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An influence of prestress by combined random loading
Svoboda, Jaroslav ; Balda, Miroslav ; Fröhlich, Vladislav
The contribution deals with findings concerning an influence of static load in combination with random dynamic torgue on fatigue life of tube specimens made out of the steel ČSN 411523.1. A generalized formula has been found for fatigue life expressed in a number of loading blocks of torgue process as a function of its standard deviation. It joins both components of the combined loading in one expression. The formula yields very precise estimates of fatigue lives.
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An influence of normal static prestress on fatigue life construction by torsional random loading
Fröhlich, Vladislav ; Balda, Miroslav ; Svoboda, Jaroslav
Definition influence static prestress on fatigue life for case that uniaxial harmonic loading is in literature enough noted and isn't problem influence those components to the calculation of life constructional whole include. Complicated is it in the event of multiaxial loading of different character and especially in cases, when has this loading random character. In the workplace CDM in Pilsen we are already on basis results for Skoda Power Inc . implementation few experiments on piped figure with opening, loading combination normal and torsional load, during which time one of the applied load was election constant and second are harmonic with zero mean value dynamically impact. Along competitive examinations we watcht place of rice cracks.
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Properties of thermo-visco-elastic material 42-809 for manufacturing of vibrodamping elements – 3.part
Svoboda, Jaroslav ; Pešek, Luděk ; Frölich, V. ; Klášterka, Petr
In the report the results of rubber elements properties made of thermo-visco-elastic material 42-809 at low temperatures are summariesed. The tests were performed by a loading fatigue machine INSTRON 8502 in a climate chamber. For improving an accuracy of measurement the test machine was equipped with a lesser force transduser Rumburk with a range up to 40kN. The report includes results of static and dynamic characteristics in temperature range 0 ÷ -50°C, measurement of residual deformations, relaxation time and evaluation of a cyclic loading influence to shapes of static characteristics of the rubber. Furthermore the results of rubber element life time and evaluation of friction behaviour at lower temperatures are presented. The limit lines for 10% of residual deformations are drawn here, too.
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Fatigue strength and life of real structures under combined random loading
Svoboda, Jaroslav ; Balda, Miroslav ; Fröhlich, Vladislav
A rather often kind of combined stress is a case, when one of its components acts statically. The contribution deals with some rsults of research works,the goal of which has been to reveal an influence of the static component on a resulting fatigue life, and to find a way of its including into fatigue strength evalutions. A procedure for finding a critical stress for an estimating of a structure save life is presented. Unfortunately, the fatigue life calculation is more complicated and needs some experiments, which will yield additional informstion on a material behaviour under required stress combination and levels.
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