Notch-Ductility Transition of Structural Steels of Various Yield Strengths

1972 ◽  
Vol 94 (1) ◽  
pp. 299-305 ◽  
Author(s):  
A. K. Shoemaker
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Fracture Behavior ◽  
Shear Fracture ◽  
Dynamic Fracture Toughness ◽  
Structural Steels ◽  
Published Data ◽  
Specimen Thickness ◽  
Plastic Energy ◽  
Lateral Contraction

The notch-ductility transition of six structural steels, A36, ABS-Class C, A302-Grade B, HY-80, A517-Grade F, and HY-130, ranging in yield strength from 36 to 137 ksi, was studied with the use of 5/8 and 1 in. dynamic-tear (DT) test specimens. The results were compared with previously published data for V-notch and fatigue-cracked Charpy tests and dynamic fracture-toughness (KID) tests. Energy, lateral-contraction, and fracture-toughness values were compared. The results of this study showed that the full-shear upper energy shelves in the Charpy V-notch and DT specimens are the products of constant average plastic energy densities for each steel and the plastic volume estimates for the fracture of the different specimens. The transition from ductile to brittle fracture behavior is essentially the same in the fatigue-cracked Charpy and DT specimens since, for each steel, the same lateral contraction was measured in each specimen broken at a given temperature. This lateral contraction increased exponentially with temperature until a full-thickness shear fracture developed. However, the maximum lateral contraction increased with increased test-specimen thickness, suggesting that the Kc values corresponding to full-shear fracture should also increase with thickness. Using the proportionality found between the lateral contraction and the values of KID2/σYDE for the brittle-fracture behavior of these steels, the Kc values are estimated to be as much as 4.5 times greater than the KIc values at the same temperatures. In general, the notch-ductility transition can best be quantitatively characterized by the lateral contraction through KID and Kc values, whereas upper shelf energies are related by constant plastic energy densities and plastic volumes which develop during fracture.

Dynamic Fracture Toughness and Charpy Transition Properties of a Service-Exposed 2.25Cr-1Mo Reheater Header Pipe

2003 ◽  
Vol 125 (2) ◽  
pp. 227-233 ◽  
Author(s):  
P. R. Sreenivasan ◽  
C. G. Shastry ◽  
M. D. Mathew ◽  
K. Bhanu Sankara Rao ◽  
S. L. Mannan ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
Prolonged Exposure ◽  
Residual Life ◽  
Shear Fracture ◽  
Temper Embrittlement ◽  
Dynamic Fracture Toughness ◽  
Life Extension ◽  
Virgin Material ◽  
Fracture Appearance Transition Temperature

Residual life analysis of power plant components like boiler tubes, superheater outlet headers, reheater headers, steam pipes, etc., is important for life extension and avoidance of catastrophic failure. In this context, fracture toughness is very important. The fracture characteristics after prolonged exposure to high temperatures and pressures are likely to be different from that of the virgin material. 2.25Cr-1Mo reheater header pipe exposed at 813 K for 120,000 h was studied by instrumented impact tests (IIT) to evaluate dynamic fracture toughness and Charpy transition properties. The methods presented in this paper for estimating dynamic fracture toughness from IIT of Charpy specimens give reliably conservative results without the need for precracking. For estimating fracture appearance transition temperature (FATT) from IIT load-time traces, the equation for percent shear fracture, PSF3, gives the best 1:1 correlation with measured values from fracture surfaces. The lower bound equation for variation of fracture toughness with temperature derived in the present study is higher than that obtained from the FATT master curve (FATT-MC) approach. Comparison of Charpy indices like FATT and upper-shelf energy for the service exposed steel to results for the virgin material reported in the literature and the compositional J-Factor estimates for temper-embrittlement susceptibility indicate that the present steel, even after 120,000 h exposure to high temperature service, has probably undergone only very little or nil degradation in toughness properties.

Experimental Investigation on Mode II Fracture Toughness KIIC of Concrete and Fracture Behavior

2006 ◽  
Vol 324-325 ◽  
pp. 1149-1152 ◽  
Author(s):  
Shi Lang Xu ◽  
Hong Bo Gao ◽  
Xiu Fang Zhang
Keyword(s):  
Fracture Toughness ◽  
Crack Length ◽  
Fracture Behavior ◽  
Shear Fracture ◽  
Discontinuity Point ◽  
Fracture Load ◽  
Mode Ii ◽  
Mode Ii Fracture ◽  
Double Edge ◽  
Mode Ii Fracture Toughness

Using the double-edge notched geometry proposed by Xu and Reinhardt recently, the dimension of 200 mm×200 mm×100mm concrete cube specimens, of which the crack length are 10 mm, 20 mm, 30mm, 40mm, 50mm respectively, are designed to experimentally measure mode II fracture toughness KIIC of concrete. For almost all specimens, typical shear fracture features i.e. approximately 0º initial cracking angle as well the following crack forwards propagation along the direction of ligament is phenomenally observed. This fact strongly confirms that this double-edge notched geometry is validly and capable of being utilized as a mode II fracture geometry to evaluate mode II fracture behavior. Then, from the discontinuity point of the measured load-displacement plot, the critical shear fracture load Pc is determined and the corresponding mode II fracture toughness KIIC is also calculated using the formula developed by Xu and Reinhardt. The computed results show that KIIC has no dependency on initial crack length, about 3.36MPa·m1/2 for the tested specimens.

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.

Fracture Toughness JIC Prediction From Super-Small Specimens (0.2CT, 0.5MM Thick) of a Martensitic Stainless Steel HT-9

1991 ◽  
Vol 113 (1) ◽  
pp. 135-140
Author(s):  
Xingyuan Mao
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Martensitic Stainless Steel ◽  
Shear Fracture ◽  
Specimen Size ◽  
Evaluation Procedure ◽  
Specimen Thickness ◽  
Rigid Plastic ◽  
Toughness Testing ◽  
Stretch Zone Width

The fracture toughness of alloy HT-9, a martensitic stainless steel under consideration for fusion reactor applications, was determined from 0.2CT (0.5mm thick) specimens. Specimens with thicknesses of 25 (1CT), 10 (0.4CT), 3 and 0.5 (0.2CT)mm were tested to investigate the effects of specimen size on fracture toughness. 0.2CT (0.5mm thick) specimens did not satisfy ASTM E813 size requirements for a valid JIc. Fractographic examinations of the variation of stretch zone width and fracture modes along the specimen thickness were performed by scanning electron microscopy (SEM), where flat and shear fracture regions had been distinguished. A new JIc evaluation procedure for invalid specimen size is proposed using rigid plastic analysis and shear fracture measurements with fractographic observations. Predicted JIc values were compared with the JIc values obtained from valid specimen sizes. This miniaturized specimen technique may be applicable to post-irradiation fracture toughness testing.

scholarly journals Dynamic Fracture Toughness Evaluation of Structural Steels Based on the Local Approach

1998 ◽  
Vol 1998 (184) ◽  
pp. 453-464 ◽  
Author(s):  
Fumiyoshi Minami ◽  
Tomoyuki Hashida ◽  
Masao Toyoda ◽  
Jun Morikawa ◽  
Takeshi Ohmura ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Dynamic Fracture ◽  
Dynamic Fracture Toughness ◽  
Structural Steels ◽  
Local Approach ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation

Hopkinson Bar Loaded Fracture Experimental Technique: A Critical Review of Dynamic Fracture Toughness Tests

2009 ◽  
Vol 62 (6) ◽  
Author(s):  
Fengchun Jiang ◽  
Kenneth S. Vecchio
Keyword(s):  
Fracture Toughness ◽  
Stress Wave ◽  
Dynamic Fracture ◽  
Fracture Behavior ◽  
Hopkinson Bar ◽  
Dynamic Fracture Toughness ◽  
Stress Wave Propagation ◽  
Theoretical Formula ◽  
Wave Loading ◽  
Engineering Materials

Hopkinson bar experimental techniques have been extensively employed to investigate the mechanical response and fracture behavior of engineering materials under high rate loading. Among these applications, the study of the dynamic fracture behavior of materials at stress-wave loading conditions (corresponding stress-intensity factor rate ∼106 MPam/s) has been an active research area in recent years. Various Hopkinson bar loading configurations and corresponding experimental methods have been proposed to date for measuring dynamic fracture toughness and investigating fracture mechanisms of engineering materials. In this paper, advances in Hopkinson bar loaded dynamic fracture techniques over the past 30 years, focused on dynamic fracture toughness measurement, are presented. Various aspects of Hopkinson bar fracture testing are reviewed, including (a) the analysis of advantages and disadvantages of loading systems and sample configurations; (b) a discussion of operating principles for determining dynamic load and sample displacement in different loading configurations; (c) a comparison of various methods used for determining dynamic fracture parameters (load, displacement, fracture time, and fracture toughness), such as theoretical formula, optical gauges, and strain gauges; and (d) an update of modeling and simulation of loading configurations. Fundamental issues associated with stress-wave loading, such as stress-wave propagation along the elastic bars and in the sample, stress-state equilibrium validation, incident pulse-shaping effect, and the “loss-of-contact” phenomenon are also addressed in this review.

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