No abstract

A push-pin type test is proposed as a general approach for bond strength evaluation normal to bonded areas for laminated structures. The evaluation method includes experiment and finite element (FE) simulation. The method has been successfully applied to evaluation of the bond strength of laminated structures made with ultrasonic consolidation (UC). Bond strength varying with UC process parameters has been studied. Based on the results of the simulation and the experiment, a quantitative correlation has been identified between the percent of bonded area and bond strength for UC.

No abstract

Cross-weld creep testing conducted at 650 • C under 69 MPa stress has reproduced either the Type I or Type IV failure mode in Grade 91 welds, depending on the post-weld heat treatment procedures. Welds post-weld heat treated below the A C1 temperature have ruptured in the Type VI failure mode, while welds heat-treated above the A C1 temperature of the alloy have ruptured in the Type I failure mode. Heat-treatments at lower temperatures and shorter durations have produced a reduced creep rate. The accelerated short term stress-relaxation test has been conducted to obtain the input creep rates for a finite element model for the cross-weld creep testing. The model predicted secondary creep rates are in good agreement with the results from the conventional cross-weld creep tests. From the finite element model, the creep damage by cavitation is believed to start at regions where the first principal stress and stress triaxiality concentrate.

No abstract