Softening Of Matrix Research Articles

Investigation of wear mechanisms in multi‐scale short carbon fiber reinforced PTFE composites for blade rotor volumetric pumps in variable lubrications

AbstractTo address bearing material damage in the Blade Rotor Volumetric Pump, We proposed a preparation method for multi‐scale short carbon fibers (SCFs) reinforced PTFE composites, which exhibited excellent tribological properties under water lubrication. However, its performance under other lubrication conditions remains insufficiently explored. Therefore, this study investigates the tribological behavior of h‐BN/5 wt% SSCFs/10 wt% LSCFs/80 wt% PTFE composites under diverse lubrication conditions (dry friction, deionized water, and seawater) with varying loads (2–4 MPa) and velocities (0.25–0.75 m/s). The composite demonstrates exceptional wear resistance across all conditions, achieving specific wear rates within the 10−6 mm3/(N•m) range. The results reveal superior performance under water lubrication with the lowest specific wear rate (1.21 ± 0.28 × 10−6 mm3/(N•m)), contrasting with seawater lubrication's maximum value (4.55 ± 0.72 × 10−6 mm3/(N•m)). Notably, the composite maintains a remarkably low friction coefficient of 0.036 under seawater lubrication at 3 MPa‐0.25 m/s. Distinct wear mechanisms emerge across conditions: Dry friction induces thermal softening of the composite matrix and interfacial weakening between SSCFs and PTFE, reducing the direct contact area by forming a transfer film on the duplex stainless steel disc. Water lubrication facilitates self‐reconstruction of SSCFs, achieving greater than 20% surface coverage through self‐directed and enriched short carbon fibers, synergizing with interfacial water films to establish boundary/fluid lubrication states. Seawater conditions introduce dual effects‐while maintaining water lubrication benefits, precipitated inorganic salts (primarily NaCl) generate abrasive wear, causing plowing marks on the friction surface, though salt films provide supplementary lubrication. The chemical reaction of seawater elements on DSS surfaces, together with inorganic salt particles, causes fluctuations in the friction coefficient. Temporal evolution analysis shows load/speed‐dependent friction trends: dry friction exhibits friction coefficient increases with ascending speed/load, water lubrication demonstrates initial reduction followed by increase, while seawater maintains stable coefficients across speed variations. All lubrication conditions involve SSCFs self‐reconstructing, which achieves alignment and enrichment of SSCFs along the sliding direction on the friction surface of the pin, thereby improving the wear resistance of composites.Highlights The multi‐scale SCFs hybrid strategy is effective and reliable. Excellent wear resistance is observed under various lubrication conditions. SSCFs' self‐reconstruction during friction enhances wear resistance. Seawater lubrication causes abrasive wear due to salt particle precipitation.

Mechanistic insights into hydration-driven shape memory response in keratinous avian feather structures.

Mechanistic insights into hydration-driven shape memory response in keratinous avian feather structures.

Histone H2A.Z Deacetylation and Dedifferentiation in Infarcted/Tip60-depleted Cardiomyocytes.

Myocardial infarction (MI) results in the loss of billions of cardiomyocytes (CMs), resulting in cardiac dysfunction. To re-muscularize injured myocardium, new CMs must be generated via renewed proliferation of surviving CMs. Approaches to induce proliferation of CMs after injury have been insufficient. Toward this end we are targeting the acetyltransferase Tip60, encoded by the Kat5 gene, based on the rationale that its pleiotropic functions combine to block CM proliferation at multiple checkpoints. We previously demonstrated that genetic depletion of Tip60 in a mouse model after MI reduces scarring, retains cardiac function, and activates the CM cell-cycle, although it remains unclear whether this culminates in the generation of daughter CMs. In order for pre-existing CMs in the adult heart to undergo proliferation, it has become accepted that they must first dedifferentiate, a process highlighted by loss of maturity, epithelial to mesenchymal transitioning (EMT), and reversion from fatty acid oxidation to glycolytic metabolism, accompanied by softening of the myocardial extracellular matrix (ECM). Based on recently published findings that Tip60 induces and maintains the differentiated state of hematopoietic stem cells and neurons via site-specific acetylation of the histone variant H2A.Z, we assessed levels of acetylated H2A.Z and dedifferentiation markers after depleting Tip60 in CMs post-MI. We report that genetic depletion of Tip60 from CMs after MI results in the near obliteration of acetylated H2A.Z in CM nuclei, accompanied by the altered expression of genes indicative of EMT induction, ECM softening, decreased fatty acid oxidation, and depressed expression of genes that regulate the TCA cycle. In accord with the possibility that site-specific acetylation of H2A.Z maintains adult CMs in a mature state of differentiation, CUT&Tag revealed enrichment of H2A.ZacK4/K7 in genetic motifs and in GO terms respectively associated with CM transcription factor binding and muscle development/differentiation. Along with our previous findings, these results support the notion that Tip60 has multiple targets in CMs that combine to maintain the differentiated state and prevent proliferation.

Synergistic Anticancer Strategy Targeting ECM Stiffness: Integration of Matrix Softening and Mechanical Signal Transduction Blockade in Primary Liver Cancers.

The development of primary liver cancer (hepatocellular carcinoma [HCC] and intrahepatic cholangiocarcinoma [ICC]) is linked to its physical microenvironment, particularly extracellular matrix (ECM) stiffness. Potential anticancer strategies targeting ECM stiffness include prevention/reversal of the stiffening process and disruption of the response of cancer cells to mechanical signals from ECM. However, each strategy has limitations. Therefore, the authors propose integrating them to maximize their strengths. Compared with HCC, ICC has a stiffer ECM and a worse prognosis. Therefore, ICC is selected to investigate mechanisms underlying the influence of ECM stiffness on cancer progression and application of the integrated anticancer strategy targeting ECM stiffness. In summary, immunofluorescence results for 181 primary liver cancer tissue chips (ICC, n=91; HCC, n=90) and analysis of TCGA mRNA-sequencing demonstrate that ECM stiffness can affect phenotypes of primary liver cancers. The YAP1/ABHD11-AS1/STAU2/ZYX/p-YAP1 pathway is a useful entry point for exploration of specific mechanisms of mechanical signal conduction from the ECM in ICC cells and their impact on cancer progression. Moreover, a synergistic anticancer strategy targeting ECM stiffness (ICCM@NPs + siABHD11-AS1@BAPN) is constructed by integrating ECM softening and blocking intracellular mechanical signal transduction in ICC and can provide insights for the treatment of cancers characterized by stiff ECM.

Microstructure degradation and creep failure study of the dissimilar metal welded joint of heat-resistant steel and Inconel 617 alloy tested at 650 °C and applied stress range of 100–150 MPa

Microstructure degradation and creep failure study of the dissimilar metal welded joint of heat-resistant steel and Inconel 617 alloy tested at 650 °C and applied stress range of 100–150 MPa

Study of phase evolution, mechanical, and tribological behaviour of a novel β-phase strengthened Ti-alloy with Fe and Co alloying via a laser material deposition route

Study of phase evolution, mechanical, and tribological behaviour of a novel β-phase strengthened Ti-alloy with Fe and Co alloying via a laser material deposition route

Effect of surface area on the wear properties of Al-based automotive alloy and the role of Si at eutectic level

The efficiency of an engine material is closely correlated with its surface area. In order to investigate wear properties, effect of surface contact area as well as silicon addition at the eutectic level of Al-Cu-Mg alloy has been studied. This test is performed under room atmosphere and dry sliding conditions using a standard pin-on-disk apparatus. Weight reduction method is adopted to measure the wear rate in microns to get more accurate results. A load varying from of 5 to 50 N and a constant sliding speed of 0.77 ms−1 are maintained throughout the test. The test results show that a lower contact surface area has a negative impact on the wear properties having higher wear rate, while the coefficient of friction of the alloy and Si addition into the alloy improve the properties to some extent. Reduction of the contact surface area increases the unit pressure and decreased material volume causes softening of the alloy matrix, resulting in a higher wear rate and coefficient of friction. The Si addition offers such an improvement mostly for an increase in strength via the Si-rich intermetallic formation. A microstructural study confirms a lower abrasive wear with a minor plastic deformation on the worn surfaces of Si added alloy and wear with higher contact surface. The Si-added alloys contain the fine and strong Si-rich intermetallic, which are responsible for such a smooth worn surface.

Evolutions on Microstructure and Impact Toughness of G115 Steel after Long-Term Aging at 700 °C

The microstructure and impact toughness evolution of G115 steel after long-term (ranging from 500 h to 10,000 h) aging at 700 °C were investigated in this study. The results showed that the microstructure of the G115 steel evolved from a finer-grained matrix with minor precipitates to a coarse-grained matrix with more precipitate with aging time, presenting a decrease in the local deformation degree in the matrix. The impact toughness of the steel decreased with aging time, presenting the largest decline at the initial aging times. The decrease in impact toughness was attributed to the coarsening of precipitates (M23C6 and Laves phase) in the steel matrix. The stable impact toughness during the whole aging process (from 500 h to 10,000 h) should be related to the comprehensive effects, including the precipitation of the Laves phase, the increase in high-angle grain boundaries, and the softening of the metal matrix.

Self-Lubrication Mechanism of Surface-Textured Polymer-Matrix Composites under the Induction of Frictional Stress.

Polymer-matrix composites have been widely used in the manufacture of seals, bearings, electrical insulators, and self-lubricating films as engineering applications move toward lighter weight, higher strength, and corrosion resistance. However, the high-speed shear effect of the friction pairs in relative motion leads to localized heating of the polymer surface, resulting in deformation or softening of the device. Herein, acer mono maple and canna leaves were used as templates to construct polymer-matrix sulfonated polyether-etherketone/polytetrafluoro-wax (SPEEK/PFW) composites with a surface-textured structure. As the bionic texture reduces the level of direct contact between the friction pairs, the frictional thermosoftening of SPEEK occurs in the localized areas of the bumps and leads to the release of PFW stored in textures, resulting in the formation of a soft polymer sliding layer in the worn area and greatly enhancing the frictional stability. By investigation of the tribological properties of textured SPEEK/PFW composites under different loads and sliding speeds, the mechanisms from surface wear to matrix softening and spontaneous construction of a slipping layer are summarized. The results of scanning electron microscopy and three-dimensional profilometer characterization of the wear scars show the surface state of SPEEK/PFW after friction, revealing the friction-thermotropic deformation of the surface texture. The results of this study not only improve our understanding of the frictional heat-induced surface self-lubrication mechanism of textured polymer composites but also provide a reference for the development of multiphase hybrid polymer-matrix composites with excellent self-lubrication properties.

Abstract We022: Depletion of Tip60 After Myocardial Infarction Induces Histone H2A.Z Deacetylation Followed by Cardiomyocyte Dedifferentiation/Cell-Cycle Activation

Myocardial infarction (MI) leads to cardiomyocyte (CM) loss, resulting in cardiac dysfunction and heart failure. Remuscularization of injured myocardium requires proliferation of surviving CMs. However, approaches aimed at inducing CM regeneration following MI have been inadequate. To this end, we are targeting the acetyltransferase Tip60 (Tat-interactive protein 60 kD), a pleiotropic tumor suppressor encoded by the Kat5 gene. Using a murine genetic model, we previously reported that disruption of Kat5 promotes CM cell-cycle re-entry, and protects against the damaging effects of MI. It is becoming increasingly recognized that pre-existing CMs must undergo dedifferentiation accompanied by reversion to glycolytic metabolism in order to resume proliferation. The site-specific acetylation of the histone variant H2A.Z at lysine K4/K7 (H2A.Zac K4/K7 ) has been shown to maintain the differentiated state in hematopoietic stem cells (HSCs), neurons, and skeletal myocytes. Here, we report that Tip60 depletion post-MI results in the near-complete absence of H2A.Zac K4/K7 in CMs. This is associated with the enrichment of differentially expressed genes (DEGs) in epithelial to mesenchymal transitioning (EMT), cytoskeletal disassembly, extracellular matrix (ECM) softening, and metabolic reprogramming. To assess therapeutic relevance, we have begun to evaluate the potential cardioprotective effects of the anti-parasitic drug pentamidine, a known Tip60 inhibitor. Systemic administration of pentamidine on days 3-16 post-MI preserved cardiac function, accompanied by CM cell-cycle activation. These data suggest that pentamidine treatment enhances remuscularization, thereby promoting the retention of post-MI function, supporting the translational promise of targeting Tip60 as an innovative therapy for ischemic heart disease.

Creep rupture properties of dissimilar welded joint of ferritic/martensitic P92 steel and Inconel 617 alloy

Creep rupture properties of dissimilar welded joint of ferritic/martensitic P92 steel and Inconel 617 alloy

Microstructure and mechanical properties of in-situ SiO2-reinforced mechanically alloyed CoCrFeNiMnX (X= 5, 20, 35 at.%) high-entropy alloys

The CoCrFeNiMnX (X = 5, 20, and 35 at.%) alloys, reinforced with 5 at.% SiC powder, were prepared by mechanical alloying and spark plasma sintering. This preparation method resulted in microstructural refinement of the FCC solid solution grains, while the SiC addition reacted with residual oxygen to form homogeneously distributed ultrafine SiO2 particles. Additionally, the alloys contained Cr7C3 carbides, which were significantly larger than the SiO2 particles and enriched with the alloy's elements, including Mn. Among the tested materials, the reinforced CoCrFeNiMn20 alloy exhibited the highest hardness and compressive yield strength (CYS), achieving 392 ± 9 HV30 or 476 ± 3 HVIT1 and 1024 ± 18 MPa, respectively. This alloy also maintained superior CYS (956 ± 35 MPa) even after 100 h of annealing at 800 °C. The reduction in CYS after annealing was smallest for the CoCrFeNiMn5 alloy (35 MPa) and increased with higher Mn content, highlighting Mn's significant role in diffusion-related processes. At elevated temperatures (600 and 800 °C), the CoCrFeNiMn5 alloy had the highest CYS of 190 ± 33 MPa, while the CoCrFeNiMn35 alloy had the lowest at 80 ± 6 MPa. This trend was also observed in wear rate tests, where the CoCrFeNiMn5 alloy had the lowest specific wear rate coefficient of 3.54 ± 0.09 × 10-4 mm³ N⁻1 m⁻1. This was due to matrix softening and oxide lubrication without significant spalling. Thus, the CoCrFeNiMn5 alloy demonstrated superior mechanical properties and wear resistance under various conditions, making it a promising candidate for applications requiring high strength and durability.

3D matrix stiffness modulation unveils cardiac fibroblast phenotypic switching

This study investigates how dynamic fluctuations in matrix stiffness affect the behavior of cardiac fibroblasts (CFs) within a three-dimensional (3D) hydrogel environment. Using hybrid hydrogels with tunable stiffness, we created an in vitro model to mimic the varying stiffness of the cardiac microenvironment. By manipulating hydrogel stiffness, we examined CF responses, particularly the expression of α-smooth muscle actin (α-SMA), a marker of myofibroblast differentiation. Our findings reveal that increased matrix stiffness promotes the differentiation of CFs into myofibroblasts, while matrix softening reverses this process. Additionally, we identified the role of focal adhesions and integrin β1 in mediating stiffness-induced phenotypic switching. This study provides significant insights into the mechanobiology of cardiac fibrosis and suggests that modulating matrix stiffness could be a potential therapeutic strategy for treating cardiovascular diseases.

Investigation of ultrasonic-assisted drilling temperature of SiCp/Al composites

ABSTRACT Due to their excellent properties and low manufacturing costs, SiC particle-reinforced Al matrix composites (SiCp/Al) find extensive application in automobile manufacturing and aerospace. However, SiCp/Al is less machinable. The ultrasonic-assisted drilling (UAD) decreases tool wear and enhances the quality of drilled holes when compared to conventional machining techniques. This paper investigates the effect of drilling temperature variations induced by processing conditions on the degree of softening of the base material during UAD of SiCp/Al. It also analyses the mechanism of how drilling temperature affects the quality of the holes made from the perspective of matrix softening. The study demonstrates a regularity in the impact of spindle speed, ultrasonic supply voltage(ultrasonic vibration amplitude), and feed rate as a function of drilling temperature. The effects of temperature changes caused by each of these factors on import/export edge defects, surface scratches on the hole wall, and tool machinability vary.

Coupling effect of temperature and off-axis angle on the compressive properties of needled carbon/quartz fiber-reinforced phenolic resin composite

Coupling effect of temperature and off-axis angle on the compressive properties of needled carbon/quartz fiber-reinforced phenolic resin composite

Early matrix softening contributes to vascular smooth muscle cell phenotype switching and aortic dissection through down-regulation of microRNA-143/145

Early matrix softening contributes to vascular smooth muscle cell phenotype switching and aortic dissection through down-regulation of microRNA-143/145

Superplastic deformation behavior of 5 vol% (TiBw+TiCp)/Ti matrix composite sheets with lamellar microstructure

Superplastic deformation behavior of 5 vol% (TiBw+TiCp)/Ti matrix composite sheets with lamellar microstructure

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds (DMWs) involving nickel-based weld metal (WM) and ferritic heat resistant steel base metal (BM) in power plants, there must be an interface between WM and BM, and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure. In this study, a new form of WM/BM interface form, namely double Y-type interface was designed for the DMWs. Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests, and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization. By applying double Y-type interface instead of conventional I-type interface, failure location of DMW could be shifted from the WM/ferritic heat-affected zone (HAZ) interface into the ferritic HAZ or even the ferritic BM, and the failure mode change improved the creep life of DMW. The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation, stress and strain concentrations, and oxide notch on the WM/HAZ interface. The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ, which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries. The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface, preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking. It is a novel scheme to prolong creep life and enhance reliability of DMW, by means of optimizing the interface form, decoupling the damage factors from WM/HAZ interface, and then changing the failure mechanism and shifting the failure location.

Unexpected softening of a fibrous matrix by contracting inclusions

Unexpected softening of a fibrous matrix by contracting inclusions

Thermomechanical Behavior and Microstructure Properties of Carbon Fiber Reinforced Polymer at Elevated Temperatures

Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 <sup>o</sup>C. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 <sup>o</sup>C, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 <sup>o</sup>C, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 <sup>o</sup>C. The maximum tensile strength of the CFRP plates exposed at 350 <sup>o</sup>C significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.