R-curves for materials with large fracture toughness to yield strength ratios
✍ Scribed by Y. W. Mai; A. G. Atkins; R. M. Caddell
- Publisher
- Springer Netherlands
- Year
- 1975
- Tongue
- English
- Weight
- 145 KB
- Volume
- 11
- Category
- Article
- ISSN
- 1573-2673
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✦ Synopsis
Unless certain minimum size requirements are satisfied, cracking of sheet materials with high fracture toughness R and low yield stress o is often complicated by generalised yielding in regions away from t~e crack tip. For materials with /(ER)/o > 0.2/m, these requirements become prohibitively large for most ~aboratory tests. To tackle this problem, various theories such as near tip strain, J-integral, crack opening displacement, and equivalent energy have been suggested as criteria for ductile fracture. Independently, Gurney, Mai, and Owen [I] have developed a new experimental technique involving the construction of an apparatus which reinforces laboratory size testpieces so that all irreversibilities caused by generalised yielding in parts remote from the crack tip are eliminated. Figure 1 shows the apparatus used in [i]. The webs of the channel section made of steels with high yield strengths (o -~ 200 ksi) are the reinforcements to the testpiece, and insofar as th~ load application arms (i.e., the flanges) remain elastic, valid fracture toughness values representing large scale brittle behaviour of the same material are determined unambiguously from the sector area method introduced by Gurney and Hunt [2].