The Mechanical Properties Of Polyurethane Elastomer Under Static And Dynamic Loading And Nano-sized Conditions

Polyurethane elastomer are widely used in different industrial fields, such as seals, tires, hydraulic hose, vibration absorbers and microelectronic packaging and so on. The large deformation behavior and the stress-strain relation of the material had aroused highly attention in the field of mechanics. In particular, it is very important to describe the constitutive relation of these material by means of experiments.In order to study the mechanical properties of polyurethane elastomer under static and dynamic loading and nano-sized conditions, some experiments were carried out on the PU elastomer(the density and hardness of the specimen respectively are 1.2g/cm3 and Shore A: 60±5). The constitutive relation of the material under static and dynamic loading conditions was obtained, and the main work was as follows:(1) The uniaxial compression experiment were carried out on the PU elastomer, which obtained the mechanical behavior of the material at the strain rate of 10-2/s. The results showed that the slope of curve decreased slowly with increasing strain at 0-0.2 and increased continuously with increasing strain at 0.2-0.6, and the PU elastomer showed a hardening phenomenon, and the inelastic behavior was not occurred during deformation. In order to get a reasonable constitutive equation of the PU elastomer, Neo-Hookean model, Mooney-Rivlin model, Yeoh strain energy function, improved Mooney-Rivlin model, and James-Green-Simpson form which fitting with experimental data were used.(2) In order to get the stress-strain relationship of the PU elastomer under different strain rates(3184.4/s、5159.3/s、7169.9/s), the dynamic compression experiment of the material was done. The results showed that the dynamic mechanical behavior of the material was highly nonlinear, and the material appeared strain rate sensitivity, and the hardening effect was obvious, and the specimen had some damage after the experiment. Through the constitutive equation of the PU elastomer under quasi-static loading conditions, and taking into account the strain rate effect and the material nonlinearity, constitutive equation of the material under dynamic loading conditions was obtained. Then the constitutive equation of PU elastomer under static and dynamic loading was obtained by least square method.(3) Considering the application of PU elastomer in micro-nano field, the nano-indentation experiment with four different strain rates(0.01/s、0.03/s、0.05/s、0.1/s) was done by means of continuous stiffness measurements. The elastic modulus, hardness and unloading stiffness of PU elastomer was obtained by analysing the load-displacement curve, and the results showed that the material appeared strain rate sensitivity.