A new analytical chip formation model is proposed for micro-end-milling operations. The model calculates an instantaneous uncut chip thickness by considering the combination of exact trochoidal trajectory of the tool ...A new analytical chip formation model is proposed for micro-end-milling operations. The model calculates an instantaneous uncut chip thickness by considering the combination of exact trochoidal trajectory of the tool tip and tool run-out, while the simplified circular trajectory and the neglected run-out create negligible change in conventional-scale chip formation models. Newton-Raphson iterative method is employed during the calculation to obtain quadratic convergence. The proposed approach allows the calculation of instantaneous uncut chip thickness to be done accurately and rapidly, and the prediction accuracy of this model is also verified by comparing the simulation results to experimental cutting forces.展开更多
As the most important performance,compliance of shield tunneling machines(STM) is defined as the capability to accommodate the sudden change of the load induced by the variable geological conditions during excavation....As the most important performance,compliance of shield tunneling machines(STM) is defined as the capability to accommodate the sudden change of the load induced by the variable geological conditions during excavation.Owing to the different requirements of the compliant tasks,the existing methods in the robotic field cannot be utilized in the analysis and design of the mechanical system of shield tunneling machines.In this paper,based on the stiffness of the mechanical system and the equivalent contact stiffness of the tunnel face,the tunneling interface-matching index(IMI) is proposed to evaluate the compliance of the machine.The IMI is defined as a metric to describe the coincidence of the stiffness curves of the mechanical system and the tunnel face.Moreover,a tunneling case is investigated in the paper as an example to expound the validation of IMI and the analytical process.In conclusion,the IMI presented here can be served as an appraisement of the capability in conforming to the load fluctuation,and give instructions for the design of the thrust system of shield tunneling machines.展开更多
This paper presents a composite modeling method of the forward dynamics in general planar mechanical system. In the modeling process, the system dynamic model is generated by assembling the model units which are kinem...This paper presents a composite modeling method of the forward dynamics in general planar mechanical system. In the modeling process, the system dynamic model is generated by assembling the model units which are kinematical determinate in planar mechanisms rather than the body/joint units in multi-body system. A state space formulation is employed to model both the unit and system models. The validation and feasibility of the method are illustrated by a case study of a four-bar mechanism. The advantage of this method is that the models are easier to reuse and the system is easier to reconfigure. The formulation reveals the relationship between the topology and dynamics of the planar mechanism to some extent.展开更多
基金supported by National Natural Science Foundation of China (No.50575134)
文摘A new analytical chip formation model is proposed for micro-end-milling operations. The model calculates an instantaneous uncut chip thickness by considering the combination of exact trochoidal trajectory of the tool tip and tool run-out, while the simplified circular trajectory and the neglected run-out create negligible change in conventional-scale chip formation models. Newton-Raphson iterative method is employed during the calculation to obtain quadratic convergence. The proposed approach allows the calculation of instantaneous uncut chip thickness to be done accurately and rapidly, and the prediction accuracy of this model is also verified by comparing the simulation results to experimental cutting forces.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2007CB714003)the National Natural Science Foundation of China (Grant Nos. 51075259 and 50905108)the Program for New Century Excellent Talents in University (Grant No.NCET-10-0579)
文摘As the most important performance,compliance of shield tunneling machines(STM) is defined as the capability to accommodate the sudden change of the load induced by the variable geological conditions during excavation.Owing to the different requirements of the compliant tasks,the existing methods in the robotic field cannot be utilized in the analysis and design of the mechanical system of shield tunneling machines.In this paper,based on the stiffness of the mechanical system and the equivalent contact stiffness of the tunnel face,the tunneling interface-matching index(IMI) is proposed to evaluate the compliance of the machine.The IMI is defined as a metric to describe the coincidence of the stiffness curves of the mechanical system and the tunnel face.Moreover,a tunneling case is investigated in the paper as an example to expound the validation of IMI and the analytical process.In conclusion,the IMI presented here can be served as an appraisement of the capability in conforming to the load fluctuation,and give instructions for the design of the thrust system of shield tunneling machines.
基金the National Natural Science Foundation of China (Grant No. 50605042)the National Basic Research Program of China (973 Program) (Grant No. 2006CB705400)
文摘This paper presents a composite modeling method of the forward dynamics in general planar mechanical system. In the modeling process, the system dynamic model is generated by assembling the model units which are kinematical determinate in planar mechanisms rather than the body/joint units in multi-body system. A state space formulation is employed to model both the unit and system models. The validation and feasibility of the method are illustrated by a case study of a four-bar mechanism. The advantage of this method is that the models are easier to reuse and the system is easier to reconfigure. The formulation reveals the relationship between the topology and dynamics of the planar mechanism to some extent.
