Archives mensuelles : janvier 2017

A study of the preload force in metal-elastomer torsion springs

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neidhart-springsNeidhart type suspension units composed of metal-elastomer torsion springs can be a good alternative to steel helical springs in applications such as vibration absorbers or vehicle suspension systems. Assembling this type of spring requires initial preload of the elastomeric working elements, which determines their operating properties.The results of experimental tests and numerical simulations concerning the preload of elastomeric working elements in Neidhart type suspension units are presented in the paper. The performed research made it possible to propose a new calculation model for determining the preload force value acting on the elastomeric cylindrical elements applied in this type of suspension unit. The results obtained using the proposed model exhibit good convergence with FEM simulation results within the range of the tested geometrical and material properties.

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Fatigue cracking of high pressure oil tube

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1-s2-0-s2213290213000321-gr1An article about a Case study of failure analysis published in « Case Studies in Engineering Failure Analysis« , July 2013.

A high pressure oil tube with nominal diameter 50.8 mm and nominal thickness 4 mm has prematurely failed with a longitudinal crack. The failure was detected after 11 months of operation. The tube is part of the hydraulic power unit of an off shore oil and gas platform. The maximum designed internal pressure was 20 MPa and the service temperature was 25 °C with no significant variation. In practice, the internal pressure varies from 16 to 20 MPa under operation, and shutdowns rarely occur.

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A Review on Failure Characteristics of Polymer Gear

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gears_imagesPolymer are now widely used as substitute material for steel in low load devices. Its failure differs from gears made of steel, thus it is important to categorize the failures shown by polymer gears. Several previous studies noted that wear detection, microstructure surface condition monitoring, weight loss and temperature detection can be used in detecting failure of polymer gear. This article reviews the failure detection method mentioned above. Other researcher works were studied and their findings were extracted in order to identify the methods they used. The most common method used was wear detection and it was supplemented by other methods such as microstructure surface condition monitoring. Failures shown by polymer can be concluded to be tooth breakage, tooth deformation, material removal and surface fatigue.

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