INTEGRATED DESIGN OF STEEL CASTINGS FOR SERVICE PERFORMANCE Richard. A. Hardin 1 , Richard K. Huff 2 and Christoph Beckermann 1 1 Dept. of Mech. and Ind. Eng., 3131 S.C., The University of Iowa, Iowa City, IA 52242, USA 2 Caterpillar Inc., Champaign, IL 61820, USA Keywords: steel casting, porosity, fatigue life, modeling, radiography Abstract An integrated approach is presented for the design of structural components made of steel castings that couples casting simulation with stress and fatigue simulation of the part in service. The casting simulation is used to predict the location, size, and shape of porosity defects in the part. The porosity predictions are then transferred to finite element stress analysis and fatigue analysis codes in order to predict the strength and fatigue life of the part in the presence of porosity. Strength and fatigue measurements on test specimens cast with varying levels of porosity are performed to establish relations between the mechanical properties and the porosity; in particular, it is shown how the elastic modulus and the fatigue notch factor depend on the size and shape of the porosity. An industrial case study is used to validate the present simulation methodology. The case study illustrates that a large pore in a low stressed area of the casting may be far less detrimental than a small amount of microporosity in an area that is subject to high tensile stresses. The proposed integrated approach leads to the design of more reliable castings, tailored inspection standards, and decreased reliance on factors of safety. Introduction Effects of shrinkage discontinuities on the structural performance of carbon and low alloy steel castings are not well understood. There are currently no standard or well-accepted methods of analysis that engineers use to determine the effect of porosity on mechanical performance of steel castings. Similarly, there are no guidelines relating non-destructive testing or non- destructive examination (NDT or NDE) methods, such as radiography, to the performance of cast steel components. Unless design engineers have ample test data and/or a track record of experience for a given part, they request that castings pass specified NDT standards without knowing exactly how this translates to part performance. As a result, integration of casting soundness information into the design of castings is still ad-hoc, based on case-by-case experience. Progress on the topic has not advanced much beyond this point despite great interest for many years [1-8]. Usually, the benefits of design experience and performance data are available only for long-run, mass-produced components. Having such a knowledge-base for all steel castings through computer modeling, will lead to more confidence in casting designs, a more rational use of testing specifications, and better performing castings. Developing such engineering guidelines in a design approach that integrates knowledge about the effects of porosity into casting design, production and NDT is the goal of the present work. The integrated casting simulation/performance analysis and design process envisioned is shown schematically in Figure 1. This process enables simultaneous optimization of the casting process parameters (e.g., riser location) and the component geometry (e.g., section thickness) at an early stage in the product definition. Durability prediction in the presence of porosity is possible if 653 Modeling of Casting, Welding and Advanced Solidification Processes - XI Edited by Charles-André Gandin and Michel Bellet TMS (The Minerals, Metals & Materials Society), 2006