Failure vs Damage

[Brian]

I am a student working for the summer for a company that produces vehicles for use in military applications. My assignment is to analyze field data from service reports for failed subsystems, and attempt to model the failure rates of these systems in the field. I have a huge volume of reports from which to gather information, but they are not categorized by damage or failure. Can anyone, perhaps from the automotive industry, suggest some rules of thumb for diffentiating between reliablity failures and damage?

As an example, looking at tires: The vast majority of tire failure reports seem to be due to two failure modes. The first, tread "wear and tear" seems fairly obviously to be a reliability issue. But there is a very large number, possibly half the incidents, that are due to cuts, slashes, and punctures sustained in "extreme" driving conditions that apparently exceed the design requirements of the tires. The general thinking here is that the tires that are changed due to this "damage" should be considered as suspended data for the failure analysis.

Since most of the subsystems are vendor items, the failure rate data will be used more for sparing considerations that design development. My feeling is that the "damage" should be analyzed as a second failure mode and the overall replacement rate established as a composite of these two rates, for the sake of spares provisioning.

Any thoughts would be great, thanks