Theoretical Study On Test Of Young's Modulus Of Elasticity And Poisson's Ratio For Films

Thin films have been found in a wide range of applications in many advancing technologies. With a rapid development of biological materials and electronics,sophisticated characterization of mechanical properties of ultra thin films is in need to be validated in order to achieve a better understanding of mechanics behavior concerned with thin layer structure, to increase the reliability, structural stability and durability of functional thin films. Therefore, a variety of techniques have been employed to measure mechanical properties of thin film materials, but these technologies have some defects in varying degrees, which affect effectiveness of evaluation of its mechanics properties. So, the urgent key scientific and technological problems need to be solved. Therefore, my further investigation involving in this field is a meaningful work.By means of the exact analytical solution of axisymmetric deformation of the circular membrane fixed at its edge under the action of uniformly-distributed loads tactfully, this thesis proposes a new method and system for the Poisson's ratio and Young's modulus of elasticity for thin films, which can be able to simultaneously determine Young's modulus of elasticity ( E )and Poisson's ratio (ν) for free-standing thin films or thin coating films without residual stresses (or pr-tension), It has advantages of simplicity and reliability, and doesn't involve the substrate effect. Moreover, for the problems of hydraulic loading and its control in existing testing technologies for Young's modulus of elasticity ( E )and Poisson's ratio (ν) for thin coating films, this subject presents a set of new technological solutions of loading and control for fluid pressure blister test. Using the loading and control device,we can not only realize the blister test for coating film materials, but also realize the bulge test for free-standing thin films material.Thesis consists of six Chapters and general conclusions:The first Chapter presents the main research content in brief, the overview related existing testing technologies for Young's modulus of elasticity ( E )and Poisson's ratio (ν) for thin coating films of domestic and international research present condition, the characteristic and innovation of this thesis, application value of geometric testing technology.The second Chapter introduces basic theories of geometric testing technology for Young's modulus of elasticity ( E ) and Poisson's ratio (ν) for thin films and theories about bending methods and indentation methods employed in this thesis.The third Chapter presents basic mechanics models of bending methods, indentation methods, bulge testing methods, combining X-ray diffraction and laser curvature methods, the derivations for the measuring formulas, the measured value of Young's modulus of elasticity ( E ) for thin films through these measurement methods deduced by some other scholars.The fourth Chapter mainly represents the domestic and international research present condition of bulge tests, proposes the geometric testing technology for Young's modulus of elasticity ( E ) and Poisson's ratio (ν) for thin films, develops a set of new loading device, and designs testing system. Using the loading and control device,we can not only realize the blister test for coating film materials, but also realize the bulge test for free-standing thin films material.The fifth Chapter mainly presents the advantages of geometric testing technology. In addition, we make some comparisons between the present testing technologies and geometric testing technology.The sixth chapter presents the main conclusions of this thesis and prospects of future research.Our effort on this work for the mechanical characterization of thin film gives birth to a certain theoretical views.