National Repository of Grey Literature 134 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Use of laser-TIG hybrid technology for boron-doped high-strength steels
Kachlíř, Jaromír ; Šebestová, Hana (referee) ; Mrňa, Libor (advisor)
This thesis deals with the usage of arc preheating for welding high strength boron enhanced steel 22MnB5 using hybrid technology known as laserTIG and also its impact on the final weld compared to welds welded by only the laser or the arc method. During the experiment I welded five sheets of the above mentioned steel 1,3 or 1,9 milimeters wide. Except for the welds fabricated by the laser and the TIG method was the only variable the electric current of the arc (I = 20, 40, or 60 A). Welds welded this way were compared based on strength limits measured by the tensile tests. Additionally were they compared according to the metalographic survey and the progress of weld hardness, calculated using the Vickers hardness test.
Comparison of the of precision manufacturing of holes during laser cutting of materials on various types of CNC cutting centers
Petruška, David ; Dostál, Jan (referee) ; Mrňa, Libor (advisor)
The thesis compares the precision of 90x90 mm laser cutouts with circular and quadrangular holes which are divided into two CNC cutting centers with different axle drive types. On both machines, the samples are cut through both oxidative and fusion cutting. Measurement was carried out using a sliding scale and for a more detailed and accurate analysis on a 3D coordinate measuring machine with a touch system. The results of the measurements showed that the more suitable cutting method for sheet metal cutting CSN 11321 DC01 is melting. Deviations of the nominal dimensions are comparable when cutting on both machines, so the choice of the machine for production speeds, operating and acquisition costs depends on the serial production of these burners.
Use of laser-TIG hybrid technology for welding of different materials used in power engineering
Žák, Tomáš ; Beran, David (referee) ; Mrňa, Libor (advisor)
Thesis is focused on analyzing the influence of preheating process parameters using electric arc from TIG torch during laser welding on weld properties of stainless steel and carbon steel with higher strength. In this thesis experiment was done in which metal sheets 3 mm thick from X12Cr13 and S355 steels were welded. Welding was done first with using only laser, then laser with TIG preheating and lastly laser with preheated material by induction heater. When TIG preheating was used than set welding current was changed on the power source. The welds were subsequently evaluated based on macrostructure, microstructure and Vickers hardness test.
Service life increasing of spare part tools for ground cultivation
Černín, Jiří ; Mrňa, Libor (referee) ; Sigmund, Marián (advisor)
This diploma thesis deals with increasing the service life of parts intended for soil cultivation. The work evaluates the current possibilities of increasing the utility value of spare parts. Practical tests will provide recommendations for the most appropriate method to increase durability. The work examines uncharted methods of testing soldered joint. The results are evaluated in terms of quality and economic profitability. All results from this work are based on the basis of practical tests of plowing machine in rocky soil.
Dependence of fillet weld seam geometry in laser welding with wobbling on stainless steel
Vaverka, Jiří ; Horník, Petr (referee) ; Mrňa, Libor (advisor)
Laser welding is one of the most developing methods of connecting materials and that’s the reason, why it is necessary to explore all possibilities of this method. This bachelor thesis is focused on laser welding of fillet welds with wobbling on stainless steel. Five testing pieces were made with different diameters of wobbling circles. Study of dependence of seam geometry on welding parameters was executed on these welds.
Use of laser-TIG hybrid technology for welding aluminium alloys
Drápela, Petr ; Šebestová, Hana (referee) ; Mrňa, Libor (advisor)
Different problems arise from choice of setting technological parameters during welding of alluminium alloys. Choice of welding method, welding speed and material influence mechanical properties of welds. During welding of alluminium alloys come difficulties due to oxidation of thin surface layer of material. One of ways how to overcome this obtacle is to use hybrid laser-TIG welding method. In this diploma thesis is described influence of welding processes on mechanical properties of two alluminium alloys(EN AW-5754 H22, EN AW-6082 T6) and change in their microstructure during welding.
Study of the influence of process parameters on welding properties of ferritic stainless steel in laser oscillation welding
Křepela, Petr ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The aim of this work was to carry out an experiment to assess the influence of the individual welding parameters in the laser welding method with the beam wobbling on the made weld, respectively. welds. The material which was welded was ferritic stainless steel with the designation 1.4016, which, like all ferritic steels, is susceptible to coarse grains and the resulting brittleness which leads to degradation of the mechanical properties of the weld. The welds were compared to a sample welded without wobbling an between themselves. Unfortunately, however, the evaluation of the test samples did not bring significant differences from laser welding without wobbling, however some changes are evident, such as grain orientation, weld defects, or uniformity of mechanical properties over the weld length, where wobbling frequency is most important. Further research should focus on limiting the porosity at higher wobbling frequencies in the shape of a circle or ellipse.
Study of the influence of process parameters on welding properties of ferritic stainless steel and carbon steel in laser oscillation welding
Rýznarová, Martina ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
In the thesis, the influence of the shape of the beam wobbling geometry and the spot vibration frequency on the properties of the heterogeneous weld of X12Cr13 martensitic stainless steel with carbon steel S355MC in laser oscillation welding is investigated. Macroscopic control was performed on the samples, which were focused on weld size and heat affected areas, weld defects, weld shape and cant / drop face and weld joint root. Subsequent microscopic inspection determined both the weld metal structure and the heat affected area and base material. The last was a Vickers microhardness test. Based on the experiment, it was found that the spot process frequency is an important process parameter.
Study of the influence of process parameters on welding properties of ferritic stainless steel and carbon steel in laser oscillation welding
Hála, Kamil ; Sigmund, Marián (referee) ; Mrňa, Libor (advisor)
The Master thesis is focused on the influence of procedural parameters on the properties of heterogeneous weld in laser welding. The literature review section offers an overview of the industrial application of the laser welding technology as well as it explains the issue of heterogeneous weld creation. The experimental part of the thesis aims to describe how six carbon steel samples have been welded together with ferritic stainless steel by usage of several different beam oscillation configurations. Tested samples have been used to create trial ensembles that were subjected for a tension testing, Vickers hardness testing, metallographic testing and corrosive resistant testing. As a result of the experiment, there is a suggestion of the study that could be used for an industrial using of a combination of these materials.
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.

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