Fringe analysis for automotive applications

Abstract

The capabilities of Ford USA's Computer Aided Holometry (CAH) system for stepped phase interferometry are presented. Holographic test equipment and facilities are briefly reviewed. Fringe analysis algorithms and procedures for practical semi-automated processing of stepped phase interferograms of complex real life structures for quantitative measurement of deformation and shape are discussed. Several automative applications illustrating the fringe analysis technique are presented, including: (1) the use of CAH combined with Finite Element Analysis (FEA) methods to study frictional effects of the thermal insertion of a wrist pin into a connecting rod; (2) a study of engine deformation due to hydraulic loading of the cylinders; and (3) the computation of sound pressure from CAH measured vibration amplitude/phase and shape using the Rayleigh integral and SYSNOISE TM methods. In the past, holometry methods have been used primarily for problem solving in structures that were already in production, often where limited opportunities existed to make expensive modifications to existing tooling. Infrequently holometry was used by knowledgeable engineers to develop optimized components in the prototype stage even without the current CAE methods. The opportunity and challenge of our day is to closely couple CAE (FEM, EFA) methods and experimental methods (CAH, modal, etc.) to optimize structural performance in the upstream product development process where necessary tooling modifications can and will be made.