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The weathering-induced changes contribute significant alteration to mechanical and failure characteristics in the rock matrix. It is crucial to evaluate the rock fracture characteristics and mechanical response under different weathering grades because prestressing rock is extremely susceptible to the effects of weathering. Consequently, this study investigates the failure characteristics and numerous generated sandstone fractures at various weathering degrees under quasi-static loadings. Brazilian tests were conducted under different loading rates (LR= 0.001 kN/s, 0.01 kN/s, 0.1 kN/s and 1 kN/s). The findings demonstrated that sandstone tensile strength is equally susceptible to loading rate and weathering grade. The tensile strength of fresh, slightly weathered and moderately weathered sandstone increased by 20%, 54%, and 52%, respectively, with an increase in loading rate from 0.001 to 1 kN/s. The fracture angle (FA), fracture maximum deviation distance (FMDD) and fracture deviation area (FDA) of fresh and moderately weathered sandstone decrease with an increase in loading rate. FMDD of slightly weathered sandstone increases slightly as compared to FA and FDA. Additionally, the results indicate that the fracture length (FL) of slightly and moderately weathered sandstone increases as the loading rate increases, whereas the FL of fresh sandstone decreases as the loading rate increases. Overall, it can be concluded that sandstone strength is affected not only by the loading rate but also by the weathering grade. Based on the laboratory failure characteristics, the geometrical trajectory is divided into single central line fracture, double central line fracture, central-non-central line fracture and non-central line fracture. [ABSTRACT FROM AUTHOR]

It is generally recognized that the fatigue failure of the cracked engineering components is a crucial issue, especially considering the sample thickness effect. Although numerous methods have been proposed, it is still unclear about the sample thickness effect on the fatigue crack growth (FCG) rate of metallic materials. Based on the plasticity‐induce crack closure and crack tunneling effect, we established an improved FCG model with a thickness factor T by the load analysis near the crack tip. The thickness factor could clarify the sample thickness effect on the FCG rate of high‐strength steels. Numerous fatigue data demonstrates that the improved model displays a fairly good relationship between the sample thickness and FCG rate. It would provide a new strategy to the FCG rate prediction of cracked structures through small size specimen. Highlights: We propose an improved model to illustrate the effect of specimen thickness on the FCG behavior.The thickness factor T provides a fairly accurate relation between the specimen thickness and FCG rate.The model would be an effective strategy to the fatigue life prediction of cracked components. [ABSTRACT FROM AUTHOR]

Background In determining mechanical characteristics, the accuracy of the thickness of the specimens can influence the biomechanical behavior, especially in the case of human tissues, where there is an important variability. This study aims to compare the accuracy of two routine measuring instruments, i.e., the digital vernier caliper and the digital thickness gauge, when measuring the thickness of venous specimens multiple times. Methodology In this study, we used 12 tubular vena cava specimens obtained from common breed pigs aged 18-24 weeks at the time of sacrifice from a local slaughterhouse. The measurements were performed using a digital vernier caliper (Multicomp PRO MP012475) for the first four protocols and a digital thickness gauge (Mitutoyo 547-500S) for the fifth protocol. In the first protocol, three measurements were taken on the same side, and their average was recorded as the sample thickness. The second protocol involved taking measurements on two opposite sides, and the average of these measurements was recorded as the sample thickness. In the third protocol, the thickness of each side was measured at its midpoint, and the average of the four measurements was recorded as the sample thickness. In the last protocol using a digital vernier caliper, the thickness of the vernier specimens was calculated as the average of the measurements taken at each corner of the square sample. Finally, for the fifth protocol, three consecutive measurements were taken using the digital thickness gauge, and their average was recorded as the final thickness of the sample. Results In the first protocol, we observed lower values during the first measurement in comparison to the second (0.409 ± 0.063 vs. 0.536 ± 0.064, p < 0.0001) and the third (0.409 ± 0.063 vs. 0.528 ± 0.055, p = 0.0001). Moreover, with the second protocol, we observed lower values during the first two measurements in comparison to the third measurement (p = 0.0279 and p = 0.0054). Regarding protocols three and four, we recorded higher values for the second and third measurements than the first one, with higher values for the third measurement than the second one. In the fifth protocol, there were no significant statistical differences between the three consecutive measurements (p = 0.953, p = 0.742, and p = 0.897). Further, we examined the variations in sample thickness determined using each of the protocols proposed for the digital vernier caliper, as well as the values obtained with the digital thickness gauge protocol. As a result, during the first and second measurements, we observed lower thickness values for the venous wall samples using the first four protocols compared to the fifth protocol (for all p < 0.05). However, no differences were noted between the five protocols during the third measurement. Conclusions The digital thickness gauge Mitutoyo 547-500S provided superior accuracy with no difference between three successive measurements of venous wall thickness, regardless of the examiner's experience. Accurately determining the thickness of venous specimens is crucial for calculating the tissue's biomechanical properties., Competing Interests: Human subjects: All authors have confirmed that this study did not involve human participants or tissue. Animal subjects: Committee of Ethics in Scientific Research of the George Emil Palade University of Medicine, Pharmacy, Science and Technology of Targu Mures, Romania Issued protocol number 2653/15.12.2023. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Ion et al.)

Laser Beam Powder Bed Fusion (LB-PBF) is a metal additive manufacturing process with the highest technological maturity and industrial acceptance levels due to its main advantage of producing complex geometries. However, there are yet some barriers to overcome for the broader adoption of LB-PBF. One of them is the questionable part quality depending on various factors, including the specimen geometry and build orientation. Thus, this study aims to understand the effect of the build orientation and specimen thickness on the obtained microstructure and mechanical properties of AISI 316L samples in terms of tensile behavior and microhardness. As a result of this study, it is observed that the variation in microhardness of samples built in different orientations or with different thicknesses is negligible. Moreover, the thickness of the tensile test specimen only affects the ductility mainly due to the statistically higher risk of a detrimental effect of the defects in the thinner specimens, whereas the build direction is more influential on the yield and ultimate tensile strength values leading to an approximate change of 15 % and anisotropic results. Vertically standing samples exhibit the lowest strength values among all build directions. The changes in the tensile properties are attributed to the microstructural effects, including grain size, morphology, and orientation. [ABSTRACT FROM AUTHOR]

• Usable specimen thickness of Si for lattice imaging on a TEM was evaluated. • The originally developed RM was used for this evaluation. • Lattice images are successfully observed for pattern with thickness of up to 508 nm. • However, the contrast of the lattice images at a thickness of 508 nm is not distinct. • The practical thickness for analysis is less than approximately 500 nm. We evaluated the usable specimen thickness of Si for lattice imaging on a transmission electron microscopy (TEM) instrument operating at 300 kV and equipped with a complementary metal-oxide-semiconductor camera by using an original reference material (RM) and comparing the lattice images obtained from Si patterns of the RM with various thicknesses. Lattice images of the {111} planes of crystalline Si are successfully observed for patterns with thicknesses of up to 508 nm. However, the contrast of these lattice fringes at a thickness of 508 nm is not distinct, even when recorded using a longer exposure time (5.0 s) than that required to obtain lattice images of patterns with thicknesses of 316 nm or less (0.5 s). Based on these results, we conclude that the practical thickness of crystalline Si specimens for accurate structural analysis and TEM magnification calibration via lattice imaging is less than approximately 500 nm under the experimental conditions. [ABSTRACT FROM AUTHOR]

This paper studies the characteristics of junction structure of closed-cell type aluminum foam, which is generally used as a shock absorber. TDCB specimens were designed for mode III type with thickness as a variable and performed a fatigue experiment on them by thickness. As the result, the load value of all specimens peaks under 0 to 25 cycles and decreases as the cycles increase. As the specimen thickens by 10 mm, the maximum load value is 1.2 times. When the thickness increases by 20 mm, the maximum value increases by 1.5 times. This study result can be utilized by investigating the mechanical characteristics of TDCB specimens for mode III type under fatigue loading conditions systematically and efficiently.

The present study attempts to investigate the effect of moisture conditioning on the indirect tensile strength (ITS) of cold recycled mixture with bitumen emulsion. Firstly, samples were prepared using a Superpave gyratory compactor. They were hence conditioned using moisture induced sensitivity tester (MIST) device. Factorial design was carried out considering four factors each at two different levels. These factors were specimen thickness, air voids content, pressure and number of cycles. In the MIST device, samples are cyclically subjected to water pressure through the sample pores. The MIST conditioned samples were tested for indirect tensile strength. The analysis of two-level full-factorial designed experiments revealed that all four factors have a negative effect on tensile strength of cold recycled mixture with bitumen emulsion. Specimen thickness was the most significant factor affecting the tensile strength followed by air voids content. In two-factor interaction, specimen thickness-number of cycles, air voids content-pressure, and pressure-number of cycles were significant. The most significant three-factor interaction was specimen thickness-pressure-number of cycles. The results from the study suggest that in measuring tensile strength, the appropriate specimen thickness and air voids content should be selected to quantify the representative tensile strength for in-situ conditions.

Failures of shear keys in precast concrete segmental bridges (PCSBs) have been attributed to fracture of concrete along the joints with shearing off the keys. The principal goal of this study is to investigate the effect of specimen thickness and coarse aggregate size on shear strength of single‐keyed dry joints in PCSBs, which are noticed by bridges designers in deciding box geometry and requiring the concrete constituents. In this paper, shear performance of match‐casting single‐keyed dry joints is assessed in terms of cracking shear strength, ultimate shear strength, residual shear strength, and failure modes. It was found that there tended to be slightly positive correlation between specimen thickness and ultimate shear strength, while the influence of coarse aggregate size was obscure. The measured shear capacity was compared with several provisions of design formulae. [ABSTRACT FROM AUTHOR]

• Long-term aging test of CFRP laminates subjected to different solutions are made. • Effects of specimen thickness on aging test of CFRP laminates are discussed. • New analytical models of accelerated factors are proposed. • The proposed models are applied to predict long-term properties of CFRP laminates. In this paper, an experimental research was undertaken to investigate the effect of specimen thicknesses on water absorptions and flexural strengths of wet lay-up CFRP laminates subjected to distilled water or alkaline solution immersion up to 180 days. Test results showed that the water uptake and flexural strength retention of CFRP laminates were significantly affected by the adopted specimen thickness. For the same aging time, the water uptake of CFRP laminates decreased in the early stage of immersion and increased in the later stage of immersion with the increase of specimen thickness. Meanwhile, the flexural strength retention generally increased as specimen thickness increased. In addition, a new thickness-based accelerated method for hygrothermal aging test of CFRP laminates was proposed. The accelerated factors of the water uptake and flexural strength retention of CFRP laminates were theoretically deduced. The proposed analytical model of accelerated factors was verified with current test data, and then applied to predict long-term properties of CFRP laminates. Compared with the traditional temperature-based accelerated method, the new thickness-based accelerated method is much easier to apply to predict long-term properties of CFRP laminates with good accuracy. [ABSTRACT FROM AUTHOR]

Although the testing method for fracture toughness KIC has been implemented for decades, the strict specimen size requirements make it difficult to get the accurate KIC for the high‐toughness materials. In this study, different specimen sizes of high‐strength steels were adopted in fracture toughness testing. Through the observations on the fracture surfaces of the KIC specimen, it is shown that the fracture energy can be divided into 2 distinct parts: (1) the energy for flat fracture and (2) the energy for shear fracture. According to the energy criterion, the KIC values can be acquired by small‐size specimens through derivation. The results reveal that the estimated toughness value is consistent with the experimental data. The new method would be widely applied to predict the fracture toughness of metallic materials with small‐size specimens. [ABSTRACT FROM AUTHOR]

In engineering design, a difficulty has always existed in those standard laboratory tests that cannot accurately predict the behavior of large structures like pipelines due to the different constraint levels. At present, extensive work has been done to characterize the constraint effects on fracture toughness by introducing a second parameter, while the systematic research on constrained transformation is inadequate. To address this issue, the ductile fracture process of X65 SENB specimen is simulated through the finite-element method coupled with the Gurson-Tvergaard-Needelman model. The parameters crack tip opening displacement (CTOD) and crack tip opening angle (CTOA) are chosen to characterize the fracture behaviors. The effects of specimen thickness on fracture toughness based on CTOD/CTOA and constraints ahead of crack tips in SENB specimen are studied. The results indicate that the critical values of CTOD/CTOA decrease with the increase of specimen thickness, but the constraint parameters are opposite. Furthermore, it finds that there is a near linear relationship between critical values of CTOD/CTOA and the stress constraint ahead of the crack tip. Thus, a constraint-corrected fracture failure criterion based on CTOD/CTOA is proposed, which can be used for the prediction and simulation of stable tearing crack growth in specimens and structures, made of this steel with any thickness value. [ABSTRACT FROM AUTHOR]

The numerical simulation and a new theoretical approach were conducted to investigate the creep crack initiation (CCI) time and the effect of constraints induced by the specimen thickness of P92 steel. The theoretical enhanced C∗-Q∗ approach, which considered the load-independent constraint parameter Q∗, was proposed to predict the CCI time around a sharp crack tip. Moreover, finite element analysis was used to verify the load independence of parameter Q∗ as the value of C∗ varied. The larger thickness of the compact tension (CT) specimen contributed to a larger constraint parameter Q∗, and the highly constrained CT specimens with larger thicknesses observably showed lower CCI times. The variation of hydrostatic stresses, triaxiality and multiaxial strain factor considering the constraint was discussed. The suitability of the analytical approach was verified to predict CCI, and the comparison between analytical and simulated results demonstrated that the C∗-Q∗ two-parameter prediction approach under stress intensity factor and Riedel-Rice (K-RR) control (initially by K, then by transient creep stress or Riedel-Rice conditions) and Hutchinson-Rice-Rosengren and Riedel-Rice (HRR-RR) control (initially by plastic HRR control, then by RR conditions) could conservatively and effectively characterize the CCI times. The K-RR solutions were more accurate when initial stress intensity factor K<6MPam1/2, and the HRR-RR solutions were more appropriate when K>6MPam1/2. [ABSTRACT FROM AUTHOR]

Fatigue crack growth experiments are performed using A7075-T6 compact tension (CT) specimens with various thicknesses t (1–21 mm). The stress intensity factor at the crack opening level Kop is measured, and the effects of t and the stress intensity factor range ΔK on Kop are investigated. In addition, the change in Kop value due to specimen surface removal is investigated. Furthermore, we clarify that the radius of curvature of the leading edge of the fatigue crack decreases as t becomes thinner. Using the three-dimensional elastoplastic finite element method, the amount of plastic lateral contraction (depression depth d) at the crack tip after fatigue loading is calculated quantitatively. The following main experimental results are obtained: In the region where ΔK is 5 MPam1/2 or higher, the rate of fatigue crack growth da/dN at a constant ΔK value increases as t increases from 1 to 11 mm. The da/dN between t = 11 and 21 mm is the same. Meanwhile, in the region where ΔK is less than 5 MPam1/2, the effect of t on da/dN is not observed. The effects of t and ΔK on the da/dN–ΔK relationship are considered physically and quantitatively based on d.

In this study, the effect of the thickness of a silica-based ceramic core on its creep deformation, either in air or under vacuum, was studied. Specimens with different thicknesses after sintering were heated to 1550 °C and by maintaining the same temperature for 40, 70 or 100 min. Scanning electronic microscopy (SEM) was employed to observe the surface microstructures and fracture morphologies of the samples. X-ray diffraction (XRD) was used to characterize the phases that formed after creep deformation. The 3D distribution of micropores and the porosities of the specimens at different states were tested by X-ray computerized tomography (XCT). The experimental results show that the effect of the thickness of the specimen on the creep deformation was notably different under different atmospheres. The creep deformation of samples with the same thicknesses under vacuum atmosphere was clearly higher than the deformation in air. In air, the creep resistance was slightly affected by the thickness of the specimen. However, the creep deformation was significantly affected by the thickness of the specimen under vacuum. The creep resistance of the 4-mm-thick specimen is noticeably higher than that of the 0.5-mm-thick specimens. The creep rate of the 0.5-mm-thick specimen is linear with the porosity of the surface layer and higher compared to the 4-mm-thick specimen, which exhibited non-linear behaviour. Reactive micropores were formed on the surface layer of these specimens under vacuum. The volume fraction of the micropores increased with increasing creep time, which resulted in the different characterization of creep for specimens with different thicknesses under vacuum. [ABSTRACT FROM AUTHOR]

In this paper, CFRP specimens were processed with the configuration of opening mode to which various fiber laminate angles have been applied. It is possible to observe that the displacements of detachment at the adhesive interface differ from each other in both the experiment and analysis results. In case of the lamination at the angle of 30°, the detachment of adhesive interface occurred at the reaction force of 224 N with the progression of 5.24 m. In case of laminations at the angles of 45° and 60°, the detachment of bonded interface occurred with the reaction forces of 1134 N and 1100 N with the progressions of 4 mm and 4.7 mm, respectively. On the basis of these results, it was possible to discern that the differences in the detachment displacement of adhesive interface and reaction force occur according to the laminate angle in the CFRP with same material properties. Through this study result, it is thought that, unlike the existing woven type CFRP to which the laminate angle was not applied, securing of the basic fiber design data for manufacturing CFRP customized to the user's environment will be able to make contributions towards the improvement of the strength and stability of the bonded CFRP structures. [ABSTRACT FROM AUTHOR]

The phase and amplitude of the electron wavefunction that has passed through ultra-thin flakes of WSe 2 is measured from high-resolution off-axis electron holograms. Both the experimental measurements and corresponding computer simulations are used to show that, as a result of dynamical diffraction, the spatially averaged phase does not increase linearly with specimen thickness close to an [001] zone axis orientation even when the specimen has a thickness of only a few layers. It is then not possible to infer the local specimen thickness of the WSe 2 from either the phase or the amplitude alone. Instead, we show that the combined analysis of phase and amplitude from experimental measurements and simulations allows an accurate determination of the local specimen thickness. The relationship between phase and projected potential is shown to be approximately linear for extremely thin specimens that are tilted by several degrees in certain directions from the [001] zone axis. A knowledge of the specimen thickness then allows the electrostatic potential to be determined from the measured phase. By using this combined approach, we determine a value for the mean inner potential of WSe 2 of 18.9±0.8 V, which is 12% lower than the value calculated from neutral atom scattering factors. [ABSTRACT FROM AUTHOR]

In this study, the fracture property is investigated with the configuration of tapered double cantilever beam different from that of the existing double cantilever beam. Aluminum TDCB (Tapered Double Cantilever Beam) specimens of mode III-type are bonded by an adhesive. The specimens had thicknesses as a variable which were 35 mm, 45 mm, and 55 mm, respectively. In the case of the specimen with a thickness of 35 mm, the maximum reaction force was shown to be about 0.4 kN when the forced displacement had progressed by about 8 mm, while the maximum reaction force of about 0.45 kN occurred in case of the specimen with a thickness of 45 mm when the forced displacement proceeded by about 7 mm, and the maximum reaction force of about 0.54kN occurred in case of the specimen with a thickness of 55mm when the forced displacement proceeded by about 7 mm. In addition, the static fracture analysis was performed for its verification by using the finite element analysis of ANSYS program, where it was affirmed that the experimental results and the simulation analysis results were shown to be similar. Based on this observation, it is considered that the simulation analysis data could be applied to the bonded interfaces of actual porous materials. [ABSTRACT FROM AUTHOR]

Since the use of composite materials can cause breakage at the fastening part when bolts and nuts, rivets or welding are used with the existing metals, a surface adhesion method using chemical adhesives is being used as the measure against such risk. In this study, the analysis results of the stresses applied to the joining interface and deformation, deformation energy produced at this time when displacements occurred at the shear face in the structures using the joining method were calculated through the analytical method based on CAE. In the analysis model, mode 1 condition for DCB test specimen specification with incorporation of British industrial standard was applied. Thicknesses of specimens were divided into 4 cases of 25, 30, 35, 40 mm, and the stresses at the adhesive interface for each specimen were calculated to be 14.5, 7.8, 9.1, 6.8 MPa, respectively, at the point where the displacements caused the adhesive interface to drop out. As the time for such occurrence of the maximum change in stresses due to thickness can be seen to be similar to the time dropping out of the adhesive interface, it is considered that base data for safety design and breakage prediction of jointed structures can be provided. [ABSTRACT FROM AUTHOR]

• High-temperature small punch test has been carried out to obtain the strength properties of the material. • Data generated by small punch testing at room temperature can be used to high temperatures by some modification. • Finite element simulation shows the limitations of the traditional expressions in correlating the material properties. • The improved traditional expressions can accurately obtain the strength properties under different specimen thicknesses. The small punch test and uniaxial tensile test of P91 steel were conducted at 600 °C, and the reliability of finite element method with the Gurson-Tvergaard- Needleman (GTN) damage model was verified by comparing the simulation results with test findings. The effect of small-scale specimen thickness on material properties was investigated through seven different specimens of varying thickness from 0.1 mm to 0.7 mm, using the GTN damage model. Finally, the traditional empirical expression was improved to correlate the small punch test characteristic loads (F y and F m) and the material mechanical properties parameters (σ YS and σ UTS) at high temperatures. The results showed that the maximum loads of different specimens with varying thickness significantly differ from the 0.5-mm specimen thickness specified in the standard small punch test, and the results of different specimens with varying thickness can be correlated to a 0.5-mm specimen thickness with little modification. The material properties predicted by the improved equations are consistent with experimental results except for σ UTS with a 0.1-mm thickness. [ABSTRACT FROM AUTHOR]

Aluminum foam with its excellent physical and mechanical characteristics is a lightweight metallic material used with good quality in vehicle bumpers, internal shock absorbers on planes, as materials for vessel joints etc. On the contrary, when aluminum foam is used without sufficient investigation, there is the likelihood of damage or destruction of the machine or mechanical structure, and in extreme case it may cause to human casualties. This study aims to analyze the characteristics of adhesive structures with aluminum foam for the closed-type aluminum foam used primarily as shock absorbers. The fatigue analyses of the DCB test specimens at mode III with aluminum foam are verified through a fatigue experiment. As the analysis results, test specimen models with the thicknesses (t) of 35 mm, 45 mm and 55 mm showed the peak load occurrence approximately after the progress from 0 to 50 cycles. And afterwards the load gradually decreased as the cycles increased. The peak loads for each DCB test specimens were ±0.80 kN for the specimen thickness(t) of 35 mm, ±0.98 kN for the specimen thickness(t) of 45 mm and ±1.18 kN for the specimen thickness(t) of 55 mm. It is also shown that the peak load occurring on the specimen increased as specimen thickness increased. These study results are compared with the specimen thickness of 35 mm model as the basis. When the specimen thickness is increased as much as 10 mm, the peak load is increased approximately 1.25 times. When the specimen thickness is also increased as much as 20 mm, the peak load is increased 1.5 times. The analysis data and the real experiment data showed similar results each other. Therefore, it can be thought that the analysis data is applicable in real field. And it is estimated that the mechanical characteristics of the DCB test specimen at mode III during the fatigue load conditions can be systematically and efficiently analyzed. [ABSTRACT FROM AUTHOR]

This study aims to investigate the mechanical behaviors under compression on the specimens of aluminum foam jointed with various thicknesses by using adhesive after being clipped to the height of 100 mm, the width of 100 mm, and the thickness of 25 mm. For the study, a simulation analysis was conducted by using the commercial finite element analysis program of ANSYS, and the process to verifying the result of simulation analyses in comparison with actual experiments was implemented. According to the results of experiments, reaction forces were risen rapidly to the yield point and this force maintained with a constant value was generally observed up to the rupture although there was the minute vibration due to the irregular arrangement of internal bubble structure as the characteristics of porous material. The simulation results could be seen to be reliable while all specimen models were different in view of the time to reach the yield point. This study identifies the mechanical characteristics of aluminum foams jointed by adhesive per thickness under compression and the result is thought to make a great contribution to the follow-up studies about the real structure jointed with aluminum foam. [ABSTRACT FROM AUTHOR]

Recently, the tightening method on the machine structure has been used by only adhesive rather than existing bolts and nuts because of light weight problem. As for the porous material such as aluminum foam, the tightening is also possible by using adhesive in the aspect of material's characteristics. In case of the structure tightened by using only adhesive, it is necessary that the fracture toughness data as a part of adhesive joint are requested in order to use safely. Because the adhesive failure characteristic of the aluminum foam which is the porous material is different from the non-porous material, the study on the fracture toughness of the adhesive interface of aluminum is important. In this study, the static experiment was performed on the adhesive specimen with the aluminum foam of DCB on tearing mode. The thicknesses of specimens were 35 mm, 45 mm, and 55 mm, respectively. In case of 35 mm thickness specimen, the maximum reaction of about 0.57 kN occurred when the forced displacement was progressed by about 7 mm. When the forced displacement was progressed by about 8 mm, the maximum reaction of about 0.68 kN occurred in case of 55 mm thickness specimen. And the simulation analysis was carried by using the finite-element analysis program of ANSYS in order to verify the experimental results. This study showed the similar trend at the results between experiment and simulation. Through the results of this study, it can be thought that the simulation analysis data may be applied to the actual jointed part of porous material. [ABSTRACT FROM AUTHOR]

The present study focuses on theoretical and numerical analysis of the joint effect of the non-singular T xx and T zz -stresses on sizes of the plastic zone in the vicinity of the crack tip under mode I loading conditions. The three-dimensional crack tip stresses including T xx and T zz stresses are incorporated into the von Mises yield criterion to develop an expression that models the crack tip plastic zone. The plastic zone size distribution is mapped for the middle plane of CT specimens. It is shown that the plastic zone size is affected by the T zz -stress, i.e. there is strong effect of out-of-plane constraint (specimen thickness) on crack tip plastic zones. The theoretical results are compared with the results computed by finite element method. In addition, to study the effect of thickness and loading mode mixity (mode I and II) of the specimen on the singular ( K I , K II ) and the non-singular ( T xx , T zz ) terms along crack front, three-dimensional stress fields are analyzed by means of finite element analysis. The strong effect of specimen thickness and mixed mode loading conditions on the T zz -stress is observed. At the same time, there is not the effect of specimen thickness on the non-singular T xx -stress at same loading conditions. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of specimen size, stress ratio, and loading pattern on fatigue crack growth for centrally cracked low carbon steel specimens. Elastic-plastic calculations were conducted under cyclic loading based on FEM using the domain integral method. The computed fatigue lives were firstly verified against the experimental tests taken from the literature. The numerical calculations showed that thickness has no significant effect on crack growth at a given stress ratio under the constant amplitude loading pattern. While the thinner specimens revealed longer fatigue lives compared to the thicker specimens at a certain stress ratio due to the application of a single tensile overload. A remarkable reduction in fatigue lives with a clear acceleration in crack growth rates was noticed for specimens with a small ligament length-to-specimen width ratio. The retardation response due to the application of a single tensile overload depended on a particular combination of specimen size and stress ratio. The variation in the crack driving force due to the change in thickness and ligament length was investigated. The relation between the crack driving force and the local stress state ahead of the crack tip was also discussed. • Retardation response depended on a given combination of thickness and stress ratio. • Ligament length showed a remarkable influence on crack growth behavior. • Variation in Δ J due to the change in thickness and ligament length was discussed. • The local stress/strain state and Δ J could explain the crack growth mechanics. [ABSTRACT FROM AUTHOR]

Influence of primary and secondary orientations on the creep behavior of aluminized single crystal Ni-based superalloy was investigated at a high temperature with various tensile stress directions and side-surface orientations. The specimens were aluminized by pack aluminizing treatment at 1000°C for 5h under argon flow. The creep rupture tests were performed at 900°C/392MPa for thick specimens and at 900°C/300MPa for the thin specimens. The aluminizing treatment reduced the creep strength of the superalloy because of the crack initiation in hardened diffusion layers. Furthermore, it was found that the creep strength of thin aluminized specimens was affected by the crystallographic orientations, not only in the tensile direction, but also in the thickness direction. This is due to the difference in the crystallographic geometry of {111} planes, which is associated with the magnitude of 〈112〉 direction shear stress on the planes and the effective cross-section change by the crack propagation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of constraint induced by specimen size on creep crack growth was studied. [•] Even in low constraint specimen FGHAZ showed a fast creep crack growth rate. [•] Correlation of C * with creep crack grow rate depended on specimen thickness. [•] Creep crack growth rate accelerated with increasing specimen size. [•] Constraint effect should be incorporated into normal remained life prediction. [Copyright &y& Elsevier]

Abstract: Laser transformation hardening is a versatile technique for enhancing surface hardness, but it has been mostly used for hardening of thick plates in order to secure enough self-quenching effect. Recently, there have been increasing needs for heat treating steel sheets, but the understanding of heat treatability for metal sheets is limited. In this study, we have investigated the effect of specimen thickness on hardening performance in the laser heat treatment of carbon steel using the process map approach recently proposed by Ki and So (2012) [1]. Using a one-dimensional heat conduction model, we have studied how the process map evolves as the specimen thickness decreases. For validation purposes, we have systematically conducted laser heat treatment on AISI 1020 steel specimens using a 3kW diode laser and constructed surface hardness maps. The experimental results are in good agreement with the theoretical predictions. [Copyright &y& Elsevier]

Abstract: In this paper, the C (t) and C ∗ integrals, stress redistribution time t red and creep crack-tip stress distributions in the compact tension (CT) specimens with various thicknesses have been calculated by the three-dimensional (3D) finite element method, and the out-of-plane creep crack-tip constraint induced by specimen thickness is quantitatively characterized and analyzed in detail. The results show that the out-of-plane creep crack-tip constraint in the CT specimens could be characterized and analyzed by the new constraint parameter R. The 3D creep crack-tip constraint increases with increasing specimen thickness, and the 3D effect becomes more pronounced with increasing the parameter C ∗. There is a central region with higher creep constraint along the crack front, the size of the region increases with increasing specimen thickness, and decreases with increasing creep time and parameter C ∗. The factors of influencing the out-of-plane creep crack-tip constraint are analyzed. [Copyright &y& Elsevier]

Abstract: Today, the resolution in phase-contrast cryo-electron tomography is for a significant part limited by the contrast transfer function (CTF) of the microscope. The CTF is a function of defocus and thus varies spatially as a result of the tilting of the specimen and the finite specimen thickness. Models that include spatial dependencies have not been adopted in daily practice because of their high computational complexity. Here we present an algorithm which reduces the processing time for computing the ‘tilted’ CTF by more than a factor 100. Our implementation of the full 3D CTF has a processing time on the order of a Radon transform of a full tilt-series. We derive and validate an expression for the damping envelope function describing the loss of resolution due to specimen thickness. Using simulations we quantify the effects of specimen thickness on the accuracy of various forward models. We study the influence of spatially varying CTF correction and subsequent tomographic reconstruction by simulation and present a new approach for space-variant phase-flipping. We show that our CTF correction strategies are successful in increasing the resolution after tomographic reconstruction. [Copyright &y& Elsevier]

Standardization of small punch test (SPT) is being carried out, but the specimen thickness is not unified in different laboratories and specimen size effect on deformation mechanism still remains unclear. In this paper, SPT specimens with thicknesses of 100 μm–500 μm were used to investigate specimen size effect on strength properties and fracture morphology of 3Cr1MoV and Incoloy 800H. The grain sizes of two materials were 10 μm (3Cr1MoV) and 50 μm (Incoloy 800H). Yield and ultimate tensile strengths were extracted from SPT data based on a combined-scheme of finite element simulations and experiments. Fractography of specimens was studied using a scanning electron microscope. The results showed that the strength value of Incoloy 800H increased with the decrease of thickness, the size dependence of yield strengths was stronger than that of ultimate strengths, and the strength value of 3Cr1MoV was thickness independent. Fractographic investigations found that failure was caused by ductile fracture for all the specimens. A theoretical model considering geometrically necessary dislocations densities, available dislocation sources and grain sizes was proposed to explain the different mechanical responses of investigated materials to specimen thicknesses. This work clarifies the SPT specimen thickness and the grain size of studied materials should be taken into consideration before sampling. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of mechanical properties like yield and ultimate tensile strengths from shear–punch tests is important when the availability of material is limited. A shear–punch test setup was built in our laboratory and the mechanical properties for different materials; mild steel, pure Al, Zn, brass (Cu–30% Zn by wt.), Al 6061, Austenitic and Martensitic stainless steels were evaluated. A new method using 1% offset criterion in conjunction with normalized shear–punch curves was used to measure the shear yield strength. A linear correlation between the shear data and tensile data was established for yield and ultimate strengths. The variation of the yield and ultimate shear strength was studied as a function of the sample thickness and die–punch clearance for soft, medium and high strength materials. [Copyright &y& Elsevier]

To determine long-range order parameters from electron diffraction intensities, the authors have developed a CCD camera system to detect precisely electron diffraction intensities, a method for quickly and precisely measuring specimen thickness, and a computer programming to calculate long-range order parameters from the ratio of superlattice and fundamental diffraction intensities. Thickness variation over a diffraction area is taken into consideration in the calculation of electron diffraction intensities on the basis of the multi-slice method, and long-range order parameters are calculated by the successive approximation method. The absorptive form factors are also calculated from experimental data of diffraction intensities by parameter fitting, and the effect of absorption on the calculation of long-range order parameters is examined. The values of Cu3Au alloys aged at 523 and 653 K that were obtained by averaging long-range order parameters determined for several diffraction areas with the developed method are close to the reported data obtained by the X-ray diffraction method. The main causes for the deviation of long-range order parameters determined for several diffraction areas are also discussed. [Copyright &y& Elsevier]

Near threshold fatigue crack growth in ambient air and in vacuum has been studied with ultrasonic fatigue testing equipment (cycling frequency 20 kHz) and with servo-hydraulic equipment (20 Hz). Aluminium alloy 2024-T3 and 7075, heat treated to promote planar slip (7075-UA) and homogeneous slip (7075-OA), respectively, have been tested at load ratio R=-1. In vacuum, no strain rate influences were found and similar crack growth rates were observed at both frequencies. Specimen thickness does not influence the threshold stress intensity amplitude (Kmax,th) determined at 3.5×10–13 m/cycle in vacuum whereas crack growth resistance increases with decreasing specimen thickness at higher growth rates. Kmax,th determined at 10-10 m/cycle in ambient air are similar at 20 Hz and 20 kHz and are 45–55% of those measured in vacuum. In ambient air and at higher stress intensities, fatigue cracks may propagate by a factor of 5–50 faster at the lower frequency. In vacuum, 7075-UA shows better crack growth properties than 7075-OA, more pronounced at higher growth rates. In ambient air, the planar slip materials show a plateau like regime in the (Δa/ΔN vs Kmax)-curves, where growth rates are hardly affected by the stress intensity. [Copyright &y& Elsevier]

Anti-symmetric four-point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode II fracture test and study the effect of specimen thickness on Mode II fracture toughness of rock. Numerical calculations show that the occurrence of Mode II fracture in the specimens without guiding grooves (when the inner and outer loading points are moved close to the notch plane) and with guiding grooves is attributed to a favorable stress condition created for Mode II fracture, i.e. tensile stress at the notch tip is depressed to be lower than the tensile strength or to be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of Mode II fracture toughness K II C decreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness. [ABSTRACT FROM AUTHOR]

The objective of this study is to statistically investigate the effect of moisture absorption on the hot/wet compressive strength of a T800H/PMR-15 carbon/polyimide composite with a quasi-isotropic stacking sequence. Compression tests on the moisture absorbed specimens were conducted at 260'C. These tests clarified the compression fracture mode, the effect of moisture absorption on hot/wet compressive strength, statistical properties and a design allowable of hot/wet compressive strength, the effectiveness of a traveler coupon to monitor moisture absorption, and the relationship between specimen thickness and hot/wet compressive strength. Important results are as follows: (1) hot/wet compressive strength was closely related with the residual moisture content measured immediately after the test, and (2) the coefficient of variation of hot/wet compressive strength was approximately twice as large as that of room temperature/dry compressive strength. [ABSTRACT FROM PUBLISHER]

Fatigue crack growth experiments are performed using A7075-T6 compact tension (CT) specimens with various thicknesses t (1–21 mm). The stress intensity factor at the crack opening level Kop is measured, and the effects of t and the stress intensity factor range ΔK on Kop are investigated. In addition, the change in Kop value due to specimen surface removal is investigated. Furthermore, we clarify that the radius of curvature of the leading edge of the fatigue crack decreases as t becomes thinner. Using the three-dimensional elastoplastic finite element method, the amount of plastic lateral contraction (depression depth d) at the crack tip after fatigue loading is calculated quantitatively. The following main experimental results are obtained: In the region where ΔK is 5 MPam1/2 or higher, the rate of fatigue crack growth da/dN at a constant ΔK value increases as t increases from 1 to 11 mm. The da/dN between t = 11 and 21 mm is the same. Meanwhile, in the region where ΔK is less than 5 MPam1/2, the effect of t on da/dN is not observed. The effects of t and ΔK on the da/dN–ΔK relationship are considered physically and quantitatively based on d. [ABSTRACT FROM AUTHOR]

Brazilian test is a commonly used laboratory method to measure the tensile strength of brittle rock, but there are also many controversies. In this paper, influencing factors including the Poisson's ratio and the rock specimen thickness on Brazilian test results are investigated using PFC3D program based on a complex-shaped grain model which can capture all the characteristics of brittle rock in threedimensional environment. The relationship between the Poisson's ratio and the tensile strength is observed through the comparison among three different models which presenting similar macro-properties except the Poisson's ratio and the tensile strength. The study of specimen thickness effect indicates that the Brazilian test results significantly overestimate the real tensile strength of the specimens with relatively larger thickness. Through investigating the stress-strain curves and crack developing processes of the Brazilian test specimens, conclusions are made that the Brazilian tensile strength will increase with the specimen thickness due to the great loading increment. [ABSTRACT FROM AUTHOR]