A stress analysis method for fatigue life prediction of welded structures
Bibliographic record
Abstract
In the case of structural weldments, the procedure for estimating fatigue life requires information concerning geometry of the object, loads and material. Detailed knowledge of stress fields in the critical regions of weldments is used to determine the fatigue life. The main theme of the research discussed in this thesis is to provide details of the methodology which has been developed to determine peak stress and associated non-linear through thickness stress distribution at the critical weld toe location by using only the geometry dependent stress concentration factors along with appropriate unique reference stress calculated in an efficient manner e.g. without modeling geometrical weld toe details. The peak stress at the weld toe can be subsequently used for estimating the fatigue crack initiation life. The non-linear through thickness stress distribution and the weight function method can be used for the determination of stress intensity factors and for the analysis of subsequent fatigue crack growth. \nAccurate peak stress estimation requires 3D fine mesh finite element (FE) models, accounting for the micro-geometrical features, such as the weld toe angle and weld toe radius. Such models are computationally expensive and therefore impractical. On the other hand, stresses at sharp weld corners obtained from 3D coarse FE meshes are inaccurate and cannot be used directly for fatigue life estimations. A robust, sufficiently accurate, efficient and practical approach is proposed for fatigue life estimation of welded structures based on 3D coarse mesh FE models. \nAnother objective is to establish a methodology which is capable of accounting for the actual variability of stress concentration factors at welds, welding defects such as misalignment and incomplete penetration resulting from manufacturing processes. The proposed approach is capable of accounting for the effects from use of different material and effect of residual stresses from welding process. Residual stress information is obtained from a welding process simulation model, which has been validated against measured residual stress data. \nThe proposed methodology has been validated using numerical and experimental data by analyzing different weldments of varying geometrical and load configurations. \nFurther, the applicability of the stress field obtained from the proposed methodology is demonstrated by using it in a forward looking “Total Fatigue Life” concept based only on the fracture mechanics approach.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".