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Cuando un elemento estructural es fabricado con un material compuesto laminado (MCL) y se somete a cambios de temperatura, se generan esfuerzos termicos intralaminares. Los esfuerzos termicos intralaminares se presentan debido a las diferencias en los coeficientes de expansion termica y a las propiedades elasticas de las capas que componen al MCL. Es posible que una combinacion de esfuerzos intralaminares y esfuerzos mecanicos puedan producir fallas por separacion en las capas de los MCL (delaminacion). En este articulo se presenta un modelo analitico con el cual se calculan esfuerzos termicos globales e intralaminares producidos por cambios de temperatura inducidos en MCL metalicos, simetricos y sin restricciones en las fronteras. El modelo es alimentado por datos de deformacion obtenidos por galgas extensometricas colocadas en la frontera del MCL. El modelo puede ser utilizado en la determinacion de esfuerzos intralaminares y globales considerando restricciones o cargas en la frontera, solo si el problema es de esfuerzos planos. El modelo fue desarrollado haciendo una analogia al modelo analitico desarrollado en [1], el cual consiste en calcular esfuerzos intralaminares y globales que se generan por la diferencia entre las constantes elasticas de los materiales que componen un MCL sometido a tension simple. El modelo propuesto se fundamenta en la teoria de la elasticidad lineal, en la teoria clasica de laminas y en el principio de superposicion. Con el modelo y mediante un arreglo de pruebas experimentales, se pueden calcular los coeficientes de expansion termica (CET) de cada una de las capas. Finalmente, se realizaron pruebas experimentales de validacion las cuales mostraron que el modelo propuesto es confiable y consistente. Palabras clave: Esfuerzo Termico, Esfuerzo Intralaminar, Coeficiente de Expansion Termica, Materiales Compuestos.

The origin of an automotive structural mechanical failure can be originated by diverse causes, due for example to the structural geometry, the materials of manufacture, the processes of manufacture and the mechanical loads, that appear during the time of service for the that were designed, among other causes. The determination of the mechanical causes that provoke such failures is not a simple task, so it is recommended to apply systematic methods that allow identifying and characterizing them efficiently. Currently, there are experimental and computational tools, which can be used of an integral way to assess failures, locate them and give them a practical solution. In this article an efficient method is presented, which was used to identify and quantify the causes that originated mechanical structural failures (generated by cracks) in a bus. Through a numerical method, was searched for and found the solution to the problem, which was implemented and evaluated. The method integrates experimental and numerical tools for the analysis of stresses and deformations (photoelasticity and electrical extensometry) required for the study of failures. Static tests (torsion and flexion) and braking, curving and travel tests were carried out, with the purpose of obtaining data of stresses and strains that would allow evaluating the mechanical conditions of the bus. The load conditions of the tests were a Gross Vehicle Weight (PBV) and PBV + 20%. To carry out the road tests, only the information of the edges and potholes was considered, since they turned out to be the events that caused the highest levels of stress. The study was carried out on a prototype bus, which did not present structural mechanical failures. The case study presented in this paper refers to finding the causes and the solution to a problem of a failure by a fissure located on the floor of a bus. Finally, the results obtained show the efficiency of the proposed analysis method as well as the integration of the experimental and numerical tools used, in a systematic and integral way identifying the causes that originated a failure in the structure of the bus. Keywords: Mechanical failures, experimental methods, numerical methods for stress analysis, automotive structures.

The failures, unexpected and catastrophic, are presented in large mechanical systems, specifically, in the electric power generation. The development of new methodologies of analysis and research to evaluate and calculate useful life must be proposed. In this work, an analytical-experimental novel methodology was developed using laws of similarity and models at the scale of prototypes, parts or mechanical components of any system. The methodology developed in the dynamic study of steam turbine blades was applied to calculate their stresses, deformations and the prediction of their useful life in mechanical fatigue conditions. The analytic-experimental and numerical results showed a relative error of less than 3,16% for both models. The new methodology was validated with these results. The use of scale models with the application of similarity laws will be of help in the analysis of failures where due to the size or high costs, real systems cannot be analyzed. Keywords: scale models, experimental analysis, deformations, similarity laws, useful life, mechanical fatigue