%0 Journal Article
%T Effect of Density and Pointed Corner Degree of Pore on Local Stress in Welded Structures: Defect in Marine Structures
%A Farida Bouafia
%A Boualem Serier
%A Nassim Serier
%A Sardar Sikandar Hayat
%J ISRN Mechanical Engineering
%D 2014
%R 10.1155/2014/834659
%X The process of assembly by welding, in marine structures, led to the creation of microstructural heterogeneities zones. Welded structures generally contain defects such as lack of penetration, slag inclusion, porosity, and misalignment. Generally these zones can be discontinuities geometrical. At the origins of stress concentration, these regions are favourable sites where fatigue cracks can initiate and propagate. In this study, the 3D finite element method is used to analyze the distribution of stress (strain) generated by the presence in the weld nugget of a pore formed during the welding process. This analysis was made in the matrix-pore interface. The effects of density and pointed corner degree of pore on the stress levels were also analyzed. 1. Introduction The major weld imperfections, in marine structures, include porosity, lack of penetration, lack of fusion, slag inclusion, undercut, misalignment, and so forth [1]. The size and frequency of imperfection depend on the welding process, weld procedure, geometry of weldment including ease of access for welding, and the care exercised in making the weld. These imperfections have different characteristics and, in most cases, are difficult and costly to detect and define nondestructively. These weld defects can significantly influence the local stress field in the vicinity of welds when the welded component is subjected to cyclic fatigue load. In most cases, weld defects lead to severe stress concentration and thus accelerate fatigue crack growth. In agreement with many authors, fatigue and fracture are the most critical failure mode of welded joints [2¨C4]. Hence, it is up of importance to study the stress distribution around these zones. This behavior is attributed to the fact that for a given fatigue life, a much larger embedded imperfection can be tolerated than a surface imperfections [5]. Different welds imperfections as described by Maddox [1] are shown in Figure 1. Figure 1: Different weld imperfections in a butt-joint [ 1]. Porosity is defined as cavity type discontinuities (voids) formed by gas entrapment during solidification. The shape of the void is dependent on the relative rates of solidification of the weld metal and the nucleation of the entrapped gas. The resultant stress field surrounding the pore depends upon the pore shape and the loading. Porosity, though generally spherical in shape, can assume many shapes and configurations. These include elongated pores, rows of single pore or collinear pores, and pore clusters. Determining the effects of various sizes and shapes of pores is
%U http://www.hindawi.com/journals/isrn.mechanical.engineering/2014/834659/