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Highlights This study examines the effects of multilayering in sandwich panel composite structures with different corrugated core configurations under quasi‐static indentation loading. The panels were fabricated using woven glass fibers and epoxy resin via the Vacuum Infusion Process. Experiments were conducted using two hemispherical cylindrical indenters with a diameter of 20 mm (ID = 20 mm) and 10 mm (ID = 10 mm) and the behavior of the composite structure in terms of contact force and fracture mechanisms for different core corrugations (square and butterfly) were investigated in two ways with foam and without foam. The experimental results demonstrate that, among corrugated core geometries without foam, butterfly cores outperform square cores in terms of structural strength, maximum force, moment force, energy absorption, specific energy absorption, and displacement until full indentation. Moreover, the butterfly core shows a higher peak load and different failure mechanisms compared to the square core. Under loading with a 10 mm indenter, the butterfly core without foam only experienced perforation in the loading area, without fracture completely. Also, adding foam did not change failure mechanisms and mechanical behavior in the butterfly geometry. However, in the square geometry, foam filled gaps between the core, preventing fracture completely and leading to only perforation in the loading area, unlike the specimen without foam. The visual analysis during the quasi‐static indentation process revealed several significant damage mechanisms, including matrix cracking, fiber breakage, delamination, buckling and crushing of cell walls, damage to top sheets, core separation, and complete indentation of the samples. Delamination and indentation failure mechanisms were seen on the butterfly core. Skin indentation and rib fracture failure mechanisms were seen on the square core. Butterfly corrugated cores revealed the best performance without/with foam. The core shape was more effective on the strength than the foam addition. [ABSTRACT FROM AUTHOR]

Contact damage of glass is one of the most crucial issues for glass products. To develop strong and tough glass products and to compare damage resistance among glass compositions, a simple method for evaluating the mechanical response of glass during contact is required not only for glass mechanists but also for glass customers and suppliers. Although it is well known that the quasi‐static Vickers indentation test is one of the simplest and most useful methods to evaluate hardness and brittleness in glass, the indentation response of glass under the indenter at higher impact velocities remains to be quantitively understood because of the difficulty of measurement and limited experimental works. In this study, therefore, the dynamic indentation behavior of soda‐lime glass is evaluated by using a lab‐made free‐drop indentation set‐up with the coils for detecting electromotive forces (EMFs). The cono‐spherical indenter made of tungsten carbide attached with a neodymium magnet was employed to generate the EMFs when the indenter passed through the coils located near the glass sample. The impact load versus indentation depth curve during the impact within a few tens of microseconds was successfully obtained both for an elastic contact and for an inelastic contact. Under an elastic condition, where no residual indent nor any cracks were left on the glass surface after the test, it is confirmed that there is almost no hysteresis in the impact load versus indentation depth curve and that the curve can be reproduced by the Hertzian analytical solution. Under an inelastic condition, on the other hand, it is found that the hysteresis in the impact load versus indentation depth curve stems from inelastic phenomena, such as plastic deformation (shear flow and/or permanent densification) and cracking. These results suggest that the dynamic indentation technique based on electromagnetic induction phenomena is a useful and effective tool for evaluating the mechanical responses of glasses during the impact. [ABSTRACT FROM AUTHOR]

Background: Residual stresses exist in many manufactured materials and must be measured and taken into account for safe structural design. Established residual stress measurement methods are either destructive or require substantial material-dependent calibration. Objective: The present work is aimed at developing an indentation-based method for measuring residual stress that causes minimal specimen damage, does not require a stress-free reference specimen, and has the capability to identify both the size and direction of the surface residual stresses. In this initial study, the simpler case of equi-biaxial stresses is addressed in preparation for subsequent general stress evaluations. Methods: The surface displacements around an indentation made by a conical indenter are measured using digital image correlation. The residual stresses are then identified by comparison to the results of a finite model of the indentation process. Results: The proposed method is shown to 2–5 times more sensitive to the presence of residual stresses than other commonly used indentation methods, particularly for materials with low Hollomon exponent n. In example measurements, axi-symmetric residual stresses were determined within 8% of the material yield stress. Conclusions: The initial study presented here successfully considered the equal-biaxial stress case. The proposed method is attractive for future development because it gives directional information and therefore can be extended to the general non-equal-biaxial case. [ABSTRACT FROM AUTHOR]

Mechanical properties of glass are critical for technical applications, thus comprehending the material response to mechanical tests is of great importance. In this study, we employ the nanoindentation combined with nanoscale infrared (nano-IR) spectroscopy combined with scattering-type scanning near-field optical microscopy (s-SNOM) and ToF-SIMS, to elucidate the nanoindentation rate dependence of plastic deformation of soda lime silicate glass. Experiment results show that the nanohardness and elastic modulus of soda lime silicate (SLS) glass exhibit a strong dependence on loading rate, while those of fused quartz (FQ) shows a much weaker dependence. The residual indent volume at fast loading conditions is smaller for SLS glass than FQ; but as the loading rate decreases, the residual indent volume of FQ and SLS glass becomes similar. The indent volume of SLS glass after sub- T g annealing (reverting subsurface densification) shows negligible dependence on the loading rate, suggesting that the densification of SLS glass is strongly enhanced at lower indentation rate, but the shear flow is independent or weakly dependent. Using nanoscale infrared spectroscopy and ToF-SIMS techniques, the sodium ion migration in SLS glass surface in the indent is found to be associated with the subsurface densification. These results suggest the possible role of highly mobile sodium ions on in nano- and micro-scale plastic deformation behavior of SLS glass. [ABSTRACT FROM AUTHOR]

A molecular dynamics model of a five-component coating based on the TiAlTaSiN system is proposed. A superposition of interatomic potentials is chosen to describe the interaction between the atoms of the system. The superposition includes both the available interatomic potentials and those calculated on the basis of the electron density functional theory. A molecular dynamics simulation is used to analyze the resistance of the developed coating model to thermal and mechanical loading. The influence of the concentration of alloying inclusions and the crystallographic orientation of the grains of this multi-component coating with respect to the applied load on its strength and deformation properties is investigated. A qualitative agreement between the simulation results and the experimental data is demonstrated. [ABSTRACT FROM AUTHOR]

Comprehensive mechanical testing of steels provides important information about the possibilities of their use under different processing and operating conditions. Comparison of test methods with each other, taking into account the development of plastic deformation and fracture analysis, is an urgent task for materials certification. The present work is devoted to the study of the characteristics of the response to deformation of high-manganese steels (13 and 22 wt.% Mn steels) in comparison with the behavior of high-entropy Cantor alloy during scratching, tensile, and microhardness tests. The plasticity of the materials and the nature of their destruction were assessed by the surface deformation relief and fractography. Analysis of the structure during scratch testing made it possible to assess the degree of plasticity of the materials and relate it to the results of tensile tests and the nature of destruction. The steel with 13 wt.% Mn (Hadfield steel) the destruction of which occurs by the quasi-viscous mechanism has the lowest ductility. The highest ductility has the Cantor alloy characterized by the viscous fracture mechanism. The Hadfield steel has the highest hardness of all materials studied, while the Cantor alloy has the least hardness. The research results lay the basis for the possibility of recalculating the mechanical characteristics from different tests, taking into account the implemented stress state scheme and processes of structural changes during deformation. [ABSTRACT FROM AUTHOR]

Stepped repair, scarf patch repair, and patch repair are important in terms of repair techniques. The composite plate repair process starts after damage zone determination either by the unaided eye or nondestructive testing (NDT) techniques. This study investigates design cases for the stepped repairs of damaged fiber-reinforced composite materials. Before preparing steps for repair, the material around the damage zone is removed. In the stepped repair, it needs extra care to ensure that the repair plies overlap each other properly in the cut. Different cases are performed considering different step sizes. 5, 10, and 15 mm step sizes are used. The damages are given to the produced fiber-reinforced composite laminates using the Quasi-static indentation (QSI) method. Using QSI high-velocity impact simulation can be done. To get damage characteristics well-known damage test method is issued. Different span-to-punch diameter ratio (SPR) values were also used to compare different damage sizes. As a result, High ratio strength recovery was obtained using the longer step size. Maximum penetration force was reduced by nearly % 6-7 and maximum stress reduction was obtained by nearly % 8-9 for the 15 mm step size repaired composites. Among the all cases, case-1 has the highest strength recovery and case-5 has the lowest. For SPR 2, The average ultimate force value of specimens repaired with case-1 was maintained at nearly 94%. For SPR 4, repairs carried out using case-1 maintain more than 95% of damage resistance. [ABSTRACT FROM AUTHOR]

Background: Lithium penetration-induced fracture within solid electrolytes (SEs) is a major issue hindering the commercialization of solid-state lithium-ion batteries (SS-LIBs). Such fracture has been frequently observed during electrochemical plating of lithium (Li)-metal anodes, but its mechanistic origin is still largely unclear. Objective: We present the first quantitative operando analysis of the fracture characteristics of a model SE material under battery-relevant electrochemical cycling conditions. Methods: Full-field deformation during Li deposition-induced cracking of garnet-type LLZTO was measured using the digital image correlation (DIC) method. The obtained displacement data were denoised via equilibrium smoothing, and then fitted to the linear elastic asymptotic crack-tip field to extract the electrochemical fracture toughness values under different current densities. Results: The physics-based equilibrium smoothing method demonstrated effectiveness in enhancing the accuracy of DIC measurements. The electrochemical fracture toughness obtained was substantially lower than the mechanical fracture toughness of the same material determined through indentation, attributed to combined effects of electrochemical embrittlement and a transition in fracture mode from intergranular to transgranular. Conclusion: The discrepancy between the two types of fracture toughness suggests that electrochemical cycling could have a significant impact on the fracture mode and resistance of a solid electrolyte. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were conducted to explore nanoindentation-induced martensitic transformation in NiTi shape memory alloys. Three atomic compositions and two indenter sizes were considered. During loading, the B2 structure underwent martensitic transformation to the B19' structure, accompanied by atomic rearrangement in the form of bands. After unloading, a portion of the B19' phase underwent reversible transformation, while the remainder remained in the form of bands, resulting in residual strain. This effect was accentuated by the more localised deformation promoted by the smaller indenter. The influence of atomic composition was observed not to play a key role in the mechanical and structural properties, contrary to previous reports on tension and compression tests. Our findings shed light on the intricate interplay of factors influencing the mechanical performance of NiTi shape memory alloys at the atomic scale, providing crucial insights for the design and understanding of such materials. [ABSTRACT FROM AUTHOR]

Instrumented indentation technique provides a simple and quick means to investigate mechanical properties such as hardness and elastic modulus near the material surface. However, accurately predicting plastic pileup/sink-in during indentation remains a hurdle in calibrating real contact depth, affecting precise material property evaluation, especially in metallic materials. This study utilizes machine learning on extensive finite element analysis (FEA) data to exclusively predict elastic modulus from indentation curves. Leveraging comprehensive FEA data from sharp and spherical indentations across diverse material properties, our neural network-based models showcase impressive accuracy, achieving approximately 0.65 and 1.72% Mean Absolute Percentage Error for spherical and sharp indentations, respectively. Furthermore, we address the impact of indenter geometry imperfections on prediction accuracy. Through data normalization and subsequent transfer learning, we effectively minimize the MAPE deviation in predicted elastic modulus between results obtained from perfect and imperfect indenters. [ABSTRACT FROM AUTHOR]

The crashworthiness of electric vehicles depends on the response of lithium-ion cells to significant deformation and high strain rates. This study thoroughly explores the mechanical behavior due to damage of lithium-ion battery (LIB) cells, focusing on Lithium Nickel Manganese Cobalt Oxide (NMC) and Lithium Iron Phosphate (LFP) types during both quasi-static indentation and dynamic high-velocity penetration tests. Employing a novel approach, a hemispherical indenter addresses gaps in stress–strain data for pouch cells, considering crucial factors like strain rate/load rate and battery cell type. In the finite element method (FEM) analysis, the mechanical response is investigated in two stages. First, a viscoplastic model is developed in Abaqus/Standard to predict the indentation test. Subsequently, a thermomechanical model is formulated to predict the high-speed-impact penetration test. Considering the high plastic strain rate of the LIB cell, adiabatic heating effects are incorporated into this model, eliminating heat conduction between elements. Addressing a notable discrepancy from prior research, this work explores the substantial reduction in force observed when transitioning from a single cell to a stack of two cells. The study aims to unveil the underlying reasons and provide insights into the mechanical behavior of stacked cells. [ABSTRACT FROM AUTHOR]

Chemical strengthening of glass represents a standard technology for fabricating damage‐resistant protective covers. Still, little attention has been paid to modifications in the tribological properties of ion‐exchanged glass surfaces. This work reports on scratch testing of a chemically strengthened alkali‐borosilicate thin glass. Diffusive Na+/K+‐ion exchange produces a residual surface compressive layer with compressive stress of 200–340 MPa and layers depths between 16 and 50 µm, depending on exchange temperature and treatment time. This leads to notable changes in the surface mechanical properties, such as an increase in surface Young's modulus, indentation, and scratch hardness. Surprisingly, the Na+/K+‐ion exchange is shifting the onsets of scratch‐induced microcracking and microcracking to lower normal loads. The accelerated buildup of lateral indentation stress in glasses with high scratch hardness was found to be responsible for the lower threshold loads of microcracking and abrasive wear in chemically strengthened alkali‐borosilicate thin glass. [ABSTRACT FROM AUTHOR]

Understanding the properties of the constituent elements within Ceramic Matrix Composites (CMCs) is of paramount importance. During manufacturing process, the properties of the starting phases can undergo changes or be influenced by their interactions. In this work, micro-indentation analysis was used to selectively characterize matrix and fiber of Ultra-High-Temperature CMCs (UHTCMCs) produced by slurry infiltration of unidirectional pitch-derived carbon fabrics and sintering. A loading pre-factor was exploited to differentiate between indentations made on the matrix and those made on the fibers. The ZrB 2 -based matrix showed typical elasto-plastic behavior, leaving a residual imprint, with hardness and a modulus of 11.5 GPa and 220 GPa, respectively, consistent with its porosity, cracks and fiber content. Conversely, the fiber displayed no residual imprint and displayed hardness and modulus values of 1.1 GPa and 40 GPa, respectively. These values were attributed to the graphitic sheets buckling and residual thermal stress. Furthermore, the indentations indicated a transition zone between the matrix and fiber affecting mechanical behavior. [ABSTRACT FROM AUTHOR]

This work discusses the predictable control of plasma-assisted physical vapor deposition (PVD) of coatings. The multiple process parameters and the instability of the nonequilibrium ion plasma system create substantial obstacles to the wide industrial application of promising multicomponent functional coatings. Here we propose a solution to this problem, which includes: creation of a database of diamond-like carbon (DLC) coatings to identify a limited set of adjustable process control parameters, determination of how these parameters affect the coating properties, analysis of the revealed effects using statistical methods and neural network algorithms, and use of the results for the predictable tuning of specified coating properties. The object of research is original DLC coatings whose structure is stabilized with nitrogen instead of conventionally used hydrogen. The experimental database of DLC coatings is created based on our previous studies and includes structural, morphological and architectural characteristics of coatings, various types of substrates, sublayers, physical, mechanical and tribological properties, and various combinations of coating deposition parameters. A specific problem is solved to determine the influence of deposition parameters such as chamber pressure P, stabilizer content (% nitrogen), ion flux rate (coil current λ) and deposition time t on hardness H and elastic modulus E of coatings. Based on the results obtained, the deposition parameters are optimized so as to obtain predictable strength values of the formed carbon coating. The optimization procedure is developed using both classical statistical methods and modern algorithms of ridge regression, randomized trees (ExtraTrees), and a fully connected neural network (multilayer perceptron MLP). [ABSTRACT FROM AUTHOR]

Mechanical properties of Li10.35Ge1.35P1.65S12 (LGPS) solid electrolytes with different grain sizes were investigated via indentation tests. Hand-milled LGPS (HM LGPS, d50: 1.32 μm) and wet-milled LGPS (WM LGPS, d50: 0.46 μm) powders were uniaxially pressed to obtain pellet samples. The HM LGPS and WM LGPS pellets had a similar bulk density of 1.63 g cm-3. At the initial loading/unloading, the WM LPGS pellet showed a large deformation owing to a decrease in cavities compared with the HM LGPS. In the subsequent cycles, both pellets exhibited elastic deformation behavior in the pressure range up to 20 N. The elastic modulus and relative residual depth of HM LGPS and WM LGPS were 21.7 GPa and 15.0 GPa and 0.75 and 0.71, respectively. This result revealed that WM LGPS is more elastically deformable and less plastically deformable than HM LGPS, which could be associated with the grain boundary strengthening interpreted by the Hall-Petch relation. Based on these mechanical properties, the superior cycle stability at the In-Li electrode/WM LGPS electrolyte interface during charging/discharging was discussed. Controlling the mechanical properties of sulfide solid electrolytes by the grain size is important for suppressing physical degradation in all-solid-state batteries. [ABSTRACT FROM AUTHOR]

Using instrumented indentation testing, we explore the measurement of surface residual stress in H-section steel beams produced through the quenching and self-tempering (QST) process. We establish a significant correlation between the plastic pile-up behavior observed during indentation and the magnitude of surface residual stress. We thoroughly clarify the distribution of plastic pile-up and residual stress, linking their variations to non-uniform phase transformation and changes in mechanical properties resulting from the QST process. Moreover, we employ an indentation curve analysis to evaluate surface residual stress, obviating the need for direct measurements of pile-up height. These findings facilitate the measurement of non-uniform surface residual stress in H-section beams, crucial for ensuring structural integrity, yet challenging to measure in situ.

Time-dependent in-plane deformation in PMMA indentation is investigated via two-layer visco-plasticity model (TLV). The parameters of TLV model for PMMA were calibrated for tensile specimens using finite element analysis (FEA) and an optimization approach. The TLV model with the calibrated parameters was then employed to simulate nano- and micro-indentation behaviors including creep, relaxation, and other responses under various test conditions. Comparisons of experimental and FEA indentation load-depth curves showed agreement except the last unloading segment. This discrepancy was attributed to the inability of TLV model in replicating the delayed elastic recovery. In addition, deformation recovery with in-plane displacement (ui) was observed over a few days after indentation load removal. The characteristics of ui recovery and the factors influencing its magnitude are discussed. The proportionality of relative ui recovery rate prominently featured in the viscoelastic properties of PMMA, regardless of indentation history.

Thermal barrier coatings (TBCs) play an important role in the thermal protection of alloy components in high temperature industries. Accurately characterizing and extracting mechanical properties of TBCs are crucial for structural design, performance optimization, failure prediction and lifespan assessment. Indentation test is an effective method for experimentally obtaining the mechanical properties and provides valuable insights into the elastic, plastic and fracture behaviors of TBCs at elevated temperatures. This paper aims to provide an overview of indentation mechanical evaluation of TBCs, including the mechanical properties at different temperatures, the mechanical property anisotropy, the microstructural and mechanical behavior under thermal exposure and/or thermal cycling, as well as the comparison of functional performance between conventional and nanostructured TBCs. Furthermore, this paper points out the main challenges and future directions from indentation investigations of TBCs. Finally, this paper is summarized and prospected.

One of the current and widely used non-destructive testing methods for monitoring and determining the elastic properties of materials is nanoindentation. In this case, to interpret the test results, a non-trivial task arises of constructing an adequate mathematical model of the indentation process. As a rule, in many cases, analytical formulas are used that are obtained from an elastic linear formulation of problems about the introduction of a non-deformable stamp into a homogeneous elastic half-space. Currently, the numerical formulation of the problem makes it possible to obtain and use a numerical solution obtained taking into account the complete plastic nonlinear behavior of the material. In this work, a study of contact problems on the introduction of a spherical and conical indenter into an elastoplastic homogeneous half-space was carried out. To verify the numerical solution, the problem of introducing a spherical and conical indenter into an elastic homogeneous half-space was also solved and compared with known analytical solutions. Issues of convergence and tuning of numerical methods, the influence of plasticity and the applicability of analytical solutions are explored. Problems are solved numerically using the finite element method in the Ansys Mechanical software package.

A dual flat-spherical indentation (DFSI) method is proposed for evaluating elastic-plastic properties of metallic materials under equi-biaxial residual stress (RS) state. DFSI consists of two indentation steps: (step I) performing flat indentation (FI) on a specimen having significant presence of residual stress, and (step II) performing spherical indentation (SI) at the center of residual imprint generated by the FI (step I). Indentation load-depth curve in conventional single spherical indentation (SSI) generally varies with RS, while the load-depth curves of SI step in DFSI are almost identical even under significant RS; this is attributed to stress redistribution during the preceding FI step. A set of FE analyses are performed for a wide range of properties of general metals. Regression-based mapping functions are established for evaluating the elastic-plastic properties from the SI data of step II. Finally, the proposed method is validated by performing DFSI experiments on the mechanically stressed SM45C and SS400 specimens.

In this study, the self‐healing capacity of Titanium Aluminum Carbide (Ti2AlC, MAX phase) was investigated. Bulk coin samples were fabricated to evaluate the self‐healing capacity at different temperatures (1000, 1200, and 1400°C). The extensive self‐healing capacity of Ti2AlC was confirmed on larger quasiplastic damage (diameter ≥1 mm) and radial cracks by covering and filling of oxides such as titanium oxide, aluminum oxide, and aluminum titanate oxide. Although the mechanical properties of Ti2AlC after healing are similar or improved relative to the Ti2AlC before healing at the microscale, some properties of Ti2AlC after introducing larger damage and healing at 1400°C showed reduced values due to excessive oxide formation on the surface. For example, the strength of Ti2AlC healed at 1400°C exhibited 151.4 MPa, which is relative to the original strength of 298.3 MPa. Alternatively, the mechanical properties such as strength, hardness, toughness, and relative modulus of elasticity of Ti2AlC healed at 1000 or 1200°C and were restored to their original strength after healing. These findings suggest that Ti2AlC can be used as a healing agent for high‐temperature applications, such as environmental barrier coating for gas turbine hot‐gas components. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the indentation behavior of thin AlSi10Mg specimens manufactured using Selective Laser Melting (SLM) in the as-built condition along with two post-treatments, namely solution heat treatment and artificial aging. Four different thicknesses of 1.0 mm, 1.5 mm, 2 mm, and 2.5 mm of SLM specimens, with the different post-treatments, underwent standardized Rockwell hardness tests using a spherical indenter to determine their hardness values and assess the impression using a stereo microscope and scanning electron microscope (SEM). The as-built specimens showed a trend of smaller indentation depths with increasing specimen thickness, and finally creased with 0.1547 mm depth at 2.5 mm. However, the post-treatments altered the behavior of the specimens to a certain degree, giving larger experimental indentation depths of 0.2204 mm, 0.1962 mm, and 0.1798 mm at 1.0 mm, 1.5 mm, and 2.5 mm thickness, respectively, after solution heat treatment. Artificial aging showed a general decrease in indentation depth with increasing specimen thickness in contrast to solution treatment, and resulted in depths of 0.1888 mm and 0.1596 mm at 1.0 mm and 2.5 mm thickness. Furthermore, a material numerical model was made using stress–strain data on ANSYS Workbench to develop a predictive model for the indentation behavior of the specimens in contrast to experimentation. Under multi-linear isotropic hardening, the Finite Element Analysis (FEA) simulation produced indentation geometry with an average accuracy of 95.4% for the artificial aging series. [ABSTRACT FROM AUTHOR]

The development of urbanization and the resulting expansion of residential and transport infrastructures pose new challenges related to ensuring comfort for city dwellers. The emission of transport vibrations and household noise reduces the quality of life in the city. To counteract this unfavorable phenomenon, vibration isolation is widely used to reduce the propagation of vibrations and noise. A proper selection of vibration isolation is necessary to ensure comfort. This selection can be made based on a deep understanding of the material parameters of the vibration isolation used. This mainly includes dynamic stiffness and damping. This article presents a comparison of the method for testing dynamic stiffness and damping using a single degree of freedom (SDOF) system and the method using image processing, which involves tracking the movement of a free-falling steel ball onto a sample of the tested material. Rubber granules, rubber granules with rubber fibers, and rebound polyurethanes were selected for testing. Strong correlations were found between the relative indentation and dynamic stiffness (at 10–60 MN/m3) and the relative rebound and damping (for 6–12%). Additionally, a very strong relationship was determined between the density and fraction of the critical damping factor/dynamic stiffness. The relative indentation and relative rebound measurement methods can be used as an alternative method to measure the dynamic stiffness and critical damping factor, respectively. [ABSTRACT FROM AUTHOR]

CO2 pre-injection fracturing is a promising technology for shale reservoirs development, with multiple advantages for improving the complexity of fractures, the production of crude oil, and the sequestration of CO2. Previous research mostly focused on the CO2 effect on macroscopic mechanical properties of shale. However, there are many phenomena closely related to shale micro mechanical behavior. Therefore, this study presents a systematic investigation into the effects of CO2 on both macro and micro mechanical properties, as well as pore-fracture structures during CO2 pre-injection fracturing in shale reservoirs. The results show that CO2 can significantly decrease the tensile strength, uniaxial compressive strength, and elastic modulus of shale. With the increasing CO2 treatment time, the macro mechanical properties of shale decrease gradually. The microscopic experiments show that this significant decrease may be due to two mechanisms. The first is the significant decrease in the micro-mechanical properties of shale. The results of indentation analysis show that the microscopic elastic modulus and hardness of shale decrease by 51.3% and 63.3% after CO2 treatment. The second is the changes of the original shale framework. Pore-fractures structure analysis showed that after CO2 treatment, a large number of dissolution pores are generated in the shale matrix. Meanwhile, there are propagation of original fractures and opening of structural weak planes, which lead to the form of new fractures. Under the action of these two mechanisms, the macro mechanical strength of shale is reduced significantly. Therefore, in the field application, proper soaking following CO2 injection could lead to a significant overall reduction in mechanical strength, potentially lowering formation breakdown pressure, easing the requirements for treatment equipment, and enhancing fracturing effects. [ABSTRACT FROM AUTHOR]

Micro-/nano-indentation has become prevalent in evaluating the mechanical characteristics of biological samples, such as cells and tissues. However, the existing contact models describing conical indentation ignore the joint effects of surface energy and substrate, and consequently cannot accurately extract the Young's modulus of biological samples deposited on substrate. Through finite element methods, we examine the conical indentation of biological films on substrates while taking surface energy into account. Based on the dimensional analysis, the explicit relationship between load and indentation depth is achieved for films with their moduli varying from 0.001 to 100 times that of the substrate. If the classical Sneddon's model was employed to analyze the load-depth data, the measured modulus could reach 18 times the real modulus for films on harder substrates, but only 4% of the real modulus for films on softer substrates. Meanwhile, in micro-/nano-indentations, neglecting the contribution of surface energy would result in an overestimation of the Young's modulus of films depending on the contact size. The analytical expression provided here can be utilized to precisely deduce the mechanical characteristics of biological films deposited on substrate from the load and indentation depth data of a conical indentation. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the effect of ball indentation on fatigue crack growth. The main objective is to assess the effectiveness of indentation, particularly its influence on the J-integral, as a fracture criterion governing fracture toughness. Using the finite element method in Abaqus 6.14, we analyzed the residual stresses induced by indentation at different positions along the predicted line of crack propagation and calculated the J-integral. The results highlight that indentation at the crack tip position significantly reduces the J-integral compared to non-indented structures, demonstrating its potential to extend the lifespan of cracked components by delaying crack propagation. The findings underscore the practical application of ball indentation as a viable technique to retard crack growth, contributing to the longevity of cracked components and, consequently, structural integrity. This analysis revealed a crack propagation retardation gain of up to 56%. [ABSTRACT FROM AUTHOR]

A variety of hollow microneedle (HMN) designs has emerged for minimally invasive therapies and monitoring systems. In this study, a design change limiting the indentation depth of the (3D) printed custom microneedle assembly (circular array of five conical frusta with and without a stopper, aspect ratio = 1.875) fabricated using stereolithography has been experimentally validated and modeled in silico. The micro-indentation profiles generated in confined compression on 1 mm ± 0.073 mm alginate films enabled the generation of a Prony series, where displacement ranged from 100 to 250 µm. These constants were used as intrinsic properties simulating experimental ramp/release profiles. Puncture occurred on two distinct hydrogel formulations at the design depth of 150 µm and indentation rate of 0.1 mm/s characterized by a peak force of 3.5 N (H = 31 kPa) and 8.3 N (H = 36.5 kPa), respectively. Experimental and theoretical alignments for peak force trends were obtained when the printing resolution was simulated. Higher puncture force and uniformity inferred by the stopper was confirmed via microscopy and profilometry. Meanwhile, poroviscoelasticity characterization is required to distinguish mass loss vs. redistribution post-indentation through pycnometry. Results from this paper highlight the feasibility of insertion-depth control within the epidermis thickness for the first time in solid HMN literature. [ABSTRACT FROM AUTHOR]

The geodynamic evolution of the East Junggar is examined by means of satellite imaging and field‐based structural studies, U‐Pb zircon geochronology and analysis of potential field geophysical data in the Yemaquan arc and the Dulate back‐arc systems. The northern Yemaquan arc shows a pervasive WNW–ESE steep S1 foliation that is related to the exhumation of Armantai ophiolitic mélange in an F1 antiformal structure. The bedding of the Dulate sequences is folded by N–S‐trending F1 upright folds that are preserved in low strain domains. The timing of D1 is estimated between 310 and 280 Ma. During D2, previously folded Dulate sequences were orthogonally refolded by E–W‐trending F2 upright folds, resulting in Type‐1 basin and dome interference pattern and pervasive E–W trending S2 cleavage zones. The age of D2 is constrained to be 270–250 Ma based on the dating of syn‐tectonic pegmatites and deposition of syn‐orogenic sedimentary rocks. The boundary between the Yemaquan arc and Dulate back‐arc basin experienced reactivation through D2 dextral transpressive shear zones. The D1 fabrics are the consequence of the closure of the Dulate back‐arc basin due to the advancing mode of Kalamaili subduction. Almost orthogonal Permian D2 fabrics were generated by the N–S shortening of the East Junggar and the northward movement of the Junggar Block indenter. This D2 deformation was associated with the anticlockwise rotation of the southern limb of the Mongolian Orocline, the scissor‐like closure of the northerly Mongol‐Okhotsk Ocean and the collision of the Mongolian and the Tarim–North China craton collages. Key Points: The Yemaquan arc and Dulate back‐arc are affected by 310–280 Ma D1 and 270–250 Ma D2 eventsD1 results from advancing mode of the Kalamaili subduction zone, and the closure of the Dulate back‐arc basinD2 results from the collisional reworking of the East Junggar system and indentation of Junggar promontory [ABSTRACT FROM AUTHOR]

• Size-dependent near-surface response of FG elastic layer is investigated. • Size effects induced by material microstructures are modeled by couple stress elasticity theory. • Solution of surface loaded layer is derived in closed-form via Fourier transform method. • Efficient numerical scheme is implemented for layer under frictionless contacts. • Effects of length scale and model's parameters on contact response are highlighted. This paper focuses on a theoretical examination of the mechanical behavior of elastic layers made of functionally graded (FG) materials. It particularly highlights the impact of material microstructures by utilizing the couple stress theory to introduce FG characteristics of the coating material across the thickness direction, along with size effects. The study distinctively addresses both surface loading and contact problems, employing various indenter shapes and eccentric indentation forces. The Fourier transform is utilized to solve for displacements and stress fields resulting from surface tractions. The method for approximating the pressure distribution under the indenter is based on a collocation method with a simple discretization of the contact pressure. Brent's method is applied to determine the unknown contact region when using indenters with non-sharp edges. The results demonstrate that the shear modulus ratio and the intrinsic material length scale significantly influence the pressure intensity, highlighting a substantial dependence on the mechanical properties of materials under indentation force. The research also shows that the effect of the length scale and shear modulus ratio affects the limit eccentricity and tilt angle. The results highlight the necessity of considering both the size effect and material gradation when analyzing FG materials under mechanical stress. [ABSTRACT FROM AUTHOR]

This work continues the study of the process of friction between a steel spherical indenter and a soft elastic elastomer previously published in our paper. It is done in the context of our previous experimental results obtained on systems with strongly pronounced adhesive interaction between the surfaces of contacting bodies during the process of friction between a steel spherical indenter and a soft elastic elastomer. In the present paper, we concentrate on the theoretical study of the processes developing in a vertical cross-section of the system. For continuity, here the case of indenter motion at a low speed at different indentation depths is considered as before. The analysis of the evolution of normal and tangential contact forces, mean normal pressure, tangential stresses, as well as the size of the contact area is performed. Despite its relative simplicity, a numerical two-dimensional (2D = 1 + 1) model, which is used here, satisfactorily reproduces experimentally observed effects. Furthermore, it allows direct visualization of the motion in the vertical cross-section of the system, which is currently invisible experimentally. Partially, it recalls two-dimensional (2D = 1 + 1) models recently proposed to describe the "turbulent" shear flow of solids under torsion and in cellular materials. The observations extracted from the model help us to understand better the adhesive processes that underlie the experimental results. [ABSTRACT FROM AUTHOR]

Fundamental mechanical and creep behavior of minerals at elevated temperatures is relevant to many subsurface exploration and resource recovery processes, yet remains largely elusive. This study uses instrumented indentation to measure microscale deformation and nanoscale creep of biotite, albite, and quartz, which are the major mineral phases of granitic rocks, at temperatures up to 400 °C. The results show that the elastic modulus of biotite is not only the lowest at room temperature but also decays the most at elevated temperature (i.e., by 25% reduction at 400 °C) compared to that of albite and quartz. The creep deformation within 20 s doubles when the temperature increases from 20 °C to 400 °C for albite, quartz, and biotite, and biotite showed at least three times the overall creep deformation compared to quartz and albite under the same temperature. The indentation creep deformation can be well characterized using a logarithmic time model, showing both transient and constant-rate creep deformation. The secondary creep rate for biotite is about three times that of albite and quartz at the same temperature, and as the temperature increases from 20 °C to 400 °C, the rate of secondary creep becomes approximately 10 times faster for the three tested minerals. Both transient creep deformation and the rate of secondary creep can be empirically correlated to the elastic moduli, which allows quick estimates of the temperature-dependent creep behavior of granitic minerals using their elastic properties, especially when those creep constants are not readily available at elevated temperatures. These results enhance the understanding of temperature-dependent creep deformation at small scales and provide insight into mineral-level damage in granitic rocks due to temperature and long-term deformation.

In the field of composite materials, extensive research has been undertaken on aluminum-graphite composites. However, a research gap has been identified regarding the specific influence of nano-sized graphite particles on their fracture toughness. Previous studies have predominantly focused on larger graphite particles or different reinforcement materials, resulting in relatively unexplored effects of nano-graphite particles. This research is deemed critical as it has the potential to generate lightweight, high-strength materials, aligning with the demands of aerospace, automotive, and structural engineering. The primary objective of this study is to investigate how the inclusion of nano-sized graphite particles affects the fracture toughness of aluminum-graphite composites. To achieve this objective, systematic dispersion and incorporation of nano-sized graphite particles into an aluminum matrix will be carried out. Mechanical testing, including fracture toughness assessments, will be conducted to evaluate the performance of the composite materials. Factors such as particle size, distribution, volume fraction, and interfacial bonding will also be characterized within the study. It is anticipated that the presence of nano-sized graphite particles will lead to a significant enhancement of the fracture toughness of the aluminum-graphite nanocomposites. This enhancement is expected to be attributed to crack deflection, tortuosity, altered stress distribution, and increased plastic deformation around cracks.

Characterizing the dynamic mechanical properties of spinal cord tissue is deemed important for developing a comprehensive knowledge of the mechanisms underlying spinal cord injury. However, complex viscoelastic properties are vastly underexplored due to the spinal cord shows heterogeneous properties. To investigate regional differences in the biomechanical properties of spinal cord, we provide a mechanical characterization method (i.e., dynamic mechanical analysis) that facilitates robust measurement of spinal cord ex vivo, at small deformations, in the dynamic regimes. Load-unload cycles were applied to the tissue surface at sinusoidal frequencies of 0.05, 0.10, 0.50 and 1.00 Hz ex vivo within 2 h post mortem. We report the main response features (e.g., nonlinearities, rate dependencies, hysteresis and conditioning) of spinal cord tissue dependent on anatomical origin, and quantify the viscoelastic properties through the measurement of peak force, moduli, and hysteresis and energy loss. For all three anatomical areas (cervical, thoracic, and lumbar spinal cord tissues), the compound, storage, and loss moduli responded similarly to increasing strain rates. Notably, the complex modulus values of ex vivo spinal cord tissue rose nonlinearly with rising test frequency. Additionally, at every strain rate, it was shown that the tissue in the thoracic spinal cord was significantly more rigid than the tissue in the cervical or lumbar spinal cord, with compound modulus values roughly 1.5-times that of the lumbar region. At strain rates between 0.05 and 0.50 Hz, tan δ values for thoracic (that is, 0.26, 0.25, 0.06, respectively) and lumbar (that is, 0.27, 0.25, 0.07, respectively) spinal cord regions were similar, respectively, which were higher than cervical (that is, 0.21, 0.21, 0.04, respectively) region. The conditioning effects tend to be greater at relative higher deformation rates. Interestingly, no marked difference of conditioning ratios is observed among all three anatomical regions, regardless of loading rate. These findings lay a foundation for further comparison between healthy and diseased spinal cord to the future development of spinal cord scaffold and helps to advance our knowledge of neuroscience.

Explosion protection is of particular importance for safety as explosions also endanger the health of workers due to the uncontrolled effects of flames and pressure, the presence of harmful reaction products and the consumption of oxygen in the ambient air breathed by workers. CuAlBe alloy is proposed as a solution for mechanical actuators such as gears that work in environments with possible explosive atmosphere. Made of CuBe master alloy and pure aluminum in a induction furnace the material present large grains in melted state. After the hot rolling (heated 600s at 900°C) of the ingots small variation of chemical composition was observed based on the oxidation of the material, appearance of small cracks on the edges and a preferential orientation of the grains along the lamination direction. Scanning electron microscopy (SEM) was used to characterize the microstructural states of CuAlBe as laminated and heat treated states.

A variety of hollow microneedle (HMN) designs has emerged for minimally invasive therapies and monitoring systems. In this study, a design change limiting the indentation depth of the (3D) printed custom microneedle assembly (circular array of five conical frusta with and without a stopper, aspect ratio = 1.875) fabricated using stereolithography has been experimentally validated and modeled in silico. The micro-indentation profiles generated in confined compression on 1 mm ± 0.073 mm alginate films enabled the generation of a Prony series, where displacement ranged from 100 to 250 µm. These constants were used as intrinsic properties simulating experimental ramp/release profiles. Puncture occurred on two distinct hydrogel formulations at the design depth of 150 µm and indentation rate of 0.1 mm/s characterized by a peak force of 3.5 N (H = 31 kPa) and 8.3 N (H = 36.5 kPa), respectively. Experimental and theoretical alignments for peak force trends were obtained when the printing resolution was simulated. Higher puncture force and uniformity inferred by the stopper was confirmed via microscopy and profilometry. Meanwhile, poroviscoelasticity characterization is required to distinguish mass loss vs. redistribution post-indentation through pycnometry. Results from this paper highlight the feasibility of insertion-depth control within the epidermis thickness for the first time in solid HMN literature.

Indentation tests create complex stress–strain states in the region beneath the indentation tip. However, it is difficult to observe the indentation responses of bulk materials. Therefore, this study presents a wedge-indentation test technology that can investigate the subsurface deformation behavior during loading and unloading inside a scanning electron microscope. In situ observations based on multiple techniques, including a secondary electron detector, electron backscatter diffraction, and digital image correlation, are realized and used to investigate the texture evolution and stress–strain behavior of monocrystalline copper in the microregion beneath the indentation tip. Indentation induces kinked slip bands along the [01‾1‾] and [011‾] directions. The maximum shear strain of 0.324 occurs at the sides of the area in direct contact with the indentation tip. The lattice rotations in three dimensions are calculated and obtained quantitatively, and the geometrically necessary dislocation density beside the contact region reaches 0.70 × 1014/m2. The proposed method has considerable potential for explaining the deformation mechanisms of materials at microscale.

Introduction: During non-surgical endodontic retreatment, gutta-percha (GP) solvents are indispensable in difficult cases when used with mechanical removal, however studies comparing their efficacy against different types of GP are limited. The purpose of this study was to investigate the softening effect of three solvents on the conventional (CGP), cross-linked carrier-based (CLGP), and thermoplasticized (TGP) and compare the effect of time on the softening effect of the solvents. Methods: Tested GP were embedded in cuboidal blocks of stone with their upper surfaces exposed (1 mm diameter). Three commercial GP solvents based on D-Limonene (DL), Eucalyptol oil (EO), and orange oil (OO) were added to the exposed GP before an indenter (weight = 1Kg) was applied. Using a digital camera, the indentation depth was measured (mm) directly after applying the solvent and indenter (T = 0), and after 1, 2, and 3 min of application (T = 1,2,3). The means of indentation depth were calculated and compared using a two-way analysis of variance and Tukey’s post-hoc test to assess the effect of the types of solvent, GP for each application duration, and Friedman’s test to evaluate the effect of application duration on the softening effect of solvents. Results: The type of GP (F = 261.43, p

The advent of biomedical applications of soft bioinspired materials has entailed an increasing demand for streamlined and expedient characterization methods meant for both research and quality control objectives. Here, a novel measurement system for the characterization of biological hydrogels with volumes as low as 75 µL was developed. The system is based on an indentation platform equipped with micrometer drive actuators that allow the determination of both the fracture points and Young's moduli of relatively stiff polymers, including agarose, as well as the measurements of viscosity for exceptionally soft and viscous hydrogels, such as DNA hydrogels. The sensitivity of the method allows differentiation between DNA hydrogels produced by rolling circle amplification based on different template sequences and synthesis protocols. In addition, the polymerization kinetics of the hydrogels can be determined by time‐resolved measurements, and the apparent viscosities of even more complex DNA‐based nanocomposites can be measured. The platform presented here thus offers the possibility to characterize a broad variety of soft biomaterials in a targeted, fast, and cost‐effective manner, holding promises for applications in fundamental materials science and ensuring reproducibility in the handling of complex materials. [ABSTRACT FROM AUTHOR]

This study explains the development of a manufacturing process that is machinable for a ceramic product. The initial process involves manufacturing a ceramic slurry, which is a mixture of high-weight percentage ceramic powders, and a polymeric binder. The ceramic slurry is then pressed to shape a solid body knwon as the green part, which can be structured using conventional machining tools. The structured green part undergoes a debinding process, the resulting body is referred to as the brown part. Finally, sintering is performed to merge the peripheral ceramic powders, and the white part is obtained. The white part exhibited approximately 18 % isotropic shrinkage in dimension and 9.4 % weight reduction compared with the initial green part. The durability of each part is determined via impact-resistant and microindentation tests. The fracture-resistant energy of the white part is determined as 0.673 J, which is an increase of approximately 500 % compared with the values of other parts. Furthermore, the elastic modulus of the white part is determined to be 14.7 GPa, representing an increase of approximately 270 %. In conclusion, we employed an innovative manufacturing process for ceramic products to address the challenges in conventional methods. [ABSTRACT FROM AUTHOR]

The future fusion reactor devices built by Institute of Plasma Physics, Chinese Academy of Science will be a compact burning plasma facility to fill the gap between ITER and the China Fusion Engineering Test Reactor, with the mission of studying the deuterium–tritium plasma in steady-state operation. The winding-package (WP) of its toroidal field coil is graded into high-field WP and low-field WP, and the high critical current density (J c) Nb3Sn strand will be applied to the high-field WP based on the current design. The thermo-magnetic instability is the main issue in the application of high- J c Nb3Sn strand, which may induce premature quenching in the low field regions. This issue can be improved by reducing the effective filament diameter (d eff) to suppress flux jumps and increasing the residual resistivity ratio (RRR) to enhance the release of heat generated by flux jumps. However, in the conductor manufacturing process, local plastic deformations (indentation) of strands can impact the sub-element layout and degrade the RRR of the strand, which would increase again the risk on instability. In this study, magnetization measurements and V – I tests were performed on samples with different indentation depths. The hysteresis loss and d eff of the indented sample was obtained from the test results. The impact of local plastic deformation on the thermo-magnetic instability of two types of Nb3Sn strand was confirmed by cross-sectional metallographic observation and quantitative microstructure analysis. It was shown that flux jumps were suppressed at indentation depths below 0.3 mm. Further indentation increase leads to severe flux jumps. [ABSTRACT FROM AUTHOR]

This study aims to experimentally examine the indentation behaviour of marine sandwich composites with pin-reinforced polyvinyl chloride foam core and E-glass face sheets. The effects of indenter diameter, resin pin diameter, and arrangement on force-displacement, maximum contact force, and absorbed energy values of sandwich panels were evaluated by the indentation tests. Throughout the experiments, the contact forces increased as the pin diameter increased from Ø2 mm to Ø4 mm. The contact forces decreased as the distance between pin diameters increased from 12 mm to 16 mm and 18 mm. Additionally, the values of absorbed energy increased as the diameters of the resin pin and indenter increased. Placing pins at a distance of 12 mm allows the material to absorb more energy for 012.7 mm and 020 mm indenter tips. The 8 mm diameter and 12 mm spacing holes provide significant initial resistance to penetration, despite the increase in weight in critical areas, against object contact from Ø12.7 to Ø20 mm. A visual inspection took place on the post-indentation cross-sections of the sandwich specimens to detect any damage modes. Damage modes varied depending on the size of the indenter and the hole pattern in the foam core. [ABSTRACT FROM AUTHOR]

Objectives: To provide a comprehensive summary of the different modalities available to measure soft tissue fibrosis after radiotherapy in head and neck cancer patients. Data Sources: PubMed, Scopus, and Web of Sciences. Review Methods: A search was conducted using a list of medical subject headings and terms related to head and neck oncology, radiation fibrosis, and quantitative measurements, including bioimpedance, MRI, and ultrasound. Original research related to quantitative measurement of neck fibrosis post‐radiotherapy was included without time constraints, while reviews, case reports, non‐English texts, and inaccessible studies were excluded. Discrepancies during the review were resolved by discussing with the senior author until consensus was reached. Results: A total of 284 articles were identified and underwent title and abstract screening. Seventeen articles had met our criteria for full‐text review based on relevance, of which nine had met our inclusion criteria. Young's modulus (YM) and viscoelasticity measures have demonstrated efficacy in quantifying neck fibrosis, with fibrotic tissues displaying significantly higher YM values and altered viscoelastic properties such as increased stiffness rate‐sensitivity and prolonged stress‐relaxation post‐radiation. Intravoxel incoherent motion offers detailed insights into tissue changes by assessing the diffusion of water molecules and blood perfusion, thereby differentiating fibrosed from healthy tissues. Shear wave elastography has proven to be an effective technique for quantifying radiation‐induced fibrosis in the head and neck region by measuring shear wave velocity. Conclusion: There are various modalities to measure radiation‐induced fibrosis, each with its unique strengths and limitations. Providers should be aware of these implications and decide on methodologies based on their specific clinical workflow. Level of Evidence: Step 5. [ABSTRACT FROM AUTHOR]

The incorporation of sustainability into the design of transport vehicles has become increasingly important in recent years. A low carbon footprint makes wood-based structures attractive to replace other lightweight materials such as aluminum or fiber-reinforced plastics. This paper investigates and compares the static and dynamic impact behavior of thin Beech wood veneer laminates in standardized mechanical tests. The results obtained from Quasi-Static Indentation (QSI) and dynamic Low-Velocity Impact (LVI) tests reveal similarities and differences with regard to load vs. displacement behavior, damage mechanisms, permanent deformation, and energy absorption. While yield strength and damage modes are comparable in both test cases, it is found that the bending stiffness is strain-rate sensitive. Plastic deformation in compression is identified as the governing mechanism for energy absorption. These results can guide the design of sustainable wood-based structures for future transport applications where a thorough understanding of impact and crashworthiness is important. [ABSTRACT FROM AUTHOR]

The tangential adhesive contact (friction) between a rigid steel indenter and a soft elastomer at shallow indentation depths, where the contact exists mainly due to adhesion, is investigated experimentally. The dependencies of friction force, contact area, average tangential stresses, and the coordinates of the front and back edges of the contact boundary on the indenter displacement are studied. It is found that first a stick–slip mode of friction is established, which is then replaced by another, more complex mode where the phase of a global slip of the elastomer on the indenter surface is absent. In both regimes, the evolutions of friction force and contact area are analyzed in detail. [ABSTRACT FROM AUTHOR]

The ever-increasing usage of ceramic materials in restorative dentistry necessitates a simple and effective method to evaluate flexural strength σF and fracture toughness K C. We propose a novel method to determine these quantities using a bilayer specimen composed of a brittle plate adhesively bonded onto a transparent polycarbonate substrate. When this bilayer structure is placed under spherical indentation, tunneling radial cracks initiate and propagate in the lower surface of the brittle layer. The failure analysis is based on previous theoretical relationships, which correlate σF with the indentation force P and layer thickness d, and K C with P and mean length of radial cracks. This work examines the accuracy and limitations of this approach using a wide range of contemporary dental ceramic materials. The effect of layer thickness, indenter radius, load level, and length and number of radial cracks are carefully examined. The accuracy of the predicted σF and K C is similar to those obtained with other concurrent test methods, such as biaxial flexure and 3-point bending (σF), and bending specimens with crack-initiation flaws (K C). The benefits of the present approach include treatment for small and thin plates, elimination of the need to introduce a precrack, and avoidance of dealing with local material nonlinearity effects for the K C measurements. Finally, the bilayer configuration resembles occlusal loading of a ceramic restoration (brittle layer) bonded to a posterior tooth (compliant substrate). [ABSTRACT FROM AUTHOR]

Cell models play a crucial role in analyzing the mechanical response of cells and quantifying cellular damage incurred during micromanipulation. While traditional models can capture the overall mechanical behavior of cells, they often lack the ability to discern among distinct cellular components. Consequently, by employing dissipative particle dynamics, this study constructed a triangular network-like representation of the cell membrane along with cross-linked cytoskeletal chains. The mechanical properties of both the membrane and cytoskeleton were then analyzed through a series of simulated mechanical tests, validated against real-world experiments. The investigation utilized particle-tracking rheology to monitor changes in the mean square displacements of membrane particles over time, facilitating the analysis of the membrane's storage and loss moduli. Additionally, the cytoskeletal network's storage and loss moduli were examined via a double-plate oscillatory shear experiment. The simulation results revealed that both the membrane and cytoskeleton exhibit viscoelastic behavior, as evidenced by the power-law dependency of their storage and loss moduli on frequency. Furthermore, indentation and microinjection simulations were conducted to examine the overall mechanical properties of cells. In the indentation experiments, an increase in the shear modulus of the membrane's WLCs correlated with a higher Young's modulus for the entire cell. Regarding the microinjection experiment, augmenting the microinjection speed resulted in reduced deformation of the cell at the point of membrane rupture and a lower percentage of high strain. [ABSTRACT FROM AUTHOR]