Explosive Ordinance Cold Assembly Process
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Solution Overview
Problem
Conventional projectile payload assemblies face challenges with spontaneous ignition due to dynamic stresses and the formation of internal voids or cracks, which can lead to system failure under shock loads, despite precise component tolerances and assembly controls.
Innovation Solution
A process involving shaping an explosive body to fit within a hollow projectile body, cooling the explosive body to a temperature below the anticipated operating temperature, and securing it within the projectile body to create a compressive fit that maintains interference throughout the projectile's lifetime, utilizing the differing thermal expansion characteristics of the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional assembly methods are used with precise component tolerances, then manufacturing precision is improved, but internal void spaces and cracks still form between components during handling and field operational conditions
Solution Approach 1:
The patent applies parameter changes by utilizing thermal expansion and contraction of materials. The explosive charge is cooled to a low temperature (e.g., -70°C) to reduce its volume, allowing it to be inserted into the projectile body. Upon warming to operating temperature, the explosive charge expands to create a tight interference fit, eliminating void spaces and preventing crack formation under dynamic stresses.
2Reliability
If thermal cycling is used to create compressive fit, then reliability is improved, but the process complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-cooling the explosive charge to a low temperature before assembly. This preliminary thermal treatment creates the necessary clearance for insertion. The projectile body is then heated to expand its internal dimensions, creating an interference fit when the cold explosive charge is inserted. This preliminary action eliminates the need for complex post-assembly adjustment procedures.
3Ease of manufacture
If conventional assembly without thermal treatment is used, then ease of manufacture is improved, but spontaneous ignition can occur due to dynamic stresses and internal voids
Solution Approach 1:
The patent applies thermal expansion by exploiting the differential thermal expansion coefficients between the explosive charge and the projectile body. The explosive charge is cooled to contract its volume for easy insertion. Upon warming to operating temperature, the explosive charge expands to create a tight interference fit, eliminating void spaces that could lead to spontaneous ignition under dynamic stresses.
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
This process ensures that no voids or cracks form between the explosive and projectile bodies, preventing system failure by maintaining a residual compressive force that counters thermal expansion and contraction, ensuring reliable operation under various conditions.
Implementation Method 1
cooling the explosive body to a temperature below a lowest anticipated operating temperature of the projectile
Implementation Method 2
normalizing the temperature of the nested bodies to a common temperature
Data Source
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AI summary
An assembly process is described for producing an ordnance projectile wherein the projectile maintains a compressive force on an explosive body carried therein throughout an anticipated operational temperature range. The process includes raising the temperature of the hollow projectile body to an elevated temperature, cooling the explosive body to a temperature below a lowest anticipated operating temperature of the projectile, nesting the cooled explosive body within the hollow projectile body while the projectile is at the elevated temperature, securing the explosive body and the hollow projectile body together, and normalizing the temperature of the nested bodies by allowing them to come to a common temperature, typically room temperature. Different thermal expansion characteristics of the inner and outer bodies will result in the projectile maintaining a compressive force on the explosive body at normal temperatures.