Refinement of Sonic Fatigue Structural Design Criteria

Acoustic fatigue resistance of aircraft structures at elevated temperatures

“…The aircraft designer found there data to be of considerable value and he could, with a certain amount of individual judgment and experience, effectively control acoustic fatigue problems for conventional subsonic aircraft. Increasing aircroft performonce ond size, coupled with increasingly stringent requirements for structural efficiency, resulted in subsequent programr (3)(4)(5)(6)(7)(8) which refined the design criteria to reduce conservatism and eliminate unnecessary weight from structural designs. The results of these previous programs have considerably redmed the uncertointies involved in predicting dynamic response and l i f e characteristics of conventional structures subiected to both propulsion system and oerodynamic noise.…”

“…Dynamic stresses were calculated based on clamped-edge conditions(3) and correlated against measured stresses, resulting i n the following empirical equotions for rms stress:o Rivet row at midpoint of long side (y = b/2) o Rivet row at midpoint of short side (X = a h ) where $(f) i s therms pressure density of the ocovrtic excitation and i s the panel damping ratio. These relotions provide estimates of the rms stress at the maximum strain locotions for a panel buckled into and responding in the fundamental mode.…”

Jet Noise Excitation of an Integrally Stiffened Panel

“…7 ' 9 ' 15 On the experimental side, good quantitative response data has only been available for relatively simple panels. Although many tests on built-up stiffened panels have been carried out, most of these have been for proof testing against fatigue or for developing design chart criteria 16 and are therefore largely unsuitable for verifying theoretical response predictions. Response data for integrally stiffened panels is virtually nonexistent (Ref.…”