Experimentálne stanovenie únavového vrubového súčiniteľa napätia pre vzorky z ocele s355 zvárané technológiou MIG

Joining components by welding is the most widespread method of joining for metal structures. For this reason, fatigue strength assessment of welded joints is of great interest to engineers involved in structure design. The welded joint itself can be considered a notch composed of a technological (inner deffects and material inhomogenities) and a geometrical (surface irregularities) part. Due to stress and strain concentration, such a notch decreases fatigue endurance of a welded construction. This paper shows experimental quantification of the fatigue stress notch factor for butt welded joints manufactured by MIG technology.Technológia zvárania je pri kovových konštrukciách najrozšírenejšou metódou spájania konštrukčných častí. Z tohto dôvodu je problematike posudzovania únavovej životnosti zvarových spojov venovaná zvýšená pozornosť strojných inžinierov. Na zvar ako taký možno pozerať ako na vrub pozostávajúci z technologickej (vnútorné chyby a nehomogenity materiálu) a geometrickej (povrchová členitosť) časti. Tento vrub vplyvom koncentrácie napätia a deformácie znižuje únavovú odolnosť konštrukcie. Obsahom tohoto príspevku je kvantifikácia únavového vrubového súčiniteľa napätia pre tupý zvar vyhotovený technológiou MIG

Health and Structural Integrity of Monitoring Systems: The Case Study of Pressurized Pipelines

In the operation of some structures, particularly in energy or chemical industry where pressurized pipeline systems are employed, certain unexpected critical situations may occur, which must be definitely avoided. Otherwise, such situations would result in undesirable damage to the environment or even the endangerment of human life. For example, the occurrence of such nonstandard states can significantly affect the safety of high-pressure pipeline systems. The following paper discusses basic physical prerequisites for assembling the systems that can sense loading states and monitor the operational safety conditions of pressure piping systems in the long-run. The appropriate monitoring system hardware with cost-effective data management was designed in order to enable the real-time monitoring of operational safety parameters. Furthermore, the paper presents the results obtained from the measurements of existing real-time safety monitoring systems for selected pipeline systems. Document type: Articl

Experimental Quantification of the Fatigue Stress Concentrator on Mig Butt Welded S355 Steel Specimen

Joining components by welding is the most widespread method of joining for metal structures. For this reason, fatigue strength assessment of welded joints is of great interest to engineers involved in structure design. The welded joint itself can be considered a notch composed of a technological (inner deffects and material inhomogenities) and a geometrical (surface irregularities) part. Due to stress and strain concentration, such a notch decreases fatigue endurance of a welded construction. This paper shows experimental quantification of the fatigue stress notch factor for butt welded joints manufactured by MIG technology

The assessment of the tensile with torsion loading interaction using the selected hypotheses and the experiment

For two steels with different material properties (both cyclic and static ones) were experimentally obtained dependencies σa=f(Nf) and σa=f(Nf). The specimens of these materials were loaded with multiple tensile and torsion stress combinations. It was found out that the time-depending relationship between the individual stresses was proportional. The results for steel with high ration of Rm/Re are different comparing to the results of the second material. In this contribution, there will be confronted the experimentally obtained fatigue life-time magnitudes with selected multiaxial fatigue life-time hypotheses like Findley, McDiarmid, Dang-Van, Carpinteri-Spagnioli, and Margetin-Ďurka-Chmelko

Heat treatment process effect on the fatigue properties of selected steels

PING 2019 is organized with the support of funds for specific university research project SVK1-2019-002.Heat treatment of steels is a technological process used to increase the strength of steels. There is a wide variety of different heat treatment procedures. The choice of a suitable technological process depends mainly on the chemical composition and the target properties of the material being processed. The relatively less explored area is the effect of heat treatment on the cyclic properties of steels. The paper will present the results of cyclic tests on two different steels. Cyclic properties of C55 steel will be analysed before and after heat treatment procedure. For high strength steel 34CrNiMo-6, the effect of the heat treatment process itself on the resulting cyclic loading properties will be analysed. Experimental results will be supported by microstructure analysis of investigated materials

Notch effect of welded joint

In general, the welded joints are multifactorial notches. This study is focused to separate the geometrical influence (when the weld can be seen on the surface) and technological factors (internal defects of the weld, structural changes of the material and residual stress) on its fatigue life. Proposed methodology of this separation comes out from the cyclic test of three specimens – group with existing weld, group without weld joint (base material) and another group where was removed outer geometry of the weld

Vliv procesu tepelného zpracování na únavové vlastnosti vysokopevnostní oceli

Tento článek je věnován analýze statických a cyklických vlastností dvou vysoce pevných ocelí (AS 4340). Důvodem této analýzy byla potřeba vybrat vhodné materiály pro energetiku. Analyzované materiály měly prakticky stejné chemické složení. Proces tepelného zpracování deklarovaný v inspekčním certifikátu byl také velmi podobný. Měřením mechanických vlastností byly určeny rozdíly ve statické pevnosti a zejména v cyklických vlastnostech srovnávaných materiálů. Pro vysvětlení významných rozdílů v únavových vlastnostech mezi materiály bylo nutné analyzovat jejich mikrostrukturu. Výsledky ukázaly, že relativně malá změna v procesu tepelného zpracování má významný vliv na únavové vlastnosti.This paper is devoted to the analysis of static and cyclic properties of two high strength steels (AS 4340). The reason for this analysis was the need to select suitable materials for the power engineering. Analyzed materials had a practically identical chemical composition. The heat treatment process declared by the inspection certificate was very similar too. By the measurements of mechanical properties there were differences in static strength and especially in cyclic properties of compared materials. To explain the significant differences in fatigue properties between materials, it was necessary to analyze their microstructure. The results have shown that a relatively small change in the heat treatment process has a significant effect on the fatigue properties of the steel

Notch effect of welded joint

In general, the welded joints are multifactorial notches. This study is focused to separate the geometrical influence (when the weld can be seen on the surface) and technological factors (internal defects of the weld, structural changes of the material and residual stress) on its fatigue life. Proposed methodology of this separation comes out from the cyclic test of three specimens – group with existing weld, group without weld joint (base material) and another group where was removed outer geometry of the weld

Safety margin against the fatigue fracture under random loading

The fatigue lifetime of the structure in operation is express in the number of working cycles, kilometers or time depending units. By harmonic process of loading is possible to express the safety margin as reserve against the required lifetime in the form of number cycles or amplitude of loading. By nonharmonic character of loading process in operation is difficult to express the level of safety margin as the reserve of loading (safety margin in loading). On the case of towing trailer will be discussed more ways of expression the reserve (safety margin) of structure against the fatigue fracture for required fatigue lifetime. For experimental acquired loading process in the most loaded cross-section will be discussed concept of determination of the level safety as reserve in the form of loading parameters. In the case, when the peaks of loading process exceeding the material yield stress (in the most loaded point of the structure) will be discussed concept of expression of loading in the form of time-varying process of strain. By using the cyclic material properties obtained in mode with controlled total strain is possible the safety margin to express also as the multiple of process loading parameters

Safety margin against the fatigue fracture under random loading

The fatigue lifetime of the structure in operation is express in the number of working cycles, kilometersor time depending units. By harmonic process of loading is possible to express the safety margin as reserve against the required lifetime in the form of number cycles or amplitude of loading. By non-harmonic character of loading process in operation is difficult to express the level of safety margin as the reserve of loading (safety margin in loading). On the case of towing trailer will be discussed more ways of expression the reserve (safety margin) of structure against the fatigue fracture for required fatigue lifetime. For experimental acquired loading process in the most loaded cross-section will be discussed concept of determination of the level safety as reserve in the form of loading parameters. In the case, when the peaks of loading process exceeding the material yield stress (in the most loaded point of the structure) will be discussed concept of expression of loading in the form of time-varying process of strain. By using the cyclic material properties obtained in mode with controlled total strain is possible the safety margin to express also as the multiple of process loading parameters