Jožef Predan (Author), Nenad Gubeljak (Author), Maks Oblak (Author), Janko Legat (Author)

Abstract

Standardi in dokumenti za določitev hitrosti širjenja razpoke predvidevajo uporabo standardnih preizkušancev, na katerih je mogoče meriti dolžino razpoke od nekaj deset do nekaj sto milimetrov prirastka. Problem postaja težaven pri zvarnih spojih, kadar se merijo prirastki razpoke na skupni razdaljile nekaj milimetrov. Za to so poglavitni razlogi naslednji: utrujanje poteka z relativno nizko amplitudo faktorja intenzitete napetosti v področju utrujenostnega praga, mikro strukturna in trdnostna heterogenost zvarnega spoja, zaostale napetosti kot posledica varjenja, med utrujanjem se način odpiranja razpoke lokalno spreminja iz enoosno nateznega na ravninsko strižno in nasprotno. Omenjeni dejavniki se kažejo z izrazito neurejeno sliko hitrosti širjenja utrujenostne razpoke. V prispevku je opisan postopek za predobdelavo eksperimentalno izmerjenih vrednosti (prirastek razpoke, št. nihajev), ki omogoča zanesljivejšo določitev hitrosti širjenja utrujenostne razpoke v zvarnem spoju za majhne prirastke do zloma, ko faktor intenzitete napetosti preseže lomno žilavost.

Keywords

zvarni spoji;utrujenostna razpoka;faktor intenzivnosti napetosti;prag;

Data

Language: Slovenian
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UM FS - Faculty of Mechanical Engineering
Publisher: Inštitut za kovinske materiale in tehnologije Ljubljana
UDC: 621.791.05:620.178.3:539.55
COBISS: 7482390 Link will open in a new window
ISSN: 1580-2949
Parent publication: Materiali in tehnologije
Views: 1610
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Other data

Secondary language: English
Secondary title: Determining the fatigue crack growth rate in welded joints for small fatigue crack extension
Secondary abstract: Standards and documents for determining crack growth rate envisage the use of standard specimens on which it is possible to measure the length of a crack from around ten to around a hundred millimeters. The problem becomes difficult in welding joints in the case when a crack length increment is measured on the total distance of just a few millimeters. The main reasons are follows: - the fatigue is performed at a relatively low amplitude stress intensity level in the region of the threshold; - the microstructure and the strength heterogeneity of the welding joint; - the residual stresses as an effect of welding a consequence of the welding process; - the local change of load modes from one-axis tensile stress to plane shear stress and vice versa. The above-mentioned factors are reflected in the results with a clearly disarranged dependence on fatigue-crack growth rate. This paper outlines a procedure for the pre-processing of experimentally measured values (crack-length increment, number of cycles) to make it possible to more reliably determine fatigue-crack growth rate in the welding joint for a low crack-length increment.
Secondary keywords: welded joints;fatigue crack;stress intensity factor;threshold;
URN: URN:NBN:SI
Type (COBISS): Scientific work
Pages: str. 201-206
Volume: ǂLetn. ǂ36
Issue: ǂšt. ǂ5
Chronology: 2002
ID: 1747558