Computational model of the lost foam casting process

One of the partners to share costs, General Motors, Inc, released their achievements research2,3 development of physical and computational model of the lost foam casting process. Using data generated in previous research Consortium Foam Lost as well as research early by different authors, was explained conflicting results a lot by allowing stock to decompose in four modes unique: Method of contact, method of gap, drop method, engulf mode.

Various methods to create a wide range of behaviors observed. Contact method is needed and uses the undercut in the pattern formation during heating the metal to solve the dilemma amount of heat flux / gap mentioned above. Gap mode (Figure 1.1.4) due to excess polymer liquid (coating route is saturated by the escape mechanism) vaporizing behind the metal front. It occurs more often in patterns with thick sections which when they decompose in contact mode create a more liquid than able to absorb pattern. This vaporizes the liquid behind the metal front, bubbles rise through the liquid metal to form a finite gap for other higher initial flow up pattern forming. Also this front, the foam decomposes to melt and not the liquid absorbing polymer coating.

Collapse method has caused foam “fissures” between-bead porosity connecting pattern on the coated surface. Beads fall within the fissure with air exhausted by coating with liquid metal filling the fissure to form a “finger”. A top engulf method viscosity liquid foam affects the initial shape of the metal flow. It is characterized by unsteady, pulsating foam encirclement of the metal appears to “chew” their way through the foam. This creates huge bubbles filled with air, liquid polymer, and steam. The experimental apparatus was developed to undercut feature in touch mode validation. With the apparatus, coated foam pattern surrounded by sand band, simulated the situation the lost foam casting process was immersed in liquid melt and then quenched in a tank of water right after the immersion. The shutdown was expected on the remaining light on the interface metal / pattern preservation. The interfaces were examined under a stereo microscope metal foam. Undercut coating was observed using this method.

At the interface of metal foam, undercut gap established between the coating and pattern to shield larger area to provide use of gaseous pyrolysis products generated during the replacement metal / pattern. Measurements of such undercut profile coating width and length. The projected value of the model in general agreement with the measured value.

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