STRAIN AND CRACK-OPENING MEASUREMENTS FOR THE DETERMINATION OF THE STRESS INTENSITY FACTOR AT THE TIPS OF CRACKS IN THIN SHEET MATERIALS

摘要

Three strain-gauge measurements ahead of the crack tip and perpendicular to the cracking plane are used to calculate the stress intensity factor that defines the crack-tip stress field in any thin sheet, stiffened or unstiffened, plane or slightly curved. A fatigue test on a cracked specimen cut from the same material yields results that permit prediction of the fatigue cracking rate in the actual structure. The possibility of extending the method to surface cracks contained in thick components is considered;as a preliminary step for the use of crack-opening displacement measurements, results of such tests for thin sheets are described.