THE EFFECT OF HEAT TREATMENT ON THE FRACTURE TOUGHNESS AND SUBCRITICAL CRACK GROWTH CHARACTERISTICS OF A 350-GRADE MARAGING STEEL

1969 ◽  
Author(s):  
C. S. Carter
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Crack Growth ◽  
Maraging Steel ◽  
Subcritical Crack Growth ◽  
Growth Characteristics

Influence of the initial damage on fracture toughness and subcritical crack growth in a granite rock

2020 ◽  
Author(s):  
Salvatore D'Urso ◽  
Lucas Pimienta ◽  
François Passelègue ◽  
Federica Sandrone ◽  
Sergio Vinciguerra ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Thermal Damage ◽  
Internal Damage ◽  
Initial Damage

<p>Fracture mechanics is an important tool to assess the slope stability, since this approach offers a methodology to study the fracture stress field in the neighborhood of the joint tips and accurately predict propagation of the joints over time. While the fracture toughness of material has been extensively studied in the past, low interest was given to the influence of initial damage on the subcritical crack growth, despite of its relevance to assess long term slope stability. Here we report new experimental results that address this question.</p><p>Starting from the real case of unstable rock mass of “Madonna del Sasso” (Colombero et al., 2015), a series of Cracked Chevron Notched Brazilian Disc (CCNBD) (Fowell, 1995) specimens were failed in a standard Mode I tensile test to investigate the effects of thermal damage on fracture toughness and subcritical crack growth on samples of granite of Alzo.</p><p>The degree of initial damage was imposed using slow heat treatment (1°C/min) up to 100, 200, 300 and 400°C, to emulate different levels of rock degradation. The samples were equipped with strain gauges close to the tips of the notch, an extensometer for the Crack Mouth Opening Displacement (CMOD) and twelve Acoustic Emission recorders.</p><p>Our results show that fracture toughness decreases with increasing thermal damage, in agreement with previous studies (Nasseri, Schubnel, & Young, 2007). The fracture toughness of undamaged granite is 1.04 MPa m<sup>1/2</sup>, but 0.65 MPa m<sup>1/2</sup> after treatment up to 400°C.</p><p>Subcritical crack growth behaviour has been studied for samples treated from 100°C up to 400°C through creep tests on CCNBD specimens. The overall effect of heat treatment is to increase the crack growth rate in granite for a given stress intensity factor. The slopes of stress intensity factor versus crack velocity curves are sensitive to modifications of initial damage’s degree. Trend drops substantially with increase of the temperature of the heat treatment. This shows a substantial increase of the internal damage index n, and a decrease of the time to failure of the CCNBD specimens.</p><p>The study highlights the importance of considering both the time-dependent slope behaviour and effects of rocks internal damage, since these conditions could lead to an unexpected premature failure.</p>

Fracture toughness and fatigue crack growth characteristics of nanotwinned copper

2011 ◽  
Vol 59 (6) ◽  
pp. 2437-2446 ◽  
Author(s):  
A. Singh ◽  
L. Tang ◽  
M. Dao ◽  
L. Lu ◽  
S. Suresh
Keyword(s):  
Fracture Toughness ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Characteristics

Mechanical Performance of Heat Treated Ti-6Al-4V Friction Stir Welds

2010 ◽  
Vol 436 ◽  
pp. 213-221 ◽  
Author(s):  
Paul Edwards ◽  
Marc Petersen ◽  
Mamidala Ramulu ◽  
Rodney Boyer
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Crack Growth ◽  
Mechanical Performance ◽  
Heat Treatment Condition ◽  
Parent Material ◽  
Fusion Welding ◽  
Fatigue Properties ◽  
Metallographic Analysis ◽  
Friction Stir

Heat treatment processes for standard fusion welding techniques in titanium are well established, but the optimal heat treatment for Friction Stir Welded titanium has not been evaluated. In this study, 6 mm thickness titanium 6Al-4V butt welds were subjected to heat treatments ranging from 700 to 900 C. Results of the metallographic analysis for each heat treatment condition will be presented in addition to microhardness, tensile and fatigue properties. It was found that increased heat treatment temperatures lead to lower hardness and tensile strengths, higher elongation to failure and improved high cycle fatigue performance. Furthermore, fracture toughness and crack growth tests were performed for welds subjected to a standard post-weld stress relief. The fracture toughness was lower than the parent material, but crack growth rates in the weld were similar to that of the base metal.

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