Cartridge Case Analysis System

Simulate Case Deflections and Chamber Interaction During Firing Pressurization

The modeling and analysis of a cartridge case requires an elastic-plastic, thermal, dynamic solution. The use of general purpose finite element programs for case analysis can be very expensive and labor intensive because the model must contain many elements to obtain stress distributions in the thin cylindrical wall region of the case and in the base region. Additionally, the case material can exceed its yield point for a large part of the interior ballistic cycle, requiring an inelastic analysis with relatively long computation times.

To improve computational and parametric design efficiency, Arrow Tech Associates, Inc. has developed an analytical tool specifically to analyze cartridge cases, called CASAS (CASe Analysis System).

CASAS is a primary analytical tool to perform the elastic-plastic, dynamic analysis (including transient heat effects) required for cartridge case design.

CASAS simulates the dynamic interaction of the cartridge case and gun chamber in five phases of the firing cycle:

• Initial Conditions - definition of material properties such as modulus, density, coefficient of thermal expansion, thermal conductivity, along with case-chamber gaps & bolt stiffness.
• Propellant Ignition - initial case contact with the chamber wall.
• Pressure Load Increase to Maximum - maximum composite structure deflection
• Elastic case recovery - internal pressure decays to atmospheric conditions.
• Residual Case/Chamber condition - clearance or interference between the case and the chamber, case extraction force.

CASAS is ideal to perform the following case/chamber parametric studies:

• Dimensional
• Stress-Strain Curve
• Chamber Pressure
• Friction Coefficient
• Extraction Temperature
• Case/Chamber Gap Size
• Static Head Space
• Dynamic Head Space

CASAS output includes:

• Maximum Total Plastic Case Strain (assess case failure)
• Extraction force required
• Maximum Bolt Load

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