Dislocation Density Evolution in Low-Cycle Fatigue of Steels Using Dislocation-Based Crystal Plasticity

2022 ◽  
Vol 148 (2) ◽  
Author(s):  
Dongping Zhu ◽  
Wei Zhang ◽  
Zhixia Ding
Keyword(s):  
Dislocation Density ◽  
Crystal Plasticity ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Density Evolution

Effect of microstructural constituents and morphological characteristics on low cycle fatigue behaviour of inter-critically annealed 20MnMoNi55 steel

2021 ◽  
pp. 146442072110387
Author(s):  
Parichay Basu ◽  
Sanjib K Acharyya ◽  
Prasanta Sahoo
Keyword(s):  
Finite Element ◽  
Strain Amplitude ◽  
Crystal Plasticity ◽  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Stress Triaxiality ◽  
Morphological Characteristics ◽  
Strain Curve ◽  
Cycle Fatigue ◽  
Microstructural Parameters

The effect of varying microstructural parameters on the cyclic behaviour of dual-phase steels was studied on the basis of experimental and micromechanical finite-element simulated results. The initial bainitic morphology of as-received 20MnMoNi55 steel was transformed into ferrite and martensite through proper inter-critical heat treatment procedures. Strain-controlled low cycle fatigue tests were conducted at room temperature with different strain amplitudes at a specific strain rate of 10−3/s. The cyclic stress–strain curve, obtained through joining the peak stresses of hysteresis loops corresponding to different strain amplitude, shows an increase in strain hardening with an increase in volume fraction of martensite. Whereas the rate of cyclic softening, considering the decrease in stress amplitude with respect to elapsed cycles, increases with increasing strain amplitude. Inclusive of all affecting microstructural parameters, an original microstructure-based representative volume element associated with a crystal plasticity-based material model was adopted for conducting micromechanical finite-element simulation. In addition to several parameters associated with a crystal plasticity model, consideration of initial geometrically necessary dislocation density in constituent phases resulted in the accurate prediction of a hysteresis loop at low strain amplitude as compared with the experimental results. A variation of stress triaxiality built up in ferrite matrix with martensite fraction along with deformation inhomogeneity between ferrite and martensite was also observed through a strain partitioning phenomenon obtained from finite-element simulated results.

Microstructure Evolution during LCF of a 10%Cr Steel at Room Temperature

2016 ◽  
Vol 879 ◽  
pp. 1311-1316 ◽  
Author(s):  
Roman Mishnev ◽  
Nadezhda Dudova ◽  
Rustam Kaibyshev
Keyword(s):  
Cyclic Loading ◽  
Dislocation Density ◽  
Microstructure Evolution ◽  
Room Temperature ◽  
Strain Softening ◽  
Low Cycle Fatigue ◽  
Lattice Dislocation ◽  
Total Strain ◽  
Cycle Fatigue ◽  
Number Of Cycles

The influence of cyclic loading on microstructure and hardness of a 10%Cr steel with 3%Co and 0.008%B was examined at room temperature and total strain amplitudes of ±0.25% and ±0.6%. Low cycle fatigue (LCF) curves exhibit a stress peak after a few cycles. Hardening is attributed to an increase in dislocation density; no changes in lath size were observed. Then stress tends to decrease monotonically with number of cycles that is indicative for material softening. At εac =±0.25%, strain softening is attributed to decreasing dislocation density and lath coarsening under LCF, whereas at εac =±0.6%, the knitting reaction between dislocations comprising lath boundaries and trapped lattice dislocation leading to the transformation of lath boundaries to subboundaries is a reason for hardness decrease and strain-induced subgrain coarsening.

scholarly journals Microstructural Evolution along the NiCrMoV Steel Welded Joints Induced by Low-Cycle Fatigue Damage

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 811
Author(s):  
Shuo Weng ◽  
Yuhui Huang ◽  
Mingliang Zhu ◽  
Fuzhen Xuan
Keyword(s):  
Dislocation Density ◽  
Grain Boundaries ◽  
Strain Amplitude ◽  
Microstructural Evolution ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Nicrmov Steel

The degradation of mechanical properties of materials is essentially related to microstructural changes under service loadings, while the inhomogeneous degradation behaviors along welded joints are not well understood. In the present work, microstructural evolution under low-cycle fatigue in base metal (BM) and weld metal (WM) of NiCrMoV steel welded joints were investigated by miniature tensile tests and microstructural observations. Results showed that both the yield strength and ultimate tensile strength of the BM and WM decreased after low-cycle fatigue tests, which were attributed to the reduction of dislocation density and formation of low-energy structures. However, the microstructural evolution mechanisms in BM and WM under the same cyclic loadings were different, i.e., the decrease of dislocation density in BM was attributed to the dislocation pile-ups along the grain boundaries, dislocation tangles around the carbides at the lower strain amplitudes (±0.3% or ±0.5%). Additionally, when the strain amplitude was ±8%, the dislocation density was further decreased by the formation of subgrains in BM. For WM, the dislocation density decreased with the increase of strain amplitude, which was mainly caused by the dislocation pile-ups along the grain boundaries and the formation of subgrains.

Dislocation density and sub-grain size evolution of 2CrMoNiWV during low cycle fatigue at elevated temperatures

2012 ◽  
Vol 60 (6-7) ◽  
pp. 2485-2496 ◽  
Author(s):  
T. Mayer ◽  
L. Balogh ◽  
C. Solenthaler ◽  
E. Müller Gubler ◽  
S.R. Holdsworth
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Size Evolution
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