Skidding analysis of angular contact ball bearing subjected to radial load and angular misalignment

Journal of Mechanical Science and Technology - Skidding is a phenomenon that frequently occurs in ball–raceway contact areas of bearings and often leads to their early failure. This paper...     

Optimization of partially crowned roller profiles for tapered roller bearings

The roller profile plays a key role in the overall performance of roller bearings. In traditional profile design for roller bearings, the roller profile was often analyzed in terms of the bearing performance, particularly the fatigue life. However, the bearing dynamic stiffness and fatigue life were seldom considered simultaneously in the design of Tapered roller bearings (TRBs). Among the available roller profiles, the partially crowned roller profile has been acknowledged as one of the best from the viewpoint of the bearing fatigue life and stiffness characteristics. This paper presented a design optimization for the partially crowned roller profile to improve the performance of TRBs. Two profile parameters of rollers employed for TRBs including the central flat length and crown radius were investigated. The optimal design parameters for the roller profile were obtained in consideration of both bearing fatigue life and stiffness. The proposed design approach was useful and applicable for further geometrical optimization, manufacturing, and engineering application of rolling bearings.     

Statistical investigation into the effects of distributed roller diameter error on the fatigue life of tapered roller bearings

This study examined the effect of distributed roller diameter error on the fatigue life of a Tapered roller bearing (TRB). To this end, a comprehensive analysis procedure to perform a statistical analysis of the fatigue life with respect to dimensional error was presented. The roller diameter error was assumed as normally distributed, with a designated mean value and a varying standard deviation. Simulations were conducted to investigate the effects of roller diameter deviation on the fatigue life of the TRB. The numerical results showed that the normally distributed roller diameter error did not necessarily result in a normally distributed bearing fatigue life. The adequate distribution function for the bearing fatigue life with respect to the roller diameter error was explored and found to be dependent on the amount of standard deviation of roller diameter error. The Weibull distribution is appropriate for a small standard deviation, while the gamma distribution and normal distributions are appropriate for large and in-between standard deviations, respectively.

     

A study on the cutting force and chip shrinkage coefficient in high-speed milling of A6061 aluminum alloy

In this paper, finite element (FE) simulation for high-speed milling of aluminum alloy was performed using a ductile fracture model with Mohr–Coulomb criterion proposed by Bai and Wierzbicki (BW). To verify the model, predicted cutting forces were compared to experimental results in the same cutting conditions. Then, further simulations were performed to estimate the cutting forces and chip shrinkage coefficients subjected to different cutting parameters such as cutting speeds, cutting depths, and clearance angles of a cutting tool. The obtained results were also used to determine optimal cutting parameters using the Taguchi method. The analysis of variance (ANOVA) was employed to investigate the influence percentage of each cutting parameter on cutting force and chip shrinkage coefficient. The simulation results showed that inclusion of strain rate in numerical model significantly improved the accuracy of estimated cutting force in comparison to experiment. The optimum values obtained for high-milling process were cutting speed 1000 m/min, cutting depth 1 mm, clearance angle 15°, and rake angle 4°.     

Linear ball guide design optimization considering stiffness,friction force,and basic dynamic load rating using particle swarm optimization

Journal of Mechanical Science and Technology - Linear-motion ball guides are one of the most common supporting elements in machine tools. Their design optimization is highly crucial for engineers...