Research on Mechanical Performance Parameter of Metal Rubber
Metal Rubber is special materials and used in aerospace, especially under extreme conditions. It has characteristics of strong adaptability, corrosion resistance, radiation resistance and designability. In this paper, we have manufactured Metal Rubber components, and done some research on the influence of previous deformation to Metal Rubber material's structure and performance, its characteristic parameters such as Poisson's ratio, Elastic modulus were studied. Research results are basic but essential for finite element analysis of Metal Rubber materials; these results also play an important role of engineering application.
Constants of Metal Rubber Material
Damping materials made of pressing wire, such as Metal Rubber (MR material), “metal-flex”, “spring cushion” etc. are used widely in vibration protection systems. They have high strength and damping, however they are non-linear and anisotropic. To use contemporary finite element software for calculation of vibration insulators made of wire damping material one should know constants of this material. Till this time this problem almost isn’t researched, there is only a few data in linear approximation. A Young modulus for pressure and bending, shear modulus, Poisson ratio, friction force for pressure and for shear, friction coefficient between wire material and steel plate are obtained for MR material made of stainless steel wire for different load directions by static experiment in the present research. An influence of deformation, relative density, wire diameter, pressing force, deformation in other direction on these constants is considered. Peculiarities of pressing wire material deformation process are discussed: a difference of Young modulus for pressure and bending, a stabilization of hysteretic loop for one direction during load in another direction, an energy dissipation coefficient for different load directions. Results of the present research not only allow calculation of vibration isolator made of MR material by finite element software, but give a method for research of other pressing wire damping materials.
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.