The coefficients of friction and squeezing of the key blocks comer in the roof structure of underground coalface are key factors to roof structure stability quantitative analysis. In this paper, through the special t...The coefficients of friction and squeezing of the key blocks comer in the roof structure of underground coalface are key factors to roof structure stability quantitative analysis. In this paper, through the special test of three-type corner friction and squeez- ing of real rock specimens, and physical simulation test on the roof key blocks of roof structure as well as the finite element calcula- tion of the corner stress distribution and failure mechanism, the characteristics of friction and squeezing of the roof key blocks comer are revealed. It is found that the friction angle of the roof key blocks corner is the residual friction angle, and the frictional angle of the roof key blocks is 22-32° (average 27°), so the friction coefficient is determined as 0.5. It also found the squeezing strength is less than the uniaxial strength, and the squeezing coefficient of the roof blocks corner is determined as 0.4. Based on the results, the ground control theory can be updated from qualitative analysis to quantitative analysis.展开更多
Corner contact in gear pair causes vibration and noise,which has attracted many attentions.However,teeth errors and deformation make it difficulty to determine the point situated at corner contact and study the mechan...Corner contact in gear pair causes vibration and noise,which has attracted many attentions.However,teeth errors and deformation make it difficulty to determine the point situated at corner contact and study the mechanism of teeth impact friction in the current researches.Based on the mechanism of corner contact,the process of corner contact is divided into two stages of impact and scratch,and the calculation model including gear equivalent error-combined deformation is established along the line of action.According to the distributive law,gear equivalent error is synthesized by base pitch error,normal backlash and tooth profile modification on the line of action.The combined tooth compliance of the first point lying in corner contact before the normal path is inversed along the line of action,on basis of the theory of engagement and the curve of tooth synthetic complianceload-history.Combined secondarily the equivalent error with the combined deflection,the position standard of the point situated at corner contact is probed.Then the impact positions and forces,from the beginning to the end during corner contact before the normal path,are calculated accurately.Due to the above results,the lash model during corner contact is founded,and the impact force and frictional coefficient are quantified.A numerical example is performed and the averaged impact friction coefficient based on the presented calculation method is validated.This research obtains the results which could be referenced to understand the complex mechanism of teeth impact friction and quantitative calculation of the friction force and coefficient,and to gear exact design for tribology.展开更多
为了提高高速钢微细钻头的钻削质量,研究了物理气相沉积(PVD)涂层高速钢微细钻头在高速干式环境下钻削铝合金时的钻削性能。应用PVD离子镀技术在直径0.2 mm的高速钢微细钻头上制备Ti Al Si N、DLC、Ti N和Al Ti N 4种涂层,并通过同时沉...为了提高高速钢微细钻头的钻削质量,研究了物理气相沉积(PVD)涂层高速钢微细钻头在高速干式环境下钻削铝合金时的钻削性能。应用PVD离子镀技术在直径0.2 mm的高速钢微细钻头上制备Ti Al Si N、DLC、Ti N和Al Ti N 4种涂层,并通过同时沉积涂层的高速钢圆盘间接测量得到涂层的显微硬度、厚度和平均摩擦系数。以6061铝合金为被加工零件对涂层的实际加工性能进行了试验测试,得到了已钻取孔的表面形貌、直径和角磨损量。通过VHM-I04显微硬度计在0.49 N下测定,DLC涂层微钻的显微硬度为2 800,摩擦系数为0.05,钻削效果在所有涂层微钻和未涂层微钻中最好。因与高速钢基体结合差,导致Ti Al Si N涂层容易脱落、微钻磨损快,故Ti Al Si N涂层不适合沉积在微钻表面。展开更多
基金This research was financially supported by the National Natural Science Foundation of China (No.50104009) and the Key Scienceand Technology Research Subject of the Ministry of Education of China (No.204183).
文摘The coefficients of friction and squeezing of the key blocks comer in the roof structure of underground coalface are key factors to roof structure stability quantitative analysis. In this paper, through the special test of three-type corner friction and squeez- ing of real rock specimens, and physical simulation test on the roof key blocks of roof structure as well as the finite element calcula- tion of the corner stress distribution and failure mechanism, the characteristics of friction and squeezing of the roof key blocks comer are revealed. It is found that the friction angle of the roof key blocks corner is the residual friction angle, and the frictional angle of the roof key blocks is 22-32° (average 27°), so the friction coefficient is determined as 0.5. It also found the squeezing strength is less than the uniaxial strength, and the squeezing coefficient of the roof blocks corner is determined as 0.4. Based on the results, the ground control theory can be updated from qualitative analysis to quantitative analysis.
基金Supported by National Science Foundation of China(Grant No.51275160)National Science Foundation of China(Grant No.51305462)National Key Basic Research Program of China(973 Program,Grant No.2010CB832700)
文摘Corner contact in gear pair causes vibration and noise,which has attracted many attentions.However,teeth errors and deformation make it difficulty to determine the point situated at corner contact and study the mechanism of teeth impact friction in the current researches.Based on the mechanism of corner contact,the process of corner contact is divided into two stages of impact and scratch,and the calculation model including gear equivalent error-combined deformation is established along the line of action.According to the distributive law,gear equivalent error is synthesized by base pitch error,normal backlash and tooth profile modification on the line of action.The combined tooth compliance of the first point lying in corner contact before the normal path is inversed along the line of action,on basis of the theory of engagement and the curve of tooth synthetic complianceload-history.Combined secondarily the equivalent error with the combined deflection,the position standard of the point situated at corner contact is probed.Then the impact positions and forces,from the beginning to the end during corner contact before the normal path,are calculated accurately.Due to the above results,the lash model during corner contact is founded,and the impact force and frictional coefficient are quantified.A numerical example is performed and the averaged impact friction coefficient based on the presented calculation method is validated.This research obtains the results which could be referenced to understand the complex mechanism of teeth impact friction and quantitative calculation of the friction force and coefficient,and to gear exact design for tribology.
文摘为了提高高速钢微细钻头的钻削质量,研究了物理气相沉积(PVD)涂层高速钢微细钻头在高速干式环境下钻削铝合金时的钻削性能。应用PVD离子镀技术在直径0.2 mm的高速钢微细钻头上制备Ti Al Si N、DLC、Ti N和Al Ti N 4种涂层,并通过同时沉积涂层的高速钢圆盘间接测量得到涂层的显微硬度、厚度和平均摩擦系数。以6061铝合金为被加工零件对涂层的实际加工性能进行了试验测试,得到了已钻取孔的表面形貌、直径和角磨损量。通过VHM-I04显微硬度计在0.49 N下测定,DLC涂层微钻的显微硬度为2 800,摩擦系数为0.05,钻削效果在所有涂层微钻和未涂层微钻中最好。因与高速钢基体结合差,导致Ti Al Si N涂层容易脱落、微钻磨损快,故Ti Al Si N涂层不适合沉积在微钻表面。
