Mechanical Properties Test Of Negative Poisson's Ratio Honeycomb Structure And Research On Compliance Control Strategy Of Device

In order to meet the increasingly diverse mechanical performance requirements,structural materials are increasingly being designed,developed and applied in practical engineering.Negative Poisson's ratio materials have been used in aerospace,military,medical and other fields due to their excellent impact resistance,fracture resistance and unique "expansion" effect.In order to meet the needs of different applications,the structural design of such materials is often complex and diverse,and the loads that are required to withstand are often coupled.Therefore,designing the relevant loading device,simulating its actual service conditions,and in-situ testing its mechanical properties is of great significance for the design and analysis of such complex components.The paper firstly introduces system optimization,function upgrade and improvement through functional and structural analysis combined with test requirements.The main methods include: analyzing the overall function and structure of the device,and expounding the functions and structures of the multi-load loading module,multi-physics loading module,in-situ observation module and control module respectively.Combined with the internal structure of the sensor used in the device,a six-dimensional force sensor calibration device was designed,and the influence of gravity on the measurement was analyzed and corrected.Combined with the calibrated sensor force feedback and neural network theory,a calibration method of device coaxiality is proposed.In addition,the problem that the device moving platform coordinate system does not coincide with the fixture coordinate system is calibrated,so that the device can output accurate displacement loading along the specified loading direction.Then according to the design structure and actual loading requirements of the device,an active compliance control strategy based on BP neural network is proposed.The control strategy constructs a relationship model between the output load of the loading device and the loading posture,so the device has a force control function based on the original control.In order to verify the accuracy of the proposed control strategy,a cantilever bending test of the 6061 Al plate specimen was carried out.Tests have shown that the proposed control strategy can accurately load the sample to be tested to the specified load.Based on the above work,this paper carries out experiments and analysis on a negative Poisson's ratio concave honeycomb structure material.Firstly,the main dimensional parameters of such structures,namely the honeycomb size,the reinforced wall inclination,the wall thickness and its elastic modulus,and the Poisson's ratio,are derived by mathematical derivation.In order to further verify the accuracy of the mathematical model,three sets of comparative experiments were carried out to study the relationship between dimensional parameters and mechanical properties,and the results were as follows: the elastic modulus of such structural materials is inversely proportional to the honeycomb size and the reinforced wall inclination angle,The wall thickness is proportional;the absolute value of the Poisson's ratio is inversely proportional to the size of the test piece,and is proportional to the reinforcement wall inclination and wall thickness.Through further analysis,among the three main size parameters,the inclination angle of the reinforcing wall has the greatest influence on the Poisson's ratio of the structure,and the honeycomb thickness has the greatest influence on the elastic modulus.The experimental results are the same as those obtained by the mathematical model constructed,and the accuracy of the test rule is verified.In addition,combined with the proposed active compliance control strategy,the bending moments of 2N·m,4N·m and 6N·m were applied to the test samples respectively,and the cantilever bending load test under the rated bending moment was realized.By collecting and analyzing the overall strain distribution of the sample,it can be seen that for a single hexagonal honeycomb structure,the strain is mainly on the outer wall when subjected to a bending load,and the strain of the reinforcing wall is relatively small.