A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to inve...A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to investigate this PKM.Based on this method,kinematic,velocity and error models of this manipulator are established respectively.Since3-PRS PKM has been applied successfully in practice and its structure is similar to the 3-P(Qu) RU PKM,corresponding models of a 3-PRS PKM are given and a performance comparison study between them is investigated on workspace,manipulator dexterity,position error and error sensitivity.The comparison results reveal that the 3-P(Qu) RU PKM has the advantage on velocity performance and the disadvantage on accuracy performance.This novel 3-P(Qu) RU PKM is an available selection for a tool head of a hybrid machine tool and the analysis is greatly helpful for the further applications of this manipulator.展开更多
This paper theoretically investigates the effects of stick-slip in rolling contact zone on stress intensity factors(SIFs)for subsurface short cracks.New mathematical models for SIFs including stick-slip ratio are dedu...This paper theoretically investigates the effects of stick-slip in rolling contact zone on stress intensity factors(SIFs)for subsurface short cracks.New mathematical models for SIFs including stick-slip ratio are deduced in two cases.One is a subsurface short crack parallel to surface,and the numerical analysis shows that the value of KⅡincreases with the increase of stick-slip ratio;the other is a subsurface short crack perpendicular to the surface,and the numerical analysis indicates that the positive value of KⅠdecreases with the increase of stick-slip ratio.As △KⅠand △KⅡare necessary to evaluate the fatigue crack propagation rate or fatigue lifetime,the influences of stick-slip ratio on them are then discussed.It is found that the maximum variations of △KⅠand △KⅡare both around 3.0%due to stick-slip ratio variation.展开更多
基金Supported by the National Natural Science Foundation of China(No.51575307,51225503)the Science and Technology Major Project-Advanced NC Machine Tools & Basic Manufacturing Equipments(No.2013ZX04004021,2014ZX04002051)Top-Notch Young Talents Program of China
文摘A novel symmetrical 3-degree-of-freedom(DOF) parallel kinematic manipulator(PKM) is firstly presented,which is named 3-P(Qu) RU.According to the structure feature,a double closed loop vector method is proposed to investigate this PKM.Based on this method,kinematic,velocity and error models of this manipulator are established respectively.Since3-PRS PKM has been applied successfully in practice and its structure is similar to the 3-P(Qu) RU PKM,corresponding models of a 3-PRS PKM are given and a performance comparison study between them is investigated on workspace,manipulator dexterity,position error and error sensitivity.The comparison results reveal that the 3-P(Qu) RU PKM has the advantage on velocity performance and the disadvantage on accuracy performance.This novel 3-P(Qu) RU PKM is an available selection for a tool head of a hybrid machine tool and the analysis is greatly helpful for the further applications of this manipulator.
基金supported by the National Science and Technology Supporting Program(Grant No.2011BAF09B01)
文摘This paper theoretically investigates the effects of stick-slip in rolling contact zone on stress intensity factors(SIFs)for subsurface short cracks.New mathematical models for SIFs including stick-slip ratio are deduced in two cases.One is a subsurface short crack parallel to surface,and the numerical analysis shows that the value of KⅡincreases with the increase of stick-slip ratio;the other is a subsurface short crack perpendicular to the surface,and the numerical analysis indicates that the positive value of KⅠdecreases with the increase of stick-slip ratio.As △KⅠand △KⅡare necessary to evaluate the fatigue crack propagation rate or fatigue lifetime,the influences of stick-slip ratio on them are then discussed.It is found that the maximum variations of △KⅠand △KⅡare both around 3.0%due to stick-slip ratio variation.
