Printing Free-Form Free-Standing Glass Structures

Transparent, bubble-free glass structures can be printed using a filament-fed, laser-heated additive manufacturing process. In this process, a stationary CO2 laser beam is focused at the intersection of the filament and workpiece to locally heat the glass above its working temperature. Glass enters the molten region and is deposited on the workpiece as the workpiece is translated/rotated using a 4-axis stage. This paper studies creating free-form, free-standing objects which is facilitated by the glass rapidly achieving structural rigidity as it cools upon exiting the molten region. The effects of the process parameters and printing techniques are examined and optimized to print simple wall and truss structures.

Development of Jig for Sintering Hollow Tube Mat

This paper presents the development of a jig for sintering a hollow tube mat. The jig consisted of metal frames, clampers, rails and wheels that were assembled together to hold a stack of hollow tubes in a form of a honeycomb structure. The sintering process involved a large oven where the hollow tube was sintered up to 120°C within two hours. During the sintering process, a partial of plastic parts was melted to allow diffusion around the particle cores. A clamping force from the jig held the tubes to make sure that the molten region around the sintered tubes retained in contact. This gives the compact a sufficient strength to hold together as the heat was removed. The jig developed in this study was capable to produce a hollow cellular mat within the size of approximately 1m (width) x 1m (length) x 1m (height).

Effects of Local Heating and Premelting in the Terminal Part of the e+ Track

The terminal part of the e+ track (the positron blob) is formed during ionization slowing down and subsequent ion-electron recombinations produced by a positron. It releases up to 1 keV of energy, which is converted into heat within few picoseconds. If a bulk temperature of a medium is below, but close enough to its melting point, some region of a substance may melt, yielding a peculiar temperature dependence of the lifetime (LT) spectra. We have estimated properties of the molten region with a help of macroscopic heat con- duction equation and suggested a model describing temperature dependence of the ortho- positronium lifetime in frozen methanol, ethanol, butanol and water close to their melting points.

Finite Element Model of Granite Ablation with UV Laser

This work presents 3-D Finite Element Model of the heat transfer inside granite during pulsed laser ablation with the aim of achieving laser cleaning treatment without damaging the stone surface. The model is focused on biotite, the most affected granite-forming mineral, owing to its low melting temperature. The model predicts sizes of the molten region that are consistent with experimental results. Moreover, the effects of different irradiation parameters; i.e., fluence, laser repetition frequency, and speed of scan have been investigated through the size of the biotite molten region. This model may be considered as the first stage of a comprehensive model of the laser ablation process in granite.

Molten Region around the Cavity Generated by a Moving Electron Beam

In this paper analytical predictions of the molten region around the cavity produced by a moving electron beam are provided. A three-dimensional analytical model is used to predict the molten and heat-affected regions surrounding a paraboloid of revolution-shaped cavity. This work avoids the defect of the infinite temperature at the cavity base for the line-source model. Introducing a new image method, an analytical solution is provided by satisfying exactly the adiabatic condition at the top surface. The molten region is governed by dimensionless parameters related to beam power per unit penetration and the depth and shape of the cavity in this work. A three-dimensional molten region is computed and presented in this paper. The effect of beam power per unit penetration on the molten region is also discussed.

Melting Solid Plug Between Two Coaxial Pipes by a Moving Heat Source in the Inner Pipe

Melting of a solid plug in the gap between two coaxial pipes by inserting a moving heat source in the inner pipe is investigated. Using a scale analysis, closed-form solutions for temperatures of liquid in the inner pipe, solid plug and liquid in the annular gap, and the surrounding medium around the outer pipe are determined. It is shown that eight independent dimensionless parameters are required to specify the entire process. The effects of independent parameters on the shapes of the molten region in the gap are found. The analysis and results provided are useful for the design of oil pipes.