LIMITS OF STRESS REDUCTION IN A PLATE WITH A HOLE USING PIEZOELECTRICACTUATORS

Recently there has been much interest in adaptive structures that can respond to a varying environment by changing their properties. Shape m emory alloys and piezoelectric materials can be used as induced strain actuators to reduce stresses in regions of stress concentration. In a previous work, we have shown that stress concentration in a plate wit h a hole can be reduced substantially by applied induced strain. Howev er. limited free induced strain (1000 mu epsilon) and low tensile stre ngth limit the effectiveness of piezoceramics for active stress allevi ation. Also, bonded actuators increase the weight of the structure and may have shear lag effects. The present work determines the effects o f such limitations on stress reduction for two load cases: a fatigue l oad case and an extreme load case. Piezoelectric actuators were found to be ineffective in reducing stress concentration factor for the extr eme load case. For the fatigue load case, effectiveness depends on the cost and weight associated with supplying actuation energy.