Pitting Corrosion of Natural Aged Al–Mg–Si Extrusion Profile

With the quick development of the high-speed railway and the service of the China Railway High-speed (CRH) series for almost a decade, one of the greatest challenges is the management/maintenance of these trains in environmental conditions. It is critical to estimate pitting damage initiation and accumulation and set up a corresponding database in order to support the foundations for interactive corrosion risk management. In this work, the pitting corrosion of a nature-aged commercial 6005A-T6 aluminum extrusion profile for 200 days was studied comprehensively. The heterogeneous microstructures were conventionally identified by the in situ eddy current, suggesting which investigated regions to fabricate samples for. After constant immersion for 240 h in 3.5 wt % NaCl, the shapes and depths of the pits were captured and measured by optical microscope (OM) and three-dimensional optical profilometry (OP), providing detailed quantification of uniform pitting corrosion. The typical features of the pits dominated by the distribution of precipitates include the peripheral dissolution of the Al matrix, channeling corrosion, intergranular attack, and large pits in the grains. Due to the high density of continuous anodic and cathodic particles constituted by alloying elements in coarse grains, the number of pits in the coarse grains was the highest while the number in the fine grains was the lowest, indicating that fine grains have the best corrosion resistance. The experimental dataset of the pit depth integrated with its corresponding microstructure would set the benchmark for further modeling of the pit depth and the remaining ductility, in order to manage the damage tolerance of the materials.

Download Full-text

Study on Magnetic Barrel Machine Equipped with Three-Dimensional Arrangement of Magnets

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.329.761 ◽

2007 ◽

Vol 329 ◽

pp. 761-766 ◽

Cited By ~ 1

Author(s):

Y. Zhang ◽

Masato Yoshioka ◽

Shin-Ichiro Hira

Keyword(s):

High Speed ◽

Permanent Magnets ◽

Three Dimensional ◽

Video Camera ◽

High Speed Video ◽

High Speed Video Camera ◽

The Media ◽

Set Up

At present, a commercially available magnetic barrel machine equipped with permanent magnets has some faults arising from constructional reason. That is, grinding or finishing ability is different from place to place in the machining region, resulting in the limitation on the region we can use in the container of workpieces. Therefore, in this research, authors made the new magnetic barrel machine equipped with three dimensional (3D) magnet arrangement to overcome these faults. The grinding ability of the new 3D magnetic barrel machine converted was experimentally examined, and compared with that of the traditional magnetic barrel machine. As a result, it was shown that we can use much broader region in the new 3D machine. It was also shown that the grinding ability became higher. The distribution of barrel media in action was recorded by means of a high speed video camera. It was clarified that the media rose up higher and were distributed more uniformly in the container by the effect of the magnet block newly set up. It was supposed that this must be the reason for the above-mentioned improvement of grinding ability.

Download Full-text

A New Sand Casting Process with Accelerated Solidification Rate

Materials Science Forum ◽

10.4028/www.scientific.net/msf.686.765 ◽

2011 ◽

Vol 686 ◽

pp. 765-769 ◽

Cited By ~ 3

Author(s):

Jian Min Zeng ◽

Yao He Zhou

Keyword(s):

High Speed ◽

Solidification Rate ◽

Convective Heat Exchange ◽

Casting Process ◽

Mold Filling ◽

Optical Microscope ◽

Sand Casting ◽

Aluminum Castings ◽

Coarse Grains ◽

Upper Chamber

In order to solve the problems involved in coarse grains, macro and micro porosities initiated by low solidification rate in sand casting, an innovative counter-gravity sand casting process, Casing under Adjustable Pressure with Accelerated Solidification (CAPAS) was put forward in this paper. The hydrodynamics of mold filling for CAPAS is based on Bernoulli's principle. The mold and crucible were placed separately in the upper and lower chambers, with the feed tube connected between them. High-speed jet flow of air made negative pressure in the upper chamber. In this way, pressure differential was created between the two chambers. Thereby the molten metal in the crucible was forced to flow upward smoothly to fill the mold cavity. After mold filling, cold air was introduced into sand mold through aisles that are set within the mold, which results in strong convective heat exchange at the casting/mold interface. So solidification rate of casting increased dramatically. The microstructures of the aluminum castings were compared between CAP (Low pressure sand casting) and CAPAS by optical microscope. The results showed that the microstructure of CAPAS aluminum casting was much finer than that of CAP casting and tensile strength markedly increased.

Download Full-text

Heat transfer mechanisms of a vapour bubble growing at a wall in saturated upward flow

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.174 ◽

2015 ◽

Vol 771 ◽

pp. 264-302 ◽

Cited By ~ 16

Author(s):

C. H. M. Baltis ◽

C. W. M. van der Geld

Keyword(s):

Heat Transfer ◽

High Speed ◽

Three Dimensional ◽

Plane Wall ◽

Bulk Liquid ◽

Vapour Bubble ◽

Contour Analysis ◽

Set Up ◽

Dry Spot ◽

Transfer Mechanisms

The aim of this study is to provide a better insight into the heat transfer mechanisms involved in single bubble growth in forced convection. In a set-up with vertical upflow of demineralized water under saturation conditions special bubble generators (BGs) were embedded at various positions in the plane wall. Power to a BG, local mean wall temperature and high-speed camera recordings from two viewing angles were measured synchronously. An accurate contour analysis is applied to reconstruct the instantaneous three-dimensional bubble volume. Interface topology changes of a vapour bubble growing at a plane wall have been found to be dictated by the rapid growth and by fluctuations in pressure, velocity and temperature in the approaching fluid flow. The camera images have shown a clear dry spot under the bubbles on the heater surface. A micro-layer under the bubble is experimentally shown to exist when the bubble pins to the wall surface and is therefore dependent on roughness and homogeneity of the wall. The ratio of heat extracted from the wall to the total heat required for evaporation was found to be around 30 % at most and to be independent of the bulk liquid flow rate and heat provided by the wall. When the bulk liquid is locally superheated this ratio was found to decrease to 20 %. Heat transfer to the bubble is also initially controlled by diffusion and is unaffected by the convection of the bulk liquid.

Download Full-text

Numerical Study on the Running Safety of High-Speed Train under the Cross Wind

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.694.109 ◽

2014 ◽

Vol 694 ◽

pp. 109-113

Author(s):

Xiang Dong Chen ◽

Yu Gong Xu

Keyword(s):

High Speed ◽

Numerical Study ◽

Three Dimensional ◽

Reduction Rate ◽

Aerodynamic Characteristics ◽

High Speed Train ◽

Wheel Load ◽

The Cross ◽

Set Up ◽

Train Safety

With the increasing speed, the crosswind effect is the more and more obvious. The three dimensional aerodynamic model of the high-speed train was set up to study the aerodynamic characteristics of the train under the cross wind. Based on the vehicle system dynamics, the couple model for dynamics of wind-train-rail systems was set up to study the train safety under the wind load. The derailment coefficient and reduction rate of wheel load were analyzed under the different train speed, different wind velocity. The results of this research can provide a theoretical basis for the high-speed train safety.

Download Full-text

Rigid-Flexible Virtual Prototyping Study of Planetary Gear Reducer for Shearer Cutting Unit

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.145.414 ◽

2010 ◽

Vol 145 ◽

pp. 414-419

Author(s):

Ke Bin Zhang ◽

Zhao Jian Yang ◽

Wei Bo Zhu

Keyword(s):

High Speed ◽

Large Scale ◽

Three Dimensional ◽

Planetary Gear ◽

Prototype Model ◽

Flexible Body ◽

Rigid Body Model ◽

Planet Gear ◽

Set Up ◽

Cutting Unit

In this research, three-dimensional simplified model for the planetary gear reducer of a certain large-scale shearer cutting unit is established by the use of UG NX5, and it is imported into ADAMS/View environment through the UG interface with ADAMS. While ANSYS is used to generate the flexible body of key parts such as sun gear, high-speed planet gear and low-speed planet gear, and then in ADAMS the flexible body is used to replace the corresponding parts of planetary reducer rigid body model, which aims to set up virtual rigid-flexible prototype model of planetary reducer. Finally, kinematics simulation was done. The simulation results show that the virtual prototype model of each component motion displays smooth without interference and the transmission ratio meets the design request. Meanwhile, the planetary gear mechanism design is proved to be very correct.

Download Full-text

High-speed brightfield 3-D imaging and 3-D image analysis of thick and overlapped cell clusters in cytological preparations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168827 ◽

1994 ◽

Vol 52 ◽

pp. 218-219

Author(s):

Robert W. Mackin

Keyword(s):

Image Analysis ◽

High Speed ◽

Three Dimensional ◽

Image Data ◽

Ccd Camera ◽

Objective Lens ◽

Array Processor ◽

Vaginal Smears ◽

Low Contrast ◽

Computer Controlled

This paper presents two advances towards the automated three-dimensional (3-D) analysis of thick and heavily-overlapped regions in cytological preparations such as cervical/vaginal smears. First, a high speed 3-D brightfield microscope has been developed, allowing the acquisition of image data at speeds approaching 30 optical slices per second. Second, algorithms have been developed to detect and segment nuclei in spite of the extremely high image variability and low contrast typical of such regions. The analysis of such regions is inherently a 3-D problem that cannot be solved reliably with conventional 2-D imaging and image analysis methods.High-Speed 3-D imaging of the specimen is accomplished by moving the specimen axially relative to the objective lens of a standard microscope (Zeiss) at a speed of 30 steps per second, where the stepsize is adjustable from 0.2 - 5μm. The specimen is mounted on a computer-controlled, piezoelectric microstage (Burleigh PZS-100, 68/μm displacement). At each step, an optical slice is acquired using a CCD camera (SONY XC-11/71 IP, Dalsa CA-D1-0256, and CA-D2-0512 have been used) connected to a 4-node array processor system based on the Intel i860 chip.

Download Full-text