MASTERS PROJECT FALL 2014 DAN FLAVIN 29 SEPTEMBER Springfield Rifle Bolt Analysis

Introduction Firearms consist of a tube, sealed at one end Modern firearms require that the seal be moveable. The mechanical structure used to provide this seal is called the bolt. In bolt action rifles, this bolt locks into the main structure of the rifle, called the receiver. This is usually done by lugs on the forward end of the bolt.

Goal Determine stresses within a rifle bolt using FEA. In this case, the 1903 Springfield rifle used by the US military was chosen Steps: Geometry: develop a 3D model of the bolt, in least-material condition Materials: determine the material properties of the steel in the bolt Finite Element Analysis (FEA): determine the loading of the bolt in a worst-case scenario

Geometry Only the head of the bolt is modeled, in order to save processing time.  1: Cartridge base  2: Bolt head  3: Receiver ring

Materials Bolt material is WD2340, equivalent to SAE 2340, a now-obsolete steel alloy. PropertyValue Young’s Modulus, elastic (typical to steels) 29,700 ksi Young’s Modulus, plastic (estimated)300 ksi Poisson’s Ration (typical to steels)0.29 Density0.284 lb/in 3 Yield Stress128 ksi Terminal Stress150 ksi

Finite Element Analysis The model used the static solid mechanic module (more conservative than dynamic) Plasticity with strain hardening was added to the model. Bolt thrust of 75ksi (proof load) was used.

Results: Displacement

Results: von Mises Stress Note than maximum stress values appear to be artifacts of stress concentrations within the software.

Results: Percent Yield Isosurfaces shown are of von Mises stress divided by yield stress (including the effects of strain hardening)

Conclusion The bolt, as modeled, will barely withstand the proof load. However, these conditions do not include strength increase due to rate of strain, and take extreme conditions not likely to be found outside of a testing laboratory. This modeling technique could be extended to the barrel and receiver for greater accuracy Further accuracy could also be developed by testing of material properties to get more accurate values