Papers by Keyword: Extensometer

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Authors: Shou Hui Chen, Zheng Guo
Abstract: As a kind of flexible fabric reinforced composites, the woven membrane materials suffer from the bi-axial tensile loads in the application of the lightweight structures. Therefore, the experiments under bi-axial tensile loads are essential for the acquaintance of the mechanical characters of the membrane materials. This paper has summarized thoroughly the details of the bi-axial tensile tests, especially the in-plane cruciform tests. The aspects include the shape and configuration of the cruciform sample, the practice of the applied stresses and the testing of the strains in the two axial directions. It could be expected to be the reference for the establishment of the testing standard of the bi-axial tensile experiment for the membrane materials.
Authors: Eduard Schenuit, Rainer Bolkart, Thomas Becker, Oliver Spinka
Abstract: Progresses in developments of high resolution digital cameras and processors power as well enable the use of optical systems for axial and biaxial strain measurements. The main benefit of these systems is a contact free measurement on the sample surface without any influence to the sample. The commonly used optical systems based on following markings attached to sample surface which have to be applied before testing. This paper presents an alternative optical measuring system using the speckle-correlation-technique. The laser based method does not need any special sample markings before testing. The speckle correlation in the presented extensometer measures up to two-dimensional surface strains in tensile as well as in compression tests; original gauge lengths down to 1.5 mm are supported.
Authors: Qiu Hong Tian, Li Ping Yan, Tao Yang, Ben Yong Chen
Abstract: Material deformation measurements are divided into two main classes: contact type measurement and non-contact type measurement. The principles of strain gauge contact type extensometers in small range and large range measurement, non-contact video and non-contact laser extensometers are described, respectively. Furthermore, advantages and disadvantages of these extensometers are reviewed. The contact type extensometers provide a high level of measurement accuracy, but the knife edge is easily damaged during the fracture of high stiffness materials; the total deformation process is not measured unless knife edge is not unloaded post-fracture; meanwhile, the reversal phenomenon is accompanied in tensile test. Accordingly, the resolution of the reversal phenomenon is discussed; Non-contact video extensometers may be used up to the material breaking point without damage, even when testing specimens that exhibit whiplash, but marks on specimens deform following specimens deformation in tensile test, and marks are not automatically and accurately tracked; Although, non-contact laser extensometers provide a higher level of measurement accuracy and wide range of application, it is expensive. On the basis of these discussions, a novel materials deformation measurement method based on laser mark automatic tracking is presented. This method has advantages of simple, high accuracy and wide range of application.
Authors: F.C. Cione, J.L. Rossi, A.C. Souza, S. Delijaicov, M.A. Colosio
Abstract: Many engineering specifications, manufacturing procedures, inspection and quality control have begun to require that the residual stress of a particular component be evaluated. This is becoming as commonplace as the demands on the mechanical properties. In the country there are few research laboratories qualified to perform these tests and also found a worrying lack of skilled labor. Studying the formation and distribution of residual stress fields will improve the operational criteria of wheel safety, among other gains. It is known that these residual stress fields could be added to the effects of system load (tare weight plus occupation of vehicle traction, braking and torque combined). The results obtained used drilling method and rosette type strain gages, are convergent with similarity to those obtained using FEA simulation over critical region for global and superficial in principal stresses mode. The relevance of the present study and research on residual stresses meets safety improvements in cars wheel industry.
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