Jingee Park

Finite element method study of incremental sheet forming for complex shape and its improvement

Abstract In order to improve the incremental sheet forming process for the product of complex shape (e.g. human face), a combination of both computer-aided manufacturing (CAM) and finite-element modelling (FEM) simulation, is implemented and evaluated from the histories of stress and strain value by means of finite-element analysis. Here, the results, using ABAQUS/Explicit finite-element code, are compared with forming limit curve at fracture in order to predict and improve the forming conditions by changing process variables of tool radius, tool down-step, and friction coefficient according to the orthogonal array of Taguchis method. First, the CAM simulation is used to create cutter location data. This data are then calculated, modified, and exported to the input file format required by ABAQUS through using MATLAB programming. The FEM results are implemented for negative incremental sheet forming and then investigated by experiment.

Plastic Deformation Characteristic of AZ31 Magnesium Alloy Sheet

In recent years, there has been a growth of the manufacture and application of magnesium products because of its small specific gravity as well as its relatively high strength. However, there are so many studies to assure good formability because magnesium sheet alloy is difficult to form. In this study, uniaxial tensile and biaxial tensile tests of AZ31 magnesium sheet alloy with thickness of 1.2mm were performed at room temperature. Uniaxial tensile tests were performed until of engineering strain. Lankford values and stress-strain curve were obtained. Biaxial tensile tests with cruciform specimen were performed until the breakdown of the specimen occurs. The yield loci were calculated by application of plastic work theory. The results are compared with the theoretical predictions based on the Hill and Logan-Hosford model. In this study, Hill`s 1979 yield function for the case of m

A parametric Study in Incremental Forming of Magnesium Alloy Sheet

Using lightweight materials in vehicle manufacturing in order to reduce energy consumption is one of the most effective approach to decrease pollutant emissions. As a lightweight material, magnesium is increasingly employed in automotive parts. However, because of its hexagonal closed-packed(HCP) crystal structure, in which only the basal plane can move, the magnesium alloy sheets show low ductility and formability at room temperature. Thus the press forming of magnesium alloy sheets has been performed at elevated temperature within range of . Here we try the possibility of sheet metal forming at room temperature by adopting incremental forming technique with rotating tool, which is so called as rotational-incremental sheet forming(RISF). In this rotational-incremental sheet forming the spindle tool rotates on the surface of the sheet metal and moves incrementally with small pitch to fit the sheet metal on the desired shape. There are various variables defining the formability of sheet metals in the incremental forming such as speed of spindle, pitch size, lubricants, etc. In this study, we clarified the effects of spindle speed and pitch size upon formability of magnesium alloy sheets at room temperature. In case of 0.2, 0.3 and 0.4mm of pitch size with hemispherical rotating tool of 6.0mm radius, the maximum temperature at contact area between rotating tool and sheet metal were . Also in case of 300, 500, and 700rpm of spindle speed, the maximum temperature at the contact area were .

Plastic Deformation Characteristics Of AZ31 Magnesium Alloy Sheets At Elevated Temperature

Using lightweight materials is the emerging need in order to reduce the vehicle’s energy consumption and pollutant emissions. Being a lightweight material, magnesium alloys are increasingly employed in the fabrication of automotive and electronic parts. Presently, magnesium alloys used in automotive and electronic parts are mainly processed by die casting. The die casting technology allows the manufacturing of parts with complex geometry. However, the mechanical properties of these parts often do not meet the requirements concerning the mechanical properties (e.g. endurance strength and ductility). A promising alternative can be forming process. The parts manufactured by forming could have fine‐grained structure without porosity and improved mechanical properties such as endurance strength and ductility. Because magnesium alloy has low formability resulted form its small slip system at room temperature it is usually formed at elevated temperature. Due to a rapid increase of usage of magnesium sheets in au...

Effect of Processing Conditions on the Deep Drawability of Ti-6Al-4V Sheet at Warm Temperatures

Abstract In the current study, fundamental deep drawing characteristics of Ti-6Al-4V alloy sheets were investigated to establish the effect of processing conditions on large size square deep drawn cups . To accomplish this study, FE-simulations (Abaqus) wereperformed to determine optimum blank size, friction coefficient, the gap between punch and die, etc. The simulated processing parameters were verified experimentally. Based on the FE-simulation results, deep drawing was performed with various blank holding loads and sample sizes. In order to improve the formability of Ti-6Al-4V sheet, various lubricant methods were evaluated. Tensile tests and thickness measurements were conducted on the formed sheets. Processing parameters including blank holding force, lubricants, and optimum blank size, were selected to achieve improved drawing quality. With ×the optimum processing condition, a 200mm 200mm cup was deep drawn successfully. Key Words : Titanium, Ti-6Al-4V Sheet, Deep Drawing, FEM-simulation, Abaqus Code, Lubricant

Evaluation of Pess Formability for Ti-6Al-4V Sheet at Elevated Temperature

Abstract Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only for aerospace parts but also for bio prothesis and motorcycle. However, the database is insufficient in the titanium alloy for press forming process. In this study, the effect of temperature on the forming limit diagram was investigated for Ti-6Al-4V titanium alloy sheet through the Hecker’s punch stretching test at elevated temperature. Experimental results obtained in this study can provide a database for the development of press forming process at elevated temperature of Ti-6Al-4V titanium alloy sheet. From the experimental studies it can be concluded that the formability of Ti-6Al-4V titanium alloy sheet is governed by the ductile failure for the testing temperature. The formability of Ti-6Al-4V titanium alloy sheet at 700℃ increases about 7 times compared with that at room temperature. Key Words