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The dynamic behavior of TiNi shape memory alloy (SMA) bellows is examined in light of its potential use as elements in seismic protection devices. Dynamic property results obtained from cyclic tests under tension-compression loading of TiNi SMA single-stage bellows, with different shapes and with different heat treatments, are reported as a function of displacement amplitude and frequency. It was found that the displacement–force loops were almost symmetric with respect to the central point for almost all specimens. The normalized secant stiffness diminishes significantly with increasing bulge height as well as displacement amplitude. From hysteretic cycles, an equivalent damping of about 15% was recognized for longtime-aged bellows with relatively high bulge height. Frequencies, in the range of interest for seismic applications, had a small influence on damping values. Under the conditions studied in this research, the bellows had better damping performance in a martensite phase than in a rhombohedral phase. SMA bellows in martensite phase subjected to the longtime-ageing have great potential as an element in seismic devices.

Bulk nanocrystalline Ni samples were prepared by plasma evaporation method combined with hot pressure sintering. The compressive mechanical properties of the bulk samples were tested under quasi-static strain rates at room temperature and the evolution of microstructure of bulk sample before and after compression was studied. The experimental results indicated that the bulk samples show a good combination of strength and ductility and have obvious strain rate sensitivity. Both dislocation glide mediated and grain boundary mediated deformation mechanism were found to be main operating deformation mechanisms for the bulk samples based on the mechanical behaviors and grain refinement after compression.

The numerical meso-modeling method is a powerful tool for simulating concrete and studying the influence of the geometric form of meso-structure on its mechanical behavior. It is still uncertain how to most effectively characterize the geometric form of the concrete meso-structure and its effect on the observed macro behavior. In this study, the fractal dimension of cement paste was used to describe the geometric form of concrete at the meso-level. A group of meso-models of concrete with various fractal dimensions and coarse aggregate contents were simulated using the Random Fractal Modeling method, and the numerical results under compression and tension were studied and discussed. The simulation results suggested that the compressive initial modulus, the compressive strength decreased, the strain corresponding to the maximum compressive stress decreased with increasing fractal dimension. However, the fractal dimension did not influence the tensile initial modulus, the tensile strength, and the strain corresponding to the maximum tensile stress obviously. The comprehensive consideration of the fractal characterize can provide a reasonable tool for understanding and predicting the observed macroscopic behavior of concrete.

Amorphous Al–Cu–Ti metal foams were prepared by spark plasma sintering (SPS) process with the diameter of 10mm. The SPS process was conducted at the pressure of 200 and 300MPa with the temperature of 653–723K, respectively. NaCl was used as the space-holder, forming almost separated pores with the porosity of 65 vol%. The microstructure and mechanical behavior of the amorphous Al–Cu–Ti metal foams were systematically investigated. The results show that the crystallinity increased at elevated temperatures. The effect of pressure and holding time on the crystallization was almost negligible. The intermetallic compounds, i.e. Al–Ti, Al–Cu and Al–Cu–Ti were identified from X-ray diffraction (XRD) patterns. It was found that weak adhesion and brittle intermetallic compounds reduced the mechanical properties, while lower volume fraction and smaller size of NaCl powders improved the mechanical properties.

Nowadays, the demand for needle-punched nonwoven fabrics has been increasing, especially in the areas of high-performance composites as reinforcement due to their potential of imparting high $z$-directional strength, easy resin absorption, light weight, and low cost. In this study, needle-punched nonwoven viscose fabric-reinforced epoxy composites are prepared by varying the area density of fabric mat (100gsm, 200gsm, 300gsm, and 400gsm) at constant fabric loading of 30wt.%. The effects of area density on mechanical and slurry abrasion behavior of composites are studied under controlled laboratory conditions. It is observed that the mechanical properties and abrasive wear resistance under steady-state condition has been improved with the increase in area density of fabric mat. Furthermore, experimental design through Taguchi’s L${}_{16}$ orthogonal array is applied to find out the optimal parametric combination for minimum wear rate. It is also observed through the analysis that silica sand size and sliding velocity are the most influential factors for wear rate.

Titanium and its alloys used in biomaterial applications are preferrably the cause of high-corrosion resistance properties in addition to having good mechanical properties. Commercially pure Ti (CP-Ti) (Grade 2), Ti6Al4V (Grade 5) and Ti6Al4V-ELI (Grade 23) samples are used as biomaterials exposed to 750^∘C and 1060^∘C for 1h. The samples were cooled in air after heat treatment at 750^∘C, the other samples were cooled in water after heat treatment at 1060^∘C. The free-heat treatment samples are as producted. Microstructures of heat-treated samples and non-made samples by comparison were evaluated before and after corrosion process microstructures and tensile strengths. Test solution is 0.5mol H₂SO${}_4+1$mol HCl mixture. The corrosion resistance of the titanium samples was evaluated. Microstructure images were monitorized on optical and SEM microscopes.

In this paper, the effect of heat treatment was determined on the microstructure, mechanical properties and corrosion resistances of the material. As a result, heat treatment is useful on corrosion resistance of alloyed samples.

This study investigates the potential of natural fibers, commonly used as cost-effective fillers in the plastic industry, as replacements for glass fibers in composite materials. Despite their advantages, these natural fibers possess a strong polar nature, causing compatibility issues with certain thermoplastic platforms, particularly aromatic compounds. Surface-level treatments, though not cost-effective, offer a solution to this issue. This research focuses on optimizing and qualifying two treatment methods, the acetyl method and stearic treatment, applied to two types of flax fibers: long and short. Examining variables such as temperature, treatment duration, and compound recovery, this study employed diffraction and gas chromatography techniques to evaluate treated and untreated fibers. Results revealed that both treatments effectively reduced non-crystalline segments within the fibers, altering surface topography. Notably, the acetyl method increased fiber surface energy, while the stearic treatment decreased it. These findings underscore the significant impact of the acetyl method and stearic treatment on modifying fiber properties, particularly surface characteristics and energy levels. The study sheds light on the potential applications of these treatments in enhancing the compatibility of natural fibers with thermoplastic platforms, despite their inherent polarity. Incorporating visuals depicting the treatment processes would further enrich the study’s authenticity and engagement, providing a tangible representation of the methods employed.

The influence of alumina addition on mechanical behavior and fracture properties of all-ceramics zirconia dental materials was evaluated. Samples containing 0, 5, 10, 15 wt.% Al₂O₃ particles were prepared by cold isostatic pressing (200 MPa) and sintered at 1500°C for 5 h. Commercial powders were investigated by bulk density and phase formation using Archimedes principle and X-ray diffraction (XRD). Bending strength and fracture load were determined at room temperature by three-point bending test. In order to study the fracture, we took points on the crack path under microscope, plotted points on coordinates and used software "Origin" to general fitting curves. Scanning electron microscopy (SEM) and atomic force microscope (AFM) were introduced to estimate the particle size of powders and observe the fracture surfaces. No density difference was observed for a given alumina content. The majority phases of ceramics were t-zirconia and α-alumina before breaking while m-zirconia, t-zirconia and α-alumina coexisted on the cross section of cracked samples. Zirconia containing 10% alumina had the best mechanical properties, the most tortuous crack propagation and the least obvious crack distribution. This observation may provide a reference for the materials selection, shape design and production process of all-ceramic crown and bridge.

Knee joint is the hub of human lower limb movement and it is also an important weight-bearing joint, which has the characteristics of load-bearing and heavy physical activities. So the knee joint becomes the predilection site of clinical disease. Once people have the cartilage lesions, their daily life will be affected seriously. The simulation of the knee joint lesions could provide help for clinical knee-joint treatment. Based on the complete model of knee joint, this paper use the finite element method to analyze the biomechanical characteristics of the defective knee joint. The results of simulation show that the stress of cartilages when standing on single leg is approximately doubled than that of standing on two legs. When standing on single leg, the 8-mm diameter osteochondral defect in femur cartilage can generate maximal changes in von-mises stress (by 36.74%), while the von-mises stress on tibia cartilage with 8-mm defect increase by 87%. The stress distribution of cartilages is almost the same, there is no obvious stress concentration when in defect. Increasing the defective diameter, femoral cartilage, meniscus and tibial all present an increasing trend towards stress. When increasing the applied load, the stress of the femoral cartilage, the meniscus and the tibial cartilage all increased.

The instant mechanical behaviors of stenotic coronary artery and deployed stents have significant impacts on percutaneous coronary intervention prognosis. However, they could not be obtained directly from the current examination techniques, which are commonly used in clinical practice. Thus, we intend to investigate the instantaneous mechanical behaviors of deployed stent and artery through virtually stenting technology based on a real clinical case in assessment of geometric and biomechanical characteristics. Method: Finite element analysis models, including rigid guide catheter, six-folded balloon with conical tip, crimped and bended stent, stenotic coronary artery with soft plaques, were simulated through virtual mechanical expansion and recoil procedure. The morphology changes of coronary lumen, strain and stress distribution of involved components at different stages and apposition of stent struts were analyzed. Results: Lumen in the stenotic region restored patency obviously at maximum expansion and had an elastic recoil about 13.5% later. The maximum principal stress distribution of artery walls and plaque was mainly concentrated in the stenotic segment with the peak value of 1.252MPa and 2.975MPa at max expansion, 0.713MPa and 1.25MPa after recoil, respectively. The higher von Mises stress and plastic equivalent strain of stent were present at the bended strut and inter-ring connectors with the peak value of 714.2MPa and 0.2385 at max expansion, 694MPa and 0.2276 after recoil. Slight malappositions were found in the proximal segment and struts distribution in the stenotic sites showed certain asymmetry. Conclusion: The instant mechanical behaviors of artery and stent could be evaluated through virtual stenting approach in assessment of geometric and biomechanical characteristics. This may contribute to choosing the best stenting schemes and predicting the clinical outcomes for a specific patient.

Blood clots occur in the human body when they are required to prevent bleeding. In pathological states such as diabetes and sickle cell disease, blood clots can also form undesirably due to hypercoagulable plasma conditions. With the continued effort in developing fibrin therapies for potential life-saving solutions, more mechanical modeling is needed to understand the properties of fibrin structures with inclusions. In this study, a fibrin matrix embedded with magnetic micro particles (MMPs) was subjected to a magnetic field to determine the magnitude of the required force to create plastic deformation within the fibrin clot. Using finite element (FE) analysis, we estimated the magnetic force from an electromagnet at a sample space located approximately 3cm away from the coil center. This electromagnetic force coupled with gravity was applied on a fibrin mechanical system with MMPs to calculate the stresses and displacements. Using appropriate coil parameters, it was determined that application of a magnetic field of 730A/m on the fibrin surface was necessary to achieve an electromagnetic force of 36nN (to engender plastic deformation).

Modeling the mechanical behavior of bone is very complex due to substantial variability of the mechanical response of bone. The objective of this study is to investigate the link between morphology of the human parietal bone and its mechanical behavior in compression with two different strain rates. Five formalin-preserved human skulls were used, and 10 specimens were taken from the parietal bone of each subject. The internal geometry of the osseous material was studied with a micro-tomography device. For mechanical testing, quasi-static (0.02 s^–1) tests on a conventional compression machine and dynamic tests (1500 s^–1) on a split Hopkinson pressure bar (SHPB) were conducted on 9 mm diameter samples. The results were used to examine relationships between the morphological parameters to find morphological correlations. Linkages between mechanical behavior and morphology of the human parietal bone were also analyzed to develop a behavior model based on micro-structure parameters as determined by micro-scanning.

Current literature reports a wide range of stiffness values and constitutive models for lung tissue across different spatial scales. Comparing the reported lung tissue stiffness values across different spatial scales may provide insights into how well those mechanical properties and the proposed constitutive models represent lung tissue’s mechanical behavior. Thus, this study applies in silico modeling to compare and potentially bridge the differences reported in lung tissue mechanical properties at different length scales. Specifically, we predicted the mesoscale mechanical behavior of rat lung tissue based on in situ and in vitro microscale test data using finite element (FE) analysis and compared those computational predictions to the reported data using mesoscale uniaxial experiments. Our simulations showed that microscale-based stiffness values differed from the mesoscale data in the simulated strain range of 0–60%, with the atomic force microscopy (AFM)-based data overestimating the mesoscale data above 15% strain. This research demonstrates that computational modeling can be used as an informative and guiding tool to investigate and potentially bridge the differences in reported lung tissue material properties across length scales.

The mechanical properties of nanocrystalline (Nc) Ni (electrodeposited, sintered, rolled) and microcrystalline (Mc) Ni were investigated by nanoindentation technique. Force-displacement curves generated during loading and unloading of the nanoindenter tip (Berkovich diamond tip) were used to determine the hardness and elastic properties of the Nc-nickel. The influence of loading rate on the hardness of electrodeposited Nc-Ni and microcrystalline (Mc) Ni were studied in the present work. The electrodeposited Nc-nickel exhibits higher hardness and elastic modulus when compared to sintered Nc-nickel. The higher modulus of elasticity is observed for the rolled Nc-nickel due to the increased defect density and less porosity in the samples. The higher modulus of elasticity is observed for Mc-nickel when compared to that of Nc-nickel (electrodeposited) with varying load rate. The strain rate sensitivity of Nc-nickel is due to the grain boundary affected zone.

Uniaxial compressive experiments of ultrafine-grained (UFG) copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 K to 573 K under quasi-static and dynamic loading conditions. Based on the experimental results, the influence of temperature on flow stress, strain hardening rate and strain rate sensitivity (SRS) were investigated carefully. The results show that the flow stress of UFG copper displays much larger sensitivity to testing temperature than that of coarse grained copper. Meanwhile, both the strain hardening rate and its sensitivity to temperature of UFG copper are lower than those of its coarse counterpart. The SRS of UFG copper also shows apparent dependence on temperature. Although the estimated activation volume of UFG-Cu is on the order of ~10 b³, which is on the same order with that of grain boundary diffusion processes, these processes should be ruled out as dominant mechanisms for UFG-Cu at our experimental temperature and strain rate range. Instead, it is suggested that the dislocation-grain boundary interactions process might be the dominant thermally activated mechanism for UFG-Cu.

Hydrogels possess magnificent properties which may be harnessed for novel applications. However, this is not achievable if the mechanical behaviors of hydrogels are not well understood. This paper aims to provide the reader with a bird's eye view of the mechanics of hydrogels, in particular the theories associated with deformation of hydrogels, the phenomena that are commonly observed, and recent developments in applications of hydrogels. Besides theoretical analyses and experimental observations, another feature of this paper is to provide an overview of how mechanics can be applied.

The finite element analysis (FEA) of porous NiTi shape memory alloys (SMAs) remains a challenge due to irregularity and complexity of pore structure. In this paper, the real finite element model (FEM) is established based on the geometrical reconstruction. Through a SMA constitutive model, the mechanical behavior and stress-induced martensitic (SIM) phase transformation are analyzed with the real FEM. The results show that the stress–strain curve of FEA is in good agreement with the experimental curve and the calculation can reflect the mechanical behavior well in the compressive process. With the increase of load, the SIM first appears pore walls or weak parts of struts, then spreads to the center of matrix, and finally happens to most of matrix. When the slope of the stress–strain curve shows obvious changes, the SIM has happened in quite a part of matrix.

Installing flexible layer is one kind of supporting techniques to deal with the large deformation in tunnels excavated in viscoelastic rocks. The role of flexible layer is to absorb rock deformation due to rock rheology. For further understanding the effect of flexible layer on mechanical behavior of tunnels, a three-layered model is established to study the mechanical behavior of tunnel where flexible layer is installed between surrounding rock and primary support. Visco-elastic analytical solutions for displacements and interaction forces in the rock/flexible layer interface and in the flexible layer/primary support interface are provided. Numerical calculation by use of finite element software Abaqus is carried out to verify the effectiveness and reliability of theoretical analysis. It could be found that flexible layer has a good ability to absorb rock deformation. Compared with rigid support structure, pressure and displacement of primary support in tunnels employing flexible layer could achieve a good improvement. This improvement is dramatically affected by the thickness and deformability of reserved flexible layer.

Bone mechanical behavior varies according to the mechanical loading to which it is subjected, and its response effectiveness mainly depends on its quality. Thus, measuring the indicators controlling the bone quality is required to assess its strength. Indeed, the Finite Element Method (FEM) provides a non-invasive tool to interpret bone quality. Therefore, this work coupled the FEM with a micromechanical law, aiming to provide an exhaustive description of the human bone mechanical behavior. Anisotropy, viscoplasticity and damage were introduced in the material behavior law and the damage evolution was plotted based on the applied loading. Then a sensitivity study was conducted to evaluate the effects of viscoplasticity and damage parameters on bone behavior. The obtained numerical results were in a good agreement with the previously reported experimental data and allowed to distinguish key parameters from non-significant ones. This new computational model provided a better understanding of the main parameters affecting bone behavior.

Ductile point-contact structures are widely used in engineering applications, with their yield strength and mechanical behavior directly related to the application safety of relevant engineering structures. The Hertz elastic contact theory can effectively express the mechanical behavior of a point-contact structure at the initial stage of load bearing. However, it cannot be applied when the structure has a characteristic yield. In this study, by analyzing the stress distribution characteristics of a point-contact structure prior to characteristic yield, the maximum contact stress on the contact surface was numerically calculated and summarized. Based on the assumption of simplified bilinear constitutive relation of materials, an elastic–plastic analytical model was derived to characterise the mechanical behavior of ductile point-contact structures before and after yield, with its validity verified using the finite element numerical calculations and experimental method.