Review on anti-loosening methods for threaded fasteners

Threaded fasteners naturally tend to loosen under vibration,impact,or alternating thermal load.Various anti-loosening methods or strategies are widely applied for preventing loosening,including a few anti-loosening designs and anti-loosening structures.In this review,a variety of influencing factors that improved the anti-loosening ability and helped guide the anti-loosening designs of threaded fasteners are summarized.Second,the anti-loosening structures are classified into two categories,that is,conventional and new-style anti-loosening structures.The former refers to widely used structures in engineering applications,while the latter refers to novel structures not available in the markets.The research on the evaluation and comparison of various conventional anti-loosening structures in terms of preventing loosening is summarized in detail and the newstyle anti-loosening structures from five different aspects are also surveyed based on different structural characteristics.In the future,the effects of combined factors on loosening should be considered to achieve optimal anti-loosening designs.More quantitative research on the mathematical relationship between the anti-loosening performance of conventional structures and structural parameters must be conducted.Furthermore,novel structures with excellent abilities to prevent loosening are needed,and issues of difficulties in installation and disassembly,low strength at thread,large deformation,and temperature dependence also need to be addressed.

Torque Distribution of Electric Vehicle with Four In-Wheel Motors Based on Road Adhesion Margin

With the worsening of energy crisis and environmental pollution,electric vehicles with four in?wheel motors have been paid more and more attention. The main research subject is how to reasonably distribute the driving torque of each wheel. Considering the longitudinal motion,lateral motion,yaw movement and rotation of the four wheels,the tire model and the seven DOF dynamic model of the vehicle are established in this paper. Then,the torque distribution method is proposed based on road adhesion margin,which can be divided into anti ? slip control layer and torque distribution layer. The anti?slip control layer is built based on sliding mode variable structure control,whose main function is to avoid the excessive slip of wheels caused by road conditions. The torque distribution layer is responsible for selecting the torque distribution method based on road adhesion margin. The simulation results show that the proposed torque distribution method can ensure the vehicle quickly adapt to current road adhesion conditions,and improve the handling stability and dynamic performance of the vehicle in the driving process.

New Adaptive Approach for Road Condition Identification in ASR Control System

A novel tire-road adaptive model in longitude direction to formulate the dynamic characteristic between tire and road is proposed in this paper, based on this model, a new adaptive approach of road condition identification is presented to identify the model＇s parameters on-line in order to improve the performance of anti-slip regulation system（ASR）. The optimal slip is determined by using the drive wheel＇s slip and longitude traction force in ASR before the slipping of the drive wheel. Co-simulation is done based on the model for JETTA GTX building with ADAMS/CAR and Matlab, and results show that the adaptive model accords with Pacejka model very well. This adaptive model has simpler form, less number of parameters and higher adaptability than usual, and the new identification approach has a small amounts of operation, which is very suitful for ASR.

Engineering Application and Development of Anti-skid Sand

In view of the increasing cement concrete pavement in China,the proportion of road non-slip surface layer is large,the winter slippery performance is insufficient and the later non-slip treatment is difficult. Through the concrete construction and post-application and development of the anti-skid sand in the road and bridge,the feasible anti-skid optimization measures are put forward.

A numerical study on tread wear and fatigue damage of railway wheels subjected to anti-slip control

Tread wear and rolling contact fatigue (RCF) damage propagated on railway wheels are the two extremely important focal points as they can tremendously deteriorate wheel/rail interactions and hunting stability and destroy wheel surface materials, and subsequently, cut down the lifetime of the wheels. The on-board anti-slip controllers are of essence aiming to hold back the striking slipping of the powered wheelsets under low-adhesion wheel/rail conditions. This paper intends to investigate the impact of anti-slip control on wheel tread wear and fatigue damage under diverse wheel/rail friction conditions. To this end, a prediction model for wheel wear and fatigue damage evolution on account of a comprehensive vehicle–track interaction model is extended, where the wheel/rail non-Hertzian contact algorithm is used. Furthermore, the effect of frictional wear on the fatigue damage at wheel surface is considered. The simulation results indicate that the wheel/rail contact is full-slip under the low-adhesion conditions with braking effort. The wear amount under the low-adhesion conditions is observably higher than that under the dry condition. It is further suggested that the wheel tread is prone to suffering more serious wear and fatigue damage issues with a higher anti-slip control threshold compared to that with a lower one.