Positron lifetime measurements as a non-destructive technique to monitor fatigue damage. Progress report

Technical Report · Sat Sep 01 04:00:00 EDT 1973

DOI:https://doi.org/10.2172/4392236· OSTI ID:4392236

Byrne, J G

The critical parts (electronics in the base of the photomultipliers) of the electronics have been brought under temperature control of within plus or minus 0.1 deg C thus minimizing drift problems. In data analysis a computer program is functioning in which there are no fixed experimental parameters. This permits much more accurate results. Samples of pure Ni and a Ni-66.5% Co alloy have been fatigued to failure. Positron lifetime and x-ray particle size were measured at various fatigue lives and transmission electron microscopy was performed after failure. Good correlation was found between the three techniques and it appears that positron lifetime can be used as an effective tool to study fatigue mechanisms. It is a more sensitive nondestructive measurement than is x- ray particle size. It has been established that grain boundaries make a distinct contribution to the positron lifetime. Positron lifetime increases with plastic tensile strain in a manner dependent on initial grain size and in a manner consistent with existing work hardening theories. There are indications that the positron lifetime may be sensitive to hydrogen embrittlement or hydrogen assisted cracking (HAC) in steels. Experiments to study lifetime changes during cyclic softening and cyclic hardening of ArSI 4340 steel are beginning. (auth)

• Research Organization: Utah Univ., Salt Lake City (USA). Div. of Materials Science and Engineering
• NSA Number: NSA-29-004726
• OSTI ID: 4392236
• Report Number(s): COO--2128-5
• Country of Publication: United States
• Language: English

Related Subjects

*COBALT BASE ALLOYS-- FATIGUE
*NICKEL ALLOYS-- FATIGUE
*NICKEL-- FATIGUE
*POSITRONS-- LIFETIME
ELECTRON MICROSCOPY
FAILURES
GRAIN SIZE
IMPURITIES
N50230* --Metals
Ceramics
& Other Materials--Metals & Alloys--Properties
Structure & Phase Studies
NONDESTRUCTIVE TESTING
PARTICLE SIZE
STRAIN HARDENING
STRAINS
X- RAY DIFFRACTION