Compressive Crack Research Articles

Limestone calcined clay-based engineered cementitious composites (LC3-ECC) with recycled sand: Macro performance and micro mechanism

Limestone calcined clay cement (LC3) contributes to the development of sustainable cement-based materials. In this study, LC3 was combined with fly ash (FA) and recycled sands (RS) to develop engineered cementitious composites (ECC). Three FA/LC3 ratios (1, 1.5, and 2) and three RS particle sizes (0.15–1.18 mm, 0.15–2.36 mm, and 0.15–4.75 mm) were studied. Compared to ordinary Portland cement (OPC)-based paste, the LC3 substitution resulted in higher hydration heat and hydration degree, forming more hydration products. Although LC3 substitution produced a slightly lower compressive strength, a more robust tensile strain-hardening behavior than OPC-based ECC was achieved. The increasing FA/LC3 ratios gradually reduced compressive strength, tensile strength, and crack width. The multiple cracking behavior with controlled widths of LC3-based ECC was found to be more stable, which could be traced to the superior properties of fiber/matrix interfacial transition zone. In addition, utilizing RS as fine aggregates with various particle sizes could achieve an ultra-high tensile strain capacity exceeding 8 % for LC3-based ECC, thereby enhancing its utilization efficiency. Furthermore, the utilization of LC3 resulted in 28.6–47.1 % and 6.6–22.0 % reductions in carbon emission and embodied energy, respectively. The combination of LC3 and RS holds a promising approach to developing sustainable ECC with desirable mechanical performance.

Sustainable and mechanical properties of Engineered Cementitious Composites with biochar: Integrating micro- and macro-mechanical insight

Engineered Cementitious Composites (ECC) are ductile, strain-hardening cementitious composites with a tightly controlled crack opening profile. A significant concern in the development and application of ECC is its high carbon emissions associated with high cement content consumption. As an emerging green additive, biochar can significantly cut down on the carbon emission of concrete products. However, research that integrates micro- and macro-mechanical insights with biochar incorporation is limited. In this study, micro-mechanical tools indicated that a certain amount of substitution biochar could enhance the tensile properties of ECC. The study assessed various properties including compressive strength, porosity, density, tensile performance, crack pattern, sustainability and cost of ECC with different biochar proportions. The findings showed that incorporating 10 %–20 % biochar effectively increased the tensile strain capacity and decreased the crack opening width in ECC materials. This improvement can be attributed to the introduction of finer biochar particles (≤75 μm) at the fiber/matrix interfacial transition zone, which alters the fiber-bridging force by reducing the chemical and frictional bond strength between the fiber and matrix, as revealed by micro-mechanical tests and microstructural inspection. Moreover, the utilization of biochar contributes to reducing the carbon emission of ECC, enhancing sustainability while maintaining a ∼10 % minimal reduction in compressive strength. Overall, this study introduces a novel approach for reusing low-carbon biomass waste in the production of building materials, offering potential advantages in micro- and macro-mechanical performance, cost-effectiveness, and environmental sustainability.

Crack propagation behavior and failure prediction of rocks with non-parallel conjugate flaws: Insights from the perspective of acoustic emission and DIC

Rock-like containing non-parallel conjugate flaws specimens (NPCFS) were prepared and uniaxial compression crack propagation tests were conducted employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that: the angle of conjugate unilateral cracks increases, the average load-bearing capacity of the rock rises. Dominant frequencies from different conjugate defect angles exhibit distinct bimodal characteristics (low-frequency: 80–140 kHz, intermediate-frequency: 260–320 kHz). The concept of AE dominant frequency ratio β is proposed and introduced to quantify the strength of macro-scale failure of the specimens. The AE multiparameter is proposed to predict the failure load, and the mean value of failure load is predicted to be in the range of 86–93 % (failure load), the prediction interval of Ib value is in the range of 95–99 %, the prediction interval of critical slowing down variance value is in the range of 90–95 %, while the prediction interval of autocorrelation coefficient is in the range of 83–90 %. A favorable correlation was observed between AE events in NPCFS and surface deformations observed through DIC technology. Both ends of the conjugate flaw cannot propagate simultaneously; once one extends, the other ceases further expansion, forming a primary failure line that propagates towards the direction of the primary compressive stress.

Phase field numerical strategies for positive volumetric strain energy fractures

AbstractA reasonable crack driving force is the key to preventing compression cracks and eliminating unrealistic crack propagation in phase field fracture analysis. Thus, examining the roles of volumetric strain energy (VSE) and deviatoric strain energy (DSE) in influencing crack propagation is necessary. This paper presents a comprehensive analysis of the following four different approaches to energy decomposition‐driven crack propagation: the positive volumetric strain energy method (VSEM), deviatoric strain energy method (DSEM), volumetric‐deviatoric strain energy method (VDSEM), and no decomposition method (NM). All of the strain energy is involved in the development of the crack propagation. The following four examples are investigated: two benchmark single‐side notched examples, a complex crack containing a hole example, and a crack coalescence in an asymmetric double notch example. The VSEM's numerical findings align with literature and experimental observations, confirming that positive VSE rather than DSE promotes crack propagation.

Research on the strength influence and crack evolution law of layered backfill based on macro and meso mechanical response

This article analyzes the effects of inclined angle (IA), filling times (FTs) and cement tailings ratio (CTR) on the uniaxial compressive strength (UCS) and crack development law of layered cemented backfill (LCB) using various research methods, including indoor experiments, numerical simulation, and computed tomography (CT) scanning. The research shows: (1) In the indoor experiments, it was observed that increasing the IA, increasing the number of FTs, and decreasing the CTR had a significant weakening effect on the UCS of the specimens. The greater the IA, the more pronounced the separation and dislocation of the layered contact surface, resulting in a significant increase in macroscopic cracks at the bottom. As the FTs increases, the center of gravity of the failure of the LCB gradually moves downwards. This causes the damage and failure time to advance, and the peak stress to change from one main crack to multiple main cracks. (2) During the numerical simulation, compressive stress accumulates and increases around the pores in the layered contact surface. Microcrack aggregation occurs on the contact surface, and downward expansion and extension. The peak strain energy decreases as the IA increases with the FTs. The number of shear cracks increased more at 20° to 30° than at 0° to 20°. The strain energy of the 0° specimen is the highest, while that of the 30° specimen is the lowest. (3) The CT scan shows that the LCB is affected by stress conduction hysteresis. When the bottom backfill is in the stage of crack evolution, the top backfill is in the stage of compaction.When the LCB reaches the peak stress, both the bottom and middle layers of the backfill lose load-bearing capacity, and the top layer of the backfill has no cracks. This paper provides reference value and research ideas for the destruction of backfill that contain layered defective structures.

Experimental evaluation of bonded/unbonded prestressed precast concrete joints under repetitive loading scenarios: Seismic performance and retrofit intervention

Recently, demands for mitigating structural damage and post-earthquake repair costs have spurred considerable research on prestressed precast frames. In this study, quasi-static tests were conducted on bonded and unbonded prestressed precast beam-column joints (BPPJs and UPPJs) to investigate the influences of bonded/unbonded post-tensioned (PT) strands, evaluate the performance of BPPJs under repeated loading, and verify the effectiveness of post-earthquake retrofitting with external buckling-restrained rods (BRRs). Additionally, the difference between the bonded and unbonded joints was further revealed from the perspective of the tensile forces of the strands at the beamcolumn interface. Test results showed that compared with the UPPJ, the BPPJ exhibited superior performance in terms of lateral stiffness, lateral resistance, and energy dissipating capacity, with a 76.4 % increase in the load-bearing capacity. The compressive zone at the beam end was also deeper in the BPPJ, accompanied by a denser distribution of compressive cracks in the concrete. Furthermore, the bond between the strands and grouting material in the duct accelerated the increase in the tensile forces of the strands at the interface, resulting in considerably more prestress loss in the BPPJ after the tests, which was 120.0 % greater than that in the UPPJ. Under repetitive loading scenarios, although the yielding resistance of the BPPJ decreased by 35.0 % compared with that of the first loading owing to the reduced tensile forces in the strands, relatively minor variations in the load-bearing capacity and energy dissipation were observed. After retrofitting with BRRs, the BPPJ exhibited substantial enhancements in both lateral stiffness and resistance, validating the effectiveness of post-earthquake retrofitting with BRRs.

Experimental evaluation of the synergistic effect of calcium precursor dosage and bacterial strain interactions on the biogenic healing potential of self-healing cement mortar

This study investigates the microbially induced calcium carbonate precipitation (MICP) in repair mortar, focusing on the impact of calcium precursor dosage and bacterial strain selection. C6H10CaO6·xH2O and (CH3COO)2Ca·xH2O were used as calcium precursors at dosages of 0.1, 0.25, and 0.4 M with Bacillus subtilis VEB4, Priestia megaterium TSB16, and Halobacillus halophilus MCC2188 microbes. Quantitative assessment of precipitate and optimization of precursor dosages were conducted before making mortar cube specimens of size 70.6 × 70.6 × 70.6 mm with bacterial spores and nutrients immobilized in Modified Expanded Perlite. Cracked cube specimens underwent automated wet-dry cycles of 12 h daily for 60 days to induce healing. Comparative analysis of biomortar specimens showed P. megaterium as the most effective in compressive strength recovery (up to 89.33%) and crack healing with a maximum healed crack width of 0.64 mm, followed by B. subtilis with significant CSR improvements. H. halophilus, less efficient in non-saline conditions, healed cracks up to 0.48 mm. Calcium lactate was considered the better calcium source choice for B. subtilis and P. megaterium strains, whereas calcium acetate improved MICP by H. halophilus. Microstructural analysis of healed precipitates collected from cracked cubes identified distinct morphology of MICP and the presence of polymorphs viz, calcite, aragonite, and vaterite. Tailored selection and dosage of calcium precursors for each strain significantly enhanced MICP and improved the quality of healing products in cracks, advancing the understanding of self-healing construction biomaterials.

Crack propagation process in double-flawed granite under compression using digital image correlation method and numerical simulation

The existence of flaws seriously weakens the rock strength, directly affects the crack expansion morphology, and indirectly affects the slope stability. In this study, uniaxial compression tests were carried out on double-flawed granite to investigate the effects of flaw angle on its compressive strength and crack coalescence based on DIC technology and PFC2D numerical simulation. The result indicates that the UCS values of flawed specimens at angles of 15°, 30°, 45°, and 60° are approximately 25.5–51.7% lower than that of the intact specimen. The failure strength of the double-flawed sample increases with the increase of flaw inclination angle, and the fracture morphology shifts from no expansion to split expansion. When the flaw tip strain of each flaw sample exceeded 0.6%, the stress concentration was generated at the flaw tip, and the sample began to appear macroscopic large cracks. DIC technique can well observe the crack initiation and propagation process, recording inclined shear strain bands at flaw tips, tensile strain bands in the middle of flaws, and tensile shear O-shaped strain ring in rock bridge areas. Numerical simulations using PFC2D software were carried out and showed a good agreement with the physical results. In addition, the effect of structural inclination on specimen failure strength is clearly explained by the theory of compressive damage based on the projected size of flaws. The deformation of rock mass is not a simple material deformation but is composed of material deformation and structural deformation. These experimental and numerical results enhance our understanding of crack initiation and coalescence characteristics, aiding in the analysis of rock structure stability in scenarios such as excavated underground openings, slopes, and tunneling construction, where pre-existing cracks or step-path fractures are pivotal to structural integrity.

A B-spline material point method for deformation failure mechanism of soft–hard interbedded rock

Geological hazards related to soft–hard interbedded rock are frequent in rock engineering. The material point method (MPM) is a mesh-free numerical approach specifically designed for analyzing large deformations. Notably, significant grid-crossing errors frequently arise when material points traverse the underlying grid. To investigate the failure mechanism of soft–hard interbedded rock, an enhanced MPM incorporating B-spline basis functions and Voronoi polygon discretization is developed and subsequently validated through comparisons with uniaxial compression test data and other numerical methods. The numerical results of soft–hard interbedded rock specimens associated with different soft layer dips (SLD) and confining pressures indicate that the SLD has a great effect on compressive strength and crack extension at low confining pressure. Rocks from SLD-30° to SLD-75° correspond to the “sliding failure along discontinuities” failure mode and have lower compressive strength than rocks with other SLD angles. It is also demonstrated that the propagation of cracks leads to a significant alteration in the internal stress state of the rock, and that stress concentrations at the crack tip exacerbate the development of failure surface. Furthermore, the failure mode of soft–hard interbedded rock can be categorized into four types: (1) sliding failure across multiple discontinuities, (2) tensile fracture across multiple discontinuities, (3) sliding failure along discontinuities, (4) tensile-split along discontinuities.

Quantitative assessment of correlation between compressive strength degradation and microstructural crack information in mortar deteriorated by freeze-thaw cycles

Freeze-thaw cycle (FTC) deterioration poses significant durability challenges to concrete structures. However, the detailed quantitative relationship between FTC-induced internal damage pattern development and mechanical degradation remains underexplored, limiting the accuracy of FTC deterioration assessments. This study aims to provide a comprehensive analysis of microstructural damage progression and its quantitative relationship with mechanical degradation in mortar specimens throughout FTC process. Through establishing an experimental setup applied to specimens at two scales and facilitated by micro-computed tomography (micro-CT), this research concurrently evaluates the microstructural damage progression, mechanical degradation, and expansion of the specimens under various FTC severity levels. The quantification of multiple crack indices reveals a stronger correlation between compressive strength reduction and crack ingression than with increases in crack quantity or width. The findings further highlight the imperative to incorporate both expansion-induced damage and time-dependent fatigue damage in evaluating FTC deterioration, thus laying a foundation for refining FTC prediction models.

Research on triaxial compressive mechanical properties and damage constructive model of post-thawing double-fractured quasi-sandstones with different angles

Joints and fractures lead to different failure mechanisms in rock masses under different environments. The mechanical properties and failure mechanisms of rocks with fissures are key problems in rock mass engineering. Parallel double-fracture quasi-sandstone specimens with different dip angles were prepared and subjected to triaxial compression tests after a single freeze-thaw cycle. Pore development, crack propagation, damage evolution, and failure characteristics were analysed. Combined with the strength distribution theory of microelements and the static elastic modulus theory, a damage constitutive model of double-fracture quasi-sandstone under freeze-thaw cycles and loads was established. This study explored the pore development, fracture propagation, damage evolution, and failure characteristics of fractured sandstone after thawing. The results showed that the compression wave velocity of the thawed specimens decreased, the nuclear magnetic resonance (NMR) T2 curve shifted to the right, and the frost heave force promoted the development of the internal porosity in the specimens. With an increase in the crack dip angle, peak stress, expansion stress, cohesion and internal friction angle, the specimen showed a ‘U’ shaped change trend, compression cracks, and rock bridge penetration rate after failure decreased, and mixed failure of tension and shear gradually changed into shear failure. When the dip angles were 30° and 60°, the double fractured quasi-sandstone had larger total damage and more obvious brittle failure characteristics.

Force model of ultrasonic empowered minimum quantity lubrication grinding CFRP

As a weight-reducing material in aerospace applications, carbon fiber reinforced polymer (CFRP) requires precision grinding to ensure the accuracy and assembly of mating positioning surfaces. However, achieving low-damage machining of CFRPs remains challenging. Flood cooling reduces the mechanical properties, while dry grinding deteriorates the surface integrity, making minimum quantity lubrication (MQL) a viable alternative. However, nanolubricants struggle to penetrate the grinding area due to gas barrier obstruction. Consequently, a new CFRP grinding approach using multiangle 2D ultrasonic vibration-empowered nanolubricant MQL was proposed. An analytical force model is crucial for optimizing machining strategies and adjusting parameters. The aim is to reveal grinding mechanics and develop a force model under different ultrasonic and lubrication-cooling conditions. First, a uniform random fiber distribution model and a grinding wheel model were established, and the mechanical properties of the interface were predicted. Then, the intermittent grinding behavior and dynamic stiffnesses of the multiangle 2D ultrasonic vibration-assisted grinding (UVAG) system were investigated based on the geometric kinematics of the grains' trajectory. Furthermore, based on the deformation deflection curve, bending fracture force models for 45°, 90°, and 135° fibers were established with different contact and boundary conditions. The material removal mechanisms of shear and tension-compression buckling in 0° CFRP grinding were revealed, and an elliptical contact normal force model was established. The interlayer shear in 45° CFRPs was analyzed. The longitudinal compressive matrix cracking and fiber shear fracture in the 90° CFRPs were elucidated. Fiber microbuckling and fiber bundle removal of 135° CFRPs were investigated. Finally, grinding force models with different fiber orientation angles (FOAs) were interconnected and experimentally assessed. Experimental assessments demonstrated that the grinding force model has acceptable estimation error and effectively captures the mechanics of CFRPs with different FOAs.

Conventional triaxial loading and unloading test and PFC numerical simulation of rock with single fracture

Take the metamorphic sandstone as the reference object, by making rock like samples with fractures, the conventional triaxial loading and unloading test and PFC numerical simulation of rock like sample with single fracture were conducted, and the effects of the loading path, inclined angle of fracture, axial stress level during unloading, initial confining pressure during unloading on the compressive strength, peak strain and crack propagation evolution of the samples were considered. The compressive strength of the specimen under triaxial unloading is smaller than that under triaxial loading. The peak strain of the specimen under triaxial unloading is also smaller than that under triaxial loading. The specimen is more prone to brittle failure. When the axial stress level is the same during unloading, with the increase of the initial confining pressure during unloading, the difference of the compressive strength of the specimens with different inclined angles of fracture gradually decreases. Under the condition of uniaxial compression and triaxial compression, the failure of all specimens is tensile failure, and the shear failure is the main one during unloading.

Cyclic response sensitivity of coupled composite plate shear walls/concrete filled (CC-PSWs/CF)

A composite plate shear wall/concrete filled system, also known as “SpeedCore”, is a new lateral force-resisting system used as core walls in mid- and high-rise buildings. This composite wall system eliminates some of the conventional construction requirements in reinforced concrete core walls, resulting in faster construction and cost savings. This paper aims to identify factors affecting the cyclic response and limit states of coupled composite plate shear walls/concrete filled (CC-PSWs/CF). A statistical sensitivity analysis is performed using the Design of Experiments method. Finite element models of walls are developed and analyzed under cyclic loading. The accuracy of the finite element simulation is validated by using results from past experimental and numerical studies. The sensitivity analysis evaluates the effect of eight factors and their interactions on the lateral response of CC-PSWs/CF systems. Ten response parameters are considered, including the system initial stiffness, the onset of steel yielding in coupling beams and walls, the onset of compressive cracking of concrete in coupling beams and walls, coupling beam first and last steel yielding and plastic hinge in concrete, and the system lateral load capacity. The results show that the wall length is the most influential factor affecting all the response variables. The wall steel area ratio, steel yield strength, concrete compressive strength, wall thickness, and the coupling beam steel ratio and span-to-depth ratio affect at least four response variables.

Study on meso-deformation and failure mechanism of rock mass with micro-cracks under freeze-thaw loading

The long-term freeze-thaw effect leads to the development of rock fractures and strength degradation in cold region engineering construction, which poses a serious challenge to the stability of the project. In this paper, the microscopic model of sandstone freeze-thaw cycles was established using a particle flow code (PFC2D). Through numerical simulation, the variation law of mechanical properties of rock mass with micro-cracks is systematically studied from the aspects of displacement, crack development, strain and strength. The results show that: (i) The freeze-thaw loading displacement is concentrated on both sides of the initial micro-cracks, and the crack development is not controlled by it. When the number of freeze-thaw cycles is greater than 17, the displacement and crack development are significant. The crack increases with the increase of the crack distance ratio. (ii) When the number of freeze-thaw cycles is less than 15, the compressive crack develops at the end of the initial micro-crack, and the development is controlled by it. When the number of freeze-thaw cycles is greater than 21, the crack increases sharply, and the development is no longer controlled by the initial micro-cracks. When the number of freeze-thaw cycles is less than 15, the damage strain shows minimal variation but decreases sharply with the increase of freeze-thaw cycles. (iii) Under each crack distance ratio, the strength changes in three stages: when the number of freeze-thaw cycles is less than 15, the strength changes little, and the strength decreases sharply with the increase of freeze-thaw cycles. With the increase of the crack distance ratio, it increases first and then decreases. And it is more significant when the number of freeze-thaw cycles is greater than 17. The research results can provide theoretical support for the influence and evaluation of rock freeze-thaw action in cold regions.

Tensile and compressive properties of bamboo scrimber under different temperature conditions

AbstractBamboo scrimber demonstrates vulnerability to environmental temperature fluctuations, such as exposure to cold or fire, when deployed in structural applications. Consequently, its mechanical properties can substantially diverge from the intended design values under varying thermal conditions. This study aims to study the tensile and compressive properties of bamboo scrimber under different temperatures to provide data support for studying bamboo scrimber under low and high temperatures. The compressive properties of bamboo scrimber under temperatures ranging from −30°C to 250°C and the tensile properties under −20°C to 250°C were determined by a series of tests with a total of 125 specimens. The results show that the mass loss of bamboo scrimber increases gradually with the increase in temperature, and the increasing trend intensifies after 120°C. With the increase of temperature, the failure mode of the specimens under compression changes from the bottom compression cracking damage to the local destabilization of longitudinal fibers, while the tensile damage modes aren't influenced by temperature, and both “straight‐line” and “folded‐line” types of damage modes occur at different temperatures. The tensile and compressive strengths and elastic modulus of the specimens decreased with the increase in temperature, and the strength was more susceptible to the temperature than the elastic modulus: a rise in temperature from 20°C to 250°C resulted in a reduction of compressive strength and tensile strength by 80.80% and 84.11%, respectively, the compressive modulus and tensile modulus experienced decreases of 49.51% and 53.28%. Furthermore, equations of temperature influence coefficients of strength and elastic modulus were established based on the test results.Highlights Bamboo scrimber's mechanical properties under different temperatures are studied. Tendency and explanation of temperature influence coefficients are analyzed. Temperature coefficient equations for strength and elastic modulus are proposed.

Mechanical Characterization Potentials of Aluminide Diffusion Coatings on Molybdenum Substrates

A mechanical test strategy is designed to determine the resistance of protective intermetallic aluminum layers on molybdenum substrates. Performing mechanical experiments, such as compression, four‐point bending and indentation tests, the specific failure behavior and a potential impact of observed phase transformations within the interface zone on the structural integrity and adhesion strength are examined. Herein, the applied test structure aims at the description of damage characteristics and critical deformation states regarding the type of loading. In this respect, it focuses on delamination behavior under compressive load and crack channeling due to bending stress. The analysis of the mechanical experiments is supported by various measurement techniques, including 3D camera equipment (GOM) and an acoustic emission (AE) analysis system. In particular, the application of the AE technique in this work provides a helpful contribution to the detection of delamination failure and the development of multiple crack channeling. Considering the successfully applied experimental approaches, it is assumed that more complex coating‐base material combinations can be characterized this way with respect to preceding annealing effects and the thereby influenced load capacity of thin films under different loading types.

Effects of autogenous shrinkage microcracks on UHPC: Insights from a machine learning based crack quantification approach

Owing to its high pozzolanic reactivity and contribution to packing density, silica fume is almost an indispensable part of UHPC, but it brings potentially serious problem of high autogenous shrinkage. Nanocellulose (NC) is very effective in controlling shrinkage but would also result in different microstructure, whose impact is not clear. This study aims to explore the compensatory effect of NC on high shrinkage of UHPC. An image process method based on machine learning and stereological methods is proposed to quantify the autogenous shrinkage induced microcracks. Results show that the addition of NC reduces the crack width and area by 57.45∼70.55% and 63.2–83.8%, respectively. The MIP analysis reveals that the incorporation of NC introduces a larger proportion of pores. In terms of mechanical properties, the higher content of pores brought by NC has a negative effect on compressive strength, however, the enhancement of flexural strength by NC can reach 66.02%. Excellent correlations between 0 and 50 nm porosity and compressive strength, crack density and flexural strength are observed with R2 of 0.94 and 0.98 respectively. This study provides a theoretical basis for the potential control of porosity and cracks of UHPC to meet the different mechanical performance requirements of components.

High‐Strength Wear‐Resistant Cu/Tungsten Carbide/Diamond Composites Fabricated by Powder Metallurgy

Copper‐based diamond composites are widely used for thermal management and wear‐resistant materials. In this work, Cu/diamond, Cu/tungsten carbide (WC)/diamond, and Cu–0.92Cr/WC/diamond composites are fabricated by high‐energy ball milling and rapid hot‐pressing sintering. Physical characteristics, compressive strength, and tribological properties of the studied composites are investigated. The compressive strength of Cu/7wt%WC/diamond composites is 102% higher than the Cu/diamond composites, reaching 415 MPa. Compression fractures extend from the interface due to compression cracks, consistent with the compression curves from molecular dynamics (MD) simulations. The crack propagates from the interface during the compression experiment, which is consistent with the result of MD simulation. The Cu/7wt%WC/diamond composites exhibit a wear rate of 0.6 × 10−6 mm3 (N m)−1 and a friction coefficient of 0.37 at 50 N. The addition of WC and diamond improves the compressive strength and wear resistance. These findings are helpful in the development of copper composites with high compression strength and wear resistance.

A comparative study of corrosion mechanisms in recrystallized and stress-relieved Zircaloy-4 by 3D-FIB tomography and ACOM-TEM

The corrosion behavior of recrystallized annealed (RXA) and stress-relieved annealed (SRA) Zircaloy-4 was assessed in 360 ℃ lithiated water for 400 days. SRA Zircaloy-4 with localized corrosion sites below the oxide/metal interface exhibits a much faster out-of-reactor corrosion rate than RXA Zircaloy-4. High-density dislocations can enhance the diffusion of oxygen anions along dislocations, promoting the advancement of corrosive reactions and forming localized corrosion sites. Such a mechanism leads to a less uniform crystallography orientation of monoclinic ZrO2 grains at the oxide/metal interface of SRA Zircaloy-4 compared to its RXA counterpart, resulting in higher compressive stress and oxide cracking rates.