Characterization of the Fracture of an Automobile Drum Brake
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Characterization of the Fracture of an Automobile Drum Brake N. López Perrusquia1 M. A. Doñu1, V. J. Cortez2, D. Sánchez3, F. Vázquez3 1
Instituto Politécnico Nacional. SEPI-ESIME U.P. Adolfo López Mateos, Zacatenco. México.D.F. 07738. México. E-mail: [email protected] 2 Univerisdad Autónoma Metropolitana Unidad Azcapotzalco, Av. San Pablo 180 Azcapotzalco 02200, México .D.F. Área de Ciencia de los materiales. 3 Universidad Politécnica del Valle de México, Av. Mexiquense s/n, esquina Av. Universidad Politécnica, Col. Villa Esmeralda, C.P. 54910, Tultitlán, Estado de México. ABSTRACT In this research we studied the fracture of a cast iron drum for 3.5 ton trucks, and it seeks to determine the causes that led to a series of cracks in different areas of the part of drum brake during the manufacturing process, casting or machining. The work followed the methodology usually used in failure analysis; we used the following analytical techniques: visual inspection, penetrating liquids, fractography, metallography, chemical analysis and mechanical testing of hardness. The analysis of the automotive part surface is divided into four sections which are the flange, track, belt and covers powders which were evaluated by the above techniques to determine the failure of the piece. Metallography analysis in each section of the piece showed different microstructure on gray cast iron; showing that pieces works with different cooling conditions during manufacture, giving a mechanism of failure-prone fragile. Keywords: Fracture, Casting, Microstructure, Optical Metallography, Hardness. INTRODUCTION The failure analysis is a useful tool because it not only seeks to identify the mechanisms that cause breakage or degradation of mechanical faults and equipment but also establishes responsibilities and probably more importantly, to facilitate the taking of corrective measures that prevents recurrence of the failure [1-2]. The life of automotive components depends critically on their properties mechanical, physical and chemical made during the casting. One of the main possible failures is due to impact and wears resistance [3-4]. The two main functions of a drum is the transmission of a considerable mechanical strength and heat dissipation from, this means operating at medium or high temperatures. Many materials can fulfill these functions, however, for reasons of performance, stability, raw material costs and ease of production, gray iron is the material commonly used. Gray irons are used for automotive brake drums have a long lifespan. They have a high thermal coefficient; on the other hand have excellent wear resistance [5-6]. In the case of ferrous, gray iron castings are widely used in the automotive industry, where operating conditions of automotive components subject to wear, abrasion and surface corrosion. The gray iron can be machined easily, even with hardness that provide good wear resistance has great resistance under conditions where the flow of lubricant is insufficient to maintain a lubricating film. It has outstanding prope
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