EXPERIMENTAL INVESTIGATION OF LARGE AMPLITUDE ELASTIC WAVE PROPAGATION AND THE ELASTIC-PLASTIC TRANSITION IN POLYCARBONATE (LEXAN)

An experimental system for determining strain-time and surface rotation-time histories during axial impact of rods is used to investigate the propagation of large-amplitude elastic strain waves and the elastic-plastic transition in polycarbonate (Lexan) rods. This previously-reported system employs in-surface diffraction grating strain transducers illuminated by a pulsed ruby laser, with the strain and surface rotation-dependent diffraction pattern recorded by high speed streak cameras. Strain-time histories are obtained for times up to 250 microsec after impact at locations ranging from two to four diameters from the impact site in rods undergoing axial impact at striker velocities of approximately 540 ft/sec; strains to 8.65 percent and strain rates in excess of 2200 per sec are recorded. Strain-time histories at one-third diameter from the impact site at striker velocities ranging up to 700 ft/sec reveal that the elastic-plastic transition in Lexan for pulse-type loadings (approximately 120 microsec loading-unloading) occurs at about 11.5 percent strain, with an abrupt change in the character of the unloading as the transition strain is exceeded; strains to 13.3 percent and strain-rates to 15,700 per sec are recorded. The effect of a previous impact on the subsequent strain-time history is examined, as well as the relationship between maximum strain and residual strain for strains near the elastic-plastic transition.

• Corporate Authors:

  North Carolina State University, Raleigh

  Raleigh, NC  United States  27695
• Authors:
  • Liddell, W L
  • Steele, R S
  • Bingham, W L
  • DOUGLAS, R A
• Publication Date: 1971-12

Media Info

• Features: References;
• Pagination: 36 p.

Subject/Index Terms

• TRT Terms: Elastic waves; Impact loads; Structural analysis; Wave motion
• Subject Areas: Marine Transportation; Materials;

Filing Info

• Accession Number: 00024808
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: 71-6 Tech Rpt
• Contract Numbers: N00014-68-A-0187
• Files: TRIS
• Created Date: Jan 21 1973 12:00AM