Accession Number : ADA114660

Title :   An Investigation of Mechanisms Effecting Environmental Stress Cracking in Titanium Alloy.


PDF Url : ADA114660

Report Date : 06 Jul 1981

Pagination or Media Count : 34

Abstract : A heat treated version of titanium alloy (Ti6A14V) has been under an environmental stress cracking investigation. The acoustic emission (AE) techniques were used to monitor crack growth in a 1 inch thick WOL bolt loaded compact tension test specimen under a linear compliance load to provide plane strain fracture over the environment test duration. An acoustic emission transducer (S-140B) was used to detect the crack movement in the test specimen while it was submerged in a closed loop methanol environment. The acoustic signals were received at a gain of 85 dB in a high bandpass filter range of 100-300 KHz and displayed in the totalizer window as digital output data, (BCD). The signals were then passed into the D/A converter and recorded as analog data on the x-y plotter. Two significant results were revealed by the AE technique, (1) heat treating just below the beta transformation temperature and annealing for a select time improved the fracture toughness in the alloy, and (2) in a plane strain load mode at a constant crack-opened-displacement (COD), the titanium alloy was crack sensitive in a pure methanol environment and not crack sensitive in the laboratory atmosphere environment. The acoustic emission rate, hence crack growth rate, appears to be a function of the methanol concentration, thus related to a diffusion mechanism.

Descriptors :   *Titanium alloys, *Crack propagation, *Stresses, *Acoustic emissions, Environmental tests, Fracture(Mechanics), Carbinols, Electroacoustic transducers, Energy transfer, Heat treatment, Strain(Mechanics), Loads(Forces), Photomicrography, Diffusion, Grids(Coordinates), Plotters

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE