pith. sign in

arxiv: 2606.26059 · v1 · pith:CWMPACUUnew · submitted 2026-06-24 · 💻 cs.CV · cs.AI

A welding penetration prediction model for laser welding process based on self-supervised learning using physics-informed neural networks

Pith reviewed 2026-06-25 19:24 UTC · model grok-4.3

classification 💻 cs.CV cs.AI
keywords laser weldingpenetration predictionself-supervised learningphysics-informed neural networkfew-shot learningmolten poolkeyholecontrastive learning
0
0 comments X

The pith

SimPhysNet predicts laser welding penetration at 96.06% accuracy using only 200 labeled images by embedding physical priors via self-supervised contrastive learning.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces SimPhysNet to classify full-penetration states in laser welding when only a small fraction of labeled images is available. It trains on a large unlabeled set by running a physics-informed neural network inside a contrastive learning loop so that features of the molten pool and keyhole become physically consistent. Three image-augmentation tasks further improve robustness before a prototypical-network few-shot stage builds class prototypes from the 200 labeled examples. The resulting classifier reaches 96.06% accuracy, matching conventional supervised models trained on the entire labeled collection. The work therefore removes the main practical obstacle that has kept supervised penetration-prediction systems out of many industrial lines.

Core claim

SimPhysNet embeds physical priors into a contrastive learning framework via a physics-informed neural network to extract features of the molten pool and keyhole from unlabeled images; three image augmentation tasks strengthen generalization; a prototypical-network few-shot stage then constructs class representations from only 200 labeled images and yields 96.06% classification accuracy, comparable to supervised baselines that use the full labeled dataset.

What carries the argument

The physics-informed neural network placed inside the contrastive learning objective that forces extracted features of the molten pool and keyhole to respect known physical constraints before few-shot classification occurs.

If this is right

  • Accurate penetration-state classification becomes feasible in settings where collecting thousands of labeled weld images is impractical.
  • Physical priors about the molten pool and keyhole can be used directly to shape representations learned from unlabeled welding video.
  • Image augmentation tasks inside the self-supervised stage measurably improve generalization on the downstream classification problem.
  • Prototypical networks can form reliable class prototypes from a few hundred labeled examples once the preceding self-supervised stage has run.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same self-supervised-plus-physics pattern could be tested on other vision-based quality-control tasks that obey conservation laws or geometric constraints.
  • If the learned features prove stable across different laser powers or materials, the method would reduce the need for per-process retraining.
  • Real-time deployment would require checking whether the full pipeline runs fast enough on edge hardware typical of welding cells.
  • Direct comparison of the extracted features against established numerical simulations of keyhole dynamics would test whether the physics embedding captures the intended quantities.

Load-bearing premise

The physics-informed neural network produces features from unlabeled images that are sufficiently informative for the downstream few-shot classification task.

What would settle it

An ablation that removes the physics-informed neural network component and measures whether accuracy with the same 200 labels falls substantially below 96% would falsify the claim that the physical priors are responsible for the performance gain.

read the original abstract

The laser welding full-penetration is of critical importance, as it constitutes one of the fundamental factors in achieving defect-free welded joints. Accurate prediction of the penetration state is therefore essential for ensuring weld quality. To this end, this paper introduces SimPhysNet, a novel algorithm that achieves high classification accuracy in laser welding penetration prediction using only a limited number of labelled images. This approach effectively overcomes the limitations of supervised learning classification algorithms, which are hindered in industrial applications by their dependence on extensive, high-quality labelled data. The core of SimPhysNet is a unique self-supervised learning paradigm that embeds physical priors into a contrastive learning framework. By incorporating a physics-informed neural network (PINN), the model is guided to extract physically meaningful features of the molten pool and keyhole from a large set of unlabelled data, while three image augmentation tasks further enhance its generalization capabilities. Subsequently, a few-shot learning strategy, based on prototypical networks, enables robust classification by constructing class representations from a minimal set of labelled images. Experimental results demonstrate that SimPhysNet achieves a classification accuracy of 96.06% using only 200 labelled images (approximately 5% of the total labelled dataset), which is comparable to the performance of conventional supervised learning algorithms that utilize the entire labelled dataset. This work presents a new, efficient, and highly accurate method, providing the way for the intelligent automation of laser welding.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper introduces SimPhysNet, a self-supervised framework that embeds physical priors about the molten pool and keyhole via a physics-informed neural network (PINN) inside a contrastive learning pipeline, followed by prototypical-network few-shot classification. It claims that this yields 96.06% accuracy on laser-welding penetration-state prediction when only 200 labeled images (≈5% of the dataset) are used, matching the performance of fully supervised baselines trained on the entire labeled set.

Significance. If the reported accuracy is reproducible and the contribution of the physics-informed component can be isolated, the approach would materially reduce the labeling burden for industrial weld-quality inspection. The combination of PINN-guided contrastive pretraining with few-shot classification is a plausible route to data-efficient vision models in manufacturing; however, the current manuscript supplies neither the governing equations nor an ablation that isolates the physics term, so the significance remains conditional on those missing elements.

major comments (2)
  1. [Abstract, §3] Abstract and §3 (method): the central performance claim (96.06% with 200 labels) is attributed to the PINN embedding physical priors, yet no equation for the physics loss term, no statement of the governing PDEs or boundary conditions for the molten-pool/keyhole model, and no ablation that removes or replaces the physics loss while keeping the contrastive framework fixed are provided. Without this isolation the attribution cannot be verified.
  2. [§4] §4 (experiments): the comparison to fully supervised baselines is reported only at the aggregate accuracy level; no per-class confusion matrices, no error analysis on the few-shot regime, and no statistical significance test across multiple random splits of the 200-label subset are shown, leaving open whether the result is robust or driven by a favorable split.
minor comments (2)
  1. [§3.2] Notation for the three image-augmentation tasks is introduced without explicit definitions or pseudocode; a short table or algorithm box would improve reproducibility.
  2. [§4.1] The total size of the unlabeled corpus and the precise train/validation/test split ratios are stated only approximately; exact numbers should be given in §4.1.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments, which highlight important areas for clarification and strengthening of the experimental validation. We address each major comment below and will incorporate the suggested additions in the revised manuscript.

read point-by-point responses
  1. Referee: [Abstract, §3] Abstract and §3 (method): the central performance claim (96.06% with 200 labels) is attributed to the PINN embedding physical priors, yet no equation for the physics loss term, no statement of the governing PDEs or boundary conditions for the molten-pool/keyhole model, and no ablation that removes or replaces the physics loss while keeping the contrastive framework fixed are provided. Without this isolation the attribution cannot be verified.

    Authors: We agree that the manuscript does not provide the explicit governing PDEs, boundary conditions, or the mathematical form of the physics loss term, nor does it include an ablation isolating the PINN contribution. In the revision we will add the relevant equations for the molten-pool/keyhole model, the precise formulation of the physics-informed loss, and an ablation study comparing the full SimPhysNet pipeline against an otherwise identical contrastive-learning baseline that omits the physics term. This will enable direct verification of the physics component's role. revision: yes

  2. Referee: [§4] §4 (experiments): the comparison to fully supervised baselines is reported only at the aggregate accuracy level; no per-class confusion matrices, no error analysis on the few-shot regime, and no statistical significance test across multiple random splits of the 200-label subset are shown, leaving open whether the result is robust or driven by a favorable split.

    Authors: We acknowledge that the current experimental section reports only aggregate accuracy and lacks per-class confusion matrices, detailed error analysis for the few-shot regime, and statistical tests over multiple random splits. In the revised manuscript we will include these elements: confusion matrices for the 200-label setting, qualitative and quantitative error analysis, and results aggregated over at least five random splits of the labeled subset together with appropriate significance testing (e.g., paired t-tests). revision: yes

Circularity Check

0 steps flagged

Empirical accuracy claim with no derivation chain reducing to inputs

full rationale

The paper reports an experimental classification accuracy of 96.06% on a few-shot task after self-supervised pretraining. No equations, fitted parameters, or uniqueness theorems are presented whose outputs are defined in terms of the target metric or whose 'predictions' collapse to the training inputs by construction. The performance number is obtained from standard evaluation on labeled data and is not algebraically or statistically forced by the method description itself. The central claim therefore remains an independent empirical observation rather than a self-referential renaming or tautology.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claim rests on the domain assumption that physical priors about molten pool and keyhole dynamics can be incorporated into a neural network to produce useful features from unlabeled images; no free parameters or invented entities are specified in the abstract.

axioms (1)
  • domain assumption Physical priors about the molten pool and keyhole can be effectively incorporated into a neural network to extract meaningful features from unlabelled images.
    This premise underpins the self-supervised learning paradigm described as the core of SimPhysNet.

pith-pipeline@v0.9.1-grok · 5809 in / 1368 out tokens · 39876 ms · 2026-06-25T19:24:28.013871+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

39 extracted references · 34 canonical work pages · 4 internal anchors

  1. [1]

    Wang, S.J

    B. Wang, S.J. Hu, L. Sun, T. Freiheit, Intelligent welding system technologies: State- of-the-art review and perspectives, J. Manuf. Syst. 56 (2020) 373 –391. https://doi.org/10.1016/j.jmsy.2020.06.020

  2. [2]

    W. Cai, J. Wang, P. Jiang, L. Cao, G. Mi, Q. Zhou, Application of sensing techniques and artificial intelligence- based methods to laser welding real- time monitoring: A critical review of recent literature, J. Manuf. Syst. 57 (2020) 1 –18. https://doi.org/10.1016/j.jmsy.2020.07.021

  3. [3]

    S. Kang, S. Jeon, K. Ryu, J. Shin, Online monitoring of weld cross -sectional shape using optical emission spectroscopy and neural network during laser dissimilar welding, Eng. Appl. Artif. Intell. 141 (2025) 109847. https://doi.org/10.1016/j.engappai.2024.109847

  4. [4]

    H. Li, H. Ren, Z. Liu, F. Huang, G. Xia, Y . Long, In-situ monitoring system for weld geometry of laser welding based on multi- task convolutional neural network model, Measurement 204 (2022) 112138. https://doi.org/10.1016/j.measurement.2022.112138

  5. [5]

    Zhang, C

    X. Zhang, C. Wang, Y . Tang, Z. Zhou, X. Lu, A Survey of Few-Shot Learning and Its Application in Industrial Object Detection Tasks, in: Y . Wang, K. Martinsen, T. Yu, K. Wang (Eds.), Lect. Notes Electr. Eng., Springer, Singapore, 2022: pp. 637 –647. https://doi.org/10.1007/978-981-19-0572-8_81

  6. [6]

    Raffin, A

    T. Raffin, A. Mayr, M. Baader, N. Laube, A. Kühl, J. Franke, Potentials of few-shot learning for quality monitoring in laser welding of hairpin windings, Procedia CIRP 118 (2023) 901–906. https://doi.org/10.1016/j.procir.2023.06.155

  7. [7]

    T. Zhu, S. Zhu, J. Zhu, W. Song, C. Li, H. Ge, J. Gu, A Deep Meta-Metric Learning Method for Few-Shot Weld Seam Visual Detection, in: 2022 IEEE Int. Conf. Robot. Biomim. ROBIO, 2022: pp. 1167–1173. https://doi.org/10.1109/ROBIO55434.2022.10012017

  8. [8]

    Q. Liu, R. Xiao, Y . Xu, J. Xu, S. Chen, A defect classification algorithm for gas tungsten arc welding process based on unsupervised learning and few -shot learning strategy, J. Manuf. Process. 131 (2024) 1219–1229. https://doi.org/10.1016/j.jmapro.2024.09.084

  9. [9]

    S. Chen, T. Li, F. Jiang, G. Zhang, S. Fang, Enhancing VPPA welding quality prediction: A hybrid model integrating prior physical knowledge and CNN analysis, J. Manuf. Process. 131 (2024) 1282–1295. https://doi.org/10.1016/j.jmapro.2024.09.089

  10. [10]

    R. Lu, M. Lou, Y . Xia, Y . Li, Real-time penetration depth prediction via physics- informed learning from molten pool surface morphology in laser filler wire welding, J. Intell. Manuf. (2025). https://doi.org/10.1007/s10845-025-02738-7

  11. [11]

    X. Li, Z. Fu, J. Shu, B. Ji, B. Ji, A modified physics -informed neural network to fatigue life prediction of deck -rib double-side welded joints, Int. J. Fatigue 189 (2024) 108566. https://doi.org/10.1016/j.ijfatigue.2024.108566

  12. [12]

    Gianfrancesco, Materials for Ultra -Supercritical and Advanced Ultra- Supercritical Power Plants, Woodhead Publishing, 2016

    A.D. Gianfrancesco, Materials for Ultra -Supercritical and Advanced Ultra- Supercritical Power Plants, Woodhead Publishing, 2016

  13. [13]

    X. Chen, K. He, Explo ring Simple Siamese Representation Learning, (2020). https://doi.org/10.48550/arXiv.2011.10566

  14. [14]

    K. He, X. Zhang, S. Ren, J. Sun, Deep Residual Learning for Image Recognition, in: 2016: pp. 770–778. https://doi.org/10.1109/CVPR.2016.90

  15. [15]

    Behúlová, E

    M. Behúlová, E. Babalová, Heat source models for numerical simulation of laser welding processes – a short review, J. Phys. Conf. Ser. 2712 (2024) 012018. https://doi.org/10.1088/1742-6596/2712/1/012018

  16. [16]

    Hartwig, L

    P. Hartwig, L. Scheunemann, J. Schröder, On the numerical treatment of heat sources in laser beam welding processes, PAMM 23 (2023) e202200220. https://doi.org/10.1002/pamm.202200220

  17. [17]

    Liang, G

    G. Liang, G. Qin, P. Cao, H. Wang, Evolutions of temperature field and stress field in narrow gap oscillating laser welding process based on equivalent heat source, J. Mater. Res. Technol. 28 (2024) 154–167. https://doi.org/10.1016/j.jmrt.2023.11.262

  18. [18]

    S. Wang, S. Sankaran, H. Wang, P. Perdikaris, An Expert’s Guide to Training Physics-informed Neural Networks, (2023). https://doi.org/10.48550/arXiv.2308.08468

  19. [19]

    W. Guo, F. Deng, Z. Meng, L. Hua, H. Mao, J. Su, A hybrid back-propagation neural network and intelligent algorithm combined algorithm for optimizing microcellular foaming injection molding process parameters, J. Manuf. Process. 50 (2020) 528 –538. https://doi.org/10.1016/j.jmapro.2019.12.020

  20. [20]

    Huntington, C.S

    D.E. Huntington, C.S. Lyrintzis, Improvements to and limitations of Latin hypercube sampling, Probabilistic Eng. Mech. 13 (1998) 245– 253. https://doi.org/10.1016/S0266-8920(97)00013-1

  21. [21]

    An overview of gradient descent optimization algorithms

    S. Ruder, An overview of gradient descent optimization algorithms, (2017). https://doi.org/10.48550/arXiv.1609.04747

  22. [22]

    Cover, P

    T. Cover, P. Hart, Nearest neighbor pattern classification, IEEE Trans. Inf. Theory 13 (1967) 21–27. https://doi.org/10.1109/TIT.1967.1053964

  23. [23]

    K. He, H. Fan, Y . Wu, S. Xie, R. Girshick, Momentum Contrast for Unsupervised Visual Representation Learning, (2020). https://doi.org/10.48550/arXiv.1911.05722

  24. [24]

    X. Chen, H. Fan, R. Girshick, K. He, Improved Baselines with Momentum Contrastive Learning, (2020). https://doi.org/10.48550/ARXIV .2003.04297

  25. [25]

    Grill, F

    J.-B. Grill, F. Strub, F. Altché, C. Tallec, P.H. Richemond, E. Buchatskaya, C. Doersch, B.A. Pires, Z.D. Guo, M.G. Azar, B. Piot, K. Kavukcuoglu, R. Munos, M. Valko, Bootstrap your own latent: A new approach to self -supervised Learning, (2020). https://doi.org/10.48550/arXiv.2006.07733

  26. [26]

    T. Chen, S. Kornblith, M. Norouzi, G. Hinton, A Simple Framework for Contrastive Learning of Visual Representations, (2020). https://doi.org/10.48550/arXiv.2002.05709

  27. [27]

    T. Chen, S. Kornblith, K. Swersky, M. Norouzi, G.E. Hinton, Big Self- Supervised Models are Strong Semi-Supervised Learners, in: Adv. Neural Inf. Process. Syst., Curran Associates, Inc., 2020: pp. 22243 –22255. https://proceedings.neurips.cc/paper/2020/hash/fcbc95ccdd551da181207c0c1400c655- Abstract.html (accessed August 14, 2025)

  28. [28]

    and Cogswell, Michael and Das, Abhishek and Vedantam, Ramakrishna and Parikh, Devi and Batra, Dhruv , year=

    R.R. Selvaraju, M. Cogswell, A. Das, R. Vedantam, D. Parikh, D. Batra, Grad- CAM: Visual Explanations from Deep Networks via Gradient- based Localization, Int. J. Comput. Vis. 128 (2020) 336–359. https://doi.org/10.1007/s11263-019-01228-7

  29. [29]

    Vinyals, C

    O. Vinyals, C. Blundell, T. Lillicrap, Matching Networks for One Shot Learning, (n.d.)

  30. [30]

    Snell, K

    J. Snell, K. Swersky, R. Zemel, Prototypical Networks for Few- shot Learning, in: Adv. Neural Inf. Process. Syst., Curran Associates, Inc., 2017. https://proceedings.neurips.cc/paper_files/paper/2017/hash/cb8da6767461f2812ae4290eac7 cbc42-Abstract.html (accessed July 2, 2025)

  31. [31]

    F. Sung, Y . Yang, L. Zhang, T. Xiang, P.H.S. Torr, T.M. Hospedales, Learning to Compare: Relation Network for Few -Shot Learning, in: 2018 IEEECVF Conf. Comput. Vis. Pattern Recognit., 2018: pp. 1199–1208. https://doi.org/10.1109/CVPR.2018.00131

  32. [32]

    Medina, A

    C. Medina, A. Devos, M. Grossglauser, Self -Supervised Prototypical Transfer Learning for Few-Shot Classification, (2020). https://doi.org/10.48550/arXiv.2006.11325

  33. [33]

    J.-C. Su, S. Maji, B. Hariharan, When Does Self-supervision Improve Few-shot Learning?, (2020). https://doi.org/10.48550/arXiv.1910.03560

  34. [34]

    Y . An, H. Xue, X. Zhao, L. Zhang, Conditional Self -Supervised Learning for Few-Shot Classification, in: Proc. Thirtieth Int. Jt. Conf. Artif. Intell., International Joint Conferences on Artificial Intelligence Organization, Montreal, Canada, 2021: pp. 2140–2146. https://doi.org/10.24963/ijcai.2021/295

  35. [35]

    UMAP: Uniform Manifold Approximation and Projection for Dimension Reduction

    L. McInnes, J. Healy, J. Melville, UMAP: Uniform Manifold Approximation and Projection for Dimension Reduction, (2020). https://doi.org/10.48550/arXiv.1802.03426

  36. [36]

    Cortes, V

    C. Cortes, V . Vapnik, Support-vector networks, Mach. Learn. 20 (1995) 273–

  37. [37]

    https://doi.org/10.1007/BF00994018

  38. [38]

    Machine Learning , author=

    L. Breiman, Random Forests, Mach. Learn. 45 (2001) 5 –32. https://doi.org/10.1023/A:1010933404324

  39. [39]

    T. Chen, C. Guestrin, XGBoost, in: Proc. 22nd ACM SIGKDD Int. Conf. Knowl. Discov. Data Min., 2016: pp. 785–794. https://doi.org/10.1145/2939672.2939785