Doctoral Degrees (Mechanical and Mechatronic Engineering)

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Browsing Doctoral Degrees (Mechanical and Mechatronic Engineering) by Author "Beyers, Wilhelm Andre"

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    Predicting structural behaviour of pressure vessels using large scale meta-modelling applied to plug type heat exchanger header boxes
    (Stellenbosch : Stellenbosch University, 2017-12) Beyers, Wilhelm Andre; Venter, Gerhard; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Plug type header boxes are predominantly designed according to the American Society of Mechanical Engineers’ Boiler and Pressure Vessel Code. The two design methods most often employed from this code are ‘Design by Rule’ from Division 1 of the code and ‘Design by Analysis’ from Division 2 Part 5. While ‘Design by Rule’ is relatively simple to implement and relies only on a set of hand calculations which produce immediate results, it is widely known to be conservative. ‘Design by Analysis’ on the other hand relies on finite element analysis, which yields more accurate results, but is more costly and time consuming. In this study a new analysis tool was developed in the form of a metamodel, based on finite element results, which predicts the structural behaviour for various plug type header boxes. The purpose of this tool is to provide a designer with real time predictions of the stresses in a header box, as is the case for ‘Design by Rule’, but with accuracy similar to a finite element analysis. In order to achieve this goal, a software tool set was developed which automates the process of setting up, simulating and post-processing the results of a finite element analysis. This made it possible to generate numerical results on a large scale, in order to collect enough data to train an accurate meta-model. Using this tool set, a number of less complex meta-models were initially created to test the approach and refine the procedure employed. These tests were performed using very large training sets and showed that high (4th and 5th) order response surface models were required to accurately approximate the structural behaviour of plug type header boxes. The challenges associated with fitting such high order response surfaces were addressed and these models were systematically scaled up in complexity until the final meta-model was constructed. The final meta-model achieved the desired goals of providing accurate stress results, in real time, for a plug type header box. Designers can use this model to search for optimal designs and identify what the structural effects are when individual header box dimensions are changed. This will allow for detailed insight to be gained of the structural behaviour of plug type header boxes in a manner which has been unavailable in the past. The implications of such knowledge will expand the field of knowledge surrounding these pressure vessels and open the door for the implementation of possible new design methods in the future.