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.

Computational Modeling of Lamination of Tape Casted Ceramics With a Fugitive Phase

2010 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Virginia G. DeGiorgi ◽  
Ming-Jen Pan
Keyword(s):  
Computational Modeling ◽  
Computational Model ◽  
Pressure Distribution ◽  
Ceramic Material ◽  
Strain Energy ◽  
Fabrication Process ◽  
Complex Geometries ◽  
Phase Approach ◽  
Lamination Process ◽  
Geometric Layout

The complex geometries required for new and novel ceramic parts require new fabrication methods such as the fugitive phase approach. This paper examines the lamination step of fugitive phase approach ceramic fabrication process. The lamination step integrates the fugitive phase with the green ceramic material. The pressing used along with the geometric layout of the fugitive phase during the lamination step creates an uneven pressure distribution in the green ceramic. This pressure distribution causes density gradients and warping in the final ceramic part. A preliminary computational model of the lamination process is modeled and the resulting stress, strain energy, and deformed shape are examined.

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.

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.

Modeling Tape Cast Ceramics With Multiple Layers of Fugitive Phase Materials

2012 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Ming-Jen Pan ◽  
Virginia G. DeGiorgi ◽  
Edward P. Gorzkowski ◽  
Alan C. Leung
Keyword(s):  
Ceramic Body ◽  
Experimental Investigations ◽  
Green Body ◽  
Ceramic Component ◽  
Viscoelastic Deformation ◽  
Ceramic Phase ◽  
Precise Control ◽  
Phase Approach ◽  
New Processing ◽  
Tape Cast

The fabrication of complex ceramic components requires new processing methods that are able to produce components with intricate geometries and accurate dimensions. The accuracy of the finished ceramic component depends upon precise control of the green ceramic body dimensions and uniformity prior to sintering. The authors are investigating the application of the fugitive phase approach, where a sacrificial material is used to form cavities or channels in the finished ceramic component. This paper, a continuation of a previous work, examines the lamination step of the fugitive phase approach for ceramic fabrication. The lamination step is where the fugitive phase pieces are combined with the tape cast green ceramic pieces. The multilayer green body is pressed to laminate the ceramic tape and fugitive phase layers together. Topological complexity is greatly increased when the tape cast ceramic pieces are interspersed with fugitive phase pieces to build up a consolidated multilayer green body. This paper examines the movement of the fugitive phase pieces, viscoelastic deformation of the ceramic phase, the filling of voids, pressure gradients, and the rebounding that occurs when the green ceramic body is removed from the press. This information will be used to complement parallel experimental investigations of the fugitive phase approach to ceramic fabrication.

An Extended Tube-Model for Rubber Elasticity: Statistical-Mechanical Theory and Finite Element Implementation

1999 ◽  
Vol 72 (4) ◽  
pp. 602-632 ◽  
Author(s):  
M. Kaliske ◽  
G. Heinrich
Keyword(s):  
Finite Element ◽  
Parameter Identification ◽  
Energy Function ◽  
Strain Energy ◽  
Strain Energy Function ◽  
Rubber Elasticity ◽  
Experimental Investigations ◽  
Structural Level ◽  
Tube Model ◽  
Starting Point

Abstract A novel model of rubber elasticity—the extended tube-model—is introduced. The model considers the topological constraints as well as the limited chain extensibility of network chains in filled rubbers. It is supplied by a formulation suitable for an implementation into a finite element code. Homogeneous states of deformation are evaluated analytically to yield expressions required e.g., for parameter identification algorithms. Finally, large scale finite element computations compare the extended tube-model with experimental investigations and with the phenomenological strain energy function of the Yeoh-model. The extended tube-model can be considered as an interesting approach introducing physical considerations on the molecular scale into the formulation of the strain energy function which is on the other hand the starting point for the numerical realization on the structural level. Thus, the gap between physics and numerics is bridged. Nevertheless, this study reveals the importance of a proper parameter identification and adapted experiments.

Lifetime Prediction for Ceramic Gas Turbine Components

1993 ◽  
Vol 115 (1) ◽  
pp. 70-75 ◽  
Author(s):  
G. Stu¨rmer ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Gas Turbine ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Operation Time ◽  
Computer Code ◽  
Experimental Investigations ◽  
Ceramic Components ◽  
Stress States ◽  
Dependent Failure ◽  
Failure Probabilities

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), theoretical and experimental investigations of ceramic gas turbine components are performed. For the reliability analysis by finite element calculations the computer code CERITS has been developed. This code is used to determine the fast fracture reliability of ceramic components subjected to polyaxial stress states with reference to volumetric flaws and was presented at the 1990 IGTI Gas Turbine Conference. CERITS-L now includes subcritical crack growth. With the new code CERITS-L, failure probabilities of ceramic components can be calculated under given load situations versus time. In comparing these time-dependent failure probabilities with a given permissible failure probability, the maximum operation time of a component can be determined. The considerable influence of the subcritical crack growth upon the lifetime of ceramic components is demonstrated at the flame tube segments of the ITS ceramic combustor.

scholarly journals Mechanical characterization and numerical modeling of laser-sintered TPE lattice structures

2021 ◽  
Author(s):  
Christina Kummert ◽  
Hans-Joachim Schmid ◽  
Lena Risse ◽  
Gunter Kullmer
Keyword(s):  
Numerical Modeling ◽  
Thermoplastic Elastomer ◽  
Experimental Investigations ◽  
Lattice Structures ◽  
Sintering Process ◽  
Compression Tests ◽  
Plastic Properties ◽  
Cell Parameters ◽  
Cyclic Compression

Abstract Additive Manufacturing provides the opportunity to produce tailored and complex structures economically. The use of lattice structures in combination with a thermoplastic elastomer enables the generation of structures with configurable properties by varying the cell parameters. Since there is only little knowledge about the producibility of lattice structures made of TPE in the laser sintering process and the resulting mechanical properties, different kinds of lattice structures are investigated within this work. The cell type, cell size and strut thickness of these structures are varied and analyzed. Within the experimental characterization of Dodecahedron-cell static and cyclic compression tests of sandwich structures are focused. The material exhibits hyperelastic and plastic properties and also the Mullins-Effect. For the later design of real TPE structures, the use of numerical methods helps to reduce time and costs. The preceding experimental investigations are used to develop a concept for the numerical modeling of TPE lattice structures. Graphic abstract

Life Time Prediction for Ceramic Gas Turbine Components

1991 ◽  
Author(s):  
G. Stürmer ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Gas Turbine ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Operation Time ◽  
Life Time ◽  
Computer Code ◽  
Experimental Investigations ◽  
Ceramic Components ◽  
Stress States ◽  
Failure Probabilities

At the Institute for Thermal Turbomachinery, University of Karlsruhe (ITS), theoretical and experimental investigations on ceramic gas turbine components are performed. For the reliability analysis by finite element calculations the computer code CERITS has been developed. This code is used to determine the fast fracture reliability of ceramic components subjected to polyaxial stress states with reference to volumetric flaws and was presented at the 1990 IGTI Gas Turbine Conference. CERITS-L now includes subcritical crack growth. With the new code CERITS-L, failure probabilities of ceramic components can be calculated under given load situations versus time. In comparing these time dependent failure probabilities with a given permissible failure probability, the maximum operation time of a component can be determined. The considerable influence of the subcritical crack growth upon the life time of ceramic components is demonstrated at the flame tube segments of the ITS ceramic combustor.

scholarly journals Experimental investigations for improved modelling of the laser sintering process of polymers

Procedia CIRP ◽  
2020 ◽  
Vol 94 ◽  
pp. 80-84 ◽  
Author(s):  
Johannes Rudloff ◽  
Marieluise Lang ◽  
Shoya Mohseni-Mofidi ◽  
Claas Bierwisch
Keyword(s):  
Laser Sintering ◽  
Experimental Investigations ◽  
Sintering Process

Low Angle Grain Boundary Dewetting in Sapphire

2001 ◽  
Vol 7 (S2) ◽  
pp. 384-385
Author(s):  
B.J. Hockey ◽  
M-K. Kang ◽  
S.M. Wiederhorn ◽  
J.E. Blendell
Keyword(s):  
Liquid Phase ◽  
Grain Boundary ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Transmission Electron ◽  
Wide Range ◽  
Grain Boundary Wetting ◽  
Tape Cast ◽  
Single Boundary ◽  
Current Emphasis

The structure and composition of low angle grain boundaries produced in sapphire by a liquid phase sintering process were investigated by conventional and high resolution transmission electron microscopy (CTEM and HRTEM, respectively). Considering the current emphasis on producing ceramics with textured microstructures for various applications, the question of grain boundary wetting vs. dewetting has become a relevant issue to determining the microstructure development and the properties of these liquid phase sintered materials. Accordingly, the present study was designed to cover a wide range of tilt misorientations, twist misorientations, and boundary orientations.The boundaries were formed by the directed growth of two sapphire plates, both having nominal <0001>, , or surface orientations through an alumina tape-cast containing an anorthite composition glass phase. After an initial hot-pressing stage, followed by an anneal at 1600° C for 200 hours, the samples typically contained a single boundary delineated by isolated pockets of entrapped glass, Fig. 1.

Sign in / Sign up

Export Citation Format

Share Document