High Elastic Deformation Research Articles

Normal contact stiffness modeling and contact characteristic research of scraped surfaces considering the truncated cone high points

In order to study the normal contact characteristics of scraped surface, a normal contact stiffness model of scraped surface was proposed considering truncated cone high points, where scraped surface was equivalent as tandemly connected truncated cone high points with asperity. The high points parameters such as the percentage of high points (POP) and the height of high points (HOP) were obtained by lapping-image processing and high points height histogram, respectively. Through high points elastic deformation formula and fractal asperity elastic-plastic deformation formula, the normal contact stiffness model of scraped surface is established. Results show that increasing fractal dimension and reducing contact gap by lapping, while decreasing HOP and increasing POP by scraping can improve the contact characteristics of scraped surface.

Highly Stretchable Piezoelectric Elastomer for Accelerated Repairing of Skeletal Muscles Loss

AbstractSkeletal muscle loss is a common clinical disease, whose long treatment period and expensive treatment costs bring a heavy burden to patients. Currently, the use of piezoelectric materials to generate in situ and efficient electrical stimulation has been proven to significantly promote wound healing and other defects. However, skeletal muscle requires repaired materials with high elastic deformation to accompany its reciprocating movement during the healing process. Therefore, developing biocompatible materials that combine high piezoelectricity and stretchability is a great challenge. In the present work, a piezoelectric elastomer PPBE is prepared by copolymerization of bio‐based diacid and diol. PPBE has matching elastic modulus with the skeletal muscle to accompanied proceed stretching and recovery movements. Piezoelectrical charge from PPBE scaffold under ultrasound and mechanical stimuli could promote myogenic differentiation via Ca2+ signaling pathway and modulate cell functions, resulting in improved muscle morphology and functional performance of skeletal muscle. Thus, development of the degradable PPBE scaffold would provide new therapy strategy for volumetric muscle loss (VML) and present great potential in repairing of other tissues.

Orientation dependent magnetocapacitance tuning in epitaxial (La,Sr)MnO3/(K,Na)NbO3-based heterostructures

We fabricated multiferroic heterostructures composed of La0.67Sr0.33MnO3 (LSMO) and (K0.48Na0.48Li0.04) (Nb0.81Ta0.15Sb0.04)O3 (KNN-LTS) on (001)-, (110)-, and (111)-oriented SrTiO3 substrates using pulsed laser deposition technique. X-ray diffraction confirmed the coherent growth of LSMO layers, while KNN-LTS layers exhibited partial relaxation in the heterostructures, with relaxation increasing from (001) to (111) orientations. Notably, the (111)-oriented LSMO, which displayed the highest out-of-plane lattice relaxation, exhibited superior magnetic properties. On the other hand, (001)-oriented sample showcased the maximum ferroelectric and piezoelectric properties due to its high elastic deformation, whereas (111)-oriented sample, characterized by higher intrinsic lattice deformation, demonstrated better dielectric properties. Our elemental analysis confirmed interface charge transfer, indicating the presence of magnetoelectric coupling within the heterostructures. Then, the magnetocapacitance effect was attributed to a combination of interface magnetoelectric coupling and magnetoresistance in LSMO. The (111)-oriented sample displayed a remarkable MC value of approximately 62% near the transition temperature (around 352 K) of LSMO, while the (110)-oriented sample reached the highest MC of approximately 65% at 300 K. These findings suggest that engineered ferroelectric/ferromagnetic heterostructures hold promise for high MC performance at room temperature and offer opportunities for modulation with crystallographic orientation, making them potentially valuable for applications in multiferroic devices.

Influence of Alloying Elements Content on High Temperature Properties of Ti-V-Cr and Ti-Al-V Series Titanium Alloys: A JMatPro Program Calculation Study

For the issues of high temperature performance affected by the alloying elements content in Ti-V-Cr and Ti-V-Cr alloys, the thermodynamic calculation method based on JMatPro program was applied in this study. The research is mainly focused on the analysis of phase composition, thermodynamic parameters and mechanical properties of Ti-Al-V and Ti-V-Cr series alloys with different element proportions under high temperature environment. Those obtained results show that the proportion of Al in Ti-Al-V alloys has a great influence on the high temperature properties. Increasing the content of Al not only increases the transformation temperature of β single-phase structure and delays the transformation process of α/β microstructure to β single-phase structure, but also helps to improve the high temperature thermal conductivity and elastic deformation resistance of the alloy. In Ti-V-Cr alloys, the influence of V element on high temperature properties is mainly focused on the improvement of thermal conductivity and high temperature deformation properties, while the influence of Cr element is relatively weak. Besides, adding a small amount of Al element to Ti-V-Cr alloy can further improve the thermal conductivity of the alloy. The Young’s modulus of the Ti-V-Cr alloy increases when 0.3%-1% of C element is added. Finally, the effect of Si element on the high temperature elastic deformation of the alloy is relatively weak.

Preparation and Performance of Resin-Gel-Rubber Expandable Lost Circulation Material Blend.

Aiming at the complex strata, lost circulation often occurs. and lost circulation control becomes a difficult issue. A drilling fluid loss accident delays the drilling progress and even causes major economic losses. If we take a self-made sodium polyacrylate grafting and modify a starch water absorbent resin, using an amphiphilic compatibilizer as raw material through mechanical blending and chemical compatibilization, we can synthesize a resin-rubber blend swelling lost circulation material. This material presents a good resistance to anti-high-temperature performance, but the quality declines while the temperature is higher than 363 °C, and with the increasing temperature, the water-swelling expansion ratio becomes higher. The range of the water-swelling expansion ratio is 8 to 25 times and the water swelling rate becomes larger along with the reduced diameter of the lost circulation materials and decreases with the increasing salinity. The resin-rubber blend swelling lost circulation material after water swelling has excellent toughness and high elastic deformation capacity, thus, forming a 7 Mpa to 2 mm fracture via expansion, extrusion, deformation, and filling, which presents a good performance for fracture plugging and realizes the purpose of lost circulation control.

Design of double stage springs for Baja SAE type vehicles

Aiming to improve the parameters which influence the performance and ergonomics of the Komiketo Baja UFSJ prototype and to optimize its results during the Baja SAE competitions, a study proposed a new methodology to substitute linear springs for double stage spring. Springs are components with high elastic deformation’s ability that compound the automotive suspension system and they influence the vehicle dynamic performance. The experimentation consists in using the Microsoft Excel software and making a simulation of a model going through an irregular trail presenting high and low oscillation frequencies of the suspension, using MSC Adams Car® software. The test was divided in two stages, one for the operation of the vehicle with linear springs and the other for non-linear springs (double-stage springs). Then, some graphics were presented with the necessary data, aiming to compare the behavior of both suspension conditions, where the vertical acceleration was considered as a comparative criterion. The results were promising presenting improvements as the ergonomics parameters, regarding the linear springs previously used in the vehicle.

Analysis of stress and strain concentration around a centralized elliptical hole in a monodomain liquid crystal elastomer sheet

Liquid crystal elastomers (LCEs) are a kind of soft materials which couple the high elastic deformability with the unique properties of liquid crystals. Such combination endows notched LCEs unusual stress and strain concentration behaviors, which is preliminary discussed by us in the case of a large sheet with a centralized circular hole. Here we extend our study from circular holes to more generalized, elliptical holes. We investigate the stress and strain fields around a centralized elliptical hole in a LCE sheet subjected to uniaxial stretches by finite element methods. The effects of the shape factor, defined as the ratio of the minor-to-major axis of the ellipse, are mainly concerned. Compared with common elastomers like neoHookean, LCEs get higher stress and strain concentration factors (SCFs), and the location of maximal strain deviates slightly from that of maximal stress. With the decrease of the shape factor (a sharper ellipse) the SCFs of LCEs rise much severer than those of neoHookean, and the deviation is diminishing. In addition, as the stretch increases, the region near the root is getting close to an approximately uniaxial stress state, and the high strain region will extend non-monotonously along the hole edge, which differs from a monotonous extension of the high stress region. All the unusual behaviors of LCEs above are attributed to the spontaneous strain induced by director rotation. Attempts to correlate stress and strain concentration behaviors to the spontaneous strain are made in this article.

Thermal Analysis of a Uniaxial Carbon Fabric Reinforced Silicone Resin

This study, which focuses on carbon fibre (CF) reinforced silicone matrix composites (CFRS-C), an alternative to conventional polymer matrix composites, aims to understand their thermal properties better. Silicone elastomer’s high elastic deformation capability is the primary factor in the choice of silicone matrix. The aforementioned materials are particularly appealing in the design of deployable systems used in the aircraft sector due to their folding capability. Better adhesion of silicone elastomer and plain weave carbon fibre fabric was succeeded by modifying the surface of the fabrics inside 20 wt.% nitric acid solution. Thermal Gravimetry (TG) and Differential Scanning Calorimetry (DSC) were used to examine the materials’ thermal properties in this study’s scope. Thermal tests showed that composite materials exhibited thermal resistance up to 368◦C. The silicone components utilized in the study can form carbon fibre-reinforced composites that exhibit thermal stability up to the specified temperature. The use of carbon fibre enhanced the thermal stability of silicone elastomers. Additionally, a change in the number of layers impacts the composite’s thermal stability.

Highly Thermally Conductive Adhesion Elastomer Enhanced by Vertically Aligned Folded Graphene.

Heat and stress transfer at an interface are crucial for the contact-based tactile sensing to measure the temperature, morphology, and modulus. However, fabricating a smart sensing material that combines high thermal conductivity, elasticity, and good adhesion is challenging. In this study, a composite is fabricated using a directional template of vertically aligned folded graphene (VAFG) and a copolymer matrix of poly-2-[[(butylamino)carbonyl]oxy]ethyl ester and polydimethylsiloxane, vinyl-end-terminated polydimethylsiloxane (poly(PBAx-ran-PDMS)). With optimized chemical cross-linking and supermolecular interactions, the poly(PBA-ran-PDMS)/VAFG exhibits high thermal conductivity (15.49W m-1 K-1 ), an high elastic deformation, and an interfacial adhesion of up to 6500 N m-1 . Poly(PBA-ran-PDMS)/VAFG is highly sensitive to temperature and pressure and demonstrates a self-learning capacity for manipulator applications. The smart manipulator can distinguish and selectively capture unknown materials in the dark. Thermally conductive, elastic, and adhesive poly(PBA-ran-PDMS)/VAFG can be developed into core materials in intelligent soft robots.

Mechanical properties and failure mechanisms of Mg-Zn-Y alloys with different extrusion ratio and LPSO volume fraction

In long period stacking ordered (LPSO) phase containing Mg-Zn-Y alloys, high elastic modulus and deformation kinks of LPSO phase considerably enhance the tensile yield strength, with slight detriment of or benefit to the ductility depending on its volume fraction. In present work, uniaxial tensile tests and fracture toughness tests are carried out using Mg 99.2 Zn 0.2 Y 0.6 , Mg 97 Zn 1 Y 2 , Mg 89 Zn 4 Y 7 and Mg 85 Zn 6 Y 9 (at % ) materials with different extrusion ratios. Extrusion processing enhances both strength and ductility due to the recrystallization of Mg grains. Variable plastic deformation mechanisms are activated depending on volume fraction of Mg and LPSO phase as well as their relative size during bending. { 10 1 ¯ 2 } 〈 10 1 ¯ 1 ¯ 〉 tensile twins in Mg grains and deformation kinks in LPSO phase are observed, which dissipate large amount of deformation energy favoring for toughness. However, inherently brittle LPSO phase is detrimental to toughness. Microstructure-motivated empirical models for yield strength and fracture toughness prediction based on rule of mixtures are calibrated by experimental data. Energy release rates of individual mechanisms are estimated, which quantitatively indicate strong Mg/LPSO interaction.

Three-dimensional boron nitride reinforced thermal conductive composites with high elasticity

Polymer-based thermally conductive composites have good interfacial contact, processability and stability. However, because of the low thermal conductivity of polymer materials, usually, a larger percentage of filler is required to achieve high thermal conductivity, which leads to a drop in the resilience of the composite. To solve this problem, a melamine-formaldehyde resin sponge (MS) was used as a skeleton to wrap boron nitride nanosheets (BNNS) through repeated layering assembly, successfully preparing a three-dimensional (3D) boron nitride network (BNNS@MS). The mixture of poly(vinylidene fluoride) and BNNS (PVDF/BNNS) was formed in the pores of the 3D network of BNNS@MS. Due to the existence of the continuous phonon conduction network, the BNNS@MS/PVDF exhibits good thermal conductivity and high elastic deformation (rebound at 90% compression). When the content of BNNS is about 5 wt%, the thermal conductivity of the BNNS@MS/PVDF is increased to 1.43 ± 0.2 W/mK, 51.1% higher than that of PVDF/BNNS. The solid heat conduction network and polymer interplay to achieve good thermal management ability, and the composites have an important application prospect in the field of wearable flexible electronic thermal management.

Mechanisms of near-linear elastic deformation behavior in a binary metastable β-type Ti-Nb alloy with large recoverable strain

A binary metastable β-type Ti-Nb alloy possessing large near-linear recoverable strain was designed to clarify the physical mechanisms responsible for high near-linear elastic deformability in near‑oxygen-free Ti-based alloys. The in situ synchrotron X-ray diffraction (SXRD) investigation reveals that in addition to the inherent elastic deformation, a reversible β↔α'' stress-induced martensitic transformation (SIMT) occurs during the near-linear elastic deformation. During the SIMT, the α'' martensitic variant 5 (V5) forms preferentially due to its maximum phase transformation strains among all 6 equivalent α'' variants. The orientation dependence of phase transformation strains of the preferential V5 leads to the appearance of different α'' diffraction peaks in the loading and Poisson’s directions during the SIMT, which is beneficial for accommodating the external macroscopic deformation to the great extent. Our experimental results show that the high near-linear elastic deformability of present Ti-Nb alloy is attributed to a combined effect of the large inherent elastic deformation arising from low Young's modulus as well as a reversible SIMT that covers a wide stress range and exhibits small phase transformation strains limited by the lattice constants of β and α'' phases. These results could provide a comprehensive understanding of the mechanisms responsible for huge near-linear elastic deformability of β-type titanium alloys.

Features of PVC/ABS compositions filling

The work is devoted to the filling of PVC (polyvinyl chloride) compositions modified with ABS (acrylonitrile-butadiene styrene) in a wide concentration range, intended for the production of profiles and moldings of various functional purposes, with short-fiber basalt fiber. Powdered samples were made by extrusion (in the form of flat profiles) and by thermoplasticizing on rolls (in the form of films). Introduction of 10-40 phr ABS in PVC formulation makes it easier to recycle the composition. Similar situation is observed when these compositions are filled with basalt fiber, which leads to insignificant decrease of MFR (melt flow index) and thermal stability, which in general does not reflect negatively on melt flow conditions, at the same time extrudate swelling index decreases by 10-15%, which indicates possibility to provide products with more precise geometric dimensions. The change in the supramolecular structure was evaluated by thermomechanical tests and by energy dispersive analysis using electron microscopy data. Thermomechanical analysis showed that the presence of large doses of ABS has a positive effect on the technological properties, leading to an earlier development of highly elastic deformations and a decrease in the yield point of the compositions. Basalt fiber contributes to an insignificant decrease in the value of high elastic deformations and an increase in the density index of meshing knots. Energy dispersion analysis has shown that introduction of basalt fiber leads to formation of homogeneous structure of PVC at lower concentrations of ABS in the composition, influencing on increase of melt flowability and thermal stability. Improved technological properties of PVC compositions filled with short-fiber basalt fiber, modified with different concentrations of ABS, allow to recommend them for production of a wide range of profile and molded products.

Enhanced biaxial stretchability of wrinkled SiO2 thin films for stretchable encapsulation

Enhanced biaxial stretchability of highly impermeable SiO2 encapsulation thin film with wrinkle structures is demonstrated. Submicron-thick SiO2 films are grown on single-crystalline Si wafers to endure local strain on wrinkled film, and their high elastic deformation limit stabilizes wrinkle structure. SiO2 films are transferred onto prestrained elastomer, and two types of wrinkle structures are formed by removal of the prestrain: aligned wrinkles by uniaxial prestrain and random wrinkles by equibiaxial prestrain. The stretchability of the large area film is correlated with the unwrinkling of individual wrinkles, and a mechanics model is suggested to predict stretchability with parameters of wrinkle morphology as well as elastic properties of the encapsulation film and the elastomer substrate.

A hard yet tough CrAlSiN nanocomposite coating for blades deposited by filtered cathode vacuum arc

Hard yet tough nanocomposite coatings with simultaneously high plastic deformation resistance and elastic deformation recovery capacity represent a new class of compressor protective coatings, which are vital for its serviceability in high sand dust environments due to the blocking effect of nanocrystalline amorphous structure on dislocation and crack. In this work, a set of CrAlSiN (nc-(Cr,Al)N/a-Si3N4) nanocomposite coatings was deposited by the filtered cathodic vacuum arc under various nitrogen fluxes. The as-deposited coatings exhibited refined grain size, well-defined nanocrystalline/amorphous phase separation, and highly dense architecture. These features allowed the achievement of the increased properties in terms of high hardness (H = 40.4 GPa) and toughness (H/E* = 0.095, H3/E*2 = 0.367) when the nitrogen flux was 100 sccm. Hard yet tough CrAlSiN nanocomposite coating showed excellent scratch response and tribological properties by enhanced cooperative deformability through increased H, H/E*, and H3/E*2, local epitaxial growth at interface and annihilation of crack and dislocation multiplication sources in grain boundaries to reduce crack initiation and propagation, and adhesion failure.

Thermally conductive, self-healing, and elastic Polyimide@Vertically aligned carbon nanotubes composite as smart thermal interface material

Smart thermal interface materials must exhibit self-healability and high thermal conductivity (k) and elastic deformation as they can experience repeated compression and undergo sudden damage. However, it remains challenging to ensure high phonon mobility/efficient phonon transfer, self-healing, and good elasticity by optimizing its molecular orientation or cross-links. Herein, a self-healing and elastic polyimide copolymer (EMPI) cross-linked by flexible and rigid segments is uniformly filled into the gaps of a forest of vertically aligned carbon nanotubes (VACNTs). The EMPI@VACNTs composite exhibits a high k value at 10.83 ± 0.22 W m−1 K−1, low interfacial thermal resistance at 6.83 ± 0.15 K mm2 W−1, high elastic compressive deformation (30% at 2.5 MPa), and strong surface adhesion (0.3 MPa). Further, it could recover 90.8% of its elastic modulus and 92% of its thermal resistance after self-healing at 80 °C for 80 h. An EMPI@VACNTs-Cu device exhibits efficient heat conduction not only by recovering after gradient compressive strains of up to 30% but also by self-healing its damage or reforming the interface with Cu. Thus, the thermally conductive, self-healing, and elastic EMPI@VACNTs composite opens new avenues for smart thermal management in various high-power/intelligent devices.

Toughening mechanism of PP/EPR/SiO2 composites with superior low-temperature toughness

Although it has been shown that the brittle-ductile transition temperature (Tbd) of rubber-toughened thermoplastics can be effectively reduced by introducing nanoparticles, the toughening mechanism is still unknown. In this work isotactic polypropylene/ethylene propylene rubber/silica nanoparticles (iPP/EPR/SiO2) composites with excellent low-temperature toughness were prepared. It was found that Tbd could be regulated synergistically by EPR and SiO2. The phase morphology showed that as silica content increased, the interface area between PP matrix and EPR dispersed phase gradually became larger. Moreover, Tbd continued to decrease with the increase of the area of EPR relaxation peak which was due to the expansion of the interface area. According to the results of impact fracture surfaces of the composites, it was found that for composites with greater EPR relaxation peak area, yielding deformation of their matrices was more intense after low-temperature impact test. Thus, a toughening mechanism for iPP/EPR/SiO2 composites at low-temperature was proposed: the internal friction loss induced by the increased phase interfacial area between EPR and iPP matrix attenuated the velocity of the impact force, as a result, compelling high-elastic deformation occurred in iPP matrix which ultimately made the composite to behave as ductile fracture at low temperatures.

DLC (H) coated 13Cr SMSS by high-pulsed power CVD technique

ABSTRACT Hydrogenated diamond-like carbon (DLC: H) films were successfully fabricated on the surface of 13Cr super martensitic stainless steel by high-pulsed power chemical vapour deposition. The mechanical and tribological properties of the films related to the substrate bias voltages were investigated. The results showed that the surface hardness and tribological properties of the substrate after DLC film deposition were improved. The DLC films became dense, the grain size and roughness reduced, and the deposition rates increased as the bias voltage increased. In addition, the dense DLC films directly led to high nanohardness and elastic modulus. The H content decreased with an increase in the bias voltage, which may be the primary reason for nanohardness and modulus enhancement. Due to the relatively high H/E* and H 2/E*3 ratios of films corresponded to high elastic strain and plastic deformation resistances reduced the wear loss, and the localized graphitization on the surface provided solid lubrication.

Quasi-elastic deformation with rebound resilience in bulk amorphous Al2O3–ZrO2–Y2O3 at moderate temperature

Large quasi-elastic deformation with high degree of rebound resilience was reported in dense, monolithic ceramics for the first time, which was achieved in the cyclic compression-resilience tests on bulk amorphous Al2O3–ZrO2–Y2O3 at 600 °C. As the compression strain was 4%, the resilience ratios in the three cycles were 89.5%, 100% and 100%, respectively; for compression strain of 8%, the resilience ratios were 74.5%, 90.6% and 92.0%. The superior elastic deformation in amorphous Al2O3–ZrO2–Y2O3 was due to the round trip migration of atoms through free volume in amorphous phase, and the residual strain after deformation of 4% and 8% are resulted from structural densification and shear band formation, respectively. This work could inspire new guidance on elastic deformation in ceramics, and provide new guidance to ceramic materials with high elastic deformation and rebound resilience in engineering applications.

Elastic and biodegradable chitosan/agarose film revealing slightly acidic pH for potential applications in regenerative medicine as artificial skin graft

The aim of this work was to develop new method for the production of chitosan/agarose (CHN/A) film that could serve as a potential artificial skin substitute for regenerative medicine applications. Within this new production method, the concentrations of biomaterial components (chitosan in CH3COOH and agarose in NaOH) were optimized to provide neutralization of the resultant mixture up to pH approx. 6.0 without uncontrolled precipitation (gelation) of chitosan constituent. Produced thin film was subjected to comprehensive evaluation of its biomedical potential by determination of mechanical, physicochemical, and biological properties. It was demonstrated that the developed CHN/A film reveals slightly acidic pH of 5.98 known to support skin regeneration, high exudate absorption capacity, and is prone to biodegradation in simulated enzymatic wound environment. Performed tensile test proved high elastic deformations of the film (Young's modulus = 0.02 MPa, elongation at break = 23%) in a wet state, which would allow suitable stretching after application at the wound site. Moreover, novel biomaterial is non-toxic and supports fibroblast growth on its surface. Based on the obtained results it may be concluded that the produced CHN/A film possesses all necessary features of the artificial skin substitute.