Research On The Key Technique Of Improving Precision In Measurement Of Barycenter

With the strategic missile being long-range and the improvement of the hit ratio of the missile warhead, the size and the mass of the missile warhead becomes smaller, the speed for the missile warhead becomes faster, and the missile warhead is influenced more in flight by the mass property parameters such as the eccentric mass of the missile warhead. So the parameters of the mass property of the missile warhead are demanded more precisely. The precision of the special appliance measured the parameters of the mass property of the missile warhead importantly affects the flying precision and the hit ratio of the missile warhead. So it is important to improve the precision of the special appliance. In all measurement parameters of the mass property, the measurement of the barycenter position is the core. As one of the key technique in the measurement of the barycenter position, the size of the balance edge construction is very important to the precision of the special appliance.Based on analyzing and comparing several measurement methods of barycenter in common use, this article established a simplified model of the balance edge construction, and the balance edge was simplified as the contact model of a cylinder and a plane, then the torque which was needed when the cylinder had been rolled on the plane in the special normal force was studied. Based on the Hertz Contact Theory which the cylinder was only acted by the normal force, the problem that the cylinder was contacted with the plane in the normal force and a little torque was studied. By analyzing and comparing the rolling friction mechanism of two bodies contacted each other, the conclusion that the pressure redistribution in the contact area was the main reason that the torque which impacted on the cylinder had been counteracted was drawn. According to the conclusion, the balance equation of the cylinder in the normal force and the torque was set up. And combining the boundary condition of the pressure in the contact area, the contact pressure was solved. Then by the condition that the cylinder was rolled, the least torque which had made the cylinder roll was given, and the least torque wascalled the rolling resistance torque, and signed as Tf.In fact the rolling resistance torque reflected the least lateral eccentricity of barycenter that the balance edge construction could measure the measured object. So if the selected size of the balance edge made the rolling resistance torque as small as possible, the measurement precision of the parameters of the mass property by the balance edge construction could be improved. By analyzing of the rolling resistance torque, the relationship between the rolling resistance torque 7/and the cylinder radius R, the normal force P was found. According to the relationship and the yield condition of ?the material, the smallest radiug.that the cylinder couldn't occur plastic deformation ifl-the normal force was confirmed, and the smallest radius was the best radius(signed as Ry) of the cylinder in the normal force to the balance edge construction in a special appliance.The factors that affected the rolling resistance torque had been studying in this article. Elastic deformation, surface adhesion, elastic lag and plastic deformation were mainly discussed, and some significative conclusions were made. The best radius in several different normal force and different cylinder length were calculated, and the half-width of the contact area, the rolling resistance torque, the lateral eccentricity of barycenter when the cylinder's radius was the best radius RY were also calculated, and the calculated results were argued. In the last the theory about the rolling resistance torque was used in the special appliance for the mass property of some kind of strategic missile warhead made by ZhengZhou Research Institute of Mechanical Engineering, and the calculated results of the lateral eccentricity of barycenter were matched well with the results measured by the appliance. Based on the analysis and calculation of the practical instance...