Papers by Author: Prarop Kritboonyarit

Abstract: With an increasing pressure on automotive weight reduction, the demand on the lighter weight automotive components continues to increase. In recent years, squeeze casting processes have been used with different aluminium alloys to produce high integrity automotive parts. In this study, the indirect squeeze casting processes is adopted to cast a motorcycles component originally produced by a high pressure die casting process using aluminium alloy ADC12. To minimize amount of gas porosity inside squeeze casts, concepts of (1) minimization of ingate velocity along with (2) bottom filling pattern during the die filling, and (3) maximization of intensifications casting pressure are applied. Then parts are casted with both conventional high pressure die casting and indirect squeeze casting processes. Comparative evaluation of mechanical properties was made between HPDC casts and squeeze casts both in as-cast and heat treated conditions. Results from the experiment have shown that squeeze casts can pass the blister test at 490 °C for 2.5 hours. Then, squeeze casts are heat treated by solution treatment at 484 °C for 20 minutes and artificial age at 190 °C for 2.5 hours, respectively. This improves UTS of the heat treated squeeze cast to 254.14 MPa with 1.84% of elongation, while the UTS of as cast condition from both processes is not significantly different.

Abstract: The purpose of the present research is to investigate and improve the quality of car brake booster deformed under drawing processes by using Finite Element (FE) program known as AutoForm. The materials are made from SPC270F with thickness 1.4 mm. and the initial diameter of 280 mm. The brake booster requires totally 9 production processes, including the sheet blanking, in the manufacture. Failure has found in the 4^th draw in which cracking occurs at the bottom of cylinder. The material property assumed to be anisotropic, behaved according to Ludwik’s equation, and deformed rigid-plastic, which followed Hill’s yielding surface. The deformation for Forming Limit Diagram (FLD) was predicted by Keeler equation. Punch and die were assumed to be rigid during simulation. In this work, the process improvement focus mainly on the smallest change in die design which no lubricant required during the drawing processes. From the predicted results, the recommended punch diameter for the 1st draw should be extended to 111.4 mm while the new design for die’s diameter in the 1st draw is as large as 103 mm. However, punch’s height and its radius need to be varied in order to prevent the wrinkle as well. Since there is a little change in the new design while no more lubrication is required during the draw process, its can be improved in quality of finish product, cost reduction in lubricant consuming as well as the machining time to make a new punch.