OCHULO, I. Optimalizace tvaru mazací mezery hydrodynamického ložiska [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2021.

Posudek vedoucího

Novotný, Pavel

The master’s thesis comprises 42 pages excluding the introductory formal sections, literature review and list of figures used. Ochelo Ikechi consulted the thesis several times throughout the semester and then most during the last week. Unfortunately, the main problem in the production of the thesis was that the substantial parts of the thesis were created during the last two days before submission. The thesis does not contain new knowledge, only an unsuccessful combination of many different materials, often unrelated. Analytical methods, one-dimensional solutions and two-dimensional solutions are incompatibly combined. There is no investigation of the possibilities of mathematical optimisation of the problem solution. The results of the calculations are meaningless, e.g. negative hydrodynamic pressure over the whole surface, maximum pressure value of 18 Pa, negative load capacity etc. The student probably did not understand the meaning of the whole problem, i.e. to find the optimal profile of the lubrication gap. The Matlab scripts provided are unrelated subroutines, often just plotting permanently typed values. As a result, they are unusable. The work contains a number of unlabelled quantities, or a single quantity labelled with three different symbols (e.g. dimensionless lubrication gap thickness). Figures are of poor quality, some tables are unlabelled. The thesis contains many similar text parts to the work of Sawadkosin Paranee (Shape optimization of the machine components due to variability of input data, 2019) and also Jonathan Bature (Shape optimization of machine parts including the effect of probability distribution of input parameter values, 2021). The objectives of the thesis are not met and the thesis as a whole does not meet the requirements for a thesis at the master's level.

Posudek oponenta

Vacula, Jiří

The diploma thesis of Mr. Ikechi Ochulo includes 42 pages of his work (from introduction to conclusion). The work deals with the optimization of the general shape of the thrust bearing geometry by numerical approach. The work includes many flaws and mistypes. As a result, the reader is not able to understand the individual steps. Meeting the goals of the thesis was not achieved: „Program for optimizing the bearing working surface of general shape.” Some Matlab .m files are supplemented, however, there is no user guideline or explaining text. The user has no idea which file to open to set input parameters making this program basically inapplicable. „Application of the optimization procedure in the design of the working surface of the thrust bearing of a turbocharger.“ It is not proven that an optimal variant is found, there is no comparison of lubrication gap properties such as load capacity, friction force, etc. The work includes non-physical results: negative non-dimensional pressure (Figure 19), peak pressure only 14.9 Pa (page no. 33) and negative load capacity (Page no. 39). Resulting mass flow rate value is missing in the table on page no. 39. In addition, the equations 4.10, 4.11 and 4.12 do not correspond to the presented computational model because they are likely just taken over from the supervisor’s sources. Selected flaws are summarized below: Page 5: Title “Abstract” includes the sentence “Abstrakt česky”. The template of the work is very non-standard. List of symbols is missing. Citations are not numbered respectively, but randomly. Reference list (section 6) includes references which are not used in the text. It is references: [2-6], [13], [15, 16], [21-25]. Figures are not referenced in the text. Reader does not understand their meaning. Figure 3 (page no. 3) is insufficient – what is plane slider, where is force F? Non-standard sentences: section 1.4.: „The history of design is almost as old as the history of homo sapiens.” Reference on page no. 8 is strange. “Larry Fogel” is mentioned, subsequently the name is “Lawrence Fogel”. Neither Larry nor Lawrence Fogel is in the reference, however. Section 2.5.: citation of the whole paragraph without any introductory. Section 2.7. does not explain how this work fills the gap, there is only general information. In iii there is mentioned “general profile”, but general profile would mean topological optimization. The coordinate system is different in figure 5 than in figure 9. The reader is confused. The reader is confused by the comparison between figure 7 and 5. One complex figure would be more beneficial. In figure 7, there is p/x=0, but in equation 3.4. this derivation is introduced. The reader does not know if it is a further assumption. It is not clear what the length 10 and 15 means in figure 8. Figure 8 is not referenced either. Parameter h is not defined in equation 3.10. This parameter is introduced in equation 3.13. The reader does not see any mutual relationship. In equation 3.25 there is isolated operator 2. In equation 3.27 is U with index . But it should be U times . The origin of equation 3.41 is unclear. On page no. 21 there is discussed ’, but it in the equations there is *. The variables in equations 4.10 and 4.11 are not defined. Section 4 is not sorted in a logical way, the reader may not recognize, what the result is. The meaning of sub-section 4.5.3 is not clear either. The conclusion does not discuss the results themselves, instead, the general properties of the algorithm are discussed. The list of flaws is not definitely complete. The reader may find further ones. In general, the equations include many mistakes and they are not explained. The reader has no chance to diversify, which equations are correct and which not. In general, due to the very poor content of the diploma thesis and not achieving the goals, the thesis is classified by mark F.

eVSKP id 132790