86 results on '"Xian-Cheng Zhang"'
Search Results
2. High‐temperature creep‐fatigue‐oxidation behaviors of P92 steel: Evaluation of life prediction models
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Kang‐Kang Wang, Jian‐Feng Wen, Xian‐Xi Xia, Run‐Zi Wang, Guo‐Dong Zhang, Xian‐Cheng Zhang, and Shan‐Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2022
3. Establishment of unified creep–fatigue life prediction under various temperatures and investigation of failure physical mechanism for Type 304 stainless steel
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Le Xu, Run‐Zi Wang, Lei He, Xian‐Cheng Zhang, Shan‐Tung Tu, Hideo Miura, and Takamoto Itoh
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2022
4. Active and passive compliant force control of ultrasonic surface rolling process on a curved surface
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Xian-Cheng Zhang, Yi-Xin Liu, Shuang Liu, Zhang Kaiming, and Ji Wang
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Surface (mathematics) ,Materials science ,Universal Software Radio Peripheral ,Mechanical Engineering ,Acoustics ,Process (computing) ,Aerospace Engineering ,PID controller ,Ultrasonic sensor ,Static force ,Deformation (meteorology) - Abstract
Ultrasonic surface rolling process (USRP) is one of the effective mechanical surface enhancement techniques. During the USRP, unstable static force will easily do harm to the surface quality. In order to achieve a higher surface quality on the part with a curved surface, an active and passive compliant USRP system has been developed. The compliant USRP tool can produce the natural obedience deformation along the part surface. Force control based on the fuzzy Proportional-integral-derivative (PID) method is then designed to maintain the static force during the USRP. Experiments have been performed on a real aero-engine blade with curved surface. It is proved that the deigned active and passive compliant USRP system can significantly reduce the force variation from 42.2 N to 4.2 N, and achieve a uniform surface quality after processing.
- Published
- 2022
5. A quasi-in-situ EBSD study of the thermal stability and grain growth mechanisms of CoCrNi medium entropy alloy with gradient-nanograined structure
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Shan-Tung Tu, Peng Cheng Zhao, Xiao Li, Run-Zi Wang, Yonggang Tong, Xian Cheng Zhang, and Bo Guan
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Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,Nucleation ,Grain growth ,Mechanics of Materials ,Materials Chemistry ,Ceramics and Composites ,Dynamic recrystallization ,Grain boundary ,Thermal stability ,Surface layer ,Composite material ,Electron backscatter diffraction - Abstract
The thermal stability and mechanical properties of a gradient-nanograined structure (GNS) CoCrNi medium entropy alloy (MEA) processed by ultrasonic surface rolling were studied by using isothermal/isochronal annealing tests combined with quasi-in-situ electron backscatter diffraction (EBSD) characterization and Vickers micro-hardness (HV) measurements. A layer by layer high-throughput investigation method was used to quantitatively study the grain growth kinetics and grain boundary evolution with different initial grain sizes, which could effectively save specimen and time costs. The grain nucleation and growth, as well as shrink and disappearance process through Σ3 coincidence site lattice boundary migration with slightly lattice rotation during annealing were directly revealed. The layer by layer grain growth kinetics and calculated activation energy indicate that the thermal stability of nano-grained top surface layer is relatively higher than that of nano-twined subsurface layer for the gradient CoCrNi MEA processed by ultrasonic surface rolling. Further analysis show that the grain boundary relaxation and dynamic recrystallization of the topmost nano-grains led to the decrease of grain boundary energy, thus improving their thermal stability. The present work provided theoretical basis for the application of CoCrNi MEA at high temperatures. Moreover, the high-throughput method on the investigation of grain stability by using gradient structure can be easily extended to other materials and it is of great significance for understanding the microstructural evolution of gradient materials.
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- 2022
6. Effect of ultrasonic surface deep rolling combined with oxygen boost diffusion treatment on fatigue properties of pure titanium
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Cong-Yang Gong, Cheng-Cheng Zhang, Xian-Cheng Zhang, Xue-Fei Teng, Yun-Fei Jia, and Shan-Tung Tu
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Multidisciplinary ,Materials science ,Diffusion ,Science ,chemistry.chemical_element ,Microstructure ,Structural materials ,Indentation hardness ,Oxygen ,Article ,Mechanical engineering ,Brittleness ,chemistry ,Residual stress ,Medicine ,Deformation (engineering) ,Composite material ,Titanium - Abstract
Ultrasonic surface deep rolling (USDR), oxygen boost diffusion (OBD), and their combination (USDR-OBD) were all used to improve the surface hardening of pure titanium. The microstructure, microhardness, and fatigue life of pure titanium treated by USDR, OBD, and USDR-OBD methods were analyzed. USDR treatment induced a severe deformation area, while OBD treatment produced a brittle oxygen diffusion zone. The USDR-OBD treated samples approached the highest hardness in comparison with other treated samples. The fatigue lives of USDR treated samples were improved, which was due to the high compressive residual stress and refined grains. However, the fatigue lives of both OBD treated samples and USDR-OBD treated samples were decreased due to premature crack initiation and rapid propagation in the oxygen diffusion zone. Finally, the fatigue fracture mechanisms of different samples were proposed.
- Published
- 2021
7. Grain-refining and strengthening mechanisms of bulk ultrafine grained CP-Ti processed by L-ECAP and MDF
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Peng-Cheng Zhao, Bo Guan, Xian-Cheng Zhang, Guang-Jian Yuan, Run-Zi Wang, Shan-Tung Tu, and Yun-Fei Jia
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Materials science ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,Recrystallization (metallurgy) ,02 engineering and technology ,Strain hardening exponent ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,0104 chemical sciences ,Mechanics of Materials ,Ultimate tensile strength ,Materials Chemistry ,Ceramics and Composites ,Dynamic recrystallization ,Composite material ,Dislocation ,0210 nano-technology ,Strengthening mechanisms of materials ,Electron backscatter diffraction - Abstract
The microstructural evolution and mechanical properties of ultrafine-grained (UFG) CP-Ti after an innovative large-volume equal channel angular pressing (L-ECAP) and multi-directional forging (MDF) were systematically examined using monotonic tensile tests combined with transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) techniques. Substantially refined and homogeneous microstructures were achieved after L-ECAP (8-pass and 12-pass) and MDF (2-cycle and 3-cycle), respectively, where the grain size distribution conformed to lognormal distribution. The grain refinement of 450 °C L-ECAP is dominated by dynamic recrystallization (DRX) and dynamic recovery (DRV), while that of MDF is dominated by DRX. The iron impurities promote recrystallization by pinning-induced dislocation accumulation so that DRX is prone to occur at iron segregation regions during L-ECAP. The monotonic tensile results show that the strain hardening rate of CP-Ti increases with the decrease of grain size, while the continuous strain hardening ability decreases. The relationship between the average grain size and yield strength is in accordance with Hall-Petch relationship. Meanwhile, the individual strengthening mechanisms were quantitatively examined by the modified model. The results indicate that the strengthening contribution of dislocation accumulation to yield strength is greater than that of grain refinement.
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- 2021
8. Investigation of creep-fatigue crack initiation by using an optimal dual-scale modelling approach
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Kai-Shang Li, Run-Zi Wang, Ji Wang, Le Xu, Li-Qiang Liu, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
9. Probabilistic damage tolerance assessment method based on the multi-scale crack growth model
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Rong-Sheng Lu, Jie Yang, Ji Wang, Run-Zi Wang, Valery Shlyannikov, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2023
10. Creep-fatigue damage mechanisms and life prediction based on crystal plasticity combined with grain boundary cavity model in a nickel-based superalloy at 650°C
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Kai-Shang Li, Run-Zi Wang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2023
11. Microscopic fatigue crack propagation model for polycrystalline alloys
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Hao-han Guo, Rong-sheng Lu, Fang Liu, Wei Cui, Jun Shen, Jie Yang, and Xian-cheng Zhang
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
12. Process-performance-prediction integration for fatigue life improvement technologies: An implementation in cold expansion of hole structures
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Kai-Shang Li, Run-Zi Wang, Xian-Cheng Zhang, Shu-Lei Yao, Lv-Yi Cheng, Xue-Lin Lei, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
13. A unified rule for high-cycle and low-cycle fatigue life prediction in multi-scale framework
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Kai-Shang Li, Lin-Hao Gu, Xiu-Rui Wang, Ji Wang, Run-Zi Wang, Hang-Hang Gu, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
14. Creep-fatigue reliability assessment for high-temperature components fusing on-line monitoring data and physics-of-failure by engineering damage mechanics approach
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Hang-Hang Gu, Run-Zi Wang, Min-Jin Tang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
15. A novel hole cold-expansion method and its effect on surface integrity of nickel-based superalloy
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Shuang Liu, Shan-Tung Tu, Xian-Cheng Zhang, Run-Zi Wang, Xue-Lin Lei, Ping Zhang, and Xian Cao
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Materials science ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,02 engineering and technology ,Conical surface ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Superalloy ,Mandrel ,Mechanics of Materials ,Residual stress ,Materials Chemistry ,Ceramics and Composites ,Surface roughness ,Dislocation ,Composite material ,0210 nano-technology ,Surface integrity - Abstract
Preferred surface integrity around the hole wall is one of the key parameters to ensure the optimized performance of hole components for nickel-based superalloy. The novel hole cold expansion technique introduced in this work involves the laser texturing process (LTP) followed by the Hertz contact rotary expansion process (HCREP), where the cylindrical sleeve is the critical component connecting the above-mentioned two processes. The purpose of LTP is to obtain the most optimized strengthened cylindrical sleeve surface, preparing for the following HCREP. Hereafter, the HCREP acts on the nickel-based hole components by the rotary extruding movements of the strengthened sleeve and conical mandrel tools. As compared to the as-received GH4169 material, the surface integrity characterization for the strengthened hole shows that a plastic deformation layer with finer grains, higher micro-hardness, deeper compressive residual stress (CRS) distribution and lower surface roughness is formed at the hole wall. In addition, transmission electron microscope (TEM) observations reveal the microstructure evolution mechanism in the strengthened hole. Grain refinement near the hole wall is regarded as the fundamental reason for improving the surface integrity, where the aggregated dislocations and recombined dislocation walls can be clearly observed.
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- 2020
16. Machinability and cutting force modeling of 7055 aluminum alloy with wide temperature range based on dry cutting
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Ping Zhang, Xian Cao, Xian-Cheng Zhang, and Youqiang Wang
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0209 industrial biotechnology ,Materials science ,Mechanical Engineering ,Machinability ,Alloy ,chemistry.chemical_element ,02 engineering and technology ,Work hardening ,engineering.material ,Atmospheric temperature range ,Industrial and Manufacturing Engineering ,Computer Science Applications ,020901 industrial engineering & automation ,Machined surface ,chemistry ,Control and Systems Engineering ,Aluminium ,Cutting force ,Hardening (metallurgy) ,engineering ,Composite material ,Software - Abstract
The machinability of 7055 aluminum alloy with wide temperature range is examined, with focus on the three cutting forces, surface quality and work hardening of the material under low, medium, and high temperatures. The results demonstrate that, under low temperature, the work hardening depth of 7055 aluminum alloy is almost insensitive to the cutting speed, whereas at a higher cutting speed, the work hardening degree of the material first decreases and then increases; both the work hardening degree and hardening depth are significantly positively correlative to the cutting depth: the work hardening degree is positively correlative, though not so significantly, to the feed rate, while the work hardening depth is insensitive to the feed rate and remains at 100 μm in all cases. Under high temperature, the work hardening degree of 7055 aluminum alloy is positively correlative to the cutting speed; at depths smaller than 80 μm below the machined surface, the work hardening degree is negatively correlative to the cutting depth; at depths larger than 80 μm below the cutting surface, the work hardening degree of the material becomes significantly positively correlative to the cutting depth. A mathematical model of three cutting forces in dry cutting with wide temperature range is established based on wide temperature-range dynamic impact experimental results and the orthogonal cutting model, and modified using the LMSE (least mean square error) principle. The errors between the predicted and experimental three cutting forces, after modification, are all smaller than 10%, which is within the permissible limit of error. This verifies that the modified three cutting force prediction model can predict cutting forces accurately.
- Published
- 2020
17. Two-sided ultrasonic surface rolling process of aeroengine blades based on on-machine noncontact measurement
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Gong Congyang, Xian-Cheng Zhang, Cheng-Cheng Zhang, Zhang Kaiming, Shuang Liu, Xian Cao, and Shulei Yao
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Blade (geometry) ,Machining ,Computer science ,Universal Software Radio Peripheral ,Mechanical Engineering ,Point cloud ,Process (computing) ,Mechanical engineering ,Ultrasonic sensor ,Motion planning ,Clamping - Abstract
As crucial parts of an aeroengine, blades are vulnerable to damage from long-term operation in harsh environments. The ultrasonic surface rolling process (USRP) is a novel surface treatment technique that can highly improve the mechanical behavior of blades. During secondary machining, the nominal blade model cannot be used for secondary machining path generation due to the deviation between the actual and nominal blades. The clamping error of the blade also affects the precision of secondary machining. This study presents a two-sided USRP (TS-USRP) machining for aeroengine blades on the basis of on-machine noncontact measurement. First, a TS-USRP machining system for blade is developed. Second, a 3D scanning system is used to obtain the point cloud of the blade, and a series of point cloud processing steps is performed. A local point cloud automatic extraction algorithm is introduced to extract the point cloud of the strengthened region of the blade. Then, the tool path is designed on the basis of the extracted point cloud. Finally, an experiment is conducted on an actual blade, with results showing that the proposed method is effective and efficient.
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- 2020
18. Low-cycle fatigue life prediction of a polycrystalline nickel-base superalloy using crystal plasticity modelling approach
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Guang Jian Yuan, Cheng-Cheng Zhang, Shan-Tung Tu, Xian Cheng Zhang, and Bo Chen
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Materials science ,Polymers and Plastics ,Mechanical Engineering ,Metals and Alloys ,Micromechanics ,02 engineering and technology ,Slip (materials science) ,Dissipation ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Finite element method ,0104 chemical sciences ,Superalloy ,Mechanics of Materials ,Materials Chemistry ,Ceramics and Composites ,Grain boundary ,Crystallite ,Composite material ,0210 nano-technology ,Stress concentration - Abstract
A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy. Accumulated plastic slip and energy dissipation as fatigue indicator parameters (FIPs) are used to predict fatigue crack initiation and the fatigue life until failure. Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present. The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8% to 2.4%. Microscopically, the adjacent grain arrangements and their interactions account for the stress concentration. In addition, different sets of grain orientations with the same total grain numbers of 150 were generated using the present model. Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale, although little effect is found on the macroscopic length-scale.
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- 2020
19. A new creep-fatigue crack growth model and a correlation of the creep-fatigue crack growth rate with unified constraint parameter
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Rong-Sheng Lu, Jian-Ping Tan, Jie Yang, Ji Wang, Valery Shlyannikov, Run-Zi Wang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2023
20. Coordinated bilateral ultrasonic surface rolling process on aero-engine blades
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Zhang Kaiming, Cheng-Cheng Zhang, Yi-Xin Liu, Shuang Liu, Shan-Tung Tu, Bo Qian, and Xian-Cheng Zhang
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Surface (mathematics) ,0209 industrial biotechnology ,business.product_category ,Blade (geometry) ,Computer science ,Mechanical Engineering ,Process (computing) ,Mechanical engineering ,02 engineering and technology ,Aero engine ,Industrial and Manufacturing Engineering ,Computer Science Applications ,Machine tool ,020901 industrial engineering & automation ,Control and Systems Engineering ,Ultrasonic sensor ,business ,Software - Abstract
Security and performance of aircraft engines are extremely affected by the blades’ surface quality. Ultrasonic surface rolling process (USRP) can improve material surface properties effectively and increase the alloys’ service life. However, applying USRP onto blades remains a challenge due to the free-form surface with thin-walled leading/trailing edges and the pre-load pressure on the blade during the USRP process. In this paper, a coordinated bilateral method of USRP on the blade is proposed. A machine tool is first designed and integrated with two USRP devices. A method of coordinated bilateral path generation is then proposed, so that the blade surface can be processed by the two USRP devices simultaneously. Finally, we perform experiments on a real aero-engine blade. The results demonstrate that by using the proposed method, USRP can be applied on the bilateral surfaces of the aero-engine blade coordinately.
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- 2019
21. Life prediction and damage analysis of creep-fatigue combined with high-low cycle loading by using a crystal plasticity-based approach
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Kai-Shang Li, Run-Zi Wang, Le Xu, Cheng-Cheng Zhang, Xian-Xi Xia, Min-Jin Tang, Guo-Dong Zhang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2022
22. A modified damage-coupled viscoplastic constitutive model for capturing the asymmetric behavior of a nickel-based superalloy under wide creep-fatigue loadings
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Li Sun, Li-Qiang Liu, Run-Zi Wang, Xiao-Wei Wang, Jian-Ping Tan, Su-Juan Guo, Ji Wang, Ding-Wu Zhang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2022
23. Influence of submerged micro-abrasive waterjet peening on surface integrity and fatigue performance of TA19 titanium alloy
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Shu-Lei Yao, Gong-Yu Wang, Hao Yu, Ji Wang, Kai-Shang Li, Shuang Liu, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2022
24. A life prediction method and damage assessment for creep-fatigue combined with high-low cyclic loading
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Kai-Shang Li, Ji Wang, Zhi-Chao Fan, Lv-Yi Cheng, Shu-Lei Yao, Run-Zi Wang, Xian-Cheng Zhang, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2022
25. On multiaxial creep–fatigue considering the non-proportional loading effect: Constitutive modeling, deformation mechanism, and life prediction
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Le XU, Run-Zi WANG, Ji WANG, Lei HE, Takamoto ITOH, Hideo MIURA, Xian-Cheng ZHANG, and Shan-Tung TU
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science - Published
- 2022
26. Effects of defect size and location on high cycle fatigue life of a maraging stainless steel at ambient and cryogenic temperatures
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Dong-Kai Chang, Qiong-Qi Wang, Hui Chen, Xian-Cheng Zhang, Jian-Feng Wen, and Shan-Tung Tu
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Mechanics of Materials ,Mechanical Engineering ,Modeling and Simulation ,General Materials Science ,Industrial and Manufacturing Engineering - Published
- 2022
27. Influence of grain size on the small fatigue crack initiation and propagation behaviors of a nickel-based superalloy at 650 °C
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Cong-Yang Gong, Run-Zi Wang, Cheng-Cheng Zhang, Yun-Fei Jia, Zhu Xumin, Yao Fu, Shan-Tung Tu, and Xian-Cheng Zhang
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Materials science ,Polymers and Plastics ,Mechanical Engineering ,Alloy ,Metals and Alloys ,Fatigue testing ,02 engineering and technology ,Nickel based ,Edge (geometry) ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Grain size ,0104 chemical sciences ,Superalloy ,Mechanics of Materials ,mental disorders ,Ultimate tensile strength ,Crack initiation ,Materials Chemistry ,Ceramics and Composites ,engineering ,Composite material ,0210 nano-technology - Abstract
GH4169 at 650 °C in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crack initiation life accounted for more percentages of the total fatigue life for the alloy with smaller grain size. The fatigue life generally increased with increasing crack initiation life. The small crack transited to long crack when its length reached ˜10 times the grain size.
- Published
- 2019
28. Effects of the stress state on plastic deformation and ductile failure: Experiment and numerical simulation using a newly designed tension‐shear specimen
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Xue-Wei Zhang, Shan-Tung Tu, Jian-Feng Wen, Xian-Cheng Zhang, and X.G. Wang
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Materials science ,Computer simulation ,Shear (geology) ,Mechanics of Materials ,Mechanical Engineering ,Fracture locus ,General Materials Science ,Composite material - Published
- 2019
29. Effect of thermal annealing on the microstructure, mechanical properties and residual stress relaxation of pure titanium after deep rolling treatment
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Cheng-Cheng Zhang, Xian-Cheng Zhang, Xianfeng Ma, Shan-Tung Tu, Jie Huang, Yun-Fei Jia, and Zhang Kaiming
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Materials science ,Polymers and Plastics ,Annealing (metallurgy) ,Mechanical Engineering ,Metals and Alloys ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Grain size ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Residual stress ,Transmission electron microscopy ,Ultimate tensile strength ,Materials Chemistry ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Tensile testing ,Titanium - Abstract
The aim of this paper was to investigate the effect of thermal annealing on the microstructure, mechanical properties, and residual stress relaxation of deep rolled pure titanium. The microstructure and mechanical properties of the surface modified layer were analyzed by metallographic microscopy, transmission electron microscope and in-situ tensile testing. The results showed that the annealed near-surface layer with fine recrystallized grains had increased ductility but decreased strength after annealing below the recrystallization temperature, where the tensile strength was still higher than that of the substrate. After annealing at the recrystallization temperature, the recrystallized near-surface layer had smaller grain size, similar tensile strength, and higher proportional limit, comparable to those of the substrate. Moreover, the residual stress relaxation showed evidently different mechanisms at three different temperature regions: low temperature (T ≤ 0.2 Tm), medium temperature (T ≈ (0.2‒0.3) Tm), and high temperature (T ≥ 0.3 Tm). Furthermore, a prediction model was proposed in terms of modification of Zener-Wert-Avrami model, which showed promise in characterizing the residual stress relaxation in commercial pure Ti during deep rolling at elevated temperature.
- Published
- 2019
30. Cyclic hardening/softening behavior of 316L stainless steel at elevated temperature including strain-rate and strain-range dependence: Experimental and damage-coupled constitutive modeling
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Xuefang Xie, Shan-Tung Tu, Jingkai Chen, Xian-Cheng Zhang, and Wenchun Jiang
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010302 applied physics ,Cyclic stress ,Materials science ,Mechanical Engineering ,Constitutive equation ,02 engineering and technology ,Plasticity ,Strain rate ,Flow stress ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Mechanics of Materials ,0103 physical sciences ,Hardening (metallurgy) ,General Materials Science ,Composite material ,0210 nano-technology ,Elastic modulus ,Softening - Abstract
In this study, the cyclic mechanical characters of 316L stainless steel at elevated temperature are extensively investigated by the experimental and cyclic constitutive models. The experiments include the monotonic tensile tests with different loading rates and the low cycle fatigue tests considering the effect of strain amplitudes, strain rates and loading sequences. The evolution of cyclic stress amplitudes, hysteresis loops and elastic modulus under various loading conditions are comprehensively analyzed. The experimental results show that the 316L steel at elevated temperature performs a typical three-stage cyclic mechanical response, i.e., initial hardening, subsequent saturation and final accelerated softening. The cyclic softening in both stiffness and flow stress is mainly caused by the nucleation of micro-voids or micro-cracks, and the subsequent coalesce and propagation. Furthermore, although the nearly rate-independent mechanical behavior is observed at monotonic tensile and first several fatigue cycles due to the DSA effect, the cyclic hardening/softening behavior shows a significant strain-rate and loading history dependence. Finally, inspired by the experimental observations and analyses, a damage-coupled cyclic elastic-viscoplastic constitutive model involving strain-range, strain-rate and loading history dependence is proposed to predict the complex cyclic behaviors of the material at elevated temperature. A hardening factor is incorporated into the Chaboche kinematic hardening equations to model the kinematic-induced hardening behavior. And the plastic strain memory surface and the maximum plastic strain rate are introduced to model the strain-range, strain-rate and loading history dependence of cyclic behavior. The proposed model is proved to effectively describe the complex evolution of not only cyclic stress amplitude but also hysteresis loops for the 316L steel at elevated temperature.
- Published
- 2019
31. High temperature fatigue and creep-fatigue behaviors in a Ni-based superalloy: Damage mechanisms and life assessment
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Shan-Tung Tu, Ji Wang, Xian-Cheng Zhang, Run-Zi Wang, Cheng-Cheng Zhang, and Shun-Peng Zhu
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Materials science ,Scanning electron microscope ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,law.invention ,Superalloy ,Cracking ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Creep ,Optical microscope ,Mechanics of Materials ,law ,Modeling and Simulation ,Ultimate tensile strength ,Fracture (geology) ,General Materials Science ,Composite material ,0210 nano-technology ,Electron backscatter diffraction - Abstract
The low cycle fatigue (LCF) and creep-fatigue behaviors of Ni-based GH4169 superalloy are investigated by uniaxial strain-controlled fully-reversed testing at 650 °C. Compared with LCF tests, the effects of tensile and compressive strain hold times on creep-fatigue lifetimes are experimentally explored with varying total strain ranges in the present work. In order to elucidate the damage mechanisms under complex loading waveforms, an additional series of tests with both tensile and compressive hold times are carried out at a given total strain range of 2.0%. Posterior to the cyclic tests, main-crack-failure modes and secondary cracking modes are studied via optical microscopy (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) techniques. Main-crack failure mechanisms are examined by the fracture appearance observations. Cracking modes are explored through quantitative characterization on the distributions of secondary cracks in the longitudinal cross sections under different loading waveforms. Moreover, a generalized life model based on linear damage summation (LDS) framework and energy dissipation criterion (EDC) is elaborated to estimate the damage mechanisms of fatigue, creep and oxidation. The prediction results can well establish the correlations between the reductions of numbers of cycles to failure and the presences of different damage mechanisms under respective loading waveforms.
- Published
- 2019
32. Dislocation-based crystal plasticity modelling of a nickel-based superalloy under dwell-fatigue: From life prediction to residual life assessment
- Author
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Guo-Dong Zhang, Lv-Yi Cheng, Xian-Cheng Zhang, Kai-Shang Li, Run-Zi Wang, Ti-Wen Lu, Shan-Tung Tu, and Zhi-Chao Fan
- Subjects
Work (thermodynamics) ,Materials science ,business.industry ,Mechanical Engineering ,Structural engineering ,Dissipation ,Residual ,Industrial and Manufacturing Engineering ,Finite element method ,Superalloy ,Mechanics of Materials ,Robustness (computer science) ,Modeling and Simulation ,General Materials Science ,Dislocation ,business ,Damage tolerance - Abstract
In this work, a dislocation-based crystal plasticity finite element (CPFE) framework was implemented to investigate the effects of loading conditions on dwell-fatigue crack initiation life. Experimentally, a large number of strain-controlled dwell-fatigue tests were carried out at 650 ℃ in a nickel-based superalloy. The combinations of CPFE simulations and post-test examinations were used to reveal the dwell-fatigue crack initiation mechanisms. Then, a life prediction approach was presented on the basis of accumulated energy dissipation at half-life cycle. Good agreement between the experimental and simulated lives verifies the robustness as well as the accuracy of the present approach. Finally, a new three-dimensional (3-D) damage tolerance diagram was proposed by introducing a CP-based physical parameter to describe the degradation levels and evaluate the residual dwell-fatigue life.
- Published
- 2022
33. Operation Status of Teleoperator Based Shared Control Telerobotic System
- Author
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Runhuai Yang, Shulei Yao, Shuang Liu, Xian-Cheng Zhang, and Guodong Zhu
- Subjects
0209 industrial biotechnology ,Artificial neural network ,Computer science ,Mechanical Engineering ,Control (management) ,Online identification ,Control engineering ,02 engineering and technology ,Industrial and Manufacturing Engineering ,Identification (information) ,020901 industrial engineering & automation ,Artificial Intelligence ,Control and Systems Engineering ,Control theory ,Electrical and Electronic Engineering ,Software ,Control methods - Abstract
Telerobotic system is a typical human-machine system. The operation results not only depend on the performance of machine, but also the status of teleoperators (SoT). However, existing telerobotic systems scarcely consider the impact of teleoperators. This paper proposes a method for the online identification of the SoT and incorporates it to a shared control telerobotic system. First, some mental indicators are obtained based on Electroencephalogram during teleoperations. The relationship between the SoT and mental indicators is then established by a neural network. The online SoT identification is further implemented on a mobile telerobotic system. Second, a SoT based shared control framework is proposed in telerobotic system. The SoT is designed to dynamically adjust the control weight of the shared controller. Finally, comparative experiments are performed between a sensor based shared control method and the SoT based shared control method. The result validates the effectiveness of the proposed SoT based shared control method in telerobotic system.
- Published
- 2020
34. Chemical short-range order strengthening mechanism in CoCrNi medium-entropy alloy under nanoindentation
- Author
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Hao Chen, Xian-Cheng Zhang, Xiao-Feng Yang, Shan-Tung Tu, Chen-Yun He, and Yongzhi Xi
- Subjects
Materials science ,Mechanical Engineering ,Alloy ,Metals and Alloys ,Nucleation ,Thermodynamics ,engineering.material ,Nanoindentation ,Condensed Matter Physics ,Entropy (classical thermodynamics) ,Molecular dynamics ,Mechanics of Materials ,Short range order ,engineering ,General Materials Science ,Dislocation ,Solid solution - Abstract
The strengthening effect of chemical short-range order (SRO) structure in CoCrNi medium-entropy alloy (MEA) was investigated using molecular dynamics (MD) simulations of nanoindentation. The quantitative correlation between SRO parameters and mechanical properties was established. Results show that the strength and hardness of CoCrNi MEA increase with increasing chemical SRO parameters and reach a stable value with steady SRO structure. Compared with random solid solution (RSS) state model, the average hardness increases 8.1 % in an intermediate SRO model and 13.7 % in a stable SRO model. The dislocation nucleation force of SRO model is 55 % larger than RSS model. Moreover, dislocation pinning induced by local Ni SRO structure, as well as the promoted unique dislocation interaction were observed during the nanoindentation process. Finally, results also show that as the temperature rises, the enhancement of hardness becomes more significant ( 11.4 % at 70 K , 17.24 % at 300 K , and 23.8 % at 800 K ).
- Published
- 2022
35. Fracture toughness assessment of the X80 steel by nanoindentation technique and a modified constitutive model
- Author
-
Shan-Tung Tu, Xian-Cheng Zhang, Yu-Cai Zhang, and Wenchun Jiang
- Subjects
Materials science ,Three point flexural test ,Applied Mathematics ,Mechanical Engineering ,Constitutive equation ,Strain energy density function ,Fracture mechanics ,Nanoindentation ,Condensed Matter Physics ,Fracture toughness ,Indentation ,General Materials Science ,Composite material ,Elastic modulus - Abstract
Fracture toughness of X80 steel is investigated and characterized by the nanoindentation technique and a modified constitutive model. Firstly the load-displacement of the X80 steel is tested by nanoindentation technique. Based on the load-displacement, the relationship of the nanoindentation load-depth is established. Secondly, the elastic modulus calculation equation was modified by introducing the radial displacement correction factor γ considering the pile-up phenomenon. At last, based on the strain energy density and indentation fracture energy theory, the nanoindentation fracture toughness constitutive model of X80 is proposed combined with the modified elastic modulus and the critical plastic depth. The fracture toughness calculated by the proposed method locates in the dispersion band range tested by the standard three point bending specimen, while the result calculated by the original method is far away from the dispersion band range. The comparison results illustrate that the proposed method can well characterize the fracture toughness of the X80 steel. The present work is of great significant for ensuring the long term and safety operation of the petroleum and natural gas transporting pipeline.
- Published
- 2022
36. Creep-fatigue life prediction in nickel-based superalloy GH4169 based on microstructural damage quantification with the help of electron backscatter diffraction
- Author
-
Yang Zhang, Xian-Cheng Zhang, Hao Chen, Run-Zi Wang, and Shan-Tung Tu
- Subjects
Materials science ,Scanning electron microscope ,Creep-fatigue ,02 engineering and technology ,Unified viscoplastic model ,010402 general chemistry ,01 natural sciences ,Interaction diagram ,Stress relaxation ,lcsh:TA401-492 ,General Materials Science ,Composite material ,Life assessment ,Viscoplasticity ,Interaction overview diagram ,Mechanical Engineering ,Damage mechanism ,Strain energy density function ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Superalloy ,Mechanics of Materials ,Fracture (geology) ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology ,Electron backscatter diffraction - Abstract
A series of strain-controlled creep-fatigue tests under different loading waveforms are carried out on GH4169 superalloy at 650 °C. In the macroscopic view, a unified viscoplastic constitutive framework is used to describe cyclic deformation process. Particularly, a modified kinematic hardening rule considering loading-dependent effect is developed to simulate the stress relaxation behavior during hold periods. Then, creep-fatigue assessment based on interaction diagram is quantitatively determined by the strain energy density exhaustion (SEDE) approach. In order to elucidate damage mechanisms under various loading conditions, the characterization of damage mechanism is observed from the post-test examination. Main-crack-failure modes from fracture appearance observations and cracking modes from longitudinal sections are studied via scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD), respectively. Furthermore, image-based creep-fatigue diagram is proposed based on metallographic interpretation of mechanisms.
- Published
- 2020
37. A dual-scale modelling approach for creep-fatigue crack initiation life prediction of holed structure in a nickel-based superalloy
- Author
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Kai Shang Li, Lv Yi Cheng, Yong Zhang, Hideo Miura, Yilun Xu, Run-Zi Wang, Xian Cheng Zhang, and Shan-Tung Tu
- Subjects
Materials science ,Scale (ratio) ,business.industry ,Mechanical Engineering ,Structural engineering ,0905 Civil Engineering ,Industrial and Manufacturing Engineering ,Dual (category theory) ,Stress (mechanics) ,Superalloy ,Mechanics of Materials ,Modeling and Simulation ,Mechanical Engineering & Transports ,General Materials Science ,Boundary value problem ,Macro ,Deformation (engineering) ,Inconel ,business ,0913 Mechanical Engineering - Abstract
In this paper, a dual-scale modelling approach is developed to investigate creep-fatigue behavior and predict crack initiation life for holed structures under multi-axial stress state. The macro-scale simulation supplies local deformation histories to the dual-scale simulation as boundary conditions. In the dual-scale simulation process, the micro-mechanical behavior and damage evolution are described by using crystal plasticity. In order to validate the dual-scale simulation procedures, a series of creep-fatigue tests as well as the post-test characterizations were carried out for nickel-based Inconel 718 at 650 ℃. The detailed results of macro- and micro-scale simulations are presented in terms of stress–strain behavior, damage evolution and life prediction. Regarding the macro-scale simulations as the benchmark, it may provide an assistant support and precognition for the micro-scale damage calculation at higher cycles. The predicted cycle numbers to crack initiation are in agreement with the experimental ones. More advantages are manifested in the potential scientific and engineering significance for the dual-scale modelling approach.
- Published
- 2022
38. A novel cold expansion process for improving the surface integrity and fatigue life of small-deep holes in Inconel 718 superalloys
- Author
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Shulei Yao, Xue-Lin Lei, Run-Zi Wang, Xian-Cheng Zhang, Shan-Tung Tu, and Cen-Yao He
- Subjects
Materials science ,Scanning electron microscope ,Mechanical Engineering ,Microstructure ,Industrial and Manufacturing Engineering ,Superalloy ,Mechanics of Materials ,Residual stress ,Modeling and Simulation ,Surface roughness ,General Materials Science ,Deformation (engineering) ,Composite material ,Inconel ,Surface integrity - Abstract
Hole cold expansion is an effective anti-fatigue manufacturing technology, which is widely used in hole strengthening of aviation components. In this paper, a novel small-deep hole (with the diameter less than 2 mm and the depth greater than 10 mm) cold expansion process, called the multi-spherical bump rotating cold expansion process (MBR-CEP), was proposed and verified by experiments on the Inconel 718 superalloy. The MBR-CEP tool with multi-spherical bumps produced by the laser texturing process (LTP) was first designed, and the MBR-CEP with different expansion degrees (δ = 2.1%, 2.6%, and 3.1%) was conducted on small-deep hole specimens. The surface integrity of the small-deep holes before and after the MBR-CEP in the inlet, middle, and outlet areas was studied. Results showed that compared with the small-deep hole after reaming, the hole treated by the MBR-CEP with different δ formed a plastic deformation layer with a maximum depth of 32.73–85.54 μm, a minimum surface roughness of 0.115–0.138 μm in Ra, and a compressive residual stress (CRS) layer with a depth of 0.39–1.077 mm. In addition, the CRS increased by up to 84%, and the microhardness increased by up to 13%. The microstructure evolution on the top surface and sub-surface of the small-deep hole wall was observed by transmission electron microscopy (TEM), which showed that nanocrystals with the size of 48–90 nm and a large number of dislocations and deformation twins formed. Finally, the effectiveness of the proposed process was verified by fatigue tests with different δ at 400 ° C . The average fatigue life increased by 3.66 and 8.05 times under δ = 2.1% and 2.6%, respectively. The fatigue fracture surface was examined with scanning electron microscopy (SEM), which revealed that low surface roughness and existence of a plastic deformation layer could effectively reduce the probability of crack initiation.
- Published
- 2022
39. Fatigue life prediction of nickel-based GH4169 alloy on the basis of a multi-scale crack propagation approach
- Author
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Xian-Cheng Zhang, Peng-Yue Zhang, Shen Ye, Run-Zi Wang, Shan-Tung Tu, and Cheng-Cheng Zhang
- Subjects
Materials science ,Basis (linear algebra) ,Scale (ratio) ,business.industry ,Mechanical Engineering ,Alloy ,Fracture mechanics ,02 engineering and technology ,Structural engineering ,Nickel based ,Integral form ,engineering.material ,021001 nanoscience & nanotechnology ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,engineering ,General Materials Science ,0210 nano-technology ,business - Abstract
This paper was concerned with an approach to predict fatigue life based on a multi-scale crack propagation model. The expressions of crack propagation rates in microstructurally small crack (MSC), physically small crack (PSC) and long crack (LC) stages were unified in the multi-scale crack propagation model. Its integral form presented a fatigue life prediction approach. The nickel-based GH4169 alloy was employed to validate the prediction capacity of present approach. The prediction results of lives of specimens with different initial defects sizes were compared with the experimental data.
- Published
- 2018
40. Experimental investigation and numerical prediction on creep crack growth behavior of the solution treated Inconel 625 superalloy
- Author
-
Zhang Yucai, You-Jun Ye, Xian-Cheng Zhang, Wenchun Jiang, Shan-Tung Tu, and Run-Zi Wang
- Subjects
Materials science ,Mechanical Engineering ,Numerical analysis ,Failure mechanism ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Inconel 625 ,Intergranular fracture ,Constraint (information theory) ,Superalloy ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Creep ,Mechanics of Materials ,Crack initiation ,General Materials Science ,Composite material ,0210 nano-technology - Abstract
Creep crack growth behaviors of the Inconel 625 superalloy at 650 °C are investigated through experimental and numerical methods. The simulated data agree well with the experimental results, reflecting that the multi-axial creep performance parameter α obtained by present paper can reasonably predict the creep crack growth behaviors of Inconel 625 superalloy. The crack initiation time takes up the most proportion of the whole life for all the load levels, and intergranular fracture is the dominated failure mechanism. Creep constraint effect is not obvious for the C∗ to characterize the creep crack growth of Inconel 625 superalloy.
- Published
- 2018
41. Computational-experimental approaches for fatigue reliability assessment of turbine bladed disks
- Author
-
Shun-Peng Zhu, Xian-Cheng Zhang, Weiwen Peng, and Qiang Liu
- Subjects
Computer science ,business.industry ,Mechanical Engineering ,Constitutive equation ,Probabilistic logic ,Experimental data ,02 engineering and technology ,Structural engineering ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Turbine ,Finite element method ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,General Materials Science ,Sensitivity (control systems) ,0210 nano-technology ,business ,Random variable ,Reliability (statistics) ,Civil and Structural Engineering - Abstract
In the present study, a computational-experimental framework is developed for fatigue reliability assessment of turbine bladed disks. Within the framework, the overspeed testing is innovatively combined with stochastic finite element (FE) analysis for quantifying uncertainties in the experimental data, material properties and loads. Meanwhile, two schemes are elaborated based on probabilistic S-N curves and stochastic FE simulation coupling with sampling technique. The stochastic FE simulation incorporates the Chaboche constitutive model with Fatemi–Socie criterion for fatigue behavior modeling and life prediction. Moreover, experimental deformation and numerical FE analysis are conducted with regard to the full-scale bladed disk test with increased step-stress overloading. Reliability sensitivity analysis is performed to provide an importance ranking of random variables for fatigue design of the bladed disk. Results indicate that stochastic FE analysis-based scheme provides more conservative predictions than the probabilistic S-N curves-based one.
- Published
- 2018
42. Effects of low-temperature transformation and transformation-induced plasticity on weld residual stresses: Numerical study and neutron diffraction measurement
- Author
-
Xian-Cheng Zhang, Wenchun Jiang, Shan-Tung Tu, Wanchuck Woo, Vyacheslav Em, and Chen Wei
- Subjects
010302 applied physics ,Materials science ,Mechanical Engineering ,Neutron diffraction ,02 engineering and technology ,Welding ,Plasticity ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,law.invention ,Compressive strength ,Mechanics of Materials ,law ,Residual stress ,Ferrite (iron) ,Diffusionless transformation ,0103 physical sciences ,lcsh:TA401-492 ,General Materials Science ,lcsh:Materials of engineering and construction. Mechanics of materials ,Composite material ,0210 nano-technology - Abstract
In this study, the weld residual stresses (RS) in a 25 mm thick ferrite steel plate with newly developed low-temperature transformation (LTT) welding wire were investigated by finite element method and neutron diffraction (ND) measurement. A thermo-elastic–plastic finite element model coupled with solid-state phase transformation (SSPT) was developed to investigate the distribution and formation mechanism of RS, which has been verified by ND measurement. The results demonstrate that the developed LTT alloy can significantly reduce the RS and even generate compressive RS in the weld zone, due to the interrupted cooling shrinkage caused by the LTT. The higher inter-pass temperatures related to the microstructure evolution result in an increased region of compressive stress within the weldment. Moreover, the longitudinal RS in the weld zone gradually changes to tension as the initial temperature of martensitic transformation increases. Notably, the relaxation effect of transformation-induced plasticity on RS and its influence on model accuracy were discussed. Keywords: Weld residual stress, Low-temperature transformation, Transformation-induced plasticity
- Published
- 2018
43. Experimental and simulated investigations of low cycle fatigue behavior in a nickel-based superalloy with different volume fractions of δ phase
- Author
-
Dong-Feng Li, Run-Zi Wang, Wen-Bo Zhu, Shan-Tung Tu, Xian-Cheng Zhang, Guang-Jian Yuan, and Yong Zhang
- Subjects
Phase boundary ,Materials science ,Mechanical Engineering ,Alloy ,chemistry.chemical_element ,Slip (materials science) ,engineering.material ,Industrial and Manufacturing Engineering ,Superalloy ,Nickel ,Volume (thermodynamics) ,chemistry ,Mechanics of Materials ,Modeling and Simulation ,Phase (matter) ,engineering ,General Materials Science ,Grain boundary ,Composite material - Abstract
The fatigue crack initiation life and damage mechanisms of three heat-treated nickel-based alloy with different volume fractions of δ phase have been investigated based on experiment and crystal plasticity simulation. With the help of fatigue indicator parameters (FIPs), the predicted fatigue lives are agreed well with experimental results, where energy dissipation based FIP shows more accurate life prediction than plastic slip based FIP does. Maximum fatigue damage sites shift from grain boundary to δ phase boundary by increasing δ phase and applied strain level. Furthermore, the existence of δ phase leads to the increase of plastic slip accumulation and decrease of localized stress level.
- Published
- 2021
44. Research on low temperature brittleness of 30Cr1Mo1V high-temperature rotor and its life optimization in rapid start-up and warm-up process
- Author
-
Guodong Zhang, Fei Xue, Zhongbing Chen, Xianxi Xia, Xian-Cheng Zhang, and Minjin Tang
- Subjects
Toughness ,Materials science ,Power station ,Rotor (electric) ,Mechanical Engineering ,Mechanical engineering ,Turbine ,law.invention ,Stress (mechanics) ,Brittleness ,Mechanics of Materials ,Steam turbine ,law ,Fracture (geology) ,General Materials Science - Abstract
Recently, there is the serious fracture for two high-temperature steam turbine rotors made of 30Cr1Mo1V steel in different power plants, characterized by brittle fracture. This steel has the disadvantage of low temperature brittleness. Currently, a large number of 30Cr1Mo1V rotors are in service. Meanwhile, these rotors are required to start up and warm up faster due to the demand for operation flexibility of the power system. In order to ensure the safety of the 30Cr1Mo1V rotors under flexible operation, it is necessary to study the low temperature brittleness of the rotors and its influence on the fatigue life in rapid start-up and warm-up processes. In this paper, the fracture causes of the 30Cr1Mo1V rotor were analyzed by the mechanical property tests, microstructure examination and fracture analysis. The test results showed that the toughness of rotor decreased significantly after service. Secondly, the temperature and stress changes of the high-temperature rotors during the rapid start-up and warm-up process were calculated by the finite element method. The simulation results showed that if the speed rose too fast, the thermal stress in the rotor inlet area would increase significantly and the temperature was lower than the fracture appearance transition temperature when reaching the full speed. The high stress will easily lead to a crack initiation under low-cycle fatigue. Then, crack instability propagation will soon occur due to the low temperature and poor toughness. Thirdly, the life of the turbine in the rapid start-up was optimized by controlling the startup time. In addition, the life under different warm-up conditions was quantitatively analyzed. It not only reveals the necessity of the warm-up process for the center hole rotor, but also successfully demonstrates that the warm-up process of the solid rotor can be cancelled, which improves the economy of the power plant.
- Published
- 2021
45. Creep crack growth behavior analysis of the 9Cr-1Mo steel by a modified creep-damage model
- Author
-
You-Jun Ye, Xian-Cheng Zhang, Shan-Tung Tu, Wenchun Jiang, and Yu-Cai Zhang
- Subjects
Materials science ,business.industry ,Bar (music) ,Finite element software ,Mechanical Engineering ,Coordinate system ,Diffusion creep ,02 engineering and technology ,Structural engineering ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Stress (mechanics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Creep ,Mechanics of Materials ,General Materials Science ,Growth rate ,0210 nano-technology ,business ,Ductility (Earth science) - Abstract
Creep crack growth behavior of the 9Cr-1Mo steel under multi-axial stress state at 600 °C was investigated by a modified creep damage model. Firstly, a modified creep damage model was proposed and incorporated into the finite element software ABAQUS by the CREEP subroutine. And then the creep and damage behaviors of the 9Cr-1Mo steel were simulated by the notched bar and CT specimen. The results indicate that the multi-axial creep ductility and the life of the high temperature components calculated by the modified model are corresponding well with the experimental data, and the life prediction precision has been greatly improved compared to that from the K-R model. This demonstrates that the proposed model can be used to accurately predict the creep crack growth behaviors of the high temperature materials. The creep crack growth rate a presents a linear relationship with the crack driving force parameter C* in log-log coordinate system. Based on the established relationship between the a and C*, the creep crack growth rate of the 9Cr-1Mo steel components working at high temperatures can be predicted.
- Published
- 2017
46. A generalized strain energy density exhaustion model allowing for compressive hold effect
- Author
-
Jian-Guo Gong, Shan-Tung Tu, Run-Zi Wang, Xian-Cheng Zhang, Cheng-Cheng Zhang, and Zhu Xumin
- Subjects
Work (thermodynamics) ,Materials science ,business.industry ,Interaction overview diagram ,Mechanical Engineering ,Strain energy density function ,02 engineering and technology ,Structural engineering ,Mechanics ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,Superalloy ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Creep ,Mechanics of Materials ,Modeling and Simulation ,General Materials Science ,0210 nano-technology ,business ,Inconel - Abstract
The aim of the present work is to propose a generalized strain energy density exhaustion model to predict the creep-fatigue lives. The oxidation damage, which is described by a correction factor representing the non-linear oxidation damage mechanism, is considered in the proposed model. All the 77 experimental data sets of GH4169 superalloy at 650 °C, Inconel 738 superalloy at 850 °C and P91 steel at 550 °C in both tension-hold-only and compression-hold-only tests are used to validate the prediction capabilities of the model. The fatigue, creep and oxidation damages per cycle are separately calculated. Then a three-dimensional damage interaction diagram combined with a suitable enveloping surface is proposed.
- Published
- 2017
47. Cycle-dependent creep-fatigue deformation and life predictions in a nickel-based superalloy at elevated temperature
- Author
-
Lv Yi Cheng, Shun-Peng Zhu, Xian Cheng Zhang, Run-Zi Wang, Peng Cheng Zhao, Shan-Tung Tu, Ji Wang, and Hideo Miura
- Subjects
Materials science ,Strain (chemistry) ,Mechanical Engineering ,chemistry.chemical_element ,Strain energy density function ,02 engineering and technology ,Creep fatigue ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Superalloy ,Dwell time ,Nickel ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Creep ,chemistry ,Mechanics of Materials ,General Materials Science ,Deformation (engineering) ,Composite material ,0210 nano-technology ,Civil and Structural Engineering - Abstract
A series of strain-controlled creep-fatigue tests with various dwell times and strain ratios are carried out on a nickel-based superalloy at 650 °C. Aiming at the mechanical understanding of creep-fatigue behavior, a non-unified constitutive framework is used to describe macroscopic cyclic deformation process to understand creep-fatigue behavior. Afterward, the quantitative evaluation of creep-fatigue damage is quantitatively determined by the cycle-by-cycle strain energy density exhaustion (SEDE) approach. The effects of strain ratio and dwell time on creep-fatigue life endurances can be well revealed by the proposed life model, where all the data points are predicted within ± 1.5 error band. Particularly, life prediction capacities with long dwell times are further improved based on three-regime creep mechanism.
- Published
- 2021
48. Damage behaviour in different micro-regions of P92 steel weldment under sequential low cycle fatigue and creep loading
- Author
-
Xiaowei Wang, Xian-Cheng Zhang, Wei Zhang, Zitong Kang, Yong Jiang, Tianyu Zhang, and Jianming Gong
- Subjects
Heat-affected zone ,Materials science ,Mechanical Engineering ,Lath ,engineering.material ,Nanoindentation ,Grain size ,Creep ,Mechanics of Materials ,Martensite ,engineering ,General Materials Science ,Composite material ,Elastic modulus ,Electron backscatter diffraction - Abstract
Understanding the evolution of microstructure and micro-region properties of weldments during cyclic loading is a challenge for the reliability assessment of high-temperature components. This work is devoted to quantitatively evaluating the variation of micro-region properties and corresponding responsible microstructural features of P92 steel weldments under interrupted fatigue tests and subsequent creep fracture. To achieve this target, high-resolution characterization techniques, including electron backscatter diffraction (EBSD) and nanoindentation tester were used. The results revealed that the microstructures in the inter-critical heat affected zone (ICHAZ) and adjacent regions, fine-grained HAZ (FGHAZ) and parent metal (PM), show significant sensitivity to fatigue loading. Notably, the grain size in the ICHAZ reaches saturation after fatigue cycles of 10% fatigue lifetime, and the weld metal (WM) keeps unchanged throughout the fatigue loading. After subsequent creep fracture, only the WM presents an increasing trend in the average grain size. Nanoindentation tests uncover that the reductions of the elastic modulus and microhardness in each region also present three cyclic softening behaviour during the fatigue process due to the evolution of martensite lath structure. However, due to nucleation and growth of cavities accelerated by carbide precipitation, relatively low elastic modulus and microhardness were observed after subsequent creep loading.
- Published
- 2021
49. Multi-stage dwell fatigue crack growth behaviors in a nickel-based superalloy at elevated temperature
- Author
-
Xian Cheng Zhang, Hideo Miura, Run-Zi Wang, Ji Wang, Yan Cui, Shan-Tung Tu, and You Jun Ye
- Subjects
Materials science ,Mechanical Engineering ,0211 other engineering and technologies ,02 engineering and technology ,Intergranular corrosion ,Paris' law ,Superalloy ,Multi stage ,Dwell time ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Deflection (engineering) ,General Materials Science ,Composite material ,Inconel ,021101 geological & geomatics engineering ,Electron backscatter diffraction - Abstract
A series of continuous and interrupted cyclic tests in Inconel 718 with the dwell times ranging from 0 s to 10,800 s at 650 °C were carried out in order to study the multi-stage dwell fatigue crack growth (DFCG) behavior. Replica technique was used to measure the intermittent DFCG rates from short to long periods and to retrospect specific damage mechanisms based on microstructural characterizations. From the macroscopic viewpoint, the DFCG curves were classified into short, moderate and long dwell conditions according to the tendencies in DFCG rates. Correspondingly, the dwell fatigue life distribution was divided into three periods, which exhibit different sensitivities in the length of dwell time on dwell fatigue life. From the microscopic viewpoint, the high-scattered points reflected in the DFCG curves were elaborately discussed with the combinations of EBSD mapping and high-resolution TEM analysis. Σ3 twin boundaries (Σ3 TBs) were regarded as the barriers to resist the DFCG due to their special performances. In addition, with the increase of dwell times, the main crack morphologies changed from transgranular to intergranular mode. Simultaneously, local crack growth modes at high-scattered points changed from across to along the Σ3 TBs with extreme low DFCG rates. Also, high-angle crack deflection was another factor that was responsible for the decrease of the DFCG rates.
- Published
- 2021
50. Semi-quantitative creep-fatigue damage analysis based on diffraction-based misorientation mapping and the correlation to macroscopic damage evolutions
- Author
-
Lv Yi Cheng, Shun-Peng Zhu, Xian Cheng Zhang, Shan-Tung Tu, Run-Zi Wang, Peng Cheng Zhao, and Hideo Miura
- Subjects
Diffraction ,Materials science ,Misorientation ,Scanning electron microscope ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,Superalloy ,Dwell time ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,Transmission electron microscopy ,Modeling and Simulation ,General Materials Science ,Dislocation ,Composite material ,0210 nano-technology ,Electron backscatter diffraction - Abstract
A large number of strain-controlled creep-fatigue tests under wide loading waveforms are conducted at 650 ℃ in nickel-based forged GH4169 superalloy. Comprehensive characterizations, including scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and transmission electron microscope (TEM), are observed from the post-test examinations. Particular focus is brought to the physical understanding of damage mechanisms under wide creep-fatigue loading conditions using EBSD analysis. The representative misorientation parameters are calculated for constructing diffraction-based misorientation mapping. Semi-quantitative analysis of longitudinal EBSD observations is conducted to prove that strain ratio has little influence on creep-fatigue damage degrees, while dwell time causes noticeable changes to damage progressions. In particular for geometrically necessary dislocation (GND) map explored in this work, more fundamental information based on failure physics is obtained to analyze the creep-fatigue crack initiation mechanism.
- Published
- 2021
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