抄録
Recently, plastic materials have been widely used in automotive industries due to its good chemical and electrical properties with low density. However, plastics easily get damage at elevated temperature. On the other hand, FSW (Friction stir welding) and FSSW (Friction stir spot welding) have been used for welding of aluminum alloys. These processes are well known as low heat input processes. In addition, new surface modification technique called FSP (Friction stir processing) has been also developed. It is possible to refine grain size and remove casting defects with applying FSP. Additionally, FSP has been also applied to fabricating composite material. However, friction stir welding and friction stir processing are not commonly applied to plastics. The aim of this study is to apply friction stirring process to plastic materials. In this paper, in order to improve strength of FSSWed PVC joint, effect of a composite material fabricated at joining part was studied. The joining strength and fracture behavior were investigated in experimentally as well as analytically. Result of cross sectional observation of the joint indicated that the present process was applicable to fabricate a composite material during FSSW at the joining part. The stir zone size increased due to applying the present process. It is considered that using reinforcement induced larger strain and enlarged the stir zone size. Tensile shear failure load of the joint with composite material at the joining part was higher than that of the joint without composite material at the joining part. According to the result of FEM analysis, value of K_<θmax> decreased with increase in the stir zone size. Fabricating the composite material during FSSW can increase the stir zone size and stiffness of the joining part, and results in increase tensile shear failure load of the joint.
