The Fracture Toughness of Hardened Tool Steels

1987 ◽  
Vol 109 (4) ◽  
pp. 314-318 ◽  
Author(s):  
D. F. Watt ◽  
Pamela Nadin ◽  
S. B. Biner
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Slow Crack Growth ◽  
Crack Opening ◽  
Compact Tension ◽  
Testing Procedure ◽  
Tool Steels ◽  
Opening Displacement ◽  
Tempering Temperature ◽  
Toughness Testing

This report details the development of a three-stage fracture toughness testing procedure used to study the effect of tempering temperature on toughness in 01 tool steel. Modified compact tension specimens were used in which the fatigue precracking stage in the ASTM E-399 Procedure was replaced by stable precracking, followed by a slow crack growth. The specimen geometry has been designed to provide a region where slow crack growth can be achieved in brittle materials. Three parameters, load, crack opening displacement, and time have been monitored during the testing procedure and a combination of heat tinting and a compliance equation have been used to identify the position of the crack front. Significant KIC results have been obtained using a modified ASTM fracture toughness equation. An inverse relationship between KIC and hardness has been measured.

Influence of Sulfur Content on the Fracture Toughness Properties of 2 1/4 Percent Cr-1 Percent Mo Steel

1976 ◽  
Vol 98 (2) ◽  
pp. 135-142 ◽  
Author(s):  
J. F. Copeland
Keyword(s):  
Fracture Toughness ◽  
Sulfur Content ◽  
Detrimental Effect ◽  
Crack Opening ◽  
Analytical Techniques ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Tension Specimen ◽  
Microvoid Coalescence ◽  
Opening Displacement

The effects of sulfur content on the fracture toughness properties of 2 1/4Cr-1 Mo steel were evaluated at test temperatures above, at, and below the nil ductility transition temperature (NDTT) of −23°C (−10°F). Small, 12.7-mm (0.5-in.) thick compact tension specimen results were combined with J-integral, Equivalent Energy, and Crack Opening Displacement analytical techniques to provide KIc results up to 22°C (72°F). It was found that the sulfur content of this steel has a large detrimental effect on KIc at the NDTT and above, where microvoid coalescence is the fracture mode. Sulfur has no significant effect at −73°C (−100°F) where cleavage occurs. These results also indicate that the higher Charpy V-notch energy at NDTT, shown by lower sulfur steels, is translatable into increased fracture resistance.

Mode Mixity in the Fracture Toughness Evaluation of Heat-Affected-Zone Material Using SEN(T) Experiment

2021 ◽  
Author(s):  
Sureshkumar Kalyanam ◽  
Yunior Hioe ◽  
Gery Wilkowski
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Heat Affected Zone ◽  
Crack Opening ◽  
Growth Direction ◽  
Mode I ◽  
Mode Ii ◽  
Mode Mixity ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement

Abstract SEN(T) specimens provide good similitude for surface cracks (SC) in pipes, where a SC structure has lower constraint condition than typically used fracture toughness specimens such as SEN(B) , and C(T). Additionally, the SENT specimen eliminates concern of material anisotropy since the crack growth direction in the SENT is the same as in a surface-cracked pipe. While the existing recommended and industrial practices for SEN(T) have been developed based on assumption of homogenous or mono-material across the crack, their applicability for the evaluation of fracture toughness of heat-affected-zone (HAZ) were evaluated in this investigation. When conducting tests on SEN(T) specimens with prescribed notch/crack in the HAZ, the asymmetric deformation around the crack causes the occurrence of a combination of Mode-I (crack opening) and Mode-II (crack in-plane shearing) behavior. This mode mixity affects the measurement of the crack-tip-opening-displacement (CTOD) and evaluation of elastic-plastic fracture mechanics parameter, J. The CTOD-R curve depicts the change in toughness with crack growth, in a manner similar to the J-R curve methodology. The experimental observations of Mode-I and Mode-II behavior seen in tests of SEN(T) specimens with notch/crack in the HAZ and as the crack propagates through the weld/HAZ thickness were investigated. The issues related to and the changes needed to account for such behavior for the development of recommended practices or standards for SEN(T) testing of weld/HAZ are addressed.

Experimental Investigation Into the Fracture Toughness of Polyethylene Pipe Material

2004 ◽  
Author(s):  
Ihab Mamdouh Graice ◽  
Maher Y. A. Younan ◽  
Soheir Ahmed Radwan Naga
Keyword(s):  
Fracture Toughness ◽  
Crack Opening ◽  
Experimental Tests ◽  
Compact Tension ◽  
Test Method ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Specimen Thickness ◽  
Pipe Material ◽  
Opening Displacement

The mechanical behavior of the recently produced gas pipes material PE100 is investigated and compared to the commonly used material PE80 to determine their relative advantages. The two materials show plastic behavior at room temperature. The fracture toughness of the two materials is experimentally determined using the two common elastic plastic fracture mechanics methods: the ASTM multiple specimen test method for determining the J-R curve of the materials, and the crack opening displacement (COD) method. The investigation of the fracture behavior of the two materials includes the effect of the specimen thickness as well as specimen configuration. The experimental tests were carried on the compact tension (CT) specimens and the single edge notch bending (SENB) specimens. At −70°C, the materials show elastic behavior, the ASTM test method for determining fracture toughness is applied to SENB specimens to determine KIC of both materials. PE80 shows greater resistance to fracture than PE100.

Assessment of Fracture Toughness and Fatigue Crack Growth Threshold of a Welded Joint Constituent of a Steam Turbine LP Rotor

2014 ◽  
Author(s):  
M.-H. Herman Shen ◽  
Sajedur Akanda ◽  
Xia Liu ◽  
Peng Wang
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Steam Turbine ◽  
Crack Growth ◽  
Welded Joint ◽  
Crack Opening ◽  
Crack Size ◽  
Turbine Rotor ◽  
Opening Displacement ◽  
Stable Crack Propagation

In order to ensure safety and reliability of steam turbine welded rotors, the present investigation focuses on evaluation of crack initiation, growth, and resistance parameters of base metal (BM), weld metal (WM) and heat affected zone (HAZ) of a steam turbine rotor welded joint constituent. The experimental part consists of three-point bending conducted on single edge notch bend specimens to induce stable crack propagation. The crack size was calculated by incorporating the crack opening displacement measured by a clip-gage, in a compliance method. The fatigue crack threshold was obtained from a crack growth rate curve according to ASTM E647 and the fracture toughness was determined from a J-based resistance curve according to ASTM E1820. From the experimental results the fatigue crack threshold is found to be a function of loading ratio rather than a single material parameter. From the fracture toughness results, the WM and the BM are found to have similar KIc values whereas HAZ is found to have slightly better KIc values although HAZ had little crack extension during the experiments.

scholarly journals Fracture toughness and crack growth of brackish ice using chevron-notched specimens

1994 ◽  
Vol 40 (135) ◽  
pp. 415-426
Author(s):  
Lars Stehn
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Crack Opening ◽  
Initial Crack ◽  
Effect Study ◽  
Small Scale ◽  
Opening Displacement ◽  
Critical Crack ◽  
Experimental Calibration ◽  
Brackish Ice

AbstractField-test equipment called FIFT (a Field Instrument for Fracture toughness Tests on ice) was used in both field and laboratory fracture-toughness tests on brackish sea ice from the Gulf of Bothnia. An experimental calibration was performed and a compliance expression was then derived for the Short Rod Chevron Notched (SRCN) specimen. Using the SRCN configuration, for which the initial crack growth is shown to be stable, and measured load-point displacements, preliminary crack-growth velocities are found. The obtained estimated crack velocity is, on average,ȧe= 20 ms−1, albeit with a large standard deviation. The results indicate that critical crack (crack-jumping) growth occurs. The apparent fracture toughness,KQ, was found to have a pronounced dependency on porosity in the form of brine volume. The results obtained are derived from a linearly elastic fracture mechanics (LEFM) theory. Consequently, the tests were designed to satisfy small-scale yielding requirements in terms of notch sensitivity and brittleness. The linearity of the load vs crack-opening displacement curves together with a size-effect study, showing that the specimen is notch-sensitive for grain-sizes ranging from 1.6 to nearly 100 mm, indicate that LEFM could be applicable.

Master Curve Testing on Reconstituted Surveillance Charpy Specimens

2018 ◽  
Author(s):  
Ferenc Gillemot ◽  
Márta Horváth ◽  
Ákos Horváth ◽  
Ildikó Szenthe ◽  
Attila Kovács
Keyword(s):  
Fracture Toughness ◽  
Master Curve ◽  
Evaluation Method ◽  
Crack Opening ◽  
Base Material ◽  
Charpy Impact ◽  
Testing Procedure ◽  
Transition Curve ◽  
Radiation Embrittlement ◽  
Opening Displacement

The original WWER-440 surveillance had 6 sets of specimens and each set had 12 Charpy, 12 COD (crack opening displacement) and 6 tensile specimens made from base material, weldment and HAZ (heat affected zone). The Charpy size precrack TPB (three point bend) COD specimens were located at the end of the chains, where the flux is rapidly decreasing. During the period of 1970–90, when the WWER-440-V213 units were designed, built and started to operate, the Charpy impact transition curve measurement was the accepted method to evaluate the radiation embrittlement. The technology and the standards to use small size fracture mechanical specimens in surveillance capsules were not developed at the time period when most of the second generation reactors — including the WWER-440 V 213 type — were designed, therefore the fracture toughness specimens were considered less interesting for the utilities and the safety authorities. Fracture toughness curves were elaborated in the laboratories on large size unirradiated specimens and radiation embrittlement adjustments were made according to the Charpy shift. However, during the past 30 years fracture mechanics has rapidly developed, and the testing moved to the direction of using small and mini sized specimens. The development of the Master Curve evaluation method [4,5] allowed the use of small specimens for fracture toughness testing in surveillance programs, and the results obtained on irradiated specimens may be used directly in the lifetime evaluation. The purpose of this work was to develop a specimen production technology and testing procedure to measure these data using the remnants of irradiated surveillance Charpy specimens, and the comparison of the data calculated from CMOD and LLD on irradiated CrMoV type RPV material and weldment.

Numerical Simulation and Experimental Investigation of Damage Behaviour on Al6061 Laser Welded Joints

2014 ◽  
Vol 627 ◽  
pp. 105-108
Author(s):  
H.Y. Tu ◽  
Siegfried Schmauder ◽  
Ulrich Weber
Keyword(s):  
Numerical Simulation ◽  
Fracture Toughness ◽  
Welded Joints ◽  
Welded Joint ◽  
Volume Fraction ◽  
Crack Opening ◽  
Compact Tension ◽  
Void Volume Fraction ◽  
Opening Displacement ◽  
Hardness Tests

The ductile damage behaviour of an aluminium laser welded joint is studied experimentally and numerically. The dimensions of the weld regions are fixed by hardness tests. Fracture toughness tests of Al6061 laser beam welded joints were performed with the compact tension (C(T)) specimens. The Rousselier model is used and the parameters: initial void volume fraction (f0) and average void distance (lc) are identified by metallographic investigations, for the BM, the FZ and the HAZ. Numerical calibration of the Rousselier parameters is performed on notched round specimens. The same Rousselier parameters are used to predict force vs. Crack Opening Displacement (COD) of C(T) specimens.

Experimental Investigation Into the Fracture Toughness of Polyethylene Pipe Material

2005 ◽  
Vol 127 (1) ◽  
pp. 70-75 ◽  
Author(s):  
Ihab Mamdouh Graice ◽  
Maher Y. A. Younan ◽  
Soheir Ahmed Radwan Naga
Keyword(s):  
Fracture Toughness ◽  
Crack Opening ◽  
Experimental Tests ◽  
Compact Tension ◽  
Test Method ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Specimen Thickness ◽  
Pipe Material ◽  
Opening Displacement

The mechanical behavior of the recently produced gas pipes material PE100 is investigated and compared to the commonly used material PE80 to determine their relative advantages. The two materials show plastic behavior at room temperature. The fracture toughness of the two materials is experimentally determined using the two common elastic plastic fracture mechanics methods: the American Society for Testing and Materials (ASTM) multiple specimen test method for determining the J-R curve of the materials, and the crack opening displacement method. The investigation of the fracture behavior of the two materials includes the effect of the specimen thickness as well as specimen configuration. The experimental tests were carried on the compact tension specimens and the single edge notch bending (SENB) specimens. At −70°C, the materials show elastic behavior, the ASTM test method for determining fracture toughness is applied to SENB specimens to determine KIC of both materials. PE80 shows greater resistance to fracture than PE100.

Sign in / Sign up

Export Citation Format

Share Document