Browsing by Subject "thermal history"

Now showing 1 - 7 of 7

Combining Burial Histories and Sedimentary Basin Rotations (PLATES Progress Report No. 267-0502)
(Institute for Geophysics, 2002) Campbell, Donald; Lawver, Lawrence A.; Gahagan, Lisa M.; Horn, Mike K.
EFFECTIVENESS OF EX-SITU HEAT TREATMENT OF L-PBF AM 17-4PH STAINLESS STEEL SPECIMENS INTENTIONALLY EXPOSED TO DIFFERENT AS-BUILT THERMAL HISTORIES
(University of Texas at Austin, 2023) Hasbrouck, C.R.; Bartolai, Joseph; Pagan, Darren C.; Miller, Simon W.
The presented research demonstrates the effectiveness of H900 heat treatment in eliminating microstructural and mechanical property differences between additively manufactured 17-4PH stainless steel samples of varying thermal histories. For this effort, 17-4PH stainless steel was manufactured using laser-based powder bed fusion on an EOS M280 machine in two geometries: ASTM Standard E8 subsize rectangular tensile specimen geometry with thicknesses of 2mm and 6mm. Thermal histories were manipulated by adding secondary laser passes on each layer at varying levels of reduced power. All samples were heat treated after the build following H900 procedures. Mechanical performance was evaluated with uniaxial quasi-static tensile testing and Vickers microhardness measurements. Metallography was examined qualitatively with optical and electron microscopy as well as quantitatively through electron backscatter diffraction. No statistically significant mechanical property or microstructural differences were discovered, suggesting a successful ex-situ heat treatment.
Fast Prediction of Thermal History in Large-Scale Parts Fabricated Via a Laser Metal Deposition Process
(University of Texas at Austin, 2018) Yan, Lei; Pan, Tan; Newkirk, Joseph W.; Liou, Frank; Thomas, Eric E.; Baker, Andrew H.; Castle, James B
Laser metal deposition (LMD) has become a popular choice for the fabrication of near-net shape complex parts. Plastic deformation and residual stresses are common phenomena that are generated from the intrinsic large thermal gradients and high cooling rates in the process. Finite element analysis (FEA) is often used to predict the transient thermal cycle and optimize processing parameters; however, the process of predicting the thermal history in the LMD process with the FEA method is usually time-consuming, especially for large-scale parts. Herein, multiple 3D FEA models with simple assumptions on the heat source and its loading methods are compared and validated with experimental thermocouple data.
Impact of Embedding Cavity Design on Thermal History between Layers in Polymer Material Extrusion Additive Manufacturing
(University of Texas at Austin, 2019) Sinha, Swapnil; Meisel, Nicholas A.
By pausing an additive manufacturing process in mid-print, it is possible to create multifunctional structures through strategic insertion of foreign components. However, in polymer material extrusion, previous research has shown that pausing the build decreases the eventual strength of the final part, due to cooling between layers. To better predict this part weakness, this paper seeks to quantify how the toolpath affects the thermal history of a cross-section, thus impacting the formation of weld strength between printed layers. This is pertinent to in-situ embedding as different embedded geometries will require different cavity designs, which, in turn, will affect toolpath design. In-situ thermal measurements are experimentally collected with a thermocouple at the layer interface of structures with different cavity designs. The weld strength between layers is then obtained through tensile tests and theoretically evaluated using polymer weld theory. Results show more accurate predictions of load at failure with this method.
Predicting and Controlling the Thermal Part History in Powder Bed Fusion Using Neural Networks
(University of Texas at Austin, 2019) Merschroth, Holger; Kniepkamp, Michael; Weigold, Matthias
Laser-based powder bed fusion of metallic parts is used widely in different branches of industry. Although there have been many investigations to improve the process stability, thermal history is rarely taken into account. The thermal history describes the parts’ thermal situation throughout the build process as a result of successive heating and cooling with each layer. This could lead to different microstructures due to different thermal boundary conditions. In this paper, a methodology based on neural networks is developed to predict and control the parts’ temperature by adjusting the laser power. A thermal imaging system is used to monitor the thermal history and to generate a training data set for the neural network. The trained network is then used to predict and control the parts temperature. Finally, tensile testing is conducted to investigate the influence of the adjusted process on the mechanical properties of the parts.
Thermal History Correlation with Mechanical Properties for Polymer Selective Laser Sintering (SLS)
(University of Texas at Austin, 2017) Taylor, Samantha; Beaman, Joseph; Fish, Scott
This study investigates the in-situ monitoring of the Selective Laser Sintering (SLS) process by focusing on finding correlations between tensile strength, elongation to break, and fracture location to the observed thermal history of manufactured parts. It compared the monitoring ability of a stationary reference mid-wave infrared and a bore-sighted mid-wave infrared camera. ZYX tensile bars were built to leverage the high dependence of tensile strength on interlayer bonding, which is generally assumed to be related to layerwise thermal conditions. Various thermal history analysis methods, for example: cold subregion temperature, average layer temperature, and outline average temperature were tested. Additionally, several smoothing techniques that reduced noise over time were assessed for their ability to improve the correlation for each individual method. Overall, cold subregions observed over four layers in a tensile bar’s thermal history had the best correlation with fracture location and mechanical strength.
THERMAL SIMULATION OF THE MATERIAL EXTRUSION PROCESS WITH DIFFERENT PRINT BED BOUNDARY CONDITIONS
(University of Texas at Austin, 2023) Huseynov, Orkhan; Al-Shaikh Ali, Mohammad; Fidan, Ismail
The temperature evolution in the material extrusion (MEX) process significantly affects the stability and bonding of 3D printed parts. Numerous studies have focused on developing models to capture the temperature history of the MEX process. However, there remains a need to explore the influence of different boundary conditions applied to the print bed. Additionally, the size of the bed relative to the 3D printed object has not been extensively investigated. This study aims to analyze the thermal behavior of the first layer in MEX by considering various boundary conditions and bed sizes. The obtained results will contribute to the development of faster yet reliable models for simulating the temperature variation in the MEX process.