The Fitting Of The Constitutive Relationship Of Pmmaand Fea Research Based On Tensile Tests

PMMA is being widely used in many fields because of its excellent physicalproperties, chemical properties and mechanical properties. Among these properties,the most important are its mechanical properties which mainly determine theappropriate application of PMMA. As a typical visco-elastic material, PMMAspecimen is easily affected by the external environments such as temperature and testspeed. The type of stress-strain curve will change as the temperature and test speedchange. That means we have to know about the fracture rules and behaviors ofPMMA, its reaction to applying load, and its reliance on temperature and time,before we start to design and use it on the given conditions.In this paper, uniaxial and quasi-static tensile tests of PMMA were operated onZwick/Z010testing machine at four temperature levels from293K~353K and fivestrain rate levels from0.0003/s to0.009/s. And then the experimental results wereanalyzed in two different ways. In one way the condition of temperature was fixedwhile the condition of strain rate was fixed in the other way. Through the time-temperature equivalence principles we got the logarithm shift factor of yield stresslgaT. At the end of this part, we illustrated the differences between brittle break andductile break.We selected two constitutive equation models to fit the experimental results.Under the condition of T=293K, we used the modified ZWT constitutive model.Under the condition of T=313K and T=333K, we chose the DSGZ constitutive model.First, we determined the parameters of each constitutive model and then fit theexperimental results with Matlab.In the end, the behavior of PMMA lamp-chimney was simulated under thermalstress and under thermal stress coupled with wind pressure with ABAQUS/Standardand ABAQUS/Explicit, based on the above research. We paid much attention to thedistribution of stress and displacement of each surface and the relationship betweenthe stress of dangerous points and external load in a static simulation. Also wefocused on the relationship between the stress, displacement, internal energy, kineticenergy, total energy and time in a dynamic simulation. An effective way to optimizethe strength of lamp-chimney we found was to increase the angle of chamfer.