This paper theoretically investigates the effects of stick-slip in roiling contact zone on stress intensity factors （SIFs） for sub- surface short cracks. New mathematical models for SIFs including stick-slip ratio a...This paper theoretically investigates the effects of stick-slip in roiling contact zone on stress intensity factors （SIFs） for sub- surface short cracks. New mathematical models for SIFs including stick-slip ratio are deduced in two cases. One is a subsur- face short crack parallel to surface, and the numerical analysis shows that the value of Kn increases 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 KI decreases with the increase of stick-slip ratio. As AKI and AKI are necessary to evaluate the fa- tigue 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 AK1 and AKu are both around 3.0% due to stick-slip ratio variation.展开更多
A free-form lens(FFL)is a special surface that is difficult to be fabricated.FFL are usually fabricated by computer-controlled optical surfacing(CCOS)technique.During CCOS,the material removal amount is determined by ...A free-form lens(FFL)is a special surface that is difficult to be fabricated.FFL are usually fabricated by computer-controlled optical surfacing(CCOS)technique.During CCOS,the material removal amount is determined by the unit removal function(URF)convoluting with the input data――the dwell time.When the removal amount and the URF are known,how to solve the input data involves the special algorithm――deconvolution.Usually,the input data are solved by virtue of low pass filter or iterative methods.However,an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS.In this paper,to solve the input data,a new method that is based on the finite Fourier coefficient is put forward.It can give a continuous and accurate solution for fabricating choice.Several parameters are simulated,which influ-ence the process of CCOS,and evaluating on the effect of the method is also carried out.Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.展开更多
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 roiling contact zone on stress intensity factors （SIFs） for sub- surface short cracks. New mathematical models for SIFs including stick-slip ratio are deduced in two cases. One is a subsur- face short crack parallel to surface, and the numerical analysis shows that the value of Kn increases 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 KI decreases with the increase of stick-slip ratio. As AKI and AKI are necessary to evaluate the fa- tigue 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 AK1 and AKu are both around 3.0% due to stick-slip ratio variation.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.50175062,60508001).
文摘A free-form lens(FFL)is a special surface that is difficult to be fabricated.FFL are usually fabricated by computer-controlled optical surfacing(CCOS)technique.During CCOS,the material removal amount is determined by the unit removal function(URF)convoluting with the input data――the dwell time.When the removal amount and the URF are known,how to solve the input data involves the special algorithm――deconvolution.Usually,the input data are solved by virtue of low pass filter or iterative methods.However,an approximation solution would destroy the machining stability nec-essary to perform precisely CCOS.In this paper,to solve the input data,a new method that is based on the finite Fourier coefficient is put forward.It can give a continuous and accurate solution for fabricating choice.Several parameters are simulated,which influ-ence the process of CCOS,and evaluating on the effect of the method is also carried out.Experimental results verify that this method is suitable for guiding the manufacturing of high precision FFL.
