Deformation Mechanisms Research Articles

Dynamic Deformation Mechanisms and Mechanical Properties of Additively Manufactured Closed‐Cell Foams of Various Topologies

Closed‐cell foams are widely used in energy absorption and load‐bearing applications. Herein, four lightweight closed‐cell foam topologies—tetrakaidecahedron, octet, spherical, and reverse hexagonal—are designed, manufactured, and mechanically tested. The structures are fabricated from acrylonitrile butadiene styrene using fused deposition modeling and subjected to low‐velocity impact to investigate their elastic, plastic, and energy absorption behavior under dynamic loading. Deformation mechanisms are investigated to explore the role of topological architectures on mechanical response. Among the structures, the reverse hexagonal topology exhibits the highest yield strength and elastic stiffness, making it suitable for load‐bearing applications. However, it demonstrates poor energy absorption due to its inability to utilize joints as plastic hinges during impact. In contrast, the octet structure exhibits superior energy absorption through a layer‐by‐layer collapse mechanism but offers limited elastic properties. The formation of shear bands in tetrakaidecahedron structure leads to midrange elastic properties. The spherical structure, however, shows poor energy absorption due to its unsystematic deformation and cell‐wall distortion. The tetrakaidecahedron foam shows increased strength but reduced energy absorption during impact compared to quasi‐static compression. These findings highlight the importance of considering dynamic mechanical properties when designing structures for impact‐prone applications throughout their service life.

Atomic-scale study on the deformation mechanism of nanofabrication in nickel-based single-crystal superalloys embedded with NbC particles

Atomic-scale study on the deformation mechanism of nanofabrication in nickel-based single-crystal superalloys embedded with NbC particles

Deep‐Learning Enhanced SrAl2O4: (Eu2+, Dy3+, Nd3+) Mechanoluminescence Film for Distributed Perception of Mechanical Deformation and Fracture

AbstractMechanoluminescence (ML) sensor‐derived distributing measurement urgently needs to overcome the trade‐off between luminous intensity and afterglow duration. In this article, a strontium aluminate (SrAl2O4) based ML sensing candidate is controllably synthesized by solid‐solution reaction of powdered precursors of SrCO3 and Al2O3 under hybrid doping of rare earth cations (Eu2+, Dy3+, Nd3+) at 1400 °C. Compared with traditional SrAl2O4: Eu2+, SrAl2O4: (Eu2+, Dy3+, Nd3+) (SAOEDN) has demonstrated highly enhanced luminous intensity (over two orders increase), robust ML behavior (300 cycles), and tunable afterglow performance (50 to 325 s) after synergistic regulation of trap depth (from 0.2 to 0.88 eV). After in situ compounding of SAOEDN with epoxy resin matrix, a flexible ML sensing film is created for distributed detection of engineering strain distribution. The ML effect triggered by mechanical deformation presented an approximately linear dependence between strain and luminous intensity with a higher spatiotemporal resolution. As a result, the engineering strain field is reconstructed via a deep learning‐derived image‐to‐image mapping process after eliminating the disturbance of afterglow. Moreover, the SAOEDN based ML film is capable of accurately detecting and capturing fracture propagation of engineering materials. It is suggested promising potential for distributed non‐contact detection of stress and strain fields in engineering applications.

Experimental Validation of Clamping-Type Mesh Fastening Method Using Thin Plates and Push-Button Rivets for Deployable Mesh Antennas

Deployable mesh antennas offer advantages such as high gain, ultra-light weight, and high packaging efficiency. However, the mesh that constitutes the reflection surface is prone to deformation due to its low stiffness, which directly affects the performance of the antenna. Therefore, it is essential to minimize the mechanical deformation of the mesh caused by external forces in order to achieve the target performance. In particular, the fastening interface between the mesh and the antenna structure is a critical area where high tensile forces are incurred due to the dynamic behavior of the antenna structure during ground tests, launch environments, and on-orbit operation. This causes degradation in the precision of the reflection surface. Therefore, an important part of the antenna development process is researching mesh fabric fastening methods that minimize the deformation of the reflection surface. Nevertheless, existing studies have only briefly mentioned mesh fastening methods, with limited systematic analysis of their impact on the mechanical properties of mesh fabric. In this paper, we propose a clamping-type mesh fastening method that combines push-button rivets and thin plates, which have high workability during mesh assembly, and conduct experimental validation. The characteristics of each fastening method were analyzed through tensile strength tests conducted at the mesh fabric level, and the results of the repeated tensile tests verified the effectiveness of the proposed fastening method.

Porosity and Conductivity Dual‐Gradient Design on Ultrathin 3D Nanofibrous Anode for Flexible Zn‐Ion Batteries

AbstractFlexible Zn‐ion batteries (ZIBs) have been regarded as a promising energy storage solution for flexible electronics. However, the challenges of dendrite growth due to uneven current density distribution and limited anode flexibility have impeded their practical application. Herein, a flexible 3D zinc anode with a dual gradient in porosity and conductivity is presented. This dual‐gradient nanofibrous anode exhibits exceptional flexibility and durability, showing less than a 10% change in resistance after 15 000 bending cycles. The vertical gradient distribution in conductivity promotes preferential zinc deposition at the bottom section, while the gradient in porosity facilitates Zn2⁺ ion migration and ensures timely replenishment of the inner space of the membrane. The combination of the 3D structure and dual‐gradient design fosters bottom‐up zinc deposition, effectively preventing dendrite formation. Symmetric cells with this dual‐gradient anode demonstrate outstanding cycling stability, maintaining more than 410 h of operation at a current density of 1 mA cm−2 for 1 mA h cm−2, surpassing reference samples and most previously reported 3D zinc anodes. The quasi‐solid‐state ZIBs assembled with this dual‐gradient anode exhibit excellent stability under various mechanical deformations. These 3D nanofibrous anodes with dual‐gradient designs hold great promise for advancing the practical application of flexible Zn‐ion batteries.

Effect of Strain Rate on Deformation Mechanisms of a Mg Alloy

Effect of Strain Rate on Deformation Mechanisms of a Mg Alloy

Study on the law of stress distribution in the presence of remaining coal pillar in a close-distance coal seam and the reasonable location of the roadway

In order to reveal the impact of remaining coal pillar on roadway layout of the lower seam after the upper part of the close coal seam is reversely mined, theoretical analysis and numerical simulation are conducted in this paper. With the roadway to be excavated in a mine located in Shanxi as the research object, theoretical analysis and numerical simulation are performed to explore the evolution of stress field in the lower coal seam under the influence of the leftover coal pillar. Also, an analysis is conducted on the mechanism of deformation and destruction occurring to the roadway in the lower coal seam, so as to determine the rational layout of roadway in the lower coal seam and the optimal parameters related to roadway support. The research results are as follows. (1) The mining operations conducted in the upper coal seam affect the magnitude of the principal stress, the principal stress ratio and the principal stress deflection angle of the lower coal seam, causing different patterns of deflective stress in the lower coal seam. (2) With the center line of coal pillar as the axis of symmetry, the influencing factors for the lower coal seam are symmetrically distributed. The larger the distance from the centerline, the larger the deflected plastic zone of the roadway surrounding rock. (3) In order to determine the rational layout of the roadway, the study area is divided into two zones by considering the main influencing factors. Allowing for the mode of mining and to ensure safety, it is recommended that the roadway should be positioned at the edge of the H-II area, such as at the location that is 15–20 m or 40–45 m away from the study area. Taking into account these influencing factors, the original tunnel support parameters are optimized. According to the data collected through on-site mining pressure observation, the support optimization scheme achieves satisfactory results.

Study on the multi-stage instability mechanism of the Wachangwan landslide in Gaoxian County, Sichuan, China

Landslides are one of the most common natural disasters worldwide. On September 27, 2020, a large-scale landslide occurred in the Tianzhulin area of Huangni Village, Wenjiang Town, Gao County, known as the Wachangwan Landslide. Through field investigations and UAV aerial photography, the causes and deformation processes of the Wachangwan landslide were thoroughly revealed. Additionally, the displacement and deformation of the landslide were analyzed using the discrete element method. The key findings are as follows: The Wachangwan landslide is a typical multistage landslide. Prolonged heavy rainfall induced sliding in the front part of the landslide body, which dragged the rear, less stable soil mass, further exacerbating deformation and eventually forming a multistage landslide. The non-sliding zone is located between zones III-1 and III-2, influenced by pressure from adjacent sliding zones. However, based on rainfall data and displacement monitoring, the non-sliding zone remains generally stable at present. Using the discrete element method, the deformation mechanism and subsequent evolution of the Wachangwan landslide under rainfall conditions were analyzed. The landslide exhibited a failure mode characterized by traction, tensile fracturing, and sliding. A stability calculation method for multistage landslides under rainfall conditions was established, combining the traditional transfer coefficient method and the multistage landslide effects. By analyzing the current stability of the Wachangwan landslide, the results provide a novel approach for evaluating the stability of multistage landslides.

Deformation Behavior and Strengthening Mechanisms of a Typical Bimodal L12 Precipitates Strengthened Nickel‐Based Superalloy Over a Wide Range of Strain Rates and Temperatures

Nickel‐based superalloys with bimodal L12 precipitates have been widely used in extreme environments due to their excellent mechanical properties. However, limited studies have focused on the deformation behavior and mechanisms under combined high strain rates and high temperatures. In this study, uniaxial compression experiments were conducted on a typical bimodal L12 precipitates strengthened nickel superalloy over a wide range of temperatures (293–1273 K) and strain rates (1 × 10−3 s−1–5 × 103 s−1) to reveal the coupling effect of temperature and strain rate on the mechanical behavior. The results show that the mechanical behavior is highly sensitive to temperature and strain rate, with the alloy exhibiting remarkable high temperature strength, particularly under dynamic loading. The third‐type strain aging (3rd SA) effect is observed in this alloy, and its underlying mechanism is analyzed. Microstructural characterizations are conducted at various conditions, providing multiscale insight into the intricate relationship between microstructure and property. A transition in dominant deformation mechanisms is observed, shifting from anti‐phase boundary dislocation pair shearing to stacking fault as temperature increases. Additionally, a comprehensive diagram is provided to elucidate the deformation mechanisms of the alloy under a wide range of strain rates and temperatures.

Adsorption–Desorption–Seepage Characteristics and Deformation Mechanism of Confined Coal for Flue Gas under Different Water Saturations

Adsorption–Desorption–Seepage Characteristics and Deformation Mechanism of Confined Coal for Flue Gas under Different Water Saturations

Quantitative Analysis of Mechanically Alloyed CuZrB Powders

Copper matrix composites are proving to be a suitable match for the present engineering needs of the market where higher temperature resistance and good microstructural stability are required. Powder metallurgy technique was used to procure the powder mixture, Cu-2Zr-0.6B (wt.%). Different mechanical alloying (MA) parameters were examined with the main focus on time, ranging from 10 h to 40 h. SEM analysis was employed to determine structural and morphological changes of the mechanically alloyed powder mixture. MIPAR image analysis software was used to complete the quantitative analysis of the mechanically alloyed CuZrB powders. Changes in size and shape of powder particles were determined during up to 40 h of MA with key points after every 10 h. It was concluded that the powder particle size decreases as the MA time increases. With the increase in MA time the area of each particle decreases due to the dominant plastic deformation mechanisms as particles undergo high forces through ball-particle-ball and wall-particle-ball collisions during the MA process.

Stability analysis of existing tunnels under dynamic loads during excavation of new tunnels

Understanding the deformation mechanism and behaviour of adjacent tunnels subjected to dynamic train loads provides vital technical insights for engineering design. This study conducted a detailed analysis and revealed that tunnel excavation significantly affects the stability of adjacent existing tunnels under dynamic loads. First, we developed a dynamic load simulation approach and derived a calculation formula for shield-soil friction. A methodology for analyzing the stress in the surrounding rock of the tunnel was established. Subsequently, the impact of dynamic loads on the stability of existing tunnels was assessed through numerical simulations. Finally, the numerical results were compared with field-measured data to validate the reliability of the research findings. The results indicated that, compared to the condition without train load, the maximum vertical and lateral displacements at the vault of the existing tunnel under dynamic load condition increased by 2.9 mm and 1 mm, respectively, leading to an overall safety and stability coefficient reduction of approximately 0.1. Furthermore, the influence of dynamic loads on the stability of the existing tunnel intensified with increasing train speeds under various load conditions. For train speeds of ≤ 40 km/h, the dynamic load could effectively be considered as a static load. Notably, the surrounding soft rock exhibited a higher degree of stress release compared to the surrounding hard rock. The stresses at the soft-hard rock interface were found to potentially induce damage to the tunnel. In scenarios where new and existing tunnels were in proximity, the dynamic load was incorporated into the entire simulation process, yielding results that closely aligned with actual measurements.

An active transtensional fault system across the NE margin of the Tibetan Plateau and its influence on surrounding blocks

The newly discovered Tianzhu transtensional fault system cuts across the WNW-trending Qilian Shan orogen and thrust and strike-slip fault systems on the northeastern margin of the Tibetan Plateau. Using high-resolution satellite images, geomorphic mapping, trenching, and radiocarbon and optically stimulated luminescence dating, we found that the Tianzhu transtensional fault system consists of the Western Tianzhu Basin, Jinqianghe, Xuanmahe, Eastern Gulang, and Haxi faults, exhibiting active oblique normal faulting during the late Quaternary. The Tianzhu transtensional fault system experiences at least normal and left-lateral slip rates of 1.0 ± 0.2 mm/yr and 3.1 ± 0.2 mm/yr, respectively, and it is capable of producing earthquakes of Mw 7.2 or higher. The deformation patterns and mechanisms of large earthquakes differ on both sides of the fault system. It is believed that the Tianzhu transtensional fault system plays an important role in accommodating differential deformation of the NE Tibetan Plateau. Undergoing long-term tectonic processes, different parts of the NE Tibetan Plateau exhibit varying crustal motion, resulting in oblique shear and formation of the Tianzhu transtensional fault system. Combining analyses of fault distribution, seismic activity, and deep geophysical fields, the Tianzhu transtensional fault system and the Bayanwulashan and Langshan range-front faults in the northeast are likely to constitute a regionally evolving transtensional fault system, weakening the stability of the Gobi-Alashan block. Our results challenge the conventional understanding of continuous deformation along the Qilian-Haiyuan fault zone, provide new insights into the extension patterns of the NE Tibetan Plateau and its influence on the surrounding blocks, and inform our understanding of the types of transfer faults that cut through collisional orogens around the world.

Effect of Aging Treatments on the Nanoprecipitation Mechanism and Dynamic Impact Behavior of Mg-7.5Gd-3Y-0.5Zr Alloy

This study aims to enhance the dynamic impact mechanical properties of Mg-7.5Gd-3Y-0.5Zr alloy by investigating the effects of aging treatments on its microstructure and dynamic impact behavior. Using various techniques, including metallographic observation, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), microhardness testing and split-Hopkinson pressure bar tests, the microstructural and macroscopic static-dynamic properties of the alloy under different aging conditions were thoroughly examined. The findings indicate the following: The aging treatments identified based on hardness curves and TEM analysis include under-aging ([Formula: see text], peak-aging ([Formula: see text] and over-aging ([Formula: see text], with specific conditions of [Formula: see text]C for 3[Formula: see text]h, [Formula: see text]C for 12[Formula: see text]h and [Formula: see text]C for 12[Formula: see text]h, respectively. The alloy exhibits a maximum impact strength of 560 MPa[Formula: see text]under under-aging conditions. Under peak aging, the maximum impact strength increases to 596 MPa. The optimal impact strength under over-aging conditions is 558 MPa[Formula: see text]. The deformation mechanisms of the alloy under under-aging conditions are characterized by a combination of tensile and compressive twinning. In contrast, peak-aging and over-aging conditions primarily involve tensile twinning, with compressive twinning playing a secondary role. The fracture mechanisms of the alloy under various aging states are mainly a mix of ductile and brittle fractures. However, in the under-aged sample, the volume fraction of the dimples is significantly more than that of cleavage planes, which ductile-brittle mixed fracture dominated by ductile fracture; for the peak-aging alloy, the number of cleavage planes increases, showing ductile-brittle mixed fracture dominated by brittle fracture.

Compressive Behaviors and Deformation Mechanisms of Open‐Cell AlSi Foam

Open‐cell AlSi foams with varying cell sizes and pore structures are fabricated using infiltration casting. Foams with uniform cell sizes ranging from 2.0 to 4.0 mm and 1.5 to 2.0 mm exhibit typical open‐cell walls. In contrast, a foam with a mixed cell size distribution (1.5 to 4.0 mm) demonstrates improved connectivity but exhibits more structural defects. Quasistatic uniaxial compression tests are performed to evaluate the compressive behavior of the foams. The deformation process and energy absorption mechanisms of three foams are comprehensively analyzed from macroscopic sample scale to pore scale using X‐ray computed tomography. The results indicate that foams with smaller cell sizes deform uniformly, with the highest compressive strength of ≈20 MPa, while those with larger cell sizes exhibit localized deformation. The foam with mixed cell sizes and a hybrid scaffold structure (3D skeletal network) displays broader deformation zones and localized deformation, rather than distinct deformation bands.

Research on the Long-Term Mechanical Behavior and Constitutive Model of Cemented Tailings Backfill Under Dynamic Triaxial Loading

Cemented tailings backfill (CTB) plays an important role in mine filling operations. In order to study the long-term stability of CTB under the dynamic disturbance of deep wells, ultrafine cemented tailings backfill was taken as the research object, and the true triaxial hydraulic fracturing antireflection-wetting dynamic experimental system of coal and rock was used to carry out a static true triaxial compression test, a true triaxial compression test under unidirectional disturbance, and a true triaxial compression test under bidirectional disturbance. At the same time, the acoustic emission monitoring and positioning tests of the CTB were carried out during the compression test. The evolution law of the mechanical parameters and deformation and failure characteristics of CTB under different confining pressures is analyzed, and the damage constitutive model of the filling body is established using stochastic statistical theory. The results show that the compressive strength of CTB increases with an increase in intermediate principal stress. According to the change process of the acoustic emission ringing count over time, the triaxial compression test can be divided into four stages: the initial active stage, initial calm stage, pre-peak active stage, and post-peak calm stage. When the intermediate principal stress is small, the specimen is dominated by shear failure. With an increase in the intermediate principal stress, the specimen changes from brittle failure to plastic failure. The deformation and failure strength of CTB are closely related to its loading and unloading methods. Under a certain stress intensity, compared with unidirectional unloading, bidirectional unloading produces a greater deformation of the rock mass, and the failure strength of the rock mass is higher. This study only considers the confining pressure within the compressive limit of the specimen. Future research can be directed at a wider range of stresses to improve the applicability and reliability of the research results.

Investigation on the Bending Mechanism of Single-Crystal Copper Under High Bending Rates via Molecular Dynamics

Leaf spring-type flexible hinges serve as critical transmission components in kilogram quantization energy balance systems. Investigating their bending behavior is crucial for enhancing measurement accuracy and ensuring structural reliability. This work employs molecular dynamics simulations to analyze the mechanical properties and deformation characteristics of such hinges under varying bending rates. The findings reveal a significant correlation between the bending rate and the hinges’ plastic deformation and microstructural evolution, indicating the presence of a critical bending rate. When the bending rate is below the critical threshold, the hinges exhibit excellent structural stability, characterized by low dislocation density, reduced von Mises stress, and limited temperature rise, making them suitable for long-term use. Conversely, when the bending rate exceeds the critical threshold, the hinges undergo significant plastic deformation, including notable increases in stress and temperature concentration, as well as microstructural alterations. Specifically, the initially stable crystal structure is disrupted, leading to the formation of numerous defect structures. These changes result in localized instability and elevate the risk of fatigue damage. This work comprehensively elucidates the mechanical responses and failure mechanisms of flexible hinges, providing valuable data and guidance for their optimized design and application.

The role of surface deformation on responsivity of the pillared layer metal-organic framework DUT-8(Ni).

A unique feature of flexible metal-organic frameworks (MOFs) is their ability to respond dynamically towards molecular stimuli by structural transitions, resulting in pore-opening and closing processes. One of the most intriguing modes is the "gating", where the material transforms from the dense to the porous state. The conditions required for the solid phase structural transition are controlled by the kinetic barriers, including nucleation of the new phase commencing on the crystallite's outer surface. Thus, surface deformation may influence the nucleation, enabling deliberate tailoring of the responsivity. In the present contribution, we investigate how chemical surface treatments (surface deformation) affect the gate opening characteristics of a typical representative of gate pressure MOFs, DUT-8(Ni) ([Ni2(ndc)2(dabco)] n , ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). A combination of various complementary advanced characterization techniques, such as NMR, nanoFTIR, terahertz, in situ XPS, in situ EPR spectroscopies, and inverse gas chromatography, are applied to unravel the changes in surface energy and mechanism of surface deformation.

Characterizing positive and negative quantitative susceptibility values in the cortex following mild traumatic brain injury: a depth- and curvature-based study.

Evidence has linked head trauma to increased risk factors for neuropathology, including mechanical deformation of the sulcal fundus and, later, perivascular accumulation of hyperphosphorylated tau adjacent to these spaces related to chronic traumatic encephalopathy. However, little is known about microstructural abnormalities and cellular dyshomeostasis in acute mild traumatic brain injury in humans, particularly in the cortex. To address this gap, we designed the first architectonically motivated quantitative susceptibility mapping study to assess regional patterns of net positive (iron-related) and net negative (myelin-, calcium-, and protein-related) magnetic susceptibility across 34 cortical regions of interest following mild traumatic brain injury. Bilateral, between-group analyses sensitive to cortical depth and curvature were conducted between 25 males with acute (<14d) sports-related mild traumatic brain injury and 25 age-matched male controls. Results suggest a trauma-induced increase in net positive susceptibility focal to superficial, perivascular-adjacent spaces in the parahippocampal sulcus. Decreases in net negative susceptibility values in distinct voxel populations within the same region indicate a potential dual pathology of neural substrates. These mild traumatic brain injury-related patterns were distinct from age-related processes revealed by correlation analyses. Our findings suggest depth- and curvature-specific deposition of biological substrates in cortical tissue convergent with features of misfolded proteins in trauma-related neurodegeneration.

Revealing the mechanical behaviour and material micro-structure of graphite electrode coatings in lithium-ion batteries during lithiation.

Understanding the mechanical behaviour of graphite electrode coatings during lithiation is crucial for optimizing high-performance lithium-ion batteries. The first experiment reveals the elastoplastic response of liquid electrolyte-immersed graphite active particles bonded with sodium carboxymethyl cellulose and styrene butadiene rubber (CMC/SBR) across various states of charge (SOCs). Simultaneously, we have developed a phenomenological model to simulate the mechanical response of graphite-CMC/SBR composites during lithiation by tracking the evolution of mechanical properties within graphite particles and the composite's porosity. The results uncover that the graphite electrode coatings undergo significant elastic-plastic mechanical deformation and are strengthened and brittle due to active particle hardening and decreasing porosity in the lithiation process. Upon completion of lithiation, the graphite electrode coatings exhibit a twofold increase in ultimate stress and elastic modulus while microhardness quadruples. However, fracture elongation decreases by 60%. Furthermore, the lithiation process enhances the adhesion properties of the electrode coating. Importantly, our proposed model shows excellent agreement between the predicted tensile stress-strain curves and experimental data. Finally, we unveiled the influence of graphite electrode coating's plastic behaviour and liquid electrolyte on the mechanical integrity of the cylindrical battery structure.