Methods for Solving a Stress Behaviour of Welded Joints under Repeated Loads

Page 1

Mechanics, Materials Science & Engineering, May 2016

ISSN 2412-5954

Methods for Solving a Stress Behaviour of Welded Joints under Repeated Loads 1, a

1, b

1

Department of Aviation Technical Studies, Technical University of Kosice, Faculty of Aeronautics, Slovakia

a

karol.semrad@tuke.sk

b

jozef.cernan@tuke.sk DOI 10.13140/RG.2.1.5113.9440

Keywords: finite element analysis (FEA), factor of Safety for fatigue stresses (FSF), factor of safety for static stresses (FS), the stress ratio (R), the experimental maximum stress at R=0 (S0), slope of experimental curve (m), allowable maximum stress (f), equivalent stress (feq), bending stress (fb), shear stress (fs), yield strength (fy).

ABSTRACT. The article processes issue of strength of cyclically loaded welded joints with a focus on fillet welds. The y and from articles by Lehigh University and the University of Illinois in USA. The practical application of the solution is presented for crane car body to crawler connection.

Introduction. The paper deals with the design of structural members subjected to repeated loads. The design of fillet welded connections is included and emphasized. The practical application is presented for crane car body to crawler connection. Fatigue strength of fillet welded connections. The fatigue strength of fillet welds depends on the type of connection in which the weld is used; for example, the fatigue strength of a fillet welded lap joint is much lower than the fatigue strength of fillet welded flange to web connections in fabricated beams. Hence, data must be obtained for specific types of fillet welded connections rather than for fillet welds in general. The fatigue strength of fillet welded flange to web connections in a fabricated member is less than the fatigue strength of the base metal from which the member is fabricated, and cannot be increased significantly by using larger fillet welds. Fatigue data presently available from continuously fillet welded tee specimens loaded axially at the centroid of the tee cross section so that axial stresses but no shear stresses are developed, indicate that such longitudinal flange to web fillet welded connections have fatigue strength equal to, or greater than, transversely groove welded joints with the weld reinforcement in place. This comparison is for welds made in the same steel subjected to equal fatigue lives. Therefore, it is conservative to design longitudinal fillet welded joints subjected to repeated normal stresses only (axial or bending stresses without shear stresses) by the same formulas used to design transversely groove welded joints with the weld reinforcement in place [1]. The available fatigue data on flange to web fillet welds under combined stresses indicate that it is reasonable to design such welds subjected to combined bending and shear stress for the following equivalent stress, feq:

(1) where fb and fs - are the bending and shear stress present, respectively (feq - should be given the same algebraic sign as fb). The maximum and minimum values of fb and fs caused by given loading may be MMSE Journal. Open Access www.mmse.xyz

128


Turn static files into dynamic content formats.

Create a flipbook
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.