Deformation Behavior of Polyethylene and Polycarbonate in Tension and in Compression at Atmospheric Pressure.
Abstract
The stress-strain behavior of high-density polyethylene and Lexan polycarbonate was examined in tension and compression. The results showed that for both the polyethylene and polycarbonate tested, the yield and flow stresses in compression exceeded those in tension, a phenomenon known as the strength differential or S-D effect. The magnitude of the effect was about 5 + or - 1 and 14 + or - 2 percent for the polyethylene and the polycarbonate, respectively. Measurements of the volume changes occurring during and resulting from plastic deformation with density determinations and dilatometer tests showed that polyethylene underwent a volume expansion, whereas polycarbonate underwent a volume contraction as a result of plastic deformation. The volume contraction in polycarbonate is in complete disagreement with the normality flow rule of plasticity theory and lends credence to our previous hypothesis, from studies on steels, that the classical theory of plasticity should be modified to include pressure-dependent yielding without requiring volume expansion. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1977
- Accession Number
- ADA042480
Entities
People
- O. Richmond
- R. J. Sober
- W. A. Spitzig
Organizations
- U.S. Steel