Cavity Filling (cavity + filling)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

3D computer simulation of melt flow and heat transfer in the lost foam casting process

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2003
S. M. H. Mirbagheri
Abstract A new mathematical model has been developed to simulate mould filling in the lost foam casting process, using the finite difference method. The simulation of molten flow and track of free surfaces is based on the SOLA-VOF numerical technique. An algorithm was developed to calculate the gas pressure of the evaporated foam during the mould filling. The effect of backpressure on the filling behaviour was modelled with an experimental function by adding three-dimensions 3DVOF functions. In order to verify the computational results, a thin grey iron plate was poured into a transparent mould. Cavity filling, foam depolymerization and gap formation were recorded with a 16mm high-speed camera. A good agreement was achieved for simulation results of filling sequences with those from experiments. Copyright © 2003 John Wiley & Sons, Ltd. [source]

GENSMAC3D: a numerical method for solving unsteady three-dimensional free surface flows

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2001
M.F. Tomé
Abstract A numerical method for solving three-dimensional free surface flows is presented. The technique is an extension of the GENSMAC code for calculating free surface flows in two dimensions. As in GENSMAC, the full Navier,Stokes equations are solved by a finite difference method; the fluid surface is represented by a piecewise linear surface composed of quadrilaterals and triangles containing marker particles on their vertices; the stress conditions on the free surface are accurately imposed; the conjugate gradient method is employed for solving the discrete Poisson equation arising from a velocity update; and an automatic time step routine is used for calculating the time step at every cycle. A program implementing these features has been interfaced with a solid modelling routine defining the flow domain. A user-friendly input data file is employed to allow almost any arbitrary three-dimensional shape to be described. The visualization of the results is performed using computer graphic structures such as phong shade, flat and parallel surfaces. Results demonstrating the applicability of this new technique for solving complex free surface flows, such as cavity filling and jet buckling, are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Cavity preparation using a superpulsed 9.6-,m CO2 laser,a histological investigation

LASERS IN SURGERY AND MEDICINE, Issue 5 2002
R. Müllejans
Abstract Background and Objectives The superpulsed 9.6-,m CO2 laser is an effective laser for ablating dental tissues and decay. This histological study compares laser class V preparations with conventional treatment to evaluate the resulting formation at the cavity walls. Study Design/Materials and Methods Four class V preparations (one made with a diamond drill and three with the CO2 laser (9.6 ,m, 60 microseconds pulse width, 40 mJ pulse energy, 100 Hz, integrated scanner system, water cooling) were performed on ten extracted teeth. The cavities were filled with a composite resin partly including enamel and dentine conditioning. Results After laser preparation, no cracks or signs of carbonisation were detected. The results were comparable to those attained with conventional treatment. Following cavity filling without prior conditioning, gaps were noted at the cavosurface indicating a lack of adhesion. Dentinal bonding decreased gap formation significantly. Conclusion The 9.6-,m CO2 laser is an effective tool for cavity preparation. Lasers Surg. Med. 30:331,336, 2002. © 2002 Wiley-Liss, Inc. [source]

Primary and secondary gas penetration during gas-assisted injection molding.

POLYMER ENGINEERING & SCIENCE, Issue 5 2004
Part I: Formulation, modeling
A theoretical study has been carried out on the transient gas-liquid interface development and gas penetration behavior during the cavity filling and gas packing stage in the gas-assisted injection molding (GAIM) of a tube cavity. A mathematical formulation describing the evolution of the gas/melt interface and the distribution of the residual wall thickness of skin melt along with the advancement of gas/melt front is presented. The physical model is put forward on the basis of Hele-Shaw approximation and interface kinematics and dynamics. Numerical simulation is implemented on a fixed mesh covering the entire cavity. The model and simulation can deal with both primary and secondary gas penetrations. The predicted and measuredresults are compared in Part II of this study to validate the theoretical model. Polym. Eng. Sci. 44:983,991, 2004. © 2004 Society of Plastics Engineers. [source]