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Cracking of ferritic stainless steel tubes during production process
Majtás, Dušan ; Kreislová, K. ; Viani, Alberto ; Pérez-Estébanez, Marta ; Geiplová, H.
From the economic reasons many products originally made from austenite stainless steel are nowadays made from ferritic stainless steel. Ferritic steels have relatively low yield strength and the work hardening is limited. They cannot be hardened by heat treatment and only moderately hardened by cold working. Commercially made stainless steel tubes from ferritic steel, used for industrial plumbing was examined on presence of cracks. The cracking was present on the inner side of the convoluted tube shape. The tube manufacturing process consisted of continual bending of the sheet to tube shape, weld the tube, then of cold shaping by pulling through rib-forming frames, which is done in several steps. Then thermal treatment applies to the nearly finished product to remove stress remaining in the structure. Prime suspect was deformation beyond the ductility of used material. However the stress-strain tensile testing does not approved this hypothesis. Several samples of failed material were taken together with reference, and were examined by optical microscopy, and X-Ray Diffraction structure analysis. The structure of the cracked tubes does not show the signs of deformation over the limit, except the location near to the crack itself. Interestingly enough the failed material showed more homogenous structure than the original one. Needle like structures were found when the material is “overetched”, on these structures concentration of stress under bending occur. This structure was identified as δ-ferrite, however its presence in α-ferrite matrix is unclear.
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Influence of ice accretion at bridge rope on Strouhal number
Pospíšil, Stanislav ; Gorski, P. ; Kuznetsov, Sergeii
The paper is concerned with the method and results of wind tunnel investigations of the/nStrouhal number (St) of a stationary iced cable model of cable-supported bridges with/nrespect to different angles of wind attack. The methodology leading to the experimental/nicing of the inclined cable model was prepared in a climatic section of the laboratory./nThe St values were determined within the range of the Reynolds number (Re) between/n2.4·104 and 16.5·104, based on the dominant vortex shedding frequencies measured in/nthe wake of the model.
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The determination of material characteristics of natural and artificial stone samples from Marian Column at Hradčany Square in Prague
Slížková, Zuzana ; Zeman, Antonín ; Petráňová, Veronika ; Viani, Alberto ; Pérez-Estébanez, Marta ; Frankeová, Dita ; Ševčík, Radek ; Mácová, Petra ; Janotová, Dana ; Hasníková, Hana ; Niedoba, Krzysztof ; Hauková, Petra
Within the survey before restoration intervention material properties of natural and artificial stones that are part of the Marian Column at Hradcany Square in Prague were determined. 15 samples were subjected to extensive instrumental analysis, whose output is not only chemical and mineralogical composition of the samples, but also the degree of degradation including a description of the porous system and the level of salinity.
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Research Report on Condition Assessment of Wood-destroying Damage to Log Walls of a Landless Person's Cottage of Leskovec (orig. No. 70) and a Cottage of Lužná (orig. No. 28) now in the Museum in Rožnov pod Radhoštěm
Kloiber, Michal ; Hrivnák, Jaroslav ; Bláha, Jiří
The subject of the research report was to assess the condition of and identify the wood-destroying damage to the walls of a landless person's cottage of Leskovec and a cottage of Lužná, two log structures that are part of the exhibition at the Wallachian Museum in Rožnov pod Radhoštěm. The report focused on locating points, classifying the degree of damage, determining the extent of concealed attack by the means of non-destructive devices, specifying whether wood is subject to a fungal attack (mycological damage) or insect attack (entomological damage) and drawing the results obtained in the plan documentation. The report was based on direct and mediated visual observation using an endoscope and mainly on measurements taken using a resistance microdrilling device and also on ascertainment of mechanical properties of wood using expanding jaws in the borehole. Based on the results, specific procedures for rehabilitation measures were designed and elements designed for structural rehabilitation were marked in the drawing documentation.
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Research Report on Condition Assessment of the Holy Ghost Tower's Roof Frame in Telč
Bláha, Jiří ; Kloiber, Michal ; Frankl, Jiří ; Buzek, Jaroslav
The subject of the research report was to assess the condition of and identify the range of wood-destroying damage to the roof frame of the Holy Ghost tower in Telč focused on locating critical points, classifying the degree of damage, determining the extent of concealed attack by the means of non-destructive devices, specifying whether wood is subject to a fungal attack (mycology) or insect attack (entomology), including the drawing of the results obtained in the drawing documentation of the existing condition of the roof frame. Based on the results, specific procedures for rehabilitation measures were designed and elements designed for structural rehabilitation were included in the drawing documentation. The report is based primarily on direct and mediated (endoscopic) visual observations supplemented by measurements using a resistance microdrilling device.
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