Plasticity Modulus Research Articles

Nanoscale phase separation achieved through trace PVDF/PEI blending enhances mechanical and energy storage performance at high temperatures

Due to the development of advanced electronic systems, there is an urgent need for polymer dielectric film capacitors with high breakdown strength (Eb) and high discharge energy density (Ud) at elevated temperatures. Herein, an all-organic blend polymer composite is fabricated by blending polyetherimide (PEI) and a trace amount of Poly(vinylidene fluoride) (PVDF), achieving nanoscale phase separation and forming interfaces between PEI and PVDF grain. The real permittivity (εr) and Eb of blend composites are simultaneously enhanced after PVDF introduction. It is worth noting that increasing the temperature does not reduce the Eb of the PEI/xPVDF blend composite. Our Study shows that optimizing the plasticity and storage modulus of PEI/xPVDF significantly contributes to maintaining Eb at elevated temperatures. Additionally, high temperatures enhance the entanglement of molecular chains at the PVDF-PEI interface, further supporting the preservation of Eb. Finally, a high Eb of 540 MV/m, a high Ud of 5.92 J/cm3 are achieved for the PEI/0.5PVDF blend at 150 °C. This work presents a new approach to enhance the Eb of dielectric polymers by optimizing mechanical properties at high temperature, which providing a different strategy for enhancing the energy storage performance.

The noteworthy tensile plasticity and strength of CoFeSiB metallic glass fiber reinforced epoxy composites

AbstractMetallic glass fibers have high strength, poor plasticity and low Young's modulus. In this study, it was used as a reinforcement to prepare metallic glass fiber reinforced epoxy composites with different fiber volume contents (20%, 30%, 40%, and 50%). The effect of fiber volume contents on the tensile properties of the metallic glass fiber reinforced epoxy composites was studied by experiment and the finite element analysis method. The experiment and simulation results are in good agreement. The tensile strength and plasticity of the metallic glass fiber reinforced epoxy composites increase with the increase of fiber volume contents. When the fiber volume content is 40% or 50%, a sharply necking feature appeared on the fibers and exhibited improved plasticity, due to the formation of interacting and arresting events of shear bands occurring at the interface between the metallic glass fibers and the epoxy. In addition, the strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites. This is a first step toward toughening the inherently brittle metallic glass fibers under tensile conditions.Highlights A novel CoFeSiB metallic glass fiber reinforced epoxy resin composite The increase of fiber volume fraction improves the tensile strength and plasticity of fiber reinforced composites. The strain hardening due to plastic deformation of the metallic glass fibers further enhanced the tensile strength of the metallic glass fiber reinforced epoxy composites.

Enhanced yield stress and reduced elastic modulus of metastable β Ti–Nb alloys deformed by equal channel angular pressing attributed to the Synergistic effect of deformation mechanisms

This work aims to obtain Ti–Nb alloys with a high yield stress, good plasticity, and low elastic modulus. To this end, metastable β Ti–Nb alloys were subjected to multipass equal channel angular pressing (ECAP) deformation at room temperature, and a thorough investigation of their microstructure evolution, deformation mechanisms, and strengthening/toughening mechanisms was conducted through X-ray diffraction, transmission electron microscopy, electron backscatter diffraction, and tensile tests. In the initial deformation stages, multiple deformation mechanisms are observed, including dislocation slip, {332} <113> twinning, stress-induced martensite (SIM) α″-phase, {112} <111> twinning, and stress-induced ω-phase. However, as the strain accumulates, the ω-phase disappears, the volume fraction of the SIM α″-phase gradually decreases, and the dominant deformation mechanism changes to dislocation slip and {332} <113> twinning. The ECAP deformation results in a complex-network microstructure and the precipitation of the nanoscale SIM α″-phase, which leads to the twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) effects. As a consequence, the Ti–Nb alloy simultaneously exhibits a high yield stress and a good plasticity. Furthermore, the high-density dislocations and interfaces generated by the ECAP deformation reduce the stability of the β-phase, and the introduced nanopores cause a decrease in density, resulting in a decrease in the elastic modulus of the alloy.

Deformation and Plasticity of Reinforced Concrete

Statement of the problem.Development of the model of plasticity of reinforced concrete structures is based on the intensity of the "stress-strain" relation to project tensors using transitions, as well as the coefficients of the steps of forces and axes (principal angle and strain-strain, total shear strain, etc.). Results. The dependences of plasticity modulus of concrete, transverse coefficient have been obtained. Complex functions of generalized hypotheses of deplanation of linear and angular deformations and jumps for crack formation breakaway and stiffness are constructed. It includes force flows, i.e., blocks of compressed and tensile concrete for isotropic medium (the first object), "main cracks" from fracture mechanics, functional and two-cone element for the deformation effect of reinforced concrete. The resistance of the tensile concrete is transferred to the working reinforcement using the total average longitudinal and transverse forces for the transversal-isotropic environment, including the average modulus of reinforcement and the reduced tensile concrete coefficient of the second limit state group. The special dowel effect is derived from the second level model of structural mechanics for a rebar with two pinched ends, as well as crack opening (a development of the Thomas –– author hypothesis), crack-track bank shear, and buckling. The main vector of forces in the reinforcement is characterized by two values of longitudinal and transverse displacements and the width of opening and shear of the crack-track (the third object). Conclusions. The energetic theory on the surface of the sphere and the determination of the integral of the mean square value of the tangential stresses of plasticity theory allowed to develop an alternative to the ge-neral model in the form of a paraboloid by summing the volume sectors, radius-levels from the matrix of sliding planes (including octahedral and pure shear) in concrete medium from microcracks to macrocracks.

Investigation on the physicochemical properties of Nru clay deposit and its industrial application

The utility of Nru clay for industrial application, which was taken from the Nsukka local government area in Enugu State, Nigeria, is assessed in this study for its physical and chemical properties. The clay was investigated chemically which showed SiO 2 51.2%, Al 2 O 3 18.3% as the predominant constituents while other metallic oxides such as Fe 2 O 3 5.3%, MgO 2.2%, Na 2 O 1.8%, CaO 1.4%, K 2 O 1.3% and MnO 0.7% were present in considerable proportion. The physical and mechanical analysis acknowledged a range in the linear shrinkage (4.17 - 6.25%), total shrinkage (7.8 - 10.2%), apparent porosity (36.92 – 26.58%), apparent density (2.59 - 2.37 g/cm3), bulk density (1.63 - 1.74 g/cm3), water absorption (22.64 – 15.33%) and modulus of rupture (6.70 – 9.15 kg/cm2) with an increase in firing temperature from 900°C to 1200°C. Nru clay can withstand heat without melting or deforming at temperature up to 1200 °C and exhibited reasonable plasticity with a modulus of plasticity of 1.42. We can infer from our investigation that Nru clay is a potential raw material for industries in the production of ceramics, high melting clays, fired bricks, and paints. Alternatively, the clays’ properties can be tailored to achieve superior physical and mechanical properties by enhancing them with additives. Therefore, it can be employed to cushion the exorbitant cost of importing clay minerals from other nations.

МОДЕЛЬ ПЛАСТИЧНОСТИ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ

A model of plasticity of reinforced concrete structures is considered, based on on the transformations of the intensity of the “stress-strain” connection by projecting the tensors of this connection, using special transitions for the main angle of deformations, total shear deformations, etc.). At the same time, the modulus of plasticity of concrete, the coefficient of transverse deformations are determined, and complex functions are constructed for linear and angular deformations in sections, taking into account deformation, gradients of deformations during the formation of cracks and stiffness changes. The hypotheses adopted for the calculation model determine the distribution of force flows - blocks for compressed and stretched concrete (first object), "main cracks" from the mechanics of destruction of reinforced concrete, complex functions and a two-cantilever element for modeling the deformation effect of reinforced concrete, developed by the author (second object). Tensile concrete resistance is transferred to the working reinforcement and is modeled using the sum of the average values of the longitudinal and transverse forces, as well as the average reduced coefficient of tension concrete. The "pin (nagel)" effect in the reinforcement crossed by a crack was obtained using the model of the second level of structural mechanics for a reinforcing bar with two pinched ends. The opening of the crack and the shift of the crack edges are simulated. The main force vector in the reinforcement is characterized by the values of longitudinal and transverse displacements (the third object).

The size-dependence of compressive mechanical properties and serrated-flow behavior of Ti-based bulk metallic glass

In this work, the size-dependence on the compressive mechanical and serrated-flow behaviors of Ti-based bulk metallic glass (BMG) was systematically investigated. The results demonstrated that the compressive plasticity of the BMGs was greatly improved from 1.0 ± 0.6% to 2.4 ± 0.5% with the specimen diameter reducing from 4 to 2 mm, while the fracture strength decreased from 2070 ± 40 to 1870 ± 31 MPa, indicating a trend of smaller and softer characteristics. Meanwhile, the Weibull distribution analysis of the strength and plasticity indicated that when the specimen diameter was increased from 2 to 4 mm, the Weibull strength modulus (mσ) decreased from 83.5 to 46.6 and the Weibull plasticity modulus (mε) decreased from 0.70 to 0.36, revealing a more discrete distribution of both the strength and the plasticity with the increase in diameter. The average shear-band velocity (ASBV), which was calculated based on the stick–slip dynamics, indicated an increasing trend with the increase in specimen diameter, while the shear-band instability index (SBI) presented a similar increasing trend. Meanwhile, the serrated-flow analysis revealed that the BMG specimen with smaller size possessed a lower average stress drop and a larger Weibull modulus of stress drop, which is the substantial cause for the considerable malleability in smaller specimen. Moreover, the fitting result for the cumulative probability distributions of the stress drop indicated that the stress drops in smaller specimens exhibit better coincidence.

Modeling the material of the cylindrical work with welded seam at compression distribution of vehicle parts

It is shown that the distribution of the ends of tubular billets, which are the main connecting elements of the vehicle brake system, is accompanied by a loss of stability in the circumferential and axial directions, as well as localization of deformations, followed by destruction in the form of a longitudinal crack that occurs at the end of the preform. The presence of the weld complicates the general conditions of deformation during crimping and distribution and leads to the destruction of the workpiece along the weld. To prevent cracking, it is necessary to tighten the crimping and distributing factors, which inevitably leads to an increase in the number of transitions, the complexity of the process and the cost of manufacturing the part as a whole. The issue of deformation of welded structures is of interest with the development of new materials for the automotive industry, such as joining two or more steel sheets with different mechanical properties, thickness or type of coating, which are important for reducing weight, minimizing costs and reducing scrap. It is shown that the deformation of the pipe billet will depend not only on the plasticity characteristics of the base metal and the weld metal, which is obvious, but also on the ratio of the squares of the pipe billet. The increase in the above modulus of plasticity is accompanied by hardening of the welded joint compared with the initial metal of the workpiece, respectively, a decrease in the value of the secant modulus in both directions – a decrease in the strength characteristics of the weld metal. Further analysis of the deformation of the welded workpiece should be carried out taking into account the local anisotropy caused by the welding seam, which will make it possible to determine the conditions of sustained plastic deformation and create an additional effect on the weakened area.

Mathematical Modeling on the Residual Stresses in Coatings Due to Heat Treatments

Coatings are implemented on engineering metals and alloys to augment the surface properties such as hardness as well as resistance to wear and corrosion. Heat treatments of coated metals/alloys are performed to aid in the progress of the bonding of the coatings to the substrate. During the air cooling process, the difference in the compositions of the coating and the substrate materials causes them to cool at different rates, which leads to straining in them. The paper presents the research on the mathematical investigation to evaluate the residual stresses in coatings caused due to heat treatments and subsequent air cooling. The mathematical modelling is executed to formulate the equations to represent the residual stresses retained in the coatings due to the heat treatments and subsequent air cooling. Air cooling undergoes two stages namely the initial quenching phase and the final cooling phase. During the quenching phase, the strain was expressed by considering the elastic, plastic and thermal strain components. Poisson’s ratio, deviatoric stress differential of the modulus of plasticity, coefficient of thermal expansion and change in temperature are used to express the elastic, plastic and thermal strain components. During the final cooling phase, the strain was expressed by considering only the elastic and thermal stain components, as the plastic staining the coating material generally does not occur during the final cooling phase and occurs only during the initial quenching phase. From the strain components, the residual stresses for the coatings in the x, y and z axis were formulated. Thus, the total residual stress is the sum total of stresses caused during the initial quenching phase and the final cooling phase.

Influence of Gradation on Resilient Modulus of High Plasticity Soil‐Gravel Mixture

Because of low resilient modulus, high plasticity soil is often not allowed to fill road subgrades and is discarded as construction and demolition waste (CDW). To make use of the CDW, this study explored the possibility of improving high plasticity soil with gravel and examined the effect of gravel gradation on the resilient modulus of the soil‐gravel mixture. A series of dynamic triaxial tests, tests of voids in coarse aggregate, and X‐ray CT scans were carried out on high plasticity soil‐gravel mixtures of different gravel contents and gravel gradation types. The test results show that there is a critical gravel content, that is, 44.1%. When the gravel content is less than 44.1%, the mixture shows a dense suspended structure and its modulus increases slowly with increasing gravel content. When the gravel content is greater than 44.1%, the mixture exhibits a dense skeleton structure and the modulus increases rapidly as the gravel content rises. Moreover, as the gravel gradation tends to the lower type, coarse aggregates increase in quantity and contact each other to form a dense skeleton; thus, the modulus increases accordingly. As the gravel gradation approaches the upper type, coarse aggregates decrease in quantity and tend to suspend in the soil, so the modulus decreases. With the increase in contact number, the skeleton structure is continuously improved, and thus the modulus is enhanced progressively. The results indicate that the gravel mixing method with a gravel content of 40%–45% can effectively improve high plasticity soil and shows great environmental and economic benefits.

Utilisation of Indigenous Ceramic Raw Materials for the Production of Water Closet

The fact is that Nigeria ceramic raw materials are underutilized as a result of inadequate information on the materials which limits the local production of water closet. The emphasis of this research was on the suitability of the physio-chemical properties of the abundant locally sourced ceramic raw materials from South-west Nigeria. The selected locally sourced raw materials included: kaolin, feldspar, silica and ball clay. The Physical properties carried out on the specimens produced include chemical analysis, shrinkage, porosity, bulk density, modulus of rupture, plasticity and viscosity. The physical property tests were done in accordance with (ASTM C). Standard and the chemical composition were identified by AAS spectrometer. However, the ratio of kaolin, feldspar, quartz and ball clay was varied in five major formulation represented as A, B, C, D and E. The clay, kaolin, quartz and feldspar used in this study were found to belong to alumina-silicate group suitable for the production of standard water closet. The samples’ properties met the required standards; hence, the materials were found suitable for production of water closet of acceptable standards. Composition A specimen gives the most suitable proportions for the production of water closet at 40% of kaolin, 25% of feldspar, 10% of quartz and 25% of ball clay respectively.

Визначення прогинів нерозрізних залізобетонних балок при повторних навантаженнях

Викладена методика визначення прогинів нерозрізних залізобетонних балок при повторних навантаженнях з урахуванням зміни пружнопластичних характеристик бетону та наведені блок-схеми для використання методики на ПЕОМ.

Influence of Polypropylene Fiber on Tensile Property of a Cement-Polymer Based Thin Spray-On Liner

The influence of a polypropylene fiber on the tensile properties of a cement-polymer based thin spray-on liner (TSL) was investigated in this study. Two different contents of fiber were added to the liner, yielding two TSL groups. Tensile tests were performed (in accordance with the ASTM D638 standard) on the two groups of specimens as well as the control group at 1, 7, 14, and 28-day curing. The test result verified the large plasticity and low elastic modulus of the TSL compared with the fiber. SEM examination revealed that fibers lying parallel to the load direction ruptured or were pulled out from the matrix, which was beneficial to the tensile strength, but detrimental to the elongation because of their high stiffness. Other fibers lying perpendicular with the load direction were detrimental to both tensile strength and elongation through aggravating the propagation of the cracks. The tensile strength was improved by fiber incorporation, while the elongation was reduced at all curing. The influence of fibers on tensile toughness was uncertain since tensile toughness depended on strength as well as deformity.

Forecasting the Structure and the Hindered Contraction of Casts by Using the ProCAST System of Engineering Analysis

The paper presents the methods for forecasting the structure and geometrical parameters of casts by using the ProCAST system of engineering analysis. Based on experimental studies and computer simulation, a regularity between the supercooling rate of aluminium alloy on the one hand and the nucleation rates and crystal growth rates on the other has been established. There have also been established dependencies describing the change in the plasticity modulus, the coefficient of thermal linear expansion, Poisson's coefficient within the temperature range of 20 to 1000°C for cores made from α-set mixture. The computer simulation based on the experimental data of the processing of silumin casts made it possible to forecast the alloy structure with the probability level of 95%, and to calculate the accuracy of hindered contraction of the alloy with accuracy equal to ± 1.5%.

Variable moduli of soil strain

The experimental diagrams between stress and strain components for soft soils are non-linear. Nonlinear diagrams qualitatively differ for soils of undisturbed and disturbed structures. It is believed that the manifestations of nonlinear properties of soil are associated with micro-destruction of soil structure under compression and, therefore, with changes in its mechanical characteristics under strain. It follows that the modulus of elasticity, Poisson’s ratio, viscosity and other mechanical parameters are the variables in the process of soil strain. Based on this, from the experimental results given in scientific literature, the changes in the modulus of elasticity and plasticity of soil are determined depending on the values of compression strain. In the process of static and dynamic compression of soil it is almost impossible to determine the boundaries of elastic and plastic strains in soft soil. So, the modulus under soil compression is called the strain modulus. From published results of experiments on dynamic and static compression of soil the most informative ones have been selected. Processing the selected compression diagrams of soft soil, the secant moduli of strain for loess soil and clay have been determined. It is established that the moduli of strain of clay and loess soil under static and dynamic strain vary depending on the rate of strain, the state of the structure and the level of compressive load.

Experimental and theoretical analysis of heat flux at fatigue crack tip under mixed mode loading

The work is devoted to experimental and theoretical study of heat dissipation at the fatigue crack tip during mixed mode loading. The plane samples of stainless steel (AISI 304) were weakened by notch to initiate fatigue crack. There were two types of samples for uniaxial loading and biaxial loading. Infrared thermography and the contact heat flux sensor based on the Seebeck effect were used to measure the dissipated thermal energy. The samples were subject to cyclic loading with constant stress amplitude and different biaxial coefficients. The experimental results confirmed the hypothesis about two stages of heat dissipation at fatigue crack tip under Paris regime. At the first stage, the power of heat flux is proportional to the product of the crack rate by the crack length. The second stage is characterized by a traditional linear relationship between the crack rate and the heat flux. The theoretical approach to calculate dissipation energy at fatigue crack tip was obtained. This technique based on link between the elastic-plastic and elastic strain fields at crack tip using the coupling between Young’s modulus and the secant plasticity modulus.

The influence of nanocrystalline CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy particles addition on microstructure and mechanical properties of SiCp/7075Al composites

The influence of nanocrystalline CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy (HEA) particles addition on the microstructure and mechanical properties of SiCp/7075Al composites was investigated systematically. The CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy was prepared by mechanical alloying, and the (5 vol% HEAp + 40 vol% SiCp)/7075Al (HEA-7075Al) and 45 vol% SiCp/7075Al (SiC-7075Al) composites were subsequently fabricated by squeeze casting. The HEA particles were well retained in the Al matrix and remained nanocrystalline following the squeeze casting and heat treatment process, which indicated that the CoNiFeAl0.4Ti0.6Cr0.5 high-entropy alloy has the advantage of sluggish diffusion behavior and thermal stability. The time for the HEA-7075Al composite reaching the aged-peak period (19.5 h) was slightly longer than that of the SiC-7075Al composite (15 h), indicating that the HEA particles addition has postponed the aging process, which can be ascribed to the decrease of dislocation density in the Al matrix, evaluated from XRD. Additionally, in contrast to the SiC-7075Al composite, the HEA-7075Al composite exhibits higher strength, better plasticity and higher modulus with the average values of 712 MPa, 0.82% and 171 GPa, respectively, which is the results of the good interface between HEA particles and Al matrix, high strength nanocrystalline HEA particles and proper dislocation density present in Al matrix.

The experimental and theoretical study of plastic deformation in the fatigue crack tip based on method of digital image correlation

This work is devoted to the experimental study of strain distribution at crack tip using digital image correlation technique. The real strain fields were compared with an elastic solution for verification of a hypothesis about link of the elastic-plastic and elastic strain fields at crack tip using the coupling between Young’s modulus and the secant plasticity modulus. The precracked plane specimens of titanium alloy VT1-0 with a thick of 1 mm were used in experimental program. The method of digital image correlation based on system StrainMaster was used for measurement the plastic deformation with spatial resolution up to 1 mkm. The strain field was obtained for different crack length and different biaxial coefficient was obtained using biaxial testing machine Biss BI-00-502. Numerical simulation of deformation fields at the fatigue crack tip was done. A qualitative correspondence between the theoretical, calculation and experimental results has been shown.

Effect of crosslinking on the physical and chemical properties of β-lactoglobulin (Blg) microgels

HypothesisMicrogels assembled from the protein β-lactoglobulin are colloidal structures with potential applications in food materials. Modifying the internal crosslinking within these microgels using enzymatic or chemical treatments should affect dissolution, swelling, and viscous attributes under strongly solvating conditions. ExperimentsMicrogels were treated with citric acid, glutaraldehyde and transglutaminase to induce cross-linking or with tris(2-carboxyethyl)phosphine to reduce disulfide linkages. Change in hydrodynamic particle size due to acidic pH, alkaline pH, ionic strength, osmolyte concentration, ethanol, urea, sodium dodecyl sulfate, and reducing agents was evaluated by light scattering measurements. Changes in microgel nanomechanical properties were evaluated via force spectroscopic measurements in water. FindingsAverage microgel size increased ∼20% in alkaline pH and with ethanol contents above 10%, and decreased ∼20% with sucrose contents above 10%. Cross-linking by glutaraldehyde and transglutaminase prevented size increases in alkaline pH. Microgel plasticity and elastic modulus were unaffected by treatments. Microgels treated with glutaraldehyde were found to have much greater stability to urea, sodium dodecyl sulfate, and reducing agents when compared to other samples. Even without cross-linking, microgels remained stable against precipitation and dissolution over a wide range conditions, indicating their broad utility as colloidal stabilizers, texture modifiers or controlled release agents in food or other applications.

Liquid-phase separation in undercooled CoCrCuFeNi high entropy alloy

Liquid-phase separation in a CoCrCuFeNi high entropy alloy is evidenced by supercooling method. The CoCrCuFeNi high entropy alloy is supercooled by glass fluxing method with a sample mass about 100 g which allows tensile test at different undercoolings. The microstructure evolution of CoCrCuFeNi high entropy alloy solidified at different undercoolings are investigated. The variation of interdendritic Cu-rich phase and the hardness of the dendrites are described in detail and liquid-phase separation is confirmed to have taken place when undercooling is equal or greater than 100 K. The plasticity and elastic modulus during tensile tests are strongly affected by compositional change upon liquid-phase separation. The samples solidified after liquid-phase separation exhibit much higher plasticity and lower elastic modulus.