Papers by Keyword: Friction Force

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Authors: Bahman Meyghani, Mokhtar Awang, Sattar Emamian
Abstract: High rotational motion from the welding tool generates a significant amount of the heat during friction stir welding (FSW). Basically, during FSW the heat is mostly coming from the frictional force between the tool shoulder and the plates. Therefore, a precise calculation of the friction coefficient can increase the accuracy of the finite element analysis (FEA) of the process. However, researchers have applied constant values, and that causes a gap between the reality and the simulated model especially after the welding plunging step. In this study, a mathematical formulation is proposed in order to calculate the temperature dependent values of the friction coefficient and also to explore the influence of the temperature in the friction coefficient. To solve the governing equations of the process, the MATLAB® software is used. The results indicate that, from 25°C to the AA 6061-T6 melting point (580°C), the values of the friction coefficient fall steadily in a range of 0.207089 to 0.000582. Furthermore, the material shear stress and the material yield stress decrease consistently as the temperature rises. Consequently, the influence of the temperature in the contact input parameters and the material properties are discussed in detail and a good correlation with the published results is achieved.
Authors: Jae Do Kwon, Sang Jin Cho, Yong Tak Bae
Abstract: The aged degradation of material is observed when heat-resisting steel is exposed for long periods of time at high temperatures. In the present study, the degraded 1Cr-0.5Mo steel that is used for long periods of time at high temperature(about 515°C) and artificially reheat-treated materials are prepared. These materials were used to study the effect of aged degradation on fretting fatigue behavior. Through this experiment, it is found that the fretting fatigue strength of reheat-treated 1Cr-0.5Mo steel is approximately 46 percent lower than that of the plain fatigue strength of the same material. Furthermore, the fretting fatigue strength of degraded 1Cr-0.5Mo steel was less than 53 percent of the same material™s plain fatigue strength. The maximum value of fatigue strength difference is observed as 57 percent between the fretting fatigue of degraded material and plain fatigue of reheat-treated material. These results can be used as basic data in a structural integrity evaluation of heat-resisting steel considering aged degradation effects.
Authors: Ho Chang, Yen Chen Chiu, Chou Wei Lan
Abstract: The purpose of the study is to measure the maximum static friction and dynamic friction in the actuation process of pneumatic cylinder after TiO2 nanoparticles are added to grease. The study makes an innovative design of a new measuring equipment of friction force, which can measure the friction force between the piston seal in pneumatic cylinder and the cylinder bore. The friction force of pneumatic cylinder bore directly affects the output dynamic property of pneumatic cylinder motion. Friction force measuring system can measure the change of friction force of pneumatic cylinder bore under the condition with different operating speeds, and can analyze the relationship between friction force of pneumatic cylinder and output dynamic property of pneumatic cylinder. Such a friction force measuring equipment takes pneumatic cylinder as an output of motive force to drive the measurement of pneumatic cylinder, and uses load cell and draw-line encoder to measure the friction force of pneumatic cylinder bore and the motion speed. In the experiment, the friction forces of pneumatic cylinder given with oil and without oil are measured respectively, achieving the friction force property of pneumatic cylinder bore when being lubricated by nanogrease added with nanoparticles of different weight percentages (wt.%). The experimental results show that adding TiO2 nanoparticles to grease can effectively decrease the friction force produced in the actuation process of pneumatic cylinder.
Authors: Wu Zhang, Yi Peng Lan, Feng Ge Zhang
Abstract: In order to eliminate the friction force of linear motor nc machine tool feed system and improve the machining precision, a new Self Magnetic-Suspension Permanent Magnet Linear Synchronous Motor(PMLSM)is putted forward in this paper, which can generate the suspending power by itself. In this paper, the magnetic field distribution is calculated by means of equivalent magnetizing current and Schwarz-christoffel transformation, and is further analyzed and verified by using Finite Element Method. Furthermore, the method of optimizating the length of the primary iron-cored is adopted to design the motor. The experimental results shows that self magnetic suspension -PMLSM can generate thrust and suspending force separately, and the thrust and suspending force are improved by applying optimized method.
Authors: Xing Dong Li, Yan Xia Shan, Chang Hong Guo
Abstract: Computational models of deformation and friction work were established by dividing contact arc between strip and work roll into two sliding regions, two braking regions and one stagnating region. A two dimensional temperature field model of work roll was established by finite difference method according to practical boundary conditions. Simulation results show that with the increase of rolling pass, deformation work reduced while friction work increased, except that deformation and friction works at the last pass were the least. The computed rolling forces and work roll surface temperatures agree well with measured values collected from a hot strip mill.
Authors: Ke Han Su, Ming Yang Cheng, Yu Chen Chang
Abstract: One of the key issues regarding multi-axis contour following tasks in modern high-precision machining applications is how to effectively reduce contour error. Generally, among existing approaches, the Cross-Coupled Control (CCC) structure is widely used in multi-axis contour following tasks to improve contouring accuracy. However, when a servomechanism is operated in reverse or low-speed motions, the inherent friction force and external disturbance effects will degrade the CCC performance. Therefore, to cope with the aforementioned problems, this paper exploits the Karnopp friction model-based compensator and the Virtual Plant Disturbance Compensator (VPDC) to improve tracking performance as well as contouring accuracy. Moreover, an integrated motion control scheme is also developed to further improve contouring performance. The proposed scheme consists of two position loop controllers with velocity command feedforward, a modified CCC, two friction force compensators, and two disturbance compensators. To evaluate the performance of the proposed approach, several free-form contour following experiments have been conducted on an X-Y table driven by two linear motors. Experimental results verify that the proposed approach can significantly enhance contouring performance for free-form contour following tasks.
Authors: Shuho Koseki, Kenichi Inoue, Kazutake Uehara, Hiroshi Usuki, Masahiro Yoshinobu, Ryutaro Tanaka, Masahiro Hagino
Abstract: Ni-based superalloys are typically difficult-to-cut materials. During machining, the cutting forces and temperatures of these superalloys are generally higher than those of other materials. Therefore, the tool life of the coated carbide cutting tools used for superalloy machining is shortened. This study evaluates the damage of the coated end mills during interrupted cutting of alloy 718 and finds the coating properties necessary for improved cutting of Ni-based superalloys. Damage of the PVD-TiN-coated cutting tools was observed by scanning electron microscopy and transmission electron microscopy of the surfaces and cross sections. In addition, friction forces were measured during turning for some coatings, and hardness of the coatings was measured after annealing. Plastic deformation of the coating and crack formation was shown to occur at the coating cross section. In addition, we determined that the major factor for the damage was high friction force between the coating surface and work material at high temperatures. In summary, coatings with stability at high temperatures and low friction forces during machining can reduce the damage of coated cutting tools, thus increasing the tool life.
Authors: De Gong Chang, Li Zeng Zhang, Zhao Dong Liu
Abstract: In this paper, taking the twin tripod sliding universal joint as three-dimensional solid model, adding various kinematic pairs and motion drivers between kinds of components, using multi-body dynamics software ADAMS that is popular at present, carrying out the dynamic simulation, contrast with or without friction force of the coupling’s movement under the action of those forces, such as the force on the slider, ball head, the journal, and so on. Finally, we obtained the movement rules of the couplings under or without those forces and some qualitative theories, which provided theoretical basis and reference for the subsequent design and research for couplings.
Authors: Peng Bo Zhang, Zhi Xiang Yu, Yu Ping Sun, Shi Chun Zhao
Abstract: The shear-type friction damper using aluminum alloy as the friction material were designed and tested under cyclical loading to investigate the effect of the lap gap to the frictional performance. The test results indicated that the dampers with a lap gap could also absorb energy stably with the same hysteretic behavior as a general friction damper; the frictional force of the shear-type friction damper depended not only upon the bolts tension by the high-strength bolts that clamped the sliding steel plate but also strongly upon the scale of lap gap. The lap gap changed in a scale of 0.12mm only, the average sliding force has four times increase at a lower level of bolt tension, and a double effect to increasing sliding force at the higher level of bolt tension.
Authors: Bo Li, Qing Dong Zhang, Xiao Feng Zhang
Abstract: Three-dimensional finite element model of rolling mill with six rolls in a factory is modeled by nonlinear FEM software called ABAQUS. It is a three-dimensional elastic-plastic rolling model. It includes not only elastic-plastic deformation of strip but also the bending of roll system and flattening of rolls. It can describe the changes in friction force between rolls better. Conclusions are as follows. When the driving roll is the backup roll, friction force between the backup roll and the intermediate roll is easy to reach the maximum value, slipping phenomenon is easy to appear. When the driving roll is the intermediate roll, friction force between the intermediate roll and the work roll is easy to reach the maximum value, slipping phenomenon is easy to appear. When the driving roll is the work roll, the changes in frictional force between the rolls is smooth. Slipping phenomenon is not easy to appear.
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