June 14, 2009
June 14, 2009
June 17, 2009
Computers in Education
14.219.1 - 14.219.9
Application of FEMLAB Software for Simulation of the Thermal Method for Nondestructive Testing Introduction
The thermal nondestructive testing (TNDT) method is widely used for inspection of industrial parts and components. The method involves heating the object and subsequently measuring the temperature of its surface. This change in temperature provides information about the test object’s structure. The surface temperature changes if the discontinuity exists inside the object.
The laboratory training allows students to understand the fundamental processes, which take place during the TNDT procedure. Students are able to simulate this procedure use FEMLAB software package. This interactive software package is based on application of partial differential equations for simulation of scientific and technical problems related to TNDT. Applied modes of this software allow the development of models with desired properties of a test object and heat flow. FEMLAB package generates the system of partial differential equations, which represent a complete model of TNDT processes. The finite element analysis method is used for solving partial differential equations.
I. Creation of the thermal processes model in FEMLAB software
A blast furnace is used as a test object (TO). The cast-iron blocks, which have internal discontinuities, will be tested. A defect (blister or crack) has different heat-transfer properties than metal. Distortion of the thermal field on the surface of a metal block will indicate the presence of the discontinuity.
The 2D model of a TO will be discussed below in details. A cross-section of the cast-iron 8 x 4 cm rectangular block, which has 2 cm in diameter blister filled with air, will be used as a model. The temperature of one of the block surfaces is 873 K. The other three block surfaces have ambient temperature -293K. Temperature distribution on the block surfaces could be determined according to the heat-transfer properties of cast-iron material and air. These properties are presented in the handbook.
There is a need to activate the FEMLAB Graphical User Interface (GUI) to start simulation. A figure of the Model Navigator panel appears after the GUI activation (see Fig.1). It is necessary to mark the button 2D and choose the model Physics modes/ Heat transfer/ Time depended to prepare the GUI for creation of the two-dimensional TO model.
Creation of the TO geometry
A cross-section of the TO can be drawn using the option Draw from the main menu. The origin of coordinate is placed in the center of the TO which is represented as a rectangle (8x4 cm) with a circle 2cm in diameter. A rectangle and circle with a necessary size can be drawn in the field of Axes using a mouse. The model of the defective TO cross-section is represented on the Fig. 2.
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