Research on Quartz Flat Mirror’s Thermal Deformation under the Condition of Non Uniform Heating

2011 ◽  
Vol 704-705 ◽  
pp. 229-235
Author(s):  
Suian Dai ◽  
Sheng Li Chang ◽  
Yong Lan ◽  
Jian Feng Luo ◽  
Fei Wang
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Thermal Deformation ◽  
Element Model ◽  
Thermal Imager ◽  
The Sun ◽  
Uniform Heating ◽  
Temperature Boundary ◽  
Definite Temperature ◽  
Temperature Boundary Condition

The optical system used in aerospace works under a very difficult aerospace condition. The temperature difference between the sides which one is facing the sun and the other one is opposite the sun can reach about 200°C. These temperature grids can bring thermal deformation to the optical components and then influence the whole system’s image or detect results. To measure and analysis the deformation, we first use finite element method to establish a heat exchange model with definite temperature boundary condition to simulate the thermal distribution situation of an optical mirror, and then we establish a laboratory experimental environment and use the thermal imager to measure the temperature distribution on the surface of the mirror and use Zygo GPI XP-D/1000 interferometer to measure the thermal deformation, from the experimental results, we can see that the definite temperature boundary condition is good enough. And the definite flow boundary condition is not necessary under this non uniform heating situation. Key Words: thermal deformation, finite element model, non uniform heating

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

scholarly journals An integral relationship for a fractional one-phase Stefan problem

2018 ◽  
Vol 21 (4) ◽  
pp. 901-918 ◽  
Author(s):  
Sabrina Roscani ◽  
Domingo Tarzia
Keyword(s):  
Boundary Condition ◽  
Stefan Problem ◽  
One Dimensional ◽  
Similarity Type ◽  
Integral Relationship ◽  
Temperature Boundary ◽  
Liouville Derivative ◽  
The One ◽  
Stefan Condition ◽  
Temperature Boundary Condition

Abstract A one-dimensional fractional one-phase Stefan problem with a temperature boundary condition at the fixed face is considered by using the Riemann–Liouville derivative. This formulation is more convenient than the one given in Roscani and Santillan (Fract. Calc. Appl. Anal., 16, No 4 (2013), 802–815) and Tarzia and Ceretani (Fract. Calc. Appl. Anal., 20, No 2 (2017), 399–421), because it allows us to work with Green’s identities (which does not apply when Caputo derivatives are considered). As a main result, an integral relationship between the temperature and the free boundary is obtained which is equivalent to the fractional Stefan condition. Moreover, an exact solution of similarity type expressed in terms of Wright functions is also given.

Finite-Element Simulations and Probabilistic Fracture Assessments of the Response of Alternate Rifling Geometries

2007 ◽  
Author(s):  
A. E. Segall ◽  
R. Carter
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Thermal Stresses ◽  
Rotational Symmetry ◽  
Element Model ◽  
Time Dependent ◽  
Uniform Heating ◽  
Thermal Pressure ◽  
Single Firing ◽  
Hoop Stresses

A 3-D finite-element model was used to simulate the severe and localized thermal/pressure transients and the resulting stresses experienced by a rifled ceramic-barrel with a steel outer-liner; the focus of the simulations was on the influence of non-traditional rifling geometries on the thermoelastic- and pressure-stresses generated during a single firing event. In order to minimize computational requirements, a twisted segment of the barrel length based on rotational symmetry was used. Using this simplification, the model utilized uniform heating and pressure across the ID surface via a time-dependent convective coefficient and pressure generated by the propellant gasses. Results indicated that the unique rifling geometries had only a limited influence on the maximum circumferential (hoop) stresses and temperatures when compared with more traditional rifling configurations because of the compressive thermal stresses developed at the heated (and rifled) surface.

Thermoplastic Fusion Bonding of Polymer-Based Micro Devices Using a Pressure Cooker

2009 ◽  
Author(s):  
Taehyun Park ◽  
Thomas J. Zimmerman ◽  
Daniel Park ◽  
Brooks Lowrey ◽  
Michael C. Murphy
Keyword(s):  
Boundary Condition ◽  
Pressure Distribution ◽  
Water Vapor Pressure ◽  
Critical Parameters ◽  
Precise Control ◽  
Fusion Bonding ◽  
Temperature Boundary ◽  
Temperature And Pressure ◽  
Temperature Boundary Condition ◽  
Polymer Container

A novel method of thermoplastic fusion bonding (TPFB), or thermal bonding, for polymer fluidic devices was demonstrated. A pressure cooker was used in a simple sealing and packaging process with precise control of the critical parameters. Polymer devices were enclosed in a vacuum-sealed polymer container. This produced an even pressure distribution and a precise temperature boundary condition over the whole surface of the device. Deformation indicators were integrated on the devices to provide a rapid means of checking deformation and pressure distribution with the naked eye. Temperature, pressure, and time are the fundamental parameters of TPFB. The temperature and pressure are dominated by the material and contact area of the device. The temperature and pressure can be manipulated by controlling the water vapor pressure. The boiling solution guarantees an accurate, constant temperature boundary condition. Time can be eliminated as a variable by choosing a sufficient time to achieve good bonding, since there was no apparent damage to the microstructures after one hour. This new method of TPFB was demonstrated for sealing and packaging a PMMA (polymethylmethacrylate) microfluidic device. Good results were obtained using the vacuum sealed polymer container in the pressure cooker. This method is also suitable for scaling up for mass production.

Theoretical and Finite Element Analysis of Crosshead of Quintuple Cylinders Fracturing Pump

2011 ◽  
Vol 201-203 ◽  
pp. 253-256 ◽  
Author(s):  
Zhi Peng Lv ◽  
Si Zhu Zhou ◽  
Xiu Hua Ma
Keyword(s):  
Boundary Condition ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Maximum Force ◽  
Element Analysis ◽  
Plunger Pump ◽  
Load Handling ◽  
The Finite Element Model

According to the plunger pump movement principle, this paper analyzed the two kind of typical force situation of the crosshead, and obtained the theoretical maximum force. Established the finite element model of the crosshead, gave an analysis to the load handling and boundary condition. The last results of the node stress and displacement show that the crosshead can work safely.

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