ICF4 discussion: ?Elastic/Plastic separation energy rate for crack advance in finite growth steps,?

1977 ◽  
Vol 13 (5) ◽  
pp. 714-716 ◽  
Author(s):  
H. F�hring ◽  
T. Seeger
Keyword(s):  
Crack Advance ◽  
Separation Energy ◽  
Energy Rate ◽  
Elastic Plastic ◽  
Finite Growth

Flaw Stability in Mild Steel Tanks in the Upper-Shelf Ductile Range—Part I: Mechanical Properties

1999 ◽  
Vol 122 (2) ◽  
pp. 162-168 ◽  
Author(s):  
Robert L. Sindelar ◽  
Poh-Sang Lam ◽  
George R. Caskey, ◽  
Leta Y. Woo
Keyword(s):  
Mechanical Properties ◽  
Compact Tension ◽  
Carbon Steels ◽  
Crack Advance ◽  
Storage Tanks ◽  
Elastic Plastic ◽  
Steel Tanks ◽  
Jr Curves ◽  
Shelf Region ◽  
Range Part

Mechanical properties of 1950’s vintage, A285 Grade B carbon steels have been compiled for elastic-plastic fracture mechanics analysis of storage tanks (Lam and Sindelar, 2000). The properties are from standard Charpy V-notch (CVN), 0.4T planform compact tension (C(T)), and tensile (T) specimens machined from archival steel from large water piping. The piping and storage tanks were constructed in the 1950s from semi-killed, hot-rolled carbon steel plate specified as A285 Grade B. Evaluation of potential aging mechanisms at both service conditions shows no loss in fracture resistance of the steel in either case. Site and literature data show that the A285, Grade B steel, at and above approximately 70°F (21°C), is in the upper transition to upper shelf region for absorbed energy and is not subject to cleavage cracking or a brittle fracture mode. Furthermore, the tank sidewalls are 1/2 or 5/8-in. (12.7 or 15.875 mm) thick, and therefore, the J-resistance JR curve that characterizes material resistance to stable crack extension under elastic-plastic deformation best defines the material fracture toughness. The JR, curves for several heats of A285, Grade B steel tested at 40°F (4.4°C), a temperature near the average ductile-to-brittle (DBTT) transition temperature (CVN at 15 ft-lb or 20.3 J), are presented. This data is applicable to evaluate flaw stability of the storage tanks that are operated above 70°F (21°C) since, even at 40°F (4.4°C), crack advance is observed to proceed by ductile tearing. [S0094-9930(00)00402-9]

Crack Separation Energy Rates in Elastic-Plastic Fracture Mechanics

1976 ◽  
Vol 190 (1) ◽  
pp. 571-584 ◽  
Author(s):  
A. P. Kfouri ◽  
K. J. Miller
Keyword(s):  
Fracture Mechanics ◽  
Biaxial Stress ◽  
Separation Energy ◽  
Brittle Crack ◽  
Finite Element Program ◽  
Elastic Plastic ◽  
Theoretical Predictions ◽  
Element Program ◽  
Dimensional Parameters ◽  
Independent Integral

SYNOPSIS The application of Griffith energy concepts to Elastic-Plastic Fracture Mechanics (EPFM) is investigated. An elastic-plastic finite element program is used to calculate the values of the Crack Separation Energy Rate, GΔ, corresponding to a variety of biaxial stress-strain states. The effect of the size of the crack tip plastic zone on the fracture stress is investigated and a relation is established between two non-dimensional parameters φ and ψ . The first parameter φ gives a measure of the ductility of the material while the second parameter ψ is related to the applied stress when brittle fracture occurs. The character of the φ, ψ dependence suggests that when a certain value of the ductility parameter φ is exceeded, brittle crack growth is no longer possible and the mode of crack extension must change to one of a ductile nature. The theoretical predictions of fracture toughness are favourably compared with the results of experiments. Calculated values of GΔ, the stress intensity factor, K, and Rice's path independent integral J are also compared and the applicability of these parameters to brittle, quasi-brittle and ductile fracture is critically discussed.

Inverse Analysis to Estimate Critical Crack Propagation Parameters for Elastic-Plastic and Graded Materials

2004 ◽  
Vol 261-263 ◽  
pp. 117-122
Author(s):  
Toshio Nakamura ◽  
Zi Qiang Wang
Keyword(s):  
Crack Propagation ◽  
Inverse Analysis ◽  
Crack Opening ◽  
Reaction Force ◽  
Accurate Estimation ◽  
Crack Advance ◽  
Inhomogeneous Materials ◽  
Graded Materials ◽  
Elastic Plastic ◽  
Fracture Parameters

Accurate crack propagation simulation requires critical fracture parameters to be known a priori. For elastic-plastic materials, two fundamental parameters are the separation energy and the peak stress required to generate new crack surfaces. In general, both are difficult to quantify since direct determinations are not possible in experiments. For inhomogeneous materials, such as graded materials, determination is even more complex since these parameters vary spatially. In this paper, a novel method based on an inverse analysis technique is proposed to estimate the fracture parameters of elastic-plastic and graded media. The method utilizes the Kalman filter to process measured data and extract best estimates of the unknown parameters. The accuracy of the method is examined in a verification study where a dynamically propagating crack in double cantilever beam type specimen is modeled. In the study, time variation records of crack opening displacement, opening strain, crack advance distance, and load point reaction force are used as possible measurements. Despite large noises in data, the results confirm accurate estimation. The estimates improve when multiple measurements are supplied to the inverse technique.

Elasto-plastic state of curve beam system subjected to complex loading

1996 ◽  
Vol 18 (4) ◽  
pp. 14-22
Author(s):  
Vu Khac Bay
Keyword(s):  
Cylindrical Shell ◽  
Solution Method ◽  
Complex Loading ◽  
Numerical Results ◽  
Elastic Solution ◽  
Plastic State ◽  
Curve Beam ◽  
Elastic State ◽  
Elastic Plastic ◽  
Beam System

Investigation of the elastic state of curve beam system had been considered in [3]. In this paper the elastic-plastic state of curve beam system in the form of cylindrical shell is analyzed by the elastic solution method. Numerical results of the problem and conclusion are given.

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