Yuji Kotani

Numerical Simulation and Evaluation of Local Thickness Increment in Ironing by Finite Element Method

Local increases in product sheet thickness effectively contribute to reducing total product weight. Products could be designed efficiently if a designer could predict and control the thickness distribution of formed products. This paper presents a numerical simulation and evaluation of the local thickness increment of products formed during the ironing process. To clarify the mechanism of the local increase of sheet thickness, a 3-D numerical simulation during ironing was performed by the Finite-Element Method. Tool shapes (contact angles with the original materials and contact length of the punch with the material) that primarily affect thickness changes of original materials were evaluated. It was found that the sheet thickness distribution could be controlled if the original material were relatively thick, when appropriate manufacturing conditions could be selected.

Effects of Elastic Behaviour of Dies and Servo Press Machine on Deep Drawing Process

Characteristic features of elastic deformation of dies and presses during deep drawing were measured to examine the effects of elastic deformation of the press and dies on product accuracy. Strains were measured on the press including dies, a slide and a bolster of a servo press. A strain magnitude of 63 ×10-6 was obtained when the slide position was at the lowest point. Two slide motions of the servo press were selected to determine appropriate manufacturing conditions. An elastic deformation analysis of the die structure was then performed by CAD simulation. To find an appropriate die structure model, the vertical displacement of the die structure in the CAD simulation was compared to the experiment results. It was found that the vertical displacement of the die structure was 0.147 [mm] at the top surface of the die when considering elastic deformation of the die structure as well as the bolster of the servo press.

Manufacturing Method of Increasing Hollow Steel Shaft Thickness Using Uniaxial Pressing

In manufacturing car components, the hollow parts manufacturing method is useful for reducing the product weight, especially in drivetrain parts such as long shafts. Long, hollow shafts should have middle portions with large diameters and thin walls and end portions with small diameters and thick walls in order to reduce weight while maintaining pipe strength.Generally, such long shaft parts are manufactured by reducing the end portion of the pipes with the equivalent diameter and desired hollow part thickness for the middle portion of the parts. It is difficult for manufacturers to successfully thicken the pipe wall locally by press forming because pipes buckle easily during the process. Using thick pipe is one way to prevent buckling, but when using thick pipes, we could not reduce weight much. Automotive industries have desired a manufacturing process that can reduce pipes (relatively thin pipes) without buckling.This paper clarifies the relationships among the forming conditions and the thickening ratio (thickness after forming / thickness before forming) in uniaxial press forming by experiments and finite-element simulation. Steel pipes with 39.0mm outer diameter and 7.6mm thickness were used in the experiment. The relationship between the thickening ratio and the forming load that depends on the die shape, lubrication, and slide motion of the press machine was investigated. An appropriate manufacturing condition that could reduce pipes without buckling was obtained. We clarified that the pipe wall thickness could be increased ten percent. The details of material flows in reducing pipes without buckling were discussed using finite-element simulation.

Characteristics of Wall Thickness Increase in Pipe Reduction Process Using Planetary Rolls

In recent years, global warming has become a worldwide problem. The reduction of carbon dioxide emissions is a top priority for many companies in the manufacturing industry. In the automobile industry as well, the reduction of carbon dioxide emissions is one of the most important issues. Technology to reduce the weight of automotive parts improves the fuel economy of automobiles, and is an important technology for reducing carbon dioxide. Also, even if this weight reduction technology is applied to electric automobiles rather than gasoline automobiles, reducing energy consumption remains an important issue. Plastic processing of hollow pipes is one important technology for realizing the weight reduction of automotive parts. Ohashi et al. [1-2] present an example of research on pipe formation in which a process was carried out to enlarge a pipe diameter using a lost core, achieving the suppression of wall thickness reduction and greater pipe expansion than hydroforming. In this study, we investigated a method to increase the wall thickness of a pipe through pipe compression using planetary rolls. The establishment of a technology whereby the wall thickness of a pipe can be controlled without buckling the pipe is an important technology for the weight reduction of products. Using the finite element analysis method, we predicted that it would be possible to increase the compression of an aluminum pipe with a 3mm wall thickness by approximately 20%, and wall thickness by approximately 20% by pressing the hollow pipe with planetary rolls.

A 3-D Forming Prediction Method of Increase of Sheet Thickness during Drawing Process

To lighten total product weights, the local increases in sheet thickness of products effectively contribute to decreasing product weights, when appropriate sheet thickness distribution in product by a designer could be performed by using an accurate prediction method by simulation. The designer only could distribute thick part where needed a large moment inertia of area from the view points of the strength of the section. In the sense of the such optical designing for the variable thickness distribution in the products, we do not need to consider that sheet thickness should be constant in a product. This paper is concerned with a forming prediction during deep drawing process. To clarify the mechanism of increase of sheet thickness, a 3-D forming simulation during deep drawing by finite element method was performed. Effects of tool shapes (contacting angles to the original materials, contacting length of punch with a material) which mainly affects the results on thickness change of original materials were investigated. The thickness distribution of drawn cups was measured in order to compare simulation results obtained by the finite element method. It has been found that controlling sheet thickness distribution was possible if an original material was relatively thick, when in choosing an appropriate manufacturing condition could be selected.

Material Flow Estimation of Deep-Drawn Product by Using Finite-Element Simulation

The approach to total weight reduction has been a key issue for car manufacturers as they cope with more and more stringent requirements for fuel economy. In sheet metal forming, local increases in product-sheet thickness effectively contribute to reducing the total product weight. Products could be designed more efficiently if a designer could predict and control the thickness distribution of formed products. This paper describes a numerical simulation and evaluation of the material flow in local thickness increments of products formed by an ironing process. In order to clarify the mechanism of the local increase in sheet thickness, a 3-D numerical simulation of deep drawing and ironing was performed using finite-element simulation. The effects of various types of finite elements that primarily affect thickness changes in original materials and thickness prediction were investigated. It was found that the sheet-thickness distribution could be predicted if the original material was relatively thick and if an appropriate type of finite element is selected.

Characteristic Features of Thickness Change of Pipe During Die Forming

Recently the growing demand for light weight products with high strength has been increased by the rapid development of automobile and aircraft technology. Also, reduction of carbon dioxide emissions is one of the most important issues also in the automobile industry. The weight reduction technology is important even if applied to electric vehicles rather than gasoline vehicles, as reduction of energy consumption is an important issue. Plastic processing of hollow pipes is an important technology for realizing weight reduction of automobile components. As an example of research into pipe forming there is the research by Ohashi et al. [1-2], who have carried out processing to enlarge pipe diameters using a lost core, which achieved suppressing reduction in wall thickness and greater pipe expansion than hydro forming. The authors investigated into a method of increasing the wall thickness of pipe by press forming. Using the finite element analysis method it was predicted that it is possible to increase the wall thickness of aluminum pipe with 2mm wall thickness by approximately 20% by hollow pipe press forming. Also, it was predicted that it is possible to increase the wall thickness by approximately 30% in places by eccentric pipe wall thickness increase. Also, the effect of the metal die which has a large effect on processing a pipe from a circular cylindrical shape to a rectangular tube shape was investigated.

Effect of Tool Shape on Increases in Sheet Thickness during Drawing and Ironing

Prior knowledge of local increase in sheet metal thickness due to forming of products would contribute to decreasing total product weight by giving the product designer an advance notice of the appropriate sheet metal thickness distribution in a product. A method using simulation to accurately predict such increases would greatly aid the designer in this task. The designer can then distribute thicker parts where a large area moment of inertia is needed from the viewpoint of structural strength in a given section. In terms of optical designing for variable thickness distribution in products, the sheet thickness in a product need not be considered constant. This paper presents the forming prediction during deep drawing. To clarify the mechanism of increase in sheet thickness, a 3-D forming simulation is performed during deep drawing by using the finite element method (FEM). The effects of tool shapes—angle of contact with the original material and the contacting length of the punch with the material—that mainly affect the change in thickness of the original material are investigated. The thickness distribution of drawn cups is measured for comparing the simulation results obtained by FEM with the experimental results. It is shown that controlling the distribution of sheet metal thickness is possible if the original material is relatively thick, and when an appropriate manufacturing method is selected.

Increase Characteristics of Local Wall Thickness of a Pipe during Die Forming

In recent years global warming has become a worldwide problem. Reduction of carbon dioxide emissions is one of the most important issues also in the automobile industry. This weight reduction technology is important even if applied to electric vehicles rather than gasoline vehicles, as reduction of energy consumption is an important issue. Plastic processing of hollow pipes is an important technology for realizing weight reduction of automobile components. As an example of research into pipe forming there is the research by Ohashi et al. [1-2], who have carried out processing to enlarge pipe diameters using a lost core, which achieved suppressing reduction in wall thickness and greater pipe expansion than hydroforming. In this research, a method of increasing the wall thickness of pipe by press forming was investigated. The establishment of technology for controlling the wall thickness of pipe without buckling the pipe is an important technology for weight reduction of products. Using the finite element analysis method it was predicted that it is possible to increase the wall thickness of aluminum pipe with 2mm wall thickness by approximately 20% by hollow pipe press forming. Also, it was predicted that it is possible to increase the wall thickness by approximately 30% in places by eccentric pipe wall thickness increase. Also, the effect of the metal die which has a large effect on processing a pipe from a circular cylindrical shape to a rectangular tube shape was investigated.

Evaluation of Press Formability Using Servo Die Cushion in Deep Drawing

Manufacturing process using servo press machines have been highlighted in car manufacturers and other industries in Japan. It is necessary to establish an appropriate press working conditions for manufacturing highly accurate products with great extra value. Our aim is to investigate into effects of variable BHF (blank holding force) on press formability, comparing to using a conventional press machine. In this study, FEM analyses of deep drawing process using a variable BHF system has been conducted to demonstrate the effectiveness of a servo die cushion on formability. According to experimental results obtained with a servo die cushion, it is found that maximum load subjected to dies was reduced by 11.8 %, when using a servo press with a servo die cushion comparing to a conventional press.