Analysis of D'Alembert Unfolding Technique for Hopkinson Bar Gage Records
Abstract
The bar gage is an instrument frequently used to make measurements of airblast pressures produced by explosive charges. The blast pressure to be measured is applied to the end of a strain-gaged steel bar. Unfortunately, reflections from the ends of the bar will be superposed upon the pressure input, limiting the useful record length. In 1983, a method of numerically removing these reflections was proposed. This method, based upon the D'Alembert solution to the thin rod wave equation, unfolds the reflections, thereby creating a record of original pressure input. In this thesis, the uncertainty of the results from the D'Alembert unfolding method are studied. These error sources are considered: wave speed, reflection coefficients, and dispersion. Numerical and analytical techniques are applied to obtain the uncertainty for an arbitrary pressure wave form. Specific wave forms are unfolded and evaluated to draw general conclusions regarding the uncertainties inherent to the unfolding technique.... Airblast measurement, Reflections, Bar gages, Stress wave transmission, D'Alembert unfolding, Unfolding.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1992
- Accession Number
- ADA268494
Entities
People
- Alan P. Ohrt