Investigation on friction-induced judder of vehicle driveline based on a nonlinear friction model

Due to friction characteristics of clutch, the driveline is prone to cause a judder during vehicle starting, and then to cause the vehicle body to vibrate, which affects driving quality. In order to analyze the judder phenomenon, a nonlinear numerical friction model based on the Gaussian friction model is established in this paper. For the driveline of a front-wheel-drive vehicle, a five-degree-of-freedom (5DOF) lumped parameter model including a nonlinear friction element is established. The complex mode of the driveline during the clutch in slip condition is calculated. The key parameters affecting the driveline stability are analyzed. The self-excited judder and pressure-induced judder of the driveline are numerically simulated, and the corresponding causes are analyzed. The nonlinear friction torque of the clutch is also calculated. Furthermore, the effects of the key parameters such as the torsional stiffness and damping of the clutch and drive shaft suppressing the self-excited judder and pressure-induced judder are numerically studied respectively. Compared with the widely used Karnopp friction model, the nonlinear numerical friction model established in this paper comprehensively includes the stribeck effect in slip and the friction torque characteristics in stick. The phenomena of the judder and stick-slip of the driveline during vehicle starting are more accurately simulated. The simulation results are in good agreement with the experimental results, which verify the accuracy and effectiveness of the dynamic model including the nonlinear friction element established in this paper.

Chipping Reduction Using Thermally-Assisted Friction Element Welding

The use of multiple material in the structural components of a vehicle allows for significant weight reduction. Friction element welding (FEW) is a novel method that allows the joining of two or more dissimilar material sheets. A limitation of this process is the chip formation in high strength aluminum alloys, which is observed as the protrusion of thin aluminum segments from under the head of the fastener. Chipping can degrade the joint’s strength over time due to accelerated crevice corrosion. A novel method is proposed to eliminate chip formation using thermal assistance. A grading scheme is developed to quantify the severity of chip formation. The effect of thermal assistance on chipping is analyzed. An investigation is also carried out to validate that the thermal assistance does not negatively affect the process time, energy, and joint strength. Thermal assistance is proposed to be a novel method of overcoming this limitation to allow more widespread use of the FEW process for higher-strength aluminum alloys. Future work will include the development of feasible, rapid methods of heating and measurement of energy utilization for implementation in the industrial environment.

Conduction Heat Assisted Friction Element Welding

Increasing awareness of global warming and strict government regulations have required the automotive industry to pursue lightweighting as an avenue towards increased vehicle efficiency. Lightweight designs typically rely heavily on multi-material use, which enables selective strengthening of critical areas without additional, unnecessary mass. Joining these materials during manufacturing has proven to be a challenging endeavor. Friction element welding (FEW) is one process that is capable of joining aluminum to steel. This two-sided joining technique utilizes a fastener to secure the aluminum sheet by creating a friction weld with the steel sheet. While this process is extremely robust for most materials, the FEW process can result in the extrusion of material from underneath the head of the fastener, termed chipping, which leads to corrosion and aesthetic issues. This behavior is typically seen in high strength aluminum alloys, such as 7075. A solution to chipping is implemented herein, which utilizes a modified downholder to conductively heat the aluminum sheet prior to the FEW process. This heating method was explored experimentally and through various numerical analyses. This method was found to be a viable option for relieving chipping. While the process time was only increased by a maximum of 2.5 seconds, faster, more localized heating should be targeted for future work.

Substantiation of Parameters of Friction Elements of Bernoulli Grippers With a Cylindrical Nozzle

The article provides a step-by-step justification of the parameters of the friction elements of the Bernoulli gripping devices with a cylindrical nozzle. The effect of friction element parameters on the lifting force of Bernoulli grippers with the classic design of the active surface and with the rounded-off nozzle and flat and toroidal surface is considered. Influence of friction elements location radius on grip lifting force is considered. Influence of friction elements shape on grip lifting force is considered. Effect of friction coefficient between friction elements of grip and object of manipulation on minimum required lifting force in order to perform handling operation is investigated. Influence of number of friction elements on Bernoulli grip lifting force is considered. For the grip design with the rounded-off nose and flat and toroidal surface when the elliptical friction elements overlap the end gap by 73%, the lifting force will increase by 7% in torsion with the lifting force without the friction elements.

The Possibilities of Using Ecological Liquids in Tribological Gliding Systems with a Selected Surface Created by the Radial Welding Technology

Presented paper deals with the issue of lubricating tribological systems formed by a double pair operating under mixed conditions of mixed friction before and after experimental tests, which were conducted in accordance with the selected methodology using Tribotestor M‘06 test machine. The lubricating media included ecological oils Plantohyd 46 S by Fuchs and EAL Hydraulic 46 manufactured by the Mobil company. Applied ecological oils can be used in agricultural mobile machines as a replacement for conventional lubricants. The tests were conducted on designated material double pairs. The shaft was made of steel 16MnCr5. The second observed friction element in terms of glide angle test was a steel plate made of S235JR, gliding surface of which was produced utilizing flame powder coating technology. The results were statistically processed and are presented in the form of graphs, tables and figures.