scholarly journals Microstructural morphology effects on fracture resistance and crack tip strain distribution in Ti–6Al–4V alloy for orthopedic implants

2014 ◽  
Vol 53 ◽  
pp. 870-880 ◽  
Author(s):  
I. Cvijović-Alagić ◽  
N. Gubeljak ◽  
M. Rakin ◽  
Z. Cvijović ◽  
K. Gerić
Keyword(s):  
Strain Distribution ◽  
Fracture Resistance ◽  
Crack Tip ◽  
Orthopedic Implants ◽  
Microstructural Morphology

Plastic Strain Distribution at the Tips of Propagating Fatigue Cracks

1976 ◽  
Vol 98 (1) ◽  
pp. 24-29 ◽  
Author(s):  
D. L. Davidson ◽  
J. Lankford
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Plastic Strain ◽  
Plastic Zone ◽  
Strain Distribution ◽  
Dimensionless Parameter ◽  
Fatigue Cracks ◽  
Crack Tip ◽  
Cyclic Plastic Zone ◽  
Plastic Zones

The techniques of selected area electron channeling and positive replica examination have been used to study the plastic zones attending fatigue crack propagation in 304 SS, 6061-T6 aluminum alloy, and Fe-3Si steel. These observations allowed the strain distribution at the crack tip to be determined. The results indicate that the concepts of a monotonic and a cyclic plastic zone are essentially correct, with the strains at demarcation between these two zones being 3 to 6 percent. Strain distribution varies as r−1/2 in the cyclic zone and as ln r in the monotonic plastic zone. The strain distributions for all materials studied may be made approximately coincident by using a dimensionless parameter related to distance from the crack tip.

Hybrid Measurement of CT and Strain Distribution of Internal Crack Using Synchrotron High-Energy Monochromatic X-Rays

2010 ◽  
Vol 652 ◽  
pp. 202-209
Author(s):  
Keisuke Tanaka ◽  
Takahisa Shobu ◽  
Hiroshi Kimachi
Keyword(s):  
Strain Distribution ◽  
Crack Opening ◽  
Three Dimensional ◽  
Crack Tip ◽  
High Energy ◽  
Internal Crack ◽  
X Rays ◽  
Crack Face ◽  
Dimensional Shape ◽  
Three Dimensional Shape

Using high-energy monochromatic X-rays of energy 66.4keV from the synchrotron radiation source, SPring-8, we have developed a system to perform a hybrid measurement of imaging of cracks and strain distribution around cracks. This system was applied to a fatigue crack made in a round bar made of carbon steel with a diameter of 4 mm. Computed tomography of the specimen gave the three-dimensional shape of a thumb-nail crack. High tensile strain ahead of the crack was measured at the applied maximum stress, while the strain on the crack face was low because of stress relief due to crack opening. The full width at half maximum (FWHM) increased near the crack tip under loading, and then decreased after unloading. The recoverable part of FWHM by unloading was caused by the steep distribution of the applied stress in the vicinity of the crack tip. The FWHM increased by plastic deformation does not change when unloaded. The measured distributions of the lattice strain and FWHM agreed well with those of the elastic and plastic strains calculated by the finite element method, respectively.

Crack Tip Opening Angle: Measurement and Modeling of Fracture Resistance in Low and High Strength Pipeline Steels

2006 ◽  
Author(s):  
Ph. P. Darcis ◽  
G. Kohn ◽  
A. Bussiba ◽  
J. D. McColskey ◽  
C. N. McCowan ◽  
...  
Keyword(s):  
Steady State ◽  
Fracture Resistance ◽  
Fracture Process ◽  
Pipeline Steel ◽  
Crack Tip ◽  
High Strength ◽  
Opening Angle ◽  
Test Technique ◽  
Crack Tip Opening Angle ◽  
Crack Tip Opening

Crack tip opening angle (CTOA) is becoming one of the more widely accepted properties for characterizing fully plastic fracture. In fact, it has been recognized as a measure of the resistance of a material to fracture, in cases where there is a large degree of stable-tearing crack extension during the fracture process. This type of steady-state fracture resistance takes place when the CTOA in a material reaches a critical value, as typically occurs in low-constraint configurations. Our current research has applied the CTOA concept as an alternative or an addition to the Charpy V-notch and the drop weight tear test (DWTT) fracture energy in pipeline characterization. A test technique for direct measurement of CTOA was developed, using a modified double cantilever beam (MDCB) specimen. A digital camera and image analysis software are used to record the progression of the crack tip and to estimate CTOA using the crack edges adjacent to the crack tip. A steady-state CTOA has been successfully measured on five different strength grades of gas pipeline steel (four low strength grades and one high strength grade: X100). In addition, two-dimensional finite element models (2D FEMs) are used to demonstrate the sequence of the fracture process and the deformation mechanisms involved. The CTOA measurements and models are correlated and agree well.

Experimental Determination of Fatigue Crack Growth Behavior and Surface Strain Distribution of ‘Faint-Waist Pure Shear’ Specimens with Different Crack Tip Radii

2006 ◽  
Vol 79 (4) ◽  
pp. 712-733 ◽  
Author(s):  
Christian Feichter ◽  
Zoltan Major ◽  
Reinhold W. Lang
Keyword(s):  
Crack Growth ◽  
Strain Gradient ◽  
Strain Distribution ◽  
Strain Analysis ◽  
Crack Tip ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Analysis Method ◽  
Growth Initiation ◽  
Tip Radius

Abstract The influence of the initial crack-tip radius on the fatigue behavior and the strain distribution in the vicinity of the blunted crack tip was determined experimentally using a servo-hydraulic testing machine and an optical full-field strain analysis method. Two different elastomer grades (SBR, EPDM) were selected for the experimental work. The strain analysis method used, based on the image correlation technique, was found to be an effective tool to determine strains, strain distributions and gradients near the crack tip for elastomeric materials. Different material behavior was observed in the two rubber types investigated. While the crack tip was regularly blunted (half circle shape) for EPDM and the strain gradient was low (less steep), the crack tip was sharp (less blunted) with a higher strain gradient for SBR. Furthermore the crack tip radius was found to be an important influencing factor on the initiation of crack growth, but not on the crack growth behavior after initiation. Based on the experimental results a phenomenological, first-order, crack-growth initiation law was proposed, dependent on the crack tip radius, the tearing energy at crack growth initiation for a sharp crack and a parameter representing the influence of the crack tip radius.

Fracture Resistance of Ship Longitudinal Members Including Fatigue Crack

2013 ◽  
Author(s):  
Yann Quéméner ◽  
Chien-Hua Huang ◽  
Chi-Fang Lee
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Fatigue Crack Growth ◽  
Crack Length ◽  
Crack Growth ◽  
Fracture Resistance ◽  
Crack Tip ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Extreme Loads

This study investigates the fracture failure of longitudinal members including cracks. Specifically, this study employs the failure assessment diagram methodology to assess the conditions of failure at the crack tip. Based on various crack configurations, this study establishes the analytical formulations of the crack-tip condition that are validated using finite element analyses. In addition, the material toughness is expressed in terms of crack-tip opening displacement. This study evaluates the failure stress of representative cracked members as a function of the crack length. This enables determining critical crack lengths corresponding to the maximum stresses derived from extreme loads. Finally, this study uses simplified fatigue crack growth analyses to characterize the critical crack length in terms of fatigue life. For members located in the deck and bottom regions, the critical crack lengths correspond to the end of the assessed fatigue life. Therefore, the fracture resistance of the longitudinal members is satisfactory as it will not cause the premature loss of the component. This study also provides analytical formulations for crack-tip conditions that could be employed in a reliability study linking fatigue crack growth and fracture under extreme loads.

scholarly journals Mechanism of Subordinate Peak Skewing of FBG Sensor during Cracks Propagation Monitoring on Aluminum Alloy Structure

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Bo Jin ◽  
Weifang Zhang ◽  
Feifei Ren ◽  
Meng Zhang ◽  
Wei Dai ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Plastic Zone ◽  
Strain Gradient ◽  
Strain Distribution ◽  
Crack Tip ◽  
Fbg Sensor ◽  
Inhomogeneous Strain ◽  
Study Results ◽  
Fbg Sensors ◽  
Cracks Propagation

This study investigates the variety of the spectra features of fiber Bragg grating (FBG) around the crack tip during fatigue crack propagation. The study results reveal that the turning of the subordinate peak is significantly associated with crack lengths and corresponds to strain gradient along the FBG. Meanwhile, the strain distribution sensed by the FBG changes with the sensing section of the grating. FBG sensors could observe the monotonic plastic zone ahead of the fatigue crack tip. The cubic strain is distributed along the grating, with monotonic plastic zone propagation at the initial and terminal part of the grating, at approximately a 30% ratio of the entire grating. However, the monotonic plastic zone is sensed by the FBG, at ±15% bias of the grating center, with the quadratic strain gradient pattern along the grating. In particular, when the initial and terminal parts of the grating experience highly inhomogeneous strain distribution, the spectrum distortion occurs.

Sign in / Sign up

Export Citation Format

Share Document