Elastic Deformation Region Research Articles

Hydrogen embrittlement behaviors during SSRT tests in gaseous hydrogen for cold-worked type 316 austenitic stainless steel and iron-based superalloy A286 used in hydrogen refueling station

To consider an appropriate evaluation method for hydrogen compatibility, slow strain rate tensile (SSRT) tests were conducted on high strength piping materials, cold-worked type 316 austenitic stainless steel (SUS316CW) and iron-based superalloy A286, used in hydrogen stations for two years.SUS316CW, used at room temperature in 82 MPa gaseous hydrogen, contained 7.8 mass ppm hydrogen. The SSRT test of SUS316CW was conducted in nitrogen at −40 °C. The fracture surface showed dimples, and no hydrogen embrittlement behavior was observed. While, the SSRT test of SUS316CW in 70 MPa gaseous hydrogen at −40 °C showed a slight decrease in reduction area and a brittle fracture morphology in the outer layer. This was considered to be the effect of high-pressure gaseous hydrogen during the SSRT test in addition to the pre-contained hydrogen.A286, used at −40 °C in 82 MPa gaseous hydrogen, contained negligible hydrogen (0.14 mass ppm). SSRT tests were conducted at 150 °C in 70 MPa gaseous hydrogen and in air, and showed a low relative reduction in area (RRA) value. To investigate the decrease in the RRA, we switched the gas from hydrogen to air in the middle of the SSRT test and closely examined the RRA values and fracture morphology including side cracks. The hydrogen embrittlement was found to originate from the elastic deformation region. Stress cycling in the elastic deformation region also accelerated the effect of hydrogen. These were attributed to an increase in the lattice hydrogen content. While in the plastic deformation region, hydrogen trapped in the defects and hydrogen through the generated surface cracks increased the hydrogen content at the crack tips, reducing the RRA value. And there was a good correlation between the crack lengths and RRA values.Then, hydrogen embrittlement mechanism depends on the operating conditions (stress and temperature) of the material, and evaluating the hydrogen compatibility of materials by controlling their hydrogen content and strain according to the service environment is desirable.

Mathematical modeling and analysis of the tailor rolled blank manufacturing process

A tailor rolled blank (TRB) is a plate of continuously varying thickness with the advantages of lightweight, high strength, and good surface quality. However, it is required that the roll gap can be adjusted online, and the plate and roll produce large elastic deformation in the TRB manufacturing process. These characteristics make the modeling of the force and deformation parameters more difficult. A new mathematical model of roll separating force in the TRB manufacturing process is established taking into account the feature of deformation in this research. The elastic deformation of the strip and the flattening deformation of the roll are considered in order to improve the prediction accuracy of the results. The roll separating forces of the entrance elastic compression region and the exit elastic recovery region are computed using the generalized Hooke's law. A new velocity field is proposed based on the deformation characteristics of the plastic region and velocity boundary conditions, and the power functionals of the internal deformation, shear, friction, and tension are calculated. The analytical models of force and deformation parameters combined the elastic and plastic deformation regions are obtained through iterative operation, which satisfies the convergence condition of the roll separating force and roll flattening. The roll separating force data obtained by the model in this research are compared with the actual measured values in the laboratory, and the deviation value is small, which proves the computational precision of the present model. Additionally, the variations of the entrance velocity and flow volume per second during the TRB manufacturing process are shown, and the influences of the tension and friction factor on the neutral angle and roll separating force are illustrated.

Influence of high temperature during tensile test for stainless steel using acoustic emission

AbstractThis paper explores the application of acoustic emission (AE) monitoring in mechanical and materials studies, specifically focusing on the detection of plastic deformation, fracture, and crack growth. However, the influence of high temperature on AE signals and its effects on mechanical properties are not fully understood due to the limitations of sensors in high‐temperature environments. To address this gap, the study investigates the impact of high temperatures on the mechanical properties of stainless steel SS304 using AE techniques during tensile testing. Two temperature conditions were tested: 600 and 700°C. AE sensors connected to specimens captured AE activity using a designated waveguide, and a Continuous Creep Monitoring Instrument (CCMi) recorded the responses. Sensitivity testing using the pencil‐lead break (PLB) technique ensured the sensor's capability. The proposed frequency‐based analysis method, fast Fourier transform amplitude (FFTA) analysis, was employed to effectively analyze the AE signals. The results revealed significant AE features and frequency distributions associated with elastic deformation, plastic deformation, and fracture regions. These findings establish a foundation for utilizing AE techniques in crack detection and monitoring under high‐temperature loading, contributing to equipment reliability and structural integrity.

Crystallization, structure and properties of PP-b-PE block copolymer

In recent years, a commercialized polypropylene (PP) and polyethylene (PE) block copolymer has been synthesized using chain-shuttling polymerization, but its molecular structure and properties are still limitedly understood. In this work, we analyzed the chain composition, mechanical properties, and structural transformations occurring during the deformation of commercial PP-PE block copolymer obtained via chain-shuttle technology. The chain composition and crystallization properties of PP-PE block copolymers obtained by chain shuttling technique were analyzed using nuclear magnetic resonance (NMR), temperature-rising elution fractionation (TREF), and differential scanning calorimetry (DSC) techniques. The sample has a mass ratio of 49:51 of PE chains to PP chains, but the crystallinity of the two components differs significantly. The PP displays limited crystallinity, indicating short PP chain segments. Some PE sequences are incorporated into the PP matrix as random copolymers, resulting in elastomeric behavior. We investigated the In-situ structural changes of crystals during stretching using synchrotron radiation 2D X-ray diffraction/scattering. In the elastic deformation region, the strain has a significant influence on the orientation of PE crystals but has little effect on the orientation of PP crystals. After the yield point, the strain-induced PE crystal failure resulting in a decrease in stress. In the strain hardening region, the orientation of PE induces recrystallization, forming a layered structure with tensile orientation. At the same time, the PP crystals are disoriented under the action of strain until they break. The results from this work provide significant insight into the design of PP-PE block copolymer products to meet the performance requirements needed for engineering applications.

In situ investigation of the evolution of shear transformation zones with different elastic tensile strains in metallic glass

Shear transformation zones are usually thought as the fundamental unit characterizing microscopic atomic rearrangement motion during deformation in amorphous materials and the corresponding evolution process determines the macroscopic mechanical behaviors. However, the evolution process of shear transformation zones under tensile loading are difficult to be experimentally detected. Here, one in-situ tensile platform coupled with nanoindenter was introduced to conduct a series of nanoscale continuous loading and creep tests on Cu50Zr50 metallic glass film under different pre-tensile strains within the elastic deformation region. The effects of loading rate and pre-tensile strain on the continuous loading and creep behaviors were systematically investigated. Moreover, the corresponding shear transformation zone volume, the activation volume and the relaxation time spectrum during tensile deformation were determined based on the Cooperative Shearing model and Maxwell-Voigt model. It was found that both of the shear transformation zone volume, activation volume and the peak intensity for the relaxation time spectrum increase with pre-tensile strain. Finally, one scheme is proposed to illustrate the microscopic mechanism for the evolution of shear transformation zones during tensile deformation. The current study offers one effective experimental strategy to in-situ investigate the mechanical behaviors and to reveal microscopic deformation mechanism in amorphous materials.

Study of the generalized curves of the static and cyclic deformation, damage and fracture

Individual deformation diagrams of all materials on metal, non-metal, or composite base under static and cyclic load link stresses and strains. These diagrams are obtained in standard tensile, compression, torsion or bending tests of laboratory samples with the registration of forces and deformations of their working parts upon loading. The diagram for a single static deformation in the stress-strain coordinates in this case covers both the region of elastic deformations and the region of elastic-plastic deformation, when deformations are localized in the neck of the loaded sample up to the moment of its destruction at a critical stress level. It is shown that linear, fractional-linear and power approximation of the obtained deformation curve are widely used in the description of the obtained deformation diagrams. Direct experiments, the theory of dislocations and the statistical theory of strength confirm the priority of power approximation of considered diagrams. At the same time for all construction materials the generalized deformation diagram in relative coordinates is described by a single power equation with the individual hardening parameter which is determined experimentally or theoretically using the dependences linking data on the module of elasticity, yield stresses, strength, and ultimate plasticity of the material. Diagrams of a cyclic elastoplastic deformation in the form of loops of plastic hysteresis are recorded by analogy with static tension diagrams with «stress – strain» axes of in conditional and true relative values. The generalized deformation diagrams for a single static and cyclic loading form a scientific basis for construction of the generalized fatigue curve on the basis of deformation fracture criterion for a wide range of cycles to failure. An effective solution to the problems of strength and service life for the most complex engineering objects such as nuclear reactors, aircraft, rocket and space systems can be achieved through introduction of generalized deformation and fracture diagrams into consideration and corresponding calculations. Their significance will especially increase in the design and implementation of new unique science-intensive facilities.

Squeeze Behaviors of Magnetorheological Fluids under Different Compressive Speeds.

The compression tests under the unidirection for magnetorheological (MR) fluids have been studied at different compressive speeds. The results indicated that curves of compressive stress under different compression speeds at the applied magnetic field of 0.15 T overlapped well and were shown to be an exponent of about 1 of the initial gap distance in the elastic deformation region and accorded well with the description of continuous media theory. The difference in compressive stress curves increases significantly with an increasing magnetic field. At this time, the continuous media theory description could not be accounted for the effect of compressive speed on the compression of MR fluid, which seems to deviate from the Deborah number prediction under the lower compressive speeds. An explanation based on the two-phase flow due to aggregations of particle chains resulting in much longer relaxation times at a lower compressive speed was proposed to explain this deviation. The results have guiding significance for the theoretical design and process parameter optimization for the squeeze-assisted MR devices such as MR dampers and MR clutches based on the compressive resistance.

The substantiation of the composition of a soft medicine for the therapy of inflammatory diseases of the musculoskeletal system

Aim. To substantiate the optimal composition of the base of the semisolid dosage form with the thick extract of feverfew (Tanacetum parthebased on structural-mechanical, textural, adhesive and microscopic studies. Materials and methods. The study objects were samples of a semisolid dosage form with the thick extract of feverfew with various gelling agents and the reference drug “Irikar”. In the course of the research, a complex of structural-mechanical methods and the microscopic analysis of the samples were used. Results and discussion. The studies of structural-mechanical properties have determined the regularities in the rheological characteristics of the experimental samples made using different gelling agents. It has been found that the rheogram of the emulgel sample has a smooth transition from the elastic deformation region to the elastic-plastic one, which may indicate a more homogeneous distribution of the sample components. It has been also determined that the sample corresponds in the textural properties to the refenium) rence drug – “Irikar” cream. The structural-mechanical studies have substantiated the rational content of the gelling agent in the emulgel composition – 3 %. The results of rheological studies have been confirmed by the data of the microscopic studies. Conclusions. The data obtained are the basis for further pharmaceutical development of a drug with the thick extract of Tanacetum parthenium for the treatment of diseases of the musculoskeletal system.

Effect of high-pressure hydrogen environment in elastic and plastic deformation regions on slow strain rate tensile tests for iron-based superalloy A286

To investigate the effects of a high-pressure hydrogen environment in the elastic and plastic deformation regions, we performed slow strain-rate tensile tests of iron-based superalloy A286 at 150 °C by switching the atmosphere from 70 MPa hydrogen to air during the tests. The relationship between the nominal strain exposed to a hydrogen environment and the relative reduction in area (RRA) revealed that in the plastic deformation region, the RRA value decreased gradually depending on the nominal strain exposed to hydrogen, but in the elastic deformation region, the RRA value decreased rapidly. The RRA value further decreased when the stress cycle was applid in the elastic region. The fracture surface exhibited an intragranular slip plane fracture similar to that of the hydrogen-charged specimen. These phenomena suggest that the lattice decohesion theory is dominant in the elastic region, where hydrogen embrittlement occurs owing to an increase in the content of dissolved hydrogen.

Effect of Shear Strain on the Supercooled Itraconazole

This article investigated the effect of shear strain on the nematic itraconazole (ITR) from both elastic and plastic deformation regions. The rheo-dielectric technique was used for this purpose. It has been demonstrated that shear strain can change the sample color, liquid crystal alignment as well as its dielectric and thermal properties. The observed modifications depend on the shear strain value. One can distinguish four regions regarding the slope of ITR stress–strain dependence and caused changes. Proper alignment changes (obtained after the shearing procedure) can additionally affect the further recrystallization of ITR to other than the initial, i.e., second polymorphic form.

Solidification Microstructure and Mechanical Properties of B1-type TiC in Fe-Ti-C Ternary Alloys

The microstructure of the B1-type TiC formed during solidification and its mechanical properties were investigated using arc-melted Fe-Ti-C ternary alloys. The TiC formed at relatively high temperatures in the liquid as the primary phase exhibited a dendritic shape. With decreasing temperature and/or decreasing Ti and C content in the liquid, its morphology changed to a cubic shape with the {001}TiC habit plane, a plate shape with the {011}TiC habit plane, and a needle shape with the <001>TiC preferential growth direction. The morphology of the TiC was characterized by the anisotropy of its surface energy and its growth rate. The cubic shape with the {001}TiC habit plane was formed as a result of the minimum surface energy of the {001}TiC. However, the plate shape with the {011}TiC habit plane and the needle shape with the <001>TiC preferential growth direction should be formed due to the slowest growth rate of <011>TiC and the fastest growth rate of <001>TiC, respectively. At room temperature, alloy with the dendritic TiC was fractured in the elastic deformation region because the TiC exhibited no plastic deformation. On the other hand, at 800ºC, it was suggested that the TiC has plastic deformability and alloy with the dendritic TiC was also plastically deformed.

Experimental investigation of surface pressures, velocities, and dynamic structural analysis of tornadic winds on a luminary pole

Several engineering and media reports have demonstrated that luminary and lighting poles are susceptible to tornadic wind actions. This paper provides the first dynamic structural analysis of a 1:50 geometrically scaled model of a generic luminary pole of a circular cross-section tested under transient wind loads caused by translating tornado-like vortices (TLVs). The physical experiments were performed in the WindEEE Dome tornado simulator at Western University (Canada). The tornadic wind actions on the pole are also compared against the reference atmospheric boundary layer (ABL) wind gust with the mean recurrent period of 50 years. Three different positions of the luminary pole in respect to the TLV path were considered: (1) TLV center passing over the pole; (2) TLV core radius passing over the pole; and (3) an intermediate case in which the pole was positioned between the TLV center and the core radius. In all cases two circular cylinders of different diameters were used to simulate two different cross-sections of an actual luminary pole. Our study demonstrates that luminary poles are more susceptible to tornadic wind actions compared to ABL winds. The tip displacements of the pole were larger in the TLVs and the direction and magnitude of the displacements were dependent on the relative positions of the TLVs and the luminary pole. The highest wind forces were observed in the regions characterized by strong tangential wind speeds. The entire luminary pole was subjected to negative pressure coefficients during the TLV passage. However, our structural analysis showed that the pole always stayed in the elastic region of deformation and there was no permanent bending or collapse of the structure.

ОЦІНЮВАННЯ РІВНЯ ТЕРМІЧНИХ НАПРУЖЕНЬ В ОКСИДНИХ ТОНКИХ ПЛІВКАХ

The results of estimation of the nature and magnitude of residual thermal stresses in CuO oxide layer synthesized on a substrate of pure copper using a known analytical model for calculating thermal stresses in single-layer coatings are presented. Thermal stresses can lead to deformations and destruction of thin-film structures and coatings, shortages and reduced quality of parts on which they are applied. The main technological parameters, on which the values of thermal stresses depend, are the operating temperatures of the process of formation of thin-film oxide layers. After the synthesis process, the coated substrates are cooled to ambient temperature. This cooling leads to thermal residual stresses. In the case where the coefficient of thermal expansion of the material of the oxide layer is much less than the coefficient of thermal expansion of the substrate material, in the CuO layer compressive residual stresses generete, while in the Cu substrate – tensile stresses. The stress-strain state during the cooling of the thin film/substrate system, which is free from external forces, was investigated. The mathematical model used the assumption that the resulting deformations do not exceed the elastic limit (the residual stresses lie in the region of elastic deformations), and the temperature gradient in the thickness of the materials does not change. It should also be noted that the values of thermal expansion coefficients, modulus of elasticity and Poisson's ratios are constant values and do not depend on temperature changes. The paper presents the main analytical dependences of thermal stresses on the physical and mechanical properties of the coating materials and the substrate. Based on the results of calculations, a graph of the dependence of thermal stresses of the coating-substrate system depending on the temperature of synthesis of oxide layers was developed. Thermal stresses are one of the components of the total residual stresses operating in the film/coating system. The obtained results on the values of residual stresses can be used to prevent the deformation and failure of thin films and coatings, as well as to predict the characteristics of the surface layers.

Моделирование напряженного состояния в преградах из анизотропных материалов

To study the properties of anisotropic materials, a mathematical model is proposed that accounts for the anisotropy of elastic and plastic properties, as well as the anisotropy of “thermal” and “cold” components of pressure. The model is applied in a threedimensional simulation of the deformation of an HCP-single-crystal barrier under impact loading by an aluminum impactor. The numerical simulation results are obtained using the dynamic finite element method with a difference scheme modified to account for the anisotropy of “cold” and “thermal” pressure components. To simulate the anisotropy of the stress deviator in the region of elastic deformations, generalized Hooke's law is used, while in the region of plastic deformations, the Mises-Hill plasticity function (Hill48) is used with account for the anisotropy of elastic properties and anisotropy of the Gruneisen coefficient. The experimentally and numerically obtained velocity profiles of the back surfaces of single-crystal zinc barriers during the spall fracture are compared with each other. When the impact loading direction coincides with [0001] axis, the elastic precursor is not observed on the velocity profile calculated numerically, which is the same for the one derived experimentally. This effect may be explained only with the use of anisotropic pressur.

Strain Properties of Multicomponent Nanosize Film Materials

The results of the correlation between the longitudinal strain coefficient (SC) and the values of the Poisson coefficient and Grüneisen parameter for nanosize film multicomponent alloys (d ≅ 30–50 nm, ci ≅ 11–20 at%) are presented. It is established that in the region of elastic or quasi‐elastic deformation (less than or equal to 0.4%), the value of SC is insensitive to changes in the Grüneisen parameter in the range of 1.5–2.5 units during the transition to plastic formation (more than 0.4%). The value of SC decreases from 4–5 units to 3–1 units. Similarly, SC is insensitive to changes in the Poisson coefficient less than or equal 0.4 but decreases sharply in the region of plastic deformation. It is concluded that a sensitive element based on a multicomponent nanoscale film of a solid solution, including a high‐entropy one, has advantages over others due to phase stability in a wide temperature range. These materials may be used to develop the architecture of sensitive elements of sensors for various functional purposes.

Sudden change of spall strength induced by shock defects based on atomistic simulation of single crystal aluminum

This Letter interprets the detailed mechanism about the discontinuous variation in spall strength associated with shock-induced microstructure. It is known that elastic deformation, dislocation and stacking fault, as well as shock structural transition will appear in turn with the increase of shock intensity. Our molecular dynamics simulations of single-crystal aluminum reveal that the spall damage shows an evident dependence on the shock-induced microstructure. The nanovoids nucleate homogeneously in the region of elastic deformation or phase transition, resulting in higher spall strength. However, the nanovoids nucleate heterogeneously in the region of dislocation and stacking faults, which leads to a sudden decrease in spall strength. Different nucleation modes have a significant effect on the temperature response of spall strength. Under the condition of heterogeneous nucleation, the spall strength shows different temperature dependence and does not change inversely with temperature.

Characterization of dynamic hardening behavior at intermediate strain rates using the virtual fields method

Crash analysis simulation is now very important in automotive industry to assess automotive crashworthiness and safety. In order to acquire reliable crash simulation results, precise material behaviors at intermediate strain rates should be used as input data. To derive the stress-strain curves at various strain rates, a large number of experiments are needed, which is costly and time consuming. The present study aims at determining the stress-strain curves of sheet metals at various strain rates from a single dynamic experiment. A new type of high-speed tensile tester for sheet metal specimens was built and high-speed tensile tests were carried out. Full-field heterogeneous strain fields were measured by a digital image correlation technique using a high-speed camera. The load data was acquired from strain gauges attached to the elastic deformation region on the specimen. Then, an inverse identification scheme with a rate dependent hardening law was applied to retrieve dynamic parameters. The stress-strain curves of three advanced high strength steels at intermediate strain rates (100 s−1 – 300 s−1) were successfully obtained from a single experiment.

Shape Analysis of the Elastic Deformation Region throughout the Axi-Symmetric Wire Drawing Process of ETP Grade Copper.

The wire drawing process is commonly perceived as one of the best studied metal forming processes in almost every aspect; however, when considering elastic deformation, researchers usually focus on the uniaxial tensile forces after the material exits the drawing die and not the elastic deformation region before entering the drawing die, even though it may have a significant impact on the strength parameters and the nature of metal flow inside the drawing die. The aim of this research is to theoretically and experimentally identify the deformation in the elastic region and to further link the shape of this region and the values of stress occurring in it with the geometrical parameters of the drawing process and assess its impact on its strength parameters. In order to achieve the assumed goals, numerical analyses using the finite element method and experimental research on the drawing process in laboratory conditions were carried out using Vickers hardness tests and resistance strain gauges measuring deformation in stationary and non-stationary conditions. The obtained results indicate that the shape and the extent of the region of elastic deformations generated in the material before the plastic deformation region during the drawing process depends on the applied deformation coefficient and stationarity of the process.

Advances in strain engineering on oxide heteroepitaxy

Advances in strain engineering on oxide heteroepitaxy

Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region.

A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. The following results have been obtained: (1) the Young’s modulus of a grain without consideration of grain-to-grain interaction is denoted as the inherent Young’s modulus; when the inherent Young’s modulus of a grain is equal to the Young’s modulus of the bulk material, there is almost no interaction between the grain and its adjacent grains; when a grain has a great difference between its inherent Young’s modulus and the Young’s modulus of the bulk material, its grain-to-grain interactions increase significantly; (2) the grain-to-grain interaction is mainly caused by the difference in the inherent Young’s modulus between the grain and its adjacent grains; the misorientation angle between the grain and its adjacent grains has almost no effect on the grain-to-grain interaction.