Occurrence Of Plastic Deformation Research Articles

Investigating the wear resistance of high-chromium cast irons A532-class III-type A against high-energy abrasive particles

Regarding the widespread use of high chromium cast irons in manufacturing various industrial and mineral-processing parts such as liners, slurry pumps, and grinding balls, increasing erosion resistance is the key factor to enhance their performance. This research investigated three different chemical compositions of high chromium irons (in the eutectic and hypoeutectic range). Austenite destabilization process was conducted at two temperatures of 1060°C and 970°C followed by air cooling and then tempering at the range of 250°C to 400°C for 4 h. Erosion and bending tests were carried out on samples with optimal heat treatment conditions. Results show that the hardness of specimens heat-treated at 970°C, and also the low-carbon hypoeutectic specimens destabilized at 1060°C, increased by increasing tempering temperature over 300°C, which can be related to the formation of a higher volume fraction of M23C6 carbides. The best erosion resistance was observed in the low-carbon hypoeutectic specimen destabilized at 1060°C and tempered at 300°C. In addition, samples with higher erosion resistance exhibit lower bending strength. Finally, it was found that the principal wear mechanism was the occurrence of plastic deformation, and detachment of carbides from the surface before having an effective role in reducing wear.

Nanomechanical, mechanical and microstructural characterization of electron beam welded Al2219-T6 tempered aerospace grade alloy: A comprehensive study

As compared to traditional fusion welding processes, electron beam welding (EBW) is known to produce structurally robust microstructures and narrow heat-affected zone (HAZ) in metals. The process becomes more significant for the tempered alloys vulnerable to heat exposure. In the present investigation, Al 2219-T6 alloy was joined using the EBW process. The microstructural, mechanical, and nanomechanical characteristics of the resulting joint were investigated. EBW resulted in a narrow HAZ (22 μm) with a 430 mm fusion zone (FZ). A dendritic structure was observed in the FZ zone, while second-phase particles were absent indicating their dissolution during welding and interesting formation of Al2Cu mixture around the dendrites. The limited content of Cu in the base metal (BM) resulted in the formation of a solid solution in the FZ, along with the presence of fine equiaxed grains in the HAZ and equiaxed dendritic grains in the FZ zone. The X-ray diffraction analysis confirmed the absence of peaks corresponding to incoherent phases in the FZ. Compared to the BM, micro-hardness measurements revealed a 12.7 % increase in the hardness in the HAZ, while a significant decrease of approximately 19 % was observed in the FZ. The joint exhibited reduced tensile strength, ultimate strength by 42.2 %, and yield strength by 47.3 % when compared to the BM. The fracture analysis indicated a ductile failure mode with the presence of microvoids. Nano-indentation tests at various loads demonstrated a decrease in the nanohardness from the BM to the HAZ and FZ regions. Atomic force microscopy (AFM) analysis revealed significant pile-ups in the FZ, indicating the occurrence of plastic deformation during the welding process. The presented findings are valuable for the joint and structure design of Al −2219T6 alloy in particular and other Al alloys in general.

Anisotropic Deformation Behavior and Indentation Size Effect of Monocrystalline BaF2 Using Nanoindentation.

In this study, our objective is to investigate the anisotropic deformation behavior and the indentation size effect (ISE) of monocrystalline barium fluoride (BaF2) using nanoindentation experiments with a diamond Berkovich indenter. BaF2 is known for its anisotropy, which results in significant variations in its mechanical properties. This anisotropy poses challenges in achieving high processing quality in ultra-precision machining. Through our experiments, we observed numerous pop-in events in the load-displacement curves, indicating the occurrence of plastic deformation in BaF2 crystals, specifically in the (100), (110), and (111) orientations; these pop-in events were observed as the indentation depth increased to 56.9 nm, 58.2 nm, and 57.8 nm, respectively. The hardness-displacement and elastic modulus-displacement curves were obtained from the tests exhibiting the ISE. The nanoindentation hardness of BaF2 is found to be highly dependent on its crystallographic orientation. Similarly, for BaF2 in the (100) orientation, the range is from 2.43 ± 0.74 and 1.24 ± 0.12 GPa. For BaF2 in the (110) orientation, the values range from 2.15 ± 0.66 to 1.18 ± 0.15 GPa. For BaF2 in the (111) orientation, the values range from 2.12 ± 0.53 GPa to 1.19 ± 0.12 GPa. These results highlight the significant influence of crystallographic orientation on the mechanical properties of BaF2. To better understand the ISE, we employed several models including Meyer's law, the Nix-Gao model, the proportional specimen resistance (PSR) model, and the modified PSR (mPSR) model, and compared them with our experimental results. Among these models, the mPSR model demonstrated the best level of correlation (R2>0.9999) with the experimental measurements, providing a reliable description of the ISE observed in BaF2. Our reports provide valuable insights into the anisotropic mechanical characteristics of BaF2 materials and serve as a theoretical guide for the ultra-precision machining of BaF2.

Fenomena Las Gesek (Friction Welding) Dengan Variasi Waktu Gesek Pada Material AISI 1040 Dengan Kuningan

Friction welding is one of the metal joining methods, by utilizing the heat generated from the physical contact of two metals in the form of friction that occurs continuously on the two metals to produce a welding joint. This research aims to find out what phenomena occur in the connection between AISI 1040 and Brass. The materials used are AISI 1040 solid cylinder with a diameter of 16 mm and brass solid cylinder with a diameter of 16 mm. This research uses experimental method. The friction time used is 6 minutes, 7 minutes, and 8 minutes with a variation of pressing distance of 3 mm, 4 mm, 5 mm with a rotating speed of 1000 rpm. The free heat process of 200 ℃ was carried out on AISI 1040 before the welding process. From the time variation and pressing distance variation that has been carried out in this study, the results obtained from the two materials do not occur. There are several phenomena seen after the welding process such as the occurrence of plastic deformation in brass and the formation of a brass thermoplastic layer attached to the surface of AISI 1040, in the time variation of 6 minutes and 7 minutes the brass thermoplastic attached to AISI 1040 is small and thin, while in the time variation of 8 minutes the brass thermoplastic layer attached to AISI is quite a lot and thick but no connection has occurred. This friction welding method is likely to connect the AISI 1040 material with brass by increasing the friction time performed.

Evolution of particle morphology of quartz sand during one-dimensional compression

Particle breakage alters particle size, shape, surface roughness, and co-ordination number, which in turn changes macro-mechanical behaviour including compressibility and shear strength. This study conducted a series of one-dimensional (1D) compression tests on quartz sands with different initial void ratios, ending the tests at various stress levels up to 13.5 MPa. The size and shape of particles were quantified using a dynamic particle shape analyser, while the surface roughness of thirty randomly selected particles for each sample was measured by an optical interferometer and quantified using flattened root-mean-square roughness (RMSf). The results demonstrate that a unique normal compression line is defined due to extensive particle breakage, with denser sample exhibiting a higher yield stress. Prior to yielding (vertical stress < 6 MPa), the changes in the three shape descriptors are limited, as the primary particle damage modes are abrasion and grinding. Conversely, at high stress level, a greater number of particles undergo splitting or explosive damage, leading to the creation of more irregularly shaped particles. The occurrence of plastic deformation at particle asperities under one-dimensional compression is identified, resulting in a decrease in surface roughness. This study highlights the significant role of the initial void ratio in shaping the evolution of surface roughness of particles under 1D compression.

Comparative analysis of experimental and numerical investigation on multiple projectile impact of AA5083 friction stir welded targets.

This research aims to investigate the ballistic resistance of base material (BM)and "Friction Stir Welded (FSW)", AA5083 aluminum alloy. The primary objective was to build a finite element model to predict kinetic energy absorption and target deformation under single and multiple projectile impact conditions. This study employed 7.62mm Hard Steel Core (HSC) projectiles produced from Steel 4340. The target was analyzed using commercially available Abaqus Explicit software for Finite Element Analysis. It was noticed that the generation of kinetic energy and surface residual velocity increases as the number of projectile strikes increases. In addition, the experimental ballistic test was conducted to validate the numerical results. Using the analytical Recht-Ipson model, each target's experimental residual velocity was determined. It was determined that weldments perform less well (30%) as compared to BM targets. Occurrence of plastic deformation during welding causes reduction in ballistic performance of weldments. For both the computational and experimental approaches, a correlation between residual velocities was found. The plastic deformations with ductile hole formation were observed in all the cases.

High-temperature compression behavior of bimodal α-Mo structured Mo-Si-B alloy

Previous study indicated developing a bimodal (micron/submicron) structured α-Mo matrix could improve fracture toughness of the fine-grained Mo-12Si-8.5B-0.57 wt% La2O3 alloy greatly without sacrificing strength dramatically at room temperature. In this work, the effect of bimodal α-Mo structure on the compressive behavior of this alloy at 1000–1400 °C was investigated. At 1000 °C, because micron α-Mo regions weakened grain boundary strengthening effect, the compressive strength and yield strength of bimodal alloy were lower than those of fine-grained alloy. But at 1200 °C and 1400 °C, the compressive strength and yield strength of bimodal alloy were higher since the micron α-Mo regions exhibited less grain boundary sliding deformation. Especially at 1400 °C, the obvious work hardening induced by the large plastic deformation of micron α-Mo regions was an extra contribution to the strength. Additionally, the intragranular and intergranular nano-scale La2O3 particles could strengthen alloy by inhibiting dislocation slip and pinning grain boundaries. Moreover, this bimodal alloy exhibited good dynamic softening resistance at 1200–1400 °C because the micron α-Mo regions preferentially occurred plastic deformation and dynamic recrystallization, and then the occurrence of dynamic recovery and recrystallization of submicron α-Mo, Mo3Si and Mo5SiB2 regions was delayed. With increasing temperature, the occurrence of plastic deformation and dynamic recovery of submicron Mo3Si and Mo5SiB2 regions was easier, and the dynamic recovery and recrystallization of micron α-Mo regions was easier to occur compared to the submicron α-Mo regions in the bimodal alloy.

Activities to advance residual life evaluation techniques for highly aged power boiler materials

ABSTRACT In Japan, national guidelines of residual life evaluation for aged thermal power equipment were formulated in 1999. Several issues had recently come to light with the increase in ageing systems, including the emergence of unexpected mode of creep damage, the verification of practical applicability of the damage calibration curve generated in the laboratory, how to deal with creep-fatigue damage due to increased numbers of plant starts and stops, occurrence of plastic deformation in the accelerated creep test and the need for the creep damage monitoring method during plant operation. The Working Group to Advance Residual Life Evaluation Techniques was established in 2011 within the Society of Materials Science, Japan, to identify issues and discuss improvement measures. This paper provides an overview of the results of the working group activities.

Adhesion Evaluation of an Embedded SiN/GaAs Interface Using a Novel "Push-Out" Technique.

Adhesion assessments of an embedded interface in a multilayer system that contains a ductile layer are challenging. The occurrence of plastic deformation in the ductile layer often leads to additional complexity in analysis. In this study, an innovative "push-out" technique was devised to evaluate the interfacial toughness (Gin) of the embedded SiN/GaAs interface in a Au/SiN/GaAs multilayer system. Focus ion beam (FIB) milling was utilized to manufacture the miniaturized specimen and scratching with a conical indenter was used to apply load. This approach effectively minimized plastic deformation in the soft Au layer while inducing tensile stress to the embedded SiN/GaAs interface. As a result, the Au/SiN bilayer detached from the GaAs substrate with little plasticity. The energy associated with the interfacial delamination was derived from analyzing the load-displacement curves obtained from the scratching test. The Gin of the SiN/GaAs interface was calculated by means of energy analysis, and the average Gin was 4.86 ± 0.96 J m-2.

An adaptive multiscale quasicontinuum approach for mechanical simulations of elastoplastic periodic lattices

The quasicontinuum method is a multiscale method that combines locally supported coarse-grained domains, with small regions in which the microstructural model is fully resolved. This contribution proposes the first adaptive formulation of the method for microstructural elastoplasticity. The microstructural model uses an elastoplastic beam description. The indicator for refinement is the occurrence of plastic deformation, such that plasticity can only occur in fully resolved regions. An illustrative numerical example of a scratch test of an elastoplastic Kelvin lattice demonstrates the capabilities of the resulting framework.

Experimental and numerical study of contact fatigue for 18CrNiMo7-6 and 20MnCr5 carburized gear tooth

Gear manufacturers must make decisions about the manufacturing materials and superficial treatments. The best performance as to a type of failure should be evaluated. However, it is a time-demanding and costly process. The present work proposes a methodology for a comprehensive assessment (experimental and computational) of contact fatigue of gears in FZG test rig. The materials investigated were 18CrNiMo7-6 and 20MnCr5 alloy steels, widely used in industrial and automotive transmission systems, but with very different raw material costs, which can exceed twice the first compared to the second. The study evaluated the contact analysis between gears from the macroscopic point of view and the microscopic (inclusion of roughness). At the same time, the evolution of roughness and pit-damaged area after each test stage was monitored. The approach determined the stress field after each loading cycle and thus correlating the regions of higher stresses with surface and subsurface fatigue (micropitting and pitting). In addition, Weibull’s statistical analysis and SEM-EDS observations were executed. In many cases, the methodology correlated the increased roughness and pitting affected area with the regions submitted to the higher contact stress. Observations by SEM-EDS revealed that the occurrence of plastic deformation as a mechanism of wear should be considered in the equations of microscopic stress analysis. The similar fatigue life of such different materials may be correlated to the competitive mechanisms of higher mechanical strength of 18CrNiMo7-6 and better crack propagation characteristics of 20MnCr5. The methodology proved to be consistent for fatigue failure analysis of gears in FZG test rig.

Effects of number of slip systems on slip transmission between neighbouring grains

ABSTRACT Slip transmission between neighbouring grains is needed for the occurrence of plastic deformation in polycrystals. A geometric factor defined for a pair of grains with a certain orientation relationship is used to determine the slip transmission. Two slip transmission factors are calculated for randomly oriented grains. One is the slip transmission factor averaged for randomly oriented grains and the other is the minimum of the transmission factors among all possible orientation relationships. The possible number of slip systems in a grain varies for different metals and alloys. The effects of the number of slip systems on the transmission factors are discussed.

Indenter radius effect on mechanical response of a-(11–20), c-(0001), and m-(-1100) plane GaN single crystals in nanoindentation: A molecular dynamics study

Molecular dynamics (MD) simulation was used to systemically investigate the nanoindentation process of GaN. Different loading orientations and indenter radii were simulated and studied. In this work, the variation of stress propagation, particle movement and evolution of dislocations were discussed in detail. The size of the indenter has an important influence on the occurrence of plastic deformation. As the size of the indenter increases, the critical load of plastic deformation increases and the critical shear strain decreases. In addition, the nucleation and propagation of dislocations during initial plastic deformation is always along the low-strain region. The propagation of dislocation varied in a similar trend as the atomic displacement and atomic stress. The nano-hardness value of GaN during the indentation process was significantly affected by the size effect. Among them, the polar plane of GaN has higher hardness and the dislocations were pinned to the sample surface, which would not slip and propagate into the sample. However, during the indentation process perpendicular to the a-plane and m-plane, there were two types of dislocations in the sample, which were nailed to the surface or propagated to the inside of the sample.

Two-level mathematical models for determining the stress state and life plate with a hole

Modern trends in the development of mechanical engineering and other industries related to the production of materials and structures with a given set of physical, mechanical, and technological properties are aimed at reducing material consumption, energy consumption, increasing accuracy, reliability, and competitiveness of the manufactured product. Therefore, the creation of mathematical methods for assessing the stress state of structural elements based on the analysis of the elastic characteristics of a material, taking into account the peculiarities of its internal microstructure, is an actual task. The considered algorithm includes the following stages: identification of strength parameters using data obtained from images of the material microstructure; study of the stress-strain state of the model based on the variational-difference finite element method; formation of a system of linear algebraic equations for solving the problem of analyzing the elastic properties of a material using the plane problem of the theory of elasticity; construction of the material yield surface for a series of tests based on the strength criteria of composite materials, taking into account the different resistance of the material under tensile and compressive loads. Based on the developed mathematical model, the SSS and the yield surface of the plate with a hole are estimated. Structural analysis is performed at the macro and micro levels. The occurrence of plastic deformations at the micro-level can lead to the development of cracks and structural damage at the macro level. As a result of the study, the probability of plastic deformation in the plate is determined, and the critical zones of the model are established. The practical significance of the results obtained is to create an approach to assessing the mechanical properties of a material, such as elastic modulus, shear modulus, Poisson's ratio, and their probabilistic characteristics following the internal material structure. The proposed approach contributes to the expansion of knowledge about the material and allows to increase the valuable information obtained by modeling. To assess the probability of plastic deformations, the generated method uses the entire set of probabilistic characteristics of the yield surface.

Investigation of operational characteristics of axial displacement guides for thermal expansion systems of steam turbines

ТНЕ PURPOSE. To carry out a comparative analysis of the performance characteristics of the longitudinal movement guides of the external bearing housings of steam turbines, using the principle of rotation to ensure full contact of their lateral surfaces with the lateral surfaces of the guide groove at the base of the external bearing housing of the steam turbine. Compare the manufacturability of elements and their implementation for both existing and newly developed steam turbines .METHODS. The permissible transverse forces are determined from the strength conditions and compared for the traditional design of fixed longitudinal guides and the design of guides, in which the principle of rotation is used to avoid "biting" of the bearing housing on the guides when temperature misalignment appears along the flanges of the turbine cylinder. Also, the allowable forces are determined and compared from the condition of the absence of plastic deformations in any of the elements of the interface of the guides, the base frame and the bearing housing. Based on the results obtained, the value of the permissible temperature misalignment along the flanges of the turbine cylinder is estimated. The analysis was carried out in relation to the operating conditions of the front bearing housing and HPC of turbines of the T 100/120-130 UTZ family.RESULTS. It has been established that all the considered designs of guides with pivoting elements make it possible to exclude the occurrence of plastic deformations in the junction of the base frame and the outboard bearing housing at a temperature misalignment of 20°C regulated in most turbine operating instructions. CONCLUSION. The design of longitudinal keys proposed by UTZ does not require a change in the technology for manufacturing the foundation frames and allows the unit to be modernized during repairs in a CHP. The best performance disc guide design can be used in new turbine designs or factory retrofits.

Simulation of Deformations of Pre-Stressed Steel Trusses in Emergency Situations

Purpose of research is to make methodology and algorithm for finite element modeling in a single computational scheme of deformation of flat steel trusses, previously stressed using high-strength ropes, in accordance with the chronology of impacts on the object in the form of prestresses, normative loads and emergency destruction of one of the bearing elements.Methods. The solution of the problem is carried out in geometrically nonlinear staging using numerical integration based on Newmark approach with the construction of equilibrium equations of the finite element model of the structure in a deformed state at each integration step. Structural nonlinearity related to structural restructuring and consideration of ropes operation for tension only is described. The application of gravity forces of the carrier system, sequential introduction of tightening and their prestress, the application of payload and emergency impact in the form of instantaneous local destruction are traced. Before failure occurs, static loading condition is simulated using dynamic relaxation method. Methodology of accounting within numerical integration of emergency impact is formulated by application of dummy forces, values of which are calculated in excluded structural element before its destruction.Results. Performance of presented computational procedure is illustrated by the example of a flat steel truss calculation with a span (54 m), including two ropes. Object behavior is considered considering the break of one of the ropes subjected to preliminary stress. It was revealed that the investigated emergency does not lead to the destruction of the second rope and the occurrence of plastic deformations in the truss rods.Conclusion: Completed developments can be used to ensure the survivability of pre-stressed steel trusses under beyond design basis effects, leading to the destruction of individual structural elements.

Estimation of residual stress level in plasma coatings of increased thickness

Regulation of the thermal and stress state of the “coating-base” system is an important step of the coatings quality management and is carried out by changing the thermal power of the plasma jet per unit of the sprayed surface by controlling the movement velocity of the plasma torch and the sprayed material flow rate. (Research purpose) The research purpose is development of a mathematical model that describes the process of layer-by-layer coatings formation and the change in the thermal state of the coating-base system during plasma spraying. (Materials and methods) We have used finite differences, finite elements and marching for solving the thermal and strength problems in internal stresses determining. We have used a technique for determining thermal fields, considering the dependence of thermal-physical and mechanical properties of the coating and base materials on temperature, the occurrence of plastic deformations and stress relaxation. A mathematical model has been designed for calculating a thermal field with a moving boundary considering the nonlinear nature of coating growth during layer-by-layer deposition and the dependence on the thermophysical properties of the coating-base system materials. We have substantiated the method that allows eliminating the existing shortcomings of traditional technologies for design and experimental studies of the thermal and stress state of the coating-base system, as well as automatization of the process of solving the numerical model and increasing the efficiency of the entire research cycle. (Results and discussion) It was found that when the flow rate of the sprayed material is changed from 0.1 to 1.0 grams per second and the plasma torch travel velocity is from 10 to 350 millimeters per second, the residual stresses in PG-19M-01 coatings on steel change their sign and can be both compressive and tensile. Varying the coating conditions allows reducing the level of residual stresses by 3-5 times. The article shows that a decrease in the level of residual stresses corresponds to an increase in the coating adhesion strength at a constant mass average temperature of the particles during the deposition process and is achieved by controlling the sprayed material flow rate and the plasma torch velocity, pre-heating the substrate and cooling. (Conclusion) It was found that the use of the proposed model makes it possible to evaluate the effect of the parameters of the spraying process (plasma torch travel velocity, spray material consumption, thermal state of the substrate before spraying, cooling conditions during spraying) on the residual stresses level.

Elastoplastic Equilibrium of a Hollow Cylinder from an Inhomogeneous Perfectly Plastic Material

The article deals with the axisymmetric elastoplastic problem for a hollow thick-walled cylinder (plane deformed state), loaded from the inside and outside by uniform pressures proportional to one parameter. The material is considered to be perfectly plastic, with the elastic modulus and yield strength generally are arbitrary functions of the radius. In addition, the material is considered to be incompressible in both plastic and elastic zones. On the basis of the criteria for the plasticity of Huber - Mises and Tresca - Saint-Venant, the radius at which the first plastic deformations occur is determined. It is shown that, depending on the functions of the inhomogeneity of elastic and plastic parameters and loads, the occurrence of plastic deformations is possible both on the surfaces and on the inner walls of the cylinder.

Elastoplastic Equilibrium of a Hollow Thick-Walled Radially Inhomogeneous Ball

The article deals with the axisymmetric elastoplastic problem for a hollow thick-walled ball (plane deformed state), loaded from the inside and outside by uniform pressures proportional to one parameter. The material is considered to be perfectly plastic, with the elastic modulus and yield strength generally are arbitrary functions of the radius. In addition, the material is considered to be incompressible in both plastic and elastic zones. On the basis of the criteria for the plasticity of Huber - Mises and Tresca - Saint-Venant, the radius at which the first plastic deformations occur is determined. It is shown that, depending on the functions of the inhomogeneity of elastic and plastic parameters and loads, the occurrence of plastic deformations is possible both on the surfaces and on the inner walls of the ball.

Phase field modeling to transformation induced plasticity in super-elastic NiTi shape memory alloy single crystal

A crystal plasticity based phase field model was established to investigate the occurrence of transformation induced plasticity (TRIP) and its effect on the cyclic transformation of super-elastic NiTi shape memory alloy (SMA) single crystal. The simulation shows that the martensite transformation and its reverse result in the occurrence of plastic deformation in the NiTi SMA single crystal and the mode of phase transition changes from a localized mode into a homogeneous one with the cycles. When the single crystal exhibits a localized martensite transformation, the TRIP occurs regularly at the interfaces between the martensite-dominated and austenite-dominated domains and then the strips of equivalent plastic strain are formed; meanwhile the TRIP hinders the martensite transformation in the austenite-dominated domains but promotes that in the martensite-dominated ones. When the transformation becomes homogeneous, the TRIP occurs in a scattered mode and with a high value, and promotes the martensite transformation in the whole single crystal. In addition, the interaction between the residual martensite phase and TRIP is investigated, and the results demonstrate that they promote each other to some extent.