Modeling Tape Cast Ceramics With Layers of Fugitive Phases

2012 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Ming-Jen Pan ◽  
Virginia G. DeGiorgi ◽  
Edward P. Gorzkowski
Keyword(s):  
Experimental Investigations ◽  
Uniform Density ◽  
Forming Process ◽  
Sintered Ceramic ◽  
Air Voids ◽  
Phase Approach ◽  
Pressure Distributions ◽  
Sacrificial Material ◽  
Ceramic Components ◽  
Carry Over

New fabrication methods for topologically complex monolithic ceramic components with accurate dimensions are being investigated. A common problem in the fabrication of precision ceramic components is controlling the forming process to attain uniform density in the green body; otherwise the tolerances achieved with green ceramics do not carry over to acceptable tolerances on the finished ceramic due to distortion and warping that occur during sintering. One of the fabrication methods under study is the fugitive phase approach in which a sacrificial material is used to form the desired channels and cavities. This paper is a continuation of previously presented work and examines the lamination step of the fugitive phase approach. In the lamination step, the green, pre-sintered, ceramic parts are layered with the sacrificial material parts and pressed together to remove air voids. During pressing uneven pressure distributions can be created in the green ceramic and the fugitive phase parts are slightly displaced or rotated. A computational model of the lamination process is used to examine how the material plasticity of the green ceramic, computational boundary conditions, and pressing duration affect the resulting geometry produced at the end of the lamination step prior to sintering. The resting stress, plastic strain, and deformed shapes are examined and compared. This information is used to complement experimental investigations of the fugitive phase approach.

Computational Modeling of Fugitive Phase Rotations Within Tape Cast Ceramics

2011 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Ming-Jen Pan
Keyword(s):  
Strain Energy ◽  
Fabrication Process ◽  
Experimental Investigations ◽  
Sintering Process ◽  
Phase Approach ◽  
Ceramic Components ◽  
Lamination Process ◽  
Carry Over ◽  
Geometric Layout ◽  
Tape Cast

For complex ceramic parts, new fabrication methods, such as the fugitive phase approach, are required. A common problem in the creation of ceramic parts is obtaining accurate dimensions of the final part. The sintering process makes it very difficult to create precise complex geometries. Tolerances achieved with green ceramics do not carry over to acceptable tolerances on the finished part due to non-uniform shrinkage and warping. The authors are investigating the application of the fugitive phase processing method, which might be able to fabricate topologically complex monolithic ceramic parts with precise tolerances. This paper is a continuation of previous work and examines the lamination step of the fugitive phase approach ceramic fabrication process; the step in which the fugitive phase material is integrated with the green ceramic material. In this step, the pressing along with the geometric layout of the fugitive phase material create an uneven pressure distribution in the green ceramic. Of particular concern is the rotation of the fugitive phase materials during the lamination step. A computational model of the lamination process is used to examine how the plasticity of the fugitive phase material along with computational boundary conditions affect the geometry of the green ceramic produced at the end of the lamination step prior to sintering. The resulting stress, strain energy, and deformed shapes are examined and compared. This information will be used to adjust the experimental investigations of the fugitive phase approach ceramic fabrication process that is working to create topologically complex ceramic components.

Three Dimensional Modeling of the Lamination of Unfired Ceramics With Fugitive Phases

2014 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Ming-Jen Pan ◽  
Virginia G. DeGiorgi
Keyword(s):  
Ceramic Body ◽  
Three Dimensional ◽  
Experimental Investigations ◽  
Pressure Gradients ◽  
Viscoelastic Deformation ◽  
Ceramic Phase ◽  
Phase Approach ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Ceramic Components

The dimensional accuracy of finished ceramic components depends upon the precise control of the unfired ceramic body prior to sintering. One approach for creating precise geometries is the fugitive phase approach. In the fugitive phase approach, the fugitive phase is a sacrificial material that can be removed to form channels in the finished ceramic component. In this paper, the authors computationally examine the fugitive phase approach; in particular, the lamination step of the fugitive phase approach is modeled. In the lamination step the unfired ceramic phases are combined with the fugitive phases through the application of pressure. For this research, the unfired ceramic phase consists of tape cast mullite and the fugitive phase is paper. These phases are laminated together in a die press to form a multilayer material. The compression of the die press causes pressure gradients, viscoelastic deformation, and rebounding of the unfired ceramic phases. In addition, the die press can cause movement of the fugitive phase pieces leaving unfilled voids. Three dimensional modeling is necessary to accurately capture the movement of the fugitive phase pieces. In this work the authors examine the viscoelastic deformation of the unfired ceramic phase, movement of the fugitive phase, the creation and filling of voids, pressure gradients, and the rebounding that occurs when the unfired ceramic body is removed from the die press. The information obtained from computational simulations will be used to help direct experimental investigations of the fugitive phase approach for fabrication of complex ceramic components.

Numerical and Experimental Investigations of Multistage Sheet-Bulk Metal Forming Process with Compound Press Tools

2015 ◽  
Vol 651-653 ◽  
pp. 1153-1158 ◽  
Author(s):  
Bernd Arno Behrens ◽  
Anas Bouguecha ◽  
Milan Vucetic ◽  
Sven Hübner ◽  
Daniel Rosenbusch ◽  
...  
Keyword(s):  
Metal Forming ◽  
Solid Metal ◽  
Experimental Investigations ◽  
Metal Component ◽  
Forming Process ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Process Sequence ◽  
Metal Forming Process ◽  
Flange Forming

Sheet-bulk metal forming is a manufacturing technology, which allows to produce a solid metal component out of a flat sheet. This paper focuses on numerical and experimental investigations of a new multistage forming process with compound press tools. The complete process sequence for the production of this solid metal component consists of three forming stages, which include a total of six production techniques. The first forming stage includes deep drawing, simultaneous cutting and following wall upsetting. In the second forming stage, flange forming combined with cup bottom ironing takes place. In the last stage of the process sequence, the component is sized. To investigate and to improve process parameters such as plastic strain distribution, resulting dimensions and process forces, FEA is performed. Based on these results the developed process is designed.

FEM Simulation Analysis of Cross Wedge Rolling Process

2011 ◽  
Vol 381 ◽  
pp. 72-75
Author(s):  
Bin Li
Keyword(s):  
Simulation Analysis ◽  
Three Dimensional ◽  
Fem Simulation ◽  
Rolling Process ◽  
Stress Distributions ◽  
Cross Wedge Rolling ◽  
Forming Process ◽  
Pressure Distributions ◽  
Metal Forming Process ◽  
Rolling Load

This paper investigates the interfacial slip between the forming tool and workpiece in a relatively new metal forming process, cross-wedge rolling. Based on the finite elements method, three-dimensional mechanical model of cross wedge rolling process has been developed. Examples of numerical simulation for strain, stress distributions and rolling load components have been included. The main advantages of the finite element method are: the capability of obtaining detailed solutions of the mechanics in a deforming body, namely, stresses, shapes, strains or contact pressure distributions; and the computer codes, can be used for a large variety of problems by simply changing the input data.

scholarly journals Aerodynamics and Heat Transfer Investigations on a High Reynolds Number Turbine Cascade

1991 ◽  
Author(s):  
Taher Schobeiri ◽  
Eric McFarland ◽  
Frederick Yeh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
Test Facility ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Calculation Methods ◽  
Transfer Coefficients ◽  
Pressure Distributions ◽  
High Reynolds

In this report the results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the space shuttle main engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.

Advanced Turbine Technology Applications Project (ATTAP): Overview, and Ceramic Component Technology Status

1991 ◽  
Author(s):  
Philip J. Haley
Keyword(s):  
High Speed ◽  
High Volume ◽  
Department Of Energy ◽  
High Yield ◽  
Design System ◽  
Ceramic Component ◽  
Forming Process ◽  
Technology Applications ◽  
Ceramic Components ◽  
Monolithic Ceramics

The automotive gas turbine’s (AGT) significant potential payoffs in fuel economy, emissions, and alternate fuels usage continue to motivate development activities worldwide. The U.S. Department of Energy-sponsored, NASA-managed Advanced Turbine Technology Applications Project (ATTAP) focuses on developing critical AGT structural ceramic component technologies. The area of greatest challenge is that of cost-effective, near-net-shape, high-volume, high-yield manufacturing processes. Process physics modeling and Taguchi analyses are affording substantial progress, and new processes are being explored. Laboratory characterization is building a shared materials data base among Allison, Garrett, Government labs, and ceramic manufacturers. General Motors (GM) has logged over 700 test hours with ceramic components in hot gasifier rigs during ATTAP. A key ATTAP milestone was addressed by successfully demonstrating full goal temperature and speed (2500°F rotor inlet at 100% shaft speed) with ceramic components. Fast-fracture ceramic component design tools are well correlated. Although time-dependent data and mechanistic models exist, a validated design system for such phenomena does not, and is a pressing need. Damage tolerance and impact resistance have been substantially addressed through tailored component designs, tougher monolithic ceramics, and increased ceramic strengths. Ceramic turbine rotors are now continuing to run after various substantial impacts, and after chipping damage. Ceramic-ceramic and ceramic-metal interfacing is being addressed by minimizing components’ joints, and by other DOE-sponsored work on joining models, processes, and materials. The extruded regenerator disk is a continuing goal which requires both forming process and materials technology development. Controlling turbine tip clearances and tolerating tip rubs are key technologies. GM has demonstrated clearance control schemes, as well as rotor survivability to high speed/temperature tip rubs. Several noteworthy ceramic materials reflect the rapid progress over the past decade of monolithic ceramics, especially the Si3N4 family. GM forecasts achieving ATTAP engine cyclic durability goals.

Preparation of Multilayer Barium Titanate PTC Thermistor with Low Room Temperature Resistance

2007 ◽  
Vol 280-283 ◽  
pp. 1921-1924 ◽  
Author(s):  
Dong Xiang Zhou ◽  
Huan Liu ◽  
Shu Ping Gong ◽  
Dao Li Zhang
Keyword(s):  
Barium Titanate ◽  
Room Temperature ◽  
Roll Forming ◽  
Forming Process ◽  
Sintered Ceramic ◽  
Temperature Resistance ◽  
Typical Size ◽  
Temperature Characteristics ◽  
Chip Type ◽  
Roll Forming Process

Chip-type PTC thermistors with multilayer stacked structure have been fabricated by bonding sintered ceramic chips with internal electrodes to offer low resistance at room temperature and correspondence to surface mounted technology. The resistance-temperature characteristics of multiplayer stacked PTC thermistors made up of different numbers (N = 1, 3, 5) of layers were experimentally investigated (the typical size of each layer was 10 mm × 7.0 mm × 0.38 mm). The selection and extraction of additives in roll-forming process were also discussed. This resulted in a crack-free multiplayer stacked PTC thermistor.

An Investigation on Turbine Tip and Shroud Heat Transfer

2003 ◽  
Vol 125 (3) ◽  
pp. 513-520 ◽  
Author(s):  
Kam S. Chana ◽  
Terry V. Jones
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Guide Vane ◽  
Pressure Ratio ◽  
Experimental Investigations ◽  
Inlet Temperature ◽  
Turbine Stage ◽  
Pressure Distributions ◽  
Engine Design ◽  
Nozzle Guide

Detailed experimental investigations have been performed to measure the heat transfer and static pressure distributions on the rotor tip and rotor casing of a gas turbine stage with a shroudless rotor blade. The turbine stage was a modern high pressure Rolls-Royce aero-engine design with stage pressure ratio of 3.2 and nozzle guide vane (ngv) Reynolds number of 2.54E6. Measurements have been taken with and without inlet temperature distortion to the stage. The measurements were taken in the QinetiQ Isentropic Light Piston Facility and aerodynamic and heat transfer measurements are presented from the rotor tip and casing region. A simple two-dimensional model is presented to estimate the heat transfer rate to the rotor tip and casing region as a function of Reynolds number along the gap.

Application of a Material Model to Predict Rolling Forces and Microstructure during a Hot Ring Rolling Process

2013 ◽  
Vol 762 ◽  
pp. 354-359 ◽  
Author(s):  
Thomas Henke ◽  
Gerhard Hirt ◽  
Markus Bambach
Keyword(s):  
Grain Size ◽  
Microstructure Evolution ◽  
Rolling Force ◽  
Flow Behavior ◽  
Rolling Process ◽  
Ring Rolling ◽  
Experimental Investigations ◽  
Forming Process ◽  
Ring Geometry ◽  
Ring Rolling Process

Ring rolling is an incremental bulk forming process. Hence, the process consists of a large number of alternating deformations and dwell steps. For accurate calculations of material flow and thus ring geometry and rolling forces in hot ring rolling processes, it seems necessary to consider material softening due to static and post dynamic recrystallization which could occur between two deformation steps. In addition, due to the large number of cycles, the modeling results, especially the prediction of grain size, can easily be affected by uncertainties in the input data. However, for small rings and ring material with slow recrystallization kinetics, the interpass times can be short compared to the softening kinetics and the effect of softening can be so small, that microstructure evolution and the description of the materials flow behavior can be de-coupled. In this paper, a semi-empirical JMAK-based model for a stainless steel (1.4301/ X5CrNi18-9/ AISI304) is presented and evaluated by the use of experiments and other investigations published in [1],[2]. Finite Element (FE) simulations of a ring rolling process with a high number of ring revolutions and thus multiple, incremental forming steps were conducted based on ring rolling experiments. The FE simulation results were validated with the experimentally derived rolling force and evolution of ring diameter. The microstructure evolution was calculated in a post processing step considering the investigated evolution of strain and temperature. In this calculation the interrelations between the fraction of dynamically recrystallized microstructure, the evolution of post-dynamically recrystallized microstructure and the final grain size have been considered. Both, the calculated final microstructure and the evolution of rolling force and ring geometry calculated stand in good agreement with the experimental investigations.

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