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To overcome the limitation in formability at room temperature, manufacturers have developed magnesium alloys with remarkable properties by adding rare-earth elements. The rare-earth magnesium alloys behave differently from the conventional alloys, especially with respect to their coupled anisotropic and strain rate sensitive behavior. In the current work, such behavior of the rare-earth Mg alloy ZEK100 sheet at room temperature is investigated with the aid of the elastic viscoplastic self-consistent polycrystal plasticity model. Different strain rate sensitivities (SRSs) for various deformation modes are employed by the model to simulate the strain rate sensitive behaviors under different loading directions and loading rates. Good agreement between the experiments and simulations reveals the importance and necessity of using different SRSs for each deformation mode in hexagonal close-packed metals. Furthermore, the relative activities of each deformation mode and the texture evolution during different loadings are discussed. The anisotropic and strain rate sensitive behavior is ascribed to the various operating deformation modes with different SRSs during loading along different directions.

The relationship between activities of involved deformation mechanisms and the evolution of microstructure and texture during uniaxial tension of AZ31 magnesium alloy with a rare non-basal texture has been thoroughly investigated in the present study by means of electron backscattered diffraction (EBSD) measurement and visco-plastic self-consistent (VPSC) modeling. These results show that except basal slip and prismatic slip, { 10 1 ¯ 2 } extension twin (ET) also plays a significant role during plastic deformation. With the increasing tilted angle between loading direction and rolling direction (RD) of sheet, the activity of { 10 1 ¯ 2 } ET possesses a decreasing tendency and its role in plastic deformation changes from the one mainly sustaining plastic strain to the one mainly accommodating local strain between individual grains. When { 10 1 ¯ 2 } ET serves as a carrier of plastic strain, it mainly results in the formation of basal texture component (c-axis//ND, normal direction). By comparison, when the role of { 10 1 ¯ 2 } ET is to accommodate local strain, it mainly brings about the formation of prismatic texture component (c-axis//TD, transverse direction). At large plastic deformation, the competition between basal slip and pyramidal slip is responsible for the concentration of tilted basal poles towards ND within all deformed samples. The larger difference is between the activities of basal slip and pyramidal slip, the smaller separation is between these two tilted basal poles. Besides, VPSC modeling overestimates volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 0 to 30° between loading direction and RD of sheet because interactions between twin variants are not included in VPSC modeling procedure at the present form. In addition, as compatible deformation between individual grains cannot be considered in VPSC modeling, the predicted volume fractions of { 10 1 ¯ 2 } ET in samples with angle of 45 to 90° between loading direction and RD of sheet are smaller than the correspondingly measured results.

This paper investigates the rate of transformation induced plasticity in TRIP steel (TRansformation-Induced Plasticity) after plastic straining by the use of Barkhausen noise emission. The samples were subjected to a variable degree of plastic straining and analysed by the use of conventional techniques such SEM, XRD, as well as microhardness in order to investigate residual stress and microstructural alterations initiated by the uniaxial tensile test. Barkhausen noise emission is analysed as a function of plastic straining as well as in the direction of the exerted load and interpreted with respect to the aforementioned microstructure and stress alterations. It was found that Barkhausen noise markedly decreases along with increasing plastic straining, up to 20%, followed by a strain region in which the evolution of Barkhausen noise reaches saturation. Samples after the tensile test exhibited marked magnetic anisotropy since the Barkhausen noise emission in the direction perpendicular to the tensile stress remained less affected. Apart from the effective value of Barkhausen noise, the Barkhausen noise envelopes were also analysed.

The texture profile analysis test is an imitative test to determine texture properties of food, which quantify the consumer’s perception of eating food. The instrumental texture parameters obtained from this test depend on the specimen size and the nonstandardized test conditions. To overcome this problem, texture properties are here related to intrinsic mechanical properties, which are independent of the test conditions. Two types of materials are used to investigate the effect of viscoelasticity, plasticity and damage on the texture parameters for varying test conditions. Analytical relations between mechanical properties, test conditions, and the instrumental hardness, springiness, cohesiveness, and adhesiveness are determined. The hardness is obtained from the stiffness of the material, which is potentially rate-dependent, and the yield stress of a material in case of plasticity. The springiness is determined by the recoverable or irrecoverable strain in the material, which results from the mechanical properties in combination with the test conditions. Cohesiveness and springiness are found to be strongly related, unless structural damage is present in the material. Adhesiveness is only an indirect measure of the adhesion between the material and compression plate and depends on the test conditions and stiffness of the material. Finite element simulations reveal a decrease of hardness in case of a nonflat top surface, indicating the importance of geometrical effects.

Structural integrity is always an important issue for the service life time of any structure. Therefore, joint of the metal is also a vital point to consider. This thesis describes a new method that uses the Fiber Bragg Grating (FBG) sensor to detect the crack initiation of friction stir welded aluminum (AL) alloy by low cycle fatigue test. Experimental setups and procedures are studied, a proper test configuration is determined and a series of testing performed. The applicability of this new method of stress control fatigue test in monitoring the metal crack initiation is demonstrated through the test results, which shows that FBG sensors are sensitive to capture the onset of the crack. Stress controlled fatigue tests especially at high strain amplitude for Friction Stir Welded (FSW) joints demand the sensors to withstand strain level above ±8000 με [40] and with the size of few mm, and these sensors are not available in the market. In this work, the new sensors arrays are used in the characterization of cyclic deformation behavior of FSW aluminum alloy, which, in some cases, could sustain up to ±11000με. During the experiment significant difference in plastic strain amplitude (PSA) was observed using these optical fiber sensors mounted in nugget zone (NZ) and across the boundary area between thermo mechanical affected zone (TMZ) and heat affected zone (HZ). For all the samples of Al alloy, with the progress of cyclic deformation the cyclic hardening characteristics of the metal were observed.

The locally occurring mechanisms of hydrogen embrittlement significantly influence the fatigue behavior of a material, which was shown in previous research on two different AISI 300-series austenitic stainless steels with different austenite stabilities. In this preliminary work, an enhanced fatigue crack growth as well as changes in crack initiation sites and morphology caused by hydrogen were observed. To further analyze the results obtained in this previous research, in the present work the local cyclic deformation behavior of the material volume was analyzed by using cyclic indentation testing. Moreover, these results were correlated to the local dislocation structures obtained with transmission electron microscopy (TEM) in the vicinity of fatigue cracks. The cyclic indentation tests show a decreased cyclic hardening potential as well as an increased dislocation mobility for the conditions precharged with hydrogen, which correlates to the TEM analysis, revealing courser dislocation cells in the vicinity of the fatigue crack tip. Consequently, the presented results indicate that the hydrogen enhanced localized plasticity (HELP) mechanism leads to accelerated crack growth and change in crack morphology for the materials investigated. In summary, the cyclic indentation tests show a high potential for an analysis of the effects of hydrogen on the local cyclic deformation behavior., Forschungsvereinigung Verbrennungskraftmaschinen, Deutsche Forschungsgemeinschaft

In this study, single-phase NbTiZr and NbTiZr(MoTa)0.1 medium-entropy alloys (MEAs) were investigated for their use in biomedical implants. The alloys were prepared by arc melting, and were then cold-rolled, annealed, and characterized in terms of phase analysis, mechanical properties, fractography, and wear resistance. Both alloys showed a single body-centered cubic phase with superior mechanical, and tribological properties compared to commercially available biomedical alloys. Mo and Ta-containing MEAs showed higher tensile yield strength (1060 ± 18 MPa)) and higher tensile ductility (∼20%), thus overcoming the strength–ductility trade-off with no signs of transformation-induced plasticity, twinning, or precipitation. The generalized stacking fault energy (GSFE) calculations on the {112} slip system by the first-principles calculations based on density functional theory showed that the addition of less than 0.2 molar fraction of Mo and Ta lowers the GSFE curves. This behavior posits the increase in ductility of the alloy by facilitating slips although strength is also increased by solid solution strengthening. The wear resistance of both alloys against hardened steel surfaces was superior to that of commercial biomedical alloys. Thus, we concluded that NbTiZr(MoTa)0.1 MEA with good tensile ductility is a potential candidate for biomedical implants.

This experimental study describes the elastic and yielding response of compacted high-plasticity clay in conjunction with deformation characteristics at relatively larger strains for different stress paths and stress states. K0 consolidated undrained triaxial compression and extension stress path tests were conducted on compacted Nagpur cohesive soil with bender element measurements to explore the elastic and yielding response of soil. The experimental results showed that the stress path direction had a significant impact on the stress–strain–strength properties of soil as the peak deviatoric stress was found to increase with the increase in stress path angle. The measured small-strain shear modulus (Gmax) values were observed to be a function of the mean effective stress (p′) with slight dependency on deviatoric stress (q). Gmax was found to reduce with increase in strain level during shearing. An attempt was made to formulate an empirical correlation for compacted cohesive soil based on the elastic shear stiffness in pre-yield conditions. This correlation was further used to determine the yielding criteria of compacted cohesive soil along with the other two well-established criteria of stress–strain and strain energy.

High- and medium-entropy alloys (HEAs and MEAs) possess high solid-solution strength. Numerous investigations have been conducted on its impact on yield strength, however, there are limited reports regarding the relation between solid-solution strengthening and strain-hardening rate. In addition, no attempt has been made to account for the dislocation-mediated plasticity; most works focused on twinning- or transformation-induced plasticity (TWIP or TRIP). In this work we reveal the role of solid-solution strengthening on the strain-hardening rate via systematically investigating evolutions of deformation structures by controlling the Cr/V ratio in prototypical V1-xCrxCoNi alloys. Comparing the TWIP of CrCoNi with the dislocation slip of V0.4Cr0.6CoNi, the hardening rate of CrCoNi was superior to slip-band refinements of V0.4Cr0.6CoNi due to the dynamic Hall-Petch effect. However, as V content increased further to V0.7Cr0.3CoNi and VCoNi, their rate of slip-band refinement in V0.7Cr0.3CoNi and VCoNi with high solid-solution strength surpassed that of CrCoNi. Although it is generally accepted in conventional alloys that deformation twinning results in a higher strain-hardening rate than dislocation-mediated plasticity, we observed that the latter can be predominant in the former under an activated huge solid-solution strengthening effect. The high solid-solution strength lowered the cross-slip activation and consequently retarded the dislocation rearrangement rate, i.e., the dynamic recovery. This delay in the hardening rate decrease, therefore, increased the strain-hardening rate, results in an overall higher strain-hardening rate of V-rich alloys.

The mechanical properties and deformation mechanism of a C-doped interstitial high-entropy alloy (iHEA) with a nominal composition of Fe49.5Mn29.7Co9.9Cr9.9C1 (at. %) were investigated. An excellent combination of strength and ductility was obtained by cold rolling and annealing. The structure of the alloy is consisted of FCC matrix and randomly distributed Cr23C6. For gaining a better understanding of deformation mechanism, EBSD and TEM were conducted to characterize the microstructure of tensile specimens interrupted at different strains. At low strain (2%), deformation is dominated by dislocations and their partial slip. With the strain increase to 20%, deformation-driven athermal phase transformation and dislocations slip are the main deformation mechanism. While at high strain of 35% before necking, deformation twins have been observed besides the HCP phase. The simultaneous effect of phase transformation (TRIP effect) and mechanical twins (TWIP effect) delay the shrinkage, and improve the tensile strength and plasticity. What's more, compared with the HEA without C addition, the yield strength of the C-doped iHEA has been improved, which can be attributed to the grain refinement strengthening and precipitation hardening. Together with the lattice friction and solid solution strengthening, the theoretical calculated values of yield strength match well with the experimental results.

The influence of a longitudinal static magnetic field on microstructures and mechanical properties of Ni3Al-based alloy during directional solidification at the growth speed of 25 μm/s and 100 μm/s has been experimentally investigated. Results reflected that the utilization of a 0.5 T magnetic field refines the NiAl dendrites at both speeds of growth. When applying a high magnetic field, the columnar-to-equiaxed transition (CET) occurred at growth speed of 25 μm/s and dendrite networks formed at growth speed of 100 μm/s. Tensile property results indicated that the refinement of dendrites enhanced both plasticity and ultimate tensile strength of Ni-Al alloy. The change of microstructures and mechanical properties should be attributed to the combined action of the thermoelectric magnetic convection (TEMC) in mushy zone together with the thermoelectric magnetic force (TEMF) acting on the solid. When applying a low magnetic field (0.5 T), the TEMF is too small to fragment the dendrites, and the refined dendrites is mainly due to the TEMC in the interdendritic regions. At a lower growth speed, the TEMF is supposed to strong enough to fragment the dendrites and induce the occurrence of CET under 2 or 4 T. When the growth speed increased to 100 μm/s, no obvious CET was observed, but a vertical secondary convection is induced by the circulation in the parallel plane, which promotes the growth of secondary and tertiary branches, leading to the formation of abnormally developed high order dendrites. The hierarchical dendritic structure was suggested to provide a channel for rapid crack propagation and thus degraded the mechanical properties.

Transformation-induced plasticity (TRIP) endows material with continuous work hardening ability, which is considered as a powerful weapon to break the strength-ductility tradeoff. However, FCC based alloys with TRIP effect can not get rid of the “soft” feature of the structure entirely, resulting in insufficient yield strength. Here, a CoxCr25(AlFeNi)75-x high-entropy alloy is designed. NiAl phase is used as strengthening component to improve yield strength, while TRIP effect ensures plasticity. Compared with the previous TRIP high-entropy alloy, its yield strength is nearly doubled, and the uniform elongation is more than 55% at room temperature. Furthermore, the corresponding multiphase microstructure evolution and deformation mechanisms are investigated. Significantly, stacking faults and ∑3 twin boundaries are confirmed to be the nucleation sites of HCP phase by HAADF-STEM. Ingenious composition design and proper heat treatment process make it a perfect combination of precipitation strengthening and transformation-induced plasticity, and thus guide design in the high-performance alloy.

Increasing the yield strength of austenitic steel without significantly sacrificing ductility has been a long-standing technical challenge. Here, we obtained an ultrahigh yield strength (∼1.4 GPa) and ductile (∼37% uniform elongation) austenitic steel through innovatively combining cold rolling, flash annealing, and tempering (CFT) processes. Such CFT steel shows a heterogeneous lamellar microstructure composed of reversed austenite and partially recrystallized austenite. The ultrahigh yield strength is attributed to the synergistic strengthening mechanisms induced by high-density dislocations, nano/ultrafine grains, and nanoscale precipitates. The achieved high ductility is associated with the pronounced transformation-induced plasticity (TRIP) effect induced by the high-density dislocations combined with the twinning-induced plasticity (TWIP) effect induced by grain refinement. Such a strengthening and plasticity mechanism paves the way for a processing route to achieve ultrahigh strength-high ductility combination in austenitic steel.

A β-Ti dendrite reinforced Zr-based bulk metallic glass composite (BMGC) was found to be brittle when cast in a large size. The reasons for the embrittlement and the effectiveness of the cryothermal cycling (CTC) treatment in restoring the mode I fracture toughness are examined. Plasticity in all the CTC treated BMGC is estimated from the distribution and occurrence of pop-ins in nanoindentation tests and by measuring the magnitude of enthalpy of relaxation (ΔHrel) via differential scanning calorimetry (DSC). This is further validated by examining the strain-to-failure (ef) in compression tests. Mode I fracture behaviour of the as-cast embrittled BMGC and the CTC treated BMGC, which exhibits maximum plasticity, is examined. Results show that both BMGCs are equally brittle and exhibit 5 times lower notch toughness (KQJ) than their tougher counterpart. Post-facto imaging of the side surfaces reveals the absence of notch-tip plasticity in both BMGCs. The lack of notch tip plasticity of CTC treated BMGC, despite exhibiting signatures of plasticity in nanoindentation and higher ΔHrel is rationalized by reassessing the origin of pop-ins in nanoindentation tests and describing the variations in chemical and topological short range ordering during CTC, respectively. Implications of these results in terms of improving the fracture toughness of structurally relaxed BMGCs via CTC are discussed.

Grain refinement to the nanocrystalline regime is the most effective way to strengthen materials but this often deteriorates the grain-size thermal stability and plasticity. Here we manufactured a nanocrystalline face centred cubic CrCoNi medium entropy alloy with columnar grains via magnetron sputtering. Compression of CrCoNi pillars with diameters of ∼ 1 µm revealed a record high yield strength of ∼5 GPa for pillars with face centred cubic structures and engineering plastic strain of > 30%. The alloy possessed an outstanding grain-size thermal stability even at 1073 K. Both nanocrystalline grain size and a high density of nanotwins/stacking faults are critical to the exceptional yield strength. Deformation twinning, grains refinement during deformation, grain boundary sliding and random grain orientation all contribute to the large plasticity. The outstanding thermal stability is attributed to the sluggish diffusion effect and the low energy of twin boundaries.

The Mg-4.58Gd-0.45Y-0.01Er alloys with different volume fractions of columnar crystals in hard orientation (orientation factor of 〈a〉 basal plane slip system is less than 0.2) were prepared by changing the pulling rate to regulate the crystal growth orientation. Tensile tests were performed on the Mg-4.58Gd-0.45Y-0.01Er alloy at room temperature, and the structure after deformation was investigated by electron backscatter diffraction (EBSD). Subsequently, the strengthening mechanism of columnar crystals in hard orientation was explored. The results show if orientation factors of 〈a〉 basal plane slip system of columnar crystals are all greater than 0.4 (soft orientation), the alloy has low yield strength σs (64 MPa), but great work hardening ability, and ultimate tensile strength σb and elongation δ are 114 MPa and 37.3%, respectively. If orientation factors of 〈a〉 basal plane slip system of columnar crystals are all less than 0.2 (hard orientation), the alloy has high strength (σs, 125 MPa), but poor plasticity (δ, 6.32%). If the “hard orientation” and the “soft orientation” columnar crystals are arranged alternately along the direction perpendicular to the crystal growth, the alloy has both superior strength (σs, 102 MPa) and excellent plasticity (δ, 22.5%) at room temperature. The improved comprehensive mechanical property can be attributed to two factors. On the one hand, the “hard orientation” columnar crystals can prevent the “soft orientation” crystals deforming, so the strength is improved. On the other hand, the “hard orientation” columnar crystals themselves can withstand a certain amount of deformation to retain appropriate plasticity.

For dental materials, a certain defect tolerance would be beneficial. Some Ceria-stabilized zirconia (Ce-TZP) composites are promising dental repair materials, as they have been shown to exhibit an obvious amount of transformation-induced plasticity with almost no dispersion in strength data. The purpose of this study was to design a novel tricalcium silicate (C3S)-based dental repair material by adding 10 mol.% Ce-TZP to improve fracture toughness and dipotassium hydrogen phosphate (K2HPO4) as the setting accelerator. The study evaluated the physicochemical properties, in vitro cell activity, and antibacterial activity of Ce-TZP/C3S composite cement, and the results revealed that Ce-TZP/C3S cement showed a fast-setting ability and good washout resistance when the setting time was controlled within 26–43 min. With increasing Ce-TZP content, the mechanical properties, especially the flexural strength and fracture toughness, were gradually enhanced. Additionally, the 30% Ce-TZP/C3S composite showed good antibacterial activity and in vitro cytocompatibility. The study concluded that 30% Ce-TZP/C3S composites could be regarded as ideal candidates in the field of dental materials due to their excellent physical and chemical properties, antimicrobial activity, in vitro cytocompatibility, outstanding fracture toughness and fast-setting ability.

This paper focuses on the interface failure in metal/GFRP laminates on account of the high-velocity impact phenomenon by a hemispherical projectile. The study considers three laminates in which the failure inside the 8-layer 0/90 GFRP laminate is compared with the other two laminates that include metal layers in their layup configuration. The metal layers were placed on the top and bottom on one type of laminates while in the other additional metal layers are placed symmetrically inside the layup as well. They were subjected to high-velocity impact by a hemispherical projectile at different energy levels and the idea is not to perforate the laminate configuration instead to account for the damage incurred in these laminates and the role of metal layers in providing resistance to damage within these laminates. The study utilizes experimental findings and proposes a rate-dependent Finite Element (FE) model consisting of the Hashin-Puck failure scheme for composite and the Johnson-Cook damage model for metal layers. The results of the model satisfactorily agree with their experimental counterparts and provide valuable insight into the damage resistance inside the laminates. It has been observed that the 8-layer GFRP laminate was good in terms of elastic recovery and prevention of propagation of damage inside the laminates only, till the impact energy was lower. For higher impact energy, they show poor damage resistance as the fiber failure is triggered in them. However, laminates with metal layers are shown to protect the laminate by dissipating energy in the delamination of metal/GFRP interface, shear failure of the metal layer, and on account of metal plasticity. The study further shows that the through-thickness compressive stresses were responsible for the failure of laminates and also triggering the delamination in them. A damage energy study was performed to investigate the amount of energy dissipating in various failure modes like delamination, matrix cracking, fiber failure, etc.

Magnesium alloys are frequently subjected to biaxial stress during manufacturing process, however, the work hardening behavior under such circumstance are not well understood. In this study, the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated. The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state, resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading, with the elastic-plastic transition part of work hardening extended and stage III hardly emerged. Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basal 〈a〉 slip during biaxial loading tests. While the thickness strain is primarily accommodated by pyramidal 〈c + a〉 slip at the initial stage of biaxial deformation, {10–11} contraction twinning is activated at larger plastic strain. The low activation of non-basal 〈a〉 slip also retards the dynamic recovery and cross-slip of basal and prismatic 〈a〉 slips, leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.

By observing the microstructure evolution of Mg-Ga alloy during tensile deformation, it is found that the prismatic slip and the pyramidal slip occur during the tensile process at room temperature, which finally leads to the plenty of dislocation accumulation. After 8% tensile deformation, the { 10 1 ¯ 2 } extension twin is the main way to coordinate the strain in the c-axis direction for the alloy with the Ga content lower than 2 wt.%, but the pyramidal slip is the main way to coordinate the strain along the c-axis direction for the alloy with the Ga content higher than 2 wt.%. The Ga addition can promote the activation of the non-basal slip, which is beneficial to the work-hardening of the alloy to achieve better plasticity. Dynamic precipitation can slightly reduce the increment of dislocations. The preparation method of high strain rate rolling (HSRR) is another important reason for the plasticity of magnesium alloy sheets, and it is an important embodiment of the application of the dislocation engineering concept in magnesium alloy. The non-basal dislocations derived from the HSRR deformation can provide the non-basal dislocation sources when magnesium alloy is deformed at room temperature, resulting in good ductility. This study can be used as a reference for preparing wrought magnesium alloy with high strength and high plasticity by Ga alloying and hot deformation.

Nanocrystalline metals often display a high strength up to the gigapascal level, yet they suffer from poor plasticity. Previous studies have shown that the development of hetero-sized grains can efficiently overcome the strength-ductility trade-off of nanocrystalline metals. However, whether this strategy can lead to the fabrication of nanocrystalline nanowires exhibiting both high strength and superplasticity is unclear, similar to the atomistic deformation mechanism. In this paper, we show that ultra-small nanocrystalline Au nanowires comprising grains in both the Hall–Petch and inverse Hall–Petch grain-size regions can exhibit extremely high uniform elongation (236%) and high strength (2.34 gigapascals) at room temperature. In situ atomic-scale observations revealed that the plastic deformation underwent two stages. In the first stage, the super-elongation ability originated from the intergrain plasticity of small grains via mechanisms such as grain boundary migration and grain rotation. This intergrain plasticity caused the grains in the heterogeneous-structured nanowires to grow very large. In the second stage, the super-elongation ability originated from intragrain plasticity accompanied by the diffusion of surface atoms. Our results show that the hetero-grain-sized nanocrystalline nanowires, comprising grains with sizes both in the strongest Hall–Petch effect region and the inverse Hall–Petch effect region, were simultaneously ultra-strong and ductile. They displayed neither a strength-ductility trade-off nor plastic instability.

Natural gas hydrate (NGH) reservoirs consist of the types of sediments with weak cementation, low strength, high plasticity, and high creep. Based on the kinetics and thermodynamic characteristics of NGH decomposition, herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term drilling. The results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range, thus aggravating the plastic strain accumulation around the wellbore. Furthermore, the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress, as a result, the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ stress. The lower the pore pressure, the greater the stress concentration effects and the higher the plastic strain at the wellbore. Moreover, the lower the initial NGH saturation, the greater the initial plastic strain and yield range and the higher the equivalent creep stress. The plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.

A novel yield criterion based on CPB06 considering anisotropic and tension-compression asymmetric behaviors of magnesium alloys was derived and proposed (called M_CPB06). This yield criterion can simultaneously predict the yield stresses and the Lankford ratios at different angles (if any) under uniaxial tension, compression, equal-biaxial and equal-compression conditions. Then, in order to further describe the anisotropic strain-hardening characteristics of magnesium alloy, the proposed M_CPB06 criterion was further evolved to the M_CPB06ev model by expressing the parameters of the M_CPB06 model as functions of the plastic strain. As the model was developed, the stresses and Lankford ratios of AZ31B and ZK61M magnesium alloys at different angles under tensile, compressive and through-thickness compressive conditions were used to calibrate the M_CPB06/M_CPB06ev and the existing CPB06ex2 model. Calibration results reveal that compared with the CPB06ex2 yield criterion with equal quantity of coefficients, the M_CPB06 criterion exhibits certain advancement, and meanwhile the M_CPB06ev model can relatively accurately predict the change of the yield locus with increase of the plastic strain. Finally, the M_CPB06ev model was developed through UMAT in LS-DYNA. Finite element simulations using the subroutine were conducted on the specimens of different angles to the rolling direction under tension and compression. Simulation results were highly consistent with the experimental results, demonstrating a good reliability and accuracy of the developed subroutine.

For a homogeneous, continuous, and isotropic material whose constitutive relationships meets with the Ramberg-Osgood law (R-O law), the energy in the elastoplastic indentation with a ball indenter was theoretically analyzed, and the proportional superposition of energy in pure elasticity and pure plasticity during indentation was considered based on the equivalence of energy density. Subsequently, a Proportional Superposition-based Elasto Plastic Model (PS-EPM) was developed to describe the relationships between the displacement and the load during the ball indentation. Furthermore, a new test method of Ball Indentation based on Elastoplastic Proportional Superposition (BI-EPS) was developed to obtain the constitutive relationships of R-O law materials. The load–displacement curves predicted using the PS-EPM model were found to agree closely with the Finite Element Analysis (FEA) results. Moreover, the stress vs. strain curves predicted using the BI-EPS method were in better agreement with those obtained by FEA. Additionally, ball indentation was performed on eleven types of metal materials including five types of aluminum alloys and six types of steel. The test results showed that the stress vs. strain relationships and the tensile strength values predicted using the proposed BI-EPS method agreed well with the results obtained using conventional uniaxial tensile tests.

The excellent shape memory and mechanical properties of TiNi shape memory alloys (SMAs) fabricated using selective laser melting (SLM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti2Ni precipitates in a Ti50.6Ni49.4 SMA fabricated using SLM. Specifically, because of the complete solution treatment, nanoscale spherical Ti2Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cycles. These simultaneously enhanced properties are considerably superior than those of most previously reported TiNi SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti2Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti2Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in TiNi SMAs and will accelerate the wider application of SMAs.

In the present study, the micro-mechanical behavior of CoCrFeMnNi high-entropy alloy was investigated using an in-house micro-tensile setup at room temperature and 550 °C at different strain rates. Micro-mechanical properties are compared with those obtained using a commercial macro-tensile setup to check a potential sample size effect. Results show that mechanical properties such as yield strength, ultimate tensile strength and uniform elongation are independent of the sample size. However, the total elongation-to-failure of micro-samples is found to be lower than those of macro-counterparts. Apart from this, the material exhibits serrated plastic flow, which is strain rate dependent in terms of the onset strain and shape of serrations at 550 °C. Furthermore, transmission electron microscopy investigations were performed to correlate the occurrence of serrations to the observed distinct dislocation structures. Microstructural results provide direct evidence that dislocations are curved and hence effectively pinned and unpinned at the lowest applied strain rate, which might be responsible for the occurrence of serrated plastic flow.

MgAlON transparent ceramic was prepared via pressureless sintering and post hot isostatic pressing. The in-line transmittance of MgAlON ceramic exceeds 80% in the range 0.39–4.67 μm, and the ceramic was fully dense with average grain sizes ∼55 μm. The mechanical properties at the grain boundary (GB) and the center of the grain (CG) of MgAlON ceramic was investigated by nanoindentation at forces of 1 × 102–3 × 105 μN. The results indicated that the hardness values of MgAlON ceramic were sensitive to the testing forces and measurements position. The hardness at GB zone was lower than that at CG zone, which was probably ascribed to weaker interatomic bonding force in GB area. The Meyer's index of the hardness in GB and CG regions is 1.87 and 1.82, respectively. There is a weaker ISE in GB area of MgAlON as a result of larger plasticity and smaller elasticity. The hardness values of GB and CG regions are ∼13.36 GPa and ∼13.58 GPa, respectively.

An attempt has been made in this study by employing the Deshpande and Fleck constitutive model, which is available in the ABAQUS software as the crushable foam material model, to reflect the stress-strain behavior of dental implants made of titanium foam (Ti-foam) under fatigue loading. For comparison purposes, solid Ti has also been considered in the study. Before proceeding to the study of fatigue loading effect on the implant, the modelling approach has been tested with the results of a compression test available in the open literature. Equivalent plastic strain, effective stress, and hydrostatic stress qualities have been generated for various porosity levels. Fatigue loadings corresponding to all three directions namely, lingual, axial, and mesio-distal directions have been applied on the implant for 50 load cycles in order to observe the fatigue loading effect on the implant. It has been observed from the simulation results that under identical conditions, stress generated in the Ti-foam material is less and Ti-foam can also transfer more loads to the surrounding bones as compared to the correspondings of solid Ti material. Therefore, Ti-foam based implant can solve the stress shielding effect and hence Ti-foam is a suitable alternative of the solid Ti for fabricating dental implants.

The effects of cryogenic thermal cycling on deformation behaviour and structural variation of {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 bulk metallic glass (BMG) were studied and compared with Cu-free [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 BMG. After thermal-cycled treatment between 393 K and cryogenic temperature, the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG obtained a plastic strain of 7.4% combined with a high yield strength of 4350 MPa. The excellent soft magnetic properties were maintained after CTC treatment. The minor addition of Cu element results in an initial nano-sized heterogeneity in the matrix, which facilitates the rejuvenation process during thermal cycling, and brings to a low optimal thermal temperature of 393 K, making the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG more attractive in industrial application. During thermal cycling, the formation of more soft regions leads to the increase of structural heterogeneities, which is beneficial to the initiation of shear transition zones and the formation of multiple shear bands, and thus results in the enhancement of plasticity. This study links the subtle variation of specific structure with macroscopic mechanical properties, and provides a new insight of composition selection for cryogenic thermal cycling treatment.

This paper presents the effect of plasticity and the limit states on the electrical resistivity of bentonite as grounding material. The material used in this study was extracted from Andrassy volcanic formations in Tawau district. The geotechnical properties such as the plasticity characteristic, water content and electrical resistivity of the bentonite were investigated. The electrical resistivity was measured at different limit state of the bentonite using a soil box and a 4-pin resistivity meter. In this study, the Andrassy bentonite showed appropriate composition and technical properties commonly associated in electrical grounding application. Test results indicated that the electrical resistivity is somewhat similar to most bentonites. The resistivity values were found to vary with the bentonite limit state. Water content greatly influences the electrical resistivity of the bentonite. Under dry solid-state, the resistivity is the highest at 11 kΩm. Surprisingly, under liquid state, three distinct resistivity values were observed. Under wet conditions, the resistivity were 4500, 180 and 1.8 Ωm for semi-solid, plastic, and liquid states, respectively. Thus, it is expected that bentonite performance as good grounding enhancement material depends on its wet conditions, mainly when the water content is greater than the plastic limit.

Dislocation plays a crucial role in controlling the strength and plasticity of bulk materials. However, determining the densities of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) is one of the classical problems in material research for several decades. Here, we proposed a new approach based on indentation size effect (ISE) and strengthening theories. This approach was performed on a laser powder bed fused (L-PBF) Hastelloy X (HX), and the results were verified by the Hough-based EBSD and modified Williamson–Hall (m-WH) methods. Furthermore, to better understand the new approach and essential mechanisms, an in-depth investigation of the microstructure was conducted. The distribution of dislocations shows a clear grain orientation-dependent: low density in large preferentially orientated grains while high density in fine orientated grains. The increment of strengthening in L-PBF HX is attributed to a huge amount of edge-GNDs. Planar slip is the main operative deformation mechanism during indentation tests, and the slip step patterns depend mostly on grain orientations and stacking fault energy. This study provides quantitative results of GND and SSD density for L-PBF HX, which constructs a firm basis for future quantitative work on other metals with different crystal structures. Funding agencies: The Swedish Governmental Agency for Innovation Systems (Vinnova Grant No. 2016-05175) and the Center for Additive Manufacturing-metal (CAM2). Siemens Energy is acknowledged for providing the samples.

The response of crystalline materials to elasto-plastic cyclic loading is reviewed and analyzed. The important parameters characterizing the cyclic plastic response of single crystals, polycrystals, and multiphase materials are presented and related to the internal dislocation structure. Cyclic plastic strain localization is shown to be the characteristic feature of cyclic plastic straining which leads to surface relief formation and fatigue crack initiation. Recent models of fatigue crack initiation are presented. The mechanisms and kinetics of early crack growth are reviewed and the analysis of the relation of the crack growth kinetics and fatigue life curves is suggested.

This work deals with studying staging and macroscopic strain localization in austenitic stainless steel 12Kh18N9T within a temperature range of 143 K < T < 420 K. The visualization and evolution of macroscopic localized plastic deformation bands at different stages of work hardening were carried out by the method of the double-exposure speckle photography (DESP), which allows registering displacement fields with a high accuracy by tracing changes on the surface of the material under study and then comparing the specklograms recorded during uniaxial tension. The shape of the tensile curves σ(ε) undergoes a significant change with a decreasing temperature due to the γ-α'-phase transformation induced by plastic deformation. The processing of the deformation curves of the steel samples made it possible to distinguish the following stages of strain hardening, i.e. the stage of linear hardening and jerky flow stage. A comparative analysis of the design diagrams (with the introduction of additional parameters of the Ludwigson equation) and experimental diagrams of tension of steel 12Kh18N9T for different temperatures is carried out. The analysis of local strains distributions showed that at the stage of linear work hardening, a mobile system of plastic strain localization centers is observed. The temperature dependence of the parameters of plastic deformation localization at the stages of linear work hardening has been established. Unlike the linear hardening, the jerky flow possesses the propagation of single plastic strain fronts that occur one after another through the sample due to the γ-α' phase transition and the Portevin-Le Chatelier effect. It was found that at the jerky flow stage, which is the final stage before the destruction of the sample, the centers of deformation localization do not merge, leading to the neck formation.

Metal-organic framework (MOF) glasses provide new perspectives on many material properties due to their unique chemical and structural nature. Their mechanical properties are of particular interest because glasses are inherently brittle, which limits their applications as structural materials. Here we perform strain-rate-dependent uniaxial micropillar compression experiments on agZIF-62, agZIF-UC-5, and agTIF-4, a series of MOF glasses with different substituting linker molecules, and find that these glasses show substantial plasticity, at least on the micrometer scale. At a quasi-static strain rate of 0.001 s-1, the micropillars yielded at approximately 0.32 GPa and subsequently deformed plastically up to 35% strain, irrespective of the type of substituting linker. With increasing strain rate, the yield strength of agZIF-62 evolved with the strain-rate sensitivity m = 0.024 to reach a yield strength of 0.44 GPa at a strain rate of 510 s-1. On the basis of this relatively low strain-rate sensitivity and the absence of serrated flow, we conclude that structural densification is the predominant mechanism that accommodates such extensive plasticity.

The development of ultrastrong maraging stainless steels (MSSs) is always in high demand. However, traditional high-strength MSSs generally exhibit early plastic instability with a low uniform strain since the precipitated nanoparticles are non-coherent with the body-centered-cubic (BCC) lath martensitic matrix. Here, we design a novel ultrahigh strength MSS (Fe-5.30Cr-13.47Ni-3.10Al-1.22Mo-0.50W-0.23Nb-0.03C-0.005B, wt.%) using a cluster formula approach. A fabulous microstructure consisting of a uniform distribution of high-density coherent B2-NiAl nanoprecipitates (3−5 nm) in BCC martensitic matrix was successfully obtained. This alloy has not only an exceedingly high ultimate tensile strength of 2.0 GPa, but also a decent uniform elongation of 4.2%−5.1%, which is almost triple of the value observed in existing MSSs. We present an in-depth discussion on the origins of ultrahigh strength and uniform plastic strain in the new alloy to validate our design strategy and further offer a new pathway to exploit high-performance MSSs.

Polysynthetic twinned (PST) TiAl single crystal possesses great potentials for high-temperature applications due to its excellent combination of strength, ductility and creep resistance. However, a critical property for high-temperature application of such material involving high-temperature fatigue properties remains unknown. Here, the high-temperature high-cycle fatigue performance of PST TiAl single crystal has been studied. The result shows that PST TiAl single crystal can withstand more than 107 cyclic loadings at 975 °C under a stress amplitude of 270 MPa, which is significantly higher than traditional TiAl alloys. Experimental observations and atomistic simulations indicate that the improvement of fatigue resistance is attributed to the plastic strain delocalization in uniform lamellar structure, and the plastic deformation is well-distributed and sufficient in each lamella. Even in the α2 lamella with difficult slippage, a large number of stacking fault structures can be observed. The 〈c + a〉 dislocations in α2 tend to dissociate into a Frank partial with b = 1/6 2 ¯ 0 3 ¯ >, forming a ribbon of I1 fault which ensures the continuity of deformation.

We reported the fracture behavior of multimodal AA7075-B4C composites with three types of coarse grains (CG, AA7075 powder-1 μm, AA7075 powder-10 μm, and as-cryomilled AA7075 powder) synthesized via cryomilling and plasma activated sintering. Our results indicated that the type (particle size) and weight fraction could affect the distribution of CGs, which in turn significantly affect the fracture behavior of multi-modal composites. Multiple voids were found in the vicinity of AA7075 powder-1 μm, leading to a limited plasticity even with a lower yield strength. AA7075 powder-10 μm (25%) could distribute homogeneously in the composites, resulting in a high yield strength (712 ± 24 MPa) with the plasticity of ~7.7%. The localized grain growth occurred during consolidation with addition of as-cryomilled AA7075 powder. Noted that once the continuous distribution of CGs were detected in the composites, the yield strength decrease dramatically. The CGs could enhance the plasticity by retarding the propagation of micro-cracks during deformation.

Despite being strong with many outstanding physical properties, tungsten is inherently brittle at room temperature, restricting its structural and functional applications at small scales. Here, a facile strategy has been adopted, to introduce high-density dislocations while reducing grain boundaries, through electron backscatter diffraction (EBSD)-guided microfabrication of cold-drawn bulk tungsten wires. The designed tungsten microwire attains an ultralarge uniform tensile elongation of ~10.6%, while retains a high yield strength of ~2.4 GPa. in situ TEM tensile testing reveals that the large uniform elongation of tungsten microwires originates from the motion of pre-existing high-density dislocations, while the subsequent ductile fracture is attributed to crack-tip plasticity and the inhibition of grain boundary cracking. This work demonstrates the application potential of tungsten microcomponents with superior ductility and workability for micro/nanoscale mechanical, electronic, and energy systems.

The present work aims to address the effects of the sintering temperature (800–1500 °C) on the mechanical properties and material removal mechanisms of 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) based on a series of nanoindentation and nanoscratch experiments. The impacts of the sintering temperature on the mechanical properties, including plasticity, deformation behavior, indentation energies, and cracking resistance were rigorously studied. The acquired results indicate that 1100 °C signifies the transition threshold for the ceramic microstructure, leading to the entirely different mechanical properties and indentation responses for materials sintered at temperatures lower or higher than the threshold value. Moreover, 1100 °C is also a transition threshold of the material removal mechanism, before which the material removal mechanism is dominated by the plastic regime, and beyond which, the material removal mechanism tends to show ductile-brittle characteristics.

A novel TiNb fibre with an α-Al2O3 coating was fabricated by cathodic plasma electrolytic deposition (CPED), which has enormous potential for use in intermetallic matrix composites (IMMCs). This study aims to clarify the microstructural evolution of α-Al2O3 coatings on TiNb fibres and to systematically evaluate the mechanical properties of such modified fibres. The results revealed that the CPED process can be divided into three stages as voltage and deposition time increased: gas film formation, spark discharge, and spark fading, where the coating successively underwent local nucleation, uniform deposition, micropore self-sealing, and loose structure formation. The optimum deposition parameters of the deposition voltage of 300–400 V and deposition time of 3–4 min were determined, under which the α-Al2O3 coating combined tightly with the TiNb fibre matrix, micropores were completely self-sealed, and the loose structure and detrimental phase transitions in TiNb were effectively avoided. The fracture strength calculated by the Weibull method suggested that the fracture strength of the modified Al2O3/TiNb fibre was enhanced by more than 30%; this improved strength maintained high stability, benefiting from the intact α-Al2O3 ceramic coating. In particular, the fibre coated at 300 V for 4 min had the highest strength reaching 1620 MPa. The fracture morphology presented marked necking and shear lip characteristics, indicating excellent plasticity.

Cu content has been successfully optimized in a thixo-cast and directly aged (T5-treatment) Al–7Si–0.5Mg (wt.%) alloy. Even after the 0.5% Cu addition, plate-like Al2Cu (θ’) phases, which contribute to high strengths and large plasticity, are precipitated. The formation of a large fraction of Cu-containing brittle phases could be suppressed as well. Then, the Al–7Si–0.5Mg–0.5Cu alloy exhibits high ultimate tensile strength, 0.2% proof stress, and elongation to failure of 296 MPa, 209 MPa, and 8.8%, respectively. This results in a high quality index similar to that of solution-treated and subsequently aged (T6-treated) Al–7Si–Mg alloys. A Cu addition over 1.0% further improves the strengths; however, this leads to poor ductility because of the high fraction of Cu-containing brittle phases.

As an eco-friendly inorganic cementitious matrix material, a geopolymer mortar combined with short-cut fibers and fiber meshes represents a novel strengthening system, which has been proven to be effective in strengthening existing concrete structural members. However, the behavior of cement concrete cylinders confined by fabric-reinforced geopolymer mortar (FRGM) under compression is unclear. Therefore, in this work, experimental studies were performed to investigate the effects of the number of strengthening layers, matrix strength of the strengthening system, and loading path on the compressive behavior of basalt–FRGM-confined concrete. The experimental results show that two or three layers of the FRGM jacket can help substantially improve the peak stress and its corresponding axial deformation, ductility, and energy absorption ability. The envelope of the cyclic stress–strain curve is consistent with the monotonic stress–strain curve of an identical group of specimens with the same confinement. The residual plastic strain increases with repeated loading cycles, whereas the new reloading stress deteriorates. Regression models are proposed to predict the peak stress and corresponding axial strain in the basalt-FRGM-confined concrete. Finally, monotonic and hysteretic constitutive models for the FRGM-confined cement concrete are developed and compared with the experimental curves. The experimental results provide new insights into the strengthening properties of geopolymer composites and theoretical support for their application. Notably, geopolymer composites can be used in repairing aging and damaged concrete structures while ensuring a low carbon footprint.

Because large plastic deformation occurs in hydroforming bellows there is a residual stress distributing in the metal after forming, which is complex and not easy to be measured. The existence of residual stress might have an effect on the corrosive property and bulking performance of bellows. A finite element model was established to simulate the forming residual stress of the nickel alloy multi-layer bellow. The distribution of residual stress was calculated out and validated by cosα X-ray diffraction measurement. Thus the forming mechanics and the effects of layer number and forming pressure on the residual stress in the hydroforming bellow were both discussed in detail based on the established model. It was shown that the calculated residual stress had the same trend with the experimental results. The axial and circumferential residual stresses at the outer surface of the peak were both compressive. There existed the maximal Von Mises stress at the inner surface of the peak of the bellow. At this position the radial and axial residual stresses were both tensile. When applying multi-layer bellows and less forming pressure a lower forming residual stress could be obtained because of the narrow plastic strain region during forming.

An analytical approach is established to analyze the mechanical behavior of a unidirectional (UD) composite subjected to an in-plane shear. The effects of the interface debonding on the in-plane shear strength and plasticity of the composite are evaluated respectively. The volume-averaged internal stresses of the fiber and matrix are calculated through Bridging Model. Owing to the stress fluctuation in the matrix caused by other phases (such as the imbedded fiber and interface crack), the homogenized matrix stresses must be converted into true values based on a stress concentration factor (SCF). A new in-plane shear SCF of a composite with debonded interface is derived and applied to the predictions of strain and strength in this paper. Moreover, the contribution of the relative slippage between fiber and matrix to the non-linear shear deformation of the composite is analyzed. Finally, the efficiency and accuracy of our theory are verified with a series of examples. The approach is very efficient because the calculation can be achieved with explicit expressions mainly based on the constituent material properties. The comparisons between predicted strength and deformation with the experimental results show that our analytical approach can give out reliable underlying data for multi-scale analysis. Moreover, this theoretical method can tell if and how much the interface of a composite needs to be modified for a given load environment.

Micromechanics simulations of fiber-reinforced polymer-matrix composites with waviness defects are conducted to investigate the effect of constitutive model selection on the nucleation, evolution, ...

ConspectusFractures in metallic materials such as ductile austenitic, ferritic, and dual-phase steels often occur after significant plastic deformation. The dislocation-driven plasticity enhances t...

Different mechanical properties characterise the materials of 3D printed components, depending on the specific additive manufacturing (AM) process, its parameters, and the post-treatment adopted. Specifically, stereolithography (SLA) uses a photopolymerisation technique that creates solid components through selective solidification. In this study, 72 specimens were 3D printed using 12 commercial-grade methacrylate resins and tested under uniaxial tensile loads. The resin specimens were evaluated before and after curing. The recommended cure temperature and time were followed for all materials. The stress-strain curves measured during the testing campaign were evaluated in terms of maximum tensile strength, Young’s modulus, ductility, resilience, and toughness. The results reveal that the curing process increases the material stiffness and resistance to tensile loads. However, it was found that the curing process generally reduces the plasticity of the resins, causing a more or less marked brittle behaviour. This represents a potential limitation to the use of SLA 3D printing for structural elements which require some plasticity to avoid dangerous sudden failures.

Hydrogen embrittlement is a phenomenon that affects the mechanical properties of steels intended for hydrogen transport. One affected by this embrittlement is the ductile–brittle transition temperature (DBTT). This temperature is conventionally defined and compared to service temperature as an acceptability criterion for codes. Transition temperature does not depend only on the material, but also on specimen geometry, particularly the thickness. This phenomenon is attributed to the plasticity constraint described by several parameters as the effective stress T, the out-of-plane stress Tz and the parameter Ae=0.3% related to the surface covered by plastic strain iso-lines. Generally, the transition temperature is defined for a conservative reason by the Charpy impact test. Standard Charpy specimens are straight beams with a thickness of 10 mm. For thin pipes, it is impossible to extract this type of the standard specimen. One uses in this case mini-Charpy specimens with a reduced thickness due to pipe curvature. This paper aims to quantify the effect of hydrogen embrittlement on the transition temperature of pipe steel (API 5L X65) as well as the effect of Charpy specimen thickness. Three plastic constraint parameters (Teff, Rp, and Ae=0.3%) are computed to get a correlation between plastic constraint and the shift of the transition temperature.