Numerical and experimental investigation of low cycle fatigue behaviour in P91 steel

Zhang

2020

Metals

Fatigue damage, creep damage, and their interactions are the critical factors in degrading the integrity of most high-temperature engineering structures. A reliable creep-fatigue damage interaction diagram is a crucial issue for the design and assessment of high-temperature components used in power plants. In this paper, a new three-dimensional creep-fatigue-elasticity damage interaction diagram was constructed based on a developed life prediction model for both high-temperature fatigue and creep fatigue. The total tensile strain energy density concept is adopted as a damage parameter for life prediction by using the elastic strain energy density and mean stress concepts. The model was validated by a great deal of data such as P91 steel at 550 °C, Haynes 230 at 850 °C, Alloy 617 at 850 and 950 °C, and Inconel 625 at 815 °C. The estimation values have very high accuracy since nearly all the test data fell into the scatter band of 2.0.

Section: Data Collectionmentioning

confidence: 99%

A New 3D Creep-Fatigue-Elasticity Damage Interaction Diagram Based on the Total Tensile Strain Energy Density Model

Zhang

2020

Metals

“…LCF has two fundamental characteristics, including low cycle phenomenon and plastic deformation in each cycle, in which the materials have finite endurance for this type of load. There is a lot of interest in investigating the influences of cyclic loading on the mechanical properties of the material, especially steel [13][14][15][16][17][18][19][20]. Srinivasan et al [13] investigated the LCF behavior at several temperatures of 316L stainless steel.…”

Section: Introductionmentioning

confidence: 99%

“…Mannan and Valsan [15] then studied the thermomechanical fatigue, creep-fatigue, and low-cycle fatigue of 9Cr-1Mo steel at high temperatures. The results from their research indicated that base metal of 316L stainless steel showed better fatigue resistance compared with weld metal at a temperature of 773 K. Ye et al [18] applied the nondestructive indentation technique to estimate the mechanical properties in the 304L steel weld zone subjected to the LCF loading, while numerical and experimental investigation regarding the LCF behavior of P91 steel was conducted by Dundulis et al [19].…”

Section: Introductionmentioning

confidence: 99%

Characterization of strain amplitude-dependent behavior of hardness and indentation size effect of SS400 structural steel

Vinh

Anh

Thang

2020

STCE

In this paper, the continuous stiffness measurement (CSM) indentation is employed to investigate fatigue mechanical properties of structural steel under cyclic loading. For this purpose, several representative analytical approaches were introduced to estimate the basic mechanical properties including Young’s modulus and indentation hardness from the characteristics of the loading/unloading curves. Several experiments including CSM nanoindentation, low-cycle fatigue experiment for four strain amplitude levels, optical microscope (OM), and transmission electron microscopy (TEM) examinations were conducted to observe the variation characteristics of mechanical properties at the microscale and their micro-mechanisms. The microstructural evolution of the specimens deformed by the low-cycle fatigue was observed using the OM and TEM examinations. The standard nanoindentation experiments were then performed at different strain rate levels to characterize the influences of strain rate indentation on hardness of the material. The micro-mechanisms established based on the microstructural evolution and strain gradient plasticity theory were introduced to be responsible for the variation of indentation hardness under cyclic loading. Finally, the indentation size effect (ISE) phenomenon in SS400 structural steel was investigated and explained through the strain gradient plasticity theory regarding geometrically necessary dislocations underneath the indenter tip. The experimental results can be used for practical designs as well as for understanding the fatigue behavior of SS400 structural steel. Keywords: cyclic loading; fatigue; nanoindentation; indentation size effect; strain rate sensitivity; structural steel.

“…Actually, a considerable number of structural components' failure can be attributed to the LCF damage, especially for the steam rotors during start/stop stage and power transient period [11][12][13][14][15][16][17]. A series of parameters, including the temperature [18], the strain rate [19], the strain amplitude [20], etc., could influence the LCF behavior of the material.…”

Section: Introductionmentioning

confidence: 99%

Investigation on LCF Behavior of Welded Joint at Different Temperatures for Bainite Steel

Xiongfei

Cui

et al. 2019

Chin. J. Mech. Eng.

The current research of low cycle fatigue (LCF) is mainly focused on the components with uniform microstructure. Compared with these typical components, LCF behavior of welded components are more complex due to their great gradient microstructure, especially for different temperature. In this paper, LCF properties were conducted on the welded joint at different temperatures for bainite steel, and the failure mechanism was systematically discussed. Fatigue parameters derived from fitting curves indicated that welded joint had worse plastic deformation resistance and experienced more significantly strain hardening effect at 300 °C. The joint failed in the weld metal at room temperature, which attributed to the softening in weld metal combined with cyclic strain hardening effect in heataffected zone, which meant the joint was more sensitive with the hardness at this condition. When it came to 300 °C, more cracks appeared near to HAZ and the heterogeneous distributed surface inclusion was responsible for the fracture transition to HAZ adjacent to bainite steel rather than the softest zone in HAZ, reflecting the joint was more sensitive with the surface inclusion at 300 °C. This research could support the design on loading of welded component at different temperature, and further ensure the safe operation.