A technique for in situ X-ray computed tomography of deformation-induced cavitation in thermoplastics

Olufsen, Sindre Nordmark; Tekseth, Kim Robert; Breiby, Dag W.; Clausen, Arild Holm; Hopperstad, Odd Sture

doi:10.1016/j.polymertesting.2020.106834

Cited by 5 publications

(4 citation statements)

References 29 publications

(69 reference statements)

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“…As mentioned in the introduction and stated by literature, many damage mechanisms are accompanied by an increase in volume. [13,15,16,19] To capture such effects, a normalized volume element, V norm , was calculated from the engineering strains in all three spatial directions (Equation 6and Figure 3A). These strains were captured in DIC measurements using virtual extensometers (Figure A2B), whereas the load was applied in the y-direction in all experiments.…”

Section: Volume Change As Sign Of Damage Onsetmentioning

confidence: 99%

“…Additionally, viscoelastic effects and irreversible deformation could not be easily distinguished as source of ε res . Some sources [19] suggest to prestrain the samples and continue characterization after a thorough relaxation period.…”

Section: A13 | Determination Of Modulus In Cyclic Testsmentioning

confidence: 99%

“…As a consequence, additional volume is created. [13,15,16,19] Voids and crazes do not close on their own and crack healing is unlikely for most materials, especially if the glass transition temperature is significantly above room temperature. Thus, an irreversible change in volume is expected on the microscale.…”

mentioning

confidence: 99%

“…To determine the void volume fraction, X-ray tomography scans or scanning electron microscopy (SEM) on cryofractured specimens are an option. [8,19] These methods have to be employed sometime after testing though, so that the majority of relaxation processes is already completed. Comparable in situ measurements are challenging and suffer from various limitations.…”

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confidence: 99%

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Characterization methods for strain‐induced damage in polypropylene

Wiener

Preissegger

Plank

et al. 2022

Polymer Engineering & Sci

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Various methods are used to characterize the deterioration of mechanical properties in polymers. The focus is set on distinguishing between time‐dependent and irreversible damage in two different grades of polypropylene. First, digital image correlation is utilized to capture the stress–strain behavior during monotonic tensile tests. Changes in specimen volume are recorded throughout the experiment and serve as an indicator for crazes and voids. However, the elastic modulus, E, cannot be monitored throughout the entire experiment. Further analysis is performed in the form of cyclic load–unload tests. E and the residual strain, εres, as a function of the applied strain, εappl, are obtained for each cycle. Results show that E primarily suffers from the time‐dependent behavior of the tested polymers in this case. Subsequently, an alternative technique is applied, where specimens are prestrained and then allowed to relax. In the following dynamic mechanical analysis, viscoelastic effects can be avoided. Considerations on the onset and evolution of damage are made. Ultimately, these results are confirmed through microcomputed tomography, where the shapes and densities of defects are captured in high resolution.

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Section: Volume Change As Sign Of Damage Onsetmentioning

confidence: 99%

Section: A13 | Determination Of Modulus In Cyclic Testsmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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