This diploma thesis deals with frame of the two-point crank press LKDS800, which was designed by company ŽĎAS a.s. Frame is welded construction creating the base of the press which has mass approximately 90 tonnes. Aim of this study was to perform strain-stress analysis of the frame. From obtained results perform optimization of mass this frame leading to reduce material costs and machining. In the process is frame loaded by nominal forces from the shearing process, under its own weight and inertia forces caused by moving components. As a result of the dynamic loading in welded joints there are risks of fatigue fracture. The manufacturer of the press is required to find the most loaded welded joint and it to assess the fatigue life.

Theoretical part of this master thesis is focused on the theory of fatigue life. The second part deals with the assesment of static strength the closing flap in front of water turbine. Futher fatigue analysis of the closing flap is performed considering corrosive environment. The aim is to verify the required service lifetime of 50 years.

This work describes the design of a dedicated three-rolls hydraulic bending for Hardox 500 without the possibility of bending sheet metal for the manufacture of pipes. The work will analyze the problem of proposed three-rolls bending, bending technology and creating of the pre-bending, the design of the adjusting hydraulic servo-cylinder, planetary gearboxes with hydraulic motors to drive the bottom rollers, a partial draft of the hydraulic circuit and the complete frame structure of bending machine with its covers.

Elaboration of design principles of steel joints. Creation of the finite element model in ANSYS program, the study of static behaviour near the bolt hole, deformation of the screw and the stress components of the welded joint. Comparison with the analytical formulas.

This diploma thesis deals with design load bearing steel structure of the sport stadium roofing with 82,8 m length and 29,0 m width. Roofing structure is designed and examined in two versions. Variant A is designed like tubular truss girder with axis distance 4,6 m. Variant B is designed like welded solid-web girder with same axis distance. These versions are compared by weight, manufacturing complexity and appearance, prefeable version is processed in detail. Drawings contain layout of both versions and manufacturing drawings of truss.

Ces travaux portent sur l'étude expérimentale et numérique de la rupture de structures soudées soumises à des sollicitations pyrotechniques telles que celles subies par les véhicules militaires sur le champ de bataille. Ce travail de thèse présente le développement de modèles éléments finis détaillés (à l’échelle mésoscopique) permettant de reproduire le comportement de ces assemblages lorsqu’ils sont sollicités par ces sollicitations dynamiques. Ils prennent en compte la géométrie locale des cordons de soudure et les différents matériaux. Pour paramétrer ces modèles, il est nécessaire de caractériser la soudure à l’échelle des matériaux constitutifs de l’assemblage. Ainsi des essais de caractérisation de leur comportement mécanique sont menés en se basant sur les vitesses de déformation relevées sur des modèles éléments finis de véhicule : quasi-statique jusqu’à 1000s-1. Pour l’analyse de la rupture, une large plage de triaxialité des contraintes est couverte au travers d’essais dédiés. Pour chaque matériau, une loi de comportement et un critère de rupture ont été déterminés par analyse inverse et validés sur des grandeurs globales et locales. Afin d’étudier la pertinence des modèles mésoscopiques, des essais au canon à gaz sont réalisés sur des assemblages soudés élémentaires en L et en T. Ils permettent de reproduire les principaux modes de rupture observés sur les pièces réelles. In fine, les simulations corrèlent les essais en termes de mode et de seuil d’apparition de la rupture. Ceci valide les lois de comportement identifiées et la modélisation mésoscopique proposée. / Finite element modeling is commonly used to design armored vehicles and to evaluate the strength of the structure against mine explosion. This study investigates experimental and numerical failure of welded structures submitted to such dynamic loadings. The goal is to develop detailed finite element models at meso-scale that allow to predict the behavior and failure of welded joints at intermediate strain rates. These models must take into account the local properties of the welded joint as the geometries as the mechanical behavior of the constitutive materials. Experimental characterizations of the material behavior are led on tensile specimens from quasi-static loading up to 1000s-1. This strain rates range results from analysis on vehicle finite element models. Dedicated tests are also conducted to study the material failure on a large range of stress triaxiality values. For each constitutive material, the hardening and failure parameters are identified through a reverse engineering approach. To validate the meso-scale models, gas gun tests are led on basic L and T welded assemblies. Modes and thresholds of failure are correctly replicated thanks to these finite element models. This validates the identified material behavior laws and the proposed meso-scale modeling.

The subject of the diploma thesis is design and structural analysis of the sports hall. The building is located in Pardubice city. The dimensions of a floor plan are 45,5 m x 30,0 m, the height is 13,0 m. There is a sport facilities unit adjusted to the construction. The dimension of such an object is 39,0 m x 10,0 m. The load-bearing structure consists of truss girders, which are pin-supported by fixed columns. The distance between main trusses is 6,5 m. The supporting part of the roof deck consists of solid-purlins. Space stability is ensured by cross bracing and longitudinal bracing. All bars are rolled steel profiles and are designed according to current ČSN EN standards. Steel S355 is used as the construction material. In this work is processed a structural design report of main elements including connections and drawing documentation.

The subject of this diploma’s thesis is design of the footbridge over Radlická street in Prague. Total length of the footbridge is about 90 m. Three variant designs were made with different systems of static construction. Based on the multi-criteria analysis, the most suitable variant was chosen. The variant A, a continuous truss beam, was chosen for detailed design. It is a truss footbridge with a lower orthotropic deck without a wind bracing. The stability of the upper chord is secured by frame stiffness of verticals and stiffness of the floor beam. Detailed static calculation includes assessment of load-bearing parts of the structure and assessment of welds. The structure is made of steel class S335. Assessment and dimensioning were designed according to valid standards ČSN EN 1990-1993.

No description available.

The following thesis is a study on the ability to create acceptable welds in thin-plate, ultra-high-strength steels (UHSS) by way of friction stir welding (FSW). Steels are welded together to create tailor-welded blanks (TWB) for use in the automotive industry. Dual Phase (DP) 590, 780, and 980 steel as well as Transformation-Induced Plasticity (TRIP) 590 steel with thicknesses ranging from 1.2 mm to 1.8 mm were welded using friction stir welding under a variety of processing conditions, including experiments with dissimilar thicknesses. Samples were tested under tensile loads for initial determination if an acceptable weld had been created. Acceptable welds were created in both TRIP 590 and DP 590 at speeds up to 102 centimeters-per-minute. No acceptable welds were created in the DP 780 and DP 980 materials. A series of microhardness measurements were taken across weld samples to gain understanding as to the causes of failure. These data indicate that softening, caused by both excessive heat and insufficient heat can result in weld failure. Not enough heat causes the high concentration of martensite in these materials to temper while too much heat can cause excessive hardening in the weld, through the formation of even more martensite, which tends to promote failure mode during forming operations. Laser welding is one of the leading methods for creating tailor-welded blank. Therefore, laser welded samples of each material were tested and compared to Friction Stir Welded samples. Lower strength and elongation are measured in weld failure while the failure location itself determines the success of a weld. In short, an acceptable weld is one that breaks outside the weld nugget and Heat Affected Zone (HAZ) and where the tensile strength (both yield and ultimate) along with the elongation are comparable to the base material. In unacceptable welds, the sample broke in the weld nugget or HAZ while strength and elongations were well below those of the base material samples.