National Repository of Grey Literature 5 records found  Search took 0.00 seconds. 
Evaluation of the quality of laser cutting surfaces
Krejčiřík, Marek ; Sigmund, Marian (referee) ; Kubíček, Jaroslav (advisor)
As the title implies, the topic to be solved in this diploma thesis was describing and evaluating the CO2 and fiber laser cutting technologies and their comparison with plasma and oxygen cutting, described in the standard ČSN EN ISO 9013. Samples of IMEX 700 high-strength fine-grain steel with a yield strength of 690 MPa were used and subjected to a final quality assessment. The diploma thesis is divided into two parts – theoretical and experimental. The theoretical part is mainly focused on a laser. Among other things, the principle of plasma and oxygen cutting was discussed. The cutting edges of samples cut by these methods were analyzed and compared in an experiment. Last but not least, the surface roughness, material hardness, and their measurement methods were discussed in the theoretical part. The final cuts after laser, plasma, and oxygen cutting were evaluated and compared in the experimental part. The roughness of the individual cuts was compared, and measured values were classified into the relevant quality classes specified by the standard EN ISO 9013. The thermal influence of the cutting joint, the width of the thermally influenced area and the hardness history were further evaluated parameters. The obtained results were discussed and summarized in the conclusion. Studied technologies were compared. Based on the experiment, fiber laser cutting was determined as the best choice regarding quality and economics.
Plasma cutting of high strength steels
Šmak, Martin ; Herčík, Tomáš (referee) ; Kubíček, Jaroslav (advisor)
Cutting of steel is one of the fundamental operations within steel processing and steel product manufacturing. The cutting of high-strength steels represents a significant technological problem since the application of many methods produces an extensive amount of heat that is introduced into the material. The heat may significantly impact the mechanical properties of the steel. The thesis is focused on the application of the method of plasma cutting on high-strength steels. In the theoretical part of the present thesis, the common methods of cutting of steel and the plasma cutting technology are described. The parameters influencing the process of plasma cutting and their impact on the quality of the section are discussed. Furthermore, the concept of a heat-affected zone in the context of the plasma cutting method is concerned. The experimental part deals with the influence of plasma cutting on the hardness of certain types of high-strength steels. Three types of high-strength steels were used for the experiments: ARMOX 500 T, STRENX 650 MC E, and XAR®450. The sections were performed with two different cutting speeds. The size of the heat-affected zone and the hardness in the different areas of the section were evaluated. The results show that the plasma cutting is suitable for cutting of high-strength steels if appropriate parameters are selected. The influence of this method on the mechanical properties of certain high-strength steels is shown and discussed.
Study of properties of laser welds of Domex 460 MC material using arc preheating
Novotný, Michal ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
This diploma thesis deals with weldability of Domex 460 MC material. There are two welding methods and three other welded materials in heterogenous connection which will be researched in this diploma thesis. The welding methods are fiber solid-state laser and a new method of hybrid welding called laser – TIG. The other materials are Domex 700 MC, S355J2 and DC01. Domex 460 MC is a high-strenght steel with fine-grained structure. During the welding process the imput heat decreases mechanical properties of the materials. This effect is caused by material seeds growing. From these samples (which were produced by welding) were created metallographic cuts. These metallographic cuts were analysed focusing on their makrostructure, microstructure, mikrohardnest and Mn arrangement in welded heterogenous samples using electron microscope and EDX analysis.
Steel-Concrete Columns Composed of High-Strength Materials
Röder, Václav ; Štěpánek, Petr (referee) ; Studnička,, Jiří (referee) ; Vičan,, Josef (referee) ; Karmazínová, Marcela (advisor)
The main objective of this thesis is the verification of the buckling strength of the composite compression members which were made from high-strength materials. This thesis is divided into four main chapters which are interconnected. The first chapter summarizes the current state of the problem of the compression members. The basis of this part is the elementary theories and researches, the task of this text is attempted to understand and obtain normative procedures which are important for practical use. The second part deals with the theoretical analysis of composite column, mainly with the examination of the individual effects on the buckling strength. The result of the first and the second parts is analytical algebraic equations which determine the buckling strength of the member. The third part contains the numerical analysis, which leads to create a numerical model of the compression column. The numerical model is used for the verification of the theoretical analysis and for the investigation of the behaviour of the column loaded by axial force. The last part deals with the experimental verification of the previous analyses. There are tested various types of the composite columns, which were made of steel with a yield strength up to 455 MPa and of the concrete with a cube compression strength up to 102 MPa. Experimental results confirmed the high reliability of centrally loaded column and every tested columns failed by flexural buckling. The final step is evaluation and comparison of the results obtained from previous four parts. It was founded that design criteria for centrally loaded steel-concrete column are too conservative and design relationships doesn´t use the positive properties of high-strength materials for economic design.
Design of Conveyor Semi-Trailer
Nepovím, Ondřej ; Kovář, Stanislav (referee) ; Pokorný, Přemysl (advisor)
The first part of the thesis focuses on a research study of high-strength steels. The thesis also includes a conceptual design of the supporting structure of a transshipment trailer, which uses high-strength materials. This design is compatible with the Herkul trailer produced by the company NovaSteel s. r. o. and distributed by the sales network of Romill Brno, spol. s r.o. In its final part, the thesis deals with a stress analysis of the proposed design of the transshipment trailer. Stress-strength and deformation tests were carried out by means of the finite element method.

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