Eutectic Solder Venting Plug for Munition Cook-Off Safety
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Solution Overview
Problem
Existing munitions are prone to high-order detonation due to internal hoop pressure caused by temperature increases beyond normal operating ranges, leading to undesired explosions, and prior lifting plug designs fail to effectively vent energetic materials while maintaining structural integrity and drop indicator functionality.
Innovation Solution
A lifting plug with a eutectic solder joint between the plug and a ring, which melts at a predetermined temperature, allowing the plug to separate and vent cook-off gases, preventing high-order reactions and maintaining mechanical properties at normal temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lifting plug seals the munition during transportation, then the munition is protected from the environment, but under high temperatures the sealing causes internal hoop pressure leading to high-order detonation
Solution Approach 1:
The lifting plug incorporates a eutectic solder joint with a specific melting point (e.g., 183°C for tin-lead eutectic) that changes the mechanical state of the plug at elevated temperatures. Below the melting point, the joint provides a sealed connection; above it, the joint softens and allows venting, thus changing the parameter of seal integrity with temperature
Solution Approach 2:
The eutectic solder joint utilizes a phase transition from solid to liquid at a predetermined melting point. This phase change enables the lifting plug to automatically transition from a sealed state during normal transportation to a vented state during cook-off conditions, relieving internal pressure without requiring active control
2Object-affected harmful factors
If wax material is incorporated to vent at temperatures below explosive reaction temperature, then high-order reaction is prevented, but structural integrity of the lifting plug degrades and drop indicator functionality is lost
Solution Approach 1:
Instead of using wax that degrades structural integrity, the invention uses a eutectic solder joint whose mechanical properties change with temperature. The solder maintains sufficient strength at room temperature to support the lifting plug function and drop indicator, but softens at the eutectic melting point to enable venting
Solution Approach 2:
The lifting plug is constructed as a composite structure combining the plug body material with a eutectic solder joint. This composite design allows the joint to provide both mechanical bonding strength at low temperatures and controlled softening at high temperatures, combining the benefits of structural integrity with thermal venting capability
3Strength
If threaded rings are used to limit vent opening size, then structural integrity is maintained, but the ability to vent energetic material is limited
Solution Approach 1:
The eutectic solder joint changes its effective opening size with temperature. At room temperature, the solid solder provides a tight seal with minimal opening. At elevated temperatures above the eutectic point, the softened solder allows the opening to expand significantly, enabling effective venting of energetic materials while maintaining structural integrity during normal handling
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
The solution effectively reduces high-order detonations to combustible reactions, enhancing safety during elevated temperature exposures without compromising structural integrity or drop indicator functionality, thus preventing material damage and loss of life.
Implementation Method 1
the joint between the lifting plug and the ring is soldered with a eutectic solder formed from one or more eutectic materials. The eutectic solder melts at a predetermined temperature and allows the lifting plug to be ejected from the munition.
Implementation Method 2
the eutectic solder melts at a predetermined temperature and allows the lifting plug to be ejected from the munition. The removal of the lifting plug from the munition eliminates pressure buildup within the munition cavity
Data Source
AI summary
A venting lifting plug is provided for an unfuzed munition having a cavity with internal threads.