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Dissolution driven crack branching in polycarbonate
Malmö högskola, School of Technology (TS).
Malmö högskola, School of Technology (TS).ORCID iD: 0000-0002-7952-5330
2011 (English)In: Fatigue and Fracture of Engineering Materials and Structures, Vol. 34, no 4, p. 227-239Article in journal (Refereed) Published
Abstract [en]

Stress corrosion, in the form of chemically assisted crack growth, in polycarbonate is examined with focus on crack branching characteristics. Cracks with finite width are observed; this is to be expected for dissolution driven cracking. The cracks branched repeatedly and crack widths before and after branching are measured. Both symmetric and asymmetric branching is found. The dissolution rate is assumed to be a linear function of the strain along the crack surface. In the literature, it is proposed that the crack width is proportional to the square of the mode I stress intensity factor. Energy considerations lead to that the sum of branch widths must equal the width of the unbranched crack. The results from the present study correspond fairly well with this assumption. The branching angle is found to be 32º ± 12º, which is in line with results for sharp cracks reported in the literature. The mean growth direction of the branches is found to deviate slightly from the expected straight. No significant correlation between angles and crack widths is found. The scatter in results is mainly addressed to the inherent perturbation sensitivity of stress corrosion cracking. Also numerically simulations of crack branching is performed. These results show promising agreement with the experiments.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2011. Vol. 34, no 4, p. 227-239
Keywords [en]
stress corrosion cracking, polycarbonate, dissolution, branching, experiment, finite element modelling
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:mau:diva-2284DOI: 10.1111/j.1460-2695.2010.01508.xISI: 000288127600001Scopus ID: 2-s2.0-79952555249Local ID: 10397OAI: oai:DiVA.org:mau-2284DiVA, id: diva2:1399037
Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2024-03-04Bibliographically approved
In thesis
1. On initiation of chemically assisted crack growth and crack propagation paths of branching cracks in polycarbonate
Open this publication in new window or tab >>On initiation of chemically assisted crack growth and crack propagation paths of branching cracks in polycarbonate
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Stress corrosion, SC, in some cases gives rise to stress corrosion cracking, SCC, which differs from purely stress intensity driven cracks in many aspects. They initiate and grow under the influence of an aggressive environment in a stressed substrate. They grow at low load and may branch. The phenomenon of SCC is very complex, both the initiation phase and crack extension itself of SCC is seemingly associated with arbitrariness due to the many unknown factors controlling the process. Such factors could be concentration of species in the environment, stress, stress concentration, electrical conditions, mass transport, and so on.In the present thesis, chemically assisted crack initiation and growth is studied with special focus on the initiation and branching of cracks. Polycarbonate plates are used as substrates subjected to an acetone environment. Experimental procedures for examining initiation and branching in polycarbonate are presented. An optical microscope is employed to study the substrate.The attack at initiation is quantified from pits found on the surface, and pits that act as origin for cracks is identified and the distribution is analysed. A growth criterion for surface cracks is formulated from the observations, and it is used to numerically simulate crack growth. The cracks are seen to coalesce, and this phenomenon is studied in detail. Branching sites of cracks growing in the bulk of polycarbonate are inspected at the sample surface. It is found that the total width of the crack branches are approximately the same as the width of the original crack. Also, angles of the branches are studied. Further, for comparison the crack growth in the bulk is simulated using a moving boundary problem based algorithm and similar behaviour of crack branching is found.

Place, publisher, year, edition, pages
Ulf Hejman/Media-Tryck AB, 2010. p. 77
Keywords
stress corrosion, crack initiation, multiple cracking, polycarbonate, three point bending, stress corrosion cracking, polycarbonate, dissolution, branching, experiment, finite element modelling
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:mau:diva-7790 (URN)9955 (Local ID)978-91-633-6462-4 (ISBN)9955 (Archive number)9955 (OAI)
Note

Both papers in thesis as manuscript, paper II with title "Branching cracks in a layered material - Dissolution driven crack growth in polycarbonate"

Available from: 2020-02-28 Created: 2020-02-28 Last updated: 2024-03-04Bibliographically approved

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Hejman, UlfBjerkén, Christina

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