Effect of Specimen Thickness on Fracture Toughness of Bovine Patellar Cartilage

2003 ◽  
Vol 125 (6) ◽  
pp. 927-929 ◽  
Author(s):  
D. J. Adams ◽  
K. M. Brosche ◽  
J. L. Lewis
Keyword(s):  
Mechanical Property ◽  
Fracture Toughness ◽  
Articular Cartilage ◽  
Fracture Behavior ◽  
Crack Tip ◽  
Opening Angle ◽  
Specimen Thickness ◽  
Patellar Cartilage ◽  
Crack Tip Opening Angle ◽  
Crack Tip Opening

Fracture toughness and crack tip opening angle were measured for bovine patellar cartilage using modified single-edged notch specimens of two thicknesses. There was no difference in fracture toughness between thin (0.7 mm) versus relatively thick (2.7 mm) specimens, but the crack tip opening angle at initiation of crack propagation was larger for the thin specimens (106 deg) than for the thick specimens (70 deg). Fracture toughness of the bovine patellar cartilage 1.03kJ/m2 was not statistically different than that reported previously for canine patellar cartilage 1.07kJ/m2 employing the same methods. Large variation in measurements for both bovine and canine cartilage are in part attributable to variation between individual animals, and are consistent with variation in other mechanical property measurements for articular cartilage. The observed reduction in crack tip opening angle with increased specimen thickness is consistent with behavior of some engineering materials, and demonstrates that specimen thickness influences fracture behavior for bovine patellar cartilage.

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.

Application of a Simplified Constant Crack Tip Opening Angle Model to Crack Propagation Analyses in Steel Pipelines

2020 ◽  
Author(s):  
Chris Bassindale ◽  
Xin Wang ◽  
William R. Tyson ◽  
Su Xu
Keyword(s):  
Crack Tip ◽  
Propagation Model ◽  
Simplified Model ◽  
Computational Time ◽  
Opening Angle ◽  
Recent Experimental Data ◽  
Published Data ◽  
Velocity Data ◽  
Crack Tip Opening Angle ◽  
Crack Tip Opening

Abstract In this paper, a simplified constant crack tip opening angle (CTOA) model is presented and used to analyze two different pipeline steels. The steels examined in this work were an American Petroleum Institute (API) Standard X65 steel and a Japanese Industrial Standard (JIS) steel with the grade designation of STPG370. The commercial finite element (FE) code ABAQUS 2017x was used to generate the models and solve the analyses. The proposed propagation model was first verified through comparing the numerical results with published data. The steady-state fracture velocity data from the simplified model matched the data from literature within a maximum difference of 2% while drastically reducing the computational time required by an order of magnitude. Following the verification of the simplified model, it was then used to analyze recent experimental data. The model was able to match the experimental crack velocity data within a difference of 4%.

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