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The study of damage and failure in fractured rock masses is crucial. This study employs the representative volume element (RVE) method to develop a microscale rock model. The model simulates the propagation and rupture of fractures by integrating factors including actual mineralogical composition, the Weibull distribution function, the Mohr–Coulomb damage criterion, and strain softening. Results indicate that fractures reduce the uniaxial compressive strength of the rock and that peak strength is significantly correlated with crack geometries. Plastic damage in rocks was categorized into three stages: elastic, rapid growth, and postpeak softening. A logistic growth model describes the plastic volume change curves for rocks with various fracture geometries, establishing the relationship between plastic damage volume and damage variables. Constitutive models for rocks with varying fracture geometries under uniaxial compression were formulated. The accuracy and applicability of these models were validated, providing a theoretical basis for rock engineering applications. Highlights: A heterogeneous plastic damage model based on representative volume elements is developed.A logistic growth model was used to describe the plastic volume change curves for rocks containing different fracture geometries.The relationship between rock plastic damage volume and damage variables was established.Plastic damage constitutive models of rocks containing different fracture geometries under uniaxial compression were obtained and validated. [ABSTRACT FROM AUTHOR]

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Existing studies typically explore the differences in seismic performance evaluation results of different evaluation models for concrete gravity dams by analyzing amplitude factors while neglecting the influence of ground motion duration. As a result, the influence of different evaluation models on the seismic performance of gravity dams can not be evaluated comprehensively. This paper, using the efficacy coefficient method, integrated the overall damage index of the dam body and the relative displacement of the dam crest to construct a comprehensive seismic damage evaluation model for gravity dams. Taking the Koyna gravity dam as the research subject, this paper examined the influence of ground motions with different strong seismic motion durations on the seismic damage degree of the dam body under both single-indicator and multi-indicator evaluation models, and the analysis results of different evaluation models on the seismic performance of gravity dams were compared. The result indicates that ground motion duration is positively correlated with the damage degree of gravity dams, and relying on a single evaluation indicator may lead to conservative or dangerous evaluations of the damage degree of dam bodies. A comprehensive evaluation model can more accurately reflect the influence of variations in strong seismic motion duration on the damage degree of concrete gravity dams.

This paper presents a unified experimental and numerical investigation on the transition from brittle to ductile behavior in a low-porosity sandstone under drained conditions. The experimental results demonstrate a transition in the mechanical behavior from brittle faulting to dilatant ductile flow at room temperature with an increase in effective confining pressure, suggesting that microcracking-controlled local friction is the underlying plastic deformation mechanism. For constitutive modeling, the sandstone is considered as a heterogeneous medium composed of a pores-weakened elastic solid matrix and distributed microcracks. By following a two-step homogenization procedure and irreversible thermodynamics framework, a micromechanics-based elastoplastic damage model incorporating a non-associated local plastic flow rule is formulated, in which the coupling between plasticity, damage and pore pressure is taken into account. In this context, a non-associated macroscopic effective strength criterion as an inherent part of the corresponding model is derived. Originally, a theoretical linear relation between critical state of damage at peak strength and effective confining pressure is established, which is efficient in describing post-peak softening behavior. Comparisons of numerical simulations with experimental data demonstrate that the proposed model effectively reproduces the main features of the sandstone with a brittle-ductile transition. • A transition from brittle to ductile behavior in a saturated low-porosity sandstone is observed. • A non-associated micromechanics-based constitutive model is developed. • A non-associated macroscopic effective strength criterion is derived. • A linear relation between critical damage and effective confining pressure is established. [ABSTRACT FROM AUTHOR]

In order to avoid joint failure of half grouted sleeve connection due to bond-slip, a method of applying the anchor plate in half grouted sleeve is proposed to improve reliability and mechanical properties of half-grouted sleeve connection. Using the ABAQUS software, considering the bond-slip between the steel bar and the grouting material and the plastic damage of the grouting material, a finite element simulation specimen group with different diameters of steel bars and with or without anchor plates is set up, and the specimen group is monotonically carried out by means of displacement loading. The results show that the bond strength between steel bar and grout increases and the elongation displacement of half grouted sleeve connection decreases with the increase of anchorage length of steel bar under the same diameter. Under the same length of anchorage, with the increase of steel bar diameter, the relative slip between steel bar and grouting material increases, and the elongation displacement of half grouted sleeve connection increases. At the same time, the restriction effect is more obvious with additional anchor plate. Adding the anchor plate avoids the pull-out failure mode of steel bar when the anchorage length of steel bar is equal or less than 8d (d is the diameter of steel bar). The bonding action range of steel bar-grout interface without anchor plate connection is limited. The anchor plate plays a bearing role, and the stress of the steel bar on the side away from the load end is significantly reduced. Therefore, the performance of half grouted sleeve connections can be improved by means of anchor plates. [ABSTRACT FROM AUTHOR]

In the hydrogen environment, hydrogen atoms will stick to the surface of metal materials.Over time, hydrogen atoms will penetrate into the metal and take up empty Spaces.he concentration of hydrogen atoms leads to stress concentration, which ultimately further affects the mechanical behavior of the material.The mechanical response of hydrogen at crack tip is studied by molecular dynamics method.The results show that the hydrogen adsorbed at the crack tip reduces the bonding force between atoms, resulting in a decrease in the critical applied load required for local stress concentration. The material is destroyed under the condition of lower fracture strength, and the crack propagation is promoted to a great extent.The infiltration process of adsorbent hydrogen at the crack tip under applied load was observed, and hydrogen atoms would gather in the high-stress region, resulting in a decrease in the plasticity of the material.In addition, the number of hydrogen atoms infiltrating the material will reach a maximum critical value as the calculation time increases.When the applied strain increases, the maximum number of hydrogen atoms permeating the crack tip and the time to reach the critical value will increase. [ABSTRACT FROM AUTHOR]

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Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The progressive forming process (JCOE process) results in the creation of a high-strength submarine pipeline with substantial wall thickness. However, the accumulated of strain during the transverse forming process leads to increased disparities in the microstructure of layers with varying thicknesses, thereby impacting the longitudinal mechanical properties of the pipes. This investigation explores the combination of three-dimensional (3D) simulation and experimental methods allowed for comparison of how the JCOE process impacts the mechanisms of plastic damage and the evolution of longitudinal grain orientation in layers with varying thicknesses in pipes. It was revealed in the findings that the increase in accumulated strain led to a rise in dislocation density within the grain. This exacerbated dislocation pile-up at ferrite boundaries and ferrite/bainite interfaces and raised the level of plastic damage. A reduction in grain size enhanced the strain gradient in the surface layer, resulting in hindered advancement of plastic damage. From the 1/2-thickness layer towards the surface layer, the crystal orientation tended predominantly towards the [110] direction with the accumulation of strain. At a lower level of the accumulated plastic strain, the predominant orientation of the texture in the 1/2-thickness layer was directed towards the α-fibers. As the accumulated deformation progressed into the 1/4-thickness layer, the α-fiber transformed to a {001}<110> type texture under the combined effect of conjugated slip and cross-slip. The transformation of the {001}<110> type texture into the {112}<110> type texture ensued as the accumulated deformation progressed to the surface layer and tended to shift to the {111}<110> type texture. The results of this work guide methods to control the microstructure and properties of heavy-wall dual-phase steel submarine pipelines. • The change of strain accumulation and properties in the JCOE process. • Mechanism of plastic damage along the thickness in the JCOE process. • Evolution of grain orientation after the JCOE process. • Transformation of the texture type under different strain accumulation. [ABSTRACT FROM AUTHOR]

To improve the seismic performance of coupled shear walls in high‐rise buildings and to eliminate the problems of large residual deformation and relatively small initial stiffness and damping properties of the traditional viscoelastic coupling beam damper (TVCBD), an innovative shape memory alloy (SMA)‐cable‐controlled self‐centering viscoelastic coupling beam damper (SVCBD) with energy dissipation and self‐centering capabilities was designed and investigated in this study. The construction form and operating principles of the SVCBD were proposed, relevant material performance tests of the cables were performed, and good results were obtained. Finally, the contribution of the SVCBD to seismic mitigation of a 10‐story reinforced concrete coupled shear wall structure was verified by seismic time‐history analyses. The results indicated that compared with TVCBD, SVCBD possesses fuller hysteretic curves, showing stronger energy dissipation capacity, higher initial stiffness, and much smaller residual deformation. The initial strain and cross‐sectional area of the SMA cables and the shear area of the viscoelastic plates affect the energy dissipation and self‐centering performance of SVCBD significantly. The seismic response and post‐earthquake residual deformation of the coupled shear wall structure and the plastic damage of the main components can be effectively controlled by utilizing the proposed SVCBD. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hydrogen-induced plastic loss behavior of titanium alloys is often reported, but there are relatively few studies on high-strength aluminum alloys. In this article, the hydrogen-induced plastic damage behavior of 7085-T7651 high-strength aluminum alloy was investigated using a tensile specimen with pre-charging hydrogen, and the microstructure was characterized by transmission electron microscopy, scanning electron microscopy and time-of-flight secondary ion mass spectrometry. The results showed that 7085-T7651 high-strength aluminum alloy material has certain hydrogen embrittlement sensitivities, and with the increase of hydrogen-charging time, the hydrogen content and sensitivity of the material increases significantly. For the first time, the theoretical analysis and intuitive quantitative characterization of the hydrogen-induced plastic loss behavior mechanism on 7085-T7651 high-strength aluminum alloy is stated as the formation of Mg and H segregation formed at the crystal boundary, which will result in the weakening of the crystal boundary. [ABSTRACT FROM AUTHOR]

In recent years, offshore wind power has been developing rapidly, and single piles are among the commonly used foundations for wind turbines. Presently, experimental studies of the grouted connections of pile foundations are limited to the study of scaler models. Numerical simulations are more suitable for the mechanical analysis of the full-size structure instead of experimental ones. In numerical simulations, the linear elasticity model is widely adopted, but the plastic damage is studied scarcely. So, shear bond parameter research concerning grouted joints needs to be supplemented. In this paper, a bilinear random-motion reinforcement model based on the classical metal plasticity theory is adopted for steel, and the model for the grouting material is based on the Sidiroff energy equivalence principle. The plastic damage model for the grouted connecting section is established; the stresses and deformation distribution of the steel pipes and grout in the connecting section are analyzed using the changed shear bond parameters. The results show that the rectangular and triangular shear bonds are more reasonable than the semicircular shear bond transfer. Increasing the height of the shear bond may reduce the maximum stress and the maximum vertical displacement of the grout, and the shear bond width change has less influence on the joint bond stress and displacement. [ABSTRACT FROM AUTHOR]

In this paper, an algorithm is proposed to solve the frictional contact problems while considering elasto-plastic material properties. The static and dynamic solution procedures are derived in incremental form, respectively. The proposed method employs a two-layer iteration strategy. In the outer iteration layer, the equilibrium equations are solved, with the stress and stiffness matrix updated at each iteration. Within the inner iteration layer, the contact force is calculated, where the contact equations, expressed as B-differentiable equations, incorporate only contact conditions in normal and tangential directions, and the contact flexibility matrix, obtained by applying unit force pair to all contact node pairs in turn, is introduced. Consequently, the solution for nonlinear equilibrium equations and contact equations is decoupled, requiring only one decomposition of the stiffness matrix for each calculation of the contact flexibility matrix, as it remains constant within the contact iteration layer. In addition, the constitutive model of concrete developed by Lee and Fenves is utilized. This model adopts two independent variables to describe tensile and compressive damage, together considering the strength recovery of the concrete. Numerical examples demonstrate the accuracy of the proposed method by comparing the results from Abaqus. Furthermore, the present algorithm is applied to static and dynamic analyses of a concrete arch dam with several transverse joints, where the effects of gravity, water level, the number of contact surfaces, and seismic load are considered, and some conclusions are obtained. • An algorithm is developed to solve the elasto-plastic contact problems. • Two-layer iteration strategy is adopted in the proposed method. • Contact equations are expressed in the form of B-differentiable equations. • This method can be applied to static and dynamic analysis of concrete arch dams. [ABSTRACT FROM AUTHOR]

• The anti-collision performance of deck-type arch bridge with gravity foundation is investigated. • The head-on collisions on the bridge pier cause severe damage but the bridge will not collapse. • The head-on collisions on the arch lead to progressive collapse of bridge due to unbalanced thrust action. • The reasonable calculation method of bridge resistance against vessel collision is proposed. Vessel collisions pose significant threats on the safety of cross-channel bridges. Previous studies have paid little attention on the impact performance of common arch bridges with gravity foundations in inland waterways. This study aims to comprehensively investigate the anti-impact resistance and analyze the damage and failure mechanisms of arch bridges under vessel collisions. The entire process of vessel-bridge collision is simulated using three-dimensional explicit finite element technique. The damage characteristics, as well as the progressive collapse process of arch bridge are investigated thoroughly. Moreover, the rational calculation method for bridge lateral resistance against vessel collisions (BRaVC) is discussed. The results show that the gravity foundation bottom section of arch bridge can be fixed in vessel-bridge collision numerical analysis due to insignificant foundation-soil interaction. The head-on barge collision on the bridge pier leads to indistinctive lateral displacement, while obvious local damage can be observed. The impact displacement of the bridge pier is not positively correlated with the impact energy according to the impact load spectra analysis. Barge collision on the main arch results in the progressive collapse of the bridge due to unbalanced horizontal thrust from the arch on the other side. The rational BRaVC can be calculated by using sectional strength based on elastoplastic section analysis. [ABSTRACT FROM AUTHOR]

Plastic damage assessment in 316 austenitic steel was performed in this research by using the misorientation parameters derived from an in situ EBSD technique. With the increase in plastic strain, the misorientation parameters, such as the Grain Reference Orientation Deviation (GROD), Grain Orientation Spread (GOS), the Grain Orientation Spread over the grain Diameter (GOS/D), and Geometrically Necessary Dislocation (GND) density presented a growing trend. Nevertheless, the variation in GROD did not show a monotony trend, and the relative increase in the amplitude of GOS and GND density was less in the late plastic stage. Compared with the above parameters, the (GOS)/D exhibited a near-linear increase during the plastic tensile stage. As the specimen was stretched to a strain of 56.99%, the (GOS)/D increased 8.9 times compared with the original specimen. The results showed that the (GOS)/D parameter has the potential of becoming an indicator for the assessment of plastic damage in 316 steel. [ABSTRACT FROM AUTHOR]

During the vulcanization process of steel-laminated elastomeric bridge bearings, unavoidable flow of elastomer occurs inside the mold under high pressure and nonuniform heating. This may cause the interior steel laminates to misalign or distort in the finished bearing. There has been limited research to understand and quantify the effects of manufacturing imperfections, such as vertically shifted, rotated, and bent steel laminates, on the mechanical behavior of elastomeric bearings. This paper presents a finite element investigation on the effects of manufacturing imperfections on the performance of elastomeric bridge bearings subjected to service-level loads. It is observed that such imperfections have a negligible effect on the maximum shear strain induced in the elastomer. The strain hardening behavior of the elastomer under relatively large shear strains limits the maximum shear strains to values lower than those predicted by the pressure solution. In one cycle of loading, the vertical deflection of bearings is affected slightly by these imperfections. However, manufacturing imperfections can increase the tensile stresses in the steel laminates causing plastic damage. The spread of plastic damage in the steel laminates with repeated cycling may affect the long-term performance of the bearings. [ABSTRACT FROM AUTHOR]

In order to grasp the stress distribution and failure characteristics of the surrounding rock during the final mining in the fully mechanized coal mining face of Lijiahao Coal Mine, the paper uses theoretical analysis, numerical simulation and on-site monitoring and verification methods for analysis and research. The study concluded that: the deformation failure and stress distribution state of the surrounding rock of the retracement channel change continuously as the working surface advances. Advance with the work surface, the confining pressure ratio of the retracement channel is continuously increasing, resulting in an increasing range of damage to the surrounding rock of the roadway, especially when the distance is about 5 m, the deformation and damage of the surrounding rock will increase suddenly with the increase of the confining pressure ratio, after field observation, the results are basically consistent with numerical simulation and theoretical analysis.

In recent years, offshore wind power has been developing rapidly, and single piles are among the commonly used foundations for wind turbines. Presently, experimental studies of the grouted connections of pile foundations are limited to the study of scaler models. Numerical simulations are more suitable for the mechanical analysis of the full-size structure instead of experimental ones. In numerical simulations, the linear elasticity model is widely adopted, but the plastic damage is studied scarcely. So, shear bond parameter research concerning grouted joints needs to be supplemented. In this paper, a bilinear random-motion reinforcement model based on the classical metal plasticity theory is adopted for steel, and the model for the grouting material is based on the Sidiroff energy equivalence principle. The plastic damage model for the grouted connecting section is established; the stresses and deformation distribution of the steel pipes and grout in the connecting section are analyzed using the changed shear bond parameters. The results show that the rectangular and triangular shear bonds are more reasonable than the semicircular shear bond transfer. Increasing the height of the shear bond may reduce the maximum stress and the maximum vertical displacement of the grout, and the shear bond width change has less influence on the joint bond stress and displacement.

The hydrogen-induced plastic loss behavior of titanium alloys is often reported, but there are relatively few studies on high-strength aluminum alloys. In this article, the hydrogen-induced plastic damage behavior of 7085-T7651 high-strength aluminum alloy was investigated using a tensile specimen with pre-charging hydrogen, and the microstructure was characterized by transmission electron microscopy, scanning electron microscopy and time-of-flight secondary ion mass spectrometry. The results showed that 7085-T7651 high-strength aluminum alloy material has certain hydrogen embrittlement sensitivities, and with the increase of hydrogen-charging time, the hydrogen content and sensitivity of the material increases significantly. For the first time, the theoretical analysis and intuitive quantitative characterization of the hydrogen-induced plastic loss behavior mechanism on 7085-T7651 high-strength aluminum alloy is stated as the formation of Mg and H segregation formed at the crystal boundary, which will result in the weakening of the crystal boundary.

Abstract Magnetic Barkhausen Noise (MBN) method is known as an effective nondestructive evaluation (NDE) method for evaluation of residual stress in ferromagnetic materials. Some studies on the feasibility of the MBN method for NDE of residual strains were also conducted and found applicable. However, these studies are mainly focused on the state of residual strains which were introduced through a one-cycle-loading process. In practice, however, structures may suffer from an unpredictable and complicated loading history, i.e., the final state of plastic strain may be induced by several times of large loads. Whether the loading history has influences on MBN signals or not is of great importance for the practical application of the MBN method. In this paper, several ferromagnetic specimens with the same final state of residual strain but of different loading history were fabricated and inspected by using a MBN testing system. The experimental results reveal that the loading history has a significant influence on the detected MBN signals especially for a residual strain in range less than 1%, which doubts the feasibility to apply the MBN method simply in the practical environment. In addition, micro-observations on the magnetic domain structures of the plastic damaged specimens were also carried out to clarify the influence mechanism of loading history on the MBN signals.

Plastic damage assessment in 316 austenitic steel was performed in this research by using the misorientation parameters derived from an in situ EBSD technique. With the increase in plastic strain, the misorientation parameters, such as the Grain Reference Orientation Deviation (GROD), Grain Orientation Spread (GOS), the Grain Orientation Spread over the grain Diameter (GOS/D), and Geometrically Necessary Dislocation (GND) density presented a growing trend. Nevertheless, the variation in GROD did not show a monotony trend, and the relative increase in the amplitude of GOS and GND density was less in the late plastic stage. Compared with the above parameters, the (GOS)/D exhibited a near-linear increase during the plastic tensile stage. As the specimen was stretched to a strain of 56.99%, the (GOS)/D increased 8.9 times compared with the original specimen. The results showed that the (GOS)/D parameter has the potential of becoming an indicator for the assessment of plastic damage in 316 steel.

This paper focuses on the plastic deformation behavior of TC4 titanium alloy under cyclic loading by the finite element method. Finite element models were established based on the realistic microstructure whose volume fraction and gain size of primary α phase are 11.86% and 10.35 μm, respectively. The effect of cyclic loading conditions and microstructure characteristics on cyclic plastic deformation behavior of the alloy was analyzed. The results showed that due to the obvious difference in mechanical properties between primary α phase and transformed β matrix, their equivalent plastic strains are obviously different after different cycles of cyclic loading. Moreover, the equivalent plastic strain gradually decreases with the increase in primary α phase volume fraction, the decrease in primary α phase grain size, the decrease in strain amplitude and the increase in strain ratio, respectively. There is a close relationship between plastic damage and fatigue strength of the metal materials. The cyclic loading conditions and microstructure characteristics have a great influence on the fatigue life of TC4 titanium alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is quite important for the detection and evaluation of material early degradation in order to ensure the durability and integrity of the key engineering components. The collinear wave mixing method is an effective and promising technique capable of detecting and localizing damage in materials. This research reports an investigation for evaluating and locating material plasticity damage in a metallic material by using collinear mixing wave technique. It is found that a third, resonant shear wave would be generated when the resonant condition of two collinear shear and longitudinal waves is satisfied. By controlling the triggering times of the signals that excite the primary waves, this wave mixing method is capable of scanning the cylindrical metallic specimens. Distributions of the amplitudes of resonant shear waves along the specimen can thus be obtained. Experimental study and numerical simulation show that amplitudes of the resonant shear waves are significantly increased at the plastic damage zone compared with that at the undamaged zone with same position on the specimen. It is demonstrated that this wave mixing technique has great potentials for identifying and evaluating the locations of the plastic damage zone in engineering. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Underground coal seam gas drainage is an effective method to lower the risk of coal and gas outburst disaster. However, it is difficult to drainage gas in the low-permeability coal seam, especially low-permeability thick coal seam with a tectonic coal sub-layer. Due to the special structure of this coal seam, many conventional technologies are inefficient. In this paper, to stimulate the coal seam gas drainage, we proposed a hydraulic flushing cavitation technology. Theory analysis, numerical simulation and field tests ware carried out to study the stress relief and permeability increase after adopting this technology. The results indicated that a large hole was formed in the coal seam, which enlarged the scope of stress relief and plastic damaged, and the coal seam permeability and gas drainage efficiency increased significantly. [ABSTRACT FROM AUTHOR]

The progressive forming process of J-forming, C-forming, O-forming, and expansion (JCOE process) is an effective approach for manufacturing high-strength and high-strain offshore pipelines. However, the difference in microstructure of each layer along the thickness increases due to the strain accumulation and deformation direction during pipe forming, which affects the properties. In this study, the effects of the JCOE process on the microstructure evolution and deformation mechanism of heavy-wall ferrite-bainite dual-phase offshore pipeline steel along the thickness were investigated using a combination of simulation and experiment. The results revealed that the higher accumulated strains in the outer and inner layers increased localized microstrain and ferrite hardening and improved the overall strength. However, the pile-up of many dislocations at the ferrite-bainite interface promoted the generation of cleavage facets, increasing the plastic damage. The outer layer had a consistent deformation direction in the JCOE process, promoting dislocations to slip toward the phase interface. Dislocations in the inner layer slipped and annihilated in the opposite direction by back stress due to reverse deformation. The work-hardening behavior of each layer after JCOE process was divided into two stages and decreased with the increase of accumulated strain. Furthermore, the cyclic plastic deformation reduced the plastic damage and ensured the deformation capacity. This work is valuable for the development and control of microstructural characterization and forming fabrication of high-strength, high-strain offshore pipelines. [Display omitted] • Evolutionary patterns of cumulative strain and microstructure during JCOE. • The increase in accumulated strain facilitates the promotion of cleavage facets. • The deformation direction of each layer affects the distribution of dislocations. • The work-hardening capacity decreases with increasing accumulated strain. • Cyclic plastic strain reduces plastic damage and ensures deformability. [ABSTRACT FROM AUTHOR]

• A refined numerical model including shield tunnel and vehicle, and the model of shield tunnel includes anti-collision wall, segment rings, bolts connecting segments, reinforcement cage inside the segment lining. • High level accuracy of various simulation cases of collision can be achieved. • Structural response of all components of shield tunnel can be obtained for analysing the failure mechanism of shield tunnel structure. • Contribution degree of all designing factors in the simulation can be quantitative evaluated. Shield tunnels account for an essential part of the urban highway system, which are more likely to encounter terrible traffic accidents during daily operation. There is a risk of collision between the errant vehicle and the shield tunnel when a traffic accident occurs. This paper establishes a refined numerical model of the shield tunnel based on the Wuhan Yangtze River Tunnel and the vehicle numerical model. Considering the four factors (vehicle weight, speed, collision angle, ground reaction coefficient), an orthogonal test scheme designing 9 simulation cases is proposed. During the collision, the dynamic responses (opening and dislocation of segment joints, stress, and plastic damage of shield tunnel lining) are studied. Results show that the anti-collision wall and segment lining are damaged to varying degrees, and bolts and reinforcement bars in the collision area reach their yield strength; meanwhile, segment joints appear to have irreversible opening and dislocation. According to the extremum difference analysis of orthogonal simulation results, vehicle weight and speed are the two leading factors in structural responses, the contribution degree of which is significantly larger than collision angle and ground reaction coefficient in structural responses. [ABSTRACT FROM AUTHOR]

The whole process of clamping offshore well double metal composite pipe was established, Reviewing the problems that in the oil and gas wells the double metal composite pipes frequently get plastic damage or even fracture failure when the power slips hold fast to the double metal composite pipe, the effect Eq. of contact area to tooth plate and double metal composite pipe was deduced, and based on the elastoplastic contact analysis theory, the theoretical Eq. was verified. For the double metal composite pipe stress, displacement and stress of drill tooth plate, influence of slip teeth plate on the double metal composite pipe damage was analyzed, The plastic damage law of the double metal composite pipe was obtained with the influence factor of the contact surface and the influence factor of the tooth crown width. the analysis showed that, The double metal composite pipe can be clamped and the contact area value of the tooth plate with the minimum damage are fixed. Several sets of teeth were produced, and then used to carry out experiments, indoor and field experiments have fully proved the accuracy of the result, The research work provides a better theoretical basis for optimal design of slip tooth plate.

Reduced Activation Ferritic/Martensite (RAFM) steel is a new material considered to be one of the important candidate structural materials for Tokamak fusion reactors. Plastic deformation inevitably occurs during the operation of fusion reactors due to giant unexpected loads. To ensure the structural integrity, reliable non-destructive evaluation (NDE) for RAFM steel is of great importance. Magnetic Barkhousen Noise (MBN), Magnetic Incremental Permeability (MIP) and Magnetic Flux Leakage (MFL) methods are found being effective especially for NDE of large plastic deformation in RAFM steel by authors. Its feasibility for small plastic deformation under 1%, however, is not clarified. At the same time, as mechanical damage may be caused by several times of large load, i.e., the current deformation state is possibly of complicated loading history. To clarify the influence of these factors is also very important for application of these magnetic NDE methods in practice. In view of this background, the influences of plastic deformation history on NDE signals and the feasibility of the magnetic NDE methods for relative small deformation are experimentally studied in this paper. From experimental results, it was found that the MIP and MFL signals decrease with an enlarged plastic deformation and are not significantly influenced by the plastic deformation history, while the MBN signals show significantly different tendency for specimen of different loading history. To understand the mechanism, micro-structure analyses and magnetic domain observations are conducted by using the EBSD and the magnetic powder-pattern method. Observation results reveal that the pinning effect of the micro defects prevents the movement of magnetic domain walls and perturbs the signals of magnetic NDE methods, especially on the MBN signals. These results show that the MIP and MFL method are more suitable for evaluation of plastic deformation in RAFM steel from practical application point of view. [ABSTRACT FROM AUTHOR]

The wellbore stability of soft mudstone formation is strongly affected by thermal and hydraulic loadings due to its low strength and high plasticity under high-pressure and high-temperature conditions. A nonlinear coupled thermal- hydraulic-mechanical (THM) model was proposed to evaluate the influence of temperature and fluid factors on wellbore stability located in deep and complex soft mudstone formations. The evolution of near-wellbore formation strength and permeability was quantitatively described by introducing a plastic damage variable in the THM model. The influence of mud pressure and temperature on the stress and plastic damage distribution near the wellbore zone was analyzed using the THM model. The accuracy of the models was verified by comparing the radial/hoop stress results with those from classical thermopore elastic theory. Results show that the plastic failure of the near-wellbore zone and wellbore stability are mainly controlled by the coupling effects of thermal and hydraulic deformations of the soft mudstone. Specifically, the size of the damage zone is enlarged by 2.7 mm when the mud temperature increases by 40 °C. By contrast, the damage scale is reduced by 1.7 mm as the temperature decrease by 40 °C due to the compaction effects in the nearwellbore region. The mechanical behavior of the soft mudstone wellbore is time dependent, that is, with the increase in time, the damage gradually extends to the periphery of the wellbore after the plastic equilibrium state near the wellbore is reached. This study provides a THM modelling framework for understanding the mechanism of soft mudstone wellbore instability and formulating corresponding preventive measures. [ABSTRACT FROM AUTHOR]

The ensilage of total mixed ration (TMR) is a technology designed to help farmers with limitations to provide a balanced diet for their herds. Our aim was to evaluate the conservation of TMR ensiled in round bales with or without holes in the wrapping plastic film. Eight round bales of a corn silage-based TMR of 1,000 kg (370 kg DM/m3) were prepared. Ten days (d) after ensiling, four bales were randomly punctured with two holes of 25 cm2 each in opposite sides of the bale. The temperature in the center of the bales was recorded during the storage using dataloggers. After 60 d of storage, bales were weighted to assess dry matter (DM) recovery. Silages were sampled for measuring DM content, chemical composition, pH, lactic acid, and microbial counts. The temperature of the sliced bale face was assessed by infrared thermography. The holes in the plastic affected the DM content, DM recovery, and pH, whereas lactic acid, microbial counts, and temperature were not affected by treatments. The holes in the sealing plastic film should be avoided. However, holes of 25 cm2 each were not capable of causing expressive losses in TMR silage stored in 1,000 kg bales. [ABSTRACT FROM AUTHOR]

Highlights • A method for simulation of spatial variability of gravity dams was established. • Mean value of the tensile strength has a great influence on the plastic damage. • Research results can be used as a reference for gravity dams with similar profiles. Abstract A method to simulate the random field of the strength parameters of gravity dams considering their spatial variability based on the theory of random fields and the autocorrelation function is proposed. Taking a gravity dam project as an example, the elastic modulus and tensile strength are selected as random variables and the corresponding random fields are generated. Based on the concrete damage plasticity (CDP) model, the effects of the spatial variability of parameters on the dynamic response characteristics of gravity dams are expressed from the standpoints of damage development, residual displacement, and energy dissipation. The impacts of the mean value, coefficients of variation, autocorrelation distance, realizations of the tensile strength random field, and seismic inputs on the structural damage are also investigated. It is found that the spatial variability of parameters, especially the tensile strength, has a great influence on the dynamic damage of gravity dams, and that increasing the mean value of the tensile strength can improve their seismic performance. [ABSTRACT FROM AUTHOR]

Highlights • The plastic deformation of the crystal firstly appears around the void, that is, the slip systems around the void start first. • The single crystal with the hard orientation and the bicrystal with the larger misorientation between the two grains are more difficult to slip. • The slip systems in crystal with a circular pore are more prone to start than with an elliptical pore. • The loading direction that is vertical to the grain boundary is more conducive to the slip of the crystal and the growth of the pore. Abstract Additive manufacturing technology is a novel approach for the development of the modern industry. Additive manufactured aluminium (Al) becomes the hotspot of current research in order to achieve the high-precision products. However, the additive manufactured Al parts easily generate void defects due to the poor fluidity and low density of the materials, which in turn affects the mechanical properties. This paper studies the damage behavior of additive manufactured Al parts with void defects under tensile load in a mesoscale by using a two-dimensional rate-dependent crystal plasticity theory. The stress-strain curves and the plastic damages of single crystal and bicrystal with void defects are determined with different combinations of crystal orientations and loading conditions. It is found that the mechanical properties of additive manufactured aluminium severely depend on the crystal orientations and shapes of void defects. [ABSTRACT FROM AUTHOR]

Nine types of tree-pool joints designed to plant large trees on building structures were proposed in this study. Solid finite element model considering plastic damage constitutive relationship for the tree-pool joints were built using ABAQUS software platform. Based on comparative analysis of six different mesh generation methods of the 3D tree-pool joint model, an optimized mesh generation method was determined and verified considering both the calculation time and accuracy. The mechanical behavior of the nine tree-pool joints, such as peak tension/compression stress, hysteretic energy dissipation performance, plastic damage performance and corresponding crack development process, were studied in detail under horizontal and vertical loads. The results show that the tree-pool joints with steel strengthened form and composite strengthened form have superior horizontal and vertical bearing capacity. Similarly, they also have stable hysteretic energy dissipation performance, minimal plastic damage and crack development relatively in vertical ultimate load. However, the tree-pool joints with other strengthened forms, such as forms of inner-beam and inner-beam combined with ring bracket, show poor mechanical properties. Although there is a certain degree of performance improvement for these tree-pool joints relative to non-strengthened joints, narrow hysteretic curves, apparent strength/stiffness degradation characteristics, extensive material damage and crack development can be found. Results of this paper do shine some lights on how to design reasonable and reliable tree-pool joints in building structures. [ABSTRACT FROM AUTHOR]

Buckling restrained braces have dual functions of both providing lateral stiffness and improving seismic performance under earthquake in an economic and flexible way. To strengthen the performance of slab-column system, chevron buckling restrained braces were applied at slab-column connections. A quasi-static test on a one-half scale, one-bay and one-story model was conducted to evaluate the seismic performance of the slab-column frame with chevron buckling restrained braces. The results show that the cracks are mainly located in the range of 1/3 slab length around both columns and lower 1/3 of the column height, which are also the most severely damaged locations. The specimen still has bearing capacity when the deflection angle reaches 1/50. The model finally fails due to the failure of tensile brace in the loading process of deflection angle 1/30 (50mm displacement). Adopting ABAQUS finite element method, skeleton curves and plastic damage of slab-column structures with and without chevron buckling restrained braces were compared. According to the experiment and FEM simulation results, the chevron buckling restrained braces can effectively increase the lateral bearing capacity and lateral stiffness of slab-column structure, which should be considered in design and strengthening of slab-column structure. [ABSTRACT FROM AUTHOR]

• In this research, the infrared radiation observation experiments of sandstone under biaxial loading and different lateral stresses were carried out. • Based on the effective stress and plastic strain, the plastic and damage models are established respectively. • Proposed three-dimensional plastic damage constitutive model of loaded sandstone based on infrared radiation. • The stress prediction of sandstone during biaxial loading is realized through the secondary development of a finite element software subroutine. The significant increase in energy demand will inevitably boost the exploitation of natural resources. The exploitation of resources including coal, oil, geothermal, natural gas, shale gas, and other energy has to be extracted with deep mining to fulfill the industry energy demand. With the increase of mining depth and the utilization of deep rock mass, the problem of high ground stress has become increasingly prominent. During high ground stress conditions, the mechanical behavior of hard rock will change significantly. Constructing a reasonable stress–strain damage constitutive model of hard rock is the basis for the design of a resource mining construction scheme, numerical simulation analysis, more accurate acquisition of rock mechanical characteristics, and evaluation of engineering rock stability. This is very crucial that needs to be addressed in a better way to solve the scientific problems of rock engineering. In this research, the infrared radiation observation experiments of sandstone biaxial under different lateral stresses are carried out. It is found that the infrared radiation energy has a near power function relationship with the effective stress in loading and fracture process. The quantitative characterization method of infrared radiation of the first invariant of stress and the second invariant of deviator stress is established. The cumulative high-temperature point scale factor amplitude is proposed to characterize the plastic volumetric strain of sandstone. Based on the effective stress and plastic strain, the plastic and damage models are established respectively. The three-dimensional plastic damage constitutive model of loaded sandstone based on infrared radiation is constructed. The model has clear input parameters having physical significance, and the compaction stage of sandstone is considered. The stress prediction of sandstone during biaxial loading is realized through the secondary development of a finite element software subroutine. The research results can lay a theoretical foundation for the analysis and evaluation of the mechanical characteristics of hard rock in the process of deep energy exploitation. [ABSTRACT FROM AUTHOR]

In this paper, some simple stress-strain relationships of the concrete material recommended in relevant Codes are appropriately simplified, then the damage factors of the simplified plastic damage constitutive model is determined based on Sidiroff’s energy equivalence principle. Mechanical characteristics of the concrete material under the simple tension or compression are analyzed by Finite element method. Through the comparison of numerical analysis results and Code constitutive relations, the damage factors of the simplified plastic damage constitutive model is verified. The unreinforced concrete beam static tests by Petersson is simulation analyzed by the nonlinear finite element method and plastic damage constitutive model. The effect of the unit size and the different linear softening constitutive relation on the analysis results are considered. The results show that there is no obvious size effect on the plastic damage analysis results based on fracture cracking criterion, the results of the bilinear softening constitutive analysis have good accuracy, and the form of softening constitutive relation has a great influence on the result. [ABSTRACT FROM AUTHOR]