Asymmetric Threaded Joint for Dissimilar Material Shear Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for joining dissimilar strength structural materials result in inefficient configurations with overly large thread engagement, leading to increased parasitic weight and volume, and fail to provide a controlled release in adverse environments, especially in insensitive munitions and shock mitigation applications.
Innovation Solution
The development of a biased equivalent strength threaded joint with unequal bilateral thread distribution, where the thread thickness and pitch are tailored to provide equivalent shear strength to both materials, allowing for a non-permanent joint with minimal increase in thread length and incorporating secondary vent paths for controlled release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If standard thread engagement is used to join dissimilar strength structural materials, then the weaker material receives sufficient shear area, but the stronger material becomes overly strong with increased parasitic weight and volume
Solution Approach 1:
The patent applies local quality by creating asymmetric thread geometry where the thread thicknesses in the first and second structural members are intentionally made unequal. The thread thickness in the weaker material is increased to provide adequate shear area, while the thread thickness in the stronger material is reduced to minimize parasitic weight. This localized differentiation of thread dimensions allows each material to contribute optimally to the joint strength without unnecessary weight penalty.
Solution Approach 2:
The invention employs asymmetry by deviating from conventional symmetric thread designs where both mating parts have equal thread thicknesses. Instead, the patent specifies that the thread thickness in the first structural member differs from the thread thickness in the second structural member. This asymmetric configuration is mathematically optimized based on the relative strengths of the two materials, enabling the weaker material to receive enhanced shear support while the stronger material maintains minimal necessary thickness, thereby resolving the weight-strength contradiction.
2Strength
If standard thread engagement is used, then joint strength is achieved, but thread length increases leading to excessive parasitic volume
Solution Approach 1:
The patent applies local quality by concentrating the thread engagement length optimization in specific regions. By making thread thicknesses unequal, the design allows the weaker material to have thicker threads over a shorter engagement length, while the stronger material has thinner threads that can be extended or reduced as needed. This localized optimization of thread dimensions enables adequate shear area without proportionally increasing the overall thread engagement length and associated parasitic volume.
Solution Approach 2:
The asymmetric thread thickness distribution enables more efficient use of thread engagement length. The weaker material's thicker threads provide higher shear capacity per unit length, reducing the required engagement length. The stronger material's thinner threads contribute less to shear capacity but occupy less volume per unit length. This asymmetric arrangement allows the joint to achieve required strength with minimized total thread engagement volume, resolving the strength-volume contradiction.
3Strength
If permanent threaded joint is used, then strength is maintained, but controlled release in adverse environments cannot be achieved
Solution Approach 1:
The patent applies dynamics by enabling the threaded joint to transition from a permanent state to a releasable state based on environmental conditions. The asymmetric thread geometry, with the weaker material having thicker threads, creates a predetermined failure mode where the weaker material's threads can be designed to fail at specific stress thresholds or environmental conditions (such as temperature, pressure, or shock). This dynamic characteristic allows the joint to maintain strength during normal operation while providing controlled release capabilities in adverse environments, resolving the strength-adaptability contradiction.
Data Source
AI summary
Embodiments are directed to first and second structural members that are threadingly-engaged with each other. The first and second structural members are dissimilar strength materials. Each structural member configured with a plurality of threads for the threading engagement. The thread thickness of each thread in the plurality of threads for the first structural member is not equal to the thread thickness of each thread in the plurality of threads for the second structural member.