Changes In Mechanical Properties Research Articles

The Viability of the Refractory High‐Entropy Alloy AlMo0.5NbTa0.5TiZr for High‐Temperature Structural Applications

There is significant motivation to produce new structural materials for high‐temperature service, so that enhanced efficiencies can be realized for next‐generation power and propulsion applications. High‐entropy alloys incorporating refractory elements have been shown to be a viable source of potential new materials for these applications. Despite this, significant work is required in order to evaluate the suitability of these materials for operation in extreme environments of temperature and mechanical load. Herein, AlMo0.5NbTa0.5TiZr alloy is first reported on, for the first time providing an in situ determination of the B2 solvus, correlated to the changes in mechanical properties. In addition, a low‐temperature (800 °C) regime of catastrophic accelerated oxidation is identified, which is discussed in context of the potential future applications for this alloy. These results highlight significant limitations in AlMo0.5NbTa0.5TiZr and related alloys, which make them unsuitable for commercial application in their current form.

Molecular Design for Dual Circularity: Polyester with Complementary Mechanical and Chemical Recyclability under Mild Conditions.

The plastic waste accumulation requires facile yet effective solutions. Currently mechanical recycling typically leads to downcycling, while the environmental footprint of chemical recycling is often unacceptable. Here, we introduce a dual circularity concept, where rational molecular design paves the way for complementary closed-loop mechanical and chemical recyclability under mild conditions. Very small changes in macromolecular structures, thermal and mechanical properties were observed, after as many as six repeated mechanical recycling cycles, showing that a wide processing window could be the key for closing the mechanical recycling loop. Facile, time and energy efficient closed-loop chemical recycling into products with identical performance to original ones was also realized, thanks to the abundant free volume and accessible ester-functionalities. With these design criteria at hand, dual circulation in recyclability can be realized; proceeding with mechanical recycling when we can, and switching to chemical recycling when we must.

Molecular Design for Dual Circularity: Polyester with Complementary Mechanical and Chemical Recyclability under Mild Conditions

The plastic waste accumulation requires facile yet effective solutions. Currently mechanical recycling typically leads to downcycling, while the environmental footprint of chemical recycling is often unacceptable. Here, we introduce a dual circularity concept, where rational molecular design paves the way for complementary closed‐loop mechanical and chemical recyclability under mild conditions. Very small changes in macromolecular structures, thermal and mechanical properties were observed, after as many as six repeated mechanical recycling cycles, showing that a wide processing window could be the key for closing the mechanical recycling loop. Facile, time and energy efficient closed‐loop chemical recycling into products with identical performance to original ones was also realized, thanks to the abundant free volume and accessible ester‐functionalities. With these design criteria at hand, dual circulation in recyclability can be realized; proceeding with mechanical recycling when we can, and switching to chemical recycling when we must.

Freeze-Cast Composites of Alginate/Pyrophosphate-Stabilized Amorphous Calcium Carbonate: From the Nanoscale Structuration to the Macroscopic Properties.

Pyrophosphate-stabilized amorphous calcium carbonates (PyACC) are promising compounds for bone repair due to their ability to release calcium, carbonate, and phosphate ions following pyrophosphate hydrolysis. However, shaping these metastable and brittle materials using conventional methods remains a challenge, especially in the form of macroporous scaffolds, yet essential to promote cell colonization. To overcome these limitations, this article describes for the first time the design and multiscale characterization of freeze-cast alginate (Alg)-PyACC nanocomposite scaffolds. The study initially focused on the synthesis of Alg-PyACC powder through in situ coprecipitation. The presence of alginate chains in the vicinity of the PyACC was shown to affect both the powder reactivity and the release of calcium ions when placed in water (XRD, chemical titrations). In vitro cellular assays confirmed the biocompatibility of Alg-PyACC powder, supporting its use as a filler in scaffolds for bone substitutes. In a second step, the freeze-casting process was carried out using these precursor powders with varying rates of inorganic fillers. The resulting scaffolds were compared in terms of pore size and gradient (via SEM, X-ray microtomography, and mercury intrusion porosimetry). All scaffolds exhibited a pore size gradient oriented along the solidification axis, featuring unidirectional, lamellar, and interconnected pores. Interestingly, we found that the pore size and wall thickness could be controlled by the filler rate. This effect was attributed to the in situ cross-linking of alginate chains by released Ca2+ ions from the fillers, which increased viscosity, affecting temperature-driven segregation during the freezing step. Different multiscale organizations of the porosity and spatial distribution of fillers (FEG-SEM) were correlated with changes in the scaffold mechanical properties (tested via uniaxial compression). With such tunable porous and mechanical properties, Alg-PyACC composite scaffolds present attractive opportunities for specific bone substitute applications.

Stem cell mechanoadaptation. II. Microtubule stabilization and substrate compliance effects on cytoskeletal remodeling.

Stem cells adapt to their local mechanical environment by rearranging their cytoskeleton, which underpins the evolution of their shape and fate as well as the emergence of tissue structure and function. Here, in the second part of a two-part experimental series, we aimed to elucidate spatiotemporal cytoskeletal remodeling and resulting changes in morphology and mechanical properties of cells and their nuclei. Akin to mechanical testing of the most basic living and adapting unit of life, i.e., the cell, in situ in model tissue templates, we probed native and microtubule-stabilized (via Paclitaxel, PAX, exposure) stem cells' cytoskeletal adaptation capacity on substrates of increasing compliance (exerting local tension on cells) and with increased target seeding densities (exerting local compression on cells). On 10 and 100 kPa gels, cells seeded at 5000 cells/cm2 and cells proliferated to 15 000 cells/cm2 exhibited bulk moduli that nearly matched those of their respective substrates; hence, they exhibited a greater increase in Young's Modulus after microtubule stabilization than cells cultured on glass. Culture on compliant substrates also reduced microtubule-stabilized cells' F-actin, and microtubule concentration increases compared to cells seeded on glass. On gels, F-actin alignment decreased as more randomly oriented, short actin crosslinks were observed, representing emergent adaptation to the compliant substrate, mediated through myosin II contractility. We conclude that stem cell adaptation to compliant substrates facilitates the accommodation of larger loads from the PAX-stabilized polymerizing microtubule, which, in turn, exerts a larger effect in determining cells' capacity to stiffen and remodel the cytoskeleton. Taken as a whole, these studies establish correlations between cytoskeleton and physical and mechanical parameters of stem cells. Hence, the studies progress our understanding of the dynamic cytoskeleton as well as shape changes in cells and their nuclei, culminating in emergent tissue development and healing.

Influence of Powder Feed Density on Mechanical Properties and Microstructure in L-DED Additive Manufactured STS316L

Laser Directed Energy Deposition (L-DED) is a notable additive manufacturing method in which metal powder is sprayed through a nozzle and then consolidated layer by layer using a laser. Unlike other additive manufacturing processes, DED has fewer constraints on the size of the fabricated parts, making it advantageous for the production of large-scale components. However, the use of DED in additive manufacturing requires careful optimization of various process parameters, including laser power, powder feed rate, nozzle scanning speed, and deposition path, as these parameters significantly influence the geometry and properties of the fabricated parts. Recent studies have extensively investigated the microstructure and properties of parts fabricated via DED at different energy densities, but research on variables related to powder feed is still lacking. In this study, using Powder Line-Density (PLD) as a parameter, changes in bead geometry, microstructure and mechanical property followed by variation in powder feed density while conducting DED additive manufacturing with STS316L were observed. Controlled by powder feed rate and scanning speed, the Powder Line-Density was utilized for 1-line deposition with STS316L alloy powder, enabling the observation of bead geometry and melt-pool shape during the deposition process. Additionally, square-shaped specimens were manufactured via DED with controlled Powder LineDensity to observe the resulting microstructure and mechanical properties. It was observed that, even for the same energy density, specimens exhibited distinct grain morphologies, microstructure, and mechanical properties depending on the Powder Line-Density, with a particularly significant change in anisotropy. This highlights the importance of powder feed density as a key variable alongside energy density to optimize DED additive manufacturing processes. The findings of this study are expected to contribute to the control of anisotropy and strength of fabricated components in metal additive manufacturing processes by the regulation of powder feed density.

In-situ dual force: A novel pathway to improving the mechanical properties of resistance spot welds

Although in-situ post-weld heat treatment (PWHT) has been a viable method to modify resistance spot weld microstructure and improve joint mechanical properties, prevailing methodologies only employ post-weld current to initiate microstructural transformations. This study uses in-situ dual force (DF) and a PWHT current pulse to induce microstructural changes specifically at the edge of the fusion zone (FZ), a region prone to crack propagation. After a short cooling period following the welding cycle, the application of strain energy from the DF and thermal energy from the PWHT current resulted in the formation of new equiaxed grains via austenite recrystallization. The energy absorption capability of the weld improved by 39% after the DF schedule and 85% when DF was combined with a PWHT current. The changes in mechanical properties resulted from strain hardening induced by the DF schedule, while grain refinement from the combined DF and PWHT current schedule led to the deviation of cracks at the edge of the FZ. In contrast, the crack propagated directly into the FZ along the columnar structure in the as-welded condition. The novel application of in-situ DF extends beyond the conventional PWHT and offers a promising avenue to trigger microstructural changes in the weld which can improve mechanical performance and overall crashworthiness.

Decreased blood pressure with acute administration of quercetin in L-NAME-induced hypertensive rats.

Quercetin is known to reduce blood pressure (BP); however, its acute effects are unclear. We investigated the acute effects of quercetin on BP, aortic mechanical properties and vascular reactivity in female Sprague-Dawley (SD) rats. Hypertension was induced using L-NAME (40 mg/kg/day). Quercetin (4.5mg/kg) was administered intravenously. Mechanical properties of the aortae were measured by echo-tracking in normotensive and hypertensive rats. L-NAME and quercetin quantities in the aorta were determined using AP-MALDI-MSI. Vascular reactivity was performed in mesenteric and renal arteries. L-NAME increased BP and PWVβ while decreasing strain. Quercetin decreased BP and ameliorated PWVβ in L-NAME-induced hypertensive rats. Ex vivo, the acetylcholine (ACh)-induced increase in tension at 100 μM was reduced in renal arteries when exposed to quercetin while phenylephrine (Phe)-induced contractile response was augmented. In quiescent rings of renal arteries incubated with L-NAME (10μM) and TRAM-34 (1μM), the ACh-induced vasoconstrictions were inhibited by quercetin. Quercetin resulted in concentration-dependent vasodilation in mesenteric arteries and increased its sensitivity to ACh-induced relaxations. Quercetin lowered BP in L-NAME-induced hypertensive rats, likely due to changes in aortic mechanical properties and relaxation of resistance arteries. Further research is warranted to clarify the acute effects of quercetin on renal arteries in this hypertensive model.

Multi-scale synchrotron X-ray scattering studies on thermo-induced changes in structural and mechanical properties of CSH/PCE composites

Multi-scale synchrotron X-ray scattering studies on thermo-induced changes in structural and mechanical properties of CSH/PCE composites

Microstructure modulation and property enhancement via an underwater induction heating treatment strategy for underwater laser-directed energy deposition of Ti-6Al-4V

ABSTRACT In this study, an underwater in-situ induction heating treatment (UIHT)was carried out to modulate microstructure and improve the performance of underwater laser-directed energy deposition (ULDED) samples. The results showed that the redistributive behaviour of alloying elements during the UIHT process promoted the α′→α + β transition. Furthermore, the high temperature enabled dislocation motion, and the heterogeneous dislocations cancelled each other out, causing a decrease in the dislocation density. Notably, the changes in mechanical properties were primarily attributed to the changes in α grain size and dislocation density. The decomposition of martensite α′, characterised by a high dislocation density, elevated the likelihood of intergranular slip. The homogeneously dispersed α + β microstructure promoted coordinated deformation during slip, enhancing the ductility of the specimen and reducing the anisotropy of its mechanical properties. This study offers valuable guidelines for microgroup tailoring and property modulation of ULDED-repaired titanium alloys.

A Review of Synthesis Methods and Applications of Zinc Oxide Nanostructures

In this review, the methods of synthesis and applications of zinc oxide nanoparticles (ZnO NPs) were presented for the period from 2002 to 2024. Zinc oxide (ZnO) has a high economic value because of its inexpensive cost, natural availability, environmental friendliness, simple manufacturing process, and so on. ZnO has developed novel laser and optoelectronic device approaches that will increase the density of data storage and the speed of optical communication recording. Because of the changes in mechanical, chemical, and optical properties with decreasing size, that is generally assumed to arise from quantum confinement effects who is scale-dependent, there is a lot of research going on with ZnO, particularly in the area of nanotechnology. Low defect density ZnO nanostructures might be useful. Because their stress may be successfully regulated via flexible relaxation on free-side surfaces rather than plastic relaxation, nanostructures are more likely to generate faultless structures than epilayers.

Size-Dependent Effects in the Modified Green–Lindsay Thermoelasticity Model: Analysis of Ultrashort Pulse Interactions in the Presence of Electromagnetic Fields

Abstract This study provides a more detailed model for wave transmission and reflection in a complex thermodynamic framework. The governing equations are developed from multiphase electromagnetic size-dependent thermoelasticity models. The main focus here is on the development of the Modified-Green Lindsay nonlocal generalized thermoelasticity model that improves previous nonlocal approaches by incorporating additional strain and temperature rate terms. This study also examines how materials react to very short pulses and the effect of external electric and magnetic fields. The highly developed nonlinear equations in this study are solved using advanced programming techniques, including an iterative approach that combines finite element methods with a Newmark time-marching scheme. The results of this work established the nonlocal heat conduction theory of generalized thermoelasticity along with nonlocal continuum theory as a new improvement and progress in the field of thermoelasticity. This model shows that without considering thermal nonlocality interactions, predictions may miss essential aspects of wave behavior. The results show that the materials experience changes in mechanical properties, particularly an increase in hardness, when exposed to stronger magnetic fields. In addition, the results show that as the duration of laser pulses decreases, the speed of wave propagation increases. Shortening the pulse duration increases the wave propagation speed, which can create steep thermal gradients. In the case of pure metals heated by ultra-short pulse lasers, the fast electron heat conduction prevents the formation of significant thermal waves, while these pulses induce more intense and localized thermal stresses. Analysis of wave propagation also shows that the return time can exceed the forward time as the waves react to applied electric and magnetic fields.

Exploring Cross‐Link Density and Additive Effects on Mechanical and Morphological Behaviors of Cross‐Linked Polymers

AbstractCross‐linked thermoset polymeric materials are widely used in various engineering applications due to their excellent mechanical properties, thermal stability, and chemical resistance. Recent research highlights the role of cross‐link density and additives in influencing segmental dynamics and thermomechanical behavior of polymers. This study employs coarse‐grained molecular dynamics (CG‐MD) simulations to explore the thermomechanical and morphologic behaviors of cross‐linked polymers with molecular additives. Specifically, it is systematically investigated how cross‐link density (c) and different additive concentrations (m) affect key glass‐forming characteristics, along with the resulting changes in mechanical and morphologic properties of network materials as they approach their glass transition temperatures (Tg). Relatively weaker interaction between the polymer network and additives can lead to additive aggregation, significantly affecting the morphology and Tg as the m increases. Increasing c leads to an increase in both Tg and fragility while increasing m decreases them. The simulation reveals that both c and m moderately influence the mechanical properties (i.e., shear and tensile modulus) of cross‐linked polymers with additives. This study provides valuable insights into how cross‐link density and additive concentrations influence glass‐forming and morphological behaviors, offering a molecular design strategy for developing advanced cross‐linked thermosets.

Peat classification by sensitivity to mechanical technogenic impacts

Relevance. The problems associated with the weakening of the bearing capacity of peat soils because of technogenic impacts are very relevant in the development of oil and gas industry facilities in the wetlands of Western Siberia. Separately taken classifications according to undrained strength and sensitivity do not reveal the peculiarities of the behavior of weak soils at the base of structures. Therefore, the authors have proposed a different scheme of their classification. It allows assessing the change in physical and mechanical properties when their natural structure is violated during engineering and geological surveys. Aim. Peat classification in the territories of Tomsk, Novosibirsk and Omsk regions according to indicators of undrained strength and sensitivity to mechanical technogenic impacts. Object. Peat soils of Western Siberia. Methods. In accordance with current standards, the research methods included the laboratory methods for determining ash content, humidity, degree of decomposition, field tests to determine the undrained strength and sensitivity coefficient of soils, the information obtained was analyzed in Excel and Statistica software packages. Results. The authors have carried out the review of russian and foreign classifications in terms of soil sensitivity, as well as methods for determining the characteristics used to calculate it and proposed a classification scheme for changes in strength indicators under mechanical influences on peat soils. The article presents the results of experimental data from field and laboratory studies of the physico-mechanical properties of the most common types of peat, their variability after technogenic impacts is estimated according to the proposed scheme using examples of well-known classifications used in the construction of roads, pipelines and for predicting vehicle cross-country ability in swampy areas. The scope of application of the proposed scheme – engineering geological survey for the design, construction, repair and reconstruction of structures – is recommended.

X-Ray Diffraction Line Broadening of Irradiated Zr-2.5Nb Alloys

The evolution of the mechanical properties of Zr-2.5Nb pressure tubing during irradiation is dependent on dislocation loop densities that are represented by the broadening of X-ray diffraction lines. Empirical models for the integral breadth of the diffraction peaks as a function of operating conditions have been developed to predict the mechanical properties of CANDU reactor pressure tubes as a function of fast neutron flux, time and temperature. Apart from predicting mechanical property changes based on integral breadth measurements, a new model has been developed to retrospectively deduce abnormal operating temperatures of ex-service pressure from the measured line broadening. The application of integral breadth measurements to assess mechanical properties and temperature variations in pressure tubes is described and discussed in terms of the implications for pressure tube integrity.

Thermal Stability of Residual Stress, Microstructure, and Mechanical Property in Shot-Peened CNT/Al-Cu-Mg Composites

To investigate the thermal stability of a shot-peened specimen and ensure the reliability operation under high temperatures, CNT/Al-Cu-Mg composites were treated by shot peening (SP) and the isothermal aging treatment. The heating temperatures were 100, 150, 200, and 250 °C. Changes in surface residual stress and the distribution along the depth were investigated. The microstructure changes were analyzed by XRD and observed by TEM. Changes in mechanical properties were characterized by microhardness. The results show that the compressive residual stress (CRS) release and the microstructure changes mainly occurred at the initial stage of heating treatment. After 128 min of isothermal aging treatment at 250 °C, the surface CRS released 91.9% and the maximum CRS released 80.9%, the surface domain size increased by 222%, and the microstrain and microhardness decreased by 49% and 27.3%, respectively. The reinforcement effect introduced by SP basically disappeared. A large number of second-phase particles, such as CNT, Al2Cu, and Al4C3, were anchored at grain boundaries, hindering dislocation movement and enhancing the thermal stability of the material. Isothermal aging treatment at 100 °C and 150 °C for a duration of 32 min is a reliable circumstance for maintaining SP reinforcement.

Non-Invasive Nanometer Resolution Assessment of Cell-Soft Hydrogel System Mechanical Properties by Scanning Ion Conductance Microscopy.

Biomimetic hydrogels have garnered increased interest due to their considerable potential for use in various fields, such as tissue engineering, 3D cell cultivation, and drug delivery. The primary challenge for applying hydrogels in tissue engineering is accurately evaluating their mechanical characteristics. In this context, we propose a method using scanning ion conductance microscopy (SICM) to determine the rigidity of living human breast cancer cells MCF-7 cells grown on a soft, self-assembled Fmoc-FF peptide hydrogel. Moreover, it is demonstrated that the map of Young's modulus distribution obtained by the SICM method allows for determining the core location. The Young's modules for MCF-7 cells decrease with the substrate stiffening, with values of 1050 Pa, 835 Pa, and 600 Pa measured on a Petri dish, Fmoc-FF hydrogel, and Fmoc-FF/chitosan hydrogel, respectively. A comparative analysis of the SICM results and the data obtained by atomic force microscopy was in good agreement, allowing for the use of a composite cell-substrate model (CoCS) to evaluate the 'soft substrate effect'. Using the CoCS model allowed us to conclude that the MCF-7 softening was due to the cells' mechanical properties variations due to cytoskeletal changes. This research provides immediate insights into changes in cell mechanical properties resulting from different soft scaffold substrates.

Use of Ultrasound to Identify Microstructure-Property Relationships in (AlN + WC) Fabricated with Electroless Ni Producing

In order to improve the properties of the materials produced by the powder metallurgy method, first of all, powders (16.59% AlN + 6.63% WC) were coated with nickel (Ni) by electroless method, and then box boriding, which is one of the most widely used surface coating methods, was applied. A composite formed with (16.59% AlN + 6.63% WC)76.7Ni was prepared under the Ar shroud in the temperature range of 1000-1400°C. Pulse-echo technique was used for ultrasonic velocity measurements on Ni coated (16.59% AlN + 6.63% WC) samples. It is aimed to examine the change of physical, mechanical and ultrasonic properties of the obtained ceramic-metal composites depending on different sintering temperatures. In addition, the samples were characterized by mechanical and metallographic examination. The results show that the longitudinal and transverse ultrasonic velocity values and ultrasonic modulus (shear, bulk, Young’s etc.) values increase simultaneously with the increase of sintering temperature. The highest microhardness value was observed in composite samples sintered at 1400°C and its value was 1150.80 Hv. The increased strength is mainly due to grain refinement and strong interfacial bonding between Ni particles and AlN and WC matrix.

Experimental Evaluation of the Effect of Degradation on the Mechanical Behavior and Morphometric Characteristics of Functionally Graded Polymer Scaffolds.

Bone transplantation ranks second worldwide among tissue prosthesis surgeries. Currently, one of the most promising approaches is regenerative medicine, which involves tissue engineering based on polymer scaffolds with biodegradable properties. Once implanted, scaffolds interact directly with the surrounding tissues and in a fairly aggressive environment, which causes biodegradation of the scaffold material. The aim of this work is to experimentally investigate the changes in the effective mechanical properties of polylactide scaffolds manufactured using additive technologies. The mechanism and the rate of the degradation process depend on the chosen material, contact area, microstructural features, and overall architecture of sample. To assess the influence of each of these factors, solid samples with different dimensions and layers orientation as well as prototypes of functionally graded scaffolds were studied. The research methodology includes the assessment of changes in the mechanical properties of the samples, as well as their structural characteristics. Changes in the mechanical properties were measured in compression tests. Microcomputed tomography (micro-CT) studies were conducted to evaluate changes in the microstructure of scaffold prototypes. Changes caused by surface erosion and their impact on degradation were assessed using morphometric analysis. Nonlinear changes in mechanical properties were observed for both solid samples and lattice graded scaffold prototypes depending on the duration of immersion in NaCl solution and exposure to different temperatures. At the temperature of 37 °C, the decrease in the elastic modulus of solid specimens was no more than 16%, while for the lattice scaffolds, it was only 4%. For expedited degradation during a higher temperature of 45 °C, these ratios were 47% and 16%, respectively. The decrease in compressive strength was no more than 32% for solid specimens and 17% for scaffolds. The results of this study may be useful for the development of optimal scaffolds considering the impact of the degradation process on their structural integrity.

Increased perfluorooctanoic acid accumulation facilitates the migration and invasion of lung cancer cells via remodeling cell mechanics

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are widely used in industrial and household products, raising serious concerns due to their environmental persistence and mobility. Epidemiological studies have reported potential carcinogenic risks of PFAS based on their widespread occurrence and population exposure. In this study, we observed that perfluorooctanoic acid (PFOA), a common PFAS, functions as a mechanical regulator in lung cancer cells. PFOA exposure reduces cell stiffness, thereby decreasing cell adhesion and enhancing immune evasion, ultimately exacerbating tumor metastasis. In various lung cancer models, more aggressive tumor metastases have been observed in the PFOA exposure group. Additionally, serum PFOA levels in patients with advanced lung adenocarcinoma were significantly higher than those in patients with early-stage disease. Mechanistically, the interaction between PFOA and transmembrane integrins in cancer cells triggers changes in cellular mechanical properties, leading to the reorganization of the cytoskeleton, and activation of the intracellular FAK-PI3K-Akt signaling pathway. Our findings demonstrate that in individuals with lung adenocarcinoma, PFOA can increase the risk of cancer metastasis even at daily exposure levels.