Approaches to Mechanical Reduction of Dispersion in Blast Measurements Using Kolsky Bars
Abstract
Cylindrical Kolsky bars offer an attractive means for measuring time-varying blast pressure fields, but their accuracy is often compromised due to dispersion effects from high-frequency stresses resulting from Poissons effect, which propagates in the bars radial direction. Radial stresses distort the axial strain signal due to the inertial effects they induce in the bars longitudinal direction. Using appropriate bar geometry can reduce some of the inaccuracies. In addition, analytical and numerical methods have been devised that can, in some situations, improve blast measurement accuracy. Here, we demonstrate, using computational methods, the efficacy of two more direct approaches that involve applying mechanical means to suppress blast pressure signal inaccuracy. The first approach uses beryllium, which has an extremely low Poisson ratio of 0.03, as the bar material to reduce signal distortion due to dispersion. The second method uses mechanical constraint in the radial direction to suppress the noise in the pressure signal. Initial computational evaluations of this technique used an annular sheath in intimate contact with the outer radius of the bottom section of the bar. Using a Teflon sheath reduced the overprediction of peak blast pressure from a level of 12 percent the baseline level for an unconfined bar, to 3 percent.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2021
- Accession Number
- AD1149577
Entities
People
- David Fox
Organizations
- United States Army