The project elaborated within the engineering studies of the branch Manufacturing technology presents an experiment of welding of high strength steel by fiber laser. The project includes a theoretical study, which deals with the welding material properties, principles and types of lasers and laser welding technology. The practical part contains a verification of the welding parameters according to the standard ČSN EN ISO 15614-11. The final evaluation results of the experiment at the close of the project are presented.

The use of high-strength steel is more and more frequent in the car industry. I focused on USIBOR® 1500 steel welded by Nd-YAG laser. For my experiment, there were used various welding parameters and shielding gases. To compare the weld samples, I used the tensile, bending, macrostructure, microstructure and Vickers hardness test with different combinations of thickness as well as welded material.

Based on study of documents supplied by PWO Unitools a.s. and on advices of design office staff, tool for forming flanges was designed. This tool was then manufactured and it has been used for carrying test of creating flanges of various diameters from high-strength steels. During these tests, the following parameters were optimized – force of upper and lower blank holder and the height of the main guides. Threads were created into these drown flanges. These threaded joins were later tested for maximum torque and maximum compressive strength.

Although high strength steels represent yield strength up to 1300 MPa, welded structures reveal lowerstrength values. The strongest commercially available electrode provides the yield strength of about900 MPa. Therefore, in welded steels with strength above this type of filler metal, achieving anacceptable global strength is a crucial issue. In this master thesis, affects of different welding procedures on static strength of welded jointsof Weldox 960 and Weldox 1100 steels, were studied. These steels are produced by SSAB inOxelösund. Meanwhile, finite element method analyses were applied in order to investigatethe static strength behavior of such weldments under uniaxial tension. The welding parameters which were selected as variables are:  Heat input Weld joint geometry Filler metal When weld metal is undermatching in strength levels than the base material, by applyingtension the soft weld metal begins to deform before parent metal. At that point thedeformation of resulted soft zone, including the weld metal and the heat affected zone, ishindered by high strength parent metal. Thus, uniaxial stress caused by uniaxial load isconverted to multiaxial stress. This conversion in tension results in increase in the staticstrength of weldment. The increase in strength is emphasized by increase in the width of thewelded joint while the thickness of the plate is kept as constant. After experiments and performing FEM studies, it was revealed that the static strength ofWeldox 960 welded joints approaches towards the tensile strength of parent metal by increasein the width of the weldment. In Weldox 1100 joints; a slight increase in tensile properties ofthe weldments, when the width of the sample increases, was observed.

Thesis: B.S., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 1980 / Includes bibliographical references. / by Evan Joseph Hammerman. / B.S. / B.S. Massachusetts Institute of Technology, Department of Materials Science and Engineering

This research project has been undertaken to produce and characterize the behavior of High Strength Cementitious Mix (HSCM), which has considerably higher compressive strength compared to conventional concrete. Components of HSCM are cement, silica fume, sand, water, and high range water reducer. The material is tested for compressive strength and impact energy absorption capacity while the amount of above mentioned components are varied parametrically. The effect of these parameters are extensively studied and trends are reported. Finally, this research projects attempts to find correlations among compressive strength, compressive toughness, and impact toughness. Limitations of the experimental program are discussed and future direction for improvement and expansion of the research program is suggested.

This research is about modelling and simulation of how the hydrogen diffuses in high strength steels. The hydrogen diffusion in the material was examined by using finite element software with the help of material properties and some existing data. For modelling and simulating the diffusion analysis in finite element software, a cylindrical type dog-bone shaped specimen was chosen. To determine the diffusion at the centre of specimen, a cross-sectional area of the material was selected to proceed for the analysis. Abaqus software was considered as finite element software to progress the hydrogen diffusion and tensile testing of the specimen. Diffusion analysis was studied under the analogy of heat transfer and also, diffusion analysis with the addition of mechanical load was studied under the analogy of coupled temperature displacement in the Abaqus software. This process has executed for two types of high strength steels 316L and 304L stainless steels. The crack is also considered for analysis to check how it affects the specimen. Further, The 316L and 304L stainless steel results were compared to review that which steel is better to withstand the hydrogen diffusion rate and mechanical load on the material.

Concrete structures designed to meet blast criteria often require substantial increases in structural system size, weight, and cost when using conventional materials, but using higher strength materials may offer a way to mitigate these increases while achieving desired performance levels. The primary objective of this research is to investigate the performance of a high-strength Portland cement concrete, high-strength low-alloy vanadium (HSLA-V) rebar material combination that meets or exceeds blast resistance criteria while allowing a more efficient structural design than can be achieved using conventional materials. Twelve panels consisting of both single and double mat conventional Grade 60 rebar or HSLA-V rebar in combination with 4 ksi or 15 ksi concrete were tested using the ERDC quasi-static water chamber. Permission to publish this thesis was granted by the Director of the Geotechnical and Structures Laboratory and the U.S. Army Research Laboratory.

[pt] A utilização do concreto de alta resistência já é uma realidade e muitos países estão adaptando suas normas para levar em conta as propriedades deste material. No dimensionamento de pilares esbeltos e seções com concreto de alta resistência é importante observar a relação tensão- deformação adotada no cálculo, pois enquanto para o concreto convencional a deformação máxima, ecu, é 0,0035, para o de alta resistência esta deformação depende do valor da resistência do concreto, diminuindo com o aumento do fck. Para um concreto com fck = 80 MPa, por exemplo, ecu é em torno de 0,0022 de acordo com as relações tensão - deformação propostas pelo MC90-CEB. A relação tensão- deformação com ecu dependente de fck irá alterar os diagramas de interação adimensionais para o dimensionamento de pilares esbeltos e concreto de alta resistência. São construídos neste trabalho diagramas de interação força normal - momento fletor - curvatura (n,m,f) e força normal - momento fletor - índice de esbeltez (n,m,l) para o dimensionamento de pilares esbeltos e diagramas de interação (nd,md) e (nd,mdx,mdy) para o dimensionamento de seções submetidas a flexão composta reta e oblíqua. Adotou- se a relação tensão-deformação proposta pelo MC90-CEB e valores de fck de 50 a 80 MPa. Os diagramas para pilares esbeltos foram construídos com auxílio do programa PCFRAME (KRÜGER, 1989) e os diagramas para o dimensionamento de seções foram construídos com um programa desenvolvido neste trabalho. Através dos resultados, observa-se que, como ecu depende de fck, todos os diagramas de interação sofreram diferenças, podendo ser dito ainda que o uso dos diagramas já existentes, construídos com ecu constante e igual a 0,0035, pode conduzir a erros contra a segurança estrutural. / [en] The use of high strength concrete is already a reality and many countries are adapting their design codes to take into account the properties of this material. For the design of slender columns and sections subjected to combined axial force and bending, the most important property is the stress-strain relationship. While for normal concrete the strain at ultimate, ecu, can be considered constant and equal to 0,0035, for high strength concrete ecu depends on the concrete strength, decreasing as the strength increases. For a concrete with fck of 80 MPa, for instance, ecu is around 0,0022 according to the CEB Model Code (1990). Stress-strain relationship with ecu dependent of fck will affect the nondimensional interaction diagrams for the design of slender columns and sections of high strength concretes. Nondimensional interaction diagrams moment-axial load-curvature (m,n,f) and diagrams moment-axial load- slenderness ratio (m,n,l), for the design of slender columns, and nondimensional interaction diagrams (md,nd) and (nd,mdx,mdy) , for compression plus axial and biaxial bending of sections, are constructed in this work. The diagrams were constructed for concretes with strength between 50 MPa and 80 MPa, adopting suitable stress-strain relationships recommended by the CEB Model Code 1990. The diagrams for slender columns were constructed with the aid of an existing computational program developed in an earlier thesis, while the diagrams for the design of sections were constructed with a new program, specially developed in this work. The results have shown that all these diagrams are affected, even when presented in a nondimensional form, when stress-strain diagrams with ecu dependent of fck are adopted. The use of traditional nondimensional interaction diagrams, constructed with ecu constant and equal to 0,0035, may lead to errors against structural safety. / [es] La utilización del concreto de alta resistencia es una realidad actual y muchos países estan adaptando sus normas para tener en cuenta las propiedades de este material. En el dimensionamiento de pilares esbeltos y secciones con concreto de alta resistencia es importante observar la relación tensión-deformación que se adopta en el cálculo, porque mientras para el concreto convencional la deformación máxima, ecu, es 0,0035, para el de alta resistencia esta deformación depende del valor de la resistencia del concreto, diminuyendo con el aumento del fck. Para un concreto con fck = 80 MPa, por ejemplo, ecu es en torno de 0,0022 de acordo con las relaciones tensión - deformación propostas por el MC90-CEB. La relación tensión- deformación con ecu dependente de fck alterará los diagramas de interacción adimensionales para el dimensionamiento de pilares esbeltos y concreto de alta resistencia. En este trabajo se construyen diagramas de interacción fuerza normal - momento flector - curvatura (n,m,f) y fuerza normal - momento flector - índice de esbeltez (n,m,l) para el dimensionamiento de pilares esbeltos y diagramas de interacción (nd,md) y (nd,mdx,mdy) para el dimensionamiento de secciones sometidas a flexión compuesta recta y obliqua. se adoptó la relación tensión-deformación propuesta por el MC90-CEB y valores de fck de 50 la 80 MPa. Los diagramas para pilares esbeltos fueron construidos con auxilio del programa PCFRAME (KRÜGER, 1989) e implementamos un programa para obtener los diagramas para el dimensionamiento de las secciones. A través de los resultados se observa que, como ecu depende de fck, todos los diagramas de interacción sufren diferencias, y puede decirse que el uso de los diagramas construidos con ecu constante e igual la 0,0035, pueden conducir a errores que afectan la seguridad extructural.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24578号 / 工博第5084号 / 新制||工||1974(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 西山 峰広, 教授 聲高 裕治, 准教授 倉田 真宏 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM