Influence of Martensitic Phase on Microcrack Propagation in a Ferritic-Martensitic Steel

2014 ◽  
Vol 891-892 ◽  
pp. 301-306 ◽  
Author(s):  
Angelika Brueckner-Foit ◽  
Pascal Pitz ◽  
Frank Zeismann ◽  
Lisa Zellmer
Keyword(s):  
Dual Phase Steel ◽  
Martensitic Steel ◽  
Crack Opening ◽  
Crack Tip ◽  
Relative Displacement ◽  
Image Correlation ◽  
X Ray ◽  
Crack Wake ◽  
Microcrack Propagation

Hard phases such as martensite regions affect micro-crack extension by blocking the plastic zone ahead of the crack tip, but also by changing the crack opening which can be taken as loading quantity for cracks. This paper deals with the measurement of crack opening for microcracks in a ferrite/martensite dual phase steel. The methods used are in-situ testing in the SEM, X-ray tomography, and digital image correlation. It was found that martensite regions affect the relative displacement of the crack phases both at the crack tip and in the crack wake.

3D/4D Strain Mapping Using In Situ X-Ray Microtomography

2011 ◽  
Vol 70 ◽  
pp. 249-254 ◽  
Author(s):  
Hiroyuki Toda ◽  
Kentaro Uesugi ◽  
Yoshio Suzuki ◽  
Masakazu Kobayashi
Keyword(s):  
Strain Distribution ◽  
Crack Tip ◽  
Local Strain ◽  
Image Correlation ◽  
Correlation Technique ◽  
In Situ Observation ◽  
Strain Mapping ◽  
X Ray ◽  
Discrete Crack

X-ray microtomography (XMT) has been utilized for the in-situ observation of various structural materials under external disturbance such as loading. In-situ XMT provides a unique possibility to access the three-dimensional (3D) character of internal microstructure and its time evolution behaviours non-destructively, thereby enabling advanced techniques for measuring local strain distribution. Local strain mapping is readily enabled by processing such high-resolution tomographic images either by the particle tracking technique or the digital image correlation technique. Procedures for tracking microstructural features which have been developed by the authors, have been applied to analyse localised deformation and damage evolution in a material. Typically several tens of thousands of microstructural features, such as particles and pores, are tracked in a tomographic specimen (0.2 - 0.3 mm3in volume). When a sufficient number of microstructural features is dispersed in 3D space, the Delaunay tessellation algorithm is used to obtain local strain distribution. With these techniques, 3D strain fields can be measured with reasonable accuracy. Even local crack driving forces, such as local variations in the stress intensity factor, crack tip opening displacement and J integral along a crack front line, can be measured from discrete crack tip displacement fields.

Assessment of Damage and Fracture Behaviours in a Cast Aluminium Alloy via In Situ Synchrotron Microtomography

2006 ◽  
Vol 519-521 ◽  
pp. 1005-1010 ◽  
Author(s):  
Shin Yamamoto ◽  
Hiroyuki Toda ◽  
L. Qian ◽  
Tomomi Ohgaki ◽  
Masakazu Kobayashi ◽  
...  
Keyword(s):  
Driving Forces ◽  
Crack Opening ◽  
Crack Tip ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Contrast Imaging ◽  
Cracking Behavior ◽  
Damage And Fracture ◽  
Void Initiation

High resolution phase contrast imaging technique has been applied to obtain clear crack images together with the detailed of microstructural features in a cast aluminum alloy. Crack opening/closure, crack extension and damage evolution in the vicinity of a crack-tip is observed three-dimensionally (3-D). 3-D image analysis is performed to evaluate void initiation and growth near the crack-tip. The information on physical displacement of each microstructural feature is provided for analyzing local crack driving forces at crack front. This technique has been identified to provide a unique possibility to quantitatively interpret the 3-D cracking behavior in bulk materials.

scholarly journals In situ through-thickness analysis of crack tip fields with synchrotron X-ray diffraction

2019 ◽  
Vol 127 ◽  
pp. 500-508 ◽  
Author(s):  
P. Lopez-Crespo ◽  
J.V. Peralta ◽  
J.F. Kelleher ◽  
P.J. Withers
Keyword(s):  
Crack Tip ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crack Tip Fields

Microstructure-Scale In-Situ Image Correlation-Based Study of Grain Deformation and Crack Tip Displacements in Al–Cu Alloys

2014 ◽  
Vol 4 (2) ◽  
pp. MPC20140041
Author(s):  
Vipul K. Gupta ◽  
Scott A. Willard ◽  
Jacob D. Hochhalter ◽  
Stephen W. Smith
Keyword(s):  
Crack Tip ◽  
Image Correlation ◽  
Cu Alloys

Controlled Initiation of Short Fatigue Cracks in 316L Steel

2005 ◽  
Author(s):  
D. Stefanescu ◽  
J. Marrow ◽  
M. Preuss ◽  
A. Sherry
Keyword(s):  
Experimental Study ◽  
Stainless Steel ◽  
Crack Opening Displacement ◽  
Crack Nucleation ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Crack Tip ◽  
Image Correlation ◽  
Opening Displacement ◽  
R Ratio

Validation of models for short crack behavior requires accurate measurement of crack opening displacement and crack tip strain fields. Development of reliable measurement procedures, using new techniques such as Image Correlation (IC), requires specimens containing cracks with a well defined geometry. In this paper, results of an experimental study concerning controlled initiation of short fatigue cracks at positive R-ratio in laboratory specimens made from 316L stainless steel are presented. Experimental techniques, including hardness testing and X-ray diffraction were employed in order to investigate the effect of surface preparation on the surface mechanical properties and residual stresses. Crack nucleation is difficult in smooth specimens of 316L austenitic stainless steel at positive R-ratio due to the high fatigue limit and low tensile strength. Specimens with a thin ligament were therefore developed to enable nucleation of a single short fatigue crack. An experimental study of the crack growth aspect ratio evolution was then carried out using a beach marking technique. The technique described in this paper enables single short fatigue cracks of well defined geometry to be nucleated under tensile cyclic loading. Stress corrosion cracks can be developed using the same specimen geometry. Miniature tensile specimens can then be extracted to perform in-situ measurements of the crack opening displacement and crack tip strain field by Image Correlation from Scanning Electron Microscopy observations.

A Two-Parameter Description of the Behaviour of a Process Zone at a Crack Tip: Relation Between the Parameters

2005 ◽  
Author(s):  
E. Smith
Keyword(s):  
Process Zone ◽  
Crack Opening ◽  
Crack Tip ◽  
Relative Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Power Series Expansions ◽  
Elastic Crack ◽  
Crack Tip Opening ◽  
Crack Faces

The relative displacement of the crack faces and the tensile stress ahead of a Mode I elastic crack tip can be expressed, in the immediate vicinity of the tip, by two-term power series expansions, the two terms being associated with the stress intensity factor KI and a dimensionless parameter g0. These parameters feature prominently in cohesive process zone models of a crack tip with regard to the crack tip opening displacement vT, process zone size s, the crack opening area A and the effective opening area AD of the process zone. This paper shows that KI and g0 depend upon each other via a relation which is dependent upon the geometrical configuration but is independent of the configuration’s loading pattern.

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.

Sign in / Sign up

Export Citation Format

Share Document