Mechanical Performance of a Pressure Pipe CIPP Liner with Stress Concentration Effects Associated with Local Defects
Bibliographic record
Abstract
In this study, continuum finite element modelling procedures are used to examine the mechanical response and performance of a cured in place pipe (CIPP) liner for pressure pipe. The external cast iron pipe and internal CIPP liner was modelled using three-dimensional brick (C3D8I) elements with multiple elements through thickness depending on the CIPP liner diameter to wall thickness (D/t) ratio. The modelling procedures were calibrated with available public domain data and the anisotropic material behaviour of the CIPP liner was established using tensile coupon tests data. A parameter study was conducted to assess mechanical performance of a pressure pipe CIPP liner with stress concentration effects due to local defects (e. g. wall voids). The sensitivity study investigated the CIPP liner outside diameter to CIPP wall thickness ratio (D/t), host pipe void diameter to host pipe inside diameter ratio (d/D), hoop stress due to internal pressure to yield stress ratio for the CIPP liner (σh/σy), and CIPP liner/host pipe interface friction coefficient (μ). Performance envelopes were developed that were consistent with current engineering practice and illustrated a class of parameters where an engineering condition assessment would be required to evaluate the CIPP liner performance. Material yield behaviour was observed for the higher liner dimension (D/t > 60) and hoop stress to yield ratios (σh/σy ≥ 0.6). The limit state can be governed by axial tension rather than ring tension when void ratios (d/D) are greater than 0.4. As the void ratio (d/D) increases, the hoop stress tends to behave as an unconstrained liner in the radial direction. The fully bonded interface has a distinct effect of reducing the axial, hoop, and effective stress.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".