The cyclic stress-strain response of copper at low strains—II. Variable amplitude testing

✍ Scribed by J.C. Figueroa; C. Laird

• Publisher: Elsevier Science
• Year: 1981
• Weight: 799 KB
• Volume: 29
• Category: Article
• ISSN: 0001-6160
• DOI: 10.1016/0001-6160(81)90002-x

✦ Synopsis

The cyclic stress-strain response of polycrystalline copper has been explored at low strain amplitudes by means of two multistep tests. In one called the 'large step test', Program A, cycling is first begun at 2 x lo-' to create a cell structure in saturation and thereafter tests were conducted on the same specimen at suazssively lower levels of strain or stress. However, between steps, cycling at 2 x lo-' to saturation was always done to reestablish the initial cell structure. The other teat was a small step decremental test to very low values of strain or stress followed by an incremental step test-this test is called the 'small step test', Program B. The cyclic stress-strain curve associated with the large step test followed that observed in constant plastic strain testing (see Part I, the companion paper to this) with some differences at low strain. The cyclic stress-strain curve associated with the small step test followed that observed in constant stress testing (see Part I), but again with differences. In particular the 'plateau' observed in constant stress testing was not observed in the decremental test. Specimens tested by both of these tests showed dipolar walls in their dislocation structures; however, differences in the scale of these structures caused the vacations in cyclic stress-strain curves. It is argued that the cyclic stress-strain curvea observed here represent bounds in the cyclic response.