| Popis: |
The U.S. Army Research Laboratory is currently investigating several candidate ceramic materials for use as the bore material for advanced gun barrels. Extensive characterization of the thermal and mechanical properties of these materials is underway using primarily standardized test procedures. For verification of modeling efforts and probabilistic strength predictions, the materials are also being tested via internal pressurization to rupture. The approach to this test is to compress an elastic material and allow the Poisson's expansion to pressurize the tube. The expression for calculating the pressure will be detailed, along with experimental verification on a control sample. The procedure has yielded pressures in excess of 240 MPa (35 ksi), which is not the limit of the fixture but is the maximum rupture pressure achieved prior to failure of the sample. The rupture pressures and maximum stress level will be reported for each of the following materials: Al 2 O 3 (ALOX), ZrO 2 (ZR02), SiC (SCEH, SCLH, and SC46), Si 3 N 4 (SN47 and SN5P), and SiAlON. An attractive feature of this methodology is that during failure, the ceramic pieces are not propelled by high pressure gases or fluids, so the parts can be collected for post-mortem analysis and fractography. Where possible, fractography will be performed and statistical analysis of the results will be presented. |
