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The problem of predicting the quality of weld is critical to manufacturing. A great deal of data is collected under multiple conditions to predict the quality. The data generated at Daimler Chrysler has been used to develop a model based on grammatical evolution. Grammatical Evolution Technique is based on Genetic Algorithms and generates rules from the data which fit the data. This paper describes the development of a software tool that enables the user to choose input variables such as the metal types of top and bottom layers and their thickness, intensity and speed of laser beam, to generate a three dimensional map showing weld quality. A 3D weld quality surface can be generated in response to any of the two input variables picked from the set of defining input parameters. This tool will enable the user to pick the right set of input conditions to get an optimal weld quality. The tool is developed in Matlab with Graphical User Interface for the ease of operation.

Laser lap welding quality is a non-linear response based on a host of categorical and numeric material and process variables. This paper describes a Grammatical Evolution approach to the structure identification of the laser lap welding process and compares its performance with linear regression and a neuro-fuzzy inference system.

In this paper, a generalized spot weld model is presented for analyzing various performance attributes of spotwelded automotive structures. The spot weld model employs conventional definitions of beam- or nonlinear spring type elements. The relevant global mechanical properties are presented in the form of six pairs of generalized load-displacement relationships with respect to six degrees of freedom. The required generalized load-displacement relationships can be readily derived with assistance of local finite element welding process model along with limited single-weld coupon testing. As result, the effects of actual weld properties, welding-induced residual stress states, etc. can be incorporated for applications in finite element analysis of complex autobody structures. Its applications in conventional stress analysis for durability prediction, and limit load prediction, and crashworthiness simulation are also discussed with a few selected examples.