In traditional plain bearing, bushes are made of metal. In order to improve the properties of the bush, it is necessary to conduct an experiment in which the purpose is to replace metal with ceramic. Because of its hi...In traditional plain bearing, bushes are made of metal. In order to improve the properties of the bush, it is necessary to conduct an experiment in which the purpose is to replace metal with ceramic. Because of its high hardness, long fatigue wear life, excellent corrosion resistance, good self-lubricating and low density, ceramic bush is suitable for plain bearing. In this paper the influence of the inclusion on the fatigue wear strength of the bush are analysed under the action of a external load with the finite element method. All these work may provide proofs for analysing the wearing mechanism and for controlling the effect of the inclusion. When the normal outer load is 6 N/mm, namely P=6 N/mm. The compressive main stress will be formed inside the basic part of the bush, which gathers in the center touching area between the journal and the the bush around the inclusion, most of the units have their own maximum alternate stress σ max, which is smaller than the fatigue limit of the material of bushes σ 0 (σ 0=60 MPa). If there is P=30 N/mm, some units will have σ max approaching the fatigue limit, stress concentration will occur around the inclusion, so will the local plastic deformation. Some special units exceed the fatigue limit of the material. When P=225 N/mm,most of the units will have the σ max, about 50～300 MPa, which surpasses the fatigue limit. At this time micro pitting and cracking on the bush surface can be observed with SEM. When P=350 MPa, the σ max is about 300～900 MPa, the center touching area on the surface of the sample and the units around the inclusion will exceed the fatigue limit generally, the surface of the bush, the serious wear corrosion and big fatigue cracking can be observed.展开更多
In order to analyze the effect of different loading frequencies on the fatigue performance for asphalt mixture,the changing law of asphalt mixture strengths with loading speed was revealed by strength tests under diff...In order to analyze the effect of different loading frequencies on the fatigue performance for asphalt mixture,the changing law of asphalt mixture strengths with loading speed was revealed by strength tests under different loading speeds.Fatigue equations of asphalt mixtures based on the nominal stress ratio and real stress ratio were established using fatigue tests under different loading frequencies.It was revealed that the strength of the asphalt mixture is affected by the loading speed greatly.It was also discovered that the fatigue equation based on the nominal stress ratio will change with the change of the fatigue loading speed.There is no uniqueness.But the fatigue equation based on the real stress ratio doesn't change with the loading frequency.It has the uniqueness.The results indicate the fatigue equation based on the real stress ratio can realize the normalization of the asphalt mixture fatigue equation under different loading frequencies.It can greatly benefit the analysis of the fatigue characteristics under different vehicle speeds for asphalt pavement.展开更多
This work presented the characteristics of two gear teeth finishing methods, due to the properties of gear teeth surface layer obtained at the tooth working depth. These methods are: 1) the teeth carburization, harden...This work presented the characteristics of two gear teeth finishing methods, due to the properties of gear teeth surface layer obtained at the tooth working depth. These methods are: 1) the teeth carburization, hardening to a hardness of HRC 60-62 and then grinding, 2) the soft gear shaving as the final mechanical treatment and then carburizing and hardening to the hardness of HRC60-62. This work included the test results of the contact fatigue strength carried out on the circulating power system. The Wohler curves were plotted due to the obtained results, as the basis for the practical evaluation of the considered gear finishing methods. The parameters like volume distribution of the voids, content of the retained austenite, compressive residual stress value, but also the results of contact fatigue strength tests, are more favorable for the teeth shaving method than for the teeth grinding method.展开更多
The pinion bracket-assembly(PBA) is a major part of three gorges project(TGP) ship lift drive system. The static strength,fatigue strength and stress distribution of hinge pin of PBA were analyzed by ANSYS, and the st...The pinion bracket-assembly(PBA) is a major part of three gorges project(TGP) ship lift drive system. The static strength,fatigue strength and stress distribution of hinge pin of PBA were analyzed by ANSYS, and the structure of PBA was optimized. The results show that after the optimization, the maximum comprehensive stress is 259.59 MPa, the maximum fatigue cumulative damage of weld joints is 0.94 and the maximum vertical deformation of hinge pin is 0.14 mm. The elastic deformation, hydropneumatic spring cylinder(HSC) load response and the vibration characteristics of PBA were studied by the bearing test when PBA bore the load caused by different water level errors. The results indicate that when the water level of ship chamber ranges from 3.4 m to 3.6 m,the vertical elastic deformation of the pinion shaft is between-8.58 and 10.50 mm. When upward outage-load(1580 k N) is imposed by the test-rack, the vertical elastic deformation of the pinion shaft is 13.42 and 14.07 mm and HSC load response is 795.80-800.80 k N. In the process of imposing load on the pinion by the test-rack, the maximum vibration amplitude and acceleration of PBA internal components are 0.37° and 2.67 rad/s2, respectively; the maximum impact on the pin caused by vibration is 19.89 k N; the pinion shaft vertical displacement and HSC load response do not fluctuate. There is a great difference between the frequency of meshing force of the pinion and the rack(1.06 Hz) and first-order natural frequency of PBA(8.41 Hz), thus PBA will not resonate.From all above, PBA meets the static strength and fatigue strength requirements. The vibration of PBA internal components has no effect on the vertical displacement of the pinion shaft, HSC load response and smooth operation of PBA. There is a liner relationship in the ratio of 2:1 between the thrust imposed by the test-rack and HSC load, thus HSC can limit the load imposed on the pinion.展开更多
文摘In traditional plain bearing, bushes are made of metal. In order to improve the properties of the bush, it is necessary to conduct an experiment in which the purpose is to replace metal with ceramic. Because of its high hardness, long fatigue wear life, excellent corrosion resistance, good self-lubricating and low density, ceramic bush is suitable for plain bearing. In this paper the influence of the inclusion on the fatigue wear strength of the bush are analysed under the action of a external load with the finite element method. All these work may provide proofs for analysing the wearing mechanism and for controlling the effect of the inclusion. When the normal outer load is 6 N/mm, namely P=6 N/mm. The compressive main stress will be formed inside the basic part of the bush, which gathers in the center touching area between the journal and the the bush around the inclusion, most of the units have their own maximum alternate stress σ max, which is smaller than the fatigue limit of the material of bushes σ 0 (σ 0=60 MPa). If there is P=30 N/mm, some units will have σ max approaching the fatigue limit, stress concentration will occur around the inclusion, so will the local plastic deformation. Some special units exceed the fatigue limit of the material. When P=225 N/mm,most of the units will have the σ max, about 50～300 MPa, which surpasses the fatigue limit. At this time micro pitting and cracking on the bush surface can be observed with SEM. When P=350 MPa, the σ max is about 300～900 MPa, the center touching area on the surface of the sample and the units around the inclusion will exceed the fatigue limit generally, the surface of the bush, the serious wear corrosion and big fatigue cracking can be observed.
基金Projects(51208066,51038002)supported by the National Natural Science Foundation of ChinaProject(20114316120001)supported by Specialized Research Fund for the Doctoral Program of Higher Education,China+5 种基金Project(2012-319-825-150)supported by Application and Basic Research Projects of Ministry of Transport ChinaProject(2013K28)supported by Transportation Science and Technology Plan Projects of Henan Province,ChinaProject(201102)supported by Transportation Science and Technology Plan Projects of Hunan Province,ChinaProject(YB2012B031)supported by Funding Projects of Hunan Provincial Outstanding Doctorate Dissertation,ChinaProject(2014gxjgclkf-002)supported by Open Fund of Key Laboratory of Road Structure and Material of Guangxi Province ChinaProject(kfj120101)supported by Open Fund of the Key Laboratory of Highway Engineering(Changsha University of Science and Technology),China
文摘In order to analyze the effect of different loading frequencies on the fatigue performance for asphalt mixture,the changing law of asphalt mixture strengths with loading speed was revealed by strength tests under different loading speeds.Fatigue equations of asphalt mixtures based on the nominal stress ratio and real stress ratio were established using fatigue tests under different loading frequencies.It was revealed that the strength of the asphalt mixture is affected by the loading speed greatly.It was also discovered that the fatigue equation based on the nominal stress ratio will change with the change of the fatigue loading speed.There is no uniqueness.But the fatigue equation based on the real stress ratio doesn't change with the loading frequency.It has the uniqueness.The results indicate the fatigue equation based on the real stress ratio can realize the normalization of the asphalt mixture fatigue equation under different loading frequencies.It can greatly benefit the analysis of the fatigue characteristics under different vehicle speeds for asphalt pavement.
文摘This work presented the characteristics of two gear teeth finishing methods, due to the properties of gear teeth surface layer obtained at the tooth working depth. These methods are: 1) the teeth carburization, hardening to a hardness of HRC 60-62 and then grinding, 2) the soft gear shaving as the final mechanical treatment and then carburizing and hardening to the hardness of HRC60-62. This work included the test results of the contact fatigue strength carried out on the circulating power system. The Wohler curves were plotted due to the obtained results, as the basis for the practical evaluation of the considered gear finishing methods. The parameters like volume distribution of the voids, content of the retained austenite, compressive residual stress value, but also the results of contact fatigue strength tests, are more favorable for the teeth shaving method than for the teeth grinding method.
基金Project(SPKJ016-06)supported by the Key Research Project of State Power Corporation,ChinaProject(2004AC1O1D31)supported by the Key Scientific Research Project of Hubei Province,ChinaProject(0722018)supported by the China Three Gorges Corporation
文摘The pinion bracket-assembly(PBA) is a major part of three gorges project(TGP) ship lift drive system. The static strength,fatigue strength and stress distribution of hinge pin of PBA were analyzed by ANSYS, and the structure of PBA was optimized. The results show that after the optimization, the maximum comprehensive stress is 259.59 MPa, the maximum fatigue cumulative damage of weld joints is 0.94 and the maximum vertical deformation of hinge pin is 0.14 mm. The elastic deformation, hydropneumatic spring cylinder(HSC) load response and the vibration characteristics of PBA were studied by the bearing test when PBA bore the load caused by different water level errors. The results indicate that when the water level of ship chamber ranges from 3.4 m to 3.6 m,the vertical elastic deformation of the pinion shaft is between-8.58 and 10.50 mm. When upward outage-load(1580 k N) is imposed by the test-rack, the vertical elastic deformation of the pinion shaft is 13.42 and 14.07 mm and HSC load response is 795.80-800.80 k N. In the process of imposing load on the pinion by the test-rack, the maximum vibration amplitude and acceleration of PBA internal components are 0.37° and 2.67 rad/s2, respectively; the maximum impact on the pin caused by vibration is 19.89 k N; the pinion shaft vertical displacement and HSC load response do not fluctuate. There is a great difference between the frequency of meshing force of the pinion and the rack(1.06 Hz) and first-order natural frequency of PBA(8.41 Hz), thus PBA will not resonate.From all above, PBA meets the static strength and fatigue strength requirements. The vibration of PBA internal components has no effect on the vertical displacement of the pinion shaft, HSC load response and smooth operation of PBA. There is a liner relationship in the ratio of 2:1 between the thrust imposed by the test-rack and HSC load, thus HSC can limit the load imposed on the pinion.
