Joining advanced materials by diffusion bonding

Abstract

265 wJ#»W[ 1 f'~~ A D TOOL '1/////~VW»7q#f/ SHEET Figure 9.14 Reet box forming thinning distribution and evolution during forming. of SPF. This is further complicated by the interaction of the forming membrane and the tool surface, which introduces contact friction to the membrane stress field which can result in forming ceasing at the point of contact. This is illustrated clearly in Figure 9.14 which shows the thickness variation and the influences which affect the thickness variation during the forming of a simple rectangular channel section. While thickness variations cannot be completely eliminated, certain techniques have been developed which can be employed to improve the thickness variations or alternatively ensure that the material in the finished component is dispersed in the optimum manner. These methods involve: • use of lubricant coatings on the tool and forming blank; this permits slippage between the tool and the forming material • use of preforms which are pre-shaped by conventional means with minimal thinning and then formed into the fine detail by SPF • use of variable thickness starting blanks • male or female forming (Figure 9.13)