Munition Casing EDM Microholes for Controlled Fragmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for achieving controlled fragmentation in munitions, such as laser microdrilling, face challenges with aspect ratios and material susceptibility to cracks, particularly in thicker casings like the Mk-80 family, which limits their effectiveness and increases manufacturing costs.
Innovation Solution
The use of electrical discharge machining (EDM) to form microholes in the casing of munitions, specifically with a depth of 25-75% of the casing thickness and an inner diameter of 100 μm to 600 μm, arranged in an offset pattern to create initiation sites for fracture under explosive loading, thereby improving fragmentation performance without significantly altering the casing's surface or reducing mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser microdrilling is used to create microholes in thick casings (Mk-80 family), then fragmentation performance can be improved, but the aspect ratio required (127:1) is difficult to achieve and manufacturing costs increase
Solution Approach 1:
The patent replaces laser microdrilling (optical/thermal process) with electrical discharge machining (electrical process) to create microholes. EDM achieves the required high aspect ratios (127:1) in thick casings without the limitations of laser drilling, resolving the contradiction between manufacturing precision and ease of manufacture.
Solution Approach 2:
The patent changes the manufacturing process parameters by switching from laser drilling to EDM, which enables achieving aspect ratios of 127:1 in casings up to 2 inches thick. This parameter change resolves the inability of laser drilling to achieve sufficient aspect ratios in thick materials.
2Manufacturing precision
If laser microdrilling is used to create deep microholes in thick casings, then fragmentation control improves, but drill times increase making mass production difficult
Solution Approach 1:
The patent substitutes EDM for laser microdrilling to create microholes in thick casings. EDM achieves the necessary hole depth and precision for fragmentation control while significantly reducing processing time compared to laser drilling, thereby enabling mass production of munitions with controlled fragmentation.
3Manufacturing precision
If laser microdrilling is used to create microholes, then fragmentation performance improves, but cracks in the microstructure make the material susceptible to early fatigue failure
Solution Approach 1:
The patent replaces laser microdrilling with electrical discharge machining to create microholes. EDM produces cleaner holes without the microcracks and thermal damage associated with laser drilling, maintaining fragmentation performance while eliminating the susceptibility to early fatigue failure.
4Manufacturing precision
If traditional methods (notches or grooves) are used to control fragmentation, then fragment size distribution is controlled, but the surface of the casing is significantly altered which may not meet flight safety requirements
Solution Approach 1:
The patent applies local quality by creating microholes (3-5 mm deep) at specific locations on the casing surface rather than altering the entire surface with notches or grooves. This localized modification controls fragmentation while preserving the overall casing surface profile and meeting flight safety requirements.
Solution Approach 2:
The patent transitions from surface-level modifications (2D notches/grooves) to subsurface microhole creation (3D features). The microholes extend 3-5 mm into the casing material, providing fragmentation control through volumetric changes rather than surface alterations, thus preserving the external casing profile.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
EDM microholes enhance fragmentation performance by controlling fragment size and distribution, maintaining the mechanical strength of the munition, and allowing for mass production without the need for special interior liners, thus addressing the limitations of existing methods.
Implementation Method 1
forming holes in the casing using electrical discharge machining (EDM)
Implementation Method 2
When the charge is detonated, explosive energy from the charge causes the casing to break into fragments
Data Source
AI summary
A method for forming a fragmentation explosive munition includes providing a casing, and forming holes in the casing using electrical discharge machining (EDM), thereby forming a modified casing.