The effect of specimen thickness on the fracture toughness of Ti-6A1-4V

1972 ◽  
Vol 8 (4) ◽  
Author(s):  
K.H. Galda ◽  
D. Munz
Keyword(s):  
Fracture Toughness ◽  
Specimen Thickness

Revised η-Factors for 3P SE(B) Fracture Specimens Incorporating 3-D Effects

2014 ◽  
Author(s):  
Rodolfo F. de Souza ◽  
Claudio Ruggieri
Keyword(s):  
Fracture Toughness ◽  
Mouth Opening ◽  
Estimation Procedure ◽  
Crack Mouth Opening Displacement ◽  
Evaluation Procedure ◽  
Specimen Thickness ◽  
Crack Mouth ◽  
Opening Displacement ◽  
Wide Range ◽  
Fracture Specimens

Standardized procedures to measure cleavage fracture toughness of ferritic steels in the DBT region most commonly employ three-point bend fracture specimens, conventionally termed SE(B) or SENB specimens. The evaluation protocol of fracture toughness for these crack configurations builds upon laboratory records of load and crack mouth opening displacement (CMOD) to relate plastic work with J (or, equivalently, CTOD). The experimental approach employs a plastic η-factor to relate the macroscale crack driving force to the area under the load versus crack mouth opening displacement for cracked configurations. This work provides revised η-factors derived from CMOD records applicable to estimate the J-integral and CTOD in SE(B) specimens with varying crack size and specimen configuration. Non-linear finite element analyses for plane-strain and 3-D models provide the evolution of load with increased CMOD which is required for the estimation procedure. The analysis matrix considers SE(B) specimens with W = 2B and W = B configurations with and without side grooves covering a wide range of specimen thickness, including precracked Charpy (PCVN) specimens. Overall, the present results provide further validation of the J and CTOD evaluation procedure currently adopted by ASTM 1820 while, at the same time, giving improved estimation equations for J incorporating 3-D effects which enter directly into more accurate testing protocols for experimental measurements of fracture toughness values using 3P SE(B) specimens.

Establishment of Unified Correlation of In-Plane and Out-of-Plane Constraints with Ductile Fracture Toughness of Steel

2016 ◽  
Vol 853 ◽  
pp. 22-27 ◽  
Author(s):  
Bo Rui Yan ◽  
G.Z. Wang ◽  
Fu Zhen Xuan ◽  
Shan Tung Tu
Keyword(s):  
Fracture Toughness ◽  
Ductile Fracture ◽  
Structural Integrity ◽  
Damage Model ◽  
Equivalent Plastic Strain ◽  
Specimen Thickness ◽  
Wide Range ◽  
Out Of Plane ◽  
Correlation Line ◽  
Ductile Fracture Toughness

In this paper, the finite element method (FEM) based on GTN damage model was used to obtain ductile fracture toughness and investigate the establishment method of unified correlation of in-plane and out-of-plane constraints with ductile fracture toughness of steels. The unified constraint parameter Ap at different equivalent plastic strain (εp) isolines has been calculated and analyzed for SEN(B) specimens with a wide range of in-plane and out-of-plane constraints. The results show that the average Ap along the specimen thickness (Apave) can well characterize a wide range of in-plane and out-of-plane constraints. The suitable εpisolines range for establishing the unified correlation between Apave and ductile fracture toughness of the steel has been obtained. For the specimens with lower constraint, the higher εp values should be used. The results also show that the correlation line of JC/Jref-Apave1/2is independent of the selections of the suitable εp isolines and the reference specimen. This may bring convenience for the establishment and application of the JC/Jref-Apave1/2correlation lines. Using ductile fracture toughness data of a small number of specimens with different constraints (such as three specimens with different a/W) together with FEM calculations of the parameter Ap, the correlation line of JC/Jref-Apave1/2can be established. The correlation line may be used in structural integrity assessments incorporating both in-plane and out-of-plane constraints.

Validation of Linear Elastic Fracture Mechanics in Predicting the Fracture Toughness of Polyethylene Pipe Materials

2015 ◽  
Author(s):  
Tarek M. A. A. El-Bagory ◽  
Hossam E. M. Sallam ◽  
Maher Y. A. Younan
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Linear Elastic Fracture Mechanics ◽  
Operating Conditions ◽  
Specimen Thickness ◽  
Crosshead Speed ◽  
Linear Elastic ◽  
Piping Systems ◽  
Elastic Fracture ◽  
Point Bend

The main purpose of the present paper is to compare between the fracture toughness based on linear elastic fracture mechanics (GIC), and that based on nonlinear fracture mechanics (JIC). The material of the investigated pipe is a high-density polyethylene (HDPE), which is commonly used in natural gas piping systems. The welds at the pipe junction are produced by butt-fusion (BF), welding. Curved three-point bend (CTPB), fracture specimens are used. The crosshead speed ranged from 5 to 500 mm/min and specimen thickness ranged from 9 to 45mm for both welded and unwelded specimens at room temperature Ta, equal 23°C. The study reveals that the crosshead speed has a significant effect on the fracture toughness of both welded and unwelded specimens. The results of GIC for different specimen thickness and crosshead speed found previously by the authors [1] have been compared with JIC under the same operating conditions [2]. The comparison between welded and unwelded specimens revealed that in the welded specimens there is a marginal difference between fracture toughness measured using linear elastic fracture mechanics LEFM and elastic plastic fracture mechanics EPFM, for both crosshead speeds.

Prediction of Lower Bound Fracture Toughness in the Transition Temperature Region by T33-Stress

2012 ◽  
Author(s):  
Kai Lu ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Lower Bound ◽  
Temperature Region ◽  
Failure Criterion ◽  
Large Strain ◽  
Specimen Thickness ◽  
Fracture Toughness Test ◽  
Out Of Plane ◽  
Planar Failure

It is well known that the fracture toughness Jc in the ductile-to-brittle transition temperature region depends highly on the specimen thickness (hereafter, TST). The TST effect on Jc, which Wallin [1] described as Jc (∝ KJc2) ∝ B(-1/2) (Jc was calculated from the equations outlined in ASTM E1820 [2], KJc was derived from Jc as KJc = (Jc·E′)1/2; E′ = E/(1−ν2), B: TST), has been reproduced by Anderson et al. [3] based on the weakest link model. However, as Anderson et al. [3] themselves admit, Jc does not decrease indefinitely with B. On the other hand, Meshii et al. [4–6] tried to explain this TST effect on Jc as a mechanical issue. They obtained the same relationship, Jc ∝ B(-1/2) from the fracture toughness test for a non-standard CT and 3PB specimen (non-standard on the point that planar configuration was identical and thickness to width ratio B/W was varied from 0.25 to 0.5) and the stress intensity factor (SIF) corresponding to fracture load Pc denoted as Kc (Kc was calculated from the equations outlined in ASTM E399 [7]), was almost constant for TST. They also reproduced the experimental tendency by large strain FEA under the assumption based on their experimental observation that Kc was independent of TST. In addition, they expressed the TST effect on Jc by correlating Jc with the out-of-plane elastic T-stress T33. We thought that if TST effect on Jc is a mechanical issue, the lower bound Jc for TST could be predicted by FEA under some assumption such as Kc = constant for TST, and the TST corresponding to the lower bound Jc could be predicted by T33. However, before proceeding to this prediction, we thought we have to understand the candidate assumption for prediction more deeply, i.e, understand why Kc was constant for TST. Thus in this work, we attempted to explain the reason why Kc was constant for TST. Our idea was to apply the well-known “planar” failure criterion to our out-of-plane TST issue. After demonstrating our idea was valid, the lower bound Jc of carbon S55C for non-standard 3PB specimen was predicted based on this planar failure criterion and the large strain elastic-plastic FEA. The results showed that Jc showed a lower bound for specimen of B/W ≥ 1.5. In addition, it was shown that this threshold B/W could be estimated by the elastic out-of-plane T33.

scholarly journals Strength and Fracture Resistance of Amorphous Diamond-Like Carbon Films for MEMS

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
K. N. Jonnalagadda ◽  
I. Chasiotis
Keyword(s):  
Fracture Toughness ◽  
Mechanical Strength ◽  
Mixed Mode ◽  
Carbon Films ◽  
Mode I ◽  
Diamond Like Carbon ◽  
Specimen Thickness ◽  
Mode I Fracture Toughness ◽  
Theoretical Predictions ◽  
Failure Properties

The mechanical strength and mixed mode I/II fracture toughness of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) films, grown by pulsed laser deposition, are discussed in connection to material flaws and its microstructure. The failure properties of ta-C were obtained from films with thicknesses 0.5–3 μm and specimen widths 10–20 μm. The smallest test samples with 10 μm gage section averaged a strength of 7.3±1.2 GPa, while the strength of 20-μm specimens with thicknesses 0.5–3 μm varied between 2.2–5.7 GPa. The scaling of the mechanical strength with specimen thickness and dimensions was owed to deposition-induced surface flaws, and, only in the smallest specimens, RIE patterning generated specimen sidewall flaws. The mode I fracture toughness of ta-C films isKIc=4.4±0.4 MPam, while the results from mixed mode I/II fracture experiments with cracks arbitrarily oriented in the plane of the film compared very well with theoretical predictions.

Finite Element Analyses for Thickness Effects on J-Integral Testing using Non-Standard Testing Specimens

2004 ◽  
Vol 261-263 ◽  
pp. 693-698
Author(s):  
J.S. Kim ◽  
Young Jin Kim ◽  
S.M. Cho
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Three Dimensional ◽  
Specimen Thickness ◽  
J Integral ◽  
Finite Element Analyses ◽  
Single Edge ◽  
Fracture Toughness Testing ◽  
Standard Testing ◽  
Toughness Testing

This paper compiles solutions of plastic η factors for standard and non-standard fracture toughness testing specimens, via detailed three-dimensional (3-D) finite element (FE) analyses. Fracture toughness testing specimens include a middle cracked tension (M(T)) specimen, SE(B), single-edge cracked bar in tension (SE(T)) and C(T) specimen. The ligament-to-thickness ratio of the specimen is systematically varied. It is found that the use of the CMOD overall provides more robust experimental estimation than that of the LLD, for all cases considered in the present work. Moreover, the estimation based on the load- CMOD record is shown to be insensitive to the specimen thickness, and thus can be used for testing a specimen with any thickness.

Warm Pre-Stress Effect Measured at Irradiated RPV Weld Material

2005 ◽  
Author(s):  
Elisabeth Keim ◽  
Reinhard Langer ◽  
Hilmar Schnabel ◽  
Reinhard Bartsch
Keyword(s):  
Fracture Toughness ◽  
Power Plants ◽  
Large Scale ◽  
Load Capacity ◽  
Specimen Thickness ◽  
Test Machine ◽  
Stress Effect ◽  
Load Path ◽  
Pressurized Water ◽  
Opening Load

The recently initiated German project CARISMA (Crack Initiation and Arrest of Irradiated Steel Materials) will create a data base on pre-irradiated original materials of the four generations of German nuclear pressurized water reactors, which allows the examination of the consequences if the Master Curve instead of the RTNDT concept is applied. Several original materials of the four generations of German nuclear power plants (typical for KWO, KKS - Biblis A, Biblis B, KKU - KKG, KWG, KKP2, KBR - KKE, KK12, GKN2) will be investigated. They have been irradiated in six large scale irradiation capsules in a German research reactor (the VAK plant) at corresponding plant conditions. The capsules contain regular tensile and Charpy impact specimens as well as Pellini and fracture toughness wedge opening load specimens up to a specimen thickness of 100 mm. The first fracture toughness tests have been performed on a weld metal NiCrMo1 UP(mod.)/LW320, LW340 (1. generation, lower bound of the weld materials)—with a fluence Φ = 2,12E19 cm−2 (E > 1 MeV). This weld has a Cu-content of 0.22 wgt.% and it was therefore supposed to show a large transition temperature shift. Some fracture toughness tests in the irradiated material condition were already available and during this project four 100 mm thick wedge opening load (WOL) specimens were tested. At one of the specimens brittle failure could not be achieved during the test, because the load capacity of the test machine was exceeded. Therefore the specimen was loaded by a load-unload-cool-fracture load path to demonstrate the warm pre-stress effect of this highly irradiated specimen. At the final fracture of the specimen at a lower temperature, the failure load was significantly higher than the original one (factor 3 higher), which clearly indicates that the benefit of warm pre-stressing will not be eroded with irradiation.

Prediction of Fracture Toughness Temperature Dependence Over a Wide Temperature Range Using Simplified and Direct Scaling Method

2018 ◽  
Author(s):  
Takashi Inoue ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Wide Temperature Range ◽  
Fracture Load ◽  
Specimen Thickness ◽  
Temperature Range ◽  
Direct Scaling ◽  
Wide Range ◽  
Mc Method

The fracture toughness KJc of the material in the ductile to brittle transition temperature (DBTT) range exhibits both test specimen thickness (TST) dependence and temperature dependence. Attention has been paid to the master curve (MC) method, which provides an engineering approach to address these two issues. Although MC is intended to be applied to arbitrary ferritic material whose yield stress is within the range of 275 to 825 MPa, the KJc value must be obtained to determine the material dependent reference temperature T0. The applicable range of MC method is restricted to T0 ± 50 °C. Previous studies indicate that additional pre-tests to obtain T0 are necessary; thus, there might be some unwritten requirement to the test temperature for the KJc temperature dependence prediction in MC method to work effectively. If testing must be conducted for the material of interest at some restricted temperature, a more flexible KJc temperature dependence prediction can possibly be obtained for a wide temperature range in the DBTT range, if the simplified and direct scaling (SDS) method, which predicts fracture “load” from yield stress temperature dependence proposed previously is applied. In this study, the SDS method was applied to two different steels: Cr-Mo steel JIS SCM440 and 0.55% carbon steel JIS S55C. Both tensile and fracture toughness tests were performed over a wide range of temperatures, specifically, −166 to 100 °C for SCM440 and −166 to 20 °C for S55C. The SDS method (i.e., fracture load is proportional to 1/(yield stress)) was initially validated for the specimens in the DBTT range. Finally, a simplified method was proposed and initially validated to predict the KJc temperature dependence, by applying the SDS using the EPRI plastic J functional form.

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