Plastic rotational factor and J-COD relationship of three point bend specimen

✍ Scribed by Shang-Xian Wu

• Publisher: Elsevier Science
• Year: 1983
• Tongue: English
• Weight: 798 KB
• Volume: 18
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(83)90098-x

✦ Synopsis

COD calculation formulas in DD( ) and BS 5762 have been compared theoretically. It has been shown that differences between the results of these calculation formulas generally are about 10%.

An experimental method for determining the plastic rotational factor r, of three point bend specimen has been described. This method uses two clip gauges and records P-V and q-V plots simultaneously, and r,, can be determined from the slope of q-V curve. Experimental results of three steels show that under smaller amount of crack growth, the r, remains a constant about 0.45 and is not dependent on a/W noticeably.

Optical microscopic observations on half-thickness sections of specimens show that under small amount of crack growth observed fatigue precrack tip opening displacement and crack tip opening displacement calculated by using formula with r, = 0.45 are in agreement.

P-V and P-q plots were simultaneously obtained on the same specimen. .I integral values and COD values were obtained from both P-V and P-q plots. Two series of .I integral values and two series of COD vlalues of three steels are in agreement within 5%. Experimental data of .I,, and 8, of three steels were used for checking J-COD relationship within 8%.