Oblique cutting is a working condition in fully mechanized mining whose function is making it possible for coal shearer to cut coal wall.Coal shearer often exhibit large vibration amplitudes in oblique cutting since t...Oblique cutting is a working condition in fully mechanized mining whose function is making it possible for coal shearer to cut coal wall.Coal shearer often exhibit large vibration amplitudes in oblique cutting since the shearer is forced to be bent.In this study,dynamic behavior in oblique cutting for the coal shearer cutting unit gearbox(SCUG)is investigated experimentally based on National Coal Mining Equipment Laboratory of China.A new long wall mining test set-up consists of a test coal shearer and other auxiliary machines is developed for operating long wall coal mining process.Realistic oblique cutting process is developed,and vibration response will be more accurate since both cutting loads and test machine in this experiment are realistic.A data-acquisition system consisting of sensors,channel conditioner and computer is developed to capture three-dimensional vibratory accelerations.A test matrix which included various combinations of key cutting load parameters is executed under realistic oblique cutting loads within a wide parameter range to establish database.Experimental data is analyzed in time,domain and time-frequency domains for investigating the rules of dynamic behavior for SCUG.Beat vibration phenomenon and the coupling of gear mesh frequencies are found in experiment,resulting in local resonance and reduce fatigue life of SCUG.The influence of cutting load on beat phenomenon and frequency coupling is demonstrated at the end,and some conclusions are obtained.展开更多
This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-...This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-welded joint, is related to the residual particles that contain tungsten in the joint band structure. Post-weld water toughening resulted in the cryogenic intergranular brittleness of the joint, which is related to the non-equilibrium segregation of solute atoms during the post-weld water toughening. Annealing at 55OC for 30rain can effectively inhibit the cryogenic intergranular brittleness of the post- weld water-toughened joint. The yield strength, ultimate tensile strength, and uniform elongation of the annealed joint are approximately 95%, 87%, and 94% of the corresponding data of the base metal.展开更多
基金This paper was supported by the National Basic Research Program of China(2014CB046303).
文摘Oblique cutting is a working condition in fully mechanized mining whose function is making it possible for coal shearer to cut coal wall.Coal shearer often exhibit large vibration amplitudes in oblique cutting since the shearer is forced to be bent.In this study,dynamic behavior in oblique cutting for the coal shearer cutting unit gearbox(SCUG)is investigated experimentally based on National Coal Mining Equipment Laboratory of China.A new long wall mining test set-up consists of a test coal shearer and other auxiliary machines is developed for operating long wall coal mining process.Realistic oblique cutting process is developed,and vibration response will be more accurate since both cutting loads and test machine in this experiment are realistic.A data-acquisition system consisting of sensors,channel conditioner and computer is developed to capture three-dimensional vibratory accelerations.A test matrix which included various combinations of key cutting load parameters is executed under realistic oblique cutting loads within a wide parameter range to establish database.Experimental data is analyzed in time,domain and time-frequency domains for investigating the rules of dynamic behavior for SCUG.Beat vibration phenomenon and the coupling of gear mesh frequencies are found in experiment,resulting in local resonance and reduce fatigue life of SCUG.The influence of cutting load on beat phenomenon and frequency coupling is demonstrated at the end,and some conclusions are obtained.
基金Financial support by State Key Lab of Advanced Welding and Joining,Harbin Institute of Technology
文摘This study investigates the cryogenic tensile properties and fracture behavior of fiction stir welded and post-weld heat-treated joints of 32Mn-7Cr-1Mo-0.3N steel. Cryogenic brittle fracture, which occurred in the as-welded joint, is related to the residual particles that contain tungsten in the joint band structure. Post-weld water toughening resulted in the cryogenic intergranular brittleness of the joint, which is related to the non-equilibrium segregation of solute atoms during the post-weld water toughening. Annealing at 55OC for 30rain can effectively inhibit the cryogenic intergranular brittleness of the post- weld water-toughened joint. The yield strength, ultimate tensile strength, and uniform elongation of the annealed joint are approximately 95%, 87%, and 94% of the corresponding data of the base metal.
