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Strain Measurement And Analysis Of Welding Process Based On Digital Image Correlation

Posted on:2024-04-10Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhouFull Text:PDF
GTID:2531306944450804Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
During the welding process,due to the concentration of welding heat source,the temperature field of the welded joint is extremely uneven,further leading to uneven distribution of stress and strain in the welded structures.If there is regional concentration of stress caused by welding after cooling to room temperature,the fatigue performance of the entire structure will be reduced,and there is a risk of structural failure.Measuring and characterizing the strain and stress during the welding process under different welding processes can provide a deeper understanding of the generation,variation,and distribution of welding stress,and associate the welding process with residual stress,providing a basis for subsequent welding process optimization.Besides,it is also necessary to control the welding distortion of thin plates.By predicting the welding distortion and adjusting the welding process to achieve the ideal results,welding the thin plate based on this can obtain smaller or more uniform distortion.This article implemented welding process strain and stress measurement system based on relevant digital image corelation theories,and validated the accuracy of measuring displacement and strain using this system through experimental and numerical methods.Using this system to measure the strain and stress during the welding process of Q235 A thin plate under external constraints,the variation and distribution of strain and stress were analyzed.The results showed that there were significant differences in the variation and distribution of strain and stress at different positions of the welding plate,and the constraints had a significant impact on the formation and distribution of welding strain and stress.Applied the measurement system to measure welding residual stress under different welding procedures,and studied the influence of different welding process parameters on residual stress.The results indicate that reducing welding current,voltage,and welding speed,as well as increasing spot welding constraint points,can reduce residual stress to a certain extent.A regression prediction model for residual stress distribution based on artificial neural networks was established based on the measured residual stress data.Derived a method for converting strain results measured by the measurement system to inherent strain;Based on elastic mechanics and elastic finite element method,the control equation and numerical calculation method of inherent strain finite element were derived to predict welding residual distortion,and compared with the measured distortion.The results indicate that the method used can accurately predict welding residual deformation,and the error between the predicted deformation in the thickness direction of the welding plate edge and the measured deformation is within 1mm,while the error between the predicted and measured edge deflection is within 0.1mm.This article introduces the digital image correlation method into the welding process for strain and stress measurement,and proposes a new method for predicting welding residual distortion by combining the digital image correlation method with the inherent strain method.This provides new possibilities for the study of controlling welding residual stress and distortion.
Keywords/Search Tags:Welding strain, Welding stress, Welding distortion, Digital image correlation
PDF Full Text Request
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