Journal Published Online: 10 October 2014
Volume 43, Issue 4

Measuring Stress Fields in Connecting Rods Using Laser Interferometry (ESPI)



Connecting rods often fail when subjected to stresses greater than their yield limits. They are designed to support both compressive (usually more intense) and tractive forces. Engineers have used finite element simulations to create new conrod shapes, but the original design still follows the one developed several decades ago. The validation of the results is usually performed through experimental destructive tests or through field evaluations. Thus, a cheaper, non-destructive tool that could expedite the validation process would benefit test engineers and designers. The stress field of a part might be obtained from several methods, the most common of which is through the use of strain gages. In this work, we evaluate the application of electronic speckle pattern interferometry (ESPI) to measure stresses in conrods. The measurements were performed on the flat surface in the conrod web and the results were compared with those from finite element simulations. The region examined corresponds to the inner portion of the rod body, excluding only its slightly thicker edges. To eliminate or at least reduce the influence of the uncontrollable factors (noise) on the results, an experimental design was developed, based mainly on the concepts of the design of experiments (DOE). The tests were performed with a conventional forged connecting rod submitted to compressive stresses. The measurements of the stress and strain fields obtained by the ESPI technique were in accordance with the simulations, showing that this technique is a useful tool for design engineers, improving the safety of engine applications.

Author Information

Vaz, Bruno
Engineering Specialization Program, EMBRAER S.A., São Paulo, BR
Ferracini, Elcio
Quality & Production System, Thyssenkrupp Metalúrgica Campo Limpo, Paulista, SP, BR
Santos, Auteliano
School of Mechanical Engineering, Univ. of Campinas, São Paulo, BR
Gonçalves, Raquel
School of Agricultural Engineering, Univ. of Campinas, SP, BR
Pages: 14
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Stock #: JTE20120098
ISSN: 0090-3973
DOI: 10.1520/JTE20120098