Optical measurement of crack propagation with high resolution

1993 ◽  
Vol 64 (7) ◽  
pp. 1822-1824 ◽  
Author(s):  
H. Koizumi ◽  
K. Kuroda ◽  
T. Suzuki
Keyword(s):  
High Resolution ◽  
Crack Propagation ◽  
Optical Measurement

scholarly journals Dynamic crack propagation in weak snowpack layers: Insights from high-resolution, high-speed photography

2021 ◽  
Author(s):  
Bastian Bergfeld ◽  
Alec van Herwijnen ◽  
Benjamin Reuter ◽  
Grégoire Bobillier ◽  
Jürg Dual ◽  
...  
Keyword(s):  
High Resolution ◽  
Crack Propagation ◽  
Fracture Energy ◽  
High Speed ◽  
Image Correlation ◽  
Crack Speed ◽  
Specific Fracture Energy ◽  
Weak Layer ◽  
Specific Fracture ◽  
Insight Into

Abstract. To assess snow avalanche release probability, information on failure initiation and crack propagation in weak snowpack layers underlying cohesive slab layers are required. With the introduction of the Propagation Saw Test (PST) in the mid-2000s, various studies used particle tracking analysis of high-speed video recordings of PST experiments to gain insight into crack propagation processes, including slab bending, weak layer collapse, crack propagation speed and the frictional behavior after weak layer fracture. However, the resolution of the videos and the methodology used did not allow insight into dynamic processes such as the evolution of crack speed within a PST or the touchdown distance, which is the length from the crack tip to the trailing point where the slab sits on the crushed weak layer at rest again. Therefore, to study the dynamics of crack propagation we recorded PST experiments using a powerful portable high-speed camera with a horizontal resolution of 1280 pixels at rates up to 20,000 frames per second. By applying a high-density speckling pattern on the entire PST column, we then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer, and substrate. The high frame rates allowed time derivatives to obtain velocity and acceleration fields. On the one hand, we demonstrate the versatile capabilities and accuracy of the DIC method by showing three PST experiments resulting in slab fracture, crack arrest and full propagation. On the other hand, we present a methodology to determine relevant characteristics of crack propagation: the crack speed and touchdown distance within a PST, and the specific fracture energy of the weak layer. To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy we used a recently proposed mechanical model. A comparison to already established methods showed good agreement. Furthermore, our methodology also provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.

scholarly journals PARTICLE DEPOSITION STUDY IN A HORIZONTAL SQUARE CHANNEL USING HIGH-RESOLUTION IMAGING

2021 ◽  
Vol 247 ◽  
pp. 10011
Author(s):  
D. Orea ◽  
R. Chavez ◽  
D.T. Nguyen ◽  
R. Vaghetto ◽  
N. K. Anand ◽  
...  
Keyword(s):  
High Resolution ◽  
Particle Deposition ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Wall Surface ◽  
Ongoing Research ◽  
Square Channel ◽  
Resolution Imaging

The ongoing research at Texas A&M University (TAMU) aims to develop and implement measurement techniques to quantify fission product transport and related phenomena in a Gas-Cooled Fast Reactor (GCFR). This study summarizes the experimental measurements performed in a Proof-of-Concept Facility (PCF) to understand particle transport under various Reynolds numbers. Using high-resolution high-magnification optical measurement techniques, surrogate particle deposition was measured on the bottom wall surface of the PCF. The particle deposition over time was observed to decrease as the Reynolds number increased. In addition, the particle spatial distributions increased approaching the side wall of the PCF. This state-of-the art optical technique allows for the non-intrusive measurements of micron-sized particles near the wall surface.

scholarly journals Analytical and Numerical Crack Growth Analysis of 1:3 Scaled Railway Axle Specimens

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 184 ◽  
Author(s):  
David Simunek ◽  
Martin Leitner ◽  
Jürgen Maierhofer ◽  
Hans-Peter Gänser ◽  
Reinhard Pippan
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Crack Propagation ◽  
Crack Growth ◽  
Optical Measurement ◽  
Residual Lifetime ◽  
Residual Stress State ◽  
Propagation Analysis ◽  
Load Tests ◽  
Stress States

This paper deals with experimental fatigue crack propagation in rotating bending loaded round bar specimens as well as an analytical and numerical analysis of the residual lifetime. Constant amplitude (CA) load tests are performed with the surface crack length being evaluated using an optical measurement system. Fracture surfaces are microscopically analyzed to determine crack growth in depth as well as the crack shape. In spite of identical testing conditions, the experimental results show some scatter in residual lifetime, which is mainly caused by different residual stress states. Although X-ray residual stress measurements reveal only minor values, a superposition of the residual stress state with the load-induced stress leads to a significant impact on the residual lifetime calculations, which explains the experimental scatter. Numerical analyses are conducted to consider the residual stress state and their effect on crack propagation by different options. Considering the residual stress distribution in depth within the residual lifetime assessment, the deviation to the most conservative experiment is reduced from +48% to +2%. In conclusion, the results in this paper highlight that it is of utmost importance to consider local residual stress conditions in the course of a crack propagation analysis in order to properly assess the residual lifetime.

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