| 1. |
|
|
| 2. |
-
- 2019
-
Journal article (peer-reviewed)
|
|
| 3. |
- Chen, Guang, et al.
(author)
-
Dynamic analysis of the effect of nose length on train aerodynamic performance
- 2019
-
In: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 184, s. 198-208
-
Journal article (peer-reviewed)abstract
- The improved delayed detached eddy simulation (IDDES) was used to study the influence of the train’s nose length on its aerodynamic performance. Both the time-averaged and instantaneous near-wake structures and the associated distribution of slipstream velocity are compared for three nose lengths. As the nose length increases, the mean and Std values of the drag and lift force are decreased. The shorter nose-length case results in a higher slipstream velocity. In particular, at the TSI track-side position, the TSI value U_2δ for the 5-m nose length case is 30% and 32% higher than the corresponding values for the 7.5-m and 10-m nose length cases, respectively. The dynamical flow topology in the wake reveals that the flow structures of the 5-m nose length are different from those of the other two cases in the tail streamline surface. As nose length increases, the longitudinal vortices are weaker, and the angle and distance between the longitudinal vortices are smaller. The shear production from the P_xy caused by the separation of the boundary layer at the lateral wall of the tail train is greater than that of the P_xz caused by the separation of the boundary layer at the top and bottom of the tail train.
|
|
| 4. |
|
|
| 5. |
- Chen, Zhe, 1987-, et al.
(author)
-
Effect of Machining Parameters on Cutting Force and Surface Integrity when High-Speed Turning AD730™ with PCBN Tools
- 2019
-
In: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 100:9-12, s. 2601-2615
-
Journal article (peer-reviewed)abstract
- The novel wrought nickel-based superalloy, AD 730™, is a good candidate material for turbine disc applications at high temperatures beyond 650 °C. The present study focuses on the machining performance of this newly developed alloy under high-speed turning conditions with advanced PCBN tools. Meanwhile, the machined surface integrity as influenced by cutting speed and feed rate was also investigated. The surface integrity was thoroughly characterized in terms of surface roughness and morphology, machining-induced plastic deformation, white layer formation, and residual stresses. It has been found that the cutting speed and feed rate had a strong effect on the cutting forces and resultant surface integrity. The cutting forces required when machining the alloy were gradually reduced with increasing cutting speed, while at 250 m/min and above, the flank tool wear became stronger which led to increased thrust force and feed force. A higher feed rate, on the other hand, always resulted in higher cutting forces. Increasing the cutting speed and feed rate in general deteriorated the surface integrity. High cutting speeds within the range of 200–250 m/min and a low feed rate of 0.1 mm/rev are preferable in order to implement more cost-effective machining without largely reducing the surface quality achieved. The formation of tensile residual stresses on the machined AD 730™, however, could be of a concern where good fatigue resistance is critical.
|
|
| 6. |
- Chen, Zhe, et al.
(author)
-
Nano-scale characterization of white layer in broached Inconel 718
- 2017
-
In: Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing. - Amsterdam : Elsevier BV. - 0921-5093 .- 1873-4936. ; 684, s. 373-384
-
Journal article (peer-reviewed)abstract
- The formation mechanism of white layers during broaching and their mechanical properties are not well investigated and understood to date. In the present study, multiple advanced characterization techniques with nano-scale resolution, including transmission electron microscopy (TEM), transmission Kikuchi diffraction (TKD), atom probe tomography (APT) as well as nano-indentation, have been used to systematically examine the microstructural evolution and corresponding mechanical properties of a surface white layer formed when broaching the nickel-based superalloy Inconel 718.TEM observations showed that the broached white layer consists of nano-sized grains, mostly in the range of 20–50 nm. The crystallographic texture detected by TKD further revealed that the refined microstructure is primarily caused by strong shear deformation. Co-located Al-rich and Nb-rich fine clusters have been identified by APT, which are most likely to be γ′ and γ′′ clusters in a form of co-precipitates, where the clusters showed elongated and aligned appearance associated with the severe shearing history. The microstructural characteristics and crystallography of the broached white layer suggest that it was essentially formed by adiabatic shear localization in which the dominant metallurgical process is rotational dynamic recrystallization based on mechanically-driven subgrain rotations. The grain refinement within the white layer led to an increase of the surface nano-hardness by 14% and a reduction in elastic modulus by nearly 10% compared to that of the bulk material. This is primarily due to the greatly increased volume fraction of grain boundaries, when the grain size was reduced down to the nanoscale.
|
|
| 7. |
- Chen, Zhe, et al.
(author)
-
Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures
- 2016
-
In: Metallurgical and Materials Transactions. A. - : Springer. - 1073-5623 .- 1543-1940. ; 47A:7, s. 3664-3676
-
Journal article (peer-reviewed)abstract
- The current study focused on the surface integrity issues associated with broaching of Inconel 718 and the structural stability of the broached specimen at high temperatures, mainly involving the microstructural changes and residual stress relaxation. The broaching operation was performed using similar cutting conditions as that used in turbo machinery industries for machining fir-tree root fixings on turbine disks. Thermal exposure was conducted at 723 K, 823 K, and 923 K (450 A degrees C, 550 A degrees C, and 650 A degrees C) for 30, 300, and 3000 hours, respectively. Surface cavities and debris dragging, sub-surface cracks, high intensity of plastic deformation, as well as the generation of tensile residual stresses were identified to be the main issues in surface integrity for the broached Inconel 718. When a subsequent heating was applied, surface recrystallization and alpha-Cr precipitation occurred beneath the broached surface depending on the applied temperature and exposure time. The plastic deformation induced by the broaching is responsible for these microstructural changes. The surface tension was completely relaxed in a short time at the temperature where surface recrystallization occurred. The tensile layer on the sub-surface, however, exhibited a much higher resistance to the stress relief annealing. Oxidation is inevitable at high temperatures. The study found that the surface recrystallization could promote the local Cr diffusion on the broached surface.
|
|
| 8. |
- Jiang, Dong-yi, et al.
(author)
-
Surface water quality and potential health risk assessments in Changsha-Zhuzhou-Xiangtan section of Xiangjiang River, China
- 2019
-
In: journal of central south university. - : Springer Science and Business Media LLC. - 2095-2899 .- 2227-5223. ; 26:12, s. 3252-3260
-
Journal article (peer-reviewed)abstract
- The Changsha-Xiangtan-Zhuzhou City Group is a heavy industrial district and accepted as the serious pollution area in the Xiangjiang River basin. In this study, 7 metals (Pb, Hg, Cd, As, Zn, Cu and Se) and the river water quality parameters including pH, dissolved oxygen (DO), Escherichia coli (E. coli), potassium permanganate index (CODMn), dichromate oxidizability (CODCr), five-day biochemical oxygen demand (BOD5), ammonia nitrogen (NH4+-N), total nitrogen (TN), total phosphorus (TP) and fluoride (F-) in 18 sampling sites of the Changsha-Xiangtan-Zhuzhou section are monthly monitored in 2016, which is the year to step into the second stage of the Xiangjiang River Heavy Metal Pollution Control Implementation Plan. It is found that E. coli, TN and TP are the main pollutants in the Changsha-Zhuzhou-Xiangtan section, and the pollution of heavy metal is not serious but As with potential risk to local people especially children should be concerned. In addition, Xiangtan city is mainly featured with heavy metal pollution, while Zhuzhou and Changsha city are both featured with other pollutants from municipal domestic sewage.
|
|
| 9. |
- Persson, Henrik, et al.
(author)
-
Modelling tool life in high speed machining of AD730
- 2018
-
In: Procedia Manufacturing. - : Elsevier BV. - 2351-9789. ; 25, s. 316-321, s. 316-321
-
Journal article (peer-reviewed)abstract
- AD730® is a new type of nickel-based superalloy, developed by Aubert & Duval, with high temperature properties exceeding conventional superalloys such as Alloy 718. This paper presents the tool life model for this superalloy for the purpose of process optimization and manufacturing cost estimation. The tool life modelling is based on comprehensive machining tests, using the Colding model. The cutting tool material used is CBN 170, a grade specially designed and optimized for machining of nickel-based superalloys.
|
|
| 10. |
- Wen, Bo, et al.
(author)
-
IPeak : An open source tool to combine results from multiple MS/MS search engines
- 2015
-
In: Proteomics. - : Wiley-VCH Verlagsgesellschaft. - 1615-9853 .- 1615-9861. ; 15:17, s. 2916-2920
-
Journal article (peer-reviewed)abstract
- Liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) is an important technique for detecting peptides in proteomics studies. Here, we present an open source software tool, termed IPeak, a peptide identification pipeline that is designed to combine the Percolator post-processing algorithm and multi-search strategy to enhance the sensitivity of peptide identifications without compromising accuracy. IPeak provides a graphical user interface (GUI) as well as a command-line interface, which is implemented in JAVA and can work on all three major operating system platforms: Windows, Linux/Unix and OS X. IPeak has been designed to work with the mzIdentML standard from the Proteomics Standards Initiative (PSI) as an input and output, and also been fully integrated into the associated mzidLibrary project, providing access to the overall pipeline, as well as modules for calling Percolator on individual search engine result files. The integration thus enables IPeak (and Percolator) to be used in conjunction with any software packages implementing the mzIdentML data standard. IPeak is freely available and can be downloaded under an Apache 2.0 license at https://code.google.com/p/mzidentml-lib/.
|
|
| 11. |
- Zhou, Jinming, et al.
(author)
-
Comparative assessment of the surface integrity of AD730® and IN718 superalloys in high-speed turning with a CBN tool
- 2019
-
In: Journal of Manufacturing and Materials Processing. - : MDPI AG. - 2504-4494. ; 3:3
-
Journal article (peer-reviewed)abstract
- Nickel-based superalloys are typical materials used in components of aeroengines and gas turbine machinery. The strength properties of these alloys at high temperatures are crucial not only to the performance (e.g., power generation efficiency, energy consumption, and greenhouse gas emissions) of aeroengines and industrial gas turbines, but also to machinability during component manufacturing. This study comparatively evaluated the surface integrity of two superalloys, AD730® and Inconel 718 (IN718), during high-speed finishing turning using cubic boron nitride (CBN) tools. IN718 is a conventional superalloy used for the hot section components of aeroengines and industrial gas turbines, while AD730® is a novel superalloy with enhanced high-temperature mechanical properties and good potential as a next-generation superalloy for these components. High-speed turning tests of two superalloys were conducted using a CBN cutting tool and jet stream cooling. The achieved surface integrity of the AD730® and IN718 superalloys was characterized and analyzed to assess the comparability of these alloys.
|
|
