Linking Bench Wear to Vehicle Mileage with DOE and Weibull Analysis

Friction facing durability in the field varies a great deal, and in most cases very little is known about the conditions the vehicle actually operated under.

Two customers can wear out the same facing at very different rates, and without the operating history there is no way to tell whether that reflects the material or the use.

🔍 The problem

Field data is plentiful but uncontrolled. Bench data is controlled but does not obviously translate to mileage.

Bridging the two requires a test procedure designed to span the range of conditions a vehicle is subjected to, plus a statistical framework strong enough to handle the scatter that remains.

🧪 The approach

A test procedure was developed capable of containing the different operating conditions of a vehicle. Statistical applications were then used on top of it: design of experiments (DOE) to plan the tests and derive equations from the results, and Weibull curves for the reliability analysis of wear life.

📈 What came out of it

A correlation was determined between wear results on the bench and vehicle mileage. With that correlation in hand, the durability of a friction facing on a vehicle can be estimated from bench testing alone.

A second outcome was knowledge about how the material behaves relative to energy and working temperature — not just how long it lasts, but what drives how long it lasts.

💡 Why it matters

Estimating field durability from a bench removes the longest feedback loop in friction material development.

It also makes durability claims defensible, because they rest on a documented correlation and a Weibull reliability model rather than on accumulated field impressions.

📄 Full publication

Gregori, I. R. S.; Zanotto, P.; Haertel, W. — Definition of the Relationship Between Clutch Facing on Vehicle and Bench Testing Using Reliability and DOE. SAE Technical Paper 2005-01-1766, April 2005.

Read the full publication on ResearchGate