Microstructural Effects in the Low-Cycle Fatigue of Fe-Ni-Cr Austenite

1977 ◽  
Vol 99 (1) ◽  
pp. 29-35 ◽  
Author(s):  
N. F. Fiore ◽  
D. R. Diercks
Keyword(s):  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Hold Time ◽  
Weight Percent ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Cycle Fatigue ◽  
Cyclic Life ◽  
Localized Deformation ◽  
Cast Alloys

A series of low-cycle fatigue tests was performed at 593 deg C on Fe-20 Cr-10 Ni and Fe-20 Cr-20 Ni (in weight percent) austenitic alloys in both the cast and wrought conditions. The as-cast alloys exhibited substantially longer cyclic lives than the wrought alloys or wrought Type 304 stainless steel. An effect of Ni content on fatigue life was noted for the cast alloys, but not for the wrought. Striation, measurements indicated that the majority of the cyclic life was spent in crack initiation and early growth in all cases, and the superiority of the cast alloys was almost entirely due to a greater resistance to crack initiation. Macroscopic crack-growth rates were found to be essentially independent of composition and microstructure. A 1-min tension hold time per cycle produced a significant reduction in cyclic life in all cases except for the as-cast high Ni alloy. The decrease in life appeared to be associated with the initiation of cracks from localized deformation at grain boundaries.

Study on Life Prediction Method for Creep-Fatigue Interaction at Elevated Temperature

2007 ◽  
Vol 353-358 ◽  
pp. 190-194
Author(s):  
Nian Jin Chen ◽  
Zeng Liang Gao ◽  
Wei Zhang ◽  
Yue Bao Le
Keyword(s):  
Elevated Temperature ◽  
Prediction Model ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Hold Time ◽  
Prediction Method ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Creep Fatigue ◽  
316L Austenitic Stainless Steel

The law of low-cycle fatigue with hold time at elevated temperature is investigated in this paper. A new life prediction model for the situation of fatigue and creep interaction is developed, based on the damage due to fatigue and creep. In order to verify the prediction model, strain-controlled low-cycle fatigue tests at temperature 693K, 823K and 873K and fatigue tests with various hold time at temperature 823K and 873K for 316L austenitic stainless steel were carried out. Good agreement is found between the predictions and experimental results.

Life Prediction for Notched Components in Nonproportional Low Cycle Fatigue: Experiment and FEM Analysis

2004 ◽  
Author(s):  
Masao Sakane ◽  
Tsuneo Itoh ◽  
Tomoshige Susaki ◽  
Yoshiyasu Kawazoe
Keyword(s):  
Crack Initiation ◽  
Linear Models ◽  
Low Cycle Fatigue ◽  
Notch Root ◽  
Fem Analysis ◽  
Local Strain ◽  
304 Stainless Steel ◽  
Cycle Fatigue ◽  
Notched Specimens ◽  
Strain Paths

This paper studies the low cycle fatigue of circumferential notched specimens of type 304 stainless steel in nonproportional loading. Strain controlled tension-torsion low cycle fatigue tests were carried out using the notched specimens under 15 strain paths. Crack initiation lives detected by a d.c. potential method were discussed in relation to the strain concentration factors and strain histories. Finite element analyses were carried out for evaluating the local strain at the notch root using elastic-perfectly plastic and bi-linear models. The maximum principal strain and nonproportional strain ranges conservatively estimated the crack initiation lives of the notched specimens.

Detection of the Crack Initiation by Means of AE Method Under Low Cycle Fatigue of Elbow Pipe Having Local Wall Thinning

2010 ◽  
Author(s):  
Naoya Kasai ◽  
Kotoji Ando ◽  
Maki Nishio ◽  
Yoshio Urabe ◽  
Koji Takahashi
Keyword(s):  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Axial Strain ◽  
Wide Band ◽  
Fatigue Tests ◽  
Crack Growth Behavior ◽  
Cycle Fatigue ◽  
Accelerated Corrosion ◽  
Wall Thinning ◽  
Local Wall Thinning

This paper describes the detectability of the crack initiation by means of the AE method under low cycle fatigue of the elbow pipe having local wall thinning to clarify the crack growth behavior for the pipes. Elbow specimens having local wall thinning were prepared, and local wall thinning due to flow accelerated corrosion was simulated by machined pipe wall thinning. Low cycle fatigue tests for the specimens were then carried out. AE method during low cycle fatigue tests was conducted to evaluate the crack initiation and location. In AE measurement, wide band AE sensors of 5mm in diameter were used to attach to the convex surfaces of the specimens. The circumference and axial strain of the specimens and the cross head displacement were also stored to the digital AE system signal. As a result, it is clear that the AE signals indicated the crack initiation in small circumference strain.

Internal Crack Initiation in Low-Cycle Fatigue of Stainless Steel

2010 ◽  
Author(s):  
Masayuki Kamaya ◽  
Masahiro Kawakubo
Keyword(s):  
Stainless Steel ◽  
Crack Initiation ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Internal Crack ◽  
Surface Cracks ◽  
Cycle Fatigue ◽  
Type Specimens ◽  
316 Stainless Steel

Internal cracks were observed on the fracture surface of Type 316 stainless steel specimens subjected to a low-cycle fatigue test, in which the strain amplitude was more than 1%. In some cases the specimens fractured due to these internal cracks. In this study, the reason and conditions for the internal crack initiation were examined. Fatigue experiments were conducted using Type 316 stainless steel. In order to enhance the internal crack initiation, the specimens were subjected to pre-damaging and surface cracks were removed before the start of the fatigue tests. It was shown that specimens fractured due to internal cracks when the strain amplitude of pre-damaging was more than 1% and hourglass-type specimens were used. The fatigue life was reduced largely due to the internal cracks and the magnitude of reduction was more significant for the smaller strain amplitude of the fatigue tests. Inclusions were observed at the origin of some internal cracks. It was deduced that the hourglass geometry of the specimen enhanced the internal crack initiation. Namely, the multi-axial field was one of the factors promoting the internal crack initiation.

Fatigue resistance of Fe3Al-based alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Florian Gang ◽  
Manja Krüger ◽  
Alexandra Laskowsky ◽  
Heike Rühe ◽  
Joachim H. Schneibel ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Iron Aluminide ◽  
Cycle Fatigue ◽  
Grain Sizes ◽  
Cast Alloys

ABSTRACTThe low cycle fatigue (LCF) behaviour of two cast as well as two hot extruded Fe3Al-based iron aluminide alloys, either with or without Cr, is investigated. All four alloys contain microalloying additions of Zr, Nb, C and B. Fatigue tests were carried out under strain control for strain amplitudes in the range of εa = 0.1 – 0.4 % for the cast alloys and εa = 0.1 – 0.7 % for the extruded materials, at frequencies of 1 Hz (extruded Fe3Al) and 3 Hz (all other alloys) and at room temperature and 300 °C. Within the first cycles all alloys show strong cyclic hardening. Furthermore the fatigue strain – fatigue life curves are steeper at 300 °C than at room temperature, showing increased fatigue strength at low cycle numbers due to increasing ductility and decreased fatigue strength at increasing cycle numbers because of reduced yield strength. Cr is found to have only a negligible influence on the fatigue behaviour of Fe3Al-based alloys. Comparison between the differently processed materials shows superior LCF properties of the hot extruded iron aluminides due to significantly smaller grain sizes.

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