Simulation of ultrasonic-vibration drawing using the finite element method (FEM)

In ultrasonic-vibration drawing, wires are drawn while ultrasonic vibration is applied to a drawing die. Prior studies provide experimental proof that ultrasonic-vibration drawing reduces drawing resistance, improves lubrication and prevents wire breakage. In the future, ultrasonic-vibration drawing is expected to contribute to the drawing of difficult-to-draw materials and operations, such as shaped wires, ultrafine wires, and the wire drawing operation in semidry or dry condition. However, a detailed analysis and understanding of the mechanism of improvement is not possible on the basis of conventional experimental observations because the ultrasonic-vibration processing phenomenon occurs at high speed. Therefore, we attempted to understand the processing mechanism of ultrasonic-vibration drawing using the finite element method (FEM). ABAQUS was used for the FEM. Drawing force and stress–strain distributions in drawn wires were analyzed. From these studies, we quantitatively clarified the mechanism of improved drawing characteristics, such as decreased drawing force.     

Fabrication of clean cut surface on high strength steel using a new shaving die design

A shaving process is commonly applied to achieve a smooth cut surface thorough the workpiece thickness and a square cut-edge, also known as a finishing operation. However, this process is rarely successful for high-strength steel sheets, which is a major problem. In the present study, finite element method (FEM) simulation was used to clarify the main causes of this problem by comparing the shaving mechanisms between medium carbon steel grade SPCC (JIS) and high-strength steel grade SPFH 590 (JIS). Results show that in the case of SPFH 590 based on material flow, stress distribution, and strain distribution analyses, the shaved chip was difficult to form by sliding along the punch face. Moreover, the tensile stress generated in the shearing zone was increased and readily generated cracks. The shaving process was developed in the present study by generating the cutting-edge angle and rake radius on the punch. The cutting edge angle was designed to generate high compressive stress in the cutting-edge vicinity and shearing zone, and the rake radius was designed to tear a shaving allowance off and move it along the rake radius instead of moving downward along the punch movement direction, thereby decreasing the tensile stress in the shearing zone. Under these mechanisms, the increases in the generated tensile stress in the shearing zone could be delayed, and cracks could thus be prevented. The effect of the punch geometry on the cut surface characteristics and cutting forces were also investigated. Laboratory experiments were performed to validate the FEM simulation results. Experimental results agreed well with the FEM simulation results. Therefore, a smooth cut surface thorough the workpiece thickness of high-strength steel sheets could be successfully achieved by using the developed shaving process.

     

Investigation of spring-go phenomenon using finite element method

Bending is an application used in the sheet metal forming processes in many industries. One of the main problems of the bending process is the occurrence of spring-back/spring-go. Past research has investigated the spring-back problem. However, the spring-go problem was rarely investigated. In this study, the spring-go phenomenon was investigated using the finite element method (FEM) on the V-bending process. The FEM simulation results clearly and theoretically clarified the spring-go phenomenon on the material flow analysis and stress distribution. The comparison between the spring-back and spring-go phenomena was also clarified.     

Finite element analysis of punch height effect on V-bending angle

Considering the advantages of the V-bending die, the economical set-up time and the fabrication of a wide range of part size and complex shape, the V-bending die is generally used, especially in the Press Brake machine. However, the punch heights in the partial V-bending die affected the bending angle. In this study, the finite element method (FEM) was used to investigate the effects of punch height. The FEM simulation results revealed that the effects of punch height on the bending angle were clearly theoretically clarified based on the material flow analysis and stress distribution. The punch height affected the gap between the workpiece and the die, as well as the reversed bending zone, which resulted in a non-required bending angle. Therefore, applying a suitable punch height created a balance of compensating the gap between the workpiece and the die, and the stress distribution on the bending allowance and the reversed bending zone. This resulted in achieving the required bending angle.     

Finite element analysis on the coined-bead mechanism during the V-bending process

The coined-bead technique is commonly applied to solve the spring-back problem in the V-bending process. However, the coined-bead mechanism on the spring-back/spring-go feature has not been clearly identified yet. In this study, the finite element method (FEM) and laboratory experiments were used to investigate the coined-bead mechanism and its effects on the spring-back/spring-go feature. The features were clearly identified using a stress distribution analysis. The results revealed that the mechanism of the coined-bead technique not only increases the compressive stress on the bending allowance zone, where the spring-back feature decreases, but also increases the reversed bending zone on the leg of the workpiece, where the spring-go feature increases. Therefore, after compensating for the increases in the compressive stress and the reversed bending feature, the amount of spring-back on the bent part was decreased. The FEM simulation bending force and bending angle results were agreed with those from the experimental results.     

Process parameter design of spring-back and spring-go in V-bending process using Taguchi technique

Bent parts of complex shapes with high precision are increasingly required. To achieve a high precision of parts, especially the required bending angle, a suitable design of process parameters is strictly considered. In this study, process parameters of bending angle, material thickness and punch radius were investigated. The finite element method (FEM), in association with the Taguchi and the analysis of variance (ANOVA) techniques, was carried out to investigate the degree of importance of process parameters in V-bending process. The results revealed that the degree of importance of process parameters in V-bending process depended on the spring-back and spring-go. The material thickness has a major influence on the spring-back. In contrast, in the case of spring-go, the bending angle has a major influence and closely followed by the material thickness. In addition to predicting the degree of importance of process parameters by the combination of the FEM simulation, the Taguchi technique, and the ANOVA technique, by facilitating an improvement in the quality of the required bending angle was strictly considered by optimization of these process parameters corresponding with the spring-back and spring-go.     

Application of Taguchi technique to investigation of geometry and position of V-ring indenter in fine-blanking process

One of the special features of the fine-blanking process is the use of the V-ring indenter. The V-ring geometry, namely its angle and height, in addition to its position, affects features of the fine-blanked surface. In this study, the finite element (FE) simulation, the Taguchi technique, and the analysis of variance (ANOVA) techniques were carried out to investigate the degree of importance of V-ring indenter parameters. The results indicated that the height and position of the V-ring indenter have a major influence on the fine-blanking process, followed by the V-ring indenter angle. The combination of the FE-simulation, the Taguchi method, and the ANOVA technique was an effective tool to predict the degree of importance of the V-ring indenter parameters in the fine-blanking process, in addition to facilitating an improvement in the quality of the fine-blanked parts by optimization of these V-ring indenter parameters.     

Finite element analysis of sided coined-bead technique in precision V-bending process

To fabricate the precision V-bent parts, the bending angle, inner bending radius, and outer bending radius are strictly required. These requirements result in a processing difficulty especially for the difficult-to-bend material, such as high-strength steel. In the present study, the finite element method (FEM) and laboratory experiments were used to investigate the precision V-bending process. An innovation of sided coined-bead technique was proposed for preventing the spring-back and spring-go. The conventional coined-bead technique was also investigated. Based on the stress distribution analysis, the results revealed that the mechanism of the precision V-bending process, conventional coined-bead technique, and sided coined-bead technique were clearly identified. In the precision V-bending process, the conventional coined-bead technique could only prevent the spring-back. In contrast, the sided coined-bead could prevent both the spring-back and the spring-go by setting a suitable geometry and position. The FEM simulation results showed a good agreement with the experimental results with reference to the bending forces and bending angles.