Failure Mode Effect and Criticality Analysis of
Stub axle subassembly
FMECA is a methodology to identify and analyse predicted failure modes of various parts within the assembly or system. It is a technique to resolve potential problems in a system before they occur. It is most widely used reliability analysis technique performed between the conceptual and initial stage of the detailed design phase of the system in order to assure that all the potential failures have been considered and the proper provisions have been made to eliminate these failures.  (Ref. system reliability theory,2nd edition, Marvin Rausand) this technique can assist in selecting alternative concept for the same system and also provide a basis for maintenance planning.
2. FMECA Prerequisites:
I. Definition of the system:
The given stub axle subassembly includes mainly three parts: 1. Stub axle
2. Steering bearing and boss subassembly 3. Bracket or steering arm
All these parts are assembled by means of welded joints or bolted joints and the whole subassembly is linked with the steering rod by means of the swivel joint. The basic configuration is shown in the body diagram -1 below.
The basic function as we know of the system is to steer the vehicle, in the other words, turning the wheel any direction we want by simply rotating the steering wheel. So rotary motion of the steering wheel is then converted into the linear motion of steering rod which results movement the wheels.
It is here assumed that the under worst condition without abusive use, the system is failed which is to be analyzed in terms of safety and reliability.
3. System structure analysis:
The boss and bearing subassembly comprises of two bearings, bearing spacer in between, upper and...
References: 1) The Hand outs of Engineering Design Methods given in class.
Website: www. Ntnu.no/ross/srt/slides.
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