Spot Weld Failure Determination Using Solid Element Clusters
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Solution Overview
Problem
Current finite element analysis methods for simulating spot welds in structures, such as cars, are inadequate as they rely on traditional beam elements that are insufficient for accurate modeling and fail to consistently predict spot weld failure, especially in car crashworthiness simulations where solid elements are used.
Innovation Solution
Representing each spot weld by a cluster of solid elements in a finite element analysis model, allowing for arbitrary tie-connection locations between shell elements, and using a failure criterion that accounts for shear and axial stresses, strain rate effects, and sensitivity to shell element size and location, to determine spot weld failure in a time-marching simulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional beam elements are used to model spot welds, then the modeling process is simpler, but the accuracy of spot weld failure prediction deteriorates
Solution Approach 1:
The patent changes the fundamental parameter of element type from beam to solid elements. This transformation allows the model to capture three-dimensional stress states and complex failure modes that beam elements cannot represent, thereby improving failure prediction accuracy while maintaining computational feasibility through optimized solid element formulations
Solution Approach 2:
The patent employs a composite modeling approach where solid elements representing the spot weld nugget are integrated with shell elements representing the sheet metal. This composite structure allows different material behaviors and failure criteria to be applied to different regions, improving overall model accuracy without excessive complexity
2Measurement precision
If solid elements are used to model spot welds, then the accuracy of failure prediction improves, but the computational complexity increases
Solution Approach 1:
The patent segments the spot weld representation into a cluster of solid elements rather than using a single monolithic element. This segmentation allows for better stress distribution calculation and failure prediction while keeping the total element count manageable, thus balancing accuracy with computational efficiency
Solution Approach 2:
The solid element cluster formulation is designed to be universal, working with various shell element types and configurations. This multi-functionality allows the same solid element approach to handle different spot weld geometries, loading conditions, and failure modes without requiring separate specialized models, reducing overall computational complexity
3Quantity of substance
If beam elements are used for spot welds, then the model size remains manageable, but the consistency with solid element failure methods deteriorates
Solution Approach 1:
The patent applies homogeneity by using the same solid element type and failure criterion formulation for both beam-element-replacement cases and traditional solid element cases. This ensures consistent stress calculation methods and failure prediction approaches across all spot weld models, eliminating methodological inconsistencies while maintaining manageable model sizes through optimized element formulations
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~4
AI summary
Each spot weld (110a-n) in a structure (100) is represented by a cluster of at least one solid element in a finite element analysis model of the structure. Each spot weld (110a-n) is used for tying together two parts (122,124). Each of the two parts (122,124) are generally represented or modeled as a number of two-dimension shell elements. Since the tie-connection between the spot weld (110a-n) and the two parts (122,124) can be located arbitrarily within the respective part (122,124), the shell elements representing the two parts (122,124) do not have to be aligned in space. The only requirement is the two shell elements must be overlapped each other such that the spot weld (110a-n) can tie the two shell elements (i.e., one from each part) together. A spot weld failure criterion used for determining failure including shear and axial stresses acted on the spot weld (110a-n), shell element size and spot weld (110a-n) location sensitivity scale factors and strain rate effect.