Research On Key Technology Of Short-Time High-Load Inverted Planetary Roller Screw Mechanism

The development of new generation high-performance aerospace major weaponry has promoted the third-generation new inverted planetary roller screw mechanism(IPRSM)transmission technology,which has gradually replaced the second-generation ball screw as an ideal transmission part for integrative electro-mechanical actuator(IEMA)of major equipment in aerospace field.However,IPRSM is still designed by traditional methods,which result in the problems of large volume and heavy weight.The problems limit its application to aerospace tactical weapons that are sensitive to volume and weight.Therefore,considering the urgent demand of aerospace tactical weapons for high-load bearing and lightweight servo transmission mechanism and the short-life high-stress service condition of typical aerospace servo mechanism,we take the new high-performance IPRSM as the object and solve the "redundant" problems of IPRSM used by aerospace tactical weapons.Then we study the relationship between fatigue elastic failure behavior and bearing capacity of the materials near yield strength.Based on the theory,we propose the ultimate limit states lightweight design method for IPRSM and establish ultimate limit states lightweight design,manufacturing,evaluation and verification methods for short-life high-load bearing IPRSM.It provides the theoretical basis and technical support for the ultimate limit states lightweight design of aerospace short-life high-stress servo IPRSM.The main work and results of this thesis are as follows:Condersing the short-life high-stress condition of aerospace servo system,the fatigue elastic failure behavior of typical metal materials used in IPRSM with small plastic deformation is studied,and a damage-coupled cyclic elastoplastic constitutive model is established for engineering applications in near material yield strength area.Using the macro-stress control low-cycle fatigue experiment and the micro-crystal plasticity finite element simulation method,the fatigue elastic failure law of typical metal materials is analyzed,and the micro-mechanism of the material fatigue elastic failure behavior is revealed.By using the image processing method,a prediction model of fatigue elastic failure life dispersion zone of typical metal materials is established,which can show the relationship between fatigue failure behavior and bearing capacity of materials in near yield strength area.It provides a theoretical basis for the allowable yield strength selection of the ultimate limit states and lightweight design method under the short-life high-stress condition.The ultimate limit states design method of short-life high-load bearing IPRSM is proposed based on the relationship between fatigue elastic failure behavior and bearing capacity in near yield strength area.The load distribution law of IPRSM thread is studied and the maximum load of IPRSM thread is obtained,according to the load transfer state of IEMA-IPRSM-part thread and the closed-loop deformation coordination conditions.The near yield strength design criterion of short-life high-stress IPRSM is established based on the relationship between fatigue elastic failure behavior and bearing capacity in near yield strength area.And the precise design criteria of IPRSM parameters are established based on accurate meshing mechanism and interference elimination model.Then the ultimate limit states design method of shortlife high-stress IPRSM is proposed.Finally,the IPRSM design example is completed based on the technical requirements of an aerospace model.Compared with the IPRSM designed by traditional method,the pitch diameter of the IPRSM nut is reduced from50 mm to 37.5mm,and the volume is reduced by about 43%.In order to meet the precise design requirements of IPRSM parameters,and contrapose the manufacturing problem of high-precision nut with large length-diameter ratio that limits the improvement of IPRSM precision,we propose a precision grinding method using parallel axis special-shaped grinding wheel for large length-to-diameter ratio nut of IPRSM.According to the forward solution method,the parallel axis grinding contact model of IPRSM is established,and contact condition equation is obtained.According to the normal profile of the known nut thread and contact condition equation,the concave section of grinding wheel is obtained.Meanwhile,through inverse analysis,the influence on thread accuracy by different approximate methods of grinding wheel profile and the influence of eccentricity on width of thread transition surface is analyzed.The special-shaped grinding wheel profile design in parallel axis precision grinding has been completed.By using the nut designed in Chapter 3,the parallel axis grinding experiment is designed,the grinding process parameters are studied,and the parallel axis grinding and accuracy detection of iprsm nut are completed.It indicates the grinding accuracy meets the requirements of accurate design of nearly full load parameters.In order to comprehensively evaluate the bearing characteristics of IPRSM,a fourlevel performance evaluation and verification method of IPRSM is proposed.Considering the short-life high-stress conditions,a IPRSM fatigue elastic failure life test method and an IEMA envelope test method based on the characteristics of the load spectrum are formed.The IPRSM sample,IEMA prototype and test equipment are developed,and the four-level comprehensive performance evaluation of IPRSM is completed,which verifies the correctness and effectiveness of the ultimate limit states design method of short-time high-stress IPRSM.