Research On Dynamic Mechanical Properties Of Dummy Skin Materials Based On SHPB Testingtechnology

In order to realize the autonomous manufacturing of vehicle crash dummy,the material of making dummy is very important.Dummy skin material is a bionic material that mimics human skin tissue.Studying the mechanical properties of the dummy skin material is of great significance for guiding the production formula and process optimization of the material.At the same time,the mechanical properties of the dummy skin material were studied to establish the constitutive model at the later stage and the parameter setting of the material in the finite element analysis provides basic reliable data.Since the dummy skin material is a strain rate-related material,the static mechanical properties and the dynamic mechanical properties are very different.The equivalence of dynamic mechanical properties is directly related to whether the dummy can truly reflect the dynamic response of the human body under the same test conditions.Therefore,the deep study of the dynamic mechanical behavior of the dummy’s skin is the basis for the collision dummy detection and data processing system.Hopkinson Bar is the study of experimental methods commonly used dynamic mechanical properties of materials.Testing hard materials used by Hopkinson bar is very mature.However,while testing soft materials,there are problems such as weak transmission signal,lateral inertia effect,longitudinal inertia effect,friction effect,unbalanced force of two end faces,and failure to load at constant strain rate.Based on the traditional Hopkinson bar platform,I have developed a Hopkinson bar for testing dummy skin materials.In order to obtain a strong transmission signal,aluminum bars are used instead of conventional steel bars to achieve impedance matching,meanwhile a semiconductor strain gauge with a higher sensitivity is used to detect the strain signal.In order to reduce the effects of frictional and inertial effects and to achieve stress balance,a reasonable material size,increased lubrication,and the use of a solder wire shaper were designed during the test.In order to obtain better quality test signals,this paper describes in detail the sticking of elastic bar strain gauges,the connection of dynamic strain gauge bridges,and the use of semiconductor strain gauges instead of fixed value resistors to make the bridge box.The system was statically calibrated and dynamically calibrated.The difference between two methods was analyzed,and then the quadratic polynomial was used to fit the sensitivity coefficient of the semiconductor strain gauge with low linearity.The experiments were carried on foreign dummy skin materials and homemade dummy skin materials.The results show that both materials have similar stress-strain curves with highly nonlinear.Below 5000s-1 strain rate,the mechanical properties of the two materials are close,and the softening effect and strain hardening effect are relatively flat.As the strain rate increases,the softening effect and strain hardening effect of the two materials gradually increase.The strain hardening effect of homemade dummy skin materials.is more obvious.Then the two materials were fitted using the two-term superelastic Ogden model and the improved viscoelastic ZWT model.Ogden model can’t fit the initial softening part of the stress-strain curve,and the improved ZWT model has better fitting to the two materials.