Reversible Plastic Deformation Research Articles

Effect of the Initial Orientation of a Working Tool on the Stress–Strain State during Reversible Surface Plastic Deformation

Effect of the Initial Orientation of a Working Tool on the Stress–Strain State during Reversible Surface Plastic Deformation

Influence of Tool Geometry on the Stress–Strain State of Cylindrical Parts in Reversible Surface Plastic Deformation

Influence of Tool Geometry on the Stress–Strain State of Cylindrical Parts in Reversible Surface Plastic Deformation

Determination of temperature in the deformation zone during reversible surface plastic deformation

Finishing and hardening treatment by reversible surface plastic deformation of cylindrical parts is considered. By computational modeling in the ANSYS program, a finite element model is built to determine the temperature in the deformation zone depending on the parameters of the processing mode, and their influence is determined. A critical temperature is established, the excess of which reduces temporary and residual stresses. Keywords: reversible surface plastic deformation, two-radius roller, computational modeling, temperature, deformation zone. zsa@istu.edu, nquan6799@gmail.com

Influence of the geometry of the tool on stress-strain state cylindrical parts with reversible surface plastic deformation

Finishing-hardening treatment of shafts and axles by reversible surface plastic deformation is considered. A finite element model of the stress-strain state of the surface layer of cylindrical parts is constructed by 3D design and computational modeling, taking into account the geometry of the tool. It has been established that a decrease in the profile radius, roller diameter, and billet diameter increases the temporary and residual stresses in the surface layer. The optimal distance between the vertices of a two-radius roller is determined, which ensures the maximum stress state while all other conditions being equal. Keywords: reversible surface plastic deformation, distance between roller vertices, profile radius, temporary and residual stresses, plastic deformation. zsa@istu.edu, nquan6799@gmail.com

Influence of reversible surface plastic deformation on changes in the grain structure of carbon steel

Influence of reversible surface plastic deformation on changes in the grain structure of carbon steel

Оценка геометрических параметров отпечатка и давления в зоне контакта рабочего инструмента с заготовкой при реверсивном поверхностном пластическом деформировании

The article presents the results of modeling and determining the influence of the parameters of reverse surface plastic deformation on the geometric characteristics of the plastic imprint and the pressure in the contact zone of the working tool under static and reverse impact. Using the software for 3D design SOLID WORKS-2019 and computational modeling in ANSYS-19.1, a finite element model of the contact zone was built to determine the geometric characteristics of the plastic indentation and the contact pressure between the working tool and the surface of the workpiece, depending on the geometry of the working tool, reversing frequency its rotation, the initial angle of installation and the amplitude of the angle of reverse rotation of the working tool. Based on the obtained results, to increase the pressure in the contact zone of the working tool with the workpiece, which affects the degree of hardening and smoothing of microroughnesses of the workpiece surface and the formation of compressive residual stresses, it is recommended to use the following parameters and hardening modes: working roller with a diameter of 20–30 mm, with a profile radius of 2 –2.5 mm, distance between tops of working roller profile 1.5–2 mm, initial installation angle of the working roller 90о, amplitude of the reverse rotation angle of the working roller ±6 – ±8о and reverse speed of the working roller 200–240 double strokes/min.

Влияние реверсивного поверхностного пластического деформирования на параметры волнистости цилиндрических деталей

The results of experimental studies to determine the influence of the parameters of reversible surface plastic deformation on the parameters of the surface waviness of cylindrical parts made of steel 45, are presented. The proposed method implemen-tation for finishing and hardening treatment requires the development of a device for the formation of a reversing circular motion of the working tool. On completion of experimental studies using the PyCharm computer program and Python pro-gramming language, optimal modes of simplification were determined, providing the lowest waviness height.

Effect of parameters of reversible surface plastic deformation on temperature in contact zone of tool with workpiece

The article presents the results of experimental studies to determine the influence of the main technological parameters of reverse surface plastic deformation (SPD) on the temperature in the contact zone of the working tool with the workpiece. To implement the proposed method of finishing and hardening processing, a device has been developed that provides a reverse circular movement of the working tool. Using a FLIR SC7000 series thermal imager, the temperature in the contact zone of the working tool with the workpiece was determined. Experimental studies have shown that the value of the temperature on the surface of the workpiece with reverse SPD varies from 42 to 123 °C and depends on the main technological parameters of the process. It has been established that the temperature exceeding 123 °C at the contact leads to a decrease in the maximum intensity of residual stresses in the surface layer of the part. Based on the results of experimental studies and using the PyCharm computer program with the Python programming language, optimal hardening modes were determined that provide the minimum surface temperature of the part, which makes it possible to maintain the quality of the surface layer after hardening.

Mechanical properties of hardened layer under reversible surface plastic deformation

The article presents the results of experimental studies to determine the influence of the parameters of reverse surface plastic deformation (RPD) on the mechanical properties of the surface layer of cylindrical parts made of carbon steel 45. To implement the proposed method of finishing and hardening processing, a device has been developed that provides reverse circular motion of the working tool. Using the HBRV-187.5 hardness tester, HMV-G21 microhardness tester and MET-2 microscope, the hardness of the surface layer, microhardness, grain structure and depth of the hardened layer of hardened parts were determined. Experimental studies have shown that after reverse SPD, the hardness of the surface layer increases by 9...15 % compared to the hardness of the original surface, and the microhardness increases by 1,6...1,8 times, which leads to a significant hardening of the surface layer. The depth of the hardened layer is 0.8...1.6 mm, and the degree of hardening is 55...80 %. According to the results of experimental studies and using the PyCharm computer program with the Python programming language, the optimal modes of hardening by reverse SPD were determined, providing both the maximum depth and the highest degree of hardening of the surface layer, which are formed under the following processing modes: longitudinal feed 0.08...0,10 mm/rev; workpiece rotation frequency 280...300 rpm; the value of the radial interference 0.28...0.30 mm; reverse speed RI 290...300 strokes/min; the initial installation angle of RI is 90° and the value of the angle of reverse rotation of RI is ±15°.

FEATURES OF THE CALCULATION OF THE USED PLASTICITY RESOURCE DURING COLD FORMING OF GLASS-TYPE PRODUCTS

The reverse extrusion process is widely used in the production of “Glass” type parts. Due to high technical and economic indicators and great technological possibilities, in recent years, cold plastic deformation has become widely used in machine- and instrument-building plants, in the electrical and radio engineering industry, as well as in other branches of the national economy. However, the possibility of cold plastic deformation by the extrusion method is not yet sufficiently used. The reason is that, traditionally, during the design of metal pressure processing processes, attention is paid to determining the power parameters and ensuring the geometric accuracy of the workpieces. But this does not allow us to assess the ultimate shape change and technological heredity of the finished products and make a quantitative assessment of the damage of the deformed metal. In this work, the process of forming products of the “Glass” type by reverse cold plastic deformation is investigated, in which the used plasticity resource is taken as the most important parameter responsible for the quality of the products. The method of calculation of the used resource of plasticity of “Glass” blanks in the processes of reverse cold plastic forming is clarified. When calculating the used plasticity resource, the effect of the volume of the stress state scheme is taken into account by using the limit deformation surface instead of the plasticity diagrams. The graphs of distribution of the resource of plasticity by the radius of the workpiece are obtained. From the analysis of the results it follows that the greatest intensity of accumulation of damage occurs in the areas of maximum irregularity of plastic deformation. Points of contact of the punch with the workpiece turned out to be dangerous. The use of hydrostatic support in reverse extraction allowed not only to reduce the degree of plasticity used, but also to obtain a more uniform distribution of it, therefore, to improve the quality of the obtained blanks when reverse extrusion and improve the technological heredity of the finished products. The results obtained in the work can be used to estimate the limit change in shape in similar technological processes, which are accompanied by a volumetric scheme of the stressed state.

Stress-strain state of surface layer under reversible surface plastic deformation of machine parts

The article considers an approach to increasing the stress state in the elastic-plastic deformation zone during surface plastic deformation. The technical idea of solving the problem is based on the complication of the kinematics of a two-radius roller. To achieve this goal, the finite element method based on the ANSYS computer program was used, which makes it possible to determine the values of temporary, residual stresses and strains for different schemes of reversible surface plastic deformation with a two-radius roller. It has been established that the greatest influence on the stress-strain state in the deformation zone is exerted by the scheme of reverse rotation of a two-radius roller located at an angle of 45 degrees relative to the direction of movement, and the least effect is when hardening with a two-radius roller, the axis of rotation of which coincides with the direction of movement.

A combined experimental-numerical study of residual stress and its relaxation on laser shock peened SiC particle-reinforced 2009 aluminum metal matrix composites

Residual stresses have significant influences on the in-service performance of materials. Laser shock peening (LSP), a technique generating processing-based residual stress, is employed to introduce high-amplitude and large-depth compressive residual stress in SiC particle-reinforced 2009 aluminum (SiC/2009Al) metal matrix composites. Surface residual stresses after single-shot LSP and multiple shots of overlapped LSP were investigated. Single-shot LSP with 10 J, 20 J, 30 J, and 40 J laser energies introduced average surface residual stresses of −126.7 MPa, −129.3 MPa, −85.7 MPa, and −69.3 MPa. Multiple shots with energies of 20 J were inflicted twice on the surface undergoing LSP and exhibited a maximum residual compressive stress of −266.7 MPa. Then, the surface residual stress decreased from −266.7 MPa to −215.3 MPa and further to −212.7 MPa when subjected to 10,000 and 100,000 fatigue cycles. Relaxation also occurred under thermal loads, and the stress decreased from −266.7 MPa to −129.3 MPa after holding at 100 °C for 50 h. Furthermore, simulation of the LSP process was conducted with the SiC/2009Al composite and showed that SiC particles close to the peening surface generated more reverse plastic deformation and resulted in some residual tensile stress in their surroundings. This combined experimental and numerical research seeks to provide deep insight into residual stress distribution and explore the applicability of LSP with metal matrix composites. • Single shot and multiple shots LSP was conducted on SiC/2009Al metal matrix composites. • The presence of SiC particles generates local tensile stresses in the vicinity of SiC particles. • The residual stresses on SiC/2009Al show great resistance to the fatigue cycles. • The residual stresses on SiC/2009Al show poor resistance to the thermal loads.

Cyclic Deformation of Microcantilevers Using In-Situ Micromanipulation

BackgroundThe trend in miniaturisation of structural components and continuous development of more advanced crystal plasticity models point towards the need for understanding cyclic properties of engineering materials at the microscale. Though the technology of focused ion beam milling enables the preparation of micron-sized samples for mechanical testing using nanoindenters, much of the focus has been on monotonic testing since the limited 1D motion of nanoindenters imposes restrictions on both sample preparation and cyclic testing.Objective/MethodsIn this work, we present an approach for cyclic microcantilever bending using a micromanipulator setup having three degrees of freedom, thereby offering more flexibility. ResultsThe method has been demonstrated and validated by cyclic bending of Alloy 718plus microcantilevers prepared on a bulk specimen. The experiments reveal that this method is reliable and produces results that are comparable to a nanoindenter setup.ConclusionsDue to the flexibility of the method, it offers straightforward testing of cantilevers manufactured at arbitrary position on bulk samples with fully reversed plastic deformation. Specific microstructural features, e.g., selected orientations, grain boundaries, phase boundaries etc., can therefore be easily targeted.

Versatile Organosuperelastic Deformability by Multiple Mechanical Twinning

Reversible and versatile plastic deformation of crystalline solids over elastic limits is achieved in a diffusionless manner on the basis of a mechanically induced structural transition. Specific a...

Roles of Hydrogen and Plastic Strain Distribution on Delayed Crack Growth in Single-crystalline Fe–Si alloy

Abstract Effects of hydrogen on macroscopic and microscopic features of crack growth in thin specimens were investigated using a thin sheet of single-crystal Fe-3wt%Si alloy. Center-cracked specimens were tested under a sustained load in a hydrogen environment, and under continuous stretching in an air environment. The fracture features were compared to elucidate the role of hydrogen in hydrogen-induced delayed crack growth. In both air and hydrogen environments, the crack growth mode of the thin specimens was the same as that of the thick specimens, despite the significantly reduced thickness. Surprisingly, the crack grew discontinuously, and left striations on the fracture surface, in which shorter striation spacing was observed in hydrogen. In addition, there was a similarity in the deformation microstructures beneath the fracture surface, that is, both microstructures were composed of three distinct layers characterized by different plastic strain gradients and dislocation densities. In the hydrogen environment, the hydrogen-enhanced localized plasticity (HELP) mechanism is believed to be relevant to the crack growth process. Also, HELP was supposed to cause different characteristics (the magnitude of plastic strain, the plastic strain gradient, and dislocation structure) of the three layers in the hydrogen compared to those in the air. Reverse plastic deformation occurred in the regions behind the crack front during crack growth, which is speculated to contribute not only to enlarge the crack tip opening angle (CTOA) but also to blunt the crack tip.

Effect of Reversible Cyclic Plastic Deformation and Thermal Treatment on the Microstructure and Mechanical Properties of SS304L Steel

In the present study, the effect of heat treatment and reversible cyclic plastic deformation (RCPD) on microstructure and mechanical properties of stainless steel 304L (SS304L) has been examined. The RCPD demonstrated a significant reduction in the grain size as well as formation of deformation-induced twins, without any observable phase transformation in the SS304L specimens. An isothermal annealing of as-received specimens at 950 °C (1223 K) for varying annealing durations exhibited the formation of recrystallized equiaxed austenitic microstructure. It was also observed that the grain size and the twin width increased simultaneously with annealing time, wherein the grain size increased linearly, whereas the increment in the twin width was parabolic in nature. The density of deformation twins decreased with increasing annealing time, which was attributed to the variation in the stacking fault energy (SFE) with temperature and duration of annealing treatment. The average hardness values decreased with increasing annealing time, and this trend was correlated with the increasing grain sizes and, simultaneously, decreasing amount of twin density.

Reversible deformation in nanocrystalline TWIP steel during cyclic loading by partial slip reversal and detwinning

Mechanical responses of nanostructured twinning induced plasticity (TWIP) steels have attracted attention owing to their ultra high strength and ductility. A set of molecular dynamics simulations were carried out to characterize and track the atomic structure of Fe–22Mn (wt. %) nanocrystalline TWIP steel during reverse loading (tension-compression). The results show that intrinsic stacking faults and deformation twins which were formed during forward tensile loading up to total strain of 5.8% were eliminated upon subsequent reverse compression loading up to strain of 0.0 %. The current study provides the first simulation evidence of detwinning in nanocrystalline TWIP steel during the reverse loading. The atomic structure and dislocation analysis show that the observed detwinning is due to the dependence of shear stress acting on the trailing and leading partial dislocations on the loading direction. The results show that the Schmid factor of the trailing partial dislocations in compression loading are larger than leading partial dislocations one. The reversible deformation by detwinning could allow for reversible plastic deformation, storage of energy and mechanical damping in micro or nano devices.

Effect of Underloads on Plasticity-Induced Crack Closure: A Numerical Analysis

The effect of underloads is mostly quantified by the averaged effect on the fatigue crack growth rate, and the transient behavior is rarely investigated. The objective of this paper is to study the mechanisms behind the effect of underloads, periodic underloads, and underloads combined with overloads. A single underload smashes the material around the crack tip, producing a depression on crack flank and a local reduction of contact forces at the minimum load. The reduction of plastic elongation behind the crack tip has an immediate effect on crack opening level, which rapidly disappears with crack propagation. The smashing associated with the compressive force occurs mainly behind the crack tip position where the underload was applied. The effect of the underload is intimately linked to reversed plastic deformation, which explains its enhanced effect for kinematic hardening. The decrease of load below the minimum baseline load is the main loading parameter. The application of periodic underloads extends the effect of a single underload. The effect of the underload is enhanced by the presence of obstacles in the form of residual plastic deformation, which explains the great effect of underloads applied after overloads.

Effect of rolling direction on microstructure evolution of CL60 wheel steel

The effect of rolling direction on the microstructure evolution of CL60 wheel steel was systematically studied using a rolling-sliding wear testing apparatus. The evolution of microstructures in depth and on the sub-surface was investigated using Electron Backscatter Diffraction (EBSD) and scanning electron microscopy (SEM). The results indicated that the microstructure in depth underwent a transition from the sub-boundaries introduced at low strain into grains with large-angle grain boundaries (LAGBs), leading to a full ultra-fine grain (UFG) microstructure at a large strain. Notably, an abnormal growth of the strain-induced UFGs near the surface occurred at the beginning of the rolling direction reversal (RDR). Meanwhile, the microstructure of the surface layer was changed from a fiber structure parallel to the surface under the unidirectional rolling of wheel materials to a wave structure. With the increase in the number of cycles after the RDR, the grain orientation on the sub-surface was changed from {111} to {101} and finally to a random orientation, resulting in a completely reversed plastic deformation layer. Additionally, the number of cycles per reversal and the total number of cycles also played an important role in microstructure evolution.

Research on Submicron-Grained Structure Formation in Titanium Alloys upon Reversible Hydrogenation and Plastic Deformation

Abstract—The influence of thermohydrogen treatment combined with hot rolling on the structural formation in α- and near-α-titanium alloys has been studied. The prospects of obtaining submicron-grained sheet semifinished products of VT5 (Ti–5.8Al–0.1Fe, wt %) and VT20 (Ti–5.9Al–1.5V–1.2Mo–1.8Zr–0.1Fe, wt %) alloys are shown. In these materials, a submicron-grained structure allows the plastic deformation to be induced by superplasticity at temperatures reduced by 100–200°С.