AFM Study of Microstructure Role in the Cyclic Plasticity of Martensitic Steel

2016 ◽  
Vol 258 ◽  
pp. 444-447
Author(s):  
Gulzar Seidametova ◽  
Jean Bernard Vogt ◽  
Ingrid Proriol Serre
Keyword(s):  
Surface Relief ◽  
Prior Austenite ◽  
Martensitic Steel ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Cyclic Plasticity ◽  
Cycle Fatigue ◽  
Fatigue Cycle ◽  
Total Strain Range ◽  
Austenite Grains

The paper presents the description of FSMs (fatigue slip markings) and the evaluation of cyclic plasticity markings of a 12%Cr martensitic steel by AFM surface analyses. The microstructure of a 12%Cr martensitic steel, quenched and tempered in air, consists of prior austenite grains, packets, blocks, and laths. The low cycle fatigue (LCF) test at a total strain range Δεt=1.2% was interrupted at different life fractions for the surface relief investigation by AFM. The localization of FSMs relatively to the different microstructural interfaces of the studied steel was proposed. The principal FSMs, appeared in the first fatigue cycle, are likely to be localized at the packet and block boundaries, while the secondary one (appeared later at 44% of lifetime) are at the lath boundaries or in the laths. The height of principal and secondary FSMs increases constantly during LCF cycling.

Low-Cycle Fatigue under Biaxial Stress

1974 ◽  
Vol 188 (1) ◽  
pp. 657-671 ◽  
Author(s):  
M. W. Parsons ◽  
K. J. Pascoe
Keyword(s):  
Austenitic Steel ◽  
Abrupt Change ◽  
Low Cycle Fatigue ◽  
Axial Loading ◽  
Strain Range ◽  
Fatigue Behaviour ◽  
Biaxial Stress ◽  
Cycle Fatigue ◽  
Biaxial Strain ◽  
Total Strain Range

The low-cycle fatigue behaviour of a ferritic and an austenitic steel have been studied under various conditions of reversed biaxial strain. These cyclically softened and hardened respectively. In all cases, relationships of the form were found between total strain range Δε t and life Nf for lives in the range 102−105 cycles, with an abrupt change of β at intermediate lives. Variation of state of strain affected both β and κ. Various theories for the correlation of fatigue behaviour under multi-axial loading have been reviewed and compared with these results. None was found to account adequately for the effect of straining régime with the materials tested.

Low Cycle Fatigue Characteristics of a Low-Thermal Expansion, High Strength Alloy (HAYNES 242 Alloy)

2011 ◽  
Author(s):  
L. M. Pike ◽  
S. K. Srivastava
Keyword(s):  
Thermal Expansion ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
High Strength ◽  
Wave Form ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Low Thermal Expansion ◽  
Long Range Ordering

HAYNES® 242® alloy, based primarily on the Ni-25Mo-8Cr system, derives its low thermal expansion characteristics from its composition and its high strength concomitant with high ductility from a long-range ordering reaction upon an aging heat treatment. This combination has enabled the alloy continually to find a challenging range of applications in the aerospace industry at up to 1300°F (704°C). These include seal rings, containment rings, duct segments, casings, rocket nozzles, etc. In conjunction with the creep strength and environmental resistance, the low cycle fatigue (LCF) behavior is an important material property affecting the service life of 242 alloy components. The low cycle fatigue behavior of 242 alloy was studied under fully reversed strain-controlled mode at 800°F (427°C), 1000°F (538°C), 1200°F (649°C) and 1400°F (760°C) using a triangular wave form with a frequency of 0.33 Hz. Results are presented in terms of cycles to crack initiation and failure. The magnitudes of fatigue lives at total strain range ≤ 0.7% at 800, 1000 and 1200°F are significantly greater than those of solid solution strengthened alloys. Additionally, stress-controlled LCF tests were performed at 1200°F (649°C) on 242 alloy as well as 909 alloy (for comparison). The paper will discuss the results of these two test programs.

Effect of Creep in Low-Cycle Fatigue of Pressure Vessel Steel

1970 ◽  
Vol 92 (1) ◽  
pp. 67-73 ◽  
Author(s):  
J. Dubuc ◽  
A. Biron
Keyword(s):  
Pressure Vessel ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Fatigue Tests ◽  
Pressure Vessel Steel ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Vessel Steel ◽  
The Mean ◽  
Mean Strain

Low-cycle fatigue tests have been carried out at 2 cpm on a pressure vessel steel at 350 deg C (662 deg F). The total strain range was fixed for each test and the minimum (or mean) strain in some cases was constant (zero minimum value), in others increased uniformly in time at a predetermined rate. It was found that variations in the mean strain up to 0.5 percent/hour had no significant influence on the results.

SEM Study of the Influence of Microstructure on Low Cycle Fatigue Crack Growth in Martensitic Steel I

2018 ◽  
Vol 774 ◽  
pp. 96-100 ◽  
Author(s):  
Tamaz Eterashvili ◽  
Temur Dzigrashvili ◽  
M. Vardosanidze
Keyword(s):  
Room Temperature ◽  
Martensitic Steel ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Cycle Fatigue ◽  
Slip Bands ◽  
Sem Study ◽  
Austenite Grains ◽  
Plastic Zones ◽  
The Impact

Distribution of fatigue cracks in chromium martensitic steel after low cycle fatigue (LCF) tests at room temperature has been studied using SEM, and the experimental evidences of localized plastic flow (LPF) are presented. The influence of the location of LPF and the microstructure elements on the trajectory and growth of microcracks is also considered. The dimensions of plastic zones ahead of macrocrack tip as well as at its edges were measured in the process of crack propagation inside of the sample. The processes occurring in plastic zone, particularly ahead of macrocrack tip, were analyzed. Distribution, orientation and the reasons of slip bands’ formation as well as the microstructure elements at which they were nucleated have been studied. The impact of the slip bands’ orientation on the process of macrocrack growth was also analyzed. In addition the interactions of a crack with the boundaries of former austenite grains, martensitic packets, martensitic laths, slip bands and precipitates have been discussed.

Notch Effect in Low-Cycle Fatigue at Elevated Temperatures—Life Prediction From Crack Initiation and Propagation Considerations

1986 ◽  
Vol 108 (4) ◽  
pp. 279-284 ◽  
Author(s):  
Masao Sakane ◽  
Masateru Ohnami
Keyword(s):  
Crack Initiation ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Notch Effect ◽  
Cycle Fatigue ◽  
Crack Initiation And Propagation ◽  
Total Strain Range ◽  
Notched Specimens ◽  
Initiation And Propagation

This paper describes the notch effect in low-cycle fatigue of an austenitic stainless steel SUS 304 at 873 K in air. Total strain range-controlled tests were carried out using a round unnotched and three round notched specimens. A prediction method for low-cycle fatigue lives of notched specimens was developed by predicting the crack initiation and propagation periods separately. To predict the former Neuber’s rule was applied and a nominal stress/strain criterion was developed to predict the latter. Failure lives, obtained by adding the two prediction lives, closely agree with observed failure lives.

Low Cycle Fatigue of Alloy 617 at 850 °C and 950 °C

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
J. K. Wright ◽  
L. J. Carroll ◽  
J. A. Simpson ◽  
R. N. Wright
Keyword(s):  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Solute Drag ◽  
Cycle Fatigue ◽  
Alloy 617 ◽  
Total Strain Range ◽  
Cycles To Failure

The low cycle fatigue behavior of Alloy 617 has been evaluated at 850 °C and 950 °C, the temperature range of particular interest for the intermediate heat exchanger on a proposed high-temperature gas-cooled nuclear reactor. Cycles to failure were measured as a function of total strain range and varying strain rate. Results of the current experiments compare well with previous work reported in the literature for a similar range of temperatures and strain rate. The combined data demonstrate a Coffin–Manson relationship, although the slope of the Coffin–Manson fit is close to −1 rather than the typically reported value of −0.5. At 850 °C and a strain rate of 10−3 /s Alloy 617 deforms by a plastic flow mechanism in low cycle fatigue and exhibits some cyclic hardening. At 950 °C for strain rates of 10−3–10−5 /s, Alloy 617 deforms by a solute drag creep mechanism during low cycle fatigue and does not show significant cyclic hardening or softening. At this temperature the strain rate has little influence on the cycles to failure for the strain ranges tested.

Low Cycle Fatigue Life Evaluation According to Temperature and Orientation in Nickel-Base Superalloy

2019 ◽  
Vol 814 ◽  
pp. 121-126
Author(s):  
In Kang Heo ◽  
Dong Hyun Yoon ◽  
Jae Hoon Kim
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Total Strain ◽  
Nickel Base Superalloy ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Materials Used ◽  
Nickel Base

Components of gas turbines must be extremely resistant to high temperatures, high stresses, high-temperature corrosion, and erosive environments. The materials used in these environmental conditions are mainly nickel-based superalloys. In this study, the low-cycle fatigue of the nickel-based superalloy Inconel 792 was examined. The total strain range of a gas turbine between 760 °C and 870 °C was considered as the parameter representing the actual gas turbine operation. In addition, tests were performed using a trapezoidal waveform of the total strain to reflect the operation-stop conditions of a gas turbine with frequent shutdowns. The results of the fatigue test were compared with the Coffin–Manson method and energy method. The fractured surface was analyzed using a scanning electron microscope (SEM).

Investigation on Low Cycle Fatigue Life of SC Notched Specimens

2010 ◽  
Vol 97-101 ◽  
pp. 449-452
Author(s):  
Ping Zhao ◽  
Qing Hua He ◽  
Wei Li
Keyword(s):  
Fatigue Life ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Notched Specimens ◽  
Orientation Function ◽  
Fatigue Notch Factor

A low cycle fatigue life (LCF) prediction model for nickel-based single crystal (SC) is presented based on the LCF experiments of notched specimens. Fatigue notch factor is adopted to reflect the influence of notch shape on LCF. Orientation function is adopted to modify total strain range and eliminate the influence of orientation on LCF. Cycle stress ratio is adopted to reflect the influence of mean stress and cycle character on LCF. The predicted results shows that all the data are in the factor of 2.1 scatter band, which means that the model proposed in this work is reasonable.

Low-Cycle Fatigue Behavior of Internally Pressurized Boxes

1967 ◽  
Vol 89 (3) ◽  
pp. 427-435 ◽  
Author(s):  
M. R. Gross ◽  
R. E. Heise
Keyword(s):  
Aluminum Alloy ◽  
Yield Strength ◽  
Thick Plate ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Complex Structures ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Structural Applications

One phase of a continuing study of the low-cycle fatigue behavior of metals for deep submergence structural applications involves the validity of simple specimen results when applied to complex structures. As a part of this study, the low-cycle fatigue performance of twelve internally pressurized boxes was investigated. The boxes were constructed from 1-in-thick plate of six materials consisting of three steels, one aluminum alloy, and two titanium alloys. The boxes were cyclically pressurized at peak nominal stresses up to about 80 percent of the yield strength of the base metal. The results are compared with data previously obtained for simple laboratory specimens. The results of the box tests tend to confirm two general conclusions reached previously from simple specimen tests, that is: (1) Increases in low-cycle fatigue strength for a given life are not commensurate with increases in yield strength, and (2) low-cycle fatigue life is closely related to total strain range and appears to be independent of both structural metal and strength level in the life range of 1000 to 30,000 cycles.

HIGH TEMPERATURE LOW CYCLE FATIGUE AND FRACTURE CHARACTERISTIC IN TWO SINGLE CRYSTAL SUPERALLOYS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2892-2897
Author(s):  
J. J. YU ◽  
Z. H. WANG ◽  
X. F. SUN ◽  
T. JIN ◽  
H. R. GUAN ◽  
...  
Keyword(s):  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Fatigue Tests ◽  
Total Strain ◽  
Stress Axis ◽  
Cycle Fatigue ◽  
Total Strain Range ◽  
Refractory Elements ◽  
Fatigue And Fracture

Total strain controlled low cycle fatigue tests were conducted at 1173K for DD32 and SRR99 alloys. With the increase of total strain range, the stress amplitude of DD32 alloy improved more fleetly than that of SRR99 alloy. At total strain ranges less than or equal to 1.0%, the low cycle fatigue life of DD32 alloy was greater than that of SRR99 alloy. It was shown that the higher content of refractory elements in DD32 alloy resulted in a remarkable improvement of LCF properties compared to SRR99 alloy. The crack propagation perpendicular to the stress axis occurred in transgranular mode in both alloys. DD32 alloy presented more ductile character than SRR99 alloy.

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