Total Equivalent Plastic Strain Research Articles

An Experimental and Numerical Study on Forming Force, Fracture Behavior, and Strain States in Two Point Incremental Forming Process

Two-point incremental sheet forming process (TPIF) is an emerging and promising manufacturing process for the production of complex geometries or customized functional sheet components. In this study, the single-pass TPIF process is investigated using experimental and numerical approaches to study the forming force evolution, fracture behavior and strain states with a varied wall angle hemisphere shape. It can be concluded that both the peak force and fracture depth increases with tool diameter and incremental depth in TPIF process. It seems the deformation mechanism or the failure mechanism is strongly dependent on particular forming conditions based on a failure parts morphology observation. FEM simulation results indicated that the major plastic strain is positive while the minor plastic strain is negative in the TPIF process on a hemiphere shape. it can be concluded that the strain increment and total equivalent plastic strain is affected by both tool diameter and incremental depth.

Analysis of deformation induced martensite in AISI 316L stainless steel

Abstract Metastable austenite stainless steel AISI 316L is sensitive to cold deformation, where transformation from austenite to martensite occurred. The bending deformation as the formation process leads to tensile and compression troughout the thickness of the billet. Tensile testing of the specimen causes differences in the true stress-strain along the contraction neck prior to fracture as well. The aim of the paper is to find correlation between microhardness as brief inspection parameters and extension of martensitic transformation. The total equivalent plastic strain extend diagram obtained by numerical simulation of bending was compared with tensile true stress-strain diagram. Results show very good correlation between hardness, true strain and martesite content. Therefore, one can conclude that by hardness measurement, it is possible to measure the level of equivalent plastic strain until ultimate tensile stress as a linear correlation between hardness, true strain and martesite content.

Modeling the Thermal Fields of Deposited Materials During the Spray Rolling Process

The technology of spray rolling can be applied to manufacture strips with a uniform cooling rate and a high production rate. The cooling behavior of the spray-rolled material prior to rolling contact was studied using mathematical models, tracing the accumulation of multi-layers with respect to time. Thermal history, elastic–plastic, and friction behavior of the material were considered in the complicated rolling process. The developed model had a good agreement with experimental results with potential to be utilized for prediction of the spray-rolled material thermal profile. Results show that the temperature of deposited materials prior to/or during rolling and the total equivalent plastic strain distribution in the deformation zone of deposited materials during rolling increase with increasing roller preheating temperature, the initial droplet temperature, and the mass flux distribution of the spray cone. Moreover, the deposit thickness and enthalpy remaining in the deposit are found to be the dominant influencing factors on the thermal field of deposited materials during the spray rolling process.

Finite element modelling and experimental analysis of the processing conditions for obtaining straight blades by isothermal forging of a nanostructured aluminium-magnesium alloy

In this present study, both the design and the optimal manufacturing conditions for processing a straight blade by isothermal forging are shown. The starting material has been previously deformed by a severe plastic deformation (SPD) process known as equal channel angular extrusion (ECAE). As is well-known, the ECAE process is a technology which allows us to obtain materials with sub-micrometric grain size. These nanostructured materials can be employed afterwards as initial materials for other manufacturing processes. The use of these ultra fine grain sized materials (UFG) provides improved mechanical properties such as: greater hardness and mechanical strength, among others. In this present study, FEM simulations of the isothermal forging of an AA5083 previously deformed by ECAE will be carried out. The total equivalent plastic strain, the damage and the forces required to carry out the isothermal forging of this nanostructured aluminium alloy will be determined.

Finite element analysis of strain distribution in ZK60 Mg alloy during cyclic extrusion and compression

Finite element method was used to study the strain distribution in ZK60 Mg alloy during multi-pass cyclic extrusion and compression (CEC). In order to optimize the CEC processing, the effects of friction condition and die geometry on the distribution of total equivalent plastic strain were investigated. The results show that the strain distributions in the workpieces are inhomogeneous after CEC deformation. The strains of the both ends of the workpieces are lower than that of the center region. The process parameters have significant effects on the strain distribution. The friction between die and workpiece is detrimental to strain homogeneity, thus the friction should be decreased. In order to improve the strain homogeneity, a large corner radius and a low extrusion angle should be used.

Neural network based modeling and optimization of deep drawing – extrusion combined process

A combined deep drawing---extrusion process is modeled with artificial neural networks (ANN's). The process is used for manufacturing synchronizer rings and it combines sheet and bulk metal forming processes. Input---output data relevant to the process was collected. The inputs represent geometrical parameters of the synchronizer ring and the outputs are the total equivalent plastic strain (TEPS), contact ratio and forming force. This data is used to train the ANN which approximates the input-output relation well and therefore can be relied on in predicting the process input parameters that will result in desired outputs provided by the designer. The complex method constrained optimization is applied to the ANN model to find the inputs or geometrical parameters that will produce the desired or optimum values of TEPS, contact ratio and forming force. This information will be very hard to obtain by just looking at the available historical input---output data. Therefore, the presented technique is very useful for selection of process design parameters to obtain desired product properties.

Application of Orthogonal Test in Numerical Simulation of Aluminum Sheet Forming

Sheet forming is a high-volume fabrication method for producing lightweight materials components. An important goal in manufacturing research is to determine the optimum method for producing products with less cost. In this paper, combined with the orthogonal test method and finite element method (FEM) simulation, the analysis was carried out to analyze the key process factors such as stamping force, fillet radius, and friction coefficient. Using orthogonal test method can reduce the testing time, learn how the molding parameters influence the total equivalent plastic strain, acquire the best match forming parameters, and give guidance for the better condition

Analysis of Metal Flow and Deformation Features during Continuous Tube Rolling Process with Mandrel Mill

With the aid of commercial FE code MSC.SuperForm, the structural steel tube continuous rolling process of a typical hollow tube specification 152.5×12.5mm is simulated based on Bao Steel 152.5 main pass sequence of 140mm 8-stand mandrel mill, and the distribution characteristics of stress/strain, outline lateral spread, temperature changes of workpiece in continuous rolling process and distribution of stress/strain, friction of workpiece in deformation zone are analyzed. Analysis results indicate that deformation of workpiece along the width of the groove, especially at the top and the bottom of the groove is highly inhomogeneous due to the unequal draught and the longitudinal stress of special position (the top and the bottom of the groove) of workpiece is always an alternate state, in a tensile-compressive-tensile manner, and has a distinct rule. In the first stand, outline dimension of workpiece gradually increases during reducing process and early stage of wall thickness reduction, but it gradually decreases during middle-late stage of wall thickness reduction and tends towards stability at last. It is inhomogeneous that distribution of unit compressive stress and longitudinal strain of workpiece in deformation zone, and contact stress and total equivalent plastic strain are maximal in inner surface of workpiece contacting with mandrel. Temperature difference between the outer and the inner surfaces of workpiece is obvious.

A study on equal channel angular drawing (ECAD) of AA-1370 processed by route B

Equal channel angular drawing (ECAD) process is an innovative method for manufacturing high resistance wires. The aim of this process is to introduce plastic strain in the processed materials in order to obtain high resistance wires as a consequence of the strain-hardening behaviour. This process can be compared with traditional wire-drawing due to the similar profile of plastic strain achieved in the processed material. With both processes, more deformation is achieved at the perimeter of the wire than in the centre. Nevertheless, the main difference between both processes is that, for the same cross-section reduction, the ECAD process is able to produce more plastic strain in the material than that obtained by using wire-drawing processes. This study will show the distribution of total equivalent plastic strain in each of the four passages with route B that the material is going to undergo as well as in the final calibration passage. This will be calculated using the FEM software MSC Marc MentatTM. Furthermore, the drawing force obtained from FEM models will be compared to real ECAD experiments for the case of aluminium alloy AA-1370. Finally, the stress distribution inside the ECAD dies will be modelled using a three-dimensional meshing.

Modeling and finite element analysis of rod and wire steel rolling process

Two thermomechanical coupled elastic-plastic finite element (FE) models were developed for predicting the 12-pass continuous rolling process of GCr15 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.

Simultaneous Control of Shape and Properties of AZ31 Magnesium Alloy Sheets by Incremental Forming

In this study, simultaneous control of shape and hardness of AZ31 magnesium alloy sheets by incremental forming process was proposed. Influences of working temperature, giving strain and heat treatment temperature on hardness were investigated. AZ31 magnesium alloy sheets were formed into pyramidal shape by incremental forming process at 100°C and 200°C. Major strains given to the pyramidal faces were 0.1,0.2 and 0.3. After forming, heat treatment was carried out at various temperatures. Combination of final shape and total equivalent plastic strain were changed by multi-step forming and hardness distribution was measured. From the experimental results, it was found that when heat treatment was done at 200°C for 10 min after forming at 200°C, hardness of the specimen became higher than that of as received one. When heat treatment was carried out at 175°C for 60 min after forming at 100°C, hardness of the specimen also increased. In the case of multi-step forming, strain was accumulated at forming temperature of 100°C and hardness increased, but not at the forming temperature of 200°C. By multi-step forming at 100°C, asymmetric hardness distribution with symmetric shape was realized and simultaneous control of shape and hardness was succeeded.