The construction efficiency and quality of tunnel boring machines(TBMs)is largely determined by the service life of cutting tools,which is the result of contact loads in the crushed zone between cutter ring and rock.I...The construction efficiency and quality of tunnel boring machines(TBMs)is largely determined by the service life of cutting tools,which is the result of contact loads in the crushed zone between cutter ring and rock.In this paper,a series of rock breaking tests were conducted with a 216 mm diameter disc cutter and concrete samples.Based on the superposition principle,the distribution of contact loads between disc cutter and rock were obtained by using the truncated singular value decomposition(TSVD).The results show that both the peak value and the whole numerical distribution of the radial strains on the cutter ring increase with the increase of the penetration.The distribution curves of the contact loads show an approximate parabola going downwards,which indicates contact loads are more concentrated.The front non-loading area with a ratio from 1.8%to 5.4%shows an increasing trend with the increase of penetration.However,the change of rear non-loading area is not obvious.It is believed that the conclusions have guidance for the study of rock breaking mechanism and manufacturing process of the disc cutter.展开更多
Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh sti...Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh stiffness calculation, which is a crucial parameter for the high-fidelity gear dynamic model. This is partially due to the difficulty of backlash determination and the complexity of multi-tooth contact deformation during the meshing process. In this paper, a new method to calculate the mesh stiffness is proposed including the effects of tooth profile modification and eccentricity error. The time-varying mesh parameters and load distribution of cycloid-pin gear pair are determined based on the unloaded tooth contact analysis （TCA） and the nonlinear Hertzian contact theory, allowing accurate calculations of the contact stiffness of single tooth pair and the torsional stiffness of multi-tooth pairs. A detailed parametric study is presented to demonstrate the influences of tooth profile modification, applied torque and eccentricity error on the torsional mesh stiffness, loaded transmission error, Hertzian contact stiffness and load sharing factor. This model can be applied to further study the lost motion and dynamic characteristics of cycloid speed reducer and assist the optimization of its precision, vibration and noise levels.展开更多
A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The ...A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.展开更多
Frictional wear of inner walls of drill pipe and casing is produced by rotational advance of drill pipe in the casing due to the joint effect of drilling fluid, temperature and contact load during drilling, among whic...Frictional wear of inner walls of drill pipe and casing is produced by rotational advance of drill pipe in the casing due to the joint effect of drilling fluid, temperature and contact load during drilling, among which the main wear is on the drill string. With development of drilling technology, deep well, ultradeep well, high angle well, directional well, extended reach well and horizontal well are taking more and more proportion. Meanwhile, the problem of serious frictional wear between drill pipe and casing are becoming more significant due to long time of drilling, high probability of dogleg severity, high contact normal stress between drill pipe and casing etc. Tool sticking may also occur due to large frictional resistance. Therefore, higher requirements are made on the study of how to predict and prevent the wear of drill pipe and casing during drilling. The residual strength of the worn casing is also studied by analysis of the law of drill pipe＇s effect on the casing wear in this paper.展开更多
An approach for the contact analysis and load distribution of double-envelop hourglass worm gearing is presented, which is based on a 3-D elastic contact finite element method (FEM) model that accommodates the influen...An approach for the contact analysis and load distribution of double-envelop hourglass worm gearing is presented, which is based on a 3-D elastic contact finite element method (FEM) model that accommodates the influence of errors and load. As compared with existing tooth contact analysis model that assumes rigidity for the contacting surfaces, the proposed model provides a more realistic analysis on the contact patterns, the distribution of contact load and transmission errors. It is also capable of exploring the influence of different errors on meshing performances, the contact deformation, the shift of the contact zone and load share among the meshing tooth-pairs under different load.展开更多
Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously....Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously.The maximum shear stress was used to act as the criterion of the bonded strength.This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface.Firstly,the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model.It was found that with the increase in the number of coating layers,the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating.Finally,the increase in the number of layers contributes to the decrement of the stress along the x axis.展开更多
基金Project(51475478)supported by the National Natural Science Foundation of ChinaProject(2013CB035401)supported by the National Basic Research Program of China
文摘The construction efficiency and quality of tunnel boring machines(TBMs)is largely determined by the service life of cutting tools,which is the result of contact loads in the crushed zone between cutter ring and rock.In this paper,a series of rock breaking tests were conducted with a 216 mm diameter disc cutter and concrete samples.Based on the superposition principle,the distribution of contact loads between disc cutter and rock were obtained by using the truncated singular value decomposition(TSVD).The results show that both the peak value and the whole numerical distribution of the radial strains on the cutter ring increase with the increase of the penetration.The distribution curves of the contact loads show an approximate parabola going downwards,which indicates contact loads are more concentrated.The front non-loading area with a ratio from 1.8%to 5.4%shows an increasing trend with the increase of penetration.However,the change of rear non-loading area is not obvious.It is believed that the conclusions have guidance for the study of rock breaking mechanism and manufacturing process of the disc cutter.
基金Project(51575062)supported by the National Natural Science Foundation of ChinaProject(51605049)supported by the National Natural Science Foundation for Young Scholar of ChinaProject(BA2015177)supported by the Science and Technology Achievements Transformation Program of Jiangsu Province of China
文摘Cycloid speed reducers are widely used in many industrial areas due to the advantages of compact size, high reduction ratio and high stiffness. However, currently, there are not many analytical models for the mesh stiffness calculation, which is a crucial parameter for the high-fidelity gear dynamic model. This is partially due to the difficulty of backlash determination and the complexity of multi-tooth contact deformation during the meshing process. In this paper, a new method to calculate the mesh stiffness is proposed including the effects of tooth profile modification and eccentricity error. The time-varying mesh parameters and load distribution of cycloid-pin gear pair are determined based on the unloaded tooth contact analysis （TCA） and the nonlinear Hertzian contact theory, allowing accurate calculations of the contact stiffness of single tooth pair and the torsional stiffness of multi-tooth pairs. A detailed parametric study is presented to demonstrate the influences of tooth profile modification, applied torque and eccentricity error on the torsional mesh stiffness, loaded transmission error, Hertzian contact stiffness and load sharing factor. This model can be applied to further study the lost motion and dynamic characteristics of cycloid speed reducer and assist the optimization of its precision, vibration and noise levels.
文摘A three-dimensional contact model of 1×7 steel strand was established. Contact point was searched by Splitting-pinball algorithm, and Augmented-Lagrangian algorithm was applied for analysis of contact loads. The exerted tensile loads to the model were analyzed using finite element method. After analyzing calculation results, the laws of steel wire stress distribution in axis direction and in its cross-section were found. Friction coefficients were set as 0.10, 0.11, and 0.12, respec- tively, to obtain the influence law of friction coefficient to steel wire stresses. Research result shows that friction coefficient has significant influence on the shear stress of steel wire. Analyzed the calculation results of steel strand with five different lay pitch multiples and got the influence law of lay pitch multiple to the stresses of steel wire in steel strand. The Von Misses stress of steel wire increases following with the increasing of lay pitches nmltiples, but the increment value is not very prominent. The shear stress of steel wire decreases following the increase of lay pitch multiple, and the changing amplitude is large when lay pitch multiple is small. Finally, carried out a steel strand tensile deformation test and the consistency of test results with the calculation results shows that the selected model is reasonable.
文摘Frictional wear of inner walls of drill pipe and casing is produced by rotational advance of drill pipe in the casing due to the joint effect of drilling fluid, temperature and contact load during drilling, among which the main wear is on the drill string. With development of drilling technology, deep well, ultradeep well, high angle well, directional well, extended reach well and horizontal well are taking more and more proportion. Meanwhile, the problem of serious frictional wear between drill pipe and casing are becoming more significant due to long time of drilling, high probability of dogleg severity, high contact normal stress between drill pipe and casing etc. Tool sticking may also occur due to large frictional resistance. Therefore, higher requirements are made on the study of how to predict and prevent the wear of drill pipe and casing during drilling. The residual strength of the worn casing is also studied by analysis of the law of drill pipe＇s effect on the casing wear in this paper.
基金the Doctorate Degree Program Foundation of the Ministry of Education (No. 2000061120)
文摘An approach for the contact analysis and load distribution of double-envelop hourglass worm gearing is presented, which is based on a 3-D elastic contact finite element method (FEM) model that accommodates the influence of errors and load. As compared with existing tooth contact analysis model that assumes rigidity for the contacting surfaces, the proposed model provides a more realistic analysis on the contact patterns, the distribution of contact load and transmission errors. It is also capable of exploring the influence of different errors on meshing performances, the contact deformation, the shift of the contact zone and load share among the meshing tooth-pairs under different load.
基金supported by the National Natural Science Foundation of China (Grant No. 51005102)Postdoctoral Science Foundation of Jiangsu Province (Grant No. 1002028C)+1 种基金Postdoctoral Science Foundation of China (Grant No. 20110491366)the State Key Laboratory of Tribology of Tsinghua University (Grant No. SKLTKF10B04)
文摘Finite element method(FEM) was used to investigate the effect of the number of layers on the bond strength for the brittle coating/substrate materials at contact load condition,which has not been addressed previously.The maximum shear stress was used to act as the criterion of the bonded strength.This paper discussed the relationship between the number of coating layers and the maximum shear stress of the layer/substrate interface.Firstly,the results of the FEM and the Hertz analytical method were compared to verify the accuracy of the FEM model.It was found that with the increase in the number of coating layers,the position of the suddenly changed stress along the z axis is transformed from the interface to the external surface of the coating.Finally,the increase in the number of layers contributes to the decrement of the stress along the x axis.
