Papers by Keyword: Drawability

Abstract: This paper deals with the formability of pure titanium sheet in square cup deep drawing. Pure titanium has very excellent corrosion resistance. In the metal forming process, pure titanium has very good ductility in cold forming. The normal anisotropy of pure titanium is very high. Therefore, the property is suitable to the sheet metal forming, such as deep drawing process. However, the most important problem is that the occurrence of seizure becomes remarkable in severe forming operations. Many investigations on the effect of processing conditions on the seizure of titanium were carried out. In the present study, the formability of pure titanium sheet in square cup deep drawing was investigated. For the prevention, pure titanium sheets were treated by heat oxide coating. The fresh and clean titanium is not in direct contact with the die during the forming due to the existence of the oxide layer. The material was pure titanium sheets of the JIS grade 2. The initial thickness of the blank was 0.5 mm in thickness. In the deep drawing process, the sheets were employed and a flat sheet blank is formed into a square by a punch. Forming of sheet by multi-stage deep drawing was tried. Various cups were drawn by exchanging the punch and die. The die was taper without a blankholder in the subsequent stages. The effects of the intermediate annealing and tool shape on the occurrence of seizure in square cup deep drawing were also examined. The square cups were successfully drawn by heat oxide coating. The coating of titanium sheet has sufficient ability in preventing the seizure in multi-stage deep drawing operation. The results of the present study revealed that the pure titanium square cups were successfully formed by using heat oxide coating treatment.

Abstract: Tailored welded blank (TWB) consists of steel sheets of different thicknesses and strength which welded into one sheet to reduce weight and production costs, to increase dimensional accuracy and strength. Since a tailored blank is composed of different sheets of metals having different thicknesses and properties, the forming of tailored blanks then creates a lot of technical problems especially in the scheme of deformation. The objective of this work was to evaluate the drawability of tailored blanks. In order to assess the forming behavior of the tailor-welded blanks under the influence of weld orientations, a finite element and experimental methods were conducted. Three welded specimens with weld lines oriented at an angle of 0°, 90° and 45° with respect to the direction of load were investigated. The finite element result showed in a good agreement with the experimental result. The result of the experiment showed that a welded part was characterized by a higher strength and lower plasticity compared to those of the base material. Hence, the weld influences the strain distribution of the tailor-welded specimens. This phenomenon depends strongly on the direction of the weld against the direction of tensile load. The lowest strains occur in the specimen with a longitudinal weld.

Abstract: Deep drawing involves conversion of flat thin sheet metal blanks into parts of desired shape. In the present investigation, the process parameters of warm forming are compared with those of Hydromechanical deep drawing. Warm deep drawing process of circular blanks in Ironing stage is investigated using a 20 T hydraulic press. Hydro-mechanical deep drawing is a process for producing cup shaped components with the assistance of a pressurized fluid. There is an increase in the drawability of low Carbon steel by increasing the oil gap (gap between punch and die) but to make exactly cylindrical shape, the cup is subjected to ironing in the later part of drawing operation. Thickness distribution which describes the quality of the drawn cup is compared in both warm and Hydromechanical deep drawing using experiments and finite element simulations. Keywords- Warm forming,Hydromechanical, deep drawing, Drawability.

Abstract: Aluminium alloy sheets have poor drawability compared to steel sheets as indicated by the values of the plastic strain ratio or the R value. Because of the textures developed during commercial annealing and cold rolling processes, the R value for aluminium alloys is typically less than 1. Since the R value is heavily influenced by the crystallographic texture in the sheet, processes that develop a favourable texture can be utilised to improve the R value. In this study, a severe plastic deformation process called groove pressing has been used to repeatedly deform sheet specimens of aluminium alloy AA 5052. The R values of groove pressed specimens were experimentally determined. X-ray diffraction scans of the groove pressed specimens were carried out to measure the relative intensities of (111) and (002) peaks in the pattern. The largest increase in the R value was for specimens cut at 90° to the rolling direction and groove pressed to four passes. XRD data indicate that the groove pressing process is capable of introducing a favourable shear texture.

Abstract: The cylindrical cup drawing of 5A90 Aluminum-Lithium alloy sheets at various forming conditions was studied by both the experimental approach and the finite element analysis. The uniaxial tensile tests and forming limit tests of 5A90 Al-Li alloy sheets at various temperatures were first carried out. The tests results were then employed in the finite element simulations to investigate the effects of process parameters, such as forming temperature, holder force, and die corner radius, on the formability of cylindrical cup drawing with 5A90 sheets. In order to validate the finite element analysis, the corresponding deep drawing tests were also carried out. It is shown that the simulation results are in qualitative agreement with the experimental observations. The optimal forming temperature, diameter of blank, holder force, punch radius and die corner radius were then determined for the cylindrical cup drawing of 5A90 sheets, and the limit drawing ratio (LDR) reached 2.4 in the optimal parameter conditions.

Abstract: Deep drawing is one of the most widely used metal forming process to produce sheet metal parts especially in automobile industries. Warm working is the plastic deformation of metal at temperatures below the temperature range for recrystallization and above the room temperature. In this investigation, 1.0mm thick circular specimen of stainless steel AISI 304 were warm deep drawn and the influence of temperature on the deformation behaviour of material and the drawing loads which is required to draw the component was studied. The results show that the warm working has positive effects like reduced drawing load, negligible amount of increase in thinning and thickening of a drawn component when compared to the conventional drawing and also there is no necking or cracking occurs due to the temperature influence.

Abstract: The pure titanium long-cups were formed by preventing the seizing in cold multi-stage deep drawing processes. For the prevention, pure titanium sheets were treated by heating oxide coating. The coating is very effective in preventing the occurrence of seizure and galling. The fresh and clean titanium is not in direct contact with the die during the forming due to the existence of the oxide layer. In multi-stage deep drawing, pure titanium sheets of the JIS grade 2 was employed. Various cups were drawn by exchanging the punch and ringed die. The die was flat in the first stage, and was taped without a blankholder in the subsequent stages. The effects of the coating conditions on the occurrence of seizure in multi-stage deep drawing were examined. It was found that the coating titanium sheet has sufficient ability in preventing the seizure in multi-stage deep drawing processes. The pure titanium long-cups were successfully formed by a multi-stage deep drawing operation in cold.

Abstract: Titanium and its alloys are difficult-to-form materials due to limited slip system and plastic anisotropy. Titanium is also prone to change in color due to oxidation at high temperatures. It is thus advisable to conduct deep drawing of titanium and its alloys at temperatures below 600°C. In this study, the drawability of Ti-6Al-4V sheet is evaluated in respect to the process parameters such as forming temperature, forming speed, and blank holding force at elevated temperatures. It is shown that the limit drawing ratio (LDR) increases with increasing temperature, but varies insignificantly with forming speed. The development of residual stresses in the wall of drawn cups during deformation was evaluated.

Abstract: The present work is focused on the investigation of the role of temperature and punch speed in warm deep drawing of AZ31 magnesium alloy. To this purpose, an experimental campaign, defined using a proper DOE approach, has been performed. The experimental results, in terms of the Limiting Drawing Ratio, have shown that drawability is strongly affected by the process parameters. In particular, Limiting Drawing Ratio exhibits the peak value at 250°C. As far as the effect of punch speed is concerned, it depends on temperature: at 200°C drawability increases with decreasing punch speed whilst a reverse behaviour is observed at 250 and 300°C. The experimental results have been analysed by ANOVA in order to evaluate the effect of the single independent factors and their interactions on the dependent one.