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In this paper, the effects of hydrostatic stress on the magnetic properties of Mn-Zn power ferrites are discussed. Ring cores were embedded in cement and the curing process gradually exerted pressure on the core. A novel testing method was developed to continuously measure the power losses and the magnetic susceptibility in dependence on magnetic excitation at a fixed frequency and room temperature with a vector network analyzer. After 450 h, a maximum compressive stress of 120 MPa was reached. Power loss up to 300% was observed, while magnetic susceptibility dropped by 35%. The magneto-mechanical effect on core losses was simulated with the Hodgdon–Esguerra hysteresis model, showing excellent agreement with tested results, which allows us to predict the behavior of ferrite tiles embedded in load-bearing surfaces for wireless power transfer (WPT) applications. [ABSTRACT FROM AUTHOR]

Repurposing existing natural gas pipelines for hydrogen transport requires an accurate assessment of the distribution of hydrogen (H) atoms at defects, such as dents, under frequent pressure fluctuations experienced by gas pipelines. In this work, a 3-dimensional finite element-based model was developed to determine the stress/strain and H atom concentrations at an unconstrained dent on an X52 steel pipe which experienced denting, spring-back and cyclic loading processes. As expected, stress and strain concentrations generate at the dent center. However, the cyclic loading reduces the stress level and shifts the stress concentration zone from the dent center along the circumferential direction. As the dent depth increases, the maximum H atom concentration is further shifted from the dent center to the side. There are no certain relationships among the maximum H atom concentration, von Mises stress, hydrostatic stress, and plastic strain in terms of their distributions and quantities. Pressure fluctuations decrease both the stress and H atom concentrations at the dent, providing a beneficial effect on reduced risk of the dented pipelines to hydrogen embrittlement in high-pressure hydrogen gas environments. The indenter size has little influence on the H atom distribution in the dent area. [ABSTRACT FROM AUTHOR]

To study the failure (strength) regularities of rocks under complex stress states, we propose a novel three-parameter deviatoric function that includes the shape of the failure envelope on the Mohr–Coulomb (MC), Ottosen, Bigoni–Piccolroaz, and Wu–Zhang deviatoric planes. This function realizes the deviatoric plane shape of numerous classic criteria, including the Rankine, Tresca, von Mises, generalized Tresca, MC, Drucker–Prager (DP), Matsuoka–Nakai (MN), Lade–Duncan (LD), and Ottosen. On this basis, taking the nonlinear characteristics of the power function, we establish a novel 3D NUF criterion, namely MCNUF and LDNUF criteria, where the novel parameter γ is based on the basic parameters of two classical criteria, MC and LD, respectively. Based on the triaxial test data of different rocks, the proposed MCNUF and LDNUF criteria are compared with the previous criteria (the generalized nonlinear failure criterion (MNGNF), the DP and MN unified (DPMNu) criterion). Results show that: (1) the internal friction angles predicted by each criterion are equal under the same meridian plane parameters. (2) For four kinds of rock materials, the prediction performance of the proposed criteria is generally better than that of the MNGNF and DPMNu criteria. (3) The proposed criteria describe the hydrostatic stress and IPS and their coupled effect on various rock materials. (4) The 3D graphical visualization of the proposed criteria is carried out systematically, which plays a positive guiding role in enriching and perfecting the strength theory. [ABSTRACT FROM AUTHOR]

Clay formations present very favourable conditions for the long-term containment of radioactive waste due to their low hydraulic conductivity, high radionuclide retention capacity and limited fracturing in their natural state. But it is also due to the very low permeabilities of clays and claystone that drained conditions occur only at very slow temperature increases. The response is then partially drained or undrained with the consequence of thermal pressurisation induced by the thermal gradient. Furthermore, thermo-hydro-mechanical characterisations under drained and undrained conditions carried out on samples of the Callovo-Oxfordian (COx) clay formation and in situ experiments performed by Andra at the Meuse/Haute-Marne underground research laboratory (LS M/HM) have also highlighted the strongly coupled and complex thermo-hydro-mechanical processes of this material. In particular, the volume changes of the COx claystone, subjected to a temperature rise under a constant isotropic stress close to the in situ conditions of the LS M/HM laboratory in saturated and drained conditions, were highlighted. A behaviour comparable to that of over-consolidated clays depending on temperature is then experimentally observed, i.e. thermoelastic expansion followed by thermoplastic contraction: the transition temperature between these two volumetric deformation mechanisms would correspond to the maximum temperature value undergone by the COx claystone during its geological history. Based on the extensive literature on the thermomechanical behaviour of clays and clayey soils, recent thermo-hydro-mechanical tests conducted on COx samples, as well as the database on the instantaneous behaviour of COx claystone, a constitutive model for the thermomechanical behaviour of COx claystone is proposed, then implemented in a commercial computation code. The transverse isotropic elastic and then elastoplastic instantaneous behaviour (beyond the elastic limit) up to the peak strength of the COx claystone, thermoplastic and hydrostatic compactions are taken into account. The model is first validated on triaxial and hydrostatic paths. The simulation of one of the drained hydrostatic stress heating tests performed by Braun et al. verified that the proposed model was able to reproduce the thermal compaction phenomenon highlighted by the authors and to show its operational character. Highlights: As for over-consolidated clays, the volume changes of COx claystone subjected to temperature rise exhibit a thermoelastic expansion followed by thermoplastic compaction. The transition temperature between these two volumetric mechanisms would correspond to the maximum temperature undergone by the COx during its geological history. A thermo-elasto-plastic model is proposed by incorporating the observed non-linear behaviour of the COx claystone up to its strength, with the two volumetric strain mechanisms. The proposed model is implemented in the commercial geomechanical software, FLAC3D. After checking the model on triaxial stress paths, the drained hydrostatic stress heating tests performed by Braun et al. are used to validate the proposed model. [ABSTRACT FROM AUTHOR]

Certain metals experience a substantial deterioration in mechanical properties when exposed to a hydrogen environment, an effect termed hydrogen embrittlement. To understand, predict, and counteract this hydrogen‐assisted material degradation, sufficiently accurate material models are needed. According to the current hypothesis, hydrogen diffusion is driven by gradients of concentration and hydrostatic stress. To capture this, a phase‐field model is formulated as a multi‐field problem coupling deformation, crack propagation, and diffusion to analyze hydrogen‐promoted fracture. Here, the displacements, a fracture‐related phase‐field, the hydrogen lattice occupancy, and the chemical potential are considered as primary field variables. Approaches proposed in the literature often use an extrapolation of the hydrostatic stress calculated at the material point level onto the nodes and later use the B‐matrix to compute the gradient of hydrostatic stress. In order to circumvent this potentially inaccurate extrapolation, the model is recast into a mixed rate‐type variational setting, where the chemical potential—whose gradient governs the hydrogen flux—is obtained from the numerical solution of a saddle point problem. A representative boundary value problem is presented to demonstrate the applicability of the developed numerical framework. [ABSTRACT FROM AUTHOR]

Since many years ago, ultrasonic velocity has been used to investigate the physical and mechanical behaviour of rocks, thereby playing an important role in reservoir characterization and seismic interpretation. In order to develop the knowledge of ultrasonic tools, we performed a noble analysis on the ultrasonic behaviour of rocks under confining stress and evaluated a distinctive property of porous media that is measured as the area under the stress–velocity curve (here defined as S*). We further investigated its relationship with elastic and mechanical behaviours of rock. To validate the theoretical framework developed in this work, 20 core plugs from various rock units with complex microstructures were subjected to triaxial compressional tests to calculate their area under the curve. Calculations were made for crack‐closing, elastic and post‐elastic stages (e.g. pore collapse) along the ultrasonic velocity–stress curve. Moreover, the selected samples had their microstructure investigated by thin‐section studies to quantify their porosity and pore type. The results were analysed to check for the effect of pore type on S* in different stages of the stress–velocity curve. Based on the outputs of the analysis of variance and Pearson's correlation coefficient analysis, the curve had its shape and underlying area closely related to the porosity and pore geometry. Indeed, the results showed that the shale and sandstone with micro cracks and carbonate with stiff pores correspond to smaller and larger areas under the curve in crack‐closing and inelastic stages, respectively. Cross‐correlating the results to compressibility (inverse of bulk modulus), it was figured out that the calculated area under curve was well consistent with the compressibility. In addition, S* represents both static and dynamic behaviours of the rock, and the results revealed that the shape and curvature of the stress–velocity curve give valuable information about the rock microstructure. Another finding was the fact that the type of fluid and wave velocity seemingly affect the S*. Our findings can help interpret wave velocity behaviour in reservoir rocks and other stressful porous media. [ABSTRACT FROM AUTHOR]

This article discusses a method for estimating residual stresses in metal samples produced by additive manufacturing, specifically focusing on steel cylindrical bars produced by laser powder bed fusion (LPBF). The method involves making a partial longitudinal cut in the bar using electrical discharge machining (EDM) and measuring the resulting deflection to assess the contribution of residual stresses. The study combines experimental analysis with numerical simulation using finite element modeling (FEM). The proposed method allows for the estimation of residual stresses in the laboratory without the need for special equipment. The article also provides a list of references that cover various topics related to residual stresses and mechanical properties of additively manufactured stainless steel, which can be useful for further research. [Extracted from the article]

Hydride precipitation ahead of a crack is examined under conditions of hydrogen chemical equilibrium, constant temperature and elastic-plastic power-law hardening metal behavior. The limiting conditions are approached via the interaction of the operating physical mechanisms of material deformation, hydrogen diffusion and hydride precipitation. Hydrides are characterized by hydride volume fraction and isotropic transformation strain. Analytical relations are presented for hydride volume fraction and stress, as well as for hydride precipitation zone boundary. It is shown that there is an annulus, within the hydride precipitation zone, where stresses, although vary according to 1 / r 1 / n + 1 -singularity, deviate significantly from the well-known HRR-field, being smaller, according to the difference of hydrostatic stress before and after hydride precipitation. Hydride precipitation zone increases with crack-tip constraint, given by triaxiality parameter Q . [ABSTRACT FROM AUTHOR]

We apply Muskhelishvili's complex variable method to solve the plane strain problem associated with two circular incompressible liquid inclusions embedded in an infinite isotropic elastic matrix subjected to uniform remote in‐plane normal stresses. An analytical solution to the problem is derived primarily with the aid of conformal mapping and analytic continuation. To demonstrate our analytical solution, we present detailed numerical results characterizing the internal uniform hydrostatic stresses within the two liquid inclusions, the nonuniform hoop stresses along the two circular liquid‐solid interfaces on the matrix side and the nonuniform rigid body rotations within the two circular liquid inclusions. [ABSTRACT FROM AUTHOR]

In order to study the effects of notched parameters on the hydrogen embrittlement (HE) behaviors of pipeline steel in hydrogen-blended natural gas environments, the mechanical properties of notched X80 steel specimens with various depth (δ), angle (ω) and curvature radius (ρ) were studied using slow strain rate tensile (SSRT) tests combined with scanning electron microscope (SEM) and finite element analysis (FEA). The tests indicate that the presence of notches greatly reduces the fracture strain, and increases the sensitivity of the specimen to HE. The geometric shape of the notch greatly affects the HE sensitivity of the notch specimen. The sharper the geometric shape of the notch, the higher the hydrostatic stress at the notch root, and the higher the diffusion hydrogen concentration, thereby increasing the hydrogen embrittlement sensitivity of the specimen. In addition, specimen with shallow notches also exhibits high hydrogen embrittlement sensitivity due to its shorter hydrogen atom diffusion distance. • The sharper the notch geometry, the higher the hydrogen embrittlement sensitivity. • The shallower the notch, the easier hydrogen atoms accumulate at the notch root. • The hydrostatic stress distribution affects hydrogen concentration distribution. • The lower stress concentration, the lower hydrogen embrittlement sensitivity. [ABSTRACT FROM AUTHOR]

The work investigates failure criteria and mean stress correction approaches for the fatigue lifetime prediction of two hyperelastic adhesives (a polyurethane, PU, and a silicon-modified polymer, SMP). Fatigue experiments are carried under constant amplitude cyclic loading at RT and 40°C/60% r.h with butt- and the thick-adherend-shear-test-joints at three stress ratios R = −1, 0.1 and 0.5. Three mean stress correction approaches are evaluated: Goodman (static strength based), Schütz (mean stress sensitivity based) and Kujawski & Ellyin (parameter optimisation based). Fatigue failure criteria considered are: Drucker-Prager (linear-relation with the hydrostatic stress), Beltrami (quadratic relationship with the hydrostatic stress), and a multivariable nominal shear and tensile stresses criterion (data-based). The comparison is based on prediction accuracy (R-squared of master SN curves) and complexity of parameter determination. The highest values of R-squared were obtained by the Kujawski and Ellyin correction, followed by Schütz and then Goodman. However, the complexity of parameter determination follows an opposite trend with Goodman being the lightest approach. Failure criteria yielded comparable results with the multivariable criterion having the advantage of not dealing with FEA, but being limited to joints with nearly uniform stress distribution. Finally, compared to Drucker-Prager, the Beltrami criterion had a more robust parameter determination. [ABSTRACT FROM AUTHOR]

Hydride precipitation ahead of a crack is examined under conditions of hydrogen chemical equilibrium, steady-state heat conduction and linear elastic metal behavior. The limiting conditions are approached via the interaction of the operating physical mechanisms of material deformation, hydrogen diffusion and energy flow. Analytical relations are presented for the distributions of hydrogen concentration in solid solution, hydride volume fraction and stress components, as well as for the hydride precipitation zone boundary. It is shown that there is an annulus, within the hydride precipitation zone, where stresses, although vary according to 1 / r —singularity, deviate significantly from the well-known K-field, being smaller, according to the difference of hydrostatic stress before and after hydride precipitation. The hydride precipitation zone increases with crack-tip constraint, given by T-stress. In addition, temperature gradient affects hydride precipitation zone size, by controlling stress trace distribution. [ABSTRACT FROM AUTHOR]

We use Muskhelishvili's complex variable formulation to study the interaction problem associated with a circular incompressible liquid inclusion embedded in an infinite isotropic elastic matrix subjected to the action of an edge dislocation at an arbitrary position. A closed-form solution to the problem is derived largely with the aid of analytic continuation. We obtain, in explicit form, expressions for the internal uniform hydrostatic stresses, nonuniform strains and nonuniform rigid body rotation within the liquid inclusion; the hoop stress along the liquid-solid interface on the matrix side and the image force acting on the edge dislocation. We observe that (1) the internal strains and rigid body rotation within the liquid inclusion are independent of the elastic property of the matrix; (2) the internal hydrostatic stress field within the liquid inclusion is unaffected by Poisson's ratio of the matrix and is proportional to the shear modulus of the matrix; and (3) an unstable equilibrium position always exists for a climbing dislocation. [ABSTRACT FROM AUTHOR]

In this work, the effect of hydrostatic initial stress is studied with the exited semiconductor material. Electrons are exited at the free surface of the elastic semiconductor medium using the photo-thermal-elastic theory during the transport (diffusion) process. The thermal memories are due to the dual-phase-lag (DPL) relaxation times of the heat conduction equation with a novel model. In this model, the thermal conductivity is chosen as a linear dependent function of the thermal temperature impact which is variable. The effect of gravitational field is taken into account during the two-dimensional (2D) elastic deformation under the impact of an internal heat source. The Kirchhoff transformation mapping is used. The harmonic wave (normal mode) method is applied for the 2D governing equations to obtain the main physical fields analytically. Some thermal and mechanical forces are applied with other elastic-plasma conditions at the free surface of the semiconductor material to get the complete solutions. Some comparisons used a novel parameters which depend on the DPL model and the differences in the thermal conductivity parameters and they are illustrated graphically and discussed. [ABSTRACT FROM AUTHOR]

In this study, the effects of voids on the deformation behavior and the removal mechanism of amorphous alloys with continuous void structure were revealed by analyzing atomic displacement, cutting forces, and shear strain. The results indicated that shear and extrusion were the main removal mechanisms for amorphous alloys with continuous void structure. The presence of void structures led to a reduction in both the tangential and normal forces and a bigger effect on the normal force than on the tangential force. However, an increase in void diameter causes a decrease in temperature and cutting forces and a reduction formation rate of plastic deformation regions. In addition, it was founded the machining forces and friction coefficients were strongly influenced by the void size comparing with no void workpieces. As the pore size increases, there is a gradual decrease in the friction coefficient. Furthermore, a novel model considering the interaction between the tool and voids was developed to analyze the mechanism of void closure. The model indicated that a faster voids closure and a larger plastic deformation region were observed with an increase of the depth of cut. As the cutting distance increased, the voids were closed due to the machining induced hydrostatic stress. The closure of continuous voids occurred in a similar way without a critical value for the distance and size between voids. Based on the traditional cutting theory, a void processing efficiency formula was established to study the effect of void structure and cutting speeds on the processing efficiency. [ABSTRACT FROM AUTHOR]

The hydrogen solubility in ferritic and martensitic steels is affected by hydrostatic stress, pressure, and temperature. In general, compressive stresses decrease but tensile stresses increase the hydrogen solubility. This important aspect must be considered when qualifying materials for high‐pressure hydrogen applications (e.g., for pipelines or tanks) by using autoclave systems. In this work, a pressure equivalent for compensating the effect of compressive stresses on the hydrogen solubility inside of closed autoclaves is proposed to achieve solubilities that are equivalent to those in pipelines and tanks subjected to tensile stresses. Moreover, it is shown that the temperature effect becomes critical at low temperatures (e.g., under cryogenic conditions for storing liquid hydrogen). Trapping of hydrogen in the microstructure can increase the hydrogen solubility with decreasing temperature, having a solubility minimum at about room temperature. To demonstrate this effect, the generalized law of the hydrogen solubility is parameterized for different steels using measured contents of gaseous hydrogen. The constant parameter sets are verified and critically discussed with respect to the high‐pressure hydrogen experiments. [ABSTRACT FROM AUTHOR]

We first study the plane strain problem associated with an incompressible liquid inclusion having an n-fold axis of symmetry which is embedded in an infinite isotropic elastic matrix subjected to uniform remote hydrostatic stresses. A closed-form solution is derived using Muskhelishvili's complex variable formulation, a four-term conformal mapping function and the application of analytic continuation. The pair of analytic functions characterizing the elastic field in the matrix is completely determined in elementary closed-form. Explicit expressions are obtained and graphically illustrated for the internal uniform hydrostatic stresses within the liquid inclusion and the hoop stress along the liquid–solid interface on the matrix side. The closed-form solution for a linearly compressible liquid inclusion having an n-fold axis of symmetry is also obtained. [ABSTRACT FROM AUTHOR]

Hydrogen as an energy carrier is politically supported and essential for the planned energy turnaround, but requires infrastructure for transport and storage of hydrogen on a large scale, which in turn requires the development of steels resistant to hydrogen‐induced damage. Since the experimental characterization of local hydrogen concentration is nearly impossible, but microstructure level effects are significant for damage initiation, it becomes essential to further develop accompanying numerical evaluation methods. These have to be able to quantitatively describe the effect of nonmetallic inclusions on the local hydrogen concentration as the detrimental effect of nonmetallic inclusions governs the resistance against hydrogen‐induced cracking. To capture this influence, the modeling approaches available in the literature are extended and made usable for tetrahedral elements. Validation is performed using numerical studies with specimens of different stress states. Submodels are exposed to a virtual cooling and then to a hydrogen loading. Based on the resulting residual stress fields, the local hydrogen concentrations around nonmetallic inclusions with different chemical compositions and geometry are investigated and evaluated. Herein, it can be shown that especially the hydrostatic stress has a large influence on the development of the local hydrogen concentration and that the influence is particularly strong for Al2O3‐inclusions. [ABSTRACT FROM AUTHOR]

The propagation of Love-type waves due to an impulsive point source in a hydrostatic stressed transversely isotropic (HSTI) strip clamped between a poroelastic strip and an inhomogeneous semi-infinite elastic half-space is studied. Both the strips are of finite thickness, and the semi-infinite half space is considered spatial-dependent inhomogeneous medium. The Dirac-delta function has been taken into account to represent the impulsive point source force, and Fourier Transform is used to simplify the governing equations for the respective media. Green's functions technique has been adopted for solving the problem using boundary conditions of the considered problem. Thereafter, a closed-form dispersion equation has been obtained for the model. This dispersion equation infers lots of information about the considered wave into the structure. For numerical simulation purposes, we have taken six material examples of a transversely isotropic strip under the hydrostatic stress, namely Beryl, Magnesium, Cadmium, Zinc, Cobalt, and simply isotropic. The impacts of involved parameters on the phase velocity of the wave have been studied extensively and comparatively in 6 numerical examples of HSTI media. It is reported that the phase velocity of the Love-type wave is more pronounced in the presence of porosity, hydrostatic stress, linear and quadratic inhomogeneities as well as the thickness variations in both layers. Both the linear and quadratic enhance the phase velocity of the wave, while the porosity and hydrostatic stress helping to diminish the phase velocity. [ABSTRACT FROM AUTHOR]

We study the neutrality of a coated spherical inhomogeneity when the surrounding matrix is subjected to a uniform remote hydrostatic stress distribution. Both the inhomogeneity and the coating are composed of the most general spherically uniform linear anisotropic elastic materials permitting radially symmetric deformations whilst the matrix is comprised of a spherically uniform cubic material. Furthermore, when both the coating and the matrix become isotropic elastic, we obtain an exact expression for the effective bulk modulus of sphere assemblages completely replacing the original isotropic matrix. The exact expression for the effective bulk modulus of a polycrystal is simply given. The above analysis is further adapted to accomplish the neutrality of a radially inhomogeneous and spherically anisotropic spherical inhomogeneity with a radially homogeneous and spherically anisotropic coating. [ABSTRACT FROM AUTHOR]

To study the crack propagation mechanism of jointed rock mass under pre-split blasting, LS-DYNA software was used to carry out numerical simulation of rock mass blasting with vertical single joint, horizontal single joint and vertical parallel joint. The influence of in-situ stress was discussed. The results show that when there is a vertical single joint in the center of the blastholes, the cracks between holes can be penetrated. The joints have a tendency to close, and the joint is conducive to improving the degree of rock fragmentation between holes. When there is a vertical parallel joint in the center of the blastholes, the wing crack at the joint tip can be penetrated, but good fragmentation effect of rock cannot be achieved between parallel joints. When the horizontal joint is close to the blast hole, more tensile cracks will occur when the stress wave transmits to the back burst side of the joint surface. When the horizontal joint is far from the blasthole, the blocking effect of the joint is obvious. Under the action of hydrostatic in-situ stress, the initiation and propagation of radial tensile cracks and tip wing cracks are restrained. Under the action of non-hydrostatic in-situ stress, the crack growth is more restrained in the direction of the minimum principal stress, and the restraining effect increases with the increase of the maximum principal stress. [ABSTRACT FROM AUTHOR]

Cr-doped Al2O3–YAG and Al2O3–YAG–ZrO2 eutectic ceramics rods of 3 mm in diameter were solidified from the melt by a micro-pulling down (μ-PD) technique. The Cr dopant affects the microstructure, morphology, and lattice parameters of the as-grown eutectics. As a function of the dopant, the coloration, morphology, microstructure, and luminescence were investigated. Whatever the Cr-dopant concentration, mainly two phases (Al2O3–YAG) in the case of the binary system and three phases (Al2O3–YAG–ZrO2) in the case of the ternary system were observed. The Chinese script microstructure and colony boundaries are observed in ternary eutectics. Al2O3 and YAG phases show faceted morphologies, but for the ZrO2 phase, growth tends to a weakly faceted manner and forms rods or lamellae. The hydrostatic stress of binary eutectics is less than that of ternary eutectics with same Cr dopant concentration due to the distribution of ZrO2 particles in the microstructure affected by residual stresses. The spectroscopic properties of the Cr-doped binary and ternary eutectic show that Cr3+ ions exist in both Al2O3 and YAG phases in octahedral sites. [ABSTRACT FROM AUTHOR]

Background: For constitutive modeling of foams at high strain rates, it is necessary to dynamically probe their yield surface under triaxial conditions. Objective: To demonstrate dynamic triaxial characterization of foams, using a split-Hopkinson pressure bar (SHPB), in which the yield surface can be probed in various directions in the effective versus mean stress space. Methods: A conventional SHPB is augmented with a triaxial cell, using which one can dynamically apply both axial and lateral loads. The methodology is described in detail, analyzed using a one-dimensional analytical model and demonstrated using experiments. Results: We show using analysis, and experiments on polyurethane (PU) closed-cell foams that the yield surface in the effective versus hydrostatic stress space can be probed dynamically in more than one direction by varying the cross-sectional area of the specimen used. Conclusions: A methodology is presented to probe the yield surface of foams at high strain rates using the split-Hopkinson pressure bar. It was found that the uniaxial strength of PU foams increased with the loading rates. However, there was no significant enhancement of the hydrostatic strength with respect to the loading rates. [ABSTRACT FROM AUTHOR]

This article presents the results of an investigation of crack nucleation and propagation in a transparent polydimenthylsiloxane (PDMS) elastomer. The main objective of the investigation is to characterize quantitatively the evolution of crack nucleation and propagation behavior not just through the usual macroscopic load and displacement data, but with synchronized optical images at high spatial and adequate temporal resolution that will resolve the evolution of the failure processes. This is augmented with X-ray computed tomography (CT) scans to characterize the three-dimensional geometry of the cracks nucleated in the interior of the elastomer. Towards this goal, we reproduce the classical poker-chip experiment of Gent and Lindley (Proc R Soc Lond A 249(1257):195–205, 1959) in which the specimen's diameter-to-thickness ratio is varied over a broad range to cover crack nucleation, propagation, and their coalescence. These experiments are performed on transparent PDMS with different compositions, first in a specially built loading machine that is fitted with a high magnification microscopic camera that permits the measurement of the load while simultaneously providing images of the specimen configuration and subsequently in an apparatus built for in situ observations using an X-ray CT scanning system. These experiments reveal that nucleation of multiple microcracks dominates when the diameter-to-thickness aspect ratio α is sufficiently large, because the incompressibility of the material induces substantial, nearly uniform hydrostatic tension in the specimen. In contrast, specimens with smaller aspect ratio tend to nucleate fewer cracks, and are dominated by the growth of these cracks. At even smaller α , the hydrostatic stress is significantly lowered and failure is dominated by surface flaws. The three-dimensional geometry, and the spatial distribution of the nucleated cracks were evaluated using optical microscopy and X-ray CT scans. This revealed cracks of three different shapes, one of which was confined in a layer near to the upper or bottom boundary of the poker-chip, another was across the thickness, but with a tilt relative to the axis of the specimen, and the last was propagating along the radial direction. [ABSTRACT FROM AUTHOR]

To elucidate the effect of water film on the behavior of single-crystal cubic silicon carbide (SiC) under nano-indentation, molecular dynamics (MD) simulations were employed in this work. Results showed that a pop-in event occurs during nano-indentation, which is jointly controlled by the atomic amorphization and dislocation nucleation. Compared to substrate without any water film, the depth of the incipient pop-in event of the substrate decreases with the thickness of water film, where the larger the water film thickness, the lower the depth. Therefore, it is concluded that the plasticity of the material is improved with the addition of water film. Besides, the number and length of dislocations of the substrate increase with the water film, and the migration of perfect dislocations in the [110] crystal direction of packed {111} plane also become homogenized. As the water film thickness increases, dislocation activities become more prevalent; however, the recovery of deformed crystal structure gets restrained. Owing to the increase of hydrostatic stress, the sub-surface damage of the substrate is exacerbated with the water film. In addition, the surface bulge of the substrate ascends with the water film. Finally, it is observed that the inhomogeneity of the surface bulge distribution is boosted with increasing water film thickness, while the adhesion of amorphous atoms to the diamond indenter is weakened. [ABSTRACT FROM AUTHOR]

AZ91E, a magnesium alloy, shows promise in vehicle technology with its lightweight properties and potential for hybrid metal matrix composites. This study focuses on investigating compression properties using statistical analysis and finite element method simulations. However, experimental measurements reveal a density decrease compared to theoretical values, impacting weight optimization and structural integrity in vehicles. Incorporating strengthening agents like ZrO2 and fly ash enhances mechanical properties, though fracture toughness reduces due to grain refinement. Overall, this research provides valuable insights for integrating AZ91E-based composites in the automotive industry to achieve weight reduction and improved performance. As vehicles aim for lighter materials to improve fuel efficiency and reduce emissions, magnesium alloys have emerged as promising candidates for various components. AZ91E, composed mainly of magnesium (Mg), along with aluminum (Al) and zinc (Zn) as primary alloying elements, offers excellent lightweight characteristics. However, the experimental measurements in this study revealed a decrease in density compared to theoretical values, which may have implications for vehicle weight optimization and structural integrity. Decreasing deformation height reduced compressive strength for (H/D = 1 and 1.5) of AZ91E and composites, but composites showed higher compressive strength despite slightly higher density, indicating their superior performance. Analytical equations and ANSYS software provided closely matched results for axial, compressive and hydrostatic stress, while the strength coefficient and the exponent of strain hardening revealed plastic behavior of the samples. Incorporation of FA particles improved the ultimate yield and tensile strengths, as well as the tensile characteristics and hardness with underlying processes for strengthening were discussed. The investigation of AZ91E-ZrO2-fly ash hybrid metal matrix offers valuable insights into potential applications of magnesium alloys in the automotive industry. Understanding the compression attributes and mechanical behavior of these composites, its crucial for their successful integration into vehicle components, where weight reduction and improved performance are essential goals. [ABSTRACT FROM AUTHOR]

Intracrystalline diffusion is an invaluable tool for estimating timescales of geological events. Diffusion is typically modeled using gradients in chemical potential caused by variations in composition. However, chemical potential is derived for uniform pressure and temperature conditions and therefore cannot be used to model diffusion when there are gradients in stress. Internal stress variations in minerals will create gradients in strain energy which, in addition to gradients in composition, will drive diffusion. Consequently, it is necessary to have a method that incorporates stress variations into diffusion models. To address this issue, we have derived a flux expression that allows diffusion to be modeled in ionic, crystalline solids under arbitrary stress states. Our approach is consistent with standard petrological methods but instead utilizes gradients in a thermodynamic potential called "relative chemical potential." Relative chemical potential accounts for the lattice constraint in crystalline solids by quantifying changes in free energy due to the exchanges of constituents on lattice sites under arbitrary stress conditions. Consequently, gradients in relative chemical potential can be used to model diffusion when pressure is not uniform (i.e., under conditions of non-hydrostatic stress). We apply our derivation to the common quaternary garnet solid solution almandine–pyrope–grossular–spessartine. The rates and directions of divalent cation diffusion in response to stress are determined by endmember molar volumes or lattice parameters, elastic moduli, and non-ideal activity interaction parameters. Our results predict that internal stress variations of one hundred MPa or more are required to shift garnet compositions by at least a few hundredths of a mole fraction. Mineral inclusions in garnet present a potential environment to test and apply our stress-driven diffusion approach, as stress variations ranging from hundreds of MPa to GPa-level are observed or predicted around such inclusions. The ability to model stress-induced diffusion may provide new information about the magnitudes of both intracrystalline stresses and the timescales during which they occurred, imparting a better understanding of large-scale tectono-metamorphic processes. [ABSTRACT FROM AUTHOR]

Radial free harmonic wave propagation is considered for the investigation in cylindrical shells made of orthotropic human bones, transversely isotropic hexagonal crystals and simply isotropic materials under the effect of magnetic field and hydrostatic state of stress. Numerical investigations are performed for the frequency equation through 2D and 3D graphical visuals for the impact of rotation, hydrostatic stress, axial magnetic field, inner and outer radii of the cylindrical shell on the radial phase velocity of the wave. A comparative study has been developed for femoral, tibia, mandibular buccal and lingua bones, Mg, Co, Cd, Zn, beryl and ice hexagonal crystals. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on quasi-static ductile tearing of thin plates of the aluminium alloy AA6016 in three tempers. Depending on the temper, the main fracture mechanism in the plate tearing tests changes from grain boundary failure to coalescence of voids nucleated at the constituent particles. The experiments are complemented by nonlinear finite element simulations using an enriched Gurson–Tvergaard–Needleman (GTN) model to describe the material response. The onset of accelerated void growth is initiated either by incipient material softening (named the softening model) or by the occurrence of strain localization (named the localization model). It was found that strain localization takes place at a critical porosity f c , which depends on the current hydrostatic and deviatoric stress states. While the failure strain depends on the stress path, the critical porosity appears to be path independent. A third method is proposed (named the f c (T , L) model), where a critical porosity surface f c = f c T , L is used to determine when accelerated void growth starts. The surface is generated beforehand by solving for strain localization under proportional stress states defined by the stress triaxiality T and the Lode parameter L. By comparing the simulations to the experiments, it was found that the localization model performed well for a wide range of stress states. The softening model does not portray dependence on the Lode parameter and is therefore less versatile. The localization model and the f c (T , L) model gave similar predictions, but some minor differences were observed for two of the three tempers. [ABSTRACT FROM AUTHOR]

The majority of global conventional oil reservoirs have been dramatically depleted during the last few decades. To increase the oil production rate, enhanced oil recovery (EOR) techniques are commonly utilized. The ratio of the recovered oil volume to the rock volume change is defined as Biot's coefficient. During the EOR operations, Biot's coefficient continuously changes due to the fluid injection and oil production; however, so far, only porosity-dependent or constant values of Biot's coefficient have been incorporated in the EOR calculations, which is not valid since the role of external stress changes is overlooked. In this research, the Biot's coefficient of a sandstone formation was measured through the acoustic wave propagation technique. A stress-dependent equation of Biot's coefficient was achieved for application in the EOR calculations. The findings illustrated that Biot's coefficient decreases logarithmically with the hydrostatic stress. Moreover, the Biot's coefficient varied from 0.52 to 0.60 for an applied hydrostatic stress of 3.50 MPa to 21 MPa. Furthermore, it was found that there was no anisotropy of Biot's coefficient in the sandstone formations. The extracted empirical correlation can be utilized for EOR projects in which the recovered oil volume is of paramount importance economically. [ABSTRACT FROM AUTHOR]

The interaction between the exited semiconductor medium with the induced magnetic field is investigated. The medium is taken during a microtemperature process in hydrostatic initial stresses. The problem is studied when the thermal conductivity is variable that depends on the temperature (which can be taken in a linear form of temperature). The main quantities are obtained in the context of the photo-thermoelasticity theory when the medium is in a rotator case. The two dimensions (2D) deformation equations are obtained during the thermo-elastic-plasma transport processes. The governing equations can be investigated under the integral transformations of Fourier and Laplace with the impact of microelements vector. The basic analytical solutions of the physical quantities in this phenomenon are obtained under transformations in the physical domain. The thermal ramp type (heating type) is used with some othermechanical-plasma conditions which they can be applied at the free external surface. To obtain the main solutions of basic quantities in space–time domain, some inversion methods of Fourier and Laplace transformations are applied numerically. Many comparisons between several parameters are made numerically and they are shown graphically and discussed. [ABSTRACT FROM AUTHOR]

A solution for a dilatation line which occupies an arbitrary position in an elastic wedge with free surfaces and an arbitrary apex angle is found for the first time. The analytical expressions are given in the Mellin space for the stress fields of the dilatation line. It is shown that the free surfaces of the wedge strongly affect upon the stress fields. The axial and hydrostatic stress components are not equal to zero outside the dilatation line. They are strongly inhomogeneous and can change their signs, while their magnitude is comparable with that of the other non-vanishing stress components. They also demonstrate strong non-monotonic and alternating dependence on the wedge apex angle. For the wedge apex angles of 180° and 360°, the non-vanishing stress components of the dilatation line are represented in an explicit form. The results obtained can be used for solving similar problems for long elastic dilatation inclusions of arbitrary cross section embedded to wedge-shaped elastic bodies. The paper is devoted to the memory of our friend and colleague Igor Sevostianov who gave a great contribution to micromechanics of composite and porous materials. [ABSTRACT FROM AUTHOR]

A comprehensive investigation, including experimental research, finite-element analysis, and theoretical derivation, was thoroughly carried out on the steel Q370 under strong corrosion to study its fracture mechanism further. Twenty-seven steel specimens were corroded by 36% industrial hydrochloric acid for 0, 1, 2, 4, 8, 12, 24, 48, and 72 h. In particular, a three-dimensional (3D) noncontact laser scanner measured the size of pits and roughness of the steel surface. To sum up, on the condition that the corrosion time has leaped, the section loss rate mushroomed nonlinearly. An inflection point in the curve of section loss rate occurs at 12 h, and then the growth in section loss rate keeps steady. Moreover, three-dimensional roughness parameters Sa , Sq , and Sp from 3D scanning have a linear increase, and both Ssk and Sv have a nonlinear increase; notwithstanding, Sku has a nonlinear reduction. This finding means growth of surface roughness in corroded specimens. Furthermore, considering the increase in the number of pits and the cross-section reduction, the specimen shows an obvious upward trend in fracture parameters. In this study, the cavitation growth and stress-modified critical strain models were modified to establish a strong corrosion fracture model of steel Q370, including von Mises stress, hydrostatic stress, equivalent plastic strain, and corrosion time. The fracture displacement errors with the comparison of test and finite-element values are within 7%, indicating that the fracture model can precisely simulate the fracture of steel Q370 after strong corrosion. This research can present a reference for the engineering application and subsequent investigation of steel Q370 that suffered strong corrosion. [ABSTRACT FROM AUTHOR]

In this work, small-scale, low-cycle fatigue experiments on hydrogen charged nickel specimens are performed that highlight particular grain boundaries (GBs) and triple junctions as potential intergranular crack initiation sites. To understand the micromechanics and underlying physics, a dislocation density-based crystal plasticity model coupled with slip-rate based hydrogen transport model is developed. A fatigue indicator parameter (FIP) is also developed that models the crack initiation process by considering the contributions of accumulated plastic slip, GB normal stress, and local hydrogen concentration. Depending on the diffusivity, hydrogen binding energy, and misorientation, GBs are categorized as 'special' or 'random', and their role on hydrogen distribution is analysed using a model microstructure. Special GBs are ones with low diffusivity and high hydrogen binding energy whereas the random GBs have high diffusivity but low hydrogen binding energy. Complying with the experimental observations, the evolution of FIP with load cycles suggests certain triple junction configurations in the microstructure involving in the crack initiation process. For the case of uniform initial hydrogen concentration, special GBs are found to retain more hydrogen with load cycles primarily due to their low hydrogen diffusivity whereas the random GBs diffuse hydrogen out quickly to the bulk. The high hydrogen concentration and favourable stress state in the form of high hydrostatic stress spots generally found at triple junction of special/random GBs fulfil the necessary condition leading to an intergranular crack initiation. • Fatigue experiments on H charged samples performed to understand crack initiation. • Role of grain boundaries and triple junctions on intergranular cracking is analysed. • A coupled crystal plasticity and hydrogen transport model is developed. • A fatigue indicator parameter (FIP) considers HELP, HEDE, and HELP + HEDE mechanisms. • Regions of high hydrogen & hydrostatic stress are potential crack initiation sites. [ABSTRACT FROM AUTHOR]

Clinically serious congenital heart valve defects arise from improper growth and remodeling of endocardial cushions into leaflets. Genetic mutations have been extensively studied but explain less than 20% of cases. Mechanical forces generated by beating hearts drive valve development, but how these forces collectively determine valve growth and remodeling remains incompletely understood. Here, we decouple the influence of those forces on valve size and shape, and study the role of YAP pathway in determining the size and shape. The low oscillatory shear stress promotes YAP nuclear translocation in valvular endothelial cells (VEC), while the high unidirectional shear stress restricts YAP in cytoplasm. The hydrostatic compressive stress activated YAP in valvular interstitial cells (VIC), whereas the tensile stress deactivated YAP. YAP activation by small molecules promoted VIC proliferation and increased valve size. Whereas YAP inhibition enhanced the expression of cell-cell adhesions in VEC and affected valve shape. Finally, left atrial ligation was performed in chick embryonic hearts to manipulate the shear and hydrostatic stress in vivo. The restricted flow in the left ventricle induced a globular and hypoplastic left atrioventricular (AV) valves with an inhibited YAP expression. By contrast, the right AV valves with sustained YAP expression grew and elongated normally. This study establishes a simple yet elegant mechanobiological system by which transduction of local stresses regulates valve growth and remodeling. This system guides leaflets to grow into proper sizes and shapes with the ventricular development, without the need of a genetically prescribed timing mechanism. [ABSTRACT FROM AUTHOR]

Permeability and porosity are two crucial properties related to underground gas storage. This research investigates the permeability and porosity evolution of a Vosges sandstone under different stress paths. Under hydrostatic stress, the influence of irreversible deformation on permeability is more significant than on porosity. The permeability is more sensible to confining pressure than porosity. Under non-hydrostatic loading, permeability decreases continuously with deviatoric stress. At volumetric compression stage, the decrease is due to compression and closure of pores and micro-cracks. At volumetric dilatancy stage, sand production in the shear band causes the permeability decrease. Sand production mainly occurs at volumetric dilatancy stage when closing to failure. [ABSTRACT FROM AUTHOR]

This paper presents a two-surface elastoplastic model for brittle–ductile transition behaviors of porous rocks subjected to compressive stresses. Two plastic deformation mechanisms are taken into consideration: plastic shearing at low confining pressure and plastic pore collapse at high confining pressure. For loading in the brittle regime, a unified hardening/softening law is introduced into the Drucker–Prager-type yield criterion to describe the pre-peak hardening and post-peak softening behaviors. A non-associated flow rule is adopted to capture the volumetric compressibility–dilatancy phenomenon. For loading in the ductile regime, a monotonic strain hardening law as a function of hydrostatic stress is proposed and incorporated into the DiMaggio–Sandler-type yield criterion. A non-associated flow rule is used to realistically describe the plastic compaction response caused by non-hydrostatic stress. An analytical solution of stress–strain relations for shear surface is developed in the case of conventional triaxial compression. Based on the bifurcation analysis, the onset of strain localization along cap surface is predicted. Comparisons between numerical simulations and experimental data show that the proposed model is able to capture the main mechanical behaviors of the investigated porous rocks, Adamswiller sandstone and Bentheim sandstone, including strength nonlinearity, strong pressure sensitivity, strain hardening/softening, volumetric compaction/dilation, and brittle–ductile transition. [ABSTRACT FROM AUTHOR]

The atomic mobility, microstructure, and local stress in the shear bands and necking regions of notched Cu50Zr50 metallic glasses are compared, and the intricate interplay among them is examined via molecular dynamics simulations. The virtual tensile tests show that the average atomic mobility inside the mature shear band is lower than that in the necked region, which is controlled by the corresponding atomic-level structure. The short-range topological orders revealed by the Voronoi tessellation of both the necked region and the shear band are, however, quite similar to each other, while the excess free volume of the former is significantly higher than that of the latter. This high free volume content contributes to the migration of atoms or clusters and, thus, expedites the local plastic deformation. Further investigations suggest that the free volume content correlates closely with the local hydrostatic stress, while the topological microstructure is rather insensitive to the hydrostatic stress, especially when the hydrostatic stress is low. In addition, it is also found that the atomic mobility of the central atom in a cluster correlates not only with the local packing environment, such as the free volume content or the hydrostatic stress, but also with the geometry of the cluster, such as its symmetry or coordination number. The findings are helpful in developing/selecting the constitutive models for the deformation of metallic glasses. [ABSTRACT FROM AUTHOR]

During Achilles tendon healing in rodents, besides the expected tendon tissue, also cartilage-, bone- and fat-like tissue features have been observed during the first twenty weeks of healing. Several studies have hypothesized that mechanical loading may play a key role in the formation of different tissue types during healing. We recently developed a computational mechanobiological framework to predict tendon tissue production, organization and mechanical properties during tendon healing. In the current study, we aimed to explore possible mechanobiological related mechanisms underlying formation of other tissue types than tendon tissue during tendon healing. To achieve this, we further developed our recent framework to predict formation of different tissue types, based on mechanobiological models established in other fields, which have earlier not been applied to study tendon healing. We explored a wide range of biophysical stimuli, i.e., principal strain, hydrostatic stress, pore pressure, octahedral shear strain, fluid flow, angiogenesis and oxygen concentration, that may promote the formation of different tissue types. The numerical framework predicted spatiotemporal formation of tendon-, cartilage-, bone- and to a lesser degree fat-like tissue throughout the first twenty weeks of healing, similar to recent experimental reports. Specific features of experimental data were captured by different biophysical stimuli. Our modeling approach showed that mechanobiology may play a role in governing the formation of different tissue types that have been experimentally observed during tendon healing. This study provides a numerical tool that can contribute to a better understanding of tendon mechanobiology during healing. Developing these tools can ultimately lead to development of better rehabilitation regimens that stimulate tendon healing and prevent unwanted formation of cartilage-, fat- and bone-like tissues. [ABSTRACT FROM AUTHOR]

Rotary swaging is a promising technique for the fabrication of clad Cu/Al composites. Residual stresses appearing during the processing of a special arrangement of Al filaments within the Cu matrix and the influence of the bar reversal between the passes were studied by (i) neutron diffraction using a novel evaluation procedure for pseudo-strain correction and (ii) a finite element method simulation. The initial study of the stress differences in the Cu phase allowed us to infer that the stresses around the central Al filament are hydrostatic when the sample is reversed during the passes. This fact enabled the calculation of the stress-free reference and, consequently, the analysis of the hydrostatic and deviatoric components. Finally, the stresses with the von Mises relation were calculated. Hydrostatic stresses (far from the filaments) and axial deviatoric stresses are zero or compressive for both reversed and non-reversed samples. The reversal of the bar direction slightly changes the overall state within the region of high density of Al filaments, where hydrostatic stresses tend to be tensile, but it seems to be advantageous for avoiding plastification in the regions without Al wires. The finite element analysis revealed the presence of shear stresses; nevertheless, stresses calculated with the von Mises relation show similar trends in the simulation and in the neutron measurements. Microstresses are suggested as a possible reason for the large width of the neutron diffraction peak in the measurement of the radial direction. [ABSTRACT FROM AUTHOR]

Electromigration (EM) has become one of the most significant challenges considering longterm reliability in integrated circuit design. The problem is caused by the large current density in circuit interconnections. However, in most cases, we are interested in the EM stress at specific points of the interconnect, such as vias, junctions and boundaries. As a result, Model Order Reduction (MOR) techniques can provide attractive methodologies to reduce the complexity of the original systems. System-theoretic techniques like Balanced Truncation (BT) offer very reliable bounds for the approximation error, compared to moment-matching methods. In this paper, we apply a computationally efficient Low-Rank BT procedure based on the extended Krylov subspace method, that can handle large-scale models and significantly accelerate the EM stress analysis for any general interconnect or power grid structure. For the experimental evaluation, we first consider a general structure interconnect tree to demonstrate the generalizability of the proposed method and then we employ our method on the industrial IBM power grid benchmarks where the its scalability is shown. For the latter, we demonstrate that our method can achieve a speedup up to 238 × over a standard transient analysis method and a speedup up to 15 × over COMSOL, while exhibiting negligible error. • Practical numerical approach that can be applied on general multi-segment structures. • Accurate results within a predefined error bound by using Balanced Truncation. • Efficient reduction by using low-rank EKS method for solving the Lyapunov equations. • Reusable reduced models for different electromigration stress scenaria. [ABSTRACT FROM AUTHOR]

The present study provides a theoretical estimate for the thermal stress distribution and the displacement vector inside a nano-thick infinite plate due to an exponentially temporal decaying boundary heating on the front surface of the elastic plate. The surface heating is in the form of a circular ring; therefore, the axisymmetric formulation is adopted. Three different hyperbolic models of thermal transport are considered: the Maxwell-Cattaneo-Vernotte (MCV), hyperbolic Dual-Phase-Lag (HDPL) and modified hyperbolic Dual-Phase-Lag (MHDPL), which coincides with the two-step model under certain constraints. A focus is directed to the main features of the corresponding hyperbolic thermoelastic models, e.g., finite-speed thermal waves, singular surfaces (wave fronts) and wave reflection on the rear surface of the plate. Explicit expressions for the thermal and mechanical wave speeds are derived and discussed. Exact solution for the temperature in the short-time domain is derived when the thermalization time on the front surface is very long. The temperature, hydrostatic stress and displacement vector are represented in the space-time domain, with concentrating attention on the thermal reflection phenomenon on the thermally insulated rear surface. We find that the mechanical wave speeds are approximately equal for the considered models, while the thermal wave speeds are entirely different such that the modified hyperbolic dual-phase-lag thermoelasticity has the faster thermal wave speed and the Lord-Shulman thermoelasticity has the slower thermal wave speed. [ABSTRACT FROM AUTHOR]

This research was conducted to determine how the incorporation of different poroelastic equations would affect the measured rock matrix bulk modulus in the laboratory. To do this, three experimental methods were used to measure the matrix bulk modulus, K s , of seven sandstone specimens taken from the Świętokrzyskie mine in Poland. Those experimental methods were based on the different governing equations in poroelasticty theory. The matrix bulk modulus has a substantial impact on the rock strength against external stresses. Moreover, the rock bulk modulus depends directly on two components: the pore fluid bulk modulus and matrix bulk modulus. The second one is more important as it is much higher than the first one. In this study, the accuracy of those three methods in the measurement of the matrix bulk modulus was evaluated. For this purpose, an acoustic wave propagation apparatus was used to perform the required tests. For each method, an empirical correlation was extracted between the matrix bulk modulus and the applied hydrostatic stress. In all the experiments, an exponential correlation was observed between the matrix bulk modulus and the hydrostatic stress applied on the rock. Furthermore, it was found that the incorporation of the dry bulk modulus in the calculations led to an underestimation of the matrix bulk modulus. In addition, as the hydrostatic stress was raised, the matrix bulk modulus also increased. The applied methodology can be deployed to determine the matrix bulk modulus in coupled rock-fluid problems such as reservoir depletion, hydraulic fracturing, oil recovery enhancement, underground gas storage and land subsidence. [ABSTRACT FROM AUTHOR]

The FeO/Fe bond in the oxide scale is very tight, and FeO fracture is complicated under external force. In this study, the deformation behavior and mechanical properties of single-crystal FeO/Fe under nanoindentation are analyzed by the molecular dynamics (MD) simulation method. The results show that: 1. loading stage: the load increases with the increase in the loading rate; unloading stage: the load drop rate increases with the increase in the unloading rate in the early stage, and the opposite in the middle and late stage. 2. The dislocation density and the phase transition of the HCP structure decrease with the increase in the indentation rate, and the total volume of defect atoms increases with the increase in the indentation rate. 3. When the indenter is in the FeO layer, the hardness and elastic modulus increase with the increase in the indentation rate. 4. The hydrostatic stress and Von Mises stress analysis show that the average stress value increases with the increase in the indentation rate, and coexistence of compressive and tensile stress inside the model. This study provides essential help for further exploration of the deformation behavior and mechanical properties of oxide scales. [ABSTRACT FROM AUTHOR]

Gravity waves generated by mountains are multiscale and three‐dimensional. Current orographic gravity wave drag parametrisation schemes assume that the waves are two‐dimensional, varying only in the vertical and along one horizontal direction. These schemes, therefore, do not represent the process of partial critical‐level filtering, whereby a portion of the wave spectrum is saturated where the winds parallel to the wavevectors become small. This results in an unrealistic vertical distribution of the momentum flux and forcing of the waves on the mean flow. In this paper, a method of accounting for partial critical‐level filtering in an orographic gravity wave drag parametrisation using the full spectrum of realistic topography is presented. This is achieved through binning of the expression for linear hydrostatic surface stresses, computed using Fourier transforms of the subgrid orographic heights within model grid boxes, into wavevector directions. The parametrisation is compared with idealised nonlinear simulations of flow over complex topography and is shown to perform well as the number of wavevector direction bins is increased. Implementation of the scheme into the Met Office Unified Model is tested using short‐range 5‐day forecasts. As is found from idealised simulations, the binned scheme leads to less forcing in the troposphere and increased forcing in the stratosphere within the model. The binned scheme is shown to alleviate biases in the upper stratosphere, between 45 and 65 km, as well as having significant local effects in the troposphere. [ABSTRACT FROM AUTHOR]

It is investigated to what extent the evolution of ductile damage in cold forging can be controlled without changing the geometry of the produced part. Besides the effects of strain hardening and residual stresses, damage, which is the nucleation, growth and coalescence of voids on microscopic level, affects product properties of the manufactured components such as fatigue strength, impact strength, or elastic stiffness. Former investigations have shown that the load path-dependent damage evolution in forward rod extrusion, and thus, the performance of produced parts can be controlled by the process parameters extrusion strain and shoulder opening angle. As these parameters also affect the geometry of extruded parts, design requirements of components might be violated by varying these. Thus, counterpressure is used to superpose purely hydrostatic stresses to forward rod extrusion in order to decrease triaxiality in the forming zone without causing geometric variations in the produced parts. The counterpressure is either introduced by a counterpunch or by modified process routes. The achieved improvements in product performance are in agreement with results obtained by variation of extrusion strain and shoulder opening angle as described in the literature. In addition, it is observed in tensile tests that damage in cold extruded parts does not significantly affect flow stress. All advancements in product performance are realized without affecting the products' geometries. [ABSTRACT FROM AUTHOR]

It is investigated to what extent the evolution of ductile damage in cold forging can be controlled without changing the geometry of the produced part. Besides the effects of strain hardening and residual stresses, damage, which is the nucleation, growth and coalescence of voids on microscopic level, affects product properties of the manufactured components such as fatigue strength, impact strength, or elastic stiffness. Former investigations have shown that the load path-dependent damage evolution in forward rod extrusion, and thus, the performance of produced parts can be controlled by the process parameters extrusion strain and shoulder opening angle. As these parameters also affect the geometry of extruded parts, design requirements of components might be violated by varying these. Thus, counterpressure is used to superpose purely hydrostatic stresses to forward rod extrusion in order to decrease triaxiality in the forming zone without causing geometric variations in the produced parts. The counterpressure is either introduced by a counterpunch or by modified process routes. The achieved improvements in product performance are in agreement with results obtained by variation of extrusion strain and shoulder opening angle as described in the literature. In addition, it is observed in tensile tests that damage in cold extruded parts does not significantly affect flow stress. All advancements in product performance are realized without affecting the products' geometries. [ABSTRACT FROM AUTHOR]

The maximum internal pressure developed during the ignition of the explosive mixture with air within the encapsulation is directly dependent on the volume released through clearances or other discharge devices, if present. Consequently, the increase in explosion pressure must be correlated with the study of explosion-proof joints to prevent the transmission of the explosion through clearances to the ambient atmosphere. Through a comparison of defects observed during dynamic explosion tests and checks with static overpressure, a safety factor simulating the explosion demands has been identified. By checking the static overpressure at a certain pressure increase factor, the encapsulations are no less stressed than during an explosion. It has been determined that an overpressure increase factor of 1.5 times above the maximum reference explosion pressure value, during hydrostatic testing, ensures the mechanical stress of the encapsulation equivalent to the stresses resulting from overpressure through explosion. This paper presents the mechanical stress simulation of the explosion-proof encapsulation with a cylindrical frame using the SOLIDWORKS application. [ABSTRACT FROM AUTHOR]

It is investigated to what extent the evolution of ductile damage in cold forging can be controlled without changing the geometry of the produced part. Besides the effects of strain hardening and residual stresses, damage, which is the nucleation, growth and coalescence of voids on microscopic level, affects product properties of the manufactured components such as fatigue strength, impact strength, or elastic stiffness. Former investigations have shown that the load path-dependent damage evolution in forward rod extrusion, and thus, the performance of produced parts can be controlled by the process parameters extrusion strain and shoulder opening angle. As these parameters also affect the geometry of extruded parts, design requirements of components might be violated by varying these. Thus, counterpressure is used to superpose purely hydrostatic stresses to forward rod extrusion in order to decrease triaxiality in the forming zone without causing geometric variations in the produced parts. The counterpressure is either introduced by a counterpunch or by modified process routes. The achieved improvements in product performance are in agreement with results obtained by variation of extrusion strain and shoulder opening angle as described in the literature. In addition, it is observed in tensile tests that damage in cold extruded parts does not significantly affect flow stress. All advancements in product performance are realized without affecting the products' geometries. [ABSTRACT FROM AUTHOR]