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Knee and anterior cruciate ligament (ACL) are among the most injured parts of the body during sports activities. Therefore, this study aimed to evaluate knee torque and mechanical stress on ACL under various conditions of stop-jump landing, as well as identify risk factors for injury, and propose improved strategies. The stop-jump landing was modeled using anthropometric and kinematic data. Knee torque was calculated with the inverse dynamic method, and ACL stress was determined using a Finite Element Model (FEM). Different landing strategies were simulated, including variations in knee flexion at initial foot contact, as well as knee and hip angular displacement. The results showed based on mechanical stress analysis, females (6.30 MPa) had a higher probability of ACL injury compared to males (4.51 MPa). Increasing knee flexion at initial contact caused decreased knee torque and approximately a 7% reduction in ACL stress. Furthermore, increasing knee and hip angular displacement led to a decrease in knee torque, with a reduction in ACL stress by 44% and 11% respectively. To reduce the risk of ACL injury, it is recommended to increase knee flexion at initial contact as well as promote knee and hip angular displacement during landing. [ABSTRACT FROM AUTHOR]

To study the stress and deformation characteristics of Jigongzui U-shaped thin shell aqueduct structure, shell element in ANSYS is proposed to establish the three-dimensional finite element model of the aqueduct for numerical calculation, and the relevant mechanical parameters are obtained by detecting the depth of concrete carbonization. The simulated results show that: (1) The concrete carbonization depth of Jigongzui aqueduct reached 20mm, accounting for about 20% of the total thickness of the channel wall; (2) With the increase of aqueduct water level, the deformation and stress of the aqueduct body gradually increase. The maximum deflection in the middle of the span is 6.98mm, which is less than the limit value of the specification, but the tension in some areas at the bottom of the middle of the span is obvious, exceeding the allowable tensile strength. It is suggested to strengthen the aqueduct body by pasting high-performance fiber materials to improve the stress distribution of the aqueduct body; (3) Shell element has fast calculation speed and high efficiency when simulating similar U-shaped thin shell aqueduct, which can be popularized in simulating similar thin shell structures. [ABSTRACT FROM AUTHOR]

This article presents a structural strength analysis and noise reduction method for high-speed long primary moving-magnet-type linear synchronous motors (MMT-LSMs) applied to electromagnetic launch systems under high acceleration. The stresses and deformations of the mover and frame at different mover offset distances are analyzed and calculated to reveal that the permanent magnets (PMs) placed ectally on both sides of the mover core are easily damaged and need to be protected by sleeves. Then, the mover stresses with different sleeve materials and varied PM-sleeve interference values are compared for subsequent optimization. Furthermore, tooth harmonic is the main cause of vibration and noise when electromagnetic force waves are exerted on this MMT-LSM. Three improved methods are discussed comprehensively to reduce vibration and noise, including pole/slot combination, slot width, and pole arc coefficient. Finally, the experiment platform is built with the implementation of the modal and vibration acceleration experiments to verify the proposed analysis method. [ABSTRACT FROM AUTHOR]

The expanding packer is a commonly used packer, which is widely used in the process of oil and gas production. Taking the most commonly used K344 hydraulic expansion packer as the research object, using SolidWorks and ANSYS Workbench software to establish a two-dimensional finite element model of the K344 packer rubber cylinder, carry out stress analysis on the packer rubber cylinder, and obtain the packer rubber cylinder Von Mises stress and contact stress nephograms. The research results show that when the packer is in the working state of internal pressure of 20.0 MPa, the stress level of the upper and lower rubber cylinder seats is the highest, and the maximum Mises stress is 54.86 MPa; the stress level at both ends of the rubber cylinder is the highest, up to 43.465 MPa, and the strain energy density on both sides is the largest; when the packer is in the working state, the shoulder deformation is the largest, with the increase of the pressure, the deformation trend slows down, and the strain energy density has a linear relationship with the working pressure. The obtained results can provide a theoretical basis for the structural design of the expandable packer. [ABSTRACT FROM AUTHOR]

Ceramic coatings are commonly used to fulfil some form of protection function, such as thermal protection, electric isolation, or corrosion resistance. However, coating failure caused by mechanical mechanisms can reduce the effectiveness of these functions. In this study, the effect of the coating thickness of thermal barrier coatings on fracture behaviour was investigated to understand its importance and the related mechanical mechanisms. Thermal shock cycling experiments were conducted with a corresponding stress analysis based on the finite element method. The results indicate that coatings thicker than 300 μm are more likely to fail after a low number of cycles, the number of cycles at the failure of 500 μm coatings is only 16.6% of that of 100 μm coatings, and the underlying mechanism can be explained as the larger compressive stress influence of thicker coatings. The residual compressive stress increased to 125 MPa only after ten cycles for 300 μm coatings. [ABSTRACT FROM AUTHOR]

The ITER Bottom Correction Coil (BCC) is an important part of the ITER magnet system, which is used to compensate the error field of other coils caused by non-axial symmetry. The BCC lifting frame is used in the process of lifting the BCC to the temporary position in the pit, and the BCC lifting frame is also suitable for the Top Correction Coil (TCC). According to the actual working conditions, the load combination of BCC lifting frame is considered, and the tilting 6° in 4 directions is considered when the BCC lifting frame is used. The finite element analysis ensures that the BCC lifting frame can meet the stress analysis criteria. On the basis of finite element analysis, 12 lower lifting points of the lifting frame were tested with appropriate loads, and it was proved that the BCC lifting frame met the deformation evaluation criteria of load test. [ABSTRACT FROM AUTHOR]

This material summarizes the results regarding the analysis of the mechanical stress states for a piping system subjected to impeded thermal expansion. It were considered different load cases corresponding to the primary loads (own weight + internal pressure) and the secondary loads (induced by thermal expansion, including the thermal displacements of the equipment connection points). The stresses values determined for each load cases were compared with the allowable limits evaluated according to ASME B31.3 code, resulting that the analyzed piping system is safe. [ABSTRACT FROM AUTHOR]

Background: Research on resolving implant fracture is still gaining attention as it can be a serious treatment failure outcome. The implant fracture is likely to occur due to increased stress in implant body associated with peri‐implant bone resorption. Objective: This study aimed to investigate the relationship between degree of peri‐implant bone resorption and stress distribution in implant body by using finite element analysis (FEA). Methods: The magnitude and direction of loads on implants at the mandibular molar region were measured with 3D piezoelectric force transducers in a patient during maximal voluntary clenching, grinding and tapping to obtain input for the FEA as the loading condition. Simplified finite element bone models were generated to simulate the six patterns of peri‐implant bone resorption progression which the bone levels from implant platform were set at 0, 1, 2, 3, 4 and 5 mm. Three types of implants with different diameters (3.5, 4.0 and 5.0 mm), corresponding abutments and screws were created. FEA using the in vivo measured load was conducted to investigate how peri‐implant bone loss affects stress distribution in the implant body. Results: Loading condition affected stress distribution in the implant body. As bone resorption increased, von Mises stress in the implant body became larger, which was marked in smaller diameter implants, and this change was amply demonstrated when the bone resorption increased from 0 to 2 mm. Conclusion: The FEA demonstrated that as peri‐implant bone loss increased, the magnitude of stress in the implant increased, especially in small diameter implants. [ABSTRACT FROM AUTHOR]

In this study, unique short-circuit failure mechanisms in 1.2-kV SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) at 400 and 800-V dc bias were investigated using experiments and numerical TCAD simulations, taking electrical, thermal, and mechanical stress into account. It was found that the fracture of the interlayer dielectric, caused by high mechanical stress due to different thermal expansion rates, is the source of failure in the 400-V short-circuit transient. The activation of the parasitic bipolar junction transistor under extreme high temperature was confirmed to be the failure mechanism in the 800-V short-circuit transient. [ABSTRACT FROM AUTHOR]

In this study, a finite element, fully three-dimensional solid modeling method was used to study the mechanical response of a steel-cored aluminum strand (ACSR) with a mid-phase jumper under wind load. A whole model (simplifying an ACSR into a solid cylinder) and a local model (modeling according to the actual structure of an ACSR) of the mid-phase jumper were established. First, the movement of the mid-phase jumper of the tension tower under wind load was studied based on the whole finite element model, and the equivalent Young's modulus of the whole model was adjusted based on the local model. The results of the whole model were then imported into the local model and the stress distribution of each strand of the ACSR was analyzed in detail to provide guidance for the treatment measures. Therefore, the whole model and the local model complemented each other, which could reduce the number of model operations and ensure the accuracy of the results. Through the follow-up test to verify the results of the finite element simulation and the comparison of the simulation and fatigue test results, the causes of the broken strand of the ACSR were discussed. Although this modeling method was applied to the stress and deformation analysis of a mid-phase jumper in this study, it can be used to study the bending deformation of rope structures with a complex geometry and the main bending deformation. In addition, the effect of the friction coefficient on the bending of the mid-phase jumper was studied. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a study of creep deformation and stress analysis in a transversely material disk subjected to the rigid shaft by using Seth's transition theory. It has been observed that radial stress has the maximum value at the inner surface of the rotating disk made of isotropic material as compared to the hoop stress and this value of radial stress further increases with the increase in the value of angular speed. Strain rates have maximum values at the inner surface for the disk made of transversely material. [ABSTRACT FROM AUTHOR]

In order to strictly control the solid impurity particles of the pipeline and ensure the cleanliness of the pipeline of the gas supply system, a filter is installed on the pipeline before the inlet of the equipment to ensure the normal operation of the pipeline instrumentation and compressors. Since the flow of the fluid will impact the filter screen, the impact stress of the fluid on the filter screen is worth studying. However, the structure of the filter screen is complicated, so the filter screen is simplified for research. The present study adopts the dimensionless π theorem to make the density, viscosity, flow velocity, and other factors of a gas-phase fluid and solid-phase fluid dimensionless and obtains an expression for the stress acting on a filter screen as a function of the fluid parameters. Then the numerical simulation is carried out using the finite element analysis software Fluent. By changing only the velocity of the fluid and changing only the mass flow rate of the solid impurity particles, numerical simulations show that the stress acting on the filter screen has a quadratic relation with the fluid flow velocity, the stress acting on the filter screen has a linear relation with the mass flow of the solid-phase fluid, which is consistent with the law embodied in the formula derived from the π theorem. In addition, by comparing the stress acting on the filter screen traversed by different gas phase fluid media (i.e. air, CH4, and N2) under the same fluid flow conditions, it is found that effects of stress acting on the filter screen caused by different gas phase-fluids are different. All these results agree with theoretical predictions. These laws can play a guiding role in practical engineering applications in the future. Highlights Based on the dimensionless π theory, the expression about the stress of the strainer is derived. A simplified finite element model of partial filter screen is established. Using the finite element analysis software, the stress of the filter screen is obtained by changing the flow velocity of the fluid, the mass flow of the solid impurity particles and the different gas phase fluids. The filter screen can be protected from damage by controlling the flow parameters of the fluid. [ABSTRACT FROM AUTHOR]

The main fundamental mechanisms proposed for the aging of polymeric insulation to breakdown at the DC design field are reviewed. A correlation between the action of static mechanical stress affecting the whole insulation volume, and DC electric-mechanical stress providing local strain large enough to bring the polymer to plastic deformation is hypothesized. With the corollary that local plastic deformation leads to the formation of cavities, or crazes, of size large enough to trigger highly energetic phenomena and bring about insulation failure, an inter-relationship between mechanical and electrical life models can be obtained and supported by calculation and fitting to experimental results. The influence of space charge is discussed and it is argued that it would play a central role in DC ageing even if its presence is not a precondition. [ABSTRACT FROM AUTHOR]

Abstract Polymers containing chromophores often exhibit mechanoresponsive behaviour, allowing the remote detection of stress in components such as rocket motors without taking the rockets out of service. Here we describe a polymer comprising a difunctional spiropyran chromophore and methyl methacrylate cross-linked with hydroxyl-terminated polybutadiene (HTPB). This polymer was developed as a sensor for the non-destructive monitoring of mechanical stress by using the force-induced colour changes as a quantitative readout. After about 40 N of load was applied there was a gradual colour changes proportional to the compressive forces on the sample, as revealed by in-situ monitoring using a video camera and UV–Vis spectrometry. The tests highlighted a gradual decrease in the transmitted light intensity at 675 nm with increasing load, due to the opening of the spiropyran rings and their conversion to the coloured merocyanine forms. A reversible change to the initial colour occurred 72 h after the load was removed, but only under artificial fluorescent lighting, confirming that visible light is required for the ring-closing reaction. This new polymer is an ideal candidate for the remote detection of stress-induced damage in inaccessible structures or essential equipment that cannot be withdrawn from service for testing. Highlights • A polymer containing a bifunctional spiropyran chromophore was prepared to produce a force-induced colour sensor. • The compression force-induced colour changes in the polymer were monitored as a function of load. • The transmitted light intensity at 675 nm decreased with increasing load due to the opening of the spiropyran rings. • A minimum compression load of 40 N was required to initiate spiropyran ring opening, thus triggering colouration. • This polymer is ideal for the remote detection of stress-induced damage in inaccessible structures or essential equipment. [ABSTRACT FROM AUTHOR]

Optimal placement and sizing of distributed energy resources (DERs) can be performed from various points of view. In this paper, a multiobjective function is employed to determine optimal place and size of DERs including combination of photovoltaic resources and a small-scale synchronous generator (SSSG) with an internal combustion engine as its prime mover. As the objective function, not only minimization of investment costs, operation costs, and system losses are used, but also the voltage of microgrid (μG) busses and current of lines are considered as constraints. In addition, this paper shows mechanical stresses can be imposed on the SSSG caused by generator swings after short circuit fault clearing. Furthermore, it may lead to mechanical fatigue in its associated shaft and prime mover. Meanwhile, it is revealed that the mechanical stresses depend on the DERs placement and size. Thus, a novel index representing the stresses on the SSSG shaft is applied in the multiobjective goal function. This decreases SSSG loss of life in a μG with overhead lines which has high rate of short circuit faults. Optimization studies are performed in a six-bus and four-DER μG using time-based simulations. [ABSTRACT FROM AUTHOR]

The ring-core method is often used in residual stress analysis. It is applied to macro- and microscale stress analysis and has a unique advantage of releasing the residual stress across the core instead of at a single point, which makes it possible to measure an uneven residual stress field within a limited area, especially when the area is too small to be measured by other techniques. We developed a new layer-by-layer stress analysis method based on the ring-core method to retrieve the uneven in-plane stress, in which a nonuniform load that surrounds the core is approximated by discrete loading and then used to reveal the stress distribution within the core. The displacement-stress relationship is calibrated through finite element simulation. Because of the difficulty of preparing a standard specimen with an accurate high-gradient in-plane field stress in an area of several micrometers, the performance of the method was tested by a finite element simulation experiment. Good matches were achieved when comparing the calculated stress fields and the stress fields in the simulation experiments, including the biaxial, uniaxial and high-gradient cases. The method was applied to a piece of superconductor stand with a highly nonuniform stress by using a 4 µm-diameter-area ring core cut with focused ion beam. [ABSTRACT FROM AUTHOR]

This paper investigates the local control of two dimensional electron gas (2DEG) density in AlGaN/GaN heterostructures by applying external mechanical stress. The proposed 2DEG tuning mechanism relies on a local modification of the piezoelectric contribution to the total 2DEG concentration at an AlGaN/GaN heterostructure interface. Discontinuities of internally stressed passivation films are known to locally modify mechanical stress in their vicinity and may, therefore, transfer mechanical strain to neighboring device regions. If a mechanically stressed passivation laterally terminates at a gate trench on top of a GaN/AlGaN heterojunction, it will, therefore, induce mechanical strain into the semiconductor at the location of the trench sidewalls. This locally affects the piezoelectric polarization vector and, thus, changes 2DEG concentration in this region. As this effect directly modifies electronic properties underneath the gate electrode, a shift of threshold voltage will be the consequence. This phenomenon has been investigated by coupling mechanical and physical device simulation and by experimental verification of the simulation results. Finally, as one of the several possible application examples, normally-off (E-mode) and normally-on (D-mode) transistors were monolithically integrated on the same wafer by embedding the respective gate electrodes into passivation layers with different degrees of mechanical stress. DC measurements of the obtained transistors showed competitive performance levels. [ABSTRACT FROM AUTHOR]

Foundation pit is one of the most factors that threaten the safe operations of buried pipeline. In order to study the effect of foundation pit excavation on the buried pipeline, a three-dimensional model of pipeline and foundation pit was established, and the variation regulations of pipeline’s deformation under the foundation pit excavation were investigated. Effects of pipeline parameters, foundation pit parameters, soil parameters and underground continuous wall on the stress, strain and deformation of the pipeline were studied. The results show that the underground continuous wall can effectively reduce the pipeline deformation. After the foundation pit excavation, the upper surface of the pipeline’s middle section is pressed, and the lower surface is pulled, but the strain distribution of the pipeline at the edge of the pit is opposite. Horizontal and vertical displacements occurs on the pipeline, horizontal displacement moves to the inside of the pit, and vertical displacement moves to the bottom of the pit. The pipeline deformation decreases with the increasing of pipeline’s radius-thickness ratio, but it increases with the increasing of the distance between the pipeline and foundation pit. The internal pressure has a small effect on the pipeline deformation. Pipeline deformation increases with increasing of the foundation pit’s width and depth. However, the length of the foundation pit has no effect on the pipeline. The pipeline deformation increases with the soil’s Poisson’s ratio increases, and it decreases with the increasing of soil’s cohesion and elastic modulus. With the increasing of thickness and elastic modulus of the underground continuous wall, the pipeline deformation decreases. Those results can be used for pipeline laying, construction, maintenance and safety evaluation. [ABSTRACT FROM AUTHOR]

Pipeline valves are the largest, heaviest, and most important valves on an offshore platform with long delivery time. A pipeline valve is either a ball type or through conduit gate valve type with a top entry design. The top entry design provides advantages such as a lower risk of leakage, greater mechanical strength against pipeline loads, and ease of maintenance (online maintenance) compared to the side entry design. A 30 in pipeline ball valve in class 1500 and carbon steel body material was chosen for stress analysis in this paper. The valve was connected to the pipeline through pup pieces from both sides. The pup pieces were connected to the body of the valve through transition pieces. The large 30 in valve has an emergency shut down safety function and is equipped with a hydraulic actuator. The valve is designed based on the American Petroleum Institute (API) 6D Specification for Pipeline and Piping valves. The proposed formula of wall thickness calculation in this paper is based on the American Society of Mechanical Engineers (ASME) Section VIII, Division 2, Boiler and Pressure Vessel Code (BPVC) instead of the ASME B16.34 standard. The wall thickness values given in the ASME B16.34 standard of "Valves Flanged, Threaded and Welding End" are very conservative and thick, which makes pipeline valves heavier and more expensive. Noticeably, ASME B16.34 requires an even higher thickness due to assembly loads, actuation (opening and closing) loads, and shapers other than circular that are applicable for pipeline valves. These valves should withstand loads from pipeline systems such as axial, torsion, and bending moments. ASME B16.34 does not specify the body wall thickness of the pipeline valves under the pipeline loads and moments. This paper aims to create a model to prove that the 30 in Class1500 pipeline valve will withstand the loads and moments with the thickness of the valve calculated using ASME Section VIII, Division 2 methods. The criteria and the model used to prove the suitability of the valve against the loads and moments are based on ASME Section VIII, Division 2. [ABSTRACT FROM AUTHOR]

Mechanical reliability of flexible amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs) is investigated by monitoring the electrical characteristic of TFTs before and after the dynamic stretch stress up to 300k cycles. With increasing the stretch cycles degradation features in a decrease in the on-state current, an increase in the off-state current, but almost no change in the subthreshold region or the threshold voltage. An approximately linear dependence between the on-state current degradation and the stretch force is observed, from which the critical fracture strain of a-IGZO thin film is determined to be 0.42%. It is proposed that a very few number of nanoscaled mechanical-stress-induced cracks, which originate from the interface between the channel and the gate insulator, and develop into both layers, but introduce only insignificant amount of interface defects, can fully explain the observed degradation. [ABSTRACT FROM AUTHOR]

In this work, crack statistics are developed for MOCVD‐grown 12 μm thick GaN on patterned Si substrate for different sizes, trench widths and trench heights of the mesas. Optical microscope is used to obtain the percentage of cracked mesas in order to develop the crack statistics. The crack statistics show that the size and the trench height of the mesas have large effects on the percentage of cracked mesas but the trench width has no significant effect. The stress on crack‐free thick GaN mesas is investigated by micro‐Raman scattering process at room temperature by varying the size, trench height and trench width of the mesas. Both crack statistics and stress measurement show the similar behavior while varying these features of the mesas. According to Raman analysis, the critical stress for cracking of 12 μm GaN films is about 1.8 GPa. [ABSTRACT FROM AUTHOR]

China Fusion Engineering Test Reactor (CFETR) central solenoid (CS) model coil (CSMC) made with cable-in-conduit conductor superconductor had been developed in the Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, China. The highest field of CSMC is 12 T when the running current is 47.65 kA, and the largest magnetic field change rate is 1.5 T/S. CSMC mainly consists of two Nb3Sn coils and three outer NbTi coils, buffer zone, feeders and joints, and preload supports. The inner diameter of the coil is 1500 mm, and the outer diameter is 3520 mm. Stress analyzes were performed using coupled solver for simultaneous structural, thermal, and electromagnetic analysis. Based on the generalized Hooke’s law, orthotropic smeared property used for the CSMC winding pancake is calculated with one so-called “unit cell” finite-element model of the jacket and insulation. A global finite-element model was created based on the design geometry data to investigate the mechanical property of CFETR CSMC. [ABSTRACT FROM AUTHOR]

Based on the unified analytical method of stress analysis for fixed tubesheet (TS) heat exchangers (HEX), floating head and U-tube HEX presented in Part I, numerical comparisons with ASME method are performed in this paper as Part II. Numerical comparison results indicate that predictions given by the unified method agree well with finite element analysis (FEA), while ASME results are not accurate or not correct. Therefore, it is concluded that the unified method deals with thin TS of different types of HEX in equal detail with confidence to predict design stresses. [ABSTRACT FROM AUTHOR]

A stress sensitivity model for the permeability of porous media based on bidispersed fractal theory is established, considering the change of the flow path, the fractal geometry approach and the mechanics of porous media. It is noted that the two fractal parameters of the porous media construction perform differently when the stress changes. The tortuosity fractal dimension of solid cluster become bigger with an increase of stress. However, the pore fractal dimension of solid cluster and capillary bundle remains the same with an increase of stress. The definition of normalized permeability is introduced for the analyzation of the impacts of stress sensitivity on permeability. The normalized permeability is related to solid cluster tortuosity dimension, pore fractal dimension, solid cluster maximum diameter, Young's modulus and Poisson's ratio. Every parameter has clear physical meaning without the use of empirical constants. Predictions of permeability of the model is accordant with the obtained experimental data. Thus, the proposed model can precisely depict the flow of fluid in porous media under stress. [ABSTRACT FROM AUTHOR]

Based on a brief review of existing tubesheet (TS) design standards and the pertinent technical literature, a unified analytical method of stress analysis for fixed TS heat exchangers (HEXs), floating head and U-tube HEXs is proposed by removing the midplane symmetry (MPS) assumption, which assumes a geometric and loading plane of symmetry at the midway between the two TSs so that only half of the HEX or one TS needs be considered. The unified method can be successfully extended to the situations for different TS materials, unequal TS thicknesses, different TS edge conditions, different TS temperatures, pressures drop and dead weights on two TSs. The effects of pressure in TS perforations and temperature gradient in TS thickness direction are also considered by the unified method. Theoretical comparison shows that ASME method can be obtained from the special case of the simplified mechanical model of the unified method. Numerical comparison indicates that predictions given by the unified method agree well with finite element analysis (FEA), while ASME results are not accurate or not correct. [ABSTRACT FROM AUTHOR]

This paper reports the use of a non-destructive continuous magnetic Barkhausen noise technique to detect applied stress on steel surfaces. The stress profile generated in a sample of 1070 steel subjected to a three-point bending test is analyzed. The influence of different parameters such as pickup coil type, scanner speed, applied magnetic field and frequency band analyzed on the effectiveness of the technique is investigated. A moving smoothing window based on a second-order statistical moment is used to analyze the time signal. The findings show that the technique can be used to detect applied stress profiles. [ABSTRACT FROM AUTHOR]

In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. In order to investigate the response of soil and footing to steady state dynamic loading, a physical model was manufactured. The manufactured physical model could be used to simulate steady state harmonic load at different operating frequencies. Total of (84) physical models were performed. The parameters that were taken into considerations include loading frequency, size of footing and different soil conditions. The footing parameters were related to the size of the rectangular footing and depth of embedment. Two sizes of rectangular steel model footing were used (100 × 200 × 12.5 mm) and (200 × 400 × 5.0 mm). The footing was tested in all parameters at the surface and at 50 mm depth below model surface. Meanwhile the investigated parameters of the soil condition included dry and saturated sand for two relative densities 30% and 80%. The response of the soil to dynamic loading includes measuring the stresses inside the soil using piezoelectric sensors as well as measuring the excess pore water pressure by using pore water pressure transducers. It was found that the rate of increase in excess pore water pressure ratio decreased remarkably at a depth of 0.5 B–1.5 B (B is the footing width) for medium and loose dense sand, respectively. Moreover, excess pore water pressure ratio increases with increasing the eccentricity of dynamic load. The generated pore water pressure is always greater under the point of load application. Its value reduces with a certain percentages at any point away from the point of load application. In addition, the rate of variation of pore water pressure with eccentricity for loose sand is less than that for medium dense sand. The dynamic stress increments resulting from the dynamic load on the foundation reduce with depth. In addition, the dynamic stresses under the corner are slightly greater than the stresses at the center by a percentage of about 10.0%. The excess pore water pressure increases with increasing the relative density of the sand, the amplitude of dynamic loading and the operating frequency. In contrast, the rate of dissipation of the excess pore water pressure during dynamic loading is more in the case of loose sand. [ABSTRACT FROM AUTHOR]

The interference-fit technology is an effective way to enhance fatigue life of mechanical structures. However, for composites, oversized interference-fit percentage causes damages and then decreases the joint performance directly. Influence of percentages on stress and damage around Carbon Fiber Reinforced Plastics interference-fit hole is analyzed in this paper. The progressive damage theory is introduced into a three-dimensional finite-element model, which consists of the mixed failure criteria combining Hashin criteria and maximum stress criteria and the corresponding property degradation rules. A nonlinear shear stress-strain relationship is also built to solve the nonlinear material behavior. Three groups of 0.4%, 0.8%, and 1.2% interference-fit percentages are analyzed. Corresponding pin installation experiments are conducted to validate the accuracy of the model. The inserting force, stress distribution, and damage initialization around the hole are investigated and discussed in this model. [ABSTRACT FROM AUTHOR]

Bolted connections inserting gaskets such as box-shape flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure. In designing the box-shape flange connections with gaskets under internal pressure, it is important to clarify the gasket stress distribution for evaluating the sealing performance of these connections. However, no research in which the sealing performance of these connections is examined under internal pressure has been carried out. Thus, the design for box-shape connection such as thickness of flange cover, number of bolts, gasket width, and so on is not clarified. In this paper, the contact gasket stresses of these connections under internal pressure are analyzed using the finite element method (FEM), taking into account a hysteresis in the stress-displacement curve of the gasket. And then, using the contact gasket stress distributions obtained from FE analysis and the relationship between gasket stress and leak rate obtained from a gasket sealing test (JIS B2490), a method for estimating an amount of leakage is examined. Leakage tests were also conducted to measure an amount of gas leakage using an actual box-shape flange connection with a gasket. The estimated results are in reasonable agreement with the experimental results. In addition, the effect of gasket width, flange cover thickness, and flange cover material is examined on the sealing performances of box-shape flange connections under internal pressure. The effects of the above factors are discussed on the sealing performance in designing box-shape flange connections. [ABSTRACT FROM AUTHOR]

The bainitic transformation with various stress states was investigated by thermal simulation, scanning electron microscope and X-ray diffraction. The results show that as the stress increases, the promotion degree of stress on bainitic transformation increases fast firstly, then increases slowly and finally decreases. There are two critical stress values. The first one corresponds to the yield strength of parent austenite and the second one corresponds to the maximum promotion degree of stress. A simple model is proposed to describe this phenomenon. In addition, the effects of compressive stress and tensile stress on microstructure and the kinetics of bainitic transformation are similar. Moreover, even a small stress such as 30 MPa can slightly promote bainitic transformation. Finally, like bainitic transformation without stress, bainitic transformation with stress is an incomplete-reaction. [ABSTRACT FROM AUTHOR]

This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg-Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide. The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides. [ABSTRACT FROM AUTHOR]

Shop-welded, flat-bottom tanks for storage of production liquids are designed and fabricated in specific dimensions and capacities for internal pressures close to atmospheric pressure in accordance with the API 12F specification. This study addresses the failure pressure on the eleven (11) current API 12F shop-welded steel tanks as well as two proposed sizes through finite element and stress analysis of more than 350 different tank models. An elastic analysis was carried out to determine the yielding pressure of the shell-to-bottom and roof-to-shell joints. An elastic buckling analysis and a post-buckling analysis including imperfections was performed to determine the buckling modes of the equipment. The redistribution of stresses due to inelastic deformations and plastic collapse were evaluated through a plastic stress analysis considering the stress-strain hardening of the ASTM A36 mild steel material. Moreover, the design pressure increase to failure pressure or 24 oz/in² (10.3 kPa) was investigated regarding the stress levels and bottom uplift of the 13 flat-bottom tanks. The presented research provides meaningful insights and engineering calculations to evaluate the current design of the API 12F shop-welded, flat-bottom tanks as well as to establish new design internal pressures guaranteeing a safe performance of the equipment. [ABSTRACT FROM AUTHOR]

Abordarea problemelor din mediul construcţiilor este facilitată în prezent de existenţa calculatoarelor şi a programelor specializate pe diferite ramuri ale ingineriei. Programele bazate pe metoda elementului finit reprezintă instrumente puternice capabile să rezolve până şi cele mai complexe structuri inginereşti. În acest context utilizatorul este cel care dictează calitatea rezultatelor obţinute în urma analizelor numerice. Din acest motiv, un aspect esenţial pentru obţinerea unor rezultate reprezentative pentru problemele studiate îl reprezintă înţelegerea de către utilizator a bazei matematice şi a etapelor de rezolvare parcurse în cadrul programelor de calcul. Având în vedere că această bază matematică este reprezentată de legile consacrate ale mecanicii mediului continuu, articolul îşi propune să prezinte într-un mod uşor de înţeles procesul de determinare a stării de tensiuni şi deformaţii a unui corp continuu, oferind în final un exemplu de calcul. Înţelegerea acestor principii de bază este fundamentală în procesul de modelare numerică a problemelor inginereşti. [ABSTRACT FROM AUTHOR]

The Superconducting FRagment Separator (Super-FRS) is a two-stage separator to be built next to the site of GSI, Darmstadt, Germany, as part of Facility for Anti-Proton and Ion Research. Its purpose is to create and separate rare isotope beams and to enable the mass measurement also for very short lived nuclei. Overall, the Super-FRS consists of 24 dipole magnets of so-called superferric type, with superconducting coils but the field shaped by magnetic iron. The coil is trapezoidal-shaped configuration, which is wound with NbTi wires of high Cu/Sc ratio and located inside a cryostat equipped with a thermal shield and cooled with liquid helium; but the dipole will have a warm iron yoke with a wide air trim slot. This paper presents the results of the eddy current calculations in the thermal shield induced during the quench of the magnet. The mechanical behavior of the thermal shield under the Lorentz forces generated by the eddy currents will also be presented. [ABSTRACT FROM PUBLISHER]

A zero curvature method to estimate the limit load is introduced in detail, and a uniform computing process for computerization of the zero curvature method is presented. A new protection criterion against plastic collapse is proposed. A lot of examples are performed and discussed. The zero curvature load determined by the zero curvature method is a preferable definition of the limit load for perfectly plastic materials or the plastic load for strain strengthening materials. Both advantages of the ASME VIII-2 code and the EN-13445 standard are absorbed in the new protection criterion. [ABSTRACT FROM AUTHOR]

This study evaluated the pure confinement effect of steel spirals embedded in concrete with varying compressive strengths. The experimental variables in the study were the compressive strength of concrete and the yield strength and volumetric ratio of the steel spirals. To estimate the pure confinement effect of the steel spirals, all the specimens were designed to exclude concrete cover and longitudinal reinforcement. The experimental results showed that the confinement effect of spirals increased with yield strength and volumetric ratio of the spirals, but greatly decreased as the concrete compressive strength increased. Using the relationship between axial and lateral strains at peak stress of spirally confined concrete, an analytical model was developed to predict the stress-strain relationship of confined concrete. The proposed model can be successfully used to predict the structural behaviour of concrete confined by normal-, high- and ultra-high-strength steel spirals, regardless of the compressive strength of concrete. [ABSTRACT FROM AUTHOR]

At present, collapse of perforated casing of some wells in shale formation during high-pressure fluid injection of massive hydraulic fracturing has been commonly observed. In order to accurately predict the stress state of the perforated casing during shale fracturing and identify the key factor affecting the perforated casing stress, a finite-element-method (FEM) mechanical model of perforated casing in anisotropic formation was established through staged finite element method (FEM). With this model, this study analysed the mechanism underlying the effects of injection fluid temperature, internal casing pressure, and cement properties on the stress of the perforated casing. Results show that thermal loading significantly affects the stress of perforated casing. The wellbore temperature decreases by 80 °C, and the stress of perforated casing increases by 11.9 % correspondingly. The reduction in internal casing pressure and appropriate increase in cement stiffness can greatly reduce the perforated casing stress. The appropriate Young's modulus of the cement for field operations ranges from 30 GPa to 45 GPa. Variations in in-situ stress and pore pressure slightly influence the stress of perforated casing. Moreover, the stress of perforated casing decreases with increasing Young's modulus of formation. The stress of perforated casing reduces by 24 % when the anisotropy index reaches 1.2. The findings of this study can be used for the risk evaluation of the perforated casing failure during hydraulic fracturing, and also provide theoretical guidance for parameter optimization of field practices in cementing and hydraulic fracturing. [ABSTRACT FROM AUTHOR]

According to anisotropic shell theory, the pressurized structure of cylindrical shell and spherical head is analyzed, and the shear force, bending moment and stress solution at the juncture are obtained. The influence of anisotropic mechanical properties and geometric parameters on shear force, bending moment and stress distribution along the cylindrical shell is discussed, and the results are compared with the isotropic results. Additionally, Hill48 anisotropic yield criterion is also used to derive the equivalent stress intensity expression of the plane stress state, and the effect of thickness ratio and elastic modulus ratio on Hill48 equivalent stress at the juncture is discussed. Finally, finite element method is applied to verify the results of stress intensity calculation, which shows that the finite element solution and the analytical solution are in good agreement. [ABSTRACT FROM AUTHOR]

Background: The study aimed to evaluate and compare the stress distribution and 3-dimensional displacements along the craniofacial sutures in between the Rapid maxillary Expansion (RME) and Implant supported RME (I-RME). Methods: Finite element model of the skull and the implants were created using ANSYS software. The finite element model thus built composed of 537692 elements and 115694 nodes in RME model & 543078 elements and 117948 nodes with implants model. The forces were applied on the palatal surface of the posterior teeth to cause 5mm of transverse displacement on either side of the palatal halves, making it a total of 10mm. The stresses and the displacement values were obtained and interpreted. Results: Varying pattern of stress and the displacements with both positive and negative values were seen. The maximum displacement was seen in the case of plain RME model and that too at Pterygomaxillary suture and Mid-palatal suture in descending order. In the case of I-RME maximum displacement was seen at Zygomaticomaxillary suture followed by Pterygomaxillary suture. The displacements produced in all the three planes of space for the plain RME model were greater in comparison to the Implant Supported RME model. And the stresses remained high for all the sutures in case of an I-RME. Conclusions: There is a definite difference in the stress and the displacement pattern produced by RME and I-RME model and each can be used according to the need of the patient. The stresses generated in case of conventional RME were considerably less than that of the I-RME for all the sutures. [ABSTRACT FROM AUTHOR]

In this work, self-assembled Ge quantum dot (QD) formation in a dielectric matrix is explored. Of particular interest were their structural and optical properties, in order to understand the stress build-up in such a process and its impact on the material properties during processing. To this end, thin films consisting of (Ge + SiO2)/SiO2 multilayers grown by RF magnetron sputtering were deposited at room temperature. Annealing of such films at 873 K in inert N2 atmosphere produced, at the position of the Ge-rich SiO2 layers, a high lateral density (about 1012 cm−2) of Ge QDs with a good crystallinity. SiO2 spacer layers separated the adjacent Ge-rich layers, where the Ge QDs were formed with a diameter of about the size of the (Ge + SiO2) as-deposited layer thickness, and created a good vertical repeatability, confirmed by the appearance of a Bragg sheet in two-dimensional small-angle X-ray scattering patterns. The structural analysis, by wide-angle X-ray diffraction, grazing-incidence small-angle X-ray scattering and transmission electron microscopy, has shown that the described processing of the films induced large compressive stress on the formed QDs. Optical analysis by time-resolved photoluminescence (PL) revealed that the high density of crystalline Ge QDs embedded in the amorphous SiO2 matrix produced a strong luminescence in the visible part of the spectrum at 2-2.5 eV photon energy. It is shown that the decay dynamics in this energy range are very fast, and therefore the transitions that create such PL are attributed to matrix defects present in the shell surrounding the Ge QD surface (interface region with the matrix). The measured PL peak, though wide at its half-width, when analysed in consecutive short spectral segments showed the same decay dynamics, suggesting the same mechanism of relaxation. [ABSTRACT FROM AUTHOR]

The stress analysis method for fixed tubesheet (TS) heat exchangers (HEX) in pressure vessel codes such as ASME VIII-1, EN13445, and GB151 all assume a geometric and loading plane of symmetry at the midway between the two TSs so that only half of the unit or one TS is need to be considered. In this study, the midplane symmetry assumption is discarded. More common situations are considered such as unequal TS thickness, different edge conditions, pressure drop, and dead weight on two TSs. Based on the classical thin plate and shell theoretical solution, an analytical method of stress analysis for TS is presented. The proposed method is suitable for different types of HEX due to fewer assumptions employed in this study. Analysis shows that floating and U-tube HEX are the two special cases of the proposed method. Theoretical comparison shows that ASME method can be obtained from the special case of the simplified mechanical model of the proposed method. Typical geometries and loading are considered, and the proposed method is used to check the adequacy of design. Predictions are compared with the results obtained from axisymmetric finite element analysis (FEA) and current ASME method. Comparison results indicate that predictions given by this paper agree well with FEA while ASME results are not correct or not accurate. [ABSTRACT FROM AUTHOR]

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In many automotive applications, repetitive self-heating is the most critical operation condition for LDMOS transistors in smart power ICs. This is attributed to thermo-mechanical stress in the on-chip metallization, which results from the different thermal expansion coefficients of the metal and the intermetal dielectric. After many cycles, the accumulated strain in the metallization can lead to short circuits, thus limiting the lifetime. Increasing the LDMOS size can help to lower peak temperatures and therefore to reduce the stress. The downside of this is a higher cost. Hence, it has been suggested to use resilient systems that monitor the LDMOS metallization and lower the stress once a certain level of degradation is reached. Then, lifetime requirements can be fulfilled without oversizing LDMOS transistors, even though a certain performance loss has to be accepted. For such systems, suitable sensors for metal degradation are required. This work proposes a floating metal line embedded in the LDMOS metallization. The suitability of this approach has been investigated experimentally by test structures and shown to be a promising candidate. The obtained results will be explained by means of numerical thermo-mechanical simulations. [ABSTRACT FROM PUBLISHER]

Industries throughout the world today have an increased awareness of environmental, health, and safety issues. This, together with recent Nuclear Regulatory Commission changes concerning source material (e.g., thorium) has added complexity in the supply chain of thoriated tungsten commonly used in plasma spray gun spares. In the interest of a safer and more sustainable work environment, Oerlikon Metco has developed thorium-free material solutions proven to have longer service life than conventional thoriated spares. This work reports on the effect, if any, caused by tungsten compositional changes and extended service life in coating properties. Microstructure, coating efficiency parameters, hardness, particle state, in situ coating stress, and ex situ modulus are evaluated over the service life duration of the nozzle, comparing coatings with thoriated and non-thoriated nozzles and electrodes with the same spray parameters. [ABSTRACT FROM AUTHOR]

New observations on the correlation between the recoverable-to-permanent transformation of hole trapping and the generation of stress-induced leakage current (SILC) under negative-bias temperature stressing are presented. Both effects are shown to exhibit very similar temperature dependence, activation energies, and power-law time exponents. In addition, a corner temperature ( \sim 125~^\circ \textC ), which marks an increase in the activation energy from the high-to-low temperature regime, is revealed in both the trapped-hole transformation and the SILC generation, further highlighting the strongly correlated behaviors of the two effects. These findings corroborate an earlier hypothesis that both phenomena share a common degradation mechanism. [ABSTRACT FROM AUTHOR]

This article provides information about stress analysis of thin beam webs with and without lighting openings. The study described in this paper was carried out in order to investigate the influence of circular lighting openings in planar webs on critical web shear force, distribution of transverse web deformations, and also strain and stress distribution in the web plate. The main goal was to compare pre- and post-buckling behaviour of a thin web with and without lighting openings under shear load. The procedure was as follows: first of all, seven specimens – beams with a different combination of parameters (web thickness, opening size and web dimension) were calculated using available analytical methods; secondly, the same specimens were produced and tested up to load near failure; thirdly, these specimens were analysed using the Finite element method; finally, the tests results were compared with results of numerical simulations. [ABSTRACT FROM AUTHOR]

For a three-dimensional theory, a variational method of mixed type is developed to determine the stress-strain state of inhomogeneous anisotropic elastoplastic bodies under the action of neutron fluxes in the case of small strains. It is assumed that the physicomechanical characteristics of the medium depend on the radiation dose. The principle proposed is based on independent variation of the velocity fields of displacements and stresses. A modification of the variational theorem to the case of a composite material in a heterogeneous environment where different phases (inclusions) are clearly expressed is given. [ABSTRACT FROM AUTHOR]

In current article the results of hydrogeodynamic monitoring, the data of chemical analysis of mineral water and seismic regime of a region are presented. Maps of the occurred earthquakes and of the isolines of equal values of deformations were drawn. The correlation between parameters of hydrogeochemical effects and characteristics of earthquakes were determined. The correlation relationship between parametres of hydrogeochemical effect and seismic events is defined. [ABSTRACT FROM AUTHOR]