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
Based on elementary group theory, the block pivot methods for solving two-dimensional elastic frictional contact problems are presented in this paper. It is proved that the algorithms converge within a finite number o...Based on elementary group theory, the block pivot methods for solving two-dimensional elastic frictional contact problems are presented in this paper. It is proved that the algorithms converge within a finite number of steps when the friction coefficient is ''relative small''. Unlike most mathematical programming methods for contact problems, the block pivot methods permit multiple exchanges of basic and nonbasic variables.展开更多
The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks...The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks prepared by different recipes were tested. The testing results show that it is feasible for needle-like wollastonite and fibrous sepiolite to take the place of asbestos as the reinforced materials of friction materials.The braking effect of the brake blocks is the best when the ratio of the needle-like wollastonite to the fibrous sepiolite was 1∶6.展开更多
Stellite 720 is a high-carbon Co-Cr-Mo alloy, designed for severe wear/corrosion environments. This article presents a study of the Stellite 720 coating on stainless steel 304 under block-on-ring wear test. The coatin...Stellite 720 is a high-carbon Co-Cr-Mo alloy, designed for severe wear/corrosion environments. This article presents a study of the Stellite 720 coating on stainless steel 304 under block-on-ring wear test. The coating is deposited through a slurry/powder metallurgy sintering process. Micro-hardness indentation test is conducted on the cross section of the coating specimen to investigate the hardness of individual phases of the coating material and the dilution effect of the substrate material on the coating layer. The tribological behavior of the coating under low and high load wear is investigated. The worn surfaces of the coating specimens are analyzed using a Philips XL30S FEG scanning electron micro- scope (SEM) with an EDAX energy dispersive X-ray (EDX) spectroscopy system. The experimental results are discussed to explore the wear mechanisms of the Stellite 720 coating under block-on-ring wear.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The project supported by the National Natural Science Foundation of China
文摘Based on elementary group theory, the block pivot methods for solving two-dimensional elastic frictional contact problems are presented in this paper. It is proved that the algorithms converge within a finite number of steps when the friction coefficient is ''relative small''. Unlike most mathematical programming methods for contact problems, the block pivot methods permit multiple exchanges of basic and nonbasic variables.
文摘The basic technology and properties of the brake blocks made of modified needle-like wollastonite and fibrous sepiolite were intensively researched.The impact strengthes and fixed velocity friction of the brake blocks prepared by different recipes were tested. The testing results show that it is feasible for needle-like wollastonite and fibrous sepiolite to take the place of asbestos as the reinforced materials of friction materials.The braking effect of the brake blocks is the best when the ratio of the needle-like wollastonite to the fibrous sepiolite was 1∶6.
文摘Stellite 720 is a high-carbon Co-Cr-Mo alloy, designed for severe wear/corrosion environments. This article presents a study of the Stellite 720 coating on stainless steel 304 under block-on-ring wear test. The coating is deposited through a slurry/powder metallurgy sintering process. Micro-hardness indentation test is conducted on the cross section of the coating specimen to investigate the hardness of individual phases of the coating material and the dilution effect of the substrate material on the coating layer. The tribological behavior of the coating under low and high load wear is investigated. The worn surfaces of the coating specimens are analyzed using a Philips XL30S FEG scanning electron micro- scope (SEM) with an EDAX energy dispersive X-ray (EDX) spectroscopy system. The experimental results are discussed to explore the wear mechanisms of the Stellite 720 coating under block-on-ring wear.
