Predicting structural reliability.

A new method for predicting how well materials used in aircraft. automobiles, turbines, and other machines will hold up under heavy strain without developing dangerous structural cracks has been developed at Ohio State University. The aim is to help designers make vehicles and mechanical devices strong enough to withstand everyday stress without failing, indicates Herman Shen, assistant professor of aerospace engineering.

Fatigue cracks can form in any load-carrying structure during normal use, sometimes with catastrophic results. A 1988 incident involving a Boeing 737 in Hawaii brought national attention to fatigue cracks in aircraft. in this accident, the upper portion of the plane was ripped apart in flight when a fatigue crack caused an instability in the structure.

The crack that caused the problems on this flight probably wasn't the result of specific damage, but, rather, the normal wear on the plane. Shen's process will determine how the frames of aircraft, automobiles, and other load-carrying structures will respond when a fatigue crack forms.

The problem with current methods of predicting development of fatigue cracks is that engineers assume that the pressure on the crack. initial crack conditions, and other factors are known from the...