Fast 4D On-the-Fly Tomography for Observation of Advanced Pore Morphology (APM) Foam Elements Subjected to Compressive Loading.

Michal Vopalensky,Petr Koudelka,Daniel Kytyr,Matej Borovinsek,Ivana Kumpova,Matej Vesenjak,Jan Sleichrt

doi:10.3390/ma14237256

Abstract

Observation of dynamic testing by means of X-ray computed tomography (CT) and in-situ loading devices has proven its importance in material analysis already, yielding detailed 3D information on the internal structure of the object of interest and its changes during the experiment. However, the acquisition of the tomographic projections is, in general, a time-consuming task. The standard method for such experiments is the time-lapse CT, where the loading is suspended for the CT scan. On the other hand, modern X-ray tubes and detectors allow for shorter exposure times with an acceptable image quality. Consequently, the experiment can be designed in a way so that the mechanical test is running continuously, as well as the rotational platform, and the radiographic projections are taken one after another in a fast, free-running mode. Performing this so-called on-the-fly CT, the time for the experiment can be reduced substantially, compared to the time-lapse CT. In this paper, the advanced pore morphology (APM) foam elements were used as the test objects for in-situ X-ray microtomography experiments, during which series of CT scans were acquired, each with the duration of 12 s. The contrast-to-noise ratio and the full-width-half-maximum parameters are used for the quality assessment of the resultant 3D models. A comparison to the 3D models obtained by time-lapse CT is provided.

Highlights

To assess the representative mechanical response of the advanced pore morphology (APM) foam elements in compression and its variability, six specimens were subjected to the loading procedure without
The graphs demonstrate the difference in response of the specimens subjected to the time-lapse computed tomography (CT), where the loading is intermittent and the force drops of 10–15% occur due to the release of elastic energy stored in the specimen and the loading device itself causing the measured relaxation effect [23]
The best imaging quality of the 3D volumes was reached in Mode A, where static APM foam element was scanned with 2400 angular steps per 360◦, with the detector resolution of 1944 px × 1536 px

Summary

Introduction

CT has been gaining increasing attention as a powerful method for investigating dynamic processes, such as loading experiments in mechanical testing [1] In these applications, a series of subsequent tomographic scans is acquired during the course of the mechanical experiment. In certain experiments and with appropriate instrumentation, the dynamic process can be observed in discrete load-steps (i.e., suspended for the tomographic scan and continued with the step between two subsequent scans). This method is often referred to as a time-lapse 4D tomography or intermittent 4D tomography [2,3,4,5]

Results

Discussion

Conclusion