Fatigue/Creep Interactions in Ni3Al-Base Alloys

1988 ◽  
Vol 133 ◽  
Author(s):  
G. M. Camus ◽  
D. J. Duquette ◽  
N. S. Stoloff
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Frequency Effect ◽  
Propagation Mode ◽  
Crack Blunting ◽  
Fatigue Crack Growth Test

ABSTRACTStress-controlled fatigue tests and fatigue crack growth rate tests respectively have been carried out on two Ni3Al Cr/Zr alloys, IC 218 at 600°C and 800°C, and IC 221 at 800°C, in vacuum, at various test frequencies. Decreasing the test frequency and/or increasing the temperature leads to a decrease in the number of cycles to failure, and a gradual disappearance of a fatigue fracture zone. In fatigue crack propagation tests, the crack growth rate only decreases at the lowest frequency and remains constant in the major part of the frequency range investigated. The fatigue propagation mode in all cases is intergranular. These trends are shown in both cases to be related to a true creep component but, under fatigue crack growth test conditions, crack blunting intervenes gradually as the frequency is decreased, leading therefore to a less severe frequency effect.

Effect of KIII on Fatigue Crack Growth Behavior

2010 ◽  
Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Chikako Ohdama
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Crack Growth Simulation ◽  
Slant Surface ◽  
Cracked Specimens

Mixed mode fatigue tests are conducted using surface cracked specimen. Slant surface cracked specimens are made where crack angle is 15°, 30°, 45° and 60°. It is shown that factory roof is made at deepest point of surface crack due to ΔKIII, and crack growth rate decreases by the factory roof. Fatigue crack growth is simulated using S-version FEM (Finite Element Method) using crack growth criteria. It is shown that conventional crack growth criteria are not available to predict fatigue crack growth with factory roof. In this study, modified criterion for the prediction of crack growth rate is proposed. By using this criterion, fatigue crack growth simulation is conducted, and results are compared with those of experiments and discussed.

Fatigue Crack Growth Rate in Low ΔK Range According to the Microstructure and Temperature in P122 Alloy Weldment

2007 ◽  
Vol 353-358 ◽  
pp. 545-548
Author(s):  
Si Yon Bae ◽  
Bum Joon Kim ◽  
Byeong Soo Lim
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Power Plant ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Thermal Efficiency ◽  
Critical Power ◽  
Fatigue Tests

There exists strong environmental and economic pressure to increase the thermal efficiency of fossil fuel power stations and this has led to a steady increase in operating temperature and pressure resulting in the world wide construction plans for ultra super-critical power plants. Consequently, in order to improve the thermal efficiency of power plant, there has been a strong drive to develop more advanced heat resistant steels with excellent creep, high temperature fatigue and thermal fatigue resistant properties as well as superior oxidation and corrosion resistant properties. In this study, the test material was P122 alloy which was developed for ultra super-critical power plant. To measure the fatigue crack growth rate in low #K range, fatigue tests were performed on the P122 alloy welds by #K decreasing method at three different microstructure (Base metal, HAZ, Weld metal) regions. Microstructure observation and micro-hardness tests performed for all three regions to find the relationship among the crack growth rate, microstructure and hardness. Fatigue tests were performed with compact tension specimens at 600°C, 650°C and 700°C at the loading frequency of 20Hz.

Effect of Water or Soap Solution on Fatigue Crack Growth in Welded Steel

2012 ◽  
Author(s):  
Radu Dimitriu ◽  
Stephen Maddox
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Soap Solution ◽  
Tap Water ◽  
Water Pressure ◽  
Fatigue Tests

It is common practice to conduct fatigue tests on full-scale girth welded pipes in resonance bending with a static axial mean stress induced by internal water pressure. Clean tap water is used, which gradually stagnates with time during a long endurance test, and therefore it is generally assumed that it has no significant effect on the fatigue lives of cracks propagating from the inside. However, important conclusions are drawn from such tests, especially when they relate to risers, and therefore there is a need to check this. In a different context there is a similar need to check the effect of soap solution on fatigue. This is often applied during fatigue tests on welded joints that fail from an accessible weld toe as an aid to crack detection. Furthermore, it may continue to be applied when a crack has been detected in order to produce beachmarks on the fatigue fracture surface by staining. The present paper presents the results of a series of fatigue crack growth rate (FCGR) tests that aimed to establish the effects of clean water or soap solution on the fatigue performance of welded structural steel. The tests were carried out on standard single edge-notched bend (SENB) specimens machined from girth welds in X65 grade steel pipe. Comparative tests were conducted at ambient temperature in air, tap water, de-ionized water and soap solution environments. Noting the general finding that corrosion-fatigue crack growth rate increases with decrease in load cycling frequency, the influence of frequency between 0.1 and 10Hz was investigated.

Evaluation of Excessive Loading Effect on Fatigue Crack Growth Behavior Based on Crack Blunting and Stress Distribution in Front of the Crack Tip

2013 ◽  
Author(s):  
Yoshihito Yamaguchi ◽  
Jinya Katsuyama ◽  
Kunio Onizawa ◽  
Yinsheng Li
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Stress Distribution ◽  
Crack Growth ◽  
Compressive Load ◽  
Crack Tip ◽  
Crack Growth Behavior ◽  
Crack Blunting

It is very important to establish an evaluation method of the structural integrity of piping beyond the small scale yielding condition due to large earthquakes. One of the key issues is the effect of excessive loading on the fatigue crack growth behavior. We performed fatigue crack growth tests under constant amplitude cyclic loading with a single excessive tensile/compressive load. The stress distribution in front of crack tip and crack blunting were estimated by FEM analyses. After the crack tip was blunted by the excessive tensile loading, the effect of the excessive loading on crack growth rate varied depending on the magnitude of the subsequent compressive loading. When a compressive load is enough to close the crack, the crack growth rate became higher than that before the excessive tensile loading while increasing the tensile stress in front of crack tip. A crack growth prediction method has been proposed considering the effects of the excessive loading based on the variation of the stress distribution in front of crack tip and the crack blunting. The predicted crack growth rate by the proposed method was correlated with the experimental ones.

Effect of KIII on Fatigue Crack Growth Behavior

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Chikako Ohdama
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Crack Growth Simulation ◽  
Slant Surface ◽  
Cracked Specimens

In this study, mixed-mode fatigue tests are conducted using surface-cracked specimens. Slant surface-cracked specimens are prepared with crack angles of 15 deg, 30 deg, 45 deg, and 60 deg. It is shown that a “factory roof” fracture is formed at the deepest point of the surface crack due to ΔKIII and causes the crack growth rate to decrease. Additionally, fatigue crack growth is simulated using the superposition finite element method (FEM) with crack growth criteria. It is shown that conventional crack growth criteria are not applicable to factory roof fractures. Finally, a modified criterion for the prediction of crack growth rate is proposed, fatigue crack growth simulation is conducted using this criterion, and the results are compared with experimental results.

Sign in / Sign up

Export Citation Format

Share Document