Experimental investigation on the flow behavior of liquid aluminum inside pressure-die-casting dies using high-speed photography

1991 ◽  
Author(s):  
Xuping Jiang ◽  
Guobin Wu
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Flow Behavior ◽  
Die Casting ◽  
Liquid Aluminum ◽  
High Speed Photography ◽  
Pressure Die Casting

Melt Quality Assessment

2019 ◽  
Author(s):  
Derya Dispinar
Keyword(s):  
Aluminum Oxide ◽  
Die Casting ◽  
Liquid Aluminum ◽  
Hydrogen Gas ◽  
Optimized Design ◽  
Hydrogen Atoms ◽  
Reduced Pressure ◽  
Cast Part ◽  
Crystalline Oxide ◽  
Pressure Die Casting

It is well known that the reaction of liquid aluminum with the moisture in the environment results in two products: aluminum oxide and hydrogen gas that dissolves in aluminum. Both of these products are considered to be detrimental to the properties of aluminum alloys. Therefore, test equipment has been developed to check the levels of these defects in the melt. Many of these involve expensive and consumable tools. In addition, an experienced personnel may be required to interpret the results. Nonetheless, aluminum oxide is harmless as long as it remains on the surface. The problem begins when this oxide is entrained into the liquid aluminum such as turbulence during transfer or mold filling in a non-optimized design. This can only happen by folding of the oxide. During this action, rough surface of the oxides comes in contact to form no bonds. These defects are known as bifilms that have certain characteristics. First, they act as cracks in the cast parts since they are oxides. It is important to note that aluminum oxide has thin amorphous oxide (known as young oxides) and thick crystalline oxide (γ-Al2O3) that may be formed in a casting operation. Second, almost zero force is required to open these bifilms due to the unbonded folded oxide skins. Thus, these defects can easily form porosity by unravelling during solidification shrinkage. On the other hand, the formation of porosity by hydrogen is practically impossible. Theoretically, hydrogen has high solubility in the liquid but it has significantly low solubility in solid aluminum. Thus, it is suspected that hydrogen is rejected from the solidification front to form hydrogen gas and porosity. However, the hydrogen atom has the smallest atomic radii and high diffusibility. Therefore, segregation of hydrogen in front of the growing solid is difficult. In addition, the energy required for hydrogen atoms to segregate and form hydrogen gas molecule is around 30,000 atm. Under these conditions, porosity formation by hydrogen is not likely to be achieved. Hydrogen probably stays in a supersaturated state or diffuses homogeneously through the cast part. The effect of hydrogen can only be seen when it can diffuse into the unbonded gap between the bifilms to open them up to aid the unravelling of bifilms to form porosity. This phenomenon can be easily detected by a very simple test called reduced pressure test. When a sample is solidified under vacuum, the bifilms start to open up. Since all porosity is formed by bifilms, the cross section of the sample solidified under vacuum can be analyzed by means of image analysis software. The sum of maximum length of pores can be measured as an indication of melt quality. Since bifilms are the most detrimental defects, this value is called “bifilm index” given in millimetres, which makes this test the only test that can quantify aluminum melt quality in such detail including both the effects of bifilms and hydrogen together. Several Al-Si alloys were used at various conditions: degassing with lance, ceramic diffusers, and graphite rotary has been compared. Gravity sand casting, die casting, and low-pressure die casting methods were evaluated. The effect of grain refiners and modifiers was studied. And the evolution of the bifilm index has been presented.

Experimental Investigation on Flow Field in a Rotating Channel With a New TR-PIV System

2018 ◽  
Author(s):  
Shengjun Zhou ◽  
Haiwang Li ◽  
Zhi Tao ◽  
Ruquan You ◽  
Haoyu Duan
Keyword(s):  
Boundary Layer ◽  
Experimental Investigation ◽  
Laser Diode ◽  
High Speed ◽  
Flow Behavior ◽  
Particle Image Velocimetry System ◽  
Main Stream ◽  
High Speed Camera ◽  
Time Resolved ◽  
Rotating Channel

In the current study, the influence of different rotation conditions on the flow behavior is experimentally investigated by a new system which is designed for time-resolved PIV measurements of the smooth channels at rotation conditions. The Reynolds number equals 15000 and the rotation number ranges from 0 to 0.392 with an interval of 0.098. This new time-resolved Particle Image Velocimetry system consists of a 10 Watts continuous laser diode and a high-speed camera. The laser diode can provide a less than 1mm thickness sheet light. 6400 frames can be captured in one second by the high-speed camera. These two parts of the system are fixed on a rotating disk. In this case, the relative velocity of flows in the rotating smooth square channel can be measured directly to reduce the measurement error. This system makes high-speed camera close to the rotating channel, which allows a high resolution for the measurements of main stream. In addition, high accuracy and temporal resolution realize a detailed analysis of boundary layer characteristics in rotation conditions. Based on this system, experimental investigation has been undertaken. Results are presented of the evolution of velocity and boundary layer thickness at various rotation numbers and different circumferential positions.

CFD Multiphase Flow Modelling of Air Porosity Defect Formation During High-Pressure Die-Casting Filling Process

2015 ◽  
Author(s):  
J. Hao ◽  
Y. J. Lin ◽  
Y. Nie
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
High Speed ◽  
Flow Model ◽  
Defect Formation ◽  
Die Casting ◽  
Phase Flow ◽  
Filling Process ◽  
Proposed Model ◽  
Pressure Die Casting

High-Pressure Die-Casting (HPDC) is an important process for manufacturing high-volume and low-cost components. In this process molten metal is injected at high speed under high pressure into the die cavity, which often leads to entrapment of air into the liquid metal. This will cause air porosity after solidification, the main defect in the parts made by HPDC. The aim of this work was to develop a CFD multiphase flow simulation method to numerically study the air porosity defect formation in HPDC. Some numerical models have been developed to predict the air porosity defect in HPDC. However, most of them are limited to one phase flow model which could only simulate the filling process of liquid metal. In this study both the bulk fluid and surrounding air were modeled by a 3D multiphase flow model. The proposed model can describe the entrapment, advection and coalescence of air bubbles within the melt, and thus has the ability to accurately simulate the air porosity defect formation in HPDC. In the present paper, an incompressible-compressible two-phase flow model was developed. The numerical benchmark test of a broken dam problem was used to demonstrate the effectiveness of the proposed model. Then numerical model was applied to simulate a high speed water filling process. Results of the modeling were compared with corresponding experimental data and good agreement has been found.

Experimental Investigation of the Characteristics of Dynamic Cutting Process

1977 ◽  
Vol 99 (2) ◽  
pp. 410-418 ◽  
Author(s):  
M. M. Nigm ◽  
M. M. Sadek
Keyword(s):  
Experimental Investigation ◽  
Theoretical Model ◽  
High Speed ◽  
Cutting Speed ◽  
Chip Thickness ◽  
Shear Plane ◽  
Rake Angle ◽  
Experimental Results ◽  
High Speed Photography ◽  
Cutting Coefficients

The dynamic response of the shear plane and the variations of the dynamic cutting coefficients are experimentally investigated at various values of feed, cutting speed, rake angle, clearance angle, frequency, and amplitude of chip thickness modulation. Wave generating and wave removing cutting tests, in which high-speed photography is used to investigate the geometry of chip formation, are carried out. The theoretical model of dynamic cutting developed in [1] is assessed with reference to these experimental results. A comparison between this model and previous models in relation to the experimental results is also presented.

Experimental Study on Jet Breakup Morphologies and Jet Characteristic Parameters of Non-circular Nozzles under Low-intermediate Pressures

2019 ◽  
Vol 35 (4) ◽  
pp. 617-632
Author(s):  
Yue Jiang ◽  
Hong Li ◽  
Lin Hua ◽  
Daming Zhang ◽  
Zakaria Issaka
Keyword(s):  
Surface Wave ◽  
High Speed ◽  
Flow Behavior ◽  
Initial Section ◽  
Droplet Formation ◽  
High Speed Photography ◽  
Breakup Length ◽  
Jet Breakup ◽  
Circular Jets ◽  
Pressure Water

Abstract. A High-Speed Photography (HSP) technique was used to investigate the breakup process and flow behavior of low-intermediate pressure water jets issued from square and triangular shaped nozzles. The non-circular orifices were designed based on the principle of equal flowrate with the same pressure in relation to the circular orifice. The breakup morphologies and boundary structures of the jets were studied under different nozzles and working pressures. Two forms of droplet formation and the process of droplet formation, in addition to the jet breakup lengths, initial amplitudes of surface waves and jet diffusion angles of different nozzles were evaluated. It was found that the jet presented a good continuity and fluidity in the initial section, and the fluid bands gradually appeared due to the air resistance and the jet break up as the disturbance intensifies. The degree of jet breakup was enhanced with the increase of pressure and cone nozzle angle. The random appearance of the fluid band structures and the dactylitic textures near the nozzles for non-circular jets appeared earlier than those produced by the circular jets. The small satellite droplets with different shapes and sizes were seen inside and outside the jet interface. Triangular jets exhibited the shortest breakup length, the initial amplitude of surface wave, and the diffusion angle of the jet at the same pressure were largest compared with square and circular jets. Two index equations of jet characteristic lengths and equivalent diameters of both circular and non-circular nozzles were fitted with a relative error of less than 10%, which means the fitting formulas are accurate. Keywords: Breakup length, High-speed photography, MATLAB simulation, Non-circular nozzle, Surface wave amplitude.

Experimental investigation of multiphase flow behavior in drilling annuli using high speed visualization technique

2018 ◽  
Vol 14 (3) ◽  
pp. 635-643 ◽  
Author(s):  
Alap Ali Zahid ◽  
Syed Raza ur Rehman ◽  
S. Rushd ◽  
Anwarul Hasan ◽  
Mohammad Azizur Rahman
Keyword(s):  
Experimental Investigation ◽  
Multiphase Flow ◽  
High Speed ◽  
Flow Behavior ◽  
Visualization Technique
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