Fracture mechanics and fatigue life assessment of box-shaped welded structures : FEM analysis and parametric design

• In this study, Linear Elastic Fracture Mechanics (LEFM) approach is used to evaluate the fatigue strength of a box-shaped welded structure. A parametric study is also undertaken to study the effect of various weld parameters on the fatigue strength, such as lack of weld metal penetration, load position, and plate thicknesses. FRANC3D software was adopted to obtain the stress intensity factor values for two types of full-length and intermediate crack sizes, located at the critical region of the weld of the box-shaped structure. It was concluded that the LEFM approach could capture the crack propagation from the weld root reasonably well under the given conditions and estimate residual fatigue life of the welded structures conservatively. Compared to fatigue life estimations by nominal stress method (1,714,564 cycles) or effective notch stress method (63,385 cycles), the LEFM approach can estimate the residual life more accurately. Especially for intermediate (4 mm) lack of penetration (LOP) of weld metal case (589,198 cycles) in comparison to the experiments (1,216,595 cycles). The parametric study showed that the fatigue life increases with increase in the thickness of flanges, lesser LOP in the weld root, and when load is applied more toward the center of the plate. 

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Bearbetnings-, yt- och fogningsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Manufacturing, Surface and Joining Technology (hsv//eng)

Nyckelord

Fatigue crack growth

Finite element method

Linear Elastic Fracture Mechanic

Stress intensity factor

Welded structures

Cracks

Fracture mechanics

Plate metal

Plates (structural components)

Welding

Welds

Box-shaped structures

Effective notch stress

Fatigue life assessment

Fatigue life estimation

Lack of penetration

Linear-elastic fracture mechanics

Nominal stress methods

Residual fatigue lives

Fatigue of materials

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