F. W. DelRio, B. D. Clarke, T. Huber, E. D. Reedy, S.J. Grutzik
{"title":"Post-Yield Compression Characterization of Epon 828/DEA Epoxy","authors":"F. W. DelRio, B. D. Clarke, T. Huber, E. D. Reedy, S.J. Grutzik","doi":"10.1007/s11340-026-01281-7","DOIUrl":"10.1007/s11340-026-01281-7","url":null,"abstract":"<div><h3>Background</h3><p>Epoxies are a family of glassy polymers which are widely used as adhesives, encapsulants, and composite matrix materials.</p><h3>Objective</h3><p>In this technical note, we examined the stress-strain response of Epon 828/DEA epoxy at temperatures ranging from room temperature to above the glass transition temperature.</p><h3>Methods</h3><p>In particular, the true stress-strain behavior at the reduced center of each specimen was estimated from digital image correlation and the deformation and stress state were compared to those from finite element analysis.</p><h3>Results</h3><p>The results suggested excellent repeatability based on multiple tests at each temperature and when compared to previous studies at a common temperature. Moreover, it was found that the material exhibited a constant ratio of bulk and shear response, a post-yield decrease in stress by a factor of approximately one-third, and a flat plastic plateau out through a strain of <span>(epsilon _{log}approx 0.45)</span> up to temperatures of 55 <span>(^{circ })</span>C.</p><h3>Conclusions</h3><p>The data indicate that the interfacial fracture toughness trends in previous work are broadly valid below the glass transition.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"739 - 744"},"PeriodicalIF":2.4,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738551","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":"Enabling High Resolution Strain Measurement at Elevated Strain Levels through the Use of Confocal Image Microscopy","authors":"W. Abuzaid, L. Patriarca","doi":"10.1007/s11340-026-01285-3","DOIUrl":"10.1007/s11340-026-01285-3","url":null,"abstract":"<div><h3>Background</h3><p>Digital Image Correlation (DIC) is widely utilized in experimental mechanics for full-field strain and displacement measurements due to its applicability across various length scales and its relatively low equipment cost. In materials science, high-resolution DIC enables detection of localized plasticity and deformation mechanisms, particularly at the grain or sub-grain scale. However, at elevated deformation levels, especially in coarse-grained materials, significant out-of-plane displacements introduce surface distortions that compromise image quality and correlation accuracy, challenges that become more severe under high magnification.</p><h3>Objective</h3><p>This study aims to evaluate the effectiveness of confocal microscopy in improving DIC measurement accuracy under high strain (> 5%) and high magnification conditions, compared to conventional optical microscopy.</p><h3>Methods</h3><p>Quasi-static deformation experiments were conducted on coarse-grained metallic samples exhibiting pronounced slip localization. Full-field strain measurements were obtained using DIC, with imaging performed via both optical and confocal microscopy. The correlation quality, error metrics, and image focus stability were assessed across increasing strain levels to quantify the impact of out-of-plane displacements on DIC accuracy.</p><h3>Conclusions</h3><p>Out-of-plane motions significantly degrade the accuracy of DIC when using conventional optical microscopy, particularly at higher strains and magnifications. In contrast, confocal microscopy effectively mitigates correlation errors by maintaining surface focus, enabling reliable strain measurements beyond 5% strain. These findings demonstrate the utility of confocal imaging in extending the practical limits of high-resolution DIC for local deformation analysis in materials with heterogeneous strain fields.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"727 - 738"},"PeriodicalIF":2.4,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738019","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}
B. Guan, J. Tao, L. Xu, D. Tan, P. Sun, J. Liu, Y. Shang, Q. Yu
{"title":"A DMD-Based Adaptive Modulation Method for High Dynamic Range Imaging in High-Glare Environments","authors":"B. Guan, J. Tao, L. Xu, D. Tan, P. Sun, J. Liu, Y. Shang, Q. Yu","doi":"10.1007/s11340-026-01276-4","DOIUrl":"10.1007/s11340-026-01276-4","url":null,"abstract":"<div><h3>Background</h3><p>The accuracy of photomechanics measurements critically relies on image quality, particularly under extreme illumination conditions such as welding arc monitoring and polished metallic surface analysis. High dynamic range (HDR) imaging above 120 dB is essential in these contexts. Conventional CCD/CMOS sensors, with dynamic ranges typically below 70 dB, are highly susceptible to saturation under glare, resulting in irreversible loss of detail and significant errors in digital image correlation (DIC).</p><h3>Methods</h3><p>This paper presents an HDR imaging system that leverages the spatial modulation capability of a digital micromirror device (DMD). The system architecture enables autonomous regional segmentation and adaptive exposure control for high-dynamic-range scenes through an integrated framework comprising two synergistic subsystems: a DMD-based optical modulation unit and an adaptive computational imaging pipeline.</p><h3>Results</h3><p>The system achieves a measurable dynamic range of 127 dB, effectively eliminating saturation artifacts under high glare. Experimental results demonstrate a 78% reduction in strain error and improved DIC positioning accuracy, confirming reliable performance across extreme intensity variations.</p><h3>Conclusion</h3><p>The DMD-based system provides high-fidelity adaptive HDR imaging, overcoming key limitations of conventional sensors. It exhibits strong potential for optical metrology and stress analysis in high-glare environments where traditional methods are inadequate.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"713 - 725"},"PeriodicalIF":2.4,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737886","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}
X. Xiaokun, X. Yifan, S. Shaoshuai, R. Xiaoli, W. Weitao, P. Jiangzhou, H. Jie
{"title":"Experimental Study on Dynamic Mechanical Behavior of Fully-Penetrating Cross-Jointed Rocks Under Biaxial Static-Dynamic Loading","authors":"X. Xiaokun, X. Yifan, S. Shaoshuai, R. Xiaoli, W. Weitao, P. Jiangzhou, H. Jie","doi":"10.1007/s11340-026-01268-4","DOIUrl":"10.1007/s11340-026-01268-4","url":null,"abstract":"<div><h3>Background</h3><p>The jointed rock mass near the tunnel face is subjected to a biaxial stress state prior to blasting excavation, and its dynamic response is significantly influenced by the joint structure. However, existing research has been limited in its ability to reveal the fracture and ejection mechanisms of fully-penetrating cross-jointed rock under biaxial static-dynamic coupled loads, which consequently hampers the accurate prediction and effective prevention of related disasters.</p><h3>Objective</h3><p>This study aims to develop an integrated experimental mechanics approach to reveal the dynamic response characteristics and fracture-ejection evolution mechanism of fully-penetrating cross-jointed rocks under biaxial static-dynamic coupled loading.</p><h3>Methods</h3><p>A biaxial Hopkinson bar system was used to apply static-dynamic coupled loading to a fully penetrating cross-jointed rock specimen, and its dynamic mechanical response under different stress paths was systematically studied. The digital image correlation (DIC) technique was used to capture the crack evolution and rock block movement in real time, revealing the fracture-ejection behavior.</p><h3>Results</h3><p>The dynamic peak strength of jointed rock increases significantly with the increase of intermediate principal stress. For example, when the loading rate is 4300 GPa/s and the <span>({sigma }_{2}^{0})</span> increases from 6 to 12 MPa, the dynamic peak stress of the jointed rock sample increases from 41.6 MPa to 107.6 MPa, but decreases with the increase of maximum principal stress, revealing the high sensitivity of jointed rock mass to stress path. The rock shell exhibits compression-slip-rotation coordinated deformation, revealing the continuous evolution mechanism of rupture-slip-ejection under joint control.</p><h3>Conclusion</h3><p>The proposed BHPB-DIC experimental methodology successfully verifies the synergistic regulatory effect of joint structure and stress path on the dynamic response of rock mass. The proposed experimental method and mechanistic understanding can provide a theoretical basis and experimental support for the identification of dynamic hazards in jointed rock mass.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 3","pages":"567 - 587"},"PeriodicalIF":2.4,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147559986","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}
S. Wang, M. Boåsen, G. Hultgren, M. Öberg, J. Faleskog
{"title":"An Inverse Finite Interval Method for Evaluating the True Stress–Strain Response from Uniaxial Tension Tests","authors":"S. Wang, M. Boåsen, G. Hultgren, M. Öberg, J. Faleskog","doi":"10.1007/s11340-026-01266-6","DOIUrl":"10.1007/s11340-026-01266-6","url":null,"abstract":"<div><h3>Background</h3><p>Analysis of finite elastic–plastic deformation requires a good constitutive description of the inelastic response. A key element is the hardening function, typically evaluated from nominal data obtained from a uniaxial tension test using the Bridgman correction method in the post-necking regime. However, the true stress–strain data obtained in this way depend crucially on the quality of the optical measurements. Based on modern and sophisticated technology, several new and demanding methods have emerged over the last decade to improve the accuracy of the Bridgman correction method.</p><h3>Objective</h3><p>To develop and validate an accurate method, combining standard experimental and numerical methods for the evaluation of the true stress–strain response of an elastic–plastic material.</p><h3>Method</h3><p>Experimental force-displacement data for a gauge section of a round bar specimen are used as input to an inverse finite interval (IFI) method to construct the true stress-strain response at discrete points by minimising the relative error between finite element simulations and experimental results.</p><h3>Results</h3><p>The inverse finite interval method is validated both numerically and experimentally. Synthetic force–displacement data are generated numerically for a set of power-law hardening materials, and the proposed method is then applied to reconstruct the true stress–strain curve. The method is proven to be robust, and reconstructed true stress–strain curves converge to the exact power-law function. Three markedly different steel grades are used for experimental validation by comparing the deformed geometry in the necking region between experimental and numerical results, showing good agreement.</p><h3>Conclusion</h3><p>The proposed inverse finite interval (IFI) method is an expedient and accurate method for evaluation of the true stress–strain curve from nominal data extracted from a uniaxial tension test.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 3","pages":"551 - 565"},"PeriodicalIF":2.4,"publicationDate":"2026-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11340-026-01266-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147559108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Nanoscale Ultrasonic Vibration and High-Speed Displacement Measurement with Heterodyne Interferometry and Cost-Effective Software-Defined Radio Phase Meter","authors":"T. D. Nguyen, N. Van Muoi, H. H. Hai","doi":"10.1007/s11340-026-01279-1","DOIUrl":"10.1007/s11340-026-01279-1","url":null,"abstract":"<div><h3>Background</h3><p>High-resolution ultrasonic displacement and vibration measurements are crucial in precision machining, advanced manufacturing, and materials characterization. However, achieving both high sensitivity and high acquisition speed typically requires expensive hardware, such as high-speed analog-to-digital converters (ADCs), field-programmable gate array (FPGA) platforms, or commercial lock-in amplifiers, which constrain flexibility and cost-effectiveness.</p><h3>Objective</h3><p>This study aims to develop and validate a low-cost, high-performance phase meter for heterodyne interferometric ultrasonic-vibration measurements, using low-cost software-defined radio (SDR) hardware and open-source software.</p><h3>Methods</h3><p>A < $50 RTL-SDR-based phase meter was designed using flexible beat-frequency up and down conversion to acquire heterodyne signals spanning from kilohertz to hundreds of megahertz. Digital quadrature demodulation, multi-stage filtering, and a computationally efficient quadri-correlator algorithm were implemented in GNU Radio to achieve unwrap-free and real-time phase extraction. System performance was evaluated through simulations and ultrasonic-vibration experiments using a double-path heterodyne interferometer and was directly benchmarked against a commercial lock-in amplifier.</p><h3>Results</h3><p>Simulations showed a phase resolution of ± 0.01° and stability of ± 0.06° at 20 kHz. This corresponds to sensitivity levels in the nanometer and sub-nanometer range. Experiments confirmed that the SDR-based system can reliably measure 20 kHz ultrasonic vibrations with peak-to-peak amplitudes of less than 500 nm. Furthermore, despite the limitations of an 8-bit ADC, the SDR achieved a signal-to-noise ratio (SNR) of 130 dB for MHz-level phase-alternating signals through effective digital processing gain. This performance exceeded that of previous SDR models and showed good agreement with the commercial lock-in amplifier.</p><h3>Conclusion</h3><p>The proposed SDR-based phase meter offers a unique combination of low cost, wide heterodyne compatibility, high SNR, and nanometer-scale resolution. These characteristics demonstrate that low-cost SDR hardware, when combined with advanced digital demodulation techniques, provides a practical and high-performance alternative to conventional lock-in and FPGA-based interferometric systems for real-time ultrasonic metrology.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"691 - 712"},"PeriodicalIF":2.4,"publicationDate":"2026-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737440","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}
T. Zhao, J. Chen, X. Wang, Y. Wu, H. Yan, P. Yip, B. Li, J. Zhou, Y. Lu
{"title":"Biaxial Micro-Mechanical Device (MMD) with Meta-Structure for In-Situ Mechanical Testing","authors":"T. Zhao, J. Chen, X. Wang, Y. Wu, H. Yan, P. Yip, B. Li, J. Zhou, Y. Lu","doi":"10.1007/s11340-026-01277-3","DOIUrl":"10.1007/s11340-026-01277-3","url":null,"abstract":"<div><h3>Background</h3><p>Low-dimensional materials are crucial for next-generation electronic systems but their size-dependent mechanical properties demand precise in situ mechanical characterization. Conventional platforms such as push-to-pull (PTP) micromechanical devices are limited by high fabrication costs, poor load–displacement linearity, and restriction to uniaxial stretching.</p><h3>Objective</h3><p>This study aims to develop a novel and stable micro-mechanical device (MMD) device with excellent load–displacement linearity, utilizing cost-effective fabrication method, and to investigate the biaxial tensile behavior of low-dimensional materials.</p><h3>Methods</h3><p>We designed a MMD with a meta-structure of chiral patterns, fabricated using standard silicon wafers and wet etching, which reduces production costs and enables batch manufacturing, and did the uniaxial and biaxial tensile test.</p><h3>Results</h3><p>This design reduces stretching stress, enhancing stability, load–displacement linearity, and experimental repeatability. Uniaxial Scanning electron microscope (SEM) tensile tests confirmed no bulk rotation after 2000 nm displacement, while the gap of 3 μm was shown to be compatible with in situ tensile testing, and cyclic loading experiments validated repeatability. As a proof of concept, in situ tensile testing of ZnO nanowire revealed a strain of approximately 5%. Furthermore, a biaxial tensile MMD based on the meta-structure was demonstrated, with transverse and longitudinal displacements remaining nearly identical within 3 μm.</p><h3>Conclusion</h3><p>This MMD provides a cost-effective solution and tailorable platform for<i> in situ</i> mechanical characterization of low-dimensional materials, with the capability of biaxial stretching.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"681 - 690"},"PeriodicalIF":2.4,"publicationDate":"2026-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11340-026-01277-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Ogawa, T. Hidaki, H. Tatebayashi, M. Hayashi, K. Kadoi, D. Shiozawa, T. Sakagami, E. Yukutake
{"title":"Fatigue Limit Estimation Based on Dissipated Energy for Al/Al and Al/Steel Friction Stir Welding Joints","authors":"Y. Ogawa, T. Hidaki, H. Tatebayashi, M. Hayashi, K. Kadoi, D. Shiozawa, T. Sakagami, E. Yukutake","doi":"10.1007/s11340-026-01283-5","DOIUrl":"10.1007/s11340-026-01283-5","url":null,"abstract":"<div><h3>Background</h3><p>Friction stir welding was developed as a joining technique for lightweight alloys, such as aluminum, and has been increasingly recognized for its capability to join dissimilar materials in multi-material structures. The practical application of friction stir welding requires high levels of safety and reliability.</p><h3>Objective</h3><p>This study introduces a rapid method for estimating the fatigue limit of friction stir welding using infrared thermography. It specifically focuses on energy dissipation due to localized plastic deformation and evaluates the fatigue properties of friction stir welding joints based on this dissipated energy.</p><h3>Methods</h3><p>Temperature variations by dissipated energy and their phase difference were recorded during a staircase stress level test, where stress amplitude increments occurred in short cycle steps on the specimen. In the estimation of the fatigue limit of joint, the temperature variation by dissipated energy is categorized into two groups by the domain decomposition method using the least-squares approximation.</p><h3>Results</h3><p>The joints were observed to fracture at locations where temperature variations due to dissipated energy were locally elevated. The estimated fatigue limits calculated from these temperature variations were found to closely align with the actual fatigue limits. Thus, this study demonstrates that the fatigue limit of friction stir welding joints can be effectively estimated by monitoring the increases in temperature variation caused by dissipated energy.</p><h3>Conclusions</h3><p>The fatigue limits of aluminum alloy-to-aluminum alloy and aluminum alloy-to-steel friction stir welding joints can be estimated by observing the increase in temperature variation by dissipated energy.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"665 - 679"},"PeriodicalIF":2.4,"publicationDate":"2026-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11340-026-01283-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Full-Field Out-of-Plane Displacement Measurement of Plate Structures by Monocular Parametric Homography and Finite-Element-Based Digital Image Correlation","authors":"P. Xie, Z.-R. Lu, J. Liu, L. Wang","doi":"10.1007/s11340-026-01282-6","DOIUrl":"10.1007/s11340-026-01282-6","url":null,"abstract":"<div><h3>Background</h3><p>Vision-based measurement methods are nowadays widely used in structural tests due to their non-contact nature and full-field measurement capability. Typically, out-of-plane motion measurements require two or more cameras to compensate the depth information, with the additional cameras and synchronization systems increasing the overall cost.</p><h3>Objective</h3><p>To propose an efficient monocular vision method for measuring the full-field out-of-plane displacement of plate structures.</p><h3>Methods</h3><p>The image area of interest is first discretized into finite elements, and a full-field warp function is built by interpolating the out-of-plane nodal displacements using finite element shape functions. Subsequently, the parametric homography is combined with the finite element-based warp function to relate image motion to out-of-plane displacement. The nodal displacements are then determined by matching the deformed and un-deformed image regions within the digital image correlation (DIC) framework.</p><h3>Results</h3><p>Numerical simulations confirm that the measurement error remains at a low level under appropriate element size and camera configurations. Experimental validation on the out-of-plane vibration of a steel plate further demonstrates a close agreement with the laser vibrometer results in both displacement and mode frequency/shape measurements.</p><h3>Conclusions</h3><p>The proposed monocular method enables cost-effective measurement of full-field out-of-plane displacement, demonstrating its potential as a practical tool for out-of-plane vibration analysis and modal identification of plate structures.</p></div>","PeriodicalId":552,"journal":{"name":"Experimental Mechanics","volume":"66 4","pages":"647 - 664"},"PeriodicalIF":2.4,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738688","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}