Fatigue Behavior of Ferritic-Pearlitic-Bainitic Steel – Effect of Positive Mean Stress

2009 ◽  
Vol 417-418 ◽  
pp. 577-580
Author(s):  
Jaroslav Polák ◽  
Martin Petrenec
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Strain Amplitude ◽  
Fatigue Behavior ◽  
Cyclic Creep ◽  
Plastic Strain Amplitude ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Bainitic Steel ◽  
The Mean

The fatigue properties of ferritic-pearlitic-bainitic steel using specimens produced from massive forging were measured in stress controlled regime with positive mean stress. The cyclic creep curves and cyclic hardening/softening curves were evaluated. The fatigue life was plotted in dependence on the mean stress and on the plastic strain amplitude. The principal contribution to the drop of the fatigue life with the mean stress is due to the increase of the plastic strain amplitude in cycling with mean stress.

Investigated on Fatigue Properties of Aluminum Ally 7050T7451 with Fastener Holes by Laser Shock Processing

2012 ◽  
Vol 460 ◽  
pp. 407-410
Author(s):  
Yin Fang Jiang ◽  
Xian Cong He ◽  
Yu Huang ◽  
Jian Wen Zhang ◽  
Zhi Fei Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Properties ◽  
Hole Drilling ◽  
Mean Stress ◽  
Strengthening Effect ◽  
Laser Shock ◽  
Residual Stress Field ◽  
Laser Shock Processing ◽  
The Mean ◽  
Shock Processing

Based on the FEM code ABAQUS and MSC.Fatigue, the process of LSP before hole-drilling was adopted to study the residual stress field of aluminum alloy7050T7451 with Fastener Holes after Laser shock processing (LSP), and the fatigue life of the specimens by LSP was analyzed in this paper. The results indicate that multiple laser shock processing can improve the residual compressive stress and fatigue life to a certain degree, and with the increasing number of shot, the strengthening effect gradually decreases. The ratio of the fatigue life of specimens treated by LSP to the fatigue life of untreated specimens is gradually decreased as the mean stress σm increases, and when the σm is 67.3MPa, the fatigue life of specimens treated by LSP advances 719%, compared with that of untreated specimens.

Cyclic Plasticity and Cyclic Creep in Austenitic-Ferritic Duplex Steel

2011 ◽  
Vol 465 ◽  
pp. 431-434
Author(s):  
Jaroslav Polák ◽  
Martin Petrenec ◽  
Jiří Man ◽  
Tomáš Kruml
Keyword(s):  
Creep Rate ◽  
Plastic Strain ◽  
Strain Amplitude ◽  
Cyclic Creep ◽  
Cyclic Stress ◽  
Plastic Strain Amplitude ◽  
Cyclic Plasticity ◽  
Stress Strain ◽  
Duplex Steel ◽  
Mean Stresses

Smooth specimens made from austenitic-ferritic duplex steel were subjected to constant stress amplitude loading with positive mean stresses. Hysteresis loops were recorded during the fatigue life and plastic strain amplitude and cyclic creep rate were determined. Fatigue hardening/softening curves, cyclic creep curves and cyclic stress-strain curves for different positive mean stresses were evaluated. Typical dislocation structures developed in both phases of the duplex steel were identified using TEM, compared with the saturated plastic strain amplitude and correlated with the decrease of the cyclic creep rate during cycling and the slope of the cyclic stress-strain curve.

scholarly journals Ratcheting-Fatigue Behavior of Harmonic-Structure-Designed SUS316L Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 477
Author(s):  
Yang Song ◽  
Zhe Zhang ◽  
Hantuo Ma ◽  
Masashi Nakatani ◽  
Mie Ota Kawabata ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Stainless Steels ◽  
Fatigue Behavior ◽  
Structure Design ◽  
Control Mode ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Strain Accumulation ◽  
Harmonic Structure ◽  
Ratcheting Strain

Stainless steels with harmonic-structure design have a great balance of high strength and high ductility. Therefore, it is imperative to investigate their fatigue properties for engineering applications. In the present work, the harmonic-structured SUS316L stainless steels were fabricated by mechanical milling (MM) and subsequent hot isostatic pressing (HIP) process. A series of ratcheting-fatigue tests were performed on the harmonic-structured SUS316L steels under stress-control mode at room temperature. Effects of grain structure and stress-loading conditions on ratcheting behavior and fatigue life were investigated. Results showed that grain size and applied mean stress had a significant influence on ratcheting-strain accumulation and fatigue life. Owing to the ultrafine grained structure, tensile strength of the harmonic-structured SUS316L steels could be enhanced, which restrained the ratcheting-strain accumulation, resulting in a prolonged fatigue life. A higher mean stress caused a faster ratcheting-strain accumulation, which led to the deterioration of fatigue life. Moreover, a modified model based on Smith–Watson–Topper (SWT) criterion predicted the ratcheting-fatigue life of the harmonic-structured SUS316L steels well. Most of the fatigue-life points were located in the 5 times error band.

Low Cycle Fatigue Behavior of N80Q Steel under the Influence of Mean Strains

2019 ◽  
Vol 944 ◽  
pp. 1067-1075
Author(s):  
Wen Lan Wei ◽  
Li Hong Han ◽  
Yao Rong Feng ◽  
Jian Xun Zhang ◽  
Hang Wang
Keyword(s):  
Electron Microscopy ◽  
Fatigue Life ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Thermal Recovery ◽  
Cycle Fatigue ◽  
Compression Load ◽  
The Mean ◽  
Mean Strain

The service conditions of thermal recovery wells make the casing repeatedly bear the tension and compression load and form low cycle fatigue. Meanwhile, many factors, such as pre-strain and creep, lead to the formation of asymmetrical low cycle fatigue (R≠-1), which is the low cycle fatigue behavior under the influence of mean strain. This work studied the effect of mean strain on low cycle fatigue behavior of N80Q steel. Different strain amplitude conditions were selected for low cycle fatigue test, which were 0.5%, 0.7%, 1.0%, 1.5% and 2.0% respectively. Then tests at mean strains of-0.8%, 0%, 0.5% and 1.0% were conducted under constant strain amplitude. And the microstructure and fracture surface of the material after the tests were characterized using scanning electron microscopy and transmission electron microscopy, respectively. The results show that the mean strain makes the fatigue life reduce significantly under the condition of constant strain amplitude, and is related to the amplitude of the mean strain. The value of the mean strain and the strain amplitude will ultimately affect the fatigue life. And the fatigue life is related to the maximum absolute value of strain and has a linear relationship in the double logarithmic coordinate system. The SEM results of fracture morphology show that the brittleness feature of the crack growth area with high mean strain decreases significantly. And the fracture cross-section observation shows that the crack propagation is transgranular propagation. The TEM results show that a large number of dislocations pile-up is formed at lath subgrain boundary.

scholarly journals Mean Stress Effect on the Fatigue Life of 304L Austenitic Steel in Air and PWR Environments Determined with Strain- and Load-Controlled Experiments

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 221 ◽  
Author(s):  
Philippe Spätig ◽  
Jean-Christophe Le Roux ◽  
Matthias Bruchhausen ◽  
Kevin Mottershead
Keyword(s):  
Fatigue Life ◽  
Austenitic Steel ◽  
Strain Amplitude ◽  
Synergistic Effects ◽  
Stress Effect ◽  
Mean Stress ◽  
Controlled Experiments ◽  
Pressurized Water ◽  
Mean Stress Effect ◽  
The Mean

The mean stress effect on the fatigue life of 304L austenitic steel was evaluated at 300 °C in air and pressurized water reactor (PWR) environments. Uniaxial tests were performed in strain-control and load-control modes, with zero mean stress and a positive mean stress of 50 MPa. A specific procedure was used for the strain-controlled experiments to maintain the strain amplitude and mean stress constant. The strain-controlled data indicate that the application of positive mean stress decreases the fatigue life for a given strain amplitude in air and PWR environments. The data also show that the life reduction is independent of the environments, suggesting that no synergistic effects between the mean stress and the LWR environment occur. The load-controlled experiments confirm that the application of positive mean stress increases fatigue due to cyclic hardening processes. This observation is much less pronounced in the PWR environment. All data were analyzed using the Smith–Watson–Topper (SWT) stress–strain function, which was shown to correlate well with all strain- and load-controlled data with and without mean stress in each environment. In the SWT–life curve representation, the life reduction in the PWR environment was found fully consistent with the NUREG-CR6909 predictions.

Cyclic Plastic Response and Fatigue Life of Materials

2007 ◽  
Vol 348-349 ◽  
pp. 113-116 ◽  
Author(s):  
Jaroslav Polák
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Crack Growth ◽  
Strain Amplitude ◽  
Decisive Role ◽  
Cyclic Stress ◽  
Plastic Strain Amplitude ◽  
Short Crack ◽  
Plastic Response ◽  
Cyclic Plastic

Recently the decisive role of plastic strain amplitude for the initiation and the growth rate of short cracks has been demonstrated. The plastic strain amplitude can be related to the rate of short crack growth and also to the fatigue life. Since the cyclic stress-strain response of a material determines the plastic strain amplitude it influences basically its fatigue life. The experiments in stress and plastic strain controlled loading and short crack growth are presented and used to demonstrate the importance of the cyclic plastic response for the evaluation of the fatigue life.

M206 Dependence of Low-cycle Fatigue Behavior on Plastic Strain Amplitude in ECAPed Ferritic Stainless Steel

2015 ◽  
Vol 2015.90 (0) ◽  
pp. 280
Author(s):  
Ryuji TOMITA ◽  
Yoshihisa KANEKO ◽  
Makoto UCHIDA ◽  
Muhammad RIFAI ◽  
Hiroyuki MIYAMOTO ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Ferritic Stainless Steel ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Plastic Strain Amplitude ◽  
Cycle Fatigue

scholarly journals Effects of Pore Size on Fatigue Deformation Mechanism of Open-Cell Copper Foam at Low Stress Amplitude

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1639 ◽  
Author(s):  
Jian Chen ◽  
Shuowei Dai ◽  
Cong Li ◽  
Wei Li ◽  
Yanjie Ren
Keyword(s):  
Fatigue Life ◽  
Pore Size ◽  
Strain Amplitude ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Optical Microscope ◽  
Fatigue Properties ◽  
Exponential Relationship ◽  
Open Cell ◽  
Copper Foam

Axial compression-compression fatigue experiments on open-cell copper foams with different pore size were investigated in this paper. The effects of the strain amplitude on the fatigue properties were studied and found that there is an exponential relationship between the fatigue life and strain amplitude. The experimental results indicate that a smaller pore size is related to a lower fatigue life. The microstructures of failed copper foam tested at low stress amplitude were observed by optical microscope and scanning electron microscopy (SEM), suggests that different pore size related to different fatigue behavior. The fatigue failure mechanism of the open-cell copper foams were compared by experimental research.

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

scholarly journals Fatigue Modeling and Numerical Analysis of Re-Filling Probe Hole of Friction Stir Spot Welded Joints in Aluminum Alloys

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2171
Author(s):  
Armin Yousefi ◽  
Ahmad Serjouei ◽  
Reza Hedayati ◽  
Mahdi Bodaghi
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Element Model ◽  
Plastic Strain Amplitude ◽  
Friction Stir ◽  
Probe Hole ◽  
Good Agreement

In the present study, the fatigue behavior and tensile strength of A6061-T4 aluminum alloy, joined by friction stir spot welding (FSSW), are numerically investigated. The 3D finite element model (FEM) is used to analyze the FSSW joint by means of Abaqus software. The tensile strength is determined for FSSW joints with both a probe hole and a refilled probe hole. In order to calculate the fatigue life of FSSW joints, the hysteresis loop is first determined, and then the plastic strain amplitude is calculated. Finally, by using the Coffin-Manson equation, fatigue life is predicted. The results were verified against available experimental data from other literature, and a good agreement was observed between the FEM results and experimental data. The results showed that the joint’s tensile strength without a probe hole (refilled hole) is higher than the joint with a probe hole. Therefore, re-filling the probe hole is an effective method for structures jointed by FSSW subjected to a static load. The fatigue strength of the joint with a re-filled probe hole was nearly the same as the structure with a probe hole at low applied loads. Additionally, at a high applied load, the fatigue strength of joints with a refilled probe hole was slightly lower than the joint with a probe hole.

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