Test Method for Key Parameters of Small-Caliber Gun Internal Ballistics Based on Double-Layer Double-Grid Structure Strain

Testing internal ballistic parameters has long been a challenging issue in the field of internal ballistics. Therefore, a novel method based on a double-layer and double-grid structure strain tester was proposed to assess the key parameters of internal ballistics for small-caliber guns. This approach offers a simultaneous testing of multiple internal ballistic parameters through a single test system. It enables the acquisition of the entire test curve without compromising the structural integrity of the gun. Moreover, the method boasts a long service life, compact size, low cost, simple operation, and excellent electromagnetic compatibility. The core idea was to test the strain on the outer wall of the barrel using the double-layer and double-grid strain tester. In particular, the chamber pressure, projectile bottom pressure, and projectile velocity were calculated according to the thick-walled cylinder theory, the projectile bottom pressure solving model, and the projectile motion equation. Initially, the mechanism of this test method was analyzed. Subsequently, a strain tester was designed for a 30 mm caliber gun to test the outer wall strain. Finally, the internal ballistic parameters obtained from the strain test were compared with traditional measurements, which showed largely consistent results. During the ascent phase of the pressure curves, the root mean square (RMS) errors for the chamber pressure and the projectile bottom pressure curves are 1.71 and 3.60 MPa, respectively. The errors in the maximum values of chamber pressure, projectile bottom pressure, and projectile velocity are 1.1%, 0.9%, and 1.2%, respectively, thus verifying the feasibility of the strain test method.