原子力显微镜(Atomic force microscopes,AFM)接触模式下的测量结果因受样本表面倾角和针尖—样本表面间摩擦力的影响而存在较大的测量误差。为避免针尖—表面间的摩擦力对AFM测量试样表面形貌的影响,并能够准确测量表面倾角,提出了一...原子力显微镜(Atomic force microscopes,AFM)接触模式下的测量结果因受样本表面倾角和针尖—样本表面间摩擦力的影响而存在较大的测量误差。为避免针尖—表面间的摩擦力对AFM测量试样表面形貌的影响,并能够准确测量表面倾角,提出了一种新的AFM工作模式——消除倾角和摩擦力影响模式。在这种工作模式中,扫描方向垂直悬臂的长轴方向,通过测量悬臂的竖向和横向偏转而得到针尖所受的竖向和横向力,并计算得到针尖—试样表面间的vander Waals力及试样表面局部倾角,然后结合针尖顶点和扫描器的位置及针尖—试样表面间距可以得到试样表面形貌的测量结果。在上述工作模式下,针尖—试样表面间的摩擦力是可控的,能够避免针尖或试样的损伤。仿真结果证明了这种方法的可行性。展开更多
Vibrations or dither's are features of the PWM servo control system in their steady outputs. On the grounds of analyses and experiments of a PWM pneumatic servo control system, the paper puts forward four varietie...Vibrations or dither's are features of the PWM servo control system in their steady outputs. On the grounds of analyses and experiments of a PWM pneumatic servo control system, the paper puts forward four varieties of PWM modulation methods, and concludes on the relationship between dithers and the different methods, and then discusses the influence of friction to the dithers. Results from experiments regarding the dynamic and static responses on the given system support the theories presented.展开更多
A review of research on hyste-resis and stick-slip is presented in this paper. Devices for investigating friction hysteresis and stick-slip of linear rolling guide ways are introduced,as well as some experiment result...A review of research on hyste-resis and stick-slip is presented in this paper. Devices for investigating friction hysteresis and stick-slip of linear rolling guide ways are introduced,as well as some experiment results and conclusions,and some factors impacting on stick-slip are also exhibited.展开更多
TC4 titanium alloy was friction stir welded using a W-Re pin tool,and the defect-free weld was produced with proper welding parameters.The joint consists of stir zone,heat affected zone and base material.The stir zone...TC4 titanium alloy was friction stir welded using a W-Re pin tool,and the defect-free weld was produced with proper welding parameters.The joint consists of stir zone,heat affected zone and base material.The stir zone is characterized by equiaxed dynamically recrystallized α phases and transformed β phases with fine α+β lamellar microstructure.The microstructure of the heat-affected zone is similar to that of the base material,but there is an increase in the volume fraction of β.Transverse tensile strength of the joint is 92% that of the base material,and the joint is fractured in the stir zone and the fracture surface possesses typical plastic fracture characteristics.The stir zone is the weakest part of the joint,through which the tensile characteristics of the TC4 joint can be explained.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
文摘原子力显微镜(Atomic force microscopes,AFM)接触模式下的测量结果因受样本表面倾角和针尖—样本表面间摩擦力的影响而存在较大的测量误差。为避免针尖—表面间的摩擦力对AFM测量试样表面形貌的影响,并能够准确测量表面倾角,提出了一种新的AFM工作模式——消除倾角和摩擦力影响模式。在这种工作模式中,扫描方向垂直悬臂的长轴方向,通过测量悬臂的竖向和横向偏转而得到针尖所受的竖向和横向力,并计算得到针尖—试样表面间的vander Waals力及试样表面局部倾角,然后结合针尖顶点和扫描器的位置及针尖—试样表面间距可以得到试样表面形貌的测量结果。在上述工作模式下,针尖—试样表面间的摩擦力是可控的,能够避免针尖或试样的损伤。仿真结果证明了这种方法的可行性。
文摘Vibrations or dither's are features of the PWM servo control system in their steady outputs. On the grounds of analyses and experiments of a PWM pneumatic servo control system, the paper puts forward four varieties of PWM modulation methods, and concludes on the relationship between dithers and the different methods, and then discusses the influence of friction to the dithers. Results from experiments regarding the dynamic and static responses on the given system support the theories presented.
文摘A review of research on hyste-resis and stick-slip is presented in this paper. Devices for investigating friction hysteresis and stick-slip of linear rolling guide ways are introduced,as well as some experiment results and conclusions,and some factors impacting on stick-slip are also exhibited.
基金Project(2010CB731704) supported by the National Basic Research Program of ChinaProject supported by the Program of Excellent Team in Harbin Institute of Technology, China
文摘TC4 titanium alloy was friction stir welded using a W-Re pin tool,and the defect-free weld was produced with proper welding parameters.The joint consists of stir zone,heat affected zone and base material.The stir zone is characterized by equiaxed dynamically recrystallized α phases and transformed β phases with fine α+β lamellar microstructure.The microstructure of the heat-affected zone is similar to that of the base material,but there is an increase in the volume fraction of β.Transverse tensile strength of the joint is 92% that of the base material,and the joint is fractured in the stir zone and the fracture surface possesses typical plastic fracture characteristics.The stir zone is the weakest part of the joint,through which the tensile characteristics of the TC4 joint can be explained.
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.
