Influence of Unsteady Effects on Air Venting in Pressure Die Casting

2001 ◽  
Vol 123 (4) ◽  
pp. 884-892 ◽  
Author(s):  
J. Herna´ndez ◽  
J. Lo´pez ◽  
F. Faura
Keyword(s):  
Method Of Characteristics ◽  
Die Casting ◽  
Operating Conditions ◽  
Filling Process ◽  
Air Mass ◽  
One Dimensional ◽  
Trapped Air ◽  
Unsteady Effects ◽  
Pressure Die Casting ◽  
Selection Of

The influence of unsteady effects on the evacuation of air through vents in pressure die casting processes is analyzed. A model is proposed which considers the air flow as one-dimensional and adiabatic, and which retains friction effects. Venting conditions for wide ranges of the relevant dimensionless parameters are analyzed for both atmospheric and vacuum venting systems. The model is solved numerically using the method of characteristics and its results are compared with those obtained for quasi-steady models. It is shown that wide ranges of operating conditions can exist in practical situations, for which unsteady effects, neglected in previous models, are important and must be taken into account to determine the air mass entrapped at the end of the filling process. The selection of parameters which will reduce the amount of trapped air and thus porosity in manufactured parts is also discussed.

scholarly journals Direct Observation of Filling Process and Porosity Prediction in High Pressure Die Casting

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1099 ◽  
Author(s):  
Hanxue Cao ◽  
Chao Shen ◽  
Chengcheng Wang ◽  
Hui Xu ◽  
Juanjuan Zhu
Keyword(s):  
Numerical Simulation ◽  
High Pressure ◽  
Flow Visualization ◽  
Flow Pattern ◽  
Experimental Verification ◽  
Die Casting ◽  
Filling Process ◽  
High Pressure Die Casting ◽  
Visualization Experiment ◽  
Pressure Die Casting

Although numerical simulation accuracy makes progress rapidly, it is in an insufficient phase because of complicated phenomena of the filling process and difficulty of experimental verification in high pressure die casting (HPDC), especially in thin-wall complex die-castings. Therefore, in this paper, a flow visualization experiment is conducted, and the porosity at different locations is predicted under three different fast shot velocities. The differences in flow pattern between the actual filling process and the numerical simulation are compared. It shows that the flow visualization experiment can directly observe the actual and real-time filling process and could be an effective experimental verification method for the accuracy of the flow simulation model in HPDC. Moreover, significant differences start to appear in the flow pattern between the actual experiment and the Anycasting solution after the fragment or atomization formation. Finally, the fast shot velocity would determine the position at which the back flow meets the incoming flow. The junction of two streams of fluid would create more porosity than the other location. There is a transition in flow patterns due to drag crisis under high fast shot velocity around two staggered cylinders, which resulted in the porosity relationship also changing from R1 < R3 < R2 (0.88 m/s) to R1 < R2 < R3 (1.59 and 2.34 m/s).

Analysis of the Flow in a High-Pressure Die Casting Injection Chamber

2003 ◽  
Vol 125 (2) ◽  
pp. 315-324 ◽  
Author(s):  
J. Herna´ndez ◽  
J. Lo´pez ◽  
F. Faura ◽  
P. Go´mez
Keyword(s):  
Shallow Water ◽  
Die Casting ◽  
Operating Conditions ◽  
Water Model ◽  
Accurate Estimation ◽  
Viscous Effects ◽  
Filling Fraction ◽  
Filling Time ◽  
Entrapped Air ◽  
Pressure Die Casting

The flow in the injection chamber of pressure die casting machines is analyzed using a model based on the shallow-water approximation which takes into account the effects of wave reflection against the end wall of the chamber. The governing equations are solved numerically using the method of characteristics and a finite difference grid based on the inverse marching method. The results of the model for wave profiles, volume of air remaining in the injection chamber at the instant at which the molten metal reaches the gate to the die cavity, and optimum values of the parameters characterizing the law of plunger motion, are compared with the numerical results obtained from a finite element code, which solves the two-dimensional momentum and mass conservation equations, taking into account nonhydrostatic and viscous effects. We found that, although the shallow-water model does not provide a very accurate estimation of the mass of entrapped air in the injection chamber for certain ranges of working conditions, it does describe reasonably well the influence of the acceleration parameters and the initial filling fraction on the entrapped air mass, and can be of help in selecting operating conditions that reduce air entrapment while keeping the injection chamber filling time as low as possible.

Application of a Novel Entrainment Defect Model to a High Pressure Die Casting

2014 ◽  
Vol 922 ◽  
pp. 801-806
Author(s):  
Robert Watson ◽  
Tayeb Zeguer ◽  
Simon Ruffle ◽  
William D. Griffiths
Keyword(s):  
High Pressure ◽  
Surface Film ◽  
Die Casting ◽  
Weibull Statistics ◽  
High Pressure Die Casting ◽  
Trapped Air ◽  
Mould Filling ◽  
Computational Fluid Dynamics Cfd ◽  
Die Castings ◽  
Pressure Die Casting

Aluminium High Pressure Die Castings are economical to produce in high volumes. However, as greater structural demands are placed on such castings, a more detailed understanding is required of the defects which limit their strength. The process is prone to high levels of surface turbulence and fluid break-up, resulting in the entrainment of air into the liquid metal, which may manifest as trapped air porosity or bifilm defects in the finished part. A novel algorithm was developed and integrated into a commercial computational fluid dynamics (CFD) package, to model mould filling, and the formation and transport of such entrainment defects. A commercial High Pressure Die Casting was simulated using this algorithm, to illustrate its application. Castings were also produced, and the results of tensile testing were summarised in the form of Weibull statistics. It was found that where the algorithm predicted a greater quantity of entrained surface film, a reduction in UTS of about 10% was also observed.

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.

Numerical Simulation and Optimization of Low Pressure Die Casting of Aluminum Alloy Cylinder Block

2014 ◽  
Vol 1004-1005 ◽  
pp. 1172-1177 ◽  
Author(s):  
Ai Min Du ◽  
Na Wei ◽  
Zhong Pan Zhu ◽  
Kan Zhou
Keyword(s):  
Die Casting ◽  
Casting Process ◽  
Mold Filling ◽  
Shrinkage Porosity ◽  
Cylinder Block ◽  
Filling Process ◽  
Simulation And Optimization ◽  
Sand Core ◽  
Low Pressure Die Casting ◽  
Pressure Die Casting

Cylinder block with different design structures will affect casting process and final product quality in various degrees. In this paper, mold filling and solidifying process of a cylinder block was simulated with Procast software and the results show that there are several casting defects caused by the self-structure. In order to improve such a situation, we adjusted the bottom structure and thick parts on the basis of original cylinder. After analyzing the results of simulation, the optimized cylinder has better mold filling process, less impacts on the sand core and less shrinkage porosity during the solidifying process.

Comparative Analysis of HPDC Process of an Auto Part with ProCAST and FLOW-3D

2012 ◽  
Vol 184-185 ◽  
pp. 90-94 ◽  
Author(s):  
Hui Zhen Duan ◽  
Jiang Nan Shen ◽  
Yan Ping Li
Keyword(s):  
High Pressure ◽  
Aluminum Alloy ◽  
Technological Parameter ◽  
Die Casting ◽  
Filling Process ◽  
Software Simulation ◽  
Auto Part ◽  
The Difference ◽  
3D Software ◽  
Pressure Die Casting

The high pressure die casting (HPDC) process of an ADC12 aluminum alloy auto part is researched by the software ProCAST and FLOW-3D, respectively. The possible HPDC defects of the auto part are analyzed. The difference of the filling process with the same technological parameter is studied. Compared with the simulation result of ProCAST, FLOW-3D software simulation result is closer to the die casting of the actual production.

Modeling of Air Venting in Pressure Die Casting Process

2004 ◽  
Vol 126 (3) ◽  
pp. 577-581 ◽  
Author(s):  
A. Nouri-Borujerdi ◽  
J. A. Goldak
Keyword(s):  
Friction Factor ◽  
Die Casting ◽  
Casting Process ◽  
Area Ratio ◽  
Air Pressure ◽  
Temperature Dependent Viscosity ◽  
Air Mass ◽  
Choked Flow ◽  
Dependent Viscosity ◽  
Pressure Die Casting

In this study an analytical model has been developed to describe air pressure and residual air mass variations in pressure die casting for atmospheric venting. During injection of molten metal into a die cavity, air is evacuated from the cavity through vents. In this study, the influences of air velocity and friction factor due to temperature dependent viscosity and vent roughness change have been investigated. The results of the model show that there is a critical area ratio over which a quasi steady state is reached, therefore, the air pressure in the cavity remains constant. In addition, for each area ratio there is a critical/minimum time ratio below which outlet Mach number is not large enough to create choked flow. In this case, the rate of outflow air mass is not maximum. Finally, the results of the model addresses that the friction factor depends on hydraulic diameter of the vent and assuming a constant value for it is not valid.

scholarly journals Unsteady Effects on NOx Measurements in Pulse Detonation Combustion

2021 ◽  
Author(s):  
Niclas Hanraths ◽  
Myles D. Bohon ◽  
Christian Oliver Paschereit ◽  
Neda Djordjevic
Keyword(s):  
Sampling Technique ◽  
Extraction Process ◽  
Operating Conditions ◽  
Exhaust Gas ◽  
One Dimensional ◽  
Pulse Detonation ◽  
Detonation Combustion ◽  
Unsteady Effects ◽  
Sample Time ◽  
Probe Geometry

AbstractEmission measurements from unsteady combustion systems such as Pulse Detonation Combustion (PDC) are challenging due to the inherently large variations in pressure, temperature, composition, and flow velocity of the exhaust gas. Comparison of experimental data is additionally complicated by differences in operating conditions and gas sampling setup between different facilities. Qualitative considerations with regard to the sampling process from PDC, based on one-dimensional simulations, indicate a systematic influence of the sampling setup and extraction process on the resulting concentration measurements. Therefore, operating frequency, sample time, fill time, as well as PDC outlet and probe geometry were varied experimentally in order to assess the degree to which each of these parameters impact the resulting measured $${\rm NO}_{\rm x}$$ NO x in order to better inform researchers of these effects when making measurements. It was shown that measured $${\rm NO}_{\rm x}$$ NO x emissions can vary significantly depending on the choice of these parameters and therefore care must be exercised in order to reduce the influence of the sampling technique when aiming for comparable results.

Modelling the pressure die casting process with the boundary element method: Die deformation model for flash prevention

1998 ◽  
Vol 212 (3) ◽  
pp. 197-215 ◽  
Author(s):  
J Milroy ◽  
S Hinduja ◽  
K Davey
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Die Casting ◽  
Injection Pressure ◽  
Casting Process ◽  
Operating Conditions ◽  
Deformation Model ◽  
The Individual ◽  
Pressure Die Casting ◽  
Element Method

In pressure die casting, the thermal loads, injection pressure and clamping forces cause the individual blocks of a die to deform. This deformation results in gaps between the interface surfaces which, if big enough and in the vicinity of the cavity, permit material to seep into the gaps, causing flash. This paper describes a thermoelastic model to predict the deformation of the die so that it can be machined to prevent flash. The model is based on the boundary element method and allows the use of linear isoparametric or quadratic subparametric elements. Each die block is analysed as a separate problem. To avoid the occurrence of flash, the model suggests the amounts that should be machined from each die block. The predicted deformation has been experimentally verified by measuring the profile of a test die using displacement transducers and die impressions. It is shown that there is good agreement between the predicted and experimental results for different operating conditions. By machining the amounts suggested by the model, the test die was run without flash at operating conditions that had previously resulted in flash.

scholarly journals Effect of parameters of high-pressure die casting on occurrence of casting nonconformities in sleeves of silumin alloy EN AB 47100

2017 ◽  
Vol 62 (1) ◽  
pp. 373-378
Author(s):  
Ł. Pałyga ◽  
M. Stachowicz ◽  
K. Granat
Keyword(s):  
High Pressure ◽  
Die Casting ◽  
Casting Machine ◽  
Pressure Casting ◽  
High Pressure Die Casting ◽  
Closing Force ◽  
Working Parameters ◽  
Shrinkage Cavities ◽  
Pressure Die Casting ◽  
Selection Of

Abstract The paper presents a research on the effect of extreme - for the technology of the considered silumin EN AB 47100 - parameters of high-pressure die casting on occurrence of casting nonconformities. Considered was influence of the way of assembling the mould cooled-down to 140-160°C, non-standard for the selected casting, and pouring temperature in the range of 705 to 720°C (higher than the recommended) of non-refined alloy. The castings were prepared with use of a high-pressure casting machine made by Kirov with mould closing force of 2500 kN. Occurrence of nonconformities was evaluated on properly prepared specimens taken from the castings manufactured with various parameters of the injection piston and various multiplication pressures. The results were subjected to quantitative and qualitative analyses of casting nonconformities and distribution of major alloying elements. It was found that proper selection of working parameters of the casting machine, in spite of disadvantageous pouring conditions, makes it possible to reduce occurrence of some casting defects, like shrinkage cavities and porosity, to improve tightness of castings even when the alloy refining process is omitted.

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