Experimental Investigations of Induction Heating in Warm Forming of Stainless Steel Sheets

The main objective of this study is to investigate the effect of heating conditions on the temperature distribution in sheet metal. An AMS5604 stainless steel sheet was heated in an induction heater. Then, the hot workpiece was transported to the stamping tool. The uniform temperature distribution is a key factor influencing the possibility of forming and quality of warm-formed parts. To study the temperature distribution in sheet plate we carried out the measurements using termoelements. Furthermore, thermovisual measurements were performed using a FLIR P 640 thermovisual camera. It was found that to improve the uniformity of the temperature distribution in the workpiece the time of heating should be increased. However, the time of transport of the sheet to the tool should be decreased. During air cooling a decrease of the difference between the maximal and minimal temperature of the sheet is observed

Multiphysics Modeling and Numerical Simulation in Computer-Aided Manufacturing Processes

The concept of Industry 4.0 is defined as a common term for technology and the concept of new digital tools to optimize the manufacturing process. Within this framework of modular smart factories, cyber-physical systems monitor physical processes creating a virtual copy of the physical world and making decentralized decisions. This article presents a review of the literature on virtual methods of computer-aided manufacturing processes. Numerical modeling is used to predict stress and temperature distribution, springback, material flow, and prediction of phase transformations, as well as for determining forming forces and the locations of potential wrinkling and cracking. The scope of the review has been limited to the last ten years, with an emphasis on the current state of knowledge. Intelligent production driven by the concept of Industry 4.0 and the demand for high-quality equipment in the aerospace and automotive industries forces the development of manufacturing techniques to progress towards intelligent manufacturing and ecological production. Multi-scale approaches that tend to move from macro- to micro- parameters become very important in numerical optimization programs. The software requirements for optimizing a fully coupled thermo-mechanical microstructure then increase rapidly. The highly advanced simulation programs based on our knowledge of physical and mechanical phenomena occurring in non-homogeneous materials allow a significant acceleration of the introduction of new products and the optimization of existing processes.publishedVersio

Experimental and Numerical Investigation of Impact Resistance of Riveted and RFSSW Stringer-Stiffened Panels in Blunt Impact Tests

Aluminium alloy sheets have come into widespread use in the design of stringer-stiffened aerospace structures. This paper evaluates experimentally and numerically the response of stringer-stiffened Alclad 7075-T6 aluminium alloy panels subjected to impact loading. The aim of the study was to compare the impact resistance of riveted structures with the structures with the impact resistance of structures welded using the refill friction stir spot welding (RFSSW) process, which is a relatively new technique now used to create joints in aircraft structures. The experimental tests were carried out using a drop-weight type impact testing machine. Finite element modelling of stringer-stiffened panels under impact loading was carried out by using the nonlinear finite element-based MSC.Marc + Mentat program. The results of the numerical computations were validated against the experimental data. Studies were also made of the resistance of the joints to failure, the springback response and the stiffness of joints in the conditions of the dynamic impact test

A Study of the Coefficient of Friction in Steel Sheets Forming

The aim of this paper was to compare the tribological properties of a deep drawing quality steel sheet using the three commonly used friction tests, i.e., the strip drawing test, draw bead test, and bending under tension test. All tests have been carried out using a specially designed friction simulator. The test material was a 0.8-mm-thick DC04 steel sheet, commonly used in the automotive industry. Uniaxial tensile tests have been carried out to characterise the mechanical properties of the specimens. Furthermore, measurements of the sheet surface topography have been carried out to characterise the tribological properties of the specimens. The friction tests have been conducted under different pressure and lubrication conditions, surface roughnesses of tools represented by counter-samples, and orientations of the specimens according to the direction of the sheet rolling. A comparative analysis of the results of the friction tests revealed different values of friction. In the strip drawing test, the value of the coefficient of friction decreases as the contact pressure increases for both dry and lubricated conditions. In the draw bead test, the specimens oriented along the rolling direction demonstrated a higher value of the coefficient of friction compared to the samples cut transverse to the rolling direction. In contrast to the strip drawing test, the specimens tested in the bending under tension test exhibit a tendency to an increase in the value of the coefficient of friction with the increasing contact pressure

Experimental Assessment of the Depth of the Deformed Layer in the Roller Burnishing Process

This paper presents the methods of experimental determining the depth of the plastically deformed top layer in the roller burnishing process. Precise determination of the depth of the plastically deformed layer is difficult due to slight deformation at the boundary of the plastic and elastic zone, the lack of visible changes in the microstructure, and minimal changes in microhardness. The article shows the method of original measurement method that consists in determining the thickness of the deformed layer using rings. The method involves the profilographometric measurements of the disconnected rings (samples) which are flat-faced in the package on the mandrel. The rings material deforms plastically in the surface layer causing wrapping of the end face of the ring in the direction of the rolling tool movement. After dismantling the ring pack, measurements were made on the face of each ring along radial directions, and the thickness of the deformed layer was observed on the microscope. The method was verified by microhardness measurements in the cross-section and cross-section of the ring. The results of deformation depth measurements were verified by finite-element-based numerical simulation

A 3D FEM-Based Numerical Analysis of the Sheet Metal Strip Flowing Through Drawbead Simulator

Drawbeads are elements of the stamping die and they are used to compensate material flow resistance around the perimeter of the drawpiece or to change the stress state in specific regions of the drawpiece. This paper presents the results of experimental and numerical analyses of tests of sheet metal flowing through a drawbead. The tests have been carried out using a special tribological simulator of the drawbead. Experimental tests to determine the coefficient of friction (COF) have been carried out for three widths of sheet metal strip and two drawbead heights. The three-dimensional (3D) elastic-plastic numerical computations were performed using the MSC. Marc program. Special attention was given to the effect of material flow through the drawbead on the distribution of the normal stress on the tool-sheet interface. The mesh sensitivity analysis based on the value of the drawing force of the specimen being pulled through the drawbead allowed an optimal mesh size to be determined. The errors between the numerically predicted values of the COF and the values experimentally determined ranged from about 0.95% to 7.1% in the cases analysed. In the case of a drawbead height of 12 mm, the numerical model overestimated the value of the COF for all specimen widths analysed. By contrast, in the case of a drawbead height of 18 mm, all experimentally determined friction coefficients are underestimated by Finite Element Method (FEM). This was explained by the different character of sheet deformation under friction and frictionless conditions. An increase in the drawbead height, with the same sheet width, increases the value of the COF

Recent Developments and Trends in the Friction Testing for Conventional Sheet Metal Forming and Incremental Sheet Forming

Friction is the main phenomenon that has a huge influence on the flow behavior of deformed material in sheet metal forming operations. Sheet metal forming methods are one of the most popular processes of obtaining finished products, especially in aerospace, automobile, and defense industries. Methods of sheet forming are carried out at different temperatures. So, it requires tribological tests that suitably represent the contact phenomena related to the temperature. The knowledge of the friction properties of the sheet is required for the proper design of the conditions of manufacturing processes and tools. This paper summarizes the methods used to describe friction conditions in conventional sheet metal forming and incremental sheet forming that have been developed over a period of time. The following databases have been searched: WebofKowledge, Scopus, Baztool, Bielefield Academic Search Engine, DOAJ Directory of Open Access Journals, eLibrary.ru, FreeFullPdf, GoogleScholar, INGENTA, Polish Scientific Journals Database, ScienceDirect, Springer, WorldCat, WorldWideScience. The English language is selected as the main source of review. However, in a limited scope, databases in Polish and Russian languages are also used. Many methods of friction testing for tribological studies are selected and presented. Some of the methods are observed to have a huge potential in characterizing frictional resistance. The application of these methods and main results have also been provided. Parameters affecting the frictional phenomena and the role of friction have also been explained. The main disadvantages and limitations of the methods of modeling the friction phenomena in specific areas of material to be formed have been discussed. The main findings are as follows—The tribological tests can be classified into direct and indirect measurement tests of the coefficient of friction (COF). In indirect methods of determination, the COF is determined based on measuring other physical quantities. The disadvantage of this type of methods is that they allow the determination of the average COF values, but they do not allow measuring and determining the real friction resistance. In metal forming operations, there exist high local pressures that intensify the effects of adhesion and plowing in the friction resistance. In such conditions, due to the plastic deformation of the material tested, the usage of the formula for the determination of the COF based on the Coulomb friction model is limited. The applicability of the Coulomb friction model to determine the COF is also very limited in the description of contact phenomena in hot SMF due to the high shear of adhesion in total contact resistance

Effect of Computational Parameters on Springback Prediction by Numerical Simulation

Elastic recovery of the material, called springback, is one of the problems in sheet metal forming of drawpieces, especially with a complex shape. The springback can be influenced by various technological, geometrical, and material parameters. In this paper the results of experimental testing and numerical study are presented. The experiments are conducted on DC04 steel sheets, commonly used in the automotive industry. The numerical analysis of V-die air bending tests is carried out with the finite element method (FEM)-based ABAQUS/Standard 2016 program. A quadratic Hill anisotropic yield criterion is compared with an isotropic material described by the von Mises yield criterion. The effect of a number of integration points and integration rules on the springback amount and computation time is also considered. Two integration rules available in ABAQUS: the Gauss’ integration rule and Simpson’s integration rule are considered. The effect of sample orientation according to the sheet rolling direction and friction contact behaviour on the prediction of springback is also analysed. It is observed that the width of the sample bend in the V-bending test influences the stress-state in the cross-section of the sample. Different stress-states in the sample bend of the V-shaped die cause that the sheet undergoes springback in different planes. Friction contact phenomena slightly influences the springback behaviour

Prediction of springback in V-die air bending process by using finite element method

Springback phenomenon affects the dimensional and geometrical accuracy of the bent parts. The prediction of springback is a key problem in sheet metal forming. The aim of this paper is the numerical analysis of the possibility to predict the springback of anisotropic steel sheets. The experiments are conducted on 40 x 100 mm steel sheets. The mechanical properties of the sheet metals have been determined through uniaxial tensile tests of samples cut along three directions with respect to the rolling direction. The numerical model of air V-bending is built in finite element method (FEM) based ABAQUS/Standard 2016.HF2 (Dassault Systemes Simulia Corp., USA) program. The FEM results were verified by experimental investigations. The simulation model has taken into consideration material anisotropy and strain hardening phenomenon. The results of FEM simulations confirmed the ability of numerical prediction of springback amount. It was also found that the directional microstructure of the sheet metal resulted from rolling process affects the elastic-plastic deformation of the sheets through the sample width