Search

Incremental sheet forming (ISF) is a promising method for forming metal sheets, by which parts can be manufactured without the use of dedicated dies. However, the process has not been widely used for industrial application due to the unsatisfactory service performance of the formed parts. This paper focuses on improving the thickness distribution and mechanical properties (e.g., hardness, yield strength, and tensile strength) through process optimization. The response surface methodology with a Box-Behnken design is used to investigate how different process parameters affect the thickness thinning and mechanical properties. A set of experiments with 15 tests for pyramid-forming process is performed, and three parameters including step-down size, sheet thickness, and tool diameter are considered. The results show that the maximum thinning rate is lower with larger step-down size and larger tools. In addition, compared with the initial sheet, the values of hardness, yield strength, and tensile strength have been increased considerably due to the strain hardening. The present work provides useful guidance in improving the product quality formed by incremental sheet forming. [ABSTRACT FROM AUTHOR]

The forming temperature of cross-wedge rolling (CWR) usually ranges from 950 to 1150 °C, but reducing the forming temperature has some advantages. This paper presents a comprehensive study of warm and hot cross-wedge rolling by using high-strength bolts as a case. Numerical simulation and experimental trials were conducted to make a detailed comparison of warm and hot cross-wedge rolling. Forming quality, microstructure, and mechanical properties of the rolled rods were investigated using scanning electron microscopy (SEM) and tensile testing. The results show that the rolling force and torque of warm cross-wedge rolling (WCWR) are more than three times greater than those of hot cross-wedge rolling (HCWR), and the workpiece rolled by WCWR shows more pit and stacking defects but fewer central cavities. The dispersing spheroidized cementite on ferrite matrix generated in WCWR results in decreased hardness and tensile strength of the rolled rods and a significant increase of elongation, which improves subsequent machinability. [ABSTRACT FROM AUTHOR]