The paper presents experimental results of the characteristics of strength and fracture toughness of the material from the different zones of welded joints made of different participation of the linear welding energy. Strength characteristics and fracture toughness were determined in the weld material, in the area of fusion line, in the material of the heat affected zone and in the base material

The paper presents the results of two butt welded joints by conventional method. The welding process was performed using a variety of linear welding energy. The studies included experimental and computational part. In experimental studies determined the distribution of hardness and mechanical properties of the individual analyzed sections of welded joints. The data obtained were intended to determine the extent of zones in the welded joints that have certain strength characteristics. Also conducted uniaxial tensile tests of welded joints with the registration of displacement fields on the surface of specimens by means of Aramis video-system what the final result are images of strain fields map on the surface of welded joints. The resulting strain values were compared with the results of numerical computations FEM.

This paper presents a strength analysis of joints made during high-strength steel S960 welding. Joints obtained by conventional and laser welding were tested. The most attention was focused on assessing the strength of the material at Heat Affect Zone (HAZ). To this aim, the effect of Linear Welding Energy (LWE) on changes in microstructure and material characteristics was studied. Numerical models of welded joints were developed using the FEM ABAQUS program. The modelled joints were subjected to simulation loads, which allowed to determine areas (the weakest links) of joints in which the destruction process may develop. Good compatibility of the strains fields on the outer surfaces of the joints calculated numerically and recorded by means of the GOM video system was obtained. Based on the tests carried out, it can be concluded that the use of welding with low levels of LEW allow obtaining joints with comparable strength to the base material.

This review paper discusses the basic problems related to the use of cohesive models to simulate the initiation and development of failure in various types of engineering issues. The most commonly used cohesive zone models (CZMs) are described. Recent achievements in the field of cohesive modeling are characterized, with particular emphasis on the problem of mixed mode loading, the influence of the strain rate, the stress state triaxiality, and fatigue. A separate chapter of the work is devoted to the identification of cohesive parameters. Examples of the use of CZMs for the analysis of the fracture and failure process in various applications, both on the macro and microscopic scale, are given. The directions of CZMs development were indicated as well as the issues that are currently under particularly intensive development.

Fracture toughness is a structural elements property. Critical values of the J - integral, JIC measured according to the standards requirements, when transferred to engineering applications can lead to a significant conservatism in assessing integrity of a structure. In the article the formulae to estimate the fracture toughness taking into account the in-plane constraint in elements are proposed. These formulae are based on the analysis of the stress field in front of the crack proposed by Hutchinson, Rice and Rosengren (HRR), and O'Dowd's, Shih's modifications of HRR field, as well as the analysis of the stress field in front of the crack, computed numerically.