Experimental method for determining the fracture toughness of concrete based on the modified two‐parameter model and DIC technique

2021 ◽  
Author(s):  
Longbang Qing ◽  
Guorui Cao ◽  
Junfeng Guan ◽  
Shuguang Li
Keyword(s):  
Fracture Toughness ◽  
Experimental Method ◽  
Two Parameter ◽  
Dic Technique

The Experiment for the Fracture Toughness of the Compound Bioceramic and the Analysis for the Confidence Level of its Reliability

2010 ◽  
Vol 44-47 ◽  
pp. 3003-3010
Author(s):  
Shi Lian Xu ◽  
Rui Hong Wang ◽  
Ruo Qi Li ◽  
Ren Ping Xu
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Confidence Level ◽  
Confidence Limit ◽  
Limit Curve ◽  
Medical Treatments ◽  
Manufacturing Method ◽  
Upper Confidence Limit ◽  
Lower Confidence ◽  
Two Parameter

The brittle is crippling the application of bioceramic. The compound bioceramic is a new biomaterial being widely applied in medical treatments and its fracture toughness is an important mechanical behaviors. In this paper, we introduce the manufacturing method of the compound bioceramic and experiment facilities for its fracture toughness, investigate its probability distribution for the experimental data and conduct the test for fit. We conclude that the experimental data for the toughness fracture of the compound bioceramic obey the two-parameter Weibull distribution, introduce the analyzing method for the upper confidence limit curve and lower confidence limit curve and study the reliability and confidence level of the fracture toughness of the compound bioceramic.

Discussion of a New Experimental Method in Measuring Fracture Toughness Initiation at High Loading Rates by Stress Waves

1982 ◽  
Vol 104 (1) ◽  
pp. 29-35 ◽  
Author(s):  
J. R. Klepaczko
Keyword(s):  
Fracture Toughness ◽  
Experimental Method ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Fracture Initiation ◽  
High Loading ◽  
Screening Tests ◽  
Hopkinson Pressure Bar ◽  
Loading Rates ◽  
Wide Range

An experimental method is described for measuring the fracture initiation properties of metals and alloys over a wide range of loading rates, which can cover over six orders of magnitude in K˙I (1 MPam s−1 ≤ K˙I ≤ 106 MPam s−1). With some modification of the standard compact tension specimen, a large series of screening tests can be performed in the high loading region at a relatively low cost. At the lower loading rates a standard closed loop testing machine can be used. To evaluate fracture initiation at a very high loading rate, a special arrangement of the split Hopkinson pressure bar has been proposed. Specimens of the same geometry as those used in quasi-static tests are placed between the Hopkinson bars. Since the wedge is attached to the incident bar, and the specimen is backed by the transmitter bar (Fig. 2), the course of specimen loading and fracturing can be exactly monitored by recording the incident, reflected and transmitted longitudinal waves. Using this technique, fracture initiation of the prefatigued specimen has been achieved within ∼ 20 μs after the beginning of specimen loading. The effects of inertia acting on the specimen and an error introduced by friction are both considered. Experiments performed on some aluminum alloys as well as on medium carbon steel revealed a complicated pattern of the fracture toughness behavior. Generally, for the strain rate sensitive materials a substantial decrease in fracture toughness was observed under high loading rates.

Gouge Assessment for Pipes and Associated Transferability Problem

2009 ◽  
Vol 294 ◽  
pp. 15-25 ◽  
Author(s):  
Mohammed Hadj Meliani ◽  
G. Pluvinage ◽  
J. Capelle
Keyword(s):  
Fracture Toughness ◽  
Aspect Ratio ◽  
Internal Pressure ◽  
High Aspect Ratio ◽  
Fracture Resistance ◽  
Pipe Steel ◽  
Failure Assessment Diagram ◽  
Failure Assessment ◽  
Resistance Criterion ◽  
Two Parameter

The purpose of this work is to assess a gouge defect in a pipe submitted to internal pressure. To do that a method is used which is based upon a failure assessment diagram and, more precisely, upon a Modified Notch Failure Assessment Diagram (NMFAD) which has been proposed as a mesofracture approach. The safety factor has been determined under conservative conditions; i.e for a X52 pipe steel having a relatively low fracture toughness and a severe gouge defect with high aspect ratio and high constraint. In addition, a mesofracture approach to the fracture toughness transferability problem has been proposed. The crack (K-T) methodology has been modifed to create the ( –Teff) two-parameter fracture resistance criterion.

An Engineering Method for Assessing the Effects of Neutron Irradiation on the Fracture Toughness of RPV Steels

2011 ◽  
Author(s):  
Zhong-An Chen ◽  
L. Y. Wang ◽  
Yuh-Jin Chao ◽  
Poh-Sang Lam ◽  
X. S. Jin
Keyword(s):  
Fracture Toughness ◽  
Neutron Irradiation ◽  
Fracture Criterion ◽  
Crack Tip ◽  
Stress Fields ◽  
Fracture Toughness Test ◽  
Property Changes ◽  
Two Parameter ◽  
Reactor Pressure ◽  
Crack Tip Stress

Neutron irradiation degrades the reactor pressure vessel (RPV) steels. As the steel degrades, the mechanical properties of the material also change which affect the crack tip stress fields. In this article, we show that reduction of the “fracture toughness” of the RPV steels due to neutron irradiation can be interpreted by a change of an “equivalent constraint” due to material property changes. Using the J-A2 two-parameter fracture methodology to quantify the crack tip stress fields and a critical stress fracture criterion, the methodology is applied to the interpretation of fracture toughness test data from un-irradiated and irradiated RPV steels.

Crack-Tip Fields of Short Cracks in Bending As Characterized by Two Parameter Criterion

1993 ◽  
Author(s):  
J. F. Zarzour ◽  
Y. Dah-Wei ◽  
M. J. Kleinosky
Keyword(s):  
Fracture Toughness ◽  
Large Scale ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Significant Loss ◽  
Integral Approach ◽  
Rigorous Framework ◽  
Crack Tip Constraint ◽  
Two Parameter ◽  
Crack Tip Stress

Abstract Single edge notched bars (SENB), in the bending mode, with a/W ratios ranging from 0.05 to 0.5 were examined for fracture toughness in terms of the J-integral approach. The results indicate that for a/W ratios less than 0.3, there is a significant loss of J-dominance. This loss is attributed to the effect of plastic deformation on the cracked face. For a/W ratios greater than 0.3, J-dominance is maintained into the large scale yielding regime. According to the recently developed two-parameter criterion (J,Q), compressive Q-stress was interpreted as an indication of low crack-tip stress triaxiality for shallow cracks, while positive Q-stress was associated with high crack-tip stress triaxiality for deep cracks. For the material properties and specimen geometries considered herein, a fracture toughness locus was constructed in terms of the (J,Q) parameters for each of the a/W ratios. The overall fracture data are in agreement with those predicted by other approaches and provide a rigorous framework for interpreting the effect of loss of crack-tip constraint in elastic-plastic fracture analyses.

The Effects of Constraint and Compressive or Tensile Residual Stresses on Brittle Fracture

2009 ◽  
Author(s):  
Simon Kamel ◽  
Robert C. Wimpory ◽  
Michael Hofmann
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Brittle Fracture ◽  
Driving Force ◽  
High Strength ◽  
Element Analysis ◽  
Crack Driving Force ◽  
Temperature Fracture ◽  
Crack Tip Constraint ◽  
Two Parameter

Residual stress is a key feature in components containing defects which can affect the crack driving force and alter the crack tip constraint to give a modified fracture toughness. In this paper experimental and numerical investigations are performed on ‘C’ shape fracture mechanics specimens, extracted from a high strength low alloy tubing steel, to examine the effects of constraint and tensile or compressive residual stress on brittle fracture. The residual stress is introduced into the specimens by a tensile or compressive mechanical pre-load to produce, respectively, a compressive or tensile residual stress in the region where the crack is introduced. Neutron diffraction measurements are performed on the pre-loaded specimens prior to introduction of a crack, and compared with predictions of the residual stress from finite-element analysis, using tensile properties derived at room temperature. Fracture toughness tests are carried out on the as-received (non-preloaded) and pre-loaded specimens and the effect of residual stress on crack driving force and constraint is evaluated using the two-parameter J-Q approach.

Quantification of Crack-Tip Constraint Effect on Master Curve Reference Temperature Based on Two-Parameter Approach

2006 ◽  
Vol 110 ◽  
pp. 89-96 ◽  
Author(s):  
Nam Su Huh ◽  
Ludwig Stumpfrock ◽  
Xaver Schuler ◽  
Eberhard Roos
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Crack Tip ◽  
Reference Temperature ◽  
Fracture Toughness Test ◽  
Testing Specimen ◽  
Correlation Models ◽  
Dimensional Finite Element ◽  
Crack Tip Constraint ◽  
Two Parameter

The master curve has evolved into a mature technology for characterizing the fracture toughness transition of ferritic steels. However, it is well known that the master curve reference temperature (To) values estimated from small laboratory specimen may be biased low due to loss of crack-tip constraint. To quantify such variations of To resulting from differences of crack-tip constraint of testing specimen, two-parameter fracture mechanics approaches are employed in the present study. In this context, fracture toughness test and 3-dimensional finite element (FE) analysis for several standard and nonstandard test specimens are performed to quantify relationship between variations of To and constraint parameters and to find best constraint parameter representing effect of crack-tip constraint on To values evidently. Based on testing and present FE results, To and constraint parameter loci are constructed and engineering To correlation models considering crack-tip constraint are suggested

Sign in / Sign up

Export Citation Format

Share Document