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Recent developments in a NIST sponsored program on Design, Non-Destructive Evaluation and the Manufacturing Sciences (being conducted at Iowa State and Northwestern Universities) have led to the realization of a new paradigm for the design of safety critical components made by metal casting. The paradigm is based on the simultaneous integration of design for casting, design for fatigue performance and design for inspection. In a concurrent environment, foundry process simulation is used to predict an array of porosity related defects in the subject casting. The probability of detection of these defects is investigated with a radiographic inspection simulation tool (XRSIM). The likelihood that the predicted array of defects will lead to a failure is determined by a fatigue crack growth simulation. When properly utilized, this kind of system gives visibility to casting manufacturing, performance, and inspectability issues during the earliest stages of product definition.

Ryobi Outdoor Products (ROP) in Arizona, one of the subsidiaries of Ryobi Group of companies, developed 26.2cc OHV engine for string trimmers. (2) The outline of the valve train of this engine was presented at the SAE conference at Indianapolis 1996.(3) This paper describes methodologies and theoretical considerations by which such a unique valve train was developed. The theoretical consideration includes how optimize the valve train design to minimize the moving mass as a total system. Methodology for optimizing the design of each component of valve train is also presented. A review of how the theoretical optimization was translated into the final production engine design is given. The experimental effort to optimize cylinder head design to make the overall optimized design theory reality is described.