Study the Effect of Fasteners Coating Materials to Resolve the Leakage Issue in Steering Gear Assembly

<div class="section abstract"><div class="htmlview paragraph">In commercial vehicle, Hydraulic Power Assisted Steering (HPAS) gear plays a vital role to utilize the hydraulic force to assist the steering application. HPAS gear consists of housing, sector shaft, side cover, worm shaft, valve housing and rack piston. Side cover assembly is connected with the housing assembly through bolts which is in exposure to high pressure working hydraulic fluid. Since, some of the bolts are exposed to the fluid environment in the inner surface of the housing, during high pressure running condition, torque relaxation in the bolt is observed which leads to the loosening of bolts and tends to hydraulic fluid leakage through bolts. The current phosphate coated bolts are getting relaxed and loosened due to the bolts that exposed to the oil environment which have insufficient coefficient of friction in the bolt head and thread. To overcome the bolt failure during high pressure hydraulic application, various bolt coating analysis is experimented to withstand the sufficient coefficient of friction in the bolt. The detailed comparison study is carried out for the bolts such as failure torque, load, frictional force, bearing stress and thread profile deviation. This paper deals with the failure analysis of bolts in a high pressure HPAS gear assembly and comparison study is carried out between analytical calculations and experimental validation.</div></div>