scholarly journals Influence of Hardened Surface on Low Cycle Fatigue Characteristics at Tension-compression and Bending

2015 ◽  
Vol 63 (5) ◽  
pp. 1549-1554
Author(s):  
Artüras Sabaliauskas ◽  
Sergėjus Rimovskis ◽  
Petr Dostál
Keyword(s):  
Plastic Strain ◽  
Low Cycle Fatigue ◽  
White Layer ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Pure Bending ◽  
Cycle Loading ◽  
Fatigue Characteristics ◽  
Tension Strength ◽  
Hardened Surface

This paper analyses electromechanical hardening of the steel parts surface, when in the contact area so called “white layer” is formed. The experiments were performed to show the influence of “white layer” on strength of the steel C45 specimens under low cycle loading. This paper analyses monotonic and low cycle tension compression and pure bending characteristics of specimens with electromechanically hardened surface. The Performed experiments showed that under monotonic tension strength characteristics (σpr, σ02, σu) are increasing and strain characteristics (eu, ψ) are decreasing. During cyclic stress limited tension compression at low loading levels both the width of plastic strain hysteresis loop and accumulated plastic strain are decreasing, therefore the lifetime is increasing. Under pure bending this tendencies persist, but in this case the lifetime at all loading levels is larger than the lifetime at tension compression.

High Temperature Low-Cycle Fatigue, Deformation Microstructure and Final Fracture Behavior of a Nickel-Base Superalloy

2008 ◽  
Vol 378-379 ◽  
pp. 249-270 ◽  
Author(s):  
Du Yi Ye ◽  
Jin Yang Zheng
Keyword(s):  
Plastic Strain ◽  
Crack Propagation ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Final Fracture ◽  
High Plastic Strain ◽  
Nickel Base ◽  
High Plastic

The low-cycle fatigue (LCF) properties of a nickel-base precipitation-strengthened superalloy (GH4145/SQ), obtained at a temperature of 538 o C, were reported and discussed in this paper. The properties investigated include cyclic stress response, fatigue life, deformation microstructure and final fracture features as a function of applied strain amplitude. It was shown that the alloy exhibited a pronounced initial hardening followed by continuous softening to failure at high plastic strain amplitudes ( > 0.2% ap ε ), while at low plastic strain amplitudes ( < 0.2% ap ε ) the initial hardening was followed by a well-defined saturation stage. Bilinear behavior with a change of slope at a plastic strain amplitude of about 0.2% was observed in the cyclic stress-strain (CSS) and Coffin-Manson (C-M) plots. TEM observations revealed that slip band density increased with increasing total strain amplitude and precipitate degradation resulting from dislocation-precipitate interactions took place with continuous cyclic straining. The change in the microstructure during cycling is thus responsible for the fatigue hardening / softening behavior of the alloy. SEM examinations indicated that at low plastic strain amplitudes ( < 0.2% ap ε ) crack propagation was basically transgranular, while at high plastic strain amplitudes ( > 0.2% ap ε ) crack propagation exhibited intergranular features, as a whole. The variation in both the number of operating slip systems and the fracture modes with the strain amplitude employed was used to explain the observed two-stage LCF behavior of the present investigated superalloy.

Low Cycle Fatigue Behavior of Q345b Steel under Uniaxial Cycle Loading

2014 ◽  
Vol 904 ◽  
pp. 95-98
Author(s):  
Xiang You ◽  
Rui Dong Wang ◽  
Shi Ming Cui ◽  
Yong Jie Liu ◽  
Qing Yuan Wang
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Strain Range ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Cycle Loading ◽  
Reversed Cyclic ◽  
Q345b Steel

In this paper, the low cycle fatigue (LCF) behavior of Q345b steel was experimentally investigated in fully reversed cyclic axial configurations at room temperature. The strain range of 0.3%, 0.4%, 0.5%, 0.6% and 0.7% at constant strain rate of 0.005 s-1 was adopted. Cyclic stress-strain curve and strain life relationship were analyzed according to the Ramberg-Osgood relationship and Coffin-Manson relationship respectively. Suitable parameters were obtained showing good agreements with the experimental fatigue data.

ANISOTROPY OF LOW CYCLE FATIGUE CHARACTERISTICS OF SINGLE-CRYSTAL HEAT-RESISTANT NICKEL ALLOYS

2020 ◽  
pp. 97-105
Author(s):  
I.A. Hodinev ◽  
◽  
S.A. Monin ◽  
Keyword(s):  
Single Crystal ◽  
Nickel Alloys ◽  
Endurance Limit ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Heat Resistant ◽  
Cycle Loading ◽  
Two Temperatures ◽  
Fatigue Characteristics ◽  
Complete Deformation

The low cycle fatigue of heat-resistant nickel alloys with a single crystal structure VZHM7 and VIN3 was studied. The tests were carried out under conditions of monitoring the complete deformation in the cycle, loading of the type «tension-compression» occurred according to a sinusoidal law with a frequency of 0,5 Hz. For both alloys, tests were carried out for three crystallographic orientations ([001], [011], [111]) at two temperatures: 500 and 850 °C. Regression lines were constructed, the limits of limited endurance were found on the basis of 104 cycles. The influence of test temperature and crystallographic orientation on the endurance limit of alloys and RMS is analyzed.

Low-Cycle Fatigue Life of Continuously Cyclic-Hardening Material

2020 ◽  
Author(s):  
Zhong Zhang ◽  
Xijia Wu
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Root Mean Square ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Mean Square ◽  
Cycle Fatigue ◽  
Fatigue Crack Nucleation ◽  
Hardening Material ◽  
Plastic Strain Range

Abstract A general fatigue life equation is derived by modifying the Tanaka-Mura-Wu dislocation pile-up model for variable strain-amplitude fatigue processes, where the fatigue crack nucleation life is expressed in terms of the root mean square of plastic strain range. Low-cycle fatigue tests were conducted on an austenitic stainless steel. at 400°C and 600°C, the material exhibits continuously cyclic-hardening behaviour. The root mean square of plastic strain ranges is evaluated from the experimental data for each test condition at strain rates ranging from 0.0002/s to 0.02/s. The variable-amplitude Tanaka-Mura-Wu model is found to be in good agreement with the LCF data, which effectively proves Miner’s rule on the stored plastic strain energy basis.

Damage in Adhesive Joints During Low Cycle Fatigue

2010 ◽  
Author(s):  
Iva´n C. Ca´bulo-Pe´rez ◽  
Juan P. Casas-Rodri´guez
Keyword(s):  
Plastic Strain ◽  
Low Cycle Fatigue ◽  
Stress Test ◽  
Damage Model ◽  
Fatigue Tests ◽  
Constant Stress ◽  
Cycle Fatigue ◽  
Damage Behavior ◽  
Non Linear ◽  
Compressive Loads

The objective of this research is to study the damage behavior of bulk adhesive and single lap joint (SLJ) specimens during low cycle fatigue (LCF). Fatigue tests under constant stress amplitude were done and strain response was measured through cycles to failure using the bulk adhesive and SLJ data. A non linear damage model was used to fit experimental results. Identification of the damage parameters for bulk adhesive was obtained from the damage against accumulated plastic strain plot. It is shown that the plastic strain can be obtained from the constant stress test if the instantaneous elastic modulus, i.e. modulus affected by damage, is evaluated for each cycle. On the other hand, damage in SLJ was seen mainly in the adhesive for itself — no substrate failure — this fact is used to propose that fatigue response in the joint is due to continuum damage accumulation in the adhesive as the number of cycles increases. Damage behavior under compressive loads was not taken into account but good correlation of numerical and experimental data was obtained. It was found that damage evolution behaves in a non linear manner as the plastic deformation grows for each cycle: on fatigue onset an accelerated damage grow is observed, then a proportional evolution, and finally a rapid failure occurs; this characteristics were seen in both the SLJ and bulk adhesive specimen. So far, this research takes the damage model found in a standard adhesive specimen and assumes it is accurate enough to represent the damage behavior of the SLJ configuration.

Low-Cycle Strength of Elements of Constructions

2018 ◽  
Author(s):  
Alexander Zvorykin ◽  
Roman Popov ◽  
Mykola Bobyr ◽  
Igor Pioro
Keyword(s):  
Stress State ◽  
Plane Stress ◽  
Low Cycle Fatigue ◽  
Plane Stress State ◽  
Structural Elements ◽  
Cycle Fatigue ◽  
Kinematic Equation ◽  
Effective Coefficients ◽  
Operational Life ◽  
Cycle Loading

Analysis of engineering approach to the operational life forecasting for constructional elements with respect to the low-cycle fatigue is carried out. Applicability limits for a hypothesis on existence of generalized cyclic-deforming diagram in case of complex low-cycle loading (deforming) are shown. It is determined, that under condition of plane-stress state and piecewise-broken trajectories of cycle loading with stresses and deformation checking the cyclic deforming diagram is united in limits of deformations, which are not exceeded 10 values of deformation corresponding material yield point. Generalized kinematic equation of material damageability is described. The method of damageability parameter utilization for increasing of accuracy calculation of structural elements low-cycle fatigue by using the effective coefficients of stresses and deformations taking into account the damageability parameter is given.

scholarly journals Impact of Temperature on Low-Cycle Fatigue Characteristics of the HR6W Alloy

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6741
Author(s):  
Grzegorz Junak ◽  
Anżelina Marek ◽  
Michał Paduchowicz
Keyword(s):  
Fatigue Life ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Fatigue Characteristics

This paper presents the results of tests conducted on the HR6W (23Cr-45Ni-6W-Nb-Ti-B) alloy under low-cycle fatigue at room temperature and at 650 °C. Fatigue tests were carried out at constant values of the total strain ranges. The alloy under low-cycle fatigue showed cyclic strengthening both at room temperature and at 650 °C. The degree of HR6W strengthening described by coefficient n’ was higher at higher temperatures. At the same time, its fatigue life Nf at room temperature was, depending on the range of total strain adopted in the tests, several times higher than observed at 650 °C.

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