Fatigue Design & Evaluation Committee

Total Life Fatigue Project

Engineering is the art of modeling materials we do not wholly understand, into shapes we cannot precisely analyze, so as to withstand forces we cannot properly assess, in such a way that the public has no reason to suspect the extent of our ignorance.

-Dr. A.R. Dykes, Chairman, British Institute of Structural Engineers

The Total Life Project is an effort by the FD&E committee to validate (or not) a potential "Total Fatigue Life Prediction Improved Practice."

The committee has purchased (4) 20ft A36 HR bars for the purpose of evaluating new and existing methods of determining total fatigue life (initiation + propagation). Fatigue tests were performed on hourglass specimens from the purchased steel to determine the strain-life properties and the cyclic stress-strain curve. Crack growth tests were performed on compact tension specimens made from the purchased steel to determine the crack growth properties.

The majority of the steel has been focused on two types of T-specimens: welded and machined. Rectangular steel blanks were welded into the geometry shown on the left below. Other specimens were then machined into the same geometry as measured on a representative welded specimen, shown on the right below. Therefore, parent and welded samples of the same material and the same geometry are available for fatigue testing and comparison so that the effect of the welding process might be recognized.