Закономерности синтеза нанодисперсных оксидов меди электролизом на переменном токе в растворе щелочи

Показана возможность получения оксидов меди с высокой площадью удельной поверхности электролизом металлической меди с использованием переменного тока промышленной частоты. Изучены параметры, оказывающие влияние на скорость образования оксидов. Определён фазовый состав и характеристики пористой структуры продуктов электросинтеза в зависимости от режимов проведения процесса

Zum Zusammenwirken hochfester Baustoffe in Verbundträgern

When construction elements made of steel and concrete are connected this is called composite construction which has been investigated very intensely since 1930. The greatest steps in the development of this type of construction were made when the headed stud shear connector was introduced, the slim floors were launched and the high-strength materials were utilized. The coaction of high-strength steel and high-strength concrete in composite girders with solid slabs for building construction and the impact on the bearing- and the deformation-behaviour are researched in this thesis based on tests and numerical calculations. In addition to that the design of a new single push-out test allowed the systematic investigation of the behaviour of one single stud shear connector under pure shear loading. The thesis is structured as follows: * Tests with nine composite girders under positive and negative moments for the determination of the ultimate bearing capacity and ductility. * Push-out tests with 62 specimens in order to describe the bearing- and the deformation-behaviour of headed studs in high-strength concrete. * Proposal of a new design method for headed studs in high-strength concrete which allows for a resistance of the welded collar and a resistance of the stud’s shank. * Parametric study to find ways to increase the ductility of headed studs in high-strength concrete. * Critical interpretation of the Standard push-out test as given in Eurocode 4 based on numerical studies. * Development of a procedure to correct the plastic design with regard to the stress-strain distributions of the high-strength materials. * Systematic investigation of the longitudinal shear stress distribution subjected to stiffness- and loading-conditions. * Formulation of new limits for the minimum degree of longitudinal shear connection depending on the span length, the loading and the cross section with regard to the low ductility of the connectors in high-strength concrete. Based on the new perceptions practical design rules are proposed, which allow an economic use of high-strength materials in composite construction. Promising applications are highly loaded components in industrial and bridge constructions. Future investigations regarding high-strength materials in composite structures should include the bearing behaviour of shear connectors under dynamic loads, the further development of numerical methods to simulate the material behaviour of the concrete and the bearing behaviour of partially or totally concrete encased steel members

Zum Zusammenwirken hochfester Baustoffe in Verbundträgern

When construction elements made of steel and concrete are connected this is called composite construction which has been investigated very intensely since 1930. The greatest steps in the development of this type of construction were made when the headed stud shear connector was introduced, the slim floors were launched and the high-strength materials were utilized. The coaction of high-strength steel and high-strength concrete in composite girders with solid slabs for building construction and the impact on the bearing- and the deformation-behaviour are researched in this thesis based on tests and numerical calculations. In addition to that the design of a new single push-out test allowed the systematic investigation of the behaviour of one single stud shear connector under pure shear loading. The thesis is structured as follows: * Tests with nine composite girders under positive and negative moments for the determination of the ultimate bearing capacity and ductility. * Push-out tests with 62 specimens in order to describe the bearing- and the deformation-behaviour of headed studs in high-strength concrete. * Proposal of a new design method for headed studs in high-strength concrete which allows for a resistance of the welded collar and a resistance of the stud’s shank. * Parametric study to find ways to increase the ductility of headed studs in high-strength concrete. * Critical interpretation of the Standard push-out test as given in Eurocode 4 based on numerical studies. * Development of a procedure to correct the plastic design with regard to the stress-strain distributions of the high-strength materials. * Systematic investigation of the longitudinal shear stress distribution subjected to stiffness- and loading-conditions. * Formulation of new limits for the minimum degree of longitudinal shear connection depending on the span length, the loading and the cross section with regard to the low ductility of the connectors in high-strength concrete. Based on the new perceptions practical design rules are proposed, which allow an economic use of high-strength materials in composite construction. Promising applications are highly loaded components in industrial and bridge constructions. Future investigations regarding high-strength materials in composite structures should include the bearing behaviour of shear connectors under dynamic loads, the further development of numerical methods to simulate the material behaviour of the concrete and the bearing behaviour of partially or totally concrete encased steel members