Spot Weld Nugget Diameter Estimation Using Resistance and Expansion
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Solution Overview
Problem
Existing methods for estimating nugget diameter in resistance spot welding lack accuracy, particularly when the nugget does not reach the interface between metal plates, leading to low-accuracy calculations.
Innovation Solution
An estimation method that includes processes for estimating nugget thickness and diameter using expansion and contraction amounts, along with electric resistance values, to improve accuracy by determining when the nugget reaches the interface and using these parameters in equations to calculate the nugget dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical quantity measurement during welding is used to estimate nugget diameter, then actual measurement is avoided, but estimation accuracy is insufficient when nugget does not reach interface
Solution Approach 1:
The patent changes the parameters used for estimation from simple physical quantity measurements to a combination of expansion amount, contraction amount, and electric resistance value. By monitoring how these parameters change throughout the welding process, the system can determine whether the nugget has reached the interface and provide accurate diameter estimation only in that case, thus resolving the reliability issue.
Solution Approach 2:
The patent implements feedback by continuously monitoring the expansion amount, contraction amount, and electric resistance value during welding, and using this real-time data to determine nugget interface reach status. This feedback mechanism allows the system to adapt the estimation process based on actual welding conditions, improving both accuracy and reliability.
2Ease of manufacture
If nugget diameter is calculated without verifying interface reach, then calculation is simpler, but estimation accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by determining whether the nugget has reached the interface before performing diameter calculation. The system first monitors expansion and contraction amounts along with electric resistance values to assess interface reach status, and only then proceeds with diameter estimation. This preliminary verification step ensures accuracy while maintaining reasonable calculation complexity.
3Device complexity
If only expansion amount and electric resistance value are used for thickness estimation, then measurement process is simpler, but nugget dimension estimation accuracy is limited
Solution Approach 1:
The patent merges multiple measurement parameters (expansion amount, contraction amount, and electric resistance value) into a unified estimation process. By combining these parameters and analyzing their relationships, the system achieves accurate estimation of both nugget thickness and diameter while maintaining a relatively simple measurement process that uses existing welding monitoring data.
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 method enhances the accuracy of nugget diameter estimation by excluding low-accuracy calculations and incorporating contraction amounts, resulting in improved correlation with actual nugget dimensions and welding quality assessment.
Implementation Method 1
the vicinity of the surface to be bonded of each metal plate is melted by heat generation caused by energization
Implementation Method 2
the molten metal plates solidify, and the metal plates are welded
Data Source
AI summary
Resistance spot welding includes a first process of performing energization by pressurizing two or more metal plates superposed by sandwiching a pair of electrode tips, and a second process of stopping energization in the first process and pressurizing two or more metal plates by a pair of electrode tips. The estimation method for the nugget diameter includes: a thickness estimation process of estimating the nugget thickness using the amount of expansion in the thickness direction of two or more metal plates in the first process and the electric resistance value between the pair of electrode tips in the first process; and a diameter estimation process of estimating the nugget diameter using the expansion amount and the electric resistance value when the nugget is estimated to have reached the interface between two adjacent metal plates using the respective thicknesses of the two or more metal plates and the estimated nugget thickness.