Accession Number : ADA189560

Title :   Threshold Fatigue Crack Growth in Ti-6Al-2Sn-4Zr-6Mo.

Descriptive Note : Master's thesis,

Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s) : Nagy, Dale A

PDF Url : ADA189560

Report Date : Dec 1987

Pagination or Media Count : 78

Abstract : The purpose of this study was to examine the effects of different loading histories, closure loads, and stress ratios on the near-threshold crack growth rate of a Titanium-Aluminum alloy. Two different test types were conducted on four separate specimens to determine the threshold stress intensity of the material. The first test type maintained a constant maximum stress intensity factor, K(max) on a specimen with a growing crack. As the crack grew, the minimum stress intensity factor was increased until the crack growth rate reached the threshold level. The second test type also maintained a constant K(max). For this test a block of cycles was applied to the specimen and if the crack growth rate for the block of cycles was below the threshold level then K(min) was decreased by a small amount and another block of cycles was applied. This process was continued until the crack growth rate reached the threshold level. Once the threshold stress intensity was determined the cracks were grown under constant maximum load and stress ratio (R) to measure the threshold crack growth rate. Both test types were conducted over a wide range of stress ratios to investigate the effects of varying closure loads.

Descriptors :   *CRACK PROPAGATION, *FATIGUE(MECHANICS), *TITANIUM ALLOYS, *ALUMINUM ALLOYS, CONSTANTS, CRACKS, CYCLES, INTENSITY, LOADS(FORCES), RANGE(EXTREMES), RATES, RATIOS, STRESS CONCENTRATION, STRESSES, THESES, THRESHOLD EFFECTS

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE