Effect Of Mechanical Stress Research Articles

Effect of Al Content on Microstructure and Properties of AlxCr0.2NbTiV Refractory High-Entropy Alloys.

High-temperature creep refers to the slow and continuous plastic deformation of materials under the effects of high temperatures and mechanical stress over extended periods, which can lead to the degradation or even failure of the components' functionality. AlxCr0.2NbTiV (x = 0.2, 0.5, or 0.8) refractory high-entropy alloys were fabricated by arc melting. The effects of Al content on the microstructure of AlxCr0.2NbTiV alloys were studied using X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction. The microhardness, compression properties, and nanoindentation creep properties of AlxCr0.2NbTiV alloys were also tested. The results show that the AlxCr0.2NbTiV series exhibits a BCC single-phase structure. As the Al content increases, the lattice constant of the alloys gradually decreases, and the intensity of the (110) crystal plane diffraction peak increases. Adding aluminum enhances the effect of solution strengthening; however, due to grain coarsening, the microhardness and room temperature compressive strength of the alloy are only slightly improved. Additionally, because the effect of solution strengthening is diminished at high temperatures, the compressive strength of the alloy at 1000 °C is significantly reduced. The creep mechanism of the alloys is predominantly governed by dislocation creep. Moreover, increasing the Al content helps to reduce the sensitivity of the alloy to the loading rate during the creep process. At a loading rate of 2.5 mN/s, the Al0.8Cr0.2NbTiV alloy exhibits the lowest creep strain rate sensitivity index (m), which is 0.0758.

Establishing correlation between teeth exposure to mechanical loads during orthodontic treatment and occurrence of denticles in teeth

INTRODUCTION. Treatment with braces can correct pathologies of the bite, temporomandibular joint, and improve the facial and smile aesthetics. However, along with the positive effects of braces, there are a number of negative effects, one of which is the formation of denticles caused by mechanical stress during orthodontic treatment. Understanding not only the advantages, but also the disadvantages of braces systems can minimize the negative effects of treatment with non-removable orthodontic appliances by means of modern technologies.AIM. Establishing the effects of mechanical forces applied to the tooth during orthodontic treatment with braces on the formation and growth of denticles.MATERIALS AND METHODS. 41 cone-beam computed tomograms (CBCTs) of patients aged 11 to 59 years, randomly selected, treated with non-removable orthodontic appliances for two years were studied. A total of 90 teeth were found in which pulp denticles formed primarily or grew in size. CBCT was analyzed in Planmeca Romexis Review software before and 2 years after orthodontic treatment. Findings were recognized as statistically significant at p < 0.05.RESULTS. The formation and development of denticles after wearing orthodontic appliances was observed in 87.2 % (n = 30) of cases). Primary denticle formation occurred in 46.2 % (n = 18) of cases, and an increase in denticle size was observed in 25.6 % (n = 10) of cases.CONCLUSIONS. The obtained statistical data supports the relationship between the effects of mechanical stress on teeth during orthodontic treatment and denticle formation.

Rapid determination of corrosion under fatigue loading based on tensile loading

This study tests the hypothesis that corrosion properties under fatigue loading can be evaluated based on simple tensile tests without the need to perform costly and time-consuming corrosion fatigue tests. Two types of stainless steel 304L specimens, i.e., smooth and compact tension (CT), are exposed to static and fatigue loading in two aqueous solutions with different NaCl concentrations. Strain analysis, surface roughness measurements, scanning electrochemical microscopy (SECM), and Tafel polarization techniques are employed to unveil the effects of mechanical stress and strain on the corrosion behavior at micro and macro scales, a phenomenon known as electro-chemo-mechanical interaction. Finite element analysis (FEA) is performed to calculate the stress and strain field in the specimens. Digital image correlation (DIC) is used to validate the FEA results. The results indicate a strong correlation between the static stress, strain, and surface roughness with the corrosion rate. In particular, the study reveals a strong correlation between corrosion current (and corrosion current density) under fatigue loading with that under static tensile loading, thereby providing a means to evaluate the corrosion properties under fatigue loading solely from static tests. Fatigue loading leads to a progressive reduction in the corrosion potential as the number of cycles increases. The corrosion current density, icorr, is linked to the stress and accumulated plastic strain by an empirical equation, shedding lights on the complex electro-chemo-mechanical interaction. Additionally, opportunities for future research are discussed.

Effect of mild mechanical stresses on device physics of slot-die coated flexible perovskite solar cells

Halide perovskites are a promising class of novel photoactive materials for their application in flexible photovoltaic devices. Tolerance and stability of devices to various mechanical stresses are important aspects of this technology for its effective and long-term operation. Currently, this aspect has not been fully researched and addressed by the research community. Hence, this work is aimed at studying the effect of mild mechanical stresses (MMSs) induced by convex bending on the behaviour of ITO/ZnO/MAPbI3/Spiro-OMeTAD/Au slot-die-coated flexible perovskite solar cells (FPSCs) and investigating the underlying mechanisms leading to performance degradation in devices. The carrier generation, recombination, and extraction processes within FPSCs are investigated before and after the application of MMSs. The obtained results suggest that the photovoltaic performance of the FPSCs deteriorates by up to 50% after convex bending, due to increased non-radiative recombination losses. The results obtained in this work provide some valuable insights into the dynamics of recombination processes in FPSCs exposed to MMSs and can be used for developing new strategies for improving the mechanical stability of devices.

Assessment of thermo-mechanical phenomena in Si-based diodes via operando confocal Raman microscopy

The deconvolution of the thermal and mechanical stress and other induced effects caused by the electrical current flowing through a semiconductor-based device is often quite challenging. In this work, a novel specific analysis procedure is successfully tested, based on the study of mapped regions from in situ characterization by confocal Raman microscopy. The width of Si T2g Raman mode and its position are used to determine the individual spatial distribution of all phenomena occurring in the Si chip at different current intensities. The method is applied to Si-based press-fit rectifier diodes in forward-bias conditions but can be extended to other devices. The analysis reveals the presence of several regions in the Si chip as a function of their doping level and stress magnitude. Results indicate that the Si component is subjected to a predominant thermal contribution along with other two contributions related to residual and electrically induced effects, whose values differ for each region.

Biomechanical Effects of Mechanical Stress on Cells Involved in Fracture Healing.

Fracture healing is a complex staged repair process in which the mechanical environment plays a key role. Bone tissue is very sensitive to mechanical stress stimuli, and the literature suggests that appropriate stress can promote fracture healing by altering cellular function. However, fracture healing is a coupled process involving multiple cell types that balance and limit each other to ensure proper fracture healing. The main cells that function during different stages of fracture healing are different, and the types and molecular mechanisms of stress required are also different. Most previous studies have used a single mechanical stimulus on individual mechanosensitive cells, and there is no relatively uniform standard for the size and frequency of the mechanical stress. Analyzing the mechanisms underlying the effects of mechanical stimulation on the metabolic regulation of signaling pathways in cells such as in bone marrow mesenchymal stem cells (BMSCs), osteoblasts, chondrocytes, and osteoclasts is currently a challenging research hotspot. Grasping how stress affects the function of different cells at the molecular biology level can contribute to the refined management of fracture healing. Therefore, in this review, we summarize the relevant literature and describe the effects of mechanical stress on cells associated with fracture healing, and their possible signaling pathways, for the treatment of fractures and the further development of regenerative medicine.

Moderate mechanical stress suppresses chondrocyte ferroptosis in osteoarthritis by regulating NF-κB p65/GPX4 signaling pathway

Ferroptosis is a recently identified form of programmed cell death that plays an important role in the pathophysiological process of osteoarthritis (OA). Herein, we investigated the protective effect of moderate mechanical stress on chondrocyte ferroptosis and further revealed the internal molecular mechanism. Intra-articular injection of sodium iodoacetate (MIA) was conducted to induce the rat model of OA in vivo, meanwhile, interleukin-1 beta (IL-1β) was treated to chondrocytes to induce the OA cell model in vitro. The OA phenotype was analyzed by histology and microcomputed tomography, the ferroptosis was analyzed by transmission electron microscope and immunofluorescence. The expression of ferroptosis and cartilage metabolism-related factors was analyzed by immunohistochemical and Western blot. Animal experiments revealed that moderate-intensity treadmill exercise could effectively reduce chondrocyte ferroptosis and cartilage matrix degradation in MIA-induced OA rats. Cell experiments showed that 4-h cyclic tensile strain intervention could activate Nrf2 and inhibit the NF-κB signaling pathway, increase the expression of Col2a1, GPX4, and SLC7A11, decrease the expression of MMP13 and P53, thereby restraining IL-1β-induced chondrocyte ferroptosis and degeneration. Inhibition of NF-κB signaling pathway relieved the chondrocyte ferroptosis and degeneration. Meanwhile, overexpression of NF-κB by recombinant lentivirus reversed the positive effect of CTS on chondrocytes. Moderate mechanical stress could activate the Nrf2 antioxidant system, inhibit the NF-κB p65 signaling pathway, and inhibit chondrocyte ferroptosis and cartilage matrix degradation by regulating P53, SLC7A11, and GPX4.

Effects of Mechanical Stress on the Life and Insulation Performance of DC-Link Capacitors

Mechanical stress is a crucial factor affecting the life and insulation performance of DC-link capacitors (DCLCs). However, at present, there is a lack of long-term experimental observations on the effects of mechanical stress on the life and insulation performance of DCLCs. The element-winding process for DCLCs is carried out by winding metalized film on a reel and adjusting the various winding tensions and pressures according to performance requirements, usually with a winding tension coefficient (WTC) of kT = 1.5. The pull pressure of the winding machine on the film produces tension during the elements’ winding process, and the tension in the film grows after the heat-setting process. In this study, by adjusting the four tension coefficients of the elements in the winding process, which were 1.4, 1.5, 1.6, and 1.7, various winding tensions of the DCLC components were changed. Additionally, various heat-setting shrinkage tensions were appropriately generated by setting different heat-setting temperatures (HSTs). Relevant test platforms were established, and a life aging test, insulation resistance measurement, and withstand voltage test were performed on these DCLCs at different tension coefficients and HSTs. The obtained results reveal that the mechanical stress of DCLCs is affected by the parameters of the material itself, including the tension coefficient during the winding process and the HST. The winding tension affects the life of DCLCs, such that those with the highest tension (kT = 1.7) demonstrate the longest life at an HST of 105 °C, whereas samples with the lowest tension (kT = 1.4) exhibit the longest life at an HST of 110 °C. HSTs are capable of improving the lifetime of DCLCs. HSTs are also able to improve the withstand voltage capability of DCLCs, but the tension is not proportional to the withstand voltage capability of DCLCs. This research provides a suitable basis for further explorations of the life and insulation performance of DCLCs.

Modeled microgravity unravels the roles of mechanical forces in renal progenitor cell physiology

BackgroundThe glomerulus is a highly complex system, composed of different interdependent cell types that are subjected to various mechanical stimuli. These stimuli regulate multiple cellular functions, and changes in these functions may contribute to tissue damage and disease progression. To date, our understanding of the mechanobiology of glomerular cells is limited, with most research focused on the adaptive response of podocytes. However, it is crucial to recognize the interdependence between podocytes and parietal epithelial cells, in particular with the progenitor subset, as it plays a critical role in various manifestations of glomerular diseases. This highlights the necessity to implement the analysis of the effects of mechanical stress on renal progenitor cells.MethodsMicrogravity, modeled by Rotary Cell Culture System, has been employed as a system to investigate how renal progenitor cells respond to alterations in the mechanical cues within their microenvironment. Changes in cell phenotype, cytoskeleton organization, cell proliferation, cell adhesion and cell capacity for differentiation into podocytes were analyzed.ResultsIn modeled microgravity conditions, renal progenitor cells showed altered cytoskeleton and focal adhesion organization associated with a reduction in cell proliferation, cell adhesion and spreading capacity. Moreover, mechanical forces appeared to be essential for renal progenitor differentiation into podocytes. Indeed, when renal progenitors were exposed to a differentiative agent in modeled microgravity conditions, it impaired the acquisition of a complex podocyte-like F-actin cytoskeleton and the expression of specific podocyte markers, such as nephrin and nestin. Importantly, the stabilization of the cytoskeleton with a calcineurin inhibitor, cyclosporine A, rescued the differentiation of renal progenitor cells into podocytes in modeled microgravity conditions.ConclusionsAlterations in the organization of the renal progenitor cytoskeleton due to unloading conditions negatively affect the regenerative capacity of these cells. These findings strengthen the concept that changes in mechanical cues can initiate a pathophysiological process in the glomerulus, not only altering podocyte actin cytoskeleton, but also extending the detrimental effect to the renal progenitor population. This underscores the significance of the cytoskeleton as a druggable target for kidney diseases.

Assembly technology of electronic components for e-textiles

This article deals with the issue of assembling conventional SMD components on textile substrates using UV-curable non-conductive adhesives. This technology is easily applicable in the textile industry. It thus enables the easy and fast production of e-textiles that are equipped with conventional electronic components or even entire electronic modules. The article describes the principle of this innovative technology. Furthermore, comprehensive results of testing the effect of mechanical stress, chemical cleaning, and climatic changes on e-textiles with assembled SMD components on the change in contact resistance are presented here. The results show that this technology can be used for assembling and encapsulating SMD components on a textile substrate in the realization of e-textiles.

Failure analysis of the end surface of the burner nozzle made of UMCo50 material in long-term high temperature oxygen-enriched sulfur-chlorine environment

As the core device of coal water slurry gasification technology, the failure of the burner nozzle will bring serious technical and safety problems. The purpose of this paper is to determine the mechanism of burner failure based on the characteristics of corrosion products and cracks. The results showed that the Cr2O3 oxide film on the surface of UMCo50 was damaged under the effect of mechanical erosion, high temperature and stress, and the corrosive elements S and Cl in the combustion chamber made it further cracked and peeled off. Therefore, the matrix was corroded and cracks occurred. During the crack propagation process, more M23C6 carbides were precipitated at the grain boundary, it caused Cr-depleted at the grain boundary, which reduced the corrosion resistance of the matrix near the grain boundary. The exfoliation of carbides distributed along the grain boundary also accelerated crack propagation. Through XPS and XRD analysis, it was found that the main corrosion products on the crack surface of the failed parts were: Cr2O3, CoCr2O4, CoO, Fe2O3, FeS. According to the causes of failure analysis, the corresponding improvement measures are put forward.

Unravelling the nanoscale mechanism of polarization reversal in a Hf0.5Zr0.5O2-based ferroelectric capacitor by vector piezoresponse force microscopy.

Ferroelectricity is in demand in many device concepts in electronics, energy and microsystem engineering. The performance of ferroelectrics-based devices is determined by either out-of-plane or in-plane polarization, or out-of-plane or in-plane piezoelectric strain. Real prospects for the practical implementation of innovative devices opened up after the discovery of ferroelectricity in ultrathin hafnium oxide films, due to their perfect compatibility with silicon technology. Ferroelectric properties of this material have been assigned to an orthorhombic structural phase with a single polar axis, but the spatial orientation of the polarization vector and the tensorial piezoelectric behaviour, which are inextricably coupled, still remain unknown. Herein, the rotation of the polarization vector in a Hf0.5Zr0.5O2 (10 nm) capacitor during polarization switching and the spatial distribution of longitudinal and shear piezoelectric coefficients are elucidated at the nanoscale using operando vector piezoresponse force microscopy. In most of the capacitor, a 180°-flipping of the polarization vector is observed, which is consistent with the orthorhombic phase structure. However, a rather large fraction of the capacitor is also occupied by nanoregions of ferroelastic (non-180°) switching, which is explained by the effect of the local mechanical stress. To quantify the three-dimensional piezoresponse, a novel approach exploiting the Poisson effect in artificially created non-ferroelectric regions is proposed and it shows that the shear piezoelectric coefficient is twice the longitudinal coefficient. The experimental insights entail an important step in fundamental understanding of the ferroelectric and piezoelectric properties of hafnium oxide and have great potential to trigger new versions of ferroelectric-based devices.

Bacteria-surface interactions: role of impacting bacteria-laden droplets.

Understanding the interactions of pathogenic droplets with surfaces is crucial to biomedical applications. In this study, using E. coli as the model microbe, we investigate the impact of a bacteria-laden droplet on different substrates, both bare and antimicrobial. In doing so, we unveil the significance of kinetic energy and spreading parameters of the impacting droplet in determining the microbes' proliferation capabilities. Our results indicate an inverse relationship between the impact Weber number and the bacterial ability to proliferate. We reveal that the mechanical stress generated during impact impedes the capabilities of microbes present inside the droplet to create their progeny. Following an order analysis of the mechanical stress generated, we argue that the impact does not induce lysis-driven cell death of the bacteria; rather, it promotes a stress-driven transition of viable bacteria to a viable-but-non-culturable (VBNC) state. Furthermore, variations in the concentration of particles on the antimicrobial surfaces revealed the role of the post-impact spreading behaviour in dictating bacterial proliferation capabilities. Contrary to the conventional notion, we demonstrate that during the early stages of interaction, a bare substrate may outperform an antibacterial substrate in the inactivation of the bacterial load. Finally, we present an interaction map illustrating the complex relationship between bacterial colony-forming units, bactericide concentration on the surface, and the impact Weber number. We believe that the inferences of the study, highlighting the effect of mechanical stresses on the soft cell wall of microbes, could be a useful design consideration for the development of antimicrobial surfaces.

Destabilization of Indomethacin-Paracetamol Co-Amorphous Systems by Mechanical Stress.

Using co-amorphous systems (CAMS) has shown promise in addressing the challenges associated with poorly water-soluble drugs. Quench-cooling is a commonly used CAMS preparation method, often followed by grinding or milling to achieve a fine powder that is suitable for subsequent characterization or further down-stream manufacturing. However, the impact of mechanical stress applied to CAMS has received little attention. In this study, the influence of mechanical stress on indomethacin-paracetamol CAMS was investigated. The investigation involved thermal analysis and solid-state characterization across various CAMS mixing ratios and levels of mechanical stress. The study revealed a negative effect of mechanical stress on stability, particularly on the excess components in CAMS. Higher levels of mechanical stress were observed to induce phase separation or recrystallization. Notably, samples at the optimal mixing ratio demonstrated greater resistance to the destabilization caused by mechanical stress. These results showed the significance of careful consideration of processing methods during formulation and the significance of optimizing mixing ratios in CAMS.

CdSe and CdTe Mechanical Properties Revealed by COMSOL Multiphasics

Two Metal chalcogenide compounds CdTe and CdSe have been studied in depth because they are used in many optoelectronic and electronic devices. High pressure causes structural phase transitions in semiconductor materials, which have been the subject of much research. CdTe is a direct band-gap IIeVI semiconductor. Cadmium-tellurium crystalline compound has been used in more and more industries. High dislocation density is one of the problems with bulk-grown CdTe. Comsol Multiphysics was used to evaluate mechanical stress on a material. COMSOL Multiphysics 5.5 allows you to access a database of physics simulations. (CdSe and CdTe) were simulated to show the effects of mechanical stress. We use a physical model called Solid Mechanics to model the effect of mechanical stress. The results show that when pressure was applied at different levels (50pa, 100pa, 200pa, 300pa, 400pa), the strain values of (CdSe or CdTe) were similar, but (CdSe) was more resistant to deformation than (CdTe).

Consideration of tensile stress in the ODF-based approach for modelling the first magnetization curves of Grain-Oriented Electrical Steels

Grain-oriented electrical steels (GOES) are extensively utilized in power transformers to enhance energy efficiency and reduce their size and weight. GOES are characterized by their strong magnetic anisotropy, leading to distinct magnetic characteristics (behavior law and iron losses) according to the direction and the intensity of the applied field with respect to the rolling direction (RD). The Orientation Distribution Function (ODF) based approach is a convenient method for describing the anisotropy of the GOES behavior law owing to its ease of identification and implementation. However, it exhibits a significant oscillation issue at low magnetic fields. To address this issue, a high-order ODF-based method has been proposed in the literature. In this article, the ODF-based model, initially stress-free, is extended to include the effects of mechanical tensile stress on the first magnetization curves of a conventional GOES. An ODF-based model considering both magnetic anisotropy and mechanical tensile stress is then proposed. The results are discussed and compared with experimental data.

Effect of mechanical properties, microstructure and residual stress on the bending springback behavior of high-strength Al–Mg–Si–Cu alloy tubes

In this work, the bending behavior of high-strength Al–Mg–Si–Cu alloys and AA6061 under different artificial aging condition was investigated. The existing springback prediction formula is suitable for commercial AA6061 alloy, but not for high-strength Al–Mg–Si–Cu alloy. Subsequently, the microstructure, mechanical properties and residual stress of AA6061 and high-strength Al– Mg–Si–Cu alloys were investigated. The results show that the yield strength and residual stress play important roles on the springback of high-strength Al–Mg–Si–Cu alloy. In addition, a springback prediction formula based on residual tensile stress has been proposed, which makes the prediction accuracy higher than 96 %. This provides theoretical guidance and data support for the application of high-strength Al–Mg–Si–Cu alloys in lightweight automotive materials.

Research on time-varying degradation of RC buildings coupled environmental effects and corrosion-induced damage from multi-scale

Corrosion of steel reinforcement in reinforced concrete (RC) buildings is influenced by several factors, including oxygen content, chloride ion diffusion, concrete damage, and humidity. A numerical method is presented to evaluate the long-term structural performance of RC buildings under environmental conditions, which takes into account the impact of steel corrosion-induced damage from multi-scale. The macro-index used for calculation is the level of reinforcement corrosion-induced damage, which considers the inter-connected effects of oxygen content, chloride ion, moisture transport, mechanical stresses, and corrosion uncertainties. In the case of RC beams, corrosion tends to occur more severely on the outer edge near concrete surface. When the corrosion factor is taken as 1.0, the calculated compression side corrosion rate of RC beam agrees well with experimental results. Due to the influence of multiple factors, the corrosion of tension-side reinforcement exhibits some degree of variability. Furthermore, the corrosion of tension-side longitudinal reinforcement in RC beams gradually intensifies from beam ends towards mid-span, with corrosion at mid-span being particularly significant. The relationship between corrosion rate and corrosion time obtained from tests falls within the range of calculation results, and the calculated results from micro-scale align favorably with tests conducted to measure crack width.

Straining the root on and off triggers local calcium signalling.

A fundamental function of an organ is the ability to perceive mechanical cues. Yet, how this is accomplished is not fully understood, particularly in plant roots. In plants, the majority of studies dealing with the effects of mechanical stress have investigated the aerial parts. However, in natural conditions roots are also subjected to mechanical cues, for example when the root encounters a hard obstacle during its growth or when the soil settles. To investigate root cellular responses to root compression, we developed a microfluidic system associated with a microvalve allowing the delivery of controlled and reproducible mechanical stimulations to the root. In this study, examining plants expressing the R-GECO1-mTurquoise calcium reporter, we addressed the root cell deformation and calcium increase induced by the mechanical stimulation. Lateral pressure applied on the root induced a moderate elastic deformation of root cortical cells and elicited a multicomponent calcium signal at the onset of the pressure pulse, followed by a second one at the release of the pressure. This indicates that straining rather than stressing of tissues is relevant to trigger the calcium signal. Although the intensity of the calcium response increases with the pressure applied, successive pressure stimuli led to a remarkable attenuation of the calcium signal. The calcium elevation was restricted to the tissue under pressure and did not propagate. Strain sensing, spatial restriction and habituation to repetitive stimulation represent the fundamental properties of root signalling in response to local mechanical stimulation. These data linking mechanical properties of root cells to calcium elevation contribute to elucidating the pathway allowing the root to adapt to the mechanical cues generated by the soil.

The Effect of Mechanical Stress on Hyaluronan Fragments' Inflammatory Cascade: Clinical Implications.

It is a common experience, reported by patients who have undergone manual therapy that uses deep friction, to perceive soreness in treatment areas; however, it is still not clear what causes it and if it is therapeutically useful or a simple side effect. The purpose of this narrative review is to determine whether manual and physical therapies can catalyze an inflammatory process driven by HA fragments. The literature supports the hypothesis that mechanical stress can depolymerize into small pieces at low molecular weight and have a high inflammatory capacity. Many of these pieces are then further degraded into small oligosaccharides. Recently, it has been demonstrated that oligosaccharides are able to stop this inflammatory process. These data support the hypothesis that manual therapy that uses deep friction could metabolize self-aggregated HA chains responsible for increasing loose connective tissue viscosity, catalyzing a local HA fragment cascade that will generate soreness but, at the same time, facilitate the reconstitution of the physiological loose connective tissue properties. This information can help to explain the meaning of the inflammatory process as well as the requirement for it for the long-lasting resolution of these alterations.