Browsing by Subject "temperature distribution"

Now showing 1 - 4 of 4

Effects of Scanning Strategy on Residual Stress Formation in Additively Manufactured Ti-6Al-4V Parts
(University of Texas at Austin, 2017) Masoomi, Mohammad; Thompson, Scott M.; Shamsaei, Nima; Haghsenas, Meysam
Parts fabricated via directed energy additive manufacturing (AM) can experience very high, localized temperature gradients during manufacture. These temperature gradients are conducive to the formation of a complex residual stress field within such parts. In the study, a thermo-mechanical model is employed for predicting the temperature distribution and residual stress in Ti-6Al-4V parts fabricated using laser-powder bed fusion (L-PBF). The result is utilized for determining a relationship between local part temperature gradients with generated residual stress. Using this numerical model, the effects of scan patterns are investigated.
Selective Laser Sintering of Polycarbonate at Varying Powers, Scan Speeds and Scan Spacings
(1994) Childs, T.H.C.; Cardie, S.; Brown, J.M.
A benchmark study (1) has shown selective laser sintering to be the equal of or to have accuracy advantages over other processes for creating parts of size over 10 mm. Experience is needed to achieve best accuracies, as with other processes. This paper is (for us) a first step in understanding the relation between sintering parameters, part size and acuracy. Work at the University of Texas at Austin (2-4) has established that the sintering of polycarbonate can be understood in terms of a rate model driven by viscous and surface tension effects. Material properties are such that a sharp boundary exists between sintered and unsintered material. When full density is not achieved in a part, density within a single layer varies from fully sintered to totally unsintered; measured part density is thus a mean of widely varying values. Published work (3-4) uses a onedimensional non-steady state heat flow model to calculate the temperature profile and densification beneath the surface and concentrates on the effects on this of material properties varying with temperature and during sintering. In this paper, these variations are ignored but a three dimensional non-steady heat flow is used to enable edge effects to be estimated. Density gradients at edges are assumed to be responsible for variations of accuracy with sintering parameters, part size, part shape and orientation.
Temperature History within Laser Sintered Part Cakes and Its Influence on Process Quality
(University of Texas at Austin, 2015) Josupeit, Stefan; Schmid, Hans-Joachim
The temperature distribution and history within laser sintered part cakes is an important aspect regarding the process quality and reproducibility of the polymer laser sintering process. Especially the temperature history during the build and cooling phase is decisive for powder ageing effects and the development of part quality characteristics. In this work, a measurement system for three-dimensional in-process temperature measurements is set up and the influence of different parameters on the inner part cake temperature distribution and history is analyzed. Important factors are not only geometrical build job parameters like the part packing density and build height, but also process parameters like the layer thickness and bulk powder density. Individual in-process temperature profiles at different positions within a part cake are finally correlated with powder ageing effects. The results of this work help to understand the temperature history dependency of powder and part properties and can therefore be used to develop optimized process controls.
Thermography for Monitoring the Selective Laser Melting Process
(University of Texas at Austin, 2012-08-22) Krauss, H.; Eschey, C.; Zaeh, M.F.
A lot of strategies exist to monitor and control additive layer manufacturing processes. Basically one can distinguish between coaxially monitoring the process zone and monitoring the complete layer currently being built. Since Selective Laser Melting is a thermal process, a lot of information about the process and in consequence about the resulting part quality can be gathered by monitoring the temperature distribution of a complete layer and its temporal evolution. It depends on the geometrical configuration of parts being built and the quality of the powder layer deposition. In this paper, process errors originating from insufficient heat dissipation are investigated as well as the limits for detecting pores and other irregularities by observation of the temperature distribution.