Shear Strain Research Articles

The effect of Fe solute atom on interface structure and deformation behavior of Cu/FexNi1-x layered composites by molecular dynamics

Molecular dynamics investigated the effect of Fe solute atom on interface structure and deformation behavior of Cu/FexNi1-x layered composites. Ultimate stress first increases, then decreases, and then increases again with the increase of Fe content. When Fe content is between 20 % and 30 %, ultimate stress reaches the maximum value, which is 15.2 % higher than that of Cu/Ni. As the Fe content increases, stress concentration region on interface shifts from Cu layer to FexNi1-x layer, then to Cu layer, initial dislocation nucleation source on interface transfers from triangular node on Cu side to misfit dislocation line on FexNi1-x side, then to strip region on Cu side, and plastic deformation mechanism of FexNi1-x layer changes from slip of leading and trailing dislocations to slip of partial dislocations, then to slip of perfect dislocations. When Fe content is low, dislocation density rapidly increases to its peak, then decreases, and finally fluctuates around certain value, especially in the Fe30Ni70 layer where the dislocation density decreases to very low value, and interface morphology presents wavy. However, when Fe content is high, dislocation density slowly increases to its peak and then fluctuates around the peak, and interface morphology presents flat. Shear strain width of interface region decreases as Fe content increases, which indicates the interface of Cu/FexNi1-x with low Fe content has good plastic harmonized deformation ability.

Microstructural evolution and phase transformation of cansas 3303 SiC fibers during thermal shock at 1200 °C

A self-built automatic platform was built to evaluate the thermal shock performances of Cansas-III SiC fibers at 1200 °C in air up to 500 cycles, the corresponding oxidation and damage mechanisms were then revealed. The results showed that oxide scale was formed during thermal shock with a thickness of about 1 μm, the core was not oxidized via its protection. The fiber roughness increased before 100 cycles due to the decomposition of the amorphous SiCxOy phase, and then decreased as the formation of oxide scale. Within Cansas-III SiC fibers, structural defects of free carbon increased as the increasing ID/IG values, in addition, the TO peak shifted to the left, which both demonstrated that the relative movements occurred among SiC grains and residual stresses were then emerged. To clarify the axis and radial cracking of the oxide scale, a modified formulation considering nonzero shear strain components was then proposed to calculate the related residual stresses. The peeling and cracking of the oxide scale was ascribed to the residual stresses of GPa level among SiC grains and the thermal expansion mismatch between the oxide scale and the core.

Bone healing under different lay-up configuration of carbon fiber-reinforced PEEK composite plates.

Secondary healing of fractured bones requires an application of an appropriate fixator. In general, steel or titanium devices are used mostly. However, in recent years, composite structures arise as an attractive alternative due to high strength to weight ratio and other advantages like, for example, radiolucency. According to Food and Drug Administration (FDA), the only unidirectionally reinforced composite allowed to be implanted in human bodies is carbon fiber (CF)-reinforced poly-ether-ether-ketone (PEEK). In this work, the healing process of long bone assembled with CF/PEEK plates with cross- and angle-ply lay-up configurations is studied in the framework of finite element method. The healing is simulated by making use of the mechanoregulation model basing on the Prendergast theory. Cells transformation is determined by the octahedral shear strain and interstitial fluid velocity. The process runs iteratively assuming single load cycle each day. The fracture is subjected to axial and transverse forces. In the computations, the Abaqus program is used. It is shown that the angle-ply lamination scheme of CF/PEEK composite seems to provide better conditions for the transformation of the soft callus into the bone tissue.

Microtremor Analysis to Identify Fissure Vulnerable Zones in Demak, Central Java, Indonesia

Demak Regency, located in Central Java, Indonesia stands out among the regencies for its rapid development and regional growth, leading to a significant reliance on groundwater. This is thought to be caused by low precipitation and the geological characteristics of Demak Regency, which is mostly located on alluvial plains. To address these concerns, this study aimed to pinpoint regions vulnerable to ground fractures resulting from excessive groundwater extraction compounded by seismic activity. The research encompassed 191 locations, including 177 single station microtremor measurement points and 14 array microtremor measurement points. Single station microtremor measurements utilized the Horizontal to Vertical Spectral Ratio (HVSR) method, while array measurements employed the Spatial Autocorrelation (SPAC) method. Ground shear strain values spanning from 32.12 × 10-6 - 96.39 × 10-6. Notably, areas exhibiting heightened values are concentrated in Wonosalam Subdistrict and the Southwest of Karangtengah Subdistrict. The morphology of the bedrock within the study area tends to mirror the sedimentary layer's thickness, reflecting relatively minimal surface height discrepancies at the measurement points. Vulnerability to fissures resulting from excessive groundwater extraction and seismic activity is concentrated on the north side of Wonosalam District, the eastern sector of Demak District, and a small section of Mijen District.

Application of hybridized ensemble learning and equilibrium optimization in estimating damping ratios of municipal solid waste

The dynamic analysis of municipal solid waste (MSW) is essential for optimizing landfills and advancing sustainable development goals. Assessing damping ratio (D), a critical dynamic parameter, under laboratory conditions is costly and time-consuming, requiring specialized equipment and expertise. To streamline this process, this research leveraged several novel ensemble machine learning models integrated with the equilibrium optimizer algorithm (EOA) for the predictive analysis of damping characteristics. Data were gathered from 153 cyclic triaxial experiments on MSW, which examined the age, shear strain, weight, frequency, and percentage of plastic content. Analysis of a correlation heatmap indicated a significant dependence of D on shear strain within the collected MSW data. Subsequently, five advanced machine learning methods—adaptive boosting (AdaBoost), gradient boosting regression tree (GBRT), extreme gradient boosting (XGBoost), random forest (RF), and cubist regression—were employed to model D in landfill structures. Among these, the GBRT-EOA model demonstrated superior performance, with a coefficient of determination (R2) of 0.898, root mean square error of 1.659, mean absolute error of 1.194, mean absolute percentage error of 0.095, and an a20-index of 0.891 for the test data. A Shapley additive explanation analysis was conducted to validate these models further, revealing the relative contributions of each studied variable to the predicted D-MSW. This holistic approach not only enhances the understanding of MSW dynamics but also aids in the efficient design and management of landfill systems.

Enhanced Radiation Efficiency by Resonant Coupling in a Large Bandwidth Magnetoelectric Antenna

AbstractMagnetoelectric (ME) antennas hold the potential for significantly advancing miniaturization in radio frequency devices due to their compact size. However, critical hurdles still remain in ME antennas including low radiation efficiency and narrow bandwidth, which prevent them from seeing widespread use. Here, by sweeping the magnetic field to reach a resonant coupling, a significant enhancement in radiation efficiency by 70.95 ± 6.4% in a broad bandwidth ME antenna with 80 MHz is achieved as well as the far‐field radiation patterns are changed compared with that via non‐resonant coupling. The enhancement depends on the relative orientation between the magnetization and surface acoustic wave propagation direction which is dominated by the symmetry of the driving field induced by shear strain. A larger enhancement occurs when the magnetic field along hard axis of Ni due to the matching helicity and larger strain compared with easy axis scenario. This work demonstrates an innovative methodology that significantly enhances the radiation and reception efficiency in ME antennas, which may provide ideas for subsequent applications in communication antennas and magnetic sensors.

Crystal Plasticity Finite Element Simulation of Grain Evolution Behavior in Aluminum Alloy Rolling.

In this study, the crystal plasticity finite element method was established by coupling the crystal plasticity and finite element method (FEM). The effect of rolling deformation and slip system of polycrystalline Al-Mg-Si aluminum alloy was investigated. The results showed that there was a pronounced heterogeneity in the stress and strain distribution of the material during cold rolling. The maximum strain and shear strain occurred at surface of the material. The smaller the grain size, the lower the strain concentration at the grain boundary. Meanwhile, a smaller strain difference existed between the grain interior and near the boundary. The rotation of grains leads to significant differences in deformation and rotation depending on their initial orientations during the rolling process. The slip system of (11-1)<-110> had a large effect on the plastic deformation, (111)<10-1> is second, and the effect of (1-11)<011> slip system on the plastic deformation is the smallest. After deformation, the grain orientation concentration was increased with deformation. Therefore, both the strength and volume fraction of texture were increased with the increase in rolling deformation. The experimental results of EBSD indicated that the large rolling reduction resulted in severe grain twisting, so the texture strength was increased. The simulation results were in close agreement with the experimental results. This study provides a theoretical basis for the rolling process, microstructure, and performance control of aluminum alloys.

Influence of corrugated/flat rolling on microstructure and tensile property of coarse-grained AZ31–0.25Ca cast alloy

Novel corrugated rolling technology (CR) and conventional flat rolling (FR) were employed for rolling the AZ31–0.25Ca cast alloy without prior predeformation. The impact of corrugated rolling and/or flat rolling on texture modification, microstructure evolution, and mechanical properties of the magnesium alloy during two-pass rolling was examined using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), tensile tests at ambient temperature, and ABAQUS finite element simulation analysis. The results indicate that the AZ31–0.25Ca cast alloy, after homogenization with a coarse grain structure of ∼200 μm, can endure significant plastic deformation with a 60 % total rolling reduction in both corrugated-flat rolling (CFR) and flat-flat rolling (FFR) without experiencing edge cracking. Twinning is activated dramatically except for dislocation slip during CFR, which induced high-density dislocations piling up at the twin boundaries and grain boundaries of α-Mg grains. The CFR sheet exhibited a macroheterogeneous structure attributed to the distinctive corrugated roll profile. Elevated shear strain and intensified frictional shear stress were observed at the trough, resulting in the formation of an asymmetric cross shear band in the CFR sheet. Denser deformation twins and finer recrystallized grains are present at the trough, whereas fewer and coarser ones are observed at the peak, while there is a significant texture weakening effect for corrugated rolling in contrast to the conventional flat rolling. but the stress and strain heterogeneity and asymmetric cross shear band also induce strong stress concentration and result in a premature cleavage fracture and a lower tensile property in CFR sheet compared to that of the FFR sheet.

Uncovering Nanoindention Behavior of Amorphous/Crystalline High-Entropy-Alloy Composites.

Amorphous/crystalline high-entropy-alloy (HEA) composites show great promise as structural materials due to their exceptional mechanical properties. However, there is still a lack of understanding of the dynamic nanoindentation response of HEA composites at the atomic scale. Here, the mechanical behavior of amorphous/crystalline HEA composites under nanoindentation is investigated through a large-scale molecular dynamics simulation and a dislocation-based strength model, in terms of the indentation force, microstructural evolution, stress distribution, shear strain distribution, and surface topography. The results show that the uneven distribution of elements within the crystal leads to a strong heterogeneity of the surface tension during elastic deformation. The severe mismatch of the amorphous/crystalline interface combined with the rapid accumulation of elastic deformation energy causes a significant number of dislocation-based plastic deformation behaviors. The presence of surrounding dislocations inhibits the free slip of dislocations below the indenter, while the amorphous layer prevents the movement or disappearance of dislocations towards the substrate. A thin amorphous layer leads to great indentation force, and causes inconsistent stacking and movement patterns of surface atoms, resulting in local bulges and depressions at the macroscopic level. The increasing thickness of the amorphous layer hinders the extension of shear bands towards the lower part of the substrate. These findings shed light on the mechanical properties of amorphous/crystalline HEA composites and offer insights for the design of high-performance materials.

Bending and linear dynamic response of nanoplates in thermal environment

The article combines the finite element method with the novel-type sinusoidal hyperbolic shear strain hypothesis to study the static bending response and dynamics of nanoplates subjected to simultaneous mechanical, thermal, and voltage loads. The plate equilibrium equation is developed from the concept of potential work, which takes into account the impact of the flexoelectricity effect. The formula for the electric field that is operating on the plate becomes more complicated when the new strain theory is used; nonetheless, its complexity adequately displays both the mechanical and electrical components, as well as the electromechanical components, that are acting on the nanoplate. The computational theory is also verified through comparison with previously published data. The article also investigates the influence of some material factors, temperature, and external voltage on displacement response and charge polarization of nanoplates in the case of subjecting to static and time-varying loads. The results demonstrate that the thermomechanical-electrical response of nanoplates is dependent on numerous factors, which serve as the foundation for the practical design and application of nanostructures.

Enhancement effect of calcium carbide residue and rice husk ash on soft soil: Small-strain property and micro mechanism

The resource utilization of calcium carbide residue (CCR) and rice husk ash (RHA) is helpful to save resources and alleviate environmental pollution. In this research, CCR and RHA were used to modify soft clay, and the resonant column test was conducted to explore its small-strain dynamic characteristics. The micro-mechanism of CCR-RHA modified soft clay (CRSC) was investigated by using scanning electron microscopy, X-ray diffraction and mercury intrusion tests. The findings demonstrated that the dynamic shear modulus of the CRSC increased with the increase of RHA content and confining pressure, but decreased with the increase of shear strain. In contrast, the damping ratio presents the opposite change law. The Hardin-Drnevich (H-D) model was used to fit the dynamic shear modulus/maximum dynamic shear modulus (G/Gmax)-shear strain γ and the damping ratio D-shear strain γ. As confining pressure increased, Gmax increased but Dmax dropped in CRSC specimens with the same RHA content. The changes of the fitted G/Gmax-γ curve could be divided into progressively decrease stage and rapid decrease stage, while the changes of the fitted D-γ curve could be separated into linear stage and slow stage, with the same turning point γ = 10−4. Microscopic tests revealed that the incorporation of CCR and RHA helped to promote the hydration reaction, and the generated hydration products such as calcium silicate hydrate were able to enhance the integrity and compactness of the CRSC. The results of this research putfward solid foundation for the application of CCR-RHA in the modification of soft soil.

Strength and deformation characteristics of waste mud–solidified soil

The treatment, disposal, and resource utilization of waste mud are challenges for engineering construction. This study investigates the road performance of waste mud–solidified soil and explains how solidifying materials influence the strength and deformation characteristics of waste mud. Unconfined compressive strength tests, consolidated undrained triaxial shear tests, resonant column tests, and consolidation compression tests were conducted to evaluate the solidification effect. The test results show that with an increase in cement content from 5 to 9%, the unconfined compressive strength of the waste mud–solidified soil increased by over 100%, the curing time was extended from 3 to 28 days, and the unconfined compressive strength increased by approximately 70%. However, an increase in initial water content from 40 to 60% reduced the unconfined compressive strength by 50%. With the increase of cement content from 5 to 9%, the cohesion and friction angles increased by approximately 78% and 24%, respectively. The initial shear modulus under dynamic shear increased by approximately 38% and the shear strain corresponding to a damping ratio decay to 70% of the initial shear modulus decreased by nearly 11%. The compression coefficient decreased by approximately 55%. Scanning electron microscopy and X-ray diffraction tests showed that a higher cement content led to the formation of more hydration reaction products, especially an increase in the content of AlPO4, which can effectively fill the pores between soil particles, enhance the bonding between soil particles, and form a skeleton with soil particles to improve compactness. Consequently, the strength of the waste mud–solidified soil increased significantly while its compressibility decreased. This study can provide data support for dynamic characteristics of waste mud solidified soil subgrade.

Effects of cutting tool geometry on material removal of a gradient nanograined CoCrNi medium entropy alloy.

CoCrNi medium-entropy alloys (MEAs) have attracted extensive attention and research because of their superior mechanical properties, such as higher ductility, strength, and toughness. This study uses molecular dynamics (MD) simulations to investigate the cutting behavior of a gradient nanograined (GNG) CoCrNi MEA. Moreover, it explores the influence of relative tool sharpness and rake angle on the cutting process. The results show that an increase in the average grain size of the GNG samples leads to a decrease in the average resultant cutting force, as predicted by the Hall-Petch relationship. The deformation behavior shows that grain boundaries are crucial in inhibiting the propagation of strain and stress. As the average grain size of the GNG sample increases, the range of shear strain distribution and average von Mises stress decreases. Moreover, the cutting chips become thinner and longer. The subsurface damage is limited to a shallow layer at the surface. Since thermal energy is generated in the high grain boundary density, the temperature of the contact zone between the substrate and the cutting tool increases as the GNG size decreases. The cutting chips removed from the GNG CoCrNi MEA substrates will transform into a mixed structure of face-centered cubic and hexagonally close-packed phases. The sliding and twisting of grain boundaries and the merging of grains are essential mechanisms for polycrystalline deformation. Regarding the cutting parameters, the average resultant force, the material accumulation, and the chip volume increase significantly with the increase in cutting depth. In contrast to sharp tools, which mainly use shear deformation, blunt tools remove material by plowing, and the cutting force increases with the increase in cutting-edge radius and negative rake angle.

Finite element simulations of smart fracture plates capable of cyclic shortening and lengthening: which stroke for which fracture?

Introduction: Bone healing can be improved by axial micromovement, as has been shown in animals and human patients with external fixators. In the development of smart fracture plates, the ideal amount of stroke for different fracture types in the different healing stages is currently unknown. It was hypothesized that the resulting strain in the fracture gap of a simple tibial shaft fracture does not vary with the amount of axial stroke in the plate, the fracture gap size, and the fracture angle. Methods: With finite element simulations based on body donation computed tomography data, the second invariant of the deviatoric strain tensor (J2), strain energy density, hydrostatic strain, octahedral shear strain, and percentage of the fracture gap in the "perfect healing window" were computed for different gap sizes (1-3mm), angles (5°-60°), and plate stroke levels (0.05-0.60mm) in three healing stages. Multiple linear regression analyses were performed. Results: Findings showed that an active fracture plate should deliver an axial stroke in the range of 0.10-0.45mm. Different optimal stroke values were found for each healing phase, namely, 0.10-0.25mm for the first, 0.10mm for the second, and 0.35-0.45mm for the third healing phase, depending on the fracture gap size and less on the fracture angle. J2, hydrostatic strain, octahedral shear strain and the strain energy density correlated with the fracture gap size and angle (all p < 0.001). The influence of the fracture gap size and angle on the variability (adjusted R2) in several outcome measures in the fracture gap was shown to vary throughout healing. The contribution to the variability of the percentage of the fracture gap in the perfect healing window was greatest during the second healing phase. For J2, strain energy density, hydrostatic strain, and octahedral shear strain, the fracture gap size showed the greatest contribution in the third fracture healing phase, while the influence of fracture angle was independent of the healing phase. Discussion: The present findings are relevant for implant development and to design clinical studies that aim to accelerate fracture healing using axial micromovement.

Multiple factors-based damage level assessment method of concrete structures based on evidential reasoning and particle swarm optimization

Previous damage prediction methods of concrete structures usually fall into subjective and unreasonable assessments, which are usually limited to the special application scene with complex physical modeling depending on professional knowledges and experience. To overcome the above limitations, a multiple factors-based damage level assessment method of concrete structures is proposed based on evidential reasoning and particle swarm optimization. According to the method, multi-source data can be integrated for damage rules generation and quantitative damage level assessment automatically. The number and types of the used multi-source data can be chosen freely according to the special application scene. Finally, multi-source data including the normal strain in X-direction, normal strain in Y-direction, and the corresponding shear strain of two concrete structures under cyclic loads are utilized to verify the developed method. The results show that the damage level assessment results match well with the corresponding experimental results, which has a high reliability index based on the developed method. The ability of the method with good generality and flexibility is verified, which shows that the method can be used to achieve the reasonable damage level assessment of concrete structures.

Geometrically nonlinear analysis of plates and shells by a cell-based smoothed CS-MITC18+ flat shell element with drilling degrees of freedom

A development of a 3-node triangular flat shell element to analyze geometric nonlinearity of plate and shell structures is presented in this study. The proposed flat shell element has 6 degrees of freedom per node, including the drilling rotational ones, by using the Allman-type approximations for the in-plane displacements and the bending displacement approximations enriched by a cubic shape function at the bubble node located at the element's centroid. The geometrically nonlinear behaviors are described by the von Karman's large deflection assumption. The membrane and bending strains of the presented flat shell elements are averaged over sub-triangular elements based on the cell-based smoothed (CS) technique. To attenuate the shear locking phenomenon, the transverse shear strains are re-interpolated following the mixed interpolation of tensorial components (MITC) technique designed for the 3-node triangular degenerated shell elements enriched by a cubic bubble function (MITC3+). Combined with the Newton-Raphson iterations and load increments predicted by the arc-length method, the suggested 3-node triangular flat shell elements, namely the CS-MITC18+ element, can analyze moderately geometrical nonlinearity, including the snap-thought and snap-back behaviors, of various plates and shells with the different shapes, thickness, and boundaries. The numerical investigations show that the load-displacement curves provided by the CS-MITC18+ flat shell elements well agree with other references.

Micromechanical influence of near-surface adherend morphology and bondline fillers on the strain distribution in shear-loaded composite bonds

The near-surface morphology in the joining areas of adherends has a significant impact on the fatigue behavior of adhesively bonded composites. In the production process of composites, numerous opportunities exist for dictating surface morphology through the utilization of different top-layer semi-finished products. For instance, release films and peel ply fabrics can be employed to modulate the thickness and topography of the upper resin layer. These materials are subsequently removed prior to the further processing and assembly of the composites, leaving their negative imprint on the material surface. The resultant structures typically exhibit dimensions on the scale of a few micrometers. Another component in adhesive bonds are fillers, which have diameters in the same size range. Both adherend morphology and fillers influence the macroscopic behavior of the bonded joint. By in situ examining bonded end-notched flexure specimens inside a scanning electron microscope, the adhesive layer and the near-surface region of the adherends can be observed in detail under load. Evaluating these scanning electron microscope images using digital image correlation enables quantitative analysis of the strain distribution within the micrometer range. This allows the identification of the effects the adherend's near-surface morphology and the composition of the bondline (e.g. fillers, meshes) have on the shear strain distribution along bondlines. Consequently, conclusions can be drawn regarding their influence on the service life of adhesive bonds.

Valley-Free Silicon Fins Caused by Shear Strain.

Electron spins confined in silicon quantum dots are promising candidates for large-scale quantum computers. However, the degeneracy of the conduction band of bulk silicon introduces additional levels dangerously close to the window of computational energies, where the quantum information can leak. The energy of the valley states-typically 0.1meV-depends on hardly controllable atomistic disorder and still constitutes a fundamental limit to the scalability of these architectures. In this work, we introduce designs of complementary metal-oxide-semiconductor (CMOS)-compatible silicon fin field-effect transistors that enhance the energy gap to noncomputational states by more than one order of magnitude. Our devices comprise realistic silicon-germanium nanostructures with a large shear strain, where troublesome valley degrees of freedom are completely removed. The energy of noncomputational states is therefore not affected by unavoidable atomistic disorder and can further be tuned insitu by applied electric fields. Our design ideas are directly applicable to a variety of setups and will offer a blueprint toward silicon-based large-scale quantum processors.

Mechanical responses and fracturing behaviors of coal under complex normal and shear stresses, Part I: Experimental results

This work presents experimental tests based on coal collected from a coal mine based underground water reservoir (CMUWR). The mechanical responses of dry and water-soaked coal samples under the complex normal and shear stresses under multi-amplitude and variable frequency is investigated. The experimental results reveal the effects of stress path, water soaking and frequency on deformation, energy dissipation, secant modulus and shear failure surface roughness. The experimental results show that when normal and shear stresses are applied simultaneously, there is a significant competitive relationship between them. On the dominant side, the strain rate will be significantly increased. The sample under a loading frequency of 0.2 Hz exhibits a longer fatigue life. During the cyclic shear test, the shear strain of the water-soaked sample is higher than that of the dry samples. The average roughness coefficient of failure surface exhibits an increasing pattern with increase in shear strength, the elevated roughness of a shear surface is advantageous in constraining shear displacements of specimens, thereby lowering the energy dissipation. This study can provide theoretical and practical implications for a long-term safety evaluation of CMUWR.

Nanostructuring and Hardness Evolution in a Medium‐Mn Steel Processed by High‐Pressure Torsion Technique

Severe plastic deformation (SPD) is performed on a newly developed medium‐Mn steel with the composition of Fe–7.66Mn–2Ni–1Si–0.23C–0.05Nb (wt%) to achieve a nanocrystalline microstructure. The SPD process utilizes the high‐pressure torsion (HPT) technique, resulting in a nominal shear strain of approximately 36 000% after processing the disk for 10 turns. In X‐Ray diffraction line profile analysis, an increase in dislocation density to around 230 × 1014 m−2 is observed. In addition, under high strains, a face‐centered cubic (fcc) secondary phase emerges within the body‐centered cubic (bcc) matrix. In analytical transmission electron microscopy, using energy‐dispersive X‐Ray spectroscopy, it is indicated that the secondary‐phase particles are enriched in Al, Mn, and Si. As the strain imposed during HPT increases, the simultaneous rise in dislocation density and nanostructuring lead to material hardening. However, the partial phase transformation from bcc to fcc contributes to material softening. As a result of these two opposite effects, the hardness exhibits a non‐monotonic variation with the shear strain, displaying, for 10 turns of HPT, a lower hardness compared to fewer turns, despite the continuous increase in dislocation density and decrease in crystallite size.