Indian Journal of Science and Technology

Abstract

Background/Objectives: Recently, problems of noise produced in the vehicle body are emerging. The apparatus for discharging exhaust gas produced after combustion should suitably absorb vibration and noise from the engine. Methods/ Statistical Analysis: The workpiece was used AISI 316. Characteristics shown under an internal pressure of 8~12MPa and a die speed of 9~235mm/sec were observed. With an assumption that all external conditions were the same, internal pressure due to forming-oil and speeds of die and punch were controlled. Meshes were generated in a total element number of 9,282. For plastic finite elements analysis, DEFORM 2D as the specialized plasticity code of US was employed. Findings: It was shown to be affected by internal pressures rather than by the speeds of the punch and die. Crease was affirmed to be produced in a stable manner from the minimum internal pressure of 10MPa. The gap between die and crease was shown to be smaller, the higher the pressure. And it was shown to be smaller as the speed was increased. Although formability is improved with an increase in the speeds of the punch and die, produced equivalent stresses were determined to be increased. The equivalent stress produced in the crease did not exhibit a large amount of variation as a function of internal pressure and die speed. However, as the center part of the bellows was approached, smaller equivalent stresses were observed, and while larger stresses were produced, the closer it was to the punch. Similar tendency was also shown for the load acting upon die. Therefore, it appears that speed of punch and acting load should be carefully considered in production of bellows. Application/Improvements: Characteristics of plasticity according to each case were identified, and parameters were secured allowing a comparative analysis with experimental data through future experiments. 
Keywords: Bellows, Finite Elements Analysis (FEA), Forming-Oil Pressure, Hydroforming, Plastic, Punch-Speed