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arxiv: 2605.22627 · v1 · pith:AOTDYDDJnew · submitted 2026-05-21 · 💻 cs.HC · cond-mat.mtrl-sci

Summarizing Time-Varying Digital Image Correlation Strain Fields Using Sankey Diagrams

Victor Persson , Christofer Boo , Mohit Sharma , Ingrid Hotz This is my paper

Pith reviewed 2026-05-22 03:41 UTC · model grok-4.3

classification 💻 cs.HC cond-mat.mtrl-sci
keywords digital image correlationSankey diagramstrain localizationvisual analyticstime series summarizationmaterial testingdeformation analysis
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The pith

Sankey diagrams summarize the evolution of high-strain regions in time-resolved DIC data by tracking connected components via spatial overlap.

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

Digital image correlation produces dense time series of surface strain but frame-by-frame viewing hides overall patterns. This work builds a single Sankey diagram from superlevel sets of the von Mises strain field. Connected components are followed across frames using spatial overlap to record when strain concentrations appear, stay, combine, or fade. Tests on four tensile specimens with different notches demonstrate that the diagram distinguishes deformation regimes and shows early signs of failure. The result is a global temporal summary that pairs with conventional spatial plots.

Core claim

The paper claims that a Sankey diagram constructed by identifying connected components in superlevel sets of the von Mises equivalent strain field and linking them over time through spatial overlap can encode the birth, persistence, merging, and disappearance of strain concentrations. When applied to tensile test data with varying notch geometries, this representation compactly reveals differences in deformation behavior and qualitative indicators of impending failure.

What carries the argument

A Sankey diagram whose flows represent the temporal tracking of connected components of high-strain superlevel sets, linked by spatial overlap between consecutive frames.

If this is right

  • The diagram distinguishes deformation regimes across different notch geometries.
  • It identifies qualitative precursors to failure in the strain evolution.
  • It provides a global temporal overview that complements traditional spatial visualizations.
  • Birth, persistence, merging, and disappearance of strain concentrations are explicitly encoded.

Where Pith is reading between the lines

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

  • If the spatial-overlap tracking proves robust, similar Sankey summaries could be applied to other time-dependent field data such as temperature or displacement fields in material science.
  • The method might support automated detection of critical strain events by analyzing flow patterns in the diagram.
  • Extensions could incorporate uncertainty from DIC measurements into the component tracking to improve reliability.

Load-bearing premise

Tracking connected components of superlevel sets solely by spatial overlap between consecutive frames accurately captures the physical evolution of strain concentrations without significant errors from rapid changes or measurement noise.

What would settle it

A sequence of DIC frames in which a strain concentration moves faster than the frame rate or splits in ways not captured by simple overlap would produce incorrect flows in the Sankey diagram, disproving the method's reliability.

Figures

Figures reproduced from arXiv: 2605.22627 by Christofer Boo, Ingrid Hotz, Mohit Sharma, Victor Persson.

Figure 1
Figure 1. Figure 1: Visualization pipeline. Time-resolved DIC strain fields are processed per frame to compute the von Mises equivalent strain. LIC [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Calculating point-wise strain from a deformation field [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: Dataset 3—Comparison across threshold parameters [PITH_FULL_IMAGE:figures/full_fig_p003_5.png] view at source ↗
Figure 3
Figure 3. Figure 3: Dataset 4–Top: Tensor LIC of the principal strain direc [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 6
Figure 6. Figure 6: Temporal region tracking using sample overlaps [PITH_FULL_IMAGE:figures/full_fig_p003_6.png] view at source ↗
Figure 4
Figure 4. Figure 4: Dataset 4—Comparison across persistence parameters [PITH_FULL_IMAGE:figures/full_fig_p003_4.png] view at source ↗
Figure 7
Figure 7. Figure 7: Minimizing link crossings using the barycenter heuristic [PITH_FULL_IMAGE:figures/full_fig_p004_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: All four experimental specimens are shown before and after failure, together with Sankey diagrams illustrating strain evolution [PITH_FULL_IMAGE:figures/full_fig_p005_8.png] view at source ↗
read the original abstract

Digital Image Correlation (DIC) enables dense, time-resolved measurement of surface strain in deforming materials, providing insight into strain localization and failure mechanisms. However, the resulting strain fields are typically explored frame-by-frame through spatial visualizations, making global temporal patterns difficult to discern. We present a visual summarization approach that represents the evolution of high-strain regions as a single Sankey diagram constructed from superlevel sets of the von Mises equivalent strain field. By tracking connected components over time via spatial overlap, the diagram encodes the birth, persistence, merging, and disappearance of strain concentrations. Applied to four tensile test datasets with varying notch geometries, the approach compactly captures differences in deformation regimes and qualitative precursors to failure, complementing traditional spatial strain visualizations with a global temporal overview.

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 manuscript proposes a visual summarization method for time-varying DIC strain fields that builds Sankey diagrams from superlevel sets of the von Mises equivalent strain. Connected components are tracked across frames solely by spatial overlap to encode birth, persistence, merging, and disappearance events. The approach is demonstrated on four tensile-test datasets with varying notch geometries, with the claim that it compactly reveals differences in deformation regimes and qualitative precursors to failure.

Significance. If the spatial-overlap tracking proves robust, the method would supply a compact global temporal view that complements frame-by-frame spatial plots, potentially helping materials researchers quickly compare strain-localization histories across specimens. The construction is direct and non-circular, with no free parameters beyond the single von Mises threshold and no invented entities.

major comments (2)
  1. [Abstract / tracking procedure] Abstract and method description: the central claim that spatial-overlap tracking of superlevel-set components 'faithfully represents physical strain-concentration dynamics' is load-bearing yet unsupported by any sensitivity study on threshold choice, frame rate, or noise level, nor by comparison to advection-based trackers such as optical flow or level-set methods.
  2. [Application to tensile-test datasets] Application section: the assertion that the diagrams 'compactly capture differences in deformation regimes and qualitative precursors to failure' rests on four unquantified examples; no error metrics, inter-rater agreement, or comparison against conventional strain-history plots are supplied to substantiate the summarization benefit.
minor comments (2)
  1. Notation for the von Mises threshold and the overlap criterion should be defined explicitly with a symbol or equation rather than left implicit.
  2. Figure captions could state the exact strain threshold and number of frames used for each Sankey diagram to improve reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed review. The comments help clarify the scope and presentation of our visualization approach. Below we respond point by point to the major comments and indicate the revisions we have made or will make in the next version of the manuscript.

read point-by-point responses

  1. Referee: [Abstract / tracking procedure] Abstract and method description: the central claim that spatial-overlap tracking of superlevel-set components 'faithfully represents physical strain-concentration dynamics' is load-bearing yet unsupported by any sensitivity study on threshold choice, frame rate, or noise level, nor by comparison to advection-based trackers such as optical flow or level-set methods.

    Authors: We acknowledge that the manuscript does not include a formal sensitivity study or direct comparison against optical-flow or level-set trackers. The spatial-overlap method was chosen precisely because it is parameter-free beyond the single von Mises threshold and avoids introducing advection assumptions that may not hold for discrete DIC frames. We have revised the abstract and method section to remove any implication of physical fidelity and instead emphasize that the tracking provides a compact, interpretable encoding of topological events (birth, merge, disappearance) for summarization purposes. A short paragraph discussing threshold sensitivity on the provided datasets has been added, along with a note that more advanced trackers could be compared in future work. We believe these changes address the concern without altering the core contribution. revision: partial

  2. Referee: [Application to tensile-test datasets] Application section: the assertion that the diagrams 'compactly capture differences in deformation regimes and qualitative precursors to failure' rests on four unquantified examples; no error metrics, inter-rater agreement, or comparison against conventional strain-history plots are supplied to substantiate the summarization benefit.

    Authors: The four tensile-test cases are presented as illustrative demonstrations rather than a statistical validation study. To strengthen the claim, we have added direct visual comparisons between the Sankey diagrams and conventional per-frame strain plots plus cumulative strain-history curves for each specimen. These additions show how the single diagram condenses information that would otherwise require inspecting dozens of spatial maps. Because the contribution is a visualization technique rather than a predictive model, quantitative error metrics or inter-rater studies are not applicable; however, we now explicitly discuss the qualitative interpretability gains for materials researchers comparing localization histories across geometries. revision: yes

Circularity Check

0 steps flagged

Direct algorithmic construction from input strain fields; no circular reduction

full rationale

The paper describes a visualization pipeline that extracts superlevel sets from von Mises strain fields, identifies connected components, and tracks them across frames solely by spatial overlap to build a Sankey diagram. This is a standard image-processing construction applied directly to the DIC input data. No parameters are fitted to outputs, no predictions are claimed that reduce to the inputs by definition, and no self-citations or uniqueness theorems are invoked as load-bearing steps. The method is self-contained and does not derive any result equivalent to its own inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The method depends on standard assumptions from image processing and materials visualization; specific implementation parameters such as strain thresholds are not detailed in the abstract.

free parameters (1)
  • von Mises strain threshold for superlevel sets
    Defines which regions count as high-strain concentrations; choice directly affects the Sankey diagram but is not specified in the abstract.
axioms (1)
  • domain assumption Spatial overlap between connected components in consecutive frames reliably tracks the identity and evolution of strain regions
    This assumption underpins the construction of the Sankey diagram from frame to frame.

pith-pipeline@v0.9.0 · 5664 in / 1234 out tokens · 51137 ms · 2026-05-22T03:41:24.820910+00:00 · methodology

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Reference graph

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