Finite element analysis of fracture resistance parameters for stationary semi-elliptical surface cracks in high strength steel

This study deals with numerical simulations based on elastic-plastic finite element method for nonlinear stress analyses on pre-cracked tensile specimens with high strength properties. The influence of crack geometry on fracture resistance properties is considered with numerical analysis on models with two different cracks. Results on fracture resistance parameters are obtained for both simulated tensile panels with different crack lengths and width, referred as short and long crack. The obtained numerical results for crack resistance behaviour of tensile specimens are compared with data results from existing experimental investigations on specimens with same shape and material properties. Also, comparison is made with results obtained from similar standard experimental procedure. It is shown, that a proper combination of numerical and experimental procedures can lead research to significantly accurate results when investigating the fracture response of materials

Finite element analysis of fracture resistance parameters for stationary semi-elliptical surface cracks in high strength steel

This study deals with numerical simulations based on elastic-plastic finite element method for nonlinear stress analyses on pre-cracked tensile specimens with high strength properties. The influence of crack geometry on fracture resistance properties is considered with numerical analysis on models with two different cracks. Results on fracture resistance parameters are obtained for both simulated tensile panels with different crack lengths and width, referred as short and long crack. The obtained numerical results for crack resistance behaviour of tensile specimens are compared with data results from existing experimental investigations on specimens with same shape and material properties. Also, comparison is made with results obtained from similar standard experimental procedure. It is shown, that a proper combination of numerical and experimental procedures can lead research to significantly accurate results when investigating the fracture response of materials

Numerical simulation for studying constraint effect on ductile fracture initiation using complete Gurson model

Nastanak žilavog loma u zavarenim spojevima niskolegiranog čelika povišene čvrstoće je predviđen primenom mikromehaničkog kompletnog Gursonovog modela (CGM). Ograničeno deformisanje oko vrha prsline (eng. 'constraint') i promena troosnosti napona u ligamentu su razmatrani na epruvetama za savijanje u tri tačke SE(B) i na kompaktnim epruvetama za zatezanje C(T), uzimajući u obzir uticaj razlike u mehaničkim osobinama (eng. 'mismatch') i širine metala šava. Analizirana je prenosivost parametra koji odgovara nastanku prsline, u zavisnosti od troosnosti napona ispred njenog vrha i zaključeno je da se dobijene vrednosti korišćenog parametra mogu koristiti za obe geometrije razmatrane u radu.Ductile fracture initiation in high-strength low alloyed welded steel joints is predicted using micromechanical complete Gurson model (CGM). The crack tip constraint and variation of stress triaxiality in ligament are considered on single-edge notch bend SE(B) and compact tension C(T) specimens, including the effect of strength mismatching and different weld metal width. According to the analysis of stress triaxiality in front of the crack tip, transferability of fracture initiation parameter was studied. As a result of the analyses on specimens, fracture initiation parameter determined by using CGM can be transferred from one geometry to another if their triaxial conditions are found to be similar

Micromechanical modelling of ductile fracture - local approach

Micromechanical modelling of ductile fracture by using the local approach has been presented as the review of previously obtained results for welded joints made of low alloyed high strength steel. Experimental work was performed on 3PB specimens and tensile panels, which were then modelled by finite element method, using two- and three-dimensional meshes, respectively. The local approach was used to simulate both for crack initiation and growth during ductile fracture process

An overview of application of micromechanical models in ductile fracture analysis of welded joints

Fracture of welded joints has been an important research and industrial topic for a long time, having in mind the key role of welded joints in ensuring the safe operation and integrity of welded structures. This work contains an overview of application of micromechanical models to ductile fracture of welded joints. The main benefit of these models, in comparison with the classical fracture mechanics approach, is consideration of the local quantities (stress and strain) in prediction of damage development. The damage is quantified through the value of the damage parameter, which is typically related to the void nucleation, growth and coalescence for ductile fracture of metallic materials, i.e. the description of the material can be related to the actual material behaviour during fracture. Most of the presented studies, including those published by the present authors, are performed on steel as the base material, and the rest deal with aluminium alloys

Micromechanical modelling of ductile fracture – local approach

Micromechanical modelling of ductile fracture by using the local approach has been presented as the review of previously obtained results for welded joints made of low alloyed high strength steel. Experimental work was performed on 3PB specimens and tensile panels, which were then modelled by finite element method, using two- and three-dimensional meshes, respectively. The local approach was used to simulate both for crack initiation and growth during ductile fracture process

Integrity assessment of vital beam components that enable conjoint operation of two bridge cranes

Vital components of the beam that enable conjoint operation of two bridge cranes are braces and threaded spindle. The beam connects two bridge cranes with overall lifting capacity of 500 t (2 x 250 t) and enables their simultaneous conjoint operation during the rehabilitation or major overhaul of hydroelectric generating set equipment at the hydro power plant ''Djerdap 2'. Two braces are being installed instead of two hooks when this situation occurs. The threaded spindle is loaded with 500 t (5 MN), while braces are loaded with 250 t (2.5 MN) each. Integrity of structures is a relatively new scientific and engineering discipline which in a broader sense comprises condition analysis, behaviour diagnostics, service life evaluation and rehabilitation of structures, which means that beside the usual situation in which it is necessary to evaluate the integrity of a structure when a flaw is detected by means of non-destructive tests, this discipline also comprises stress condition analysis for the crackless structure, most often through the use of finite element method. This is the way to obtain precise and detailed distribution of displacements, deformations and stresses, which enables determination of weak spots on the structure, even before crack initiation. Non-destructive tests are performed in order to analyse the current condition of braces and the threaded spindle. On the basis of performed analytical calculations it is determined that the integrity is not threatened, although some internal non-homogeneities are detected by ultrasonic testing