Development of a photomicroscope method for in situ damage monitoring under ultrasonic fatigue test

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kai Tan ◽  
Victor Postel ◽  
Yujia Liu ◽  
Dongtong Yang ◽  
Sen Tang ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Early Stage ◽  
Strain Analysis ◽  
Infrared Camera ◽  
Small Crack ◽  
Image Correlation ◽  
Content Type ◽  
Damage Monitoring ◽  
Ultrasonic Fatigue

PurposeMechanical issues related to the information and growth of small cracks are considered to play a major role in very high cycle fatigue (VHCF) for metallic materials. Further efforts on better understanding in early stage of a crack are beneficial to estimating and preventing catastrophic damage for a long period service.Design/methodology/approachDependent on the ultrasonic loading system, a novel method of in situ photomicroscope is established to study the crack behaviors in VHCF regime.FindingsThis in situ photomicroscope method provides advantages in combination with fatigue damage monitoring at high magnification, a large number of cycles, and efficiency. Visional investigation with attached image proceeding code proves that the method has high resolution on both size and time, which permits reliable accuracy on small crack growth rate. It is observed that the crack propagation trends slower in the overall small crack stage down to the level of 10–11 m/cycle. Strain analysis relays on a real-time recording which is applied by using digital image correlation. Infrared camera recording indicates the method is also suitable for thermodynamic study while growth of damage.Originality/valueBenefiting from this method, it is more convenient and efficient to study the short crack propagation in VHCF regime.

In-situ thermal image correlation with mechanical properties of nylon-12 in SLS

2016 ◽  
Vol 22 (5) ◽  
pp. 794-800 ◽  
Author(s):  
William Walker Wroe ◽  
Jessica Gladstone ◽  
Tim Phillips ◽  
Scott Fish ◽  
Joseph Beaman ◽  
...  
Keyword(s):  
Thermal History ◽  
Selective Laser Sintering ◽  
Infrared Camera ◽  
Image Correlation ◽  
Correct Prediction ◽  
Content Type ◽  
Multiple Strategies ◽  
Nylon 12 ◽  
History Of

Purpose This paper aims to establish a method to verify in real time the quality of a part being built using Selective Laser Sintering (SLS). Design/methodology/approach A SLS build of 30 Nylon 12 tensile bars was done while using an infrared camera to record the thermal history of each bar. The thermal history was then compared to the ultimate tensile strength (UTS) of each bar. In addition, an attempt was made to identify where the fracture of each bar occurred based on its thermal history. Findings Several analysis techniques were used to compare the thermal history of each bar to its UTS. The strongest correlation found was 0.746. In addition, multiple strategies for predicting the break location where used, with the most successful making a correct prediction on 46 per cent of the bars. Originality/value This paper studies the feasibility of in-situ build verification, a technique that if successful would greatly help the further adoption of SLS as a method of manufacturing.

Methodology for in situ stress intensity factor determination on cracked structures by digital image correlation

2010 ◽  
Vol 1 (4) ◽  
pp. 344-357 ◽  
Author(s):  
V. Richter‐Trummer ◽  
P.M.G.P. Moreira ◽  
S.D. Pastrama ◽  
M.A.P. Vaz ◽  
P.M.S.T. de Castro
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Digital Image Correlation ◽  
Intensity Factor ◽  
Digital Image ◽  
Strain Field ◽  
Image Correlation ◽  
Content Type ◽  
Cracked Structures

PurposeThe purpose of this paper is to develop a methodology for in situ stress intensity factor (SIF) determination that can be used for the analysis of cracked structures. The technique is based on digital image correlation (DIC) combined with an overdetermined algorithm.Design/methodology/approachThe linear overdeterministic algorithm for calculating the SIF based on stress values around the crack tip is applied to a strain field obtained by DIC.FindingsAs long as the image quality is sufficiently high, a good accuracy can be obtained for the measured SIF. The crack tip can be automatically detected based on the same strain field. The use of the strain field instead of the displacement field, eliminates problems related to the rigid body motion of the analysed structure.Practical implicationsIn future works, based on the applied techniques, the SIF of complex cracked plane stress structures can be accurately determined in real engineering applications.Originality/valueThe paper demonstrates application of known techniques, refined for other applications, also the use of stress field for SIF overdeterministic calculations.

Geochemical evaluation of the in-situ regolith of Madengi hills of Dodoma, Tanzania. Implication on bedrock mapping and delineating gold mineralization target

2021 ◽  
pp. geochem2021-074
Author(s):  
Godson Godfray
Keyword(s):  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Soil Geochemistry ◽  
Residual Soils ◽  
Content Type ◽  
Geochemical Evaluation ◽  
Supplementary Material ◽  
Pathfinder Elements

Successful gold exploration projects depend on a piece of clear information on the association between gold, trace elements, and mineralization controlling factors. The use of soil geochemistry has been an important tool in pinpointing exploration targets during the early stage of exploration. This study aimed to establish the gold distribution, the elemental association between gold and its pathfinder elements such as Cu, Zn, Ag, Ni, Co, Mn, Fe, Cd, V, Cr, Ti, Sc, In, and Se and identify lithologies contributing to the overlying residual soils. From cluster analysis, a high similarity level of 53.93% has been shown with Ag, Cd, and Se at a distance level of 0.92. Au and Se have a similarity level of 65.87% and a distance level of 0.68, hence is proposed to be the most promising pathfinder element. PCA, FA, and the Pearson's correlation matrix of transformed data of V, Cu, Ni, Fe, Mn, Cr, and Co and a stronger correlation between Pb and U, Th, Na, K, Sn, Y, Ta and Be shows that source gold mineralization might be associated with both hornblende gneisses interlayered with quartzite, tonalite, and tonalitic orthogneiss. From the contour map and gridded map of Au and its pathfinder elements, it has been noted that their anomalies and target generated are localized in the Northern part of the area. The targets trend ESE to WNW nearly parallel to the shear zones as a controlling factor of Au mineralization emplacement.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5721965

Experimental Study of Fatigue Crack Initiation and Strain Evolution around a Micro-Void by In Situ SEM and Digital Image Correlation

2017 ◽  
Vol 754 ◽  
pp. 75-78 ◽  
Author(s):  
De Qiang Wang ◽  
Ming Liang Zhu ◽  
Fu Zhen Xuan
Keyword(s):  
Fatigue Crack ◽  
Digital Image Correlation ◽  
Crack Initiation ◽  
Digital Image ◽  
Early Stage ◽  
Fatigue Crack Initiation ◽  
Image Correlation ◽  
Dominant Factor ◽  
Strain Evolution

Fatigue crack initiation stage occupies a large proportion of total fatigue life in modern engineering materials and structures which are often designed under lower service loading conditions. In this paper, the fatigue crack initiation behavior from a micro-void in a small-scale specimen was studied in-situ in SEM. Surface morphologies were monitored in-situ and images were taken during interrupted tests at selected number of cycles, and displacement and strain map around the void was calculated based on digital image correlation (DIC) technique. The results indicated that the strain evolution near the micro-void could be divided into stages, before crack initiation. The strain increasing rate was fast in the early stage and slower in the second stage. A critical cyclic strain value for fatigue crack initiation from the micro-void was obtained around 9%, and was believed to be the dominant factor for early stage of fatigue damage.

The Nanomechanics of Tetrahedral Amorphous Diamond-Like Carbon (ta-C) MEMS

2003 ◽  
Author(s):  
I. Chasiotis ◽  
S. W. Cho ◽  
T. A. Friedmann ◽  
J. P. Sullivan
Keyword(s):  
Strain Analysis ◽  
Film Surface ◽  
Image Correlation ◽  
Diamond Like Carbon ◽  
Tensile Stresses ◽  
Notched Specimens ◽  
Failure Properties ◽  
First Time ◽  
Very High

The mechanics of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS structures have been investigated in connection with their elastic and failure properties. For this purpose, micro-tension specimens of thicknesses between 1.2 μm and 1.8 μm and gage widths of 10 μm or 50 μm have been fabricated by the Sandia National Laboratories (SNL). The mechanical characterization has been conducted via in situ AFM measurements and Digital Image Correlation (DIC) data strain analysis and the deformation fields of uniform tension specimens and internally notched specimens with acute notches (K=27) have been experimentally obtained. The elastic modulus and Poisson’s ratio were measured for the first time directly from the specimens averaging 750 GPa and ν=0.16 respectively, while the tensile strength was found to be very consistent averaging 7.0 GPa. Stressed material domains with smaller dimensions in the vicinity of micronotches exhibited even higher failure strength reaching an average of 11.5 GPa with about 10% scatter. AFM images of specimens under high tensile stresses have also indicated the possibility of an sp3 to sp2 phase transformation on the film surface at very high tensile stresses (>6 GPa).

scholarly journals In Situ Measurements for Plastic Zone Ahead of Crack Tip and Continuous Strain Variation under Cyclic Loading Using Digital Image Correlation Method

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 273 ◽  
Author(s):  
Yan Zhao ◽  
Dianyin Hu ◽  
Meng Zhang ◽  
Wei Dai ◽  
Weifang Zhang
Keyword(s):  
Digital Image Correlation ◽  
Plastic Zone ◽  
Crack Propagation ◽  
Digital Image ◽  
Crack Tip ◽  
Experimental Results ◽  
Image Correlation ◽  
Specimen Preparation ◽  
Strain Variation

Fatigue crack is one of the most common damage forms for aeronautical aluminum alloy. With crack propagation, the strain fields of the whole object surface and plastic zone (PZ) ahead of the crack tip are changing continuously. For most metallic materials, the behavior of PZ around the crack tip and continuous strain variation play a vital role in crack propagation. In this work, the “continuous” strain information at and in front of the crack tip on the specimen surface was obtained quantitatively and the PZ size ahead of crack tip was in situ measured quantitatively with crack propagation by using the digital image correlation (DIC) method, which overcomes the difficulty for the in situ measurement of mechanical variables. Moreover, the method of specimen preparation was simplified by using a white matt paint with strong adhesion, but also resulted in a higher resolution being shown, even for such a large area. Furthermore, the experimental results of the PZ size from the proposed method had good agreement with the theoretical values, which overcomes the limitation that the conventional approaches only consider the quasi-static crack. Finally, the continuous strain variation behavior was analyzed from the experimental results in detail with the consideration of crack propagation.

scholarly journals Strain Analysis on Electrochemical Failures of Nanoscale Silicon Electrode Based on Three-Dimensional In Situ Measurement

2020 ◽  
Vol 10 (2) ◽  
pp. 468 ◽  
Author(s):  
Zhifeng Qi ◽  
Zhongqiang Shan ◽  
Weihao Ma ◽  
Linan Li ◽  
Shibin Wang ◽  
...  
Keyword(s):  
Silicon Film ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Image Correlation ◽  
Mechanical Parameters ◽  
Stress Strain ◽  
Full Field ◽  
Battery Capacity

Nanoscale silicon film electrodes in Li-ion battery undergo great deformations leading to electrochemical and mechanical failures during repeated charging-discharging cycles. In-situ experimental characterization of the stress/strain in those electrodes still faces big challenges due to remarkable complexity of stress/strain evolution while it is still hard to predict the association between the electrode cycle life and the measurable mechanical parameters. To quantificationally investigate the evolution of the mechanical parameters, we develop a new full field 3D measurement method combining digital image correlation with laser confocal profilometry and propose a strain criterion of the failure based on semi-quantitative analysis via mean strain gradient (MSG). The experimental protocol and results illustrate that the revolution of MSG correlates positively with battery capacity decay, which may inspire future studies in the field of film electrodes.

Detection of fatigue crack propagation through damage characteristic FWHM using FBG sensors

Sensor Review ◽  
2020 ◽  
Vol 40 (6) ◽  
pp. 665-673
Author(s):  
Meng Zhang ◽  
Weifang Zhang ◽  
Xiaobei Liang ◽  
Yan Zhao ◽  
Wei Dai
Keyword(s):  
Crack Propagation ◽  
Strain Field ◽  
Theoretical Calculations ◽  
Damage Index ◽  
Crack Tip ◽  
Image Correlation ◽  
Content Type ◽  
Inhomogeneous Strain ◽  
Fbg Sensors ◽  
Damage Characteristic

Purpose Crack damage detection for aluminum alloy materials using fiber Bragg Grating (FBG) sensor is a kind of structure health monitoring. In this paper, the damage index of full width at half maximum (FWHM) was extracted from the distorted reflection spectra caused by the crack-tip inhomogeneous strain field, so as to explain the crack propagation behaviors. Design/methodology/approach The FWHM variations were also investigated through combining the theoretical calculations with simulation and experimental analyses. The transfer matrix algorithm was developed to explore the mechanism by which FWHM changed with the linear and quadratic strain. Moreover, the crack-tip inhomogeneous strain field on the specimen surface was computed according to the digital image correlation measurement during the experiments. Findings The experimental results demonstrated that the saltation points in FWHM curve accorded with the moments of crack propagation to FBG sensors. Originality/value The interpretation of reflected spectrum deformation mechanism with crack propagation was analyzed based on both simulations and experiments, and then the performance of potential damage features – FWHM were proposed and evaluated. According to the correlation between the damage characteristic and the crack-tip location, the crack-tip of the specimen could be measured rapidly and accurately with this technique.

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