The biological composition and spatial arrangement of the tissue’s constituents are directly related to its condition and function. Conventional inspection techniques such as optical microscopy and exogenous staining have limited ability to capture the heterogeneity and anisotropy of biological tissues. Here, we apply a commercial 2D digital image correlation (DIC) system integrated with a biaxial testing machine to quantitatively characterise the fibrous structure of biological materials. The approach applies a homogeneous biaxial stress field across the tissue and uses optical measurement of the resulting strain field to identify load-bearing collagen architecture. Under this loading condition, collagen bundles deform less than the surrounding matrix, so low-strain bands and their principal directions indicate ligament locations and orientations. The method was validated using an artificial anisotropic material and ex vivo skin, and was then applied to the human hip joint capsule to demonstrate its ability to characterise complex collagen networks. Testing of nine excised hip capsule specimens revealed the collagenous network and the confluence between its fibrous structures. The locations and orientations of seven ligamentous regions were detected and matched to previously published anatomical descriptions. Using strain as a quantitative measure of ligament anatomy further enabled extraction of local mechanical properties, including the tangent modulus, across the entire tissue in a single test. By combining a biaxial testing machine with a commercial 2D DIC system, this study demonstrates a practical and scalable approach for quantifying tissue structure-function relationships across whole tissues.

Quantification of Standing Cones in Elliptical Closures Using Digital Image Correlation.

Animal models and human 2D culture models have been instrumental for investigating skeletal muscle diseases and the development of therapeutics. However in vivo models and 2D cultures are limited in their translation to clinical application. These limitations are most evident through the success of myostatin inhibitors for improving mass and function in mice studies followed by unsuccessful clinical trials in patients with sarcopenia and Duchenne Muscular Dystrophy (DMD) (3-4). Although clinical trials of myostatin inhibitors have often reported increases in lean muscle mass, efficacy endpoints of improved muscle function are typically not achieved (3-4). Additionally, studies of age-related muscle atrophy, sarcopenia, have unique barriers to translation such as age-related gene expression changes and sex related muscle aging that is not conserved between species (1-2). Due to these challenges, our team developed a donor-derived 3D skeletal muscle platform housed in standard 24-well imaging plates. This platform was then utilized to investigate retention of sex- specific characteristics in 3D muscle cultures and the effectiveness of astaxanthin (ASTX) to improve contractile signaling and function in healthy and clinically sarcopenic 3D cultures. Initial characterization and validation were carried out in samples from healthy male and female donors. Contractile function recorded through digital image correlation (DIC) analysis during electrical stimulation was similar between male and female 3D muscles, but females displayed elevated type 1 fiber proportions compared to males. Female muscle also displayed elevated levels of OPA1 and TFAM protein levels along with decreased Akt signaling. Overall, female muscle exhibited a greater reliance on mitochondrial energy utilization and reduced protein synthesis indicating retention of sex-specific characteristics in 3D culture. Samples from young female and clinically sarcopenic female donors were studied in this platform for functional differences in force production, fatigue susceptibility, and contractile protein signaling following fatigue with or without astaxanthin antioxidant therapy. Astaxanthin was assessed at 1μM, 10μM, and 25μM in young cultures and only 10μM in sarcopenic cultures due to limitations in cell quantity for 7 days. Although there were no significant effects on force outputs or fatiguability for either group, 10μM rescued P38 and Akt signaling in the sarcopenic samples restoring levels to those exhibited by young DMSO- treated controls. Additionally, 10μM and 25μM in the young cohort suppressed Akt signaling indicating astaxanthin may negatively impact this critical pathway for exercise adaptation in healthy muscle. Although astaxanthin did not improve functional performance in the clinically sarcopenic or young female 3D muscle samples, clenbuterol was evaluated as a positive control for improving performance in young muscle and showed a nearly two-fold increase in both twitch and tetanic force response in 1μM treated samples compared to DMSO controls. These findings support the utilization of this muscle platform for assessing functional differences among drug treatments and untreated donor groups.

Photoacoustic technology can non-invasively obtain the temperature and pressure of tissues, holding great promise for applications in the laser thermal ablation of pigmented skin diseases. The coefficient of thermal expansion is the primary source of temperature sensitivity in photoacoustic technology. In this paper, a non-contact full-field strain measurement system based on temperature-variable three-dimensional digital image correlation is used to measure the variation of the thermal expansion coefficient of melanin in the retinal pigment epithelium layer of porcine eyes. It is found that the thermal strain of melanin exhibits non-uniformity and nonlinear increase in radial Angle and circular domain. Before the glass-transition temperature (49°C), the average coefficients of thermal expansion for concentric circular regions and different radial directions are 4.14 × 10-4 K-1 and 3.82 × 10-4 K-1, respectively. Approximating the thermal expansion coefficient of melanin with that of graphite leads to a large error, with a difference of two orders of magnitude.

Submaximal low-strain cyclic loading induces localized inelastic deformation & diminished energy dissipation in the anterior cruciate ligament.

Exploring the correlation between strain localization and carbide fracture using high-resolution digital image correlation

As an energy-absorbing viscoelastic material, shear stiffening elastomer (SSE) has been widely used in personal protection. To expand its applications, this study focuses on its dynamic response under shock wave loading. Based on the generalized Maxwell model and the time-temperature equivalence principle, a viscoelastic constitutive model of the material is established. Using Fluent software to construct a shock wave flow field, two-way fluid–structure interaction simulations are conducted, systematically revealing the influence of dynamic material boundaries on shock wave evolution. Combined with digital image correlation technique, the displacement field distribution of specimens is obtained experimentally. The results show that the shock wave propagation behavior of SSE is regulated by the shear stiffening gel (SSG)/methyl vinyl silicone rubber ratio. Increasing SSG content shifts the material from hyperelastic to viscoelastic, enhancing energy absorption and attenuating the reflected wave. When the wall shape changes from flat to curved, the stress wave front evolves from single to dual, with displacement becoming more concentrated, and the Mach stem height first increases and then decreases. Reducing material thickness increases the modulus and restricts displacement due to wave superposition, but delays the transition from Mach reflection to transitional regular reflection. This study systematically reveals the dynamic response mechanism of SSE under shock waves for the first time, providing a combined numerical and experimental basis for the design of protective structures based on viscoelastic materials and research on shock wave propagation.

A combined hardware and software method for the projection center calibration of the diffraction pattern.

Enhanced crack profile identification using physics-informed thresholding from digital image correlation techniques

Crack monitoring and damage evolution of HPC-NSC using integrated acoustic emission and digital image correlation techniques

Crack closure effect and fatigue crack growth behavior in laser repaired GH4169 superalloy based on digital image correlation technology

Digital Image Correlation (DIC)-Based Crack Strain Analysis of Concrete Containing Fly Ash and Silica Fume

Abstract Background The mechanics of the tricuspid valve are a critical determinant of its function and dysfunction. With millions suffering from tricuspid regurgitation, there is a pressing need to fill persistent knowledge gaps. A better understanding of the valve’s mechanics is essential for improving repair strategies and biomaterial-based replacements. Objective This study aimed to quantify the differences in strains within leaflets and between leaflets under both physiological and pathological loads. Methods We mounted six whole porcine heart preparations in vitro and measured full-field leaflet strains using three-dimensional digital image correlation. We varied peak transvalvular pressures between 20, 50, and 80 mmHg and applied three levels of annular dilation (0%, 30%, and 60%). Strain data were transformed into leaflet-specific radial and circumferential components, and compared statistically using linear mixed-effects models. Results Leaflet strains exhibited significant within- and between-leaflet heterogeneity. Strain magnitude increased with pressure but not with annular dilation. Additionally, strains were directionally dependent. Furthermore, we found that anterior and posterior leaflet strains near the annulus, in the belly, and near the free edge did not differ significantly. In contrast, strains in the septal leaflet increased from the annulus to the free edge. Conclusions These data provide spatially and directionally resolved strain maps of all three tricuspid valve leaflets in whole-heart preparations. By filling a critical knowledge gap, these findings may guide the design of biomaterials for valve repair and replacement.

Abstract This research elucidates the failure mechanisms of the heat-affected zone in welded aluminum alloys. Heat-affected zone softening, which leads to localized loss of strength and hardness, is a significant issue in welded aluminum components. This issue prevents the welded components from achieving their full load capacity, leading to premature failure in their heat-affected zone, despite acceptable weld quality. Accordingly, this study investigates the failure mechanisms of the heat-affected zone in non-heat-treatable 5754-H22 and heat-treatable 6082-T6 aluminum alloys. Samples are welded with different welding processes and heat inputs to clarify the influence of the welding procedure on the failure mechanism. Microstructural analyses, simulated thermal gradients using finite element, CALPHAD, and strength analytical approaches were employed to investigate the softening phenomenon. According to the results, the softening in the non-heat-treatable base metal was mainly due to dislocation recovery, while precipitation coarsening caused softening in the heat-treatable base metal. Tensile tests conducted in conjunction with digital image correlation revealed that the mechanical behavior of the welded joints followed that of their softened heat-affected zone. Furthermore, hardness-strength and stress-plastic strain empirical models were capable of predicting the deformation behavior of softened heat-affected zones, and thus, welded aluminum structures. However, the model parameters need to be adjusted for each specific base metal. Finally, autogenous laser welding showed reduced softening. However, it led to undercut defects and premature failure due to the absence of filler material, suggesting that using filler material in laser welding could be a viable solution to reduce softening in aluminum alloys.

Contractile engineered cardiac patches hold great potential for treating myocardial infarction, serving as biological ventricular assist devices (BioVADs). However, optimal design and attachment of cardiac patches remain insufficiently explored, although both are essential for the mechanical support of damaged hearts. This study presents a platform for personalized macroscale patches with a multi-zonal microarchitecture combining a regenerative zone for cell alignment, a stiff force transmission zone for load transfer, and an elastic attachment zone enabling integration. Based on computational modeling, the design is implemented using a custom G-code generator for melt electrowriting (MEW). Digital image correlation reveals up to a 2.6-fold strain difference between scaffold zones under physiological deformation, confirming zonal interplay. Biaxial testing with preconditioning shows scaffold mechanics replicating native myocardium properties up to 10% strain. For epicardial suture attachment, a reinforced outline enables shape-morphing and increases suture retention 2.16-fold. Dynamic BioVAD cultivation with fibrin-embedded cardiomyocytes significantly (p = 0.01) improves cell alignment versus controls. Finally, in a porcine myocardial infarction model, the BioVAD achieves complete epicardial attachment and vascular ingrowth within 7 days, compared to partial attachment in controls. This study highlights MEW as a versatile platform for tailoring cardiac scaffold mechanics to support tissue integration and cardiac function.

Abstract Research in the field of aortic biomechanics has significant importance for elucidating biomechanics-related pathogenesis and providing insights into the clinical diagnosis of aortic diseases. Aortic tissue is a collagen fiber-reinforced multilayer composite material with each layer indicating diverse hyperelastic and viscoelastic properties, whose alterations could be indicators of the formation and progression of aortic lesions. Up to now, numerous studies have employed diverse in vitro mechanical tests to derive the mechanical and structural properties of aortic tissues, reporting various testing and measuring systems for assessing aortic hyperelasticity and viscoelasticity. However, a new measuring device and algorithm procedure allowing three-layer hyper-viscoelastic and morphological parameter identification of the entire aortic wall is necessitated to provide a more comprehensive understanding of the anisotropic and layer-specific aortic biomechanics. In this study, a testing and measuring system integrating a desktop mechanical testing machine and a 90-degree mirror-assisted dual-surface digital image correlation (DIC) system was developed for a better understanding of the complex biomechanics of descending thoracic aortic tissues. Spatiotemporal dual-surface displacement and strain maps of the aortic intima and adventitia were reconstructed during uniaxial tension tests and subsequent stress relaxation tests. Based on the DIC measurements, the anisotropic and layer-specific hyper-viscoelastic properties and morphological features of the aorta wall were estimated using the finite element model updating (FEMU) method. This study provides a novel methodology for investigating the complex nonlinear biomechanics of aortic tissue, contributing insights into the anisotropy and layer specificity in biomechanical and morphological properties of the aortic wall during biomechanical modeling.

Enhancement of high-temperature digital image correlation measurement accuracy through noise suppression and feature guidance

Abstract Mechanosorptive creep strain (MCS) is a strain component that can dominate the overall deformation behavior of wood components under load and changing moisture. In this work, the MCS behavior of Norway spruce ( Picea abies ) tissues is investigated in the anatomical directions perpendicular to grain and different loading degrees (LD). The MCS is evaluated through a strain decomposition of the total strain, which is determined using a computer-controlled digital image correlation (DIC) system. It is shown that the common assumption of a scalar relation between mechanosorptive creep compliance (MCC) and the orthotropic, moisture-dependent elastic one is questioned by experiments.

This paper examines the applicability of the fracture forming limits (FFLs) derived from conventional monotonic upset compression tests for assessing the formability of non-monotonic strain loading paths. The work uses a simple test specimen subjected to various non-monotonic deformation histories, and combines experimental force measurements, digital image correlation, finite element analysis, and scanning electron microscopy (SEM) to characterize strain loading paths and crack opening mechanisms under varying testing parameters. Results demonstrate that non-monotonic strain loading paths can result in fracture strains that differ from those obtained through conventional monotonic bulk formability tests in the effective strain versus stress triaxiality space, depending on the considerations made in the transition between different loading stages. Consequently, reliance on monotonic test data may lead to inaccurate predictions of cracking in multi-stage industrial bulk forming processes.

Abstract Divertors constructed primarily from tungsten–copper (W/Cu) composites are essential components in magnetically confined fusion reactors, where they are subjected to extreme thermal loads. However, the W/Cu interface is particularly susceptible to fatigue-induced fracture under high heat flux (HHF) conditions. Modifying the interfacial configuration between tungsten and copper presents a promising approach to enhance the fatigue life of divertors. This study introduces a millimeter-scale serrated W/Cu interfacial design with finite element simulations and compares the fatigue performance of planar and serrated interfaces under cyclic thermal loading, with a focus on their thermomechanical behavior and failure mechanisms. The HHF experiments with digital image correlation and infrared thermography demonstrate that the serrated interface enhances fatigue life by about five times compared to the planar configuration under cyclic loading at 10 MW m −2 . After 1300 thermal cycles, metallographic observations reveal that the planar interface experiences severe shear-driven fracture, while the serrated interface maintains structural integrity with minimal damage. This enhancement in fatigue performance is attributed to the serrated geometry, which redistributes shear strain, concentrates deformation at serration tips, and induces compressive strains that suppress crack propagation. These findings provide the practical and economical optimization of W/Cu interfacial structures, supporting the development of more robust divertors for fusion reactors operating under more extreme thermal environments.