共查询到20条相似文献,搜索用时 15 毫秒
1.
Chang Min Suh Robert O. Ritchie Young Goo Kang 《Journal of Mechanical Science and Technology》1989,3(2):78-85
Fatigue tests by axial loading (R-0.05) were carried out to investigate short fatigue crack growth behavior in 2 1/4 Cr-1 Mo steel at room temperature using smooth and a small notched flat specimen. All the data of the fatigue crack growth rate in the present tests were analyzed as a function of the stress intensity factor equation in conjunction with crack closure behavior. Analysis was performed accounting for the relation of surface effective stress range,Ua and depth effective stress range,Ub. In the case of isotropic crack growth properties,Ub=(ΔKta/ΔKtb) ·Ua. By use ofUb obtained from the analysis, crack growth rates to surface direction coincide with those of depth direction. 相似文献
2.
《Wear》1986,107(3):245-262
Fretting fatigue and normal, or unfretting, fatigue tests of a stainless steel SUS304L and an aluminium alloy A2024-T3 were carried out to investigate the effects of the contact pressure and the stress ratio on the crack propagation behaviour. The crack propagation behaviour was represented by the crack propagation rate da/dNversus the crack length a or the stress intensity factors ΔKeff and Kmax In fretting fatigue, crack propagation was divided into two stages, namely SI and SII. The value of da/dN in the SI stage was very high, even under a stress intensity factor less than the threshold for normal fatigue, and decreased gradually with crack growth because of crack closure and the decreasing fretting effect. The decrease in da/dN was marked in the case of high contact pressure and low stress ratio such as when R = −0.33, where R denotes the minimum stress divided by the maximum stress. During fretting fatigue crack closure occurred at an oblique short crack in the early stages of crack propagation in both the SUS304L steel and the A2024-T3 alloy; it also occurred at the oblique cracked surface of the shear lips formed in the A2024-T3 alloy during crack growth. However, in the SII stage, which followed the SI stage, da/dN increased with crack growth as for normal fatigue. 相似文献
3.
Generally the fretting fatigue S-N curve has two regions: one is the high cycle (low stress) region and the second is the low cycle (high stress) region. In a previous paper we introduced the fretting fatigue life estimation methods in high cycle region by considering the wear process; with this estimation method the fretting fatigue limit can be estimated to be the crack initiation limit at the contact edge. In this paper we estimate the low cycle fretting fatigue life based on a new critical distance theory, modified for a high stress region using ultimate tensile strength σB and fracture toughness KIC. The critical distance for estimating low cycle fretting fatigue strength was calculated by interpolation of the critical distance on the fretting fatigue limit (estimated from σw0 and ΔKth) with critical distance on static strength (estimated from σB and KIC). By unifying this low cycle fretting fatigue life estimation method with the high cycle fretting fatigue life estimation method, which was presented in the previous paper, we can estimate the total fretting life easily. And to confirm the availability of this estimation method we perform the fretting fatigue test using Ni-Mo-V steel. 相似文献
4.
Bumjoon Kim Jonghoon Lee Jiwoo Im Jongbum Kim Moonki Kim Hakjoon Kim Sungjin Song Byeongsoo Lim 《Journal of Mechanical Science and Technology》2012,26(10):3091-3096
In this work, we examined the influence of microstructural changes, such as an intermetallic sigma (??) phase, on the fatigue behavior of high-temperature aged AISI 316L stainless steel. Nondestructive ultrasonic test and fatigue crack growth tests were performed to determine the threshold stress intensity factor of these artificially aged specimens. Ultrasonic test results characterizing the microstructural changes were compared with those of the fatigue tests to propose an empirical formula capable of predicting the threshold stress intensity factor by a nondestructive method. We observed a strong correlation between the increase in the volume fraction of the ?? phase and the decrease of ??Kth. Ultrasonic velocity increased in response to the coarsening behavior of the ?? phase in the vicinity of the grain boundaries. 相似文献
5.
Yong-Bok Lee Aslak Siljander Frederick V. Lawrence 《Journal of Mechanical Science and Technology》1992,6(2):81-87
The tensile, fracture toughness and fatigue properties of Al−Si 319 lost-foam-cast alloy were determined at room temperature.
The fatigue properties of this alloy were also determined at 150°C. Fatigue cracks were always initiated at the largest casting
pore. Initial pore sizes were measured using a scanning electron microscope. Surface replication showed that majority of the
fatigue life was spent in fatigue crack propagation and permitted the estimation of the constants in the Paris power law and
the threshold stress intensity factor (ΔK
th
). The role of internal casting porosity was quantified using a linear elastic fracture mechanics (LEFM) model for fatigue
crack growth. The predicted lives agreed with the measured values within a factor of two. 相似文献
6.
Jeong-Hwan Lee Hyeong-Yeon Lee Seong-Gu Hong Soon-Bok Lee 《Journal of Mechanical Science and Technology》2017,31(8):3665-3669
The fatigue crack growth behavior of Mod.9Cr-1Mo steel was investigated as a function of temperature, loading frequency and R ratios in the Paris regime. The relationship between fatigue crack growth rate and stress intensity factor range was acquired for each test condition. The results revealed that crack growth rate was accelerated with increasing temperature and decreasing loading frequency. The influence of the R ratio on crack growth rate was only pronounced at the low loading frequency condition. In order to understand the crack growth mechanism, activation energy analysis and normalized ΔK analysis were performed. This study suggests that oxidation and the degradation of mechanical properties promote crack growth behavior. 相似文献
7.
In fretting fatigue process the wear of contact surfaces near contact edges occur in accordance with the reciprocal micro-slippages on these contact surfaces. These fretting wear change the contact pressure near the contact edges. To estimate the fretting fatigue strength and life it is indispensable to analyze the accurate contact pressure distributions near the contact edges in each fretting fatigue process.So, in this paper we present the estimation methods of fretting wear process and fretting fatigue life using this wear process. Firstly the fretting-wear process was estimated using contact pressure and relative slippage as follows:
W=K×P×S,