Thermal Load Modeling in Structural Fastened Joints
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Solution Overview
Problem
Current methods for modeling thermal loads in structural fastened joints with dissimilar materials are inefficient, leading to increased safety factors, higher structural weight, reduced payload, and higher costs due to the inability to accurately account for thermal expansion and mechanical response in vehicle design.
Innovation Solution
A method involving physical testing of single shear joints with dissimilar materials to generate load state equations and closed-form equations, using single row joint testing equipment to determine joint parameters and strain data, which allows for the accurate calculation of thermal build-up and stiffness, thereby reducing conservatism in design models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical testing of single shear joints with dissimilar materials is performed to generate accurate load state equations, then modeling precision of thermal loads is improved, but testing time and equipment complexity increase
Solution Approach 1:
The patent segments the joint into a first component, second component, and fastener assembly, allowing independent testing of each component's thermal-mechanical response. This segmentation enables systematic data collection that can be used to develop accurate load state equations without requiring complete joint replacement testing.
Solution Approach 2:
The patent introduces an intermediary testing apparatus that applies controlled thermal and mechanical loads to the joint components. This intermediary system allows precise measurement of strain, stress, and displacement data without requiring complex full-vehicle thermal cycling, thereby reducing testing time while maintaining accuracy.
2Reliability
If conservative safety factors are used in design to account for thermal expansion uncertainties, then structural reliability is improved, but structural weight increases
Solution Approach 1:
The patent employs feedback from physical testing data to refine design calculations. By measuring actual thermal-mechanical response and comparing it with predictive models, the patent enables iterative improvement of design equations, allowing reduced safety factors based on verified performance rather than conservative estimates.
Solution Approach 2:
The patent changes the design approach from using fixed conservative safety factors to using variable parameters derived from actual material and joint testing. By determining specific thermal expansion coefficients, stiffness values, and strength parameters through controlled testing, the patent enables optimized design parameters that maintain reliability while reducing unnecessary weight.
3Measurement precision
If comprehensive thermal load modeling is performed to account for differential thermal expansion, then design accuracy is improved, but computational complexity and cost increase
Solution Approach 1:
The patent extracts the essential thermal-mechanical behavior from complex vehicle-level simulations by focusing testing on representative joint samples. By removing unnecessary computational complexity and concentrating on critical joint regions, the patent achieves accurate design data through targeted physical testing rather than comprehensive simulation.
Solution Approach 2:
The patent creates simplified test specimens that copy the essential features of actual vehicle joints. These scaled-down or simplified joint samples can be tested under controlled conditions to generate data that represents full-vehicle joint behavior, avoiding the need for complex computational modeling of entire vehicle structures.
4Adaptability or versatility
If dissimilar materials with different thermal expansion coefficients are joined, then structural versatility is improved, but differential strain and thermal stress increase
Solution Approach 1:
The patent applies local quality by tailoring the joint design and testing specifically for the combination of dissimilar materials used. By characterizing the thermal-mechanical response of specific material pairs (e.g., metal-to-composite, metal-to-metal with different CTEs) under controlled conditions, the patent enables optimized joint designs that accommodate differential expansion without excessive stress.
Solution Approach 2:
The patent utilizes composite material principles by joining dissimilar materials with complementary properties. The joint design incorporates fasteners and interface treatments that accommodate the different thermal expansion coefficients of the bonded materials, creating a composite joint system that leverages the advantages of each material while mitigating their thermal incompatibility.
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 approach enables more accurate modeling of thermal loads in structural fastened joints, reducing unnecessary weight and cost by providing a more precise analysis of joint behavior, allowing for the creation of thermo-mechanical design curves that reduce conservatism in vehicle design.
Implementation Method 1
Dissimilar materials can have different coefficients of thermal expansion. At joints between two materials of dissimilar properties, a differential strain results as each material will expand or contract proportionally to its respective coefficient of thermal expansion.
Implementation Method 2
The fasteners experience shear forces and normal forces resulting from differential thermal strains and applied mechanical loads
Implementation Method 3
The fasteners experience shear forces and normal forces resulting from differential thermal strains and applied mechanical loads
Data Source
AI summary
Methods of designing a structure taking into account thermal loads are presented. A method to analyze thermal build-up in a joint is presented. Physical testing between a first material and a second material is performed to determine physical data comprising at least one of stiffness, strain, load, and displacement. The physical data is analyzed. A closed form equation is generated based on the analysis to calculate the thermal build-up in the joint.