Design and development of a multi-axis controlled thermal scanner
- Authors: Ikho, Bambiso
- Date: 2015
- Subjects: Temperature measurements Heat -- Transmission -- Measurement , Heat -- Transmission
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/50066 , vital:41998
- Description: Surface temperature measurement is applicable to a vast number of fields including manufacturing, processing, agricultural, medical and pharmaceutical fields just to name a few. Two methods for obtaining surface temperature measurements exist; ‘surface contact measurement’ in which the measuring device makes physical contact with the surface in question or alternatively, ‘non-contact surface measurement’ where there is no contact at all. Both of these methods have got advantages, as well as disadvantages. However, in recent times, non-contact methods have been preferred since they are non-intrusive and allow for remote measurements to be made. In this research, a non-contact mobile temperature measurement system is developed. The system is microcontroller-based and uses infrared sensors to acquire temperature measurements. The infrared sensors are mounted on a three-axes, x-y-z coordinate system which allows a thermal profile of a particular surface to be generated and displayed on a Graphical User Interface (GUI) in real-time. Various tests were carried out to compare contact and non-contact measurement methods; to determine the most suitable operating height for accurate non-contact measurement given a specific surface and to investigate the benefit of single and/ or multiple sensor arrangements. The research showed that a non-contact thermal scanning system could be used to obtain detailed yet accurate surface temperature measurements following an initial sensor calibration phase to determine the most favourable scanning parameters for a particular surface. The measurements taken could then be used to generate a thermal map of a surface with a significant improvement in resolution as compared with measurements taken using contact devices. The research further showed that a multiple sensor arrangement significantly reduced the time taken to generate the thermal profiles without undermining accuracy.
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- Date Issued: 2015
Finite element analysis of the heat transfer in friction stir welding with experimental validation
- Authors: Vosloo, Natalie
- Date: 2012
- Subjects: Finite element method , Heat -- Transmission , Friction welding
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10511 , http://hdl.handle.net/10948/d1019981
- Description: Friction stir welding is a relatively new joining process. The heat transfer involved is crucial in determining the quality of the weld. Experimenrtal data, though important, does not provide enough information about the heat transfer process and experiments can be costly and time consuming. A numerical model, using the finite element method, was developed to stimulate the heat transfer in the workpiece in which the heat generation due to friction and plastic deformation was modelled as a surface heat flux boundary condition. This model was applied to Aluminium AL6082-T6 and Titanium Ti6A1-4V for different welding condiitions. Results were validated with experimental results. The model was shown to give better predictions of the maximum temperatures at locations in the workpiece than the overall temperature trend. A parametric study was also performed on the Aluminium model in order o predict temperature fields of the workpiece for welding conditions that were additional to those undertaken experimentally. It was found that rotational speed had a larger effect on the change in temperature than the feed rate. From the parametric study it was also clear that lower rotational speeds (300 to 660 rpm) had a greater effect on the change in temperature than the higher rotational speeds (840 to 1200 rpm). It was concluded that the model was well suited for the estimation of temperatures involved in the FSw of Aluminium Al6082-T6 but was not as accurate when applied to the FSW of Titanium.
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- Date Issued: 2012