The Analysis Of Superplastic Deformation Flow And The Standard Measurement Of Material Parameters

Since the phenomenon of superplasticity has been found nearly a hundred years of history, national scientists have made widely research and obtained many significant results results in the superplasticmechanism, mechanical properties, forming technology and the manufacturing technology.With the growing development of superplastic precise forming technology , more products are made through the use of superplastic forming process for forming inflatable which are more widely used in aviation ,spacefligh,building,vehicle,electron tand other fields.The tradtional superplastic material of Zn-5%Al has good microstracture and poperties and excellent superplasticity.Using its superplasticity,we can manufacture many parts with complex shapes.And the forming method has been widely used in practice. With more and more molding parts are acturly widely used in many fields,we must have a basic idea about the mechanical performance of Zn-5%Al at constant temperature.According,it has practical significance to research on the mechanics parameters of Zn-5%Al at constant temperature.Zn-5%Al has not only the strain hardering characteristic,but also the strain rate sensitivity characteristic at constant temperature. This is certain different from the traditional ductile materials which are just of their strain hardering characteristic.It determins that there are some different between Zn-5%Al at constant temperature and traditional ductile materials in the mechanical behaviour.The mechanical behaviour of Zn-5%Al is different with the typical under room temperature.So we can't think Zn-5%Al have superplasticity under room temperature.Because of its poor creep-resistance,it can't be widely used in practice.It can only be used in the decorative parts without load.The article uses the superplastic alloy of Zn-5%Al as the test material.Though the tensile test and the theoretical analysis of Zn-5%Al under room temperature to measure and analyse the main mechanical parameters of Zn-5%Al.The dissertation is mainly composed by five chapters which includes the analysis of the test curves,the traditional measurement of material parameters(m,n)and the measured results,the precise measurement of material parameters of Zn-5%Al.The main contents are as follows.1. Introduction.Firstly,introduce the plastic and the superplastic deformation mechanism and mechanical properties.Secondly,review the superplastic material of Zn-5%Al that used in the article.And then we can drive the significance and indicate the article's content. 2. The tradition measurement of material parameters.According to the tradition measurement to the material parameters of strain-rate sensitivity index(m value),strain hardening index(n value) as constants,and analyse the measured results to point out the shortage of the tradition measurements.3. The theory and the test of the precise measurement of the values of m,n.With the material of Zn-5%Al,the uniaxial tensile tests under constant strain rate,constant velocity and constant load,and the stress relaxation test are operated.And the precise results of material parameters are obtained by the presented methods through computer simulation.In this process the material parameters m,n are not constants but variables,and the measured results are different under different deformation paths,and the values under the same deformation path are also different.4. Chapter IV of this paper is on the basis of the second chapter and chapter III ,for superplastic deformation of geometric instability does not directly lead to fracture , but it appears from the new uniform and stable long established process of microscopic deformation analysis, and combined with typical superplastic alloy Zn-5% Al in the super-plastic temperature (340℃) to measure the experimental measurements and the curve of m (??),n (?)and ? (t),to establish the function expression of m (??),n (?)and ? (t). Then put the corresponding function expression substitute into the superplastic deformation of differential constitutive equations, to Solve differential equations by changed parameters of the dynamic rheological equation.5. Sum all the measured results of the article.This article gets the precise measured results of m,n andτthrough the precise measurement of the material parameters of Zn-5%Al . And measure the corresponding function expression substitute into the superplastic deformation to solve differential equations by changed parameters of the dynamic rheological equation.The test data measurement are detailed and credible,so the conclusions deduced from the elemental theory and the results obtained from test data have universal values used for reference.The research can refer to the performance of Zn-5%Al under normal condition and the wide use of Zn-5%Al in practical,and provide the important basis to the research in the area in the future.