Extreme Mechanics Letters最新文献

{"title":"Topology optimization for creating nonreciprocal compliant mechanisms: Numerical and experimental investigations","authors":"Vahid Shobeiri ,&nbsp;Yi Min Xie","doi":"10.1016/j.eml.2025.102345","DOIUrl":"10.1016/j.eml.2025.102345","url":null,"abstract":"<div><div>In this study, a topology optimization technique is developed based on the bi-directional evolutionary structural optimization (BESO) method for the creation of nonreciprocal complaint mechanisms (NCMs). The internal contact surface model is proposed as a simple and innovative approach to making complaint mechanism systems nonreciprocal. The design problem is formulated as maximizing the flexibility of NCMs with a desired level of nonreciprocity subject to a volume constraint. Based on the BESO method, a novel type of NCMs is developed with potential applications in various engineering fields. The topology optimization of a nonreciprocal inverter mechanism is studied, and the effectiveness of the proposed method is verified through experiments. The numerical and experimental results indicate that topologically optimized designs of NCMs and their asymmetric deformation can be significantly controlled by the degree of nonreciprocity. The findings from this study can be used as a basis for designing a wide range of nonreciprocal structural systems.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102345"},"PeriodicalIF":4.3,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A method to characterize the cavitation pressure of soft matter under superimposed azimuthal shear","authors":"Alexandria Rogers ,&nbsp;Yuan Ji ,&nbsp;Vladimir Coon ,&nbsp;Christopher J. Karber ,&nbsp;Jacob A. Rogers ,&nbsp;Justin W. Wilkerson","doi":"10.1016/j.eml.2025.102325","DOIUrl":"10.1016/j.eml.2025.102325","url":null,"abstract":"<div><div>In many applications (<em>e.g.</em> contact sports, vehicular accidents, blunt force trauma, traumatic brain injury, drug delivery, surgeries), biological tissues and other soft matter are subject to complex, multi-axial stress states that can induce a variety of material deformation and failure modes. Cavitation is a particular soft matter failure mode that is insufficiently understood and poorly characterized. To the best of the authors’ knowledge, cavitation has only been investigated in initially stress-free samples. The lack of data for soft matter behavior under multi-axial stress states prevents the development and validation of generalized cavitation theories. This study introduces a superimposed shear cavitation (SSC) apparatus that enables an examination of the role torsional shear stress plays in cavity nucleation, expansion, and collapse in soft matter. Our proposed SSC test expands on the well-established needle-induced cavitation (NIC) experiment by housing the gel in a Taylor–Couette cell instead of a conventional beaker. This modification enables the application of azimuthal shear stresses to the gel sample prior to the insertion and pressurization of the syringe needle. To demonstrate its capability, our SSC apparatus was used to measure the critical pressure (<span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>) of tri-block copolymer (PMMA-PnBA-PMMA) gel samples pre-loaded with various degrees of torsion. In a limited set of experiments, <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> was found to generally increase with increasing amount of applied pre-shear stress, in qualitative agreement with a generalized cavitation theory first introduced by Lopez-Pamies and co-workers, thereby providing some degree of evidence that the SSC apparatus is functioning as intended. Motion tracker particles embedded in the top surface of the gel provide additional evidence that the SSC apparatus generates the intended azimuthal pre-deformation field.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102325"},"PeriodicalIF":4.3,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143886448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spallation in homogeneous and gradient nano-grained high-entropy alloys","authors":"Xin Du ,&nbsp;Jianfeng Zhao ,&nbsp;Meizhen Xiang ,&nbsp;Fuping Yuan ,&nbsp;Xiaohu Yao ,&nbsp;Xu Zhang","doi":"10.1016/j.eml.2025.102342","DOIUrl":"10.1016/j.eml.2025.102342","url":null,"abstract":"<div><div>The strength and hardness can be improved by adjusting grain size in nano-grained structures. However, their behavior under extreme shock loading remains largely unexplored. This study investigates the shock wave response and spallation characteristics of homogeneous and gradient nano-grained CoCrFeMnNi high-entropy alloys (H-HEA and G-HEA) by molecular dynamics simulation. The results demonstrate that both H-HEA and G-HEA exhibit an elastic-plastic two-wave separation phenomenon, which diminishes with decreasing grain size. Notably, the spall strength of H-HEAs initially decreases and then increases as the grain size decreases, while G-HEA consistently shows superior spall strength compared to H-HEA. The findings suggest that GNG structures inherently possess better shock resistance. The spall strength is closely related to the nucleation ability of voids, which is dominated by the content of disordered structure. In nano-grained structures, voids mainly nucleate at grain boundaries, and the subsequent growth and coalescence lead to intergranular fracture. Additionally, shock loading induces various plastic mechanisms such as stacking faults, deformation twinning, and phase transformations. These findings underscore the critical role of microstructural design, especially GNG structure, in enhancing the shock mechanical properties of HEAs and contribute to the application of HEA in extreme shock environments.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102342"},"PeriodicalIF":4.3,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143879202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Negative-pressure soft pneumatic actuators enabled by asymmetrically distributed bending units","authors":"Zeyu Fu ,&nbsp;Tianyu Chen ,&nbsp;Haoran Zou ,&nbsp;Zhiwei Zhu ,&nbsp;Zichen Deng ,&nbsp;Yifan Wang","doi":"10.1016/j.eml.2025.102340","DOIUrl":"10.1016/j.eml.2025.102340","url":null,"abstract":"<div><div>Soft pneumatic actuators are highly flexible and can adapt to complex environments, attracting significant attention for their ability to operate in settings where rigid actuators cannot. Most existing soft pneumatic actuators are powered by positive pressure, which has the disadvantage of volume increase during operation and risk of exploding under large pressures. In this study, we designed a new type of soft actuator by inducing asymmetric bending deformation throughout a holey structure under negative pressure. Using finite element analysis and a theoretical model, we studied the effects of various geometric parameters on the structure's bending behavior. We found that the displacement of the circle's center from the central axis is a parameter with the most significant impact on the bending behavior of the structure. By designing circular holes with offset from the central axis, the structure can bend toward the offset direction during subsequent bending deformation. Based on this deformation mechanism, we designed a soft gripper that bends upon actuation and effectively picks up objects. We further designed a bi-directional gripper that bends towards both sides and a circular gripper that contracts towards the center upon evacuation to hold objects. These soft grippers’ grasping capabilities are validated by experimental tests. Finally, by arranging the holes in a wavy pattern within the structure, we created a crawling robot that moves forward through cyclic negative pressure actuation. These findings highlight the potential of leveraging bending behaviors in asymmetrically distributed holey structures for the development of negative-pressure driven soft actuators and robots.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102340"},"PeriodicalIF":4.3,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and optimization of pressure-tolerant flexible systems under extreme hydrostatic pressure","authors":"Letian Gan ,&nbsp;Dongrui Ruan ,&nbsp;Haijun Wang ,&nbsp;Zhe Wang ,&nbsp;Yanzhao Shi ,&nbsp;Yiming Hu ,&nbsp;Peng Zhou ,&nbsp;Fanghao Zhou ,&nbsp;Zheng Jia ,&nbsp;Tiefeng Li","doi":"10.1016/j.eml.2025.102339","DOIUrl":"10.1016/j.eml.2025.102339","url":null,"abstract":"<div><div>Soft robots have been increasingly developed and deployed for deep-sea applications in recent years. Unlike traditional underwater robots that rely on bulky pressure vessels for protection, some soft robots can be directly exposed to hydrostatic pressure utilizing a polymer-encapsulation approach. This approach optimizes the structure of electronic components in soft robots to eliminate high-pressure interfaces, yet clear design guidelines remain absent due to its complexity. This paper introduces a design methodology for pressure-tolerant electronics; that leverages the Eshelby inclusion theory and finite element analysis. A parameter <em>κ</em> called the geometric coherence index for numerical optimization is proposed to evaluate the arrangement of PCB components. Calculations and simulations have demonstrated that the optimized circuit board components exhibit a reduction of up to 45.5 % in both maximum and average shear stress under high hydrostatic pressure. A circuit board prototype has been manufactured and then tested at a depth of 10,900 m in the Mariana Trench. Field tests have confirmed the effectiveness of this method, demonstrating its potential for improving deep-sea exploration technologies.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102339"},"PeriodicalIF":4.3,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-scale investigation of orientation-dependent mechanical properties and fracture propagation in cortical bone using digital volume correlation and atomic force microscopy","authors":"Hutomo Tanoto ,&nbsp;Hanwen Fan ,&nbsp;Anoushka Prabhu ,&nbsp;Fernanda Espinoza ,&nbsp;Yuxiao Zhou","doi":"10.1016/j.eml.2025.102338","DOIUrl":"10.1016/j.eml.2025.102338","url":null,"abstract":"<div><div>This study investigates the orientation-dependent mechanical properties and fracture propagation behavior in bovine cortical bone, focusing on the role of lamellar plane orientation and its internal hierarchical structures—both of which are critical to bone mechanical strength and fracture resistance. By combining mechanical testing, micro-computed tomography (micro-CT), digital volume correlation (DVC), and atomic force microscopy (AFM), we examined region- and orentation-dependent mechanical properties of cortical bone, as well as the crack propagation influenced by underlying microstructures. At sub-millimeter scale, three-dimensional (3D) displacement and strain captured through <em>in situ</em> three-point bending and DVC provided detailed insights into internal deformation patterns during crack propagation. Distinct crack propagation behaviors were observed in bone samples with lamellar planes oriented parallel and perpendicular to the loading plane. AFM nanomechanical mapping was performed on cracked cross-sections, revealing the heterogeneous mechanical properties within the hierarchical lamellar structure. These micrometer-scale measurements, obtained from orthogonal cracked cross-sections, help explain the different crack propagation mechanisms observed during the bending experiments. Our findings demonstrate that the orientation of lamellar plane— the fundamental structural component of both plexiform and osteonal bone—relative to the loading plane plays a critical role in determining crack paths and local strain distribution. The integrated application of DVC and AFM provides a multiscale perspective on fracture resistance in cortical bone. These insights have important implications for the design of biomimetic materials in bone implants and for improving clinical assessments of fracture risk.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102338"},"PeriodicalIF":4.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bridging the impact response of polymers from the nanoscale to the macroscale","authors":"Kyle R. Callahan ,&nbsp;Katherine M. Evans ,&nbsp;William F. Heard ,&nbsp;Santanu Kundu ,&nbsp;Edwin P. Chan","doi":"10.1016/j.eml.2025.102331","DOIUrl":"10.1016/j.eml.2025.102331","url":null,"abstract":"<div><div>Impact from a fast-moving object is a common event, but it can vary greatly in terms of scale, speed, and energy depending on the specific case. Recently, it has been suggested that scaling analysis can be used to relate the impact performance of materials at the nano- and microscale to their behavior at the macroscale, which is relevant for most applications. In this study, we explore the broad applicability of this approach by conducting micro- and macroprojectile impact tests on polymethyl methacrylate and polycarbonate films. By applying Buckingham <span><math><mi>Π</mi></math></span> dimensional analysis to all the impact test results, we demonstrate that the minimum perforation velocity is directly related to the geometric and material properties of each system across a broad range of size and energy scales. Interestingly, we find that the failure stress of the polymer, a critical material property that defines perforation resistance, can be empirically determined based on the deformation of the specific impact test.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102331"},"PeriodicalIF":4.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deformation and adiabatic heating of single crystalline and nanocrystalline Ni micropillars at high strain rates","authors":"Nidhin George Mathews ,&nbsp;Matti Lindroos ,&nbsp;Johann Michler ,&nbsp;Gaurav Mohanty","doi":"10.1016/j.eml.2025.102336","DOIUrl":"10.1016/j.eml.2025.102336","url":null,"abstract":"<div><div>The deformation behavior of single crystal and nanocrystalline nickel were studied using <em>in situ</em> micropillar compression experiments from quasi-static to high strain rates up to 10³ s⁻¹. Deformation occurred by dislocation slip activity in single crystal nickel whereas extensive grain boundary sliding was observed in nanocrystalline nickel with a shift towards more inhomogeneous, localized deformation above 1 s⁻¹. The strain rate sensitivity exponent was found to change at higher strain rates for both single crystal and nanocrystalline nickel, while the overall strain rate sensitivity was observed to be of the same value for both. With increasing high strain rate micropillar compression tests being reported, the issue of adiabatic heating in micropillars becomes important. We report crystal plasticity based finite element modeling to estimate the adiabatic heating, spatially resolved within the micropillar, at the highest tested strain rates. The simulations predicted a significant temperature rise of up to 200 K in nanocrystalline nickel at the grain boundaries, and 20 K in single crystalline nickel due to strain localization. Transmission Kikuchi Diffraction analysis of nanocrystalline nickel micropillar post compression at 10³ s⁻¹ did not show any grain growth.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102336"},"PeriodicalIF":4.3,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143870479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A method for identifying the damage thresholds of porcine brain under low- and medium-strain rates","authors":"Zhihui Qu ,&nbsp;Yimou Fu ,&nbsp;Qiuping Yang ,&nbsp;Jingyu Wang ,&nbsp;Liqun Tang ,&nbsp;Shaoxing Qu","doi":"10.1016/j.eml.2025.102335","DOIUrl":"10.1016/j.eml.2025.102335","url":null,"abstract":"<div><div>Predicting the damage thresholds of brain tissue is crucial for preventing permanent pathological changes and developing therapeutic interventions. This study presents a method for determining the damage thresholds of porcine brain tissue using experimental data and theoretical modeling. By conducting loading and unloading experiments on porcine brain samples, the mechanical responses under varying strain rates and maximum compressive strains are analyzed. A constitutive model incorporating viscoelastic behavior, the Mullins effect, and residual deformation is proposed, effectively characterizing the mechanical properties of the brain tissue. By calculating the ratio of damage-induced dissipated energy and viscoelastic dissipated energy, the extent of damage under different maximum compression strain is quantified. The method’s reliability is validated through examining changes in modulus between the stress–strain curves obtained from the first and second loadings. At a strain rate of 0.3<span><math><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>, the mild damage strain threshold is estimated to be 0.2 – 0.3, while the moderate-to-severe damage threshold falls within 0.3 – 0.4, aligning closely with values reported in the literature. Additionally, the damage strain thresholds at 200<span><math><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> are consistent with those at 0.3<span><math><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>. The corresponding stress threshold at 200<span><math><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>ranges from 5.9 to 11.4 kPa for mild damage and from 11.4 to 22.8 kPa for moderate-to-severe damage. The findings of this study are expected to contribute to brain damage prediction.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102335"},"PeriodicalIF":4.3,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Switchable acoustic notch filter using a 3D-printed Helmholtz resonator array with bistable structures","authors":"Masahiro Fukuta ,&nbsp;Gakuto Kagawa ,&nbsp;Hidetoshi Takahashi","doi":"10.1016/j.eml.2025.102333","DOIUrl":"10.1016/j.eml.2025.102333","url":null,"abstract":"<div><div>Acoustic noise is a significant environmental issue that affects quality of life, including in workplaces. Therefore, the ability to selectively block specific sound frequencies is desired to maintain clear vocal communication. Electrically driven active noise control (ANC) is a common solution. However, its effectiveness is limited to frequencies above 1 kHz. On the other hand, passive noise control (PNC) has gained attention as an alternative solution due to its non-reliance on electricity. Among these, Helmholtz resonators (HRs) have recently attracted interest due to their ability to reduce acoustic noise at their resonant frequencies. Traditional HRs are generally limited to attenuating single frequencies, which restricts their ability to attenuate multiple frequencies using a single device. Herein, we propose an HR featuring a bistable structure that enables switching between two distinct attenuation frequencies. A bistable structure with two stable states allows for switchable configurations that enable volume changes. By integrating this bistable mechanism into an HR chamber, the resonant frequency can be altered by changing the chamber volume. Consequently, the proposed HR can attenuate two different frequencies between the concave and convex states. The proposed system was fabricated using a 3D printer with silicone material, and its bistable properties were evaluated. The measured resonant frequencies were 6.6 kHz in the concave state and 4.1 kHz in the convex state, resulting in dual-frequency noise reduction. In principle, the proposed HR design can be extended to a multi-stable mechanism that enables the attenuation of multiple frequencies.</div></div>","PeriodicalId":56247,"journal":{"name":"Extreme Mechanics Letters","volume":"77 ","pages":"Article 102333"},"PeriodicalIF":4.3,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}