MASTERS PROJECTFALL 2014

DAN FLAVIN29 SEPTEMBER 2014

1903 Springfield Rifle Bolt Analysis

Introduction

Firearms consist of a tube, sealed at one endModern 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 conditionMaterials: 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.

Property Value

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

Density 0.284 lb/in3

Yield Stress 128 ksi

Terminal Stress 150 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