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Force plate testing is commonly used to assess athlete performance. However, there is limited research on the effect the surface underneath the force plate has on derived variables. The aim of this study was to investigate whether different surfaces underneath a force plate would elicit differences in derived force plate variables using a mechanical testing device. A device was used rather than human participants to ensure controlled and repeatable impacts. The device was used to assess force reduction, peak force, rate of force development (RFD) and contact time across seven common testing surfaces: vinyl, rubber, Olympic lifting platform, ground (CarpetG) and first floor (CarpetF) carpet, Mondo track and a sprung gymnasium floor (Sprung). Significant differences in force reduction, peak force, RFD, and contact time were found between flooring conditions (p < 0.05), with large to extremely large effect sizes. Sprung flooring exhibited the highest force reduction and lowest peak forces, while CarpetF demonstrated the lowest RFD and longest contact time. These findings highlight the flooring surface underneath the force plate during testing significantly influenced derived variables. Practitioners should exert caution and consideration to force plate testing location and advocate standardisation in flooring surface in order to ensure consistent and accurate results.

Quantifying the material properties of tissues and hydrogels aids in the development of biomedical applications through better understanding of the mechanics and mechanobiological principles at play. This study introduces a mechanical testing platform designed to address challenges in measuring mm-scale tissue and hydrogel material properties. Using a floating buoy design, the platform enables horizontal submerged tensile testing with non-submersible load cells. Buoy drag testing without a sample attached resulted in signal noise (mean ± standard deviation) of −1.6E-4 ± 2.8E-2 mN for stationary recording and 1.3E-2 ± 6.7E-2 mN for maximum buoy displacement speed (1000 µm/s), suggesting the magnitude of drag forces from buoy movement are negligible in comparison to the minimum resolution of force measurement. Validation testing with latex orthodontic bands showed a ∼ 28 × reduction in signal noise with the buoy approach compared to a previously used approach, and similar force displacement recordings using the buoy approach with 2 separate hardware systems. Simultaneous imaging enabled geometrical and microstructural analysis of the sample. Murine bladder tissue was mechanically tested using two different hardware systems and testing protocols. The platform was able to accurately capture the nonlinear stress-stretch response, alongside expected strain-softening and preconditioning behavior. Stress-relaxation testing yielded results consistent with expected microstructural and viscoelastic responses of mouse bladder tissue. The versatility of the platform underscores the potential for it to integrate with various force measurement and actuator-based systems. In conclusion, this platform offers a new avenue for accurate measurement of tissue and hydrogel mechanics, facilitating mm-scale soft material research.

With the rapid development of computer technology, numerical simulations of rock dynamics have been widely carried out. The accuracy of numerical simulations depends on the parameters of the constitutive model. In this paper, the parameters of a Johnson–Holmquist-II (JH-2) constitutive model for granite were determined. First, mechanical and penetration tests were carried out on granite specimens. The mechanical tests included a quasi-static compression test and Brazilian disc splitting test to obtain the basic mechanical parameters and failure modes of granite under impact loading. Then, using the experimental results combined with the existing literature data, the parameters of the JH-2 constitutive model were determined through theoretical derivation. Finally, by comparing the numerical simulation results with the test results, the validity of the parameters was verified. These parameters can better simulate the mechanical response and failure modes of granite under different loads. The material model parameters can provide references for subsequent experiments and related numerical simulations.HighlightsThe parameters of a Johnson–Holmquist-II (JH-2) constitutive model for granite were obtained.Various mechanical tests and penetration tests were performed on granite.The model parameters have a wide range of applications.

Central Alborz Zone (CAZ) is one of the most important zones in Iran, which comprises a wide variety of carbonate rocks such as limestone, dolomite, and their compounds. Therefore, determining engineering geological characteristics of carbonate rocks is essential for proper use in civil, mining, and geotechnical engineering. The purpose of this work was to investigate the relationships between the uniaxial compressive strength (UCS) and the point load index (PLI), Schmidt hammer rebound (SHR) value, and Brazilian tensile strength (BTS). In addition, the UCS value was predicted based on the young modulus (UCS-E) and sample size factors in terms of length, length to diameter (L/D), and volume. In this study, samples were collected from the type section of 12 formations of the CAZ, and all of them were classified based on the petrographic study as carbonate rocks (Limestone, dolostone, etc.). The results showed significant positive linear equations within the 95% prediction bands for correlating UCS to PLI, BTS, SHR, and E. A conversion factor of carbonate rocks in the linear regression without intercept for UCS–PLI, UCS–BTS, UCS–SHR, and UCS-E was observed as 14.32, 7.26, 1.71, and 3.52, respectively. This study concentrated on the carbonate rocks; therefore, the results compared to previous studies were conducted on carbonate rocks. Also, the relation between the modulus ratio (MR), UCS, and maximum axial strain (εa max) studied for all rock samples and results showed that the UCS has a partial effect on MR and εa max has a strong correlation with MR. Concerning the sample size, results showed that with an increase in the length, L/D, and volume of the specimens, the UCS values are decreased. This reduction is because of an increase of internal defects (increase in length and diameter), end effects, and lateral deformation. The decrease of the UCS value is more sharply in the L/D ratios between 2 and 2.5, and for more than 2.5, the reduction rate is much lower.

Recently, three-dimensional (3D) warp interlock fabric has been involved in composite reinforcement and soft ballistic material due to its great moldability, improved impact energy-absorbing capacity, and good intra-ply resistance to delamination behaviors. However, understanding the effects of different parameters of the fabric on its mechanical behavior is necessary before the final application. The fabric architecture and its internal yarn composition are among the common influencing parameters. The current research aims to explore the effects of the warp yarn interchange ratio in the 3D warp interlock para-aramid architecture on its mechanical behavior. Thus, four 3D warp interlock variants with different warp (binding and stuffer) yarn ratios but similar architecture and structural characteristics were engineered and manufactured. Tensile and flexural rigidity mechanical tests were carried out at macro- and meso-scale according to standard EN ISO 13 934-1 and nonwoven bending length (WSP 90.5(05)), respectively. Based on the results, the warp yarn interchange ratio in the structure revealed strong influences on the tensile properties of the fabric at both the yarn and final fabric stages. Moreover, the bending stiffness of the different structures showed significant variation in both the warp and weft directions. Thus, the interchange rations of stuffer and binding warp yarn inside the 3D warp interlock fabric were found to be very key in optimizing the mechanical performance of the fabric for final applications.

The use of biodegradable polymers as matrices in composites gives a wide range of applications, especially in niche areas. The assessment of the effect of the filler content on the change of mechanical properties makes it possible to optimize the composition for specific needs. Biochar was used as a filler in the studied composites with two different biodegradable blends as a matrix. Poly(1,4-butylene adipate-co-1,4-butylene terephthalate)/polylactide/biochar (PBAT/PLA/BC) and polylactide/poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate]/biochar (PLA/P(3HB-co-4HB)/BC) composites with 0, 10, 15, 20 and 30 wt% of biochar underwent mechanical tests. The test results revealed a change in the properties of the composites related to the filler content. The results of the tensile test showed that increasing the biochar content increased the tensile modulus values by up to 100% for composites with 30 wt% of biochar, compared to unfilled matrices, and decreased the elongation associated with the breaking of PBAT/PLA and PLA/P(3HB-co-4HB) matrix composites. The elongation values at break of PBAT/PLA and PLA/(3HB-co-4HB) composites with 30 wt% biochar were reduced by 50% and 65%, respectively, compared to the unfilled matrices. PLA/P(3HB-co-4HB) matrix composites, in contrast to PBAT/PLA/BC, showed a decrease in tensile strength with the increases in filler content from 35.6 MPa for unfilled matrix to 27.1 MPa for PLA/P(3HB-co-4HB)/BC30 composites. An increase in filler content increased the brittleness of the composites regardless of the matrix used, as determined under the Charpy impact-test. This phenomenon was observed for all tested PLA/P(3HB-co-4HB) composites, for which the impact strength decreased from 4.47 kJ/m2 for the matrix to 1.61 kJ/m2 for the composite containing 30 wt% biochar. PBAT/PLA-based composites with 10 wt% of biochar showed slightly lower impact strength compared to the unfilled matrix, but composites with 30 wt% biochar showed 30% lower impact strength than PBAT/PLA. The complex viscosity value increased with increased filler content. For all composites tested on both polyester matrices, the viscosity decreased with increasing angular frequency.

Coronary artery disease (CAD), one of the leading causes of death globally, occurs due to the growth of atherosclerotic plaques in the coronary arteries, causing lesions which restrict the flow of blood to the myocardium. Percutaneous transluminal coronary angioplasty (PTCA), including balloon angioplasty and coronary stent deployment is a standard clinical invasive treatment for CAD. Coronary stents are delivered using a balloon catheter inserted across the lesion. The balloon is inflated to a nominal pressure, opening the occluded artery, deploying the stent and improving the flow of blood to the myocardium. All stent manufacturers have to perform standard in vitro mechanical testing under different physiological conditions. In this study, partially and fully bioresorbable vascular scaffolds (BVS) from Boston Scientific Limited have been examined in vitro and in silico for three different test methods: inflation, radial compression and crush resistance. We formulated a material model for poly-L-lactic acid (PLLA) and implemented it into our in-house software tool. A comparison of the different experimental results is presented in the form of graphs showing displacement-force curves, diameter – load curves or diameter - pressure curves. There is a strong correlation between simulation and real experiments with a coefficient of determination (R2) > 0.99 and a correlation coefficient (R) > 0.99. This preliminary study has shown that in-silico tests can mimic the applicable ISO standards for mechanical in vitro stent testing, providing the opportunity to use data generated using in-silico testing to partially or fully replacing the mechanical testing required for regulatory submission.

The structural components made of polymer composites in aviation, automobile, and marine applications are subjected to various environmental conditions throughout their design service life. Furthermore, the examination of the effect of various ageing environments on moisture absorption and mechanical behaviour is essential to protect the structures from premature and catastrophic failures. This study evaluates the influence of three different ageing conditions, namely, ambient (25°C), sub-zero (−10°C), and humid (40°C and 60% relative humidity) on the mechanical properties of hybrid interply basalt-aramid/epoxy composites. The compression molding process was adopted to fabricate the specimens and the specimens were aged in a distilled water environment for a period of 180 days. The aged specimens were subjected to static and dynamic mechanical tests viz. tensile, flexural (3-point bending), short-beam shear (SBS), and Charpy impact tests to study the behaviour, and then results were compared with the unaged specimens. Fourier Transform Infrared Spectroscopy (FTIR) was also performed to analyze the chemical changes within the composites due to the ageing process. It was witnessed that moisture absorption rate increases with - increase in ageing period and attains a state of saturation between 1.8% and 5.44% depending on the ageing conditions. Investigations revealed that moisture absorption has an unfavourable effect on the mechanical performance of the composites. The retention of mechanical strengths of aged composites is in the order of Unaged > Sub-zero > Humid > Ambient. Fractured tensile specimens were analyzed for microscopic observation using Scanning Electron Microscope (SEM) to study the damage morphology. Matrix decomposition, matrix cracks, and interfacial debonding were the major failure modes observed in aged composites.

Bone fractures pose a serious challenge for the healthcare system worldwide. A total of 17.5% of these fractures occur in the distal radius. Traditional cast materials commonly used for treatment have certain disadvantages, including a lack of mechanical and water resistance, poor hygiene, and odors. Three-dimensional printing is a dynamically developing technology which can potentially replace the traditional casts. The aim of the study was to examine and compare the traditional materials (plaster cast and fiberglass cast) with Polylactic Acid (PLA) and PLA–CaCO3 composite materials printed using Fused Filament Fabrication (FFF) technology and to produce a usable cast of each material. The materials were characterized by tensile, flexural, Charpy impact, Shore D hardness, flexural fatigue, and variable load cyclic tests, as well as an absorbed water test. In addition, cost-effectiveness was evaluated and compared. The measured values for tensile strength and flexural strength decreased with the increase in CaCO3 concentration. In the fatigue tests, the plaster cast and the fiberglass cast did not show normal fatigue curves; only the 3D-printed materials did so. Variable load cyclic tests showed that traditional casts cannot hold the same load at the same deflection after a higher load has been used. During these tests, the plaster cast had the biggest relative change (−79.7%), compared with −4.8 % for the 3D-printed materials. The results clearly showed that 3D-printed materials perform better in both static and dynamic mechanical tests; therefore, 3D printing could be a good alternative to customized splints and casts in the near future.

Companies developing automated driving system (ADS) technologies have spent heavily in recent years to conduct live testing of autonomous vehicles operating in real world environments to ensure their reliable and safe operations. However, the unexpected onset and ongoing resurgent effects of the Covid-19 pandemic starting in March 2020 has serve to halt, change, or delay the achievement of these new product development test objectives. This study draws on data obtained from the California automated vehicle test program to determine the extent that testing trends, test resumptions, and test environments have been affected by the pandemic. The importance of government policies to support and enable autonomous vehicles development during pandemic conditions is highlighted.