By using multi-grid method, the simultaneous Reynolds, elasticily, film-thickness,rheology, energy and thermal interface temperature equations are solved, and the numerical solution of line-ontact thermal EHL is succe...By using multi-grid method, the simultaneous Reynolds, elasticily, film-thickness,rheology, energy and thermal interface temperature equations are solved, and the numerical solution of line-ontact thermal EHL is successfully obtained and presented in this paper.In addition, the influence of sliding/rolling ratio on the distribution of temperature within the film and on the solid surface. minimum film thickness and traction coefficient are also studied. The results show that the influence of temperature on film thickness is significant and unnegligible, All mentioned above may provide a basis for further investigation of thermal EHL of helical gears.展开更多
The service condition determines the Roiling Contact Fatigue（RCF） failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF t...The service condition determines the Roiling Contact Fatigue（RCF） failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable; it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating＇s resistance of RCF. The effects of service conditions（lubrication states, contact stresses, revolve speed, and slip ratio） on the changing of thermal spray coatings＇ contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings＇ contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.展开更多
Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel fr...Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.展开更多
文摘By using multi-grid method, the simultaneous Reynolds, elasticily, film-thickness,rheology, energy and thermal interface temperature equations are solved, and the numerical solution of line-ontact thermal EHL is successfully obtained and presented in this paper.In addition, the influence of sliding/rolling ratio on the distribution of temperature within the film and on the solid surface. minimum film thickness and traction coefficient are also studied. The results show that the influence of temperature on film thickness is significant and unnegligible, All mentioned above may provide a basis for further investigation of thermal EHL of helical gears.
基金Supported by Distinguished Young Scholars of National Natural Science Foundation of China(Grant No.51125023)National Basic Research Program of China(973program,Grant No.2011CB013405)+1 种基金National Natural Science Foundation of China(Grant Nos.5127552651275105)Fundamental Research Funds for the Central Universities(Grant Nos.HEUCF20130910003,201403017)
文摘The service condition determines the Roiling Contact Fatigue（RCF） failure mechanism and lifetime under ascertain material structure integrity parameter of thermal spray coating. The available literature on the RCF testing of thermal spray coatings under various condition services is considerable; it is generally difficult to synthesize all of the result to obtain a comprehensive understanding of the parameters which has a great effect on a thermal spray coating＇s resistance of RCF. The effects of service conditions（lubrication states, contact stresses, revolve speed, and slip ratio） on the changing of thermal spray coatings＇ contact fatigue lifetime is introduced systematically. The effects of different service condition on RCF failure mechanism of thermal spray coating from the change of material structure integrity are also summarized. Moreover, In order to enhance the RCF performance, the parameter optimal design formula of service condition and material structure integrity is proposed based on the effect of service condition on thermal spray coatings＇ contact fatigue lifetime and RCF failure mechanism. The shortage of available literature and the forecast focus in future researches are discussed based on available research. The explicit result of RCF lifetime law and parameter optimal design formula in term of lubrication states, contact stresses, revolve speed, and slip ratio, is significant to improve the RCF performance on the engineering application.
文摘Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.
