1972 Volume 1972 Issue 132 Pages 405-417
A series of research for clarifying the brittle fracture initiation characteristics of narrowly spaced notches, has been carried out following the research reported previously (1st Report). Firstly, tensile tests were conducted at room temperature by using test specimens of 200 mm width, and thereby interaction effect of narrowly spaced notches were analysed by means of measuring the crack opening displacement by Moiré method. Secondly, brittle fracture tests were conducted at a low temperature (-160°C) by using test specimens of 400 mm width.
The above analyses and tests were respectively carried out for four kinds of neighboring notches, viz. equal length collinear notches, unequal length collinear notches, equal length parallel notches and equal length parallel staggered notches. Steel material tested was a 60 kg/mm2 high strength steel.
The results of test were summarized as follows :
1) From crack opening displacement which is measured at room temperature by Moiré method, it is possible to estimate fracture stress of narrowly spaced notches.
2) Fracture stress of notches arranged in a straight line which is perpendicular to load direction, becomes lower in comparing with that of a single notch, and decreases with distance between notches.
3) Fracture stress of notches, which are arranged in parallel and perpendicularly to load direction, is higher in comparison with that of a single notch and increases with decreased distance between notches.
4) Fracture stress of equal length parallel staggered notches, having the characteristic which combines the equal length collinear notches and equal length parallel notches, varies complicatedly depending upon the location of notches.
