Shot Sleeve Wave Dynamics in the Slow Phase of Die Casting Injection

2000 ◽  
Vol 122 (2) ◽  
pp. 349-356 ◽  
Author(s):  
J. Lo´pez ◽  
J. Herna´ndez ◽  
F. Faura ◽  
G. Trapaga
Keyword(s):  
Die Casting ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Slow Phase ◽  
Shot Sleeve ◽  
Viscous Effects ◽  
Filling Fraction ◽  
Wave Dynamics ◽  
Injection Process ◽  
Filling Time

An analysis is carried out on the wave formed during the slow phase of die casting injection processes. Viscous effects are assumed to be negligible and the problem is treated two-dimensionally using finite amplitude wave theory. Two commonly used types of plunger movements are considered, for which all the possible wave profiles are analyzed in depth as a function of the parameters which characterize the law of acceleration applied to the plunger, the initial shot sleeve filling fraction, and the geometrical characteristics of the problem. Different relationships between the relevant dimensionless parameters of the system are proposed, which make it possible to optimize the injection process, and so reduce the entrapment of air which leads to porosity. The validity of such relationships is analyzed in detail for different ranges of parameters. Some of the results obtained for the optimum acceleration are compared with those of other authors and experimental measurements. Finally, a law of plunger acceleration which would completely eliminate the air from the shot sleeve at the end of the slow phase of injection and minimizes the filling time is derived. [S0098-2202(00)02002-2]

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.

A Study of Wave Formation in Shot Sleeve of a Die Casting Machine

1994 ◽  
Vol 116 (2) ◽  
pp. 175-182 ◽  
Author(s):  
T. C. Tszeng ◽  
Y. L. Chu
Keyword(s):  
Wave Front ◽  
Die Casting ◽  
Casting Machine ◽  
Finite Amplitude ◽  
Wave Formation ◽  
Optimum Process ◽  
Shot Sleeve ◽  
Process Variables ◽  
Air Entrapment ◽  
Transient Wave

The objective of this study was to find the optimum process variables for minimizing the amount of air entrapped within the shot sleeve during the slow shot phase of the injection process. To achieve this objective, the relations between process variables (e.g., plunger speed/acceleration, initial filling percentage, sleeve diameter, etc.) and the wave formation within the shot sleeve of a die casting machine have to be determined. For this purpose, a mathematical model has been developed to study the transient wave formation in shot sleeve. The model based on the theory of waves of finite amplitude can predict the critical plunger speed and the profile of wave front, which in turn affect the degree of air entrapment. The optimum plunger speeds for minimum air entrapment are thus determined based on the predicted profile of wave front. Good agreement with the results from water analogue experiments is found.

A WEAKLY NONLINEAR INSTABILITY OF MISCIBLE DISPLACEMENTS IN A RECTILINEAR POROUS MEDIA FLOW

1994 ◽  
Vol 04 (05) ◽  
pp. 1319-1328 ◽  
Author(s):  
WILLIAM B. ZIMMERMAN
Keyword(s):  
Linear Theory ◽  
Landau Equation ◽  
Separation Of Variables ◽  
Finite Amplitude ◽  
Linear Stability Theory ◽  
Porous Media Flow ◽  
Perturbation Scheme ◽  
Viscous Effects ◽  
Regular Perturbation ◽  
Displacement Front

The linear stability theory of Tan & Homsy [1986] is extended to include the effects of weak nonlinear coupling between mass flux and viscous effects when the viscous fingers grow from a slowly diffusing, nearly flat displacement front. A regular perturbation scheme combined with a similarity-separation of variables technique leads to a Landau equation for the amplitude of the disturbance. The Landau constant has a simple pole for a given wavenumber within the linear theory cutoff wavenumber for growth. An argument is given that this pole leads to pairing of fingers while the instability remains small. Comparison of the length scale of the pole of the Landau constant with experimental measurements of finger scale shows good agreement where plausibly finite-amplitude effects might come into play, but with the linear theory otherwise.

Controlling and Minimizing Blistering during T6 Heat Treating of Semi-Solid Castings

2016 ◽  
Vol 256 ◽  
pp. 192-198 ◽  
Author(s):  
Hong Xing Lu ◽  
You Feng He ◽  
Stephen Midson ◽  
Da Quan Li ◽  
Qiang Zhu
Keyword(s):  
Solution Heat Treatment ◽  
Elevated Temperatures ◽  
Die Casting ◽  
Heat Treating ◽  
Pressure Casting ◽  
Shot Sleeve ◽  
Semi Solid ◽  
Entrapped Air ◽  
The Impact ◽  
Subsurface Defects

Surface blistering during T6 heat treating is an artifact that is essentially unique to high pressure casting processes such as semi-solid casting and die casting. It is believed that the blistering originates from subsurface defects present in the castings. When the castings are exposed to elevated temperatures during solution heat treatment, the strength of the aluminum is reduced, and the defects expand to deform the surfaces of the castings. There are three potential sources for the subsurface defects - entrapped air, die lubricant or shot sleeve lubricant.This paper will report on a study to determine the origin of the defects present in the castings that produce the blisters. Along with attempting to separate the influence of air and the two types of lubricants on blister formation, the study will also examine the impact of a number of process parameters on blistering.

Optimization of Trimaran Design Configuration in Calm and Deep Water

2020 ◽  
Author(s):  
Renato Skejic ◽  
Sverre A. Alterskjær
Keyword(s):  
Deep Water ◽  
Optimization Procedure ◽  
Wave Theory ◽  
Point Of View ◽  
Engineering Practice ◽  
Total Resistance ◽  
Operational Parameters ◽  
Viscous Effects ◽  
Greenhouse Gasses ◽  
Hard Particles

The field of sea based modern shipping activities is constantly seeking for its improvements to achieve the economically justified operational patterns. In the same time, the sea transportation activities also need to satisfy currently imposed and, as well as, upcoming in the near future, safety and ecologically friendly footprint characteristics when it comes to the emission of greenhouse gasses and hard particles [1]. Fulfilment of the stated requirements consequently asks for the determination of certain vessels operational parameters such as the total resistance of a vessel which estimation is frequently carried out for predefined calm and deep-water environmental scenario. Current work is dealing with investigation of the total resistance parameter in calm and deep water for the preselected types of the trimaran ship hull configurations. The total resistance is estimated according to [2] recommended procedure through applicability of the robust and reliable method which is capable to address the problem of wave resistance prediction in calm and deep water. The method has origin in ordinary and modified Michell thin – ship wave theory by considering the viscous effects [3]. The differences between the utilized theories are discussed from the qualitative and quantitative point of view of the obtained results in comparison to the open source available theoretical experimental data and from the perspective of common engineering practice. Finally, based on the above description, the performed total resistance studies are used as a base for formulation of the optimization procedure which may be used in the trimaran vessel preliminary designs in the range of the forward speeds commonly expected during the normal operational life of the investigated trimaran vessel.

scholarly journals The production of waves by the sudden release of a spherical distribution of compressed air in the atmosphere

1941 ◽  
Vol 178 (973) ◽  
pp. 153-170 ◽  
Keyword(s):  
Shock Wave ◽  
Sound Wave ◽  
Complete Solution ◽  
Spherical Wave ◽  
Three Dimensional ◽  
Wave Theory ◽  
Initial Distribution ◽  
Finite Amplitude ◽  
Compressed Air ◽  
Compressible Medium

An attempt has been made to develop a method for dealing with solutions of problems connected with the production of waves by spherical concentrations of compressed air. Starting from the general equations for three-dimensional spherically symmetrical flow in a homogeneous compressible medium having constant entropy everywhere, a process has been devised to apply step-by-step calculations over small intervals of time to investigate the general features of such a motion. A complete solution has been worked out in one particular case for a not very intense initial distribution of pressure, and various indirect checks have indicated that the results are reasonably accurate. These results show m any features of definite interest. As distinct from plane or spherical sound wave theory, it is found that a train of waves passes away from the centre of disturbance, the amplitudes and wave lengths falling off from wave to wave. Furthermore, as distinct from finite amplitude plane wave theory which shows that any wave must eventually become a shock wave, the waves obtained in the finite amplitude spherical wave case show no indication of becoming shock waves, and indeed show towards the closing stages of the calculation a similarity to sound wave propagation. The method is applicable to any spherically symmetrical motion up to such a time as the formation of a shock wave takes place and then fails owing to the assumption of constant entropy.

scholarly journals Gas Response to a Rotating Stellar Bar

1978 ◽  
Vol 3 (3) ◽  
pp. 234-236
Author(s):  
M. P. Schwarz
Keyword(s):  
Spiral Galaxies ◽  
Fast Rate ◽  
Density Wave ◽  
Wave Theory ◽  
Finite Amplitude ◽  
Spiral Waves ◽  
Galactic Rotation ◽  
Spiral Pattern ◽  
Density Wave Theory ◽  
Gas Response

The arms in spiral galaxies cannot be material arms for then they would wind up on a time scale of one galactic rotation, or a few times 108 years. The large number of spirals suggests that the spiral pattern must persist for about 1010 years (or be continually rejuvenated). The density wave theory treats the spiral pattern as a wave phenomenon, thus overcoming this problem. Much work has been done studying small amplitude oscillations in flat stellar discs. Self-consistent spiral modes have been found, but they are not stable and grow at a fast rate. Numerical simulations of thin stellar discs, such as those of Hohl (1971), which can handle finite amplitude waves, have been more successful. Spiral waves form initially but evolve into a steady state rotating bar. It seems therefore, that a long-lived spiral cannot be formed in stars alone.

Simulation Study on Wax Injection for Investment Casting

2013 ◽  
Vol 834-836 ◽  
pp. 1575-1579
Author(s):  
Bo He ◽  
Dong Hong Wang ◽  
Fei Li ◽  
Bao De Sun
Keyword(s):  
Numerical Simulation ◽  
Mold Design ◽  
Trial And Error ◽  
Efficient Tool ◽  
Injection Process ◽  
Wax Pattern ◽  
Filling Time ◽  
Gate System ◽  
The Cost ◽  
Wax Injection

As investment castings grow in size and complexity, control of wax pattern dimensions becomes increasingly important and difficult. Conventionally, mold design and dimensions are re-worked by trial-and-error procedures until casting dimensions are produced within acceptable dimensional tolerances, increasing the cost of the castings.Nowadays, numerical simulation is an efficient tool for mold design. However, one of the critical difficulties in using computer models for the simulation of wax injection process is the lack of material properties of the wax. Material property measurements were conducted in this study that can be used as input in Moldflow. Then, 3D numerical simulation could be applied in analysis with mold design of thin-walled wax pattern, with high dependability. Simulation results of filling time and the location of the air traps were analyzed. Consequently, best gate location and reasonable gate system were determined. The paper highlighted the effectiveness of simulation in filling optimization and deformation of wax pattern.

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