FATIGUE ASSESSMENT OF CORRODED DECK LONGITUDINALS OF TANKERS

Fatigue life of deck longitudinals of oil tankers is analysed based on linear elastic fracture mechanics. A parametric formulation for the estimation of stress intensity factors and the Paris-Erdogan law are applied. Long-term effects of corrosion are modelled based on regression equations fitted to thickness measurements made during inspections of two tankers. Parametric studies are performed in order to investigate the importance of the governing parameters of crack propagation. A comparison of the fatigue analyses performed by linear fracture mechanics and S-N approaches is presented.

Determination of Mechanical and Fracture Properties of Silicon Single Crystal from Indentation Experiments and Finite Element Modelling

It is well-known that cracks are observed around the impression during indentation of brittle materials. The cracks inception depends on load conditions, material and indenter geometry. The paper aims to use experimental micro-indentation data, FE simulations with cohesive zone modelling, and an optimisation procedure to determine the cohesive energy density of silicon single crystals. While previous studies available in the literature, which use cohesive zone finite element techniques for simulation of indentation cracks in brittle solids, tried to improve methods for the evaluation of material toughness from the indentation load, crack size, hardness, elastic constants, and indenter geometry, this study focuses on the evaluation of the cohesive energy density 2Γ from which the material toughness can be easily determined using the well-known Griffith-Irwin formula. There is no need to control the premise of the linear fracture mechanics that the cohesive zone is much shorter than the crack length. Hence, the developed approach is suitable also for short cracks for which the linear fracture mechanics premise is violated.

Theory of Narrow U-Shaped Notches in Linear Fracture Mechanics

On the basis of linear fracture mechanics, a complete set of asymptotic formulas is obtained to describe the stress-strain state at the top of a narrow U-shaped notch. This type of defect can be possessed by a crack that has undergone a corrosive effect of the environment, or there can be a crack-like defect in a welded joint, e.g. lack of penetration, undercut, or a narrow slot in the part. To comparatively assess the risk of cracking at the tops of narrow U-shaped notches, and identify the places and directions of fracture initiation, we reveal the possibility of using such energy criteria as the deformation energy density and The previously indicated criteria were proposed by the author of this work for classical cracks-cuts. The purpose of this work was to study, on the basis of singular solutions of linear fracture mechanics, the stress-strain state in terms and near the tops of extremely narrow U-shaped notches, i.e., blunt cracks, in comparison with classical cracks-cuts

Traumatic acute epidural hematoma caused by injury of the diploic channels

Background: Traumatic acute epidural hematomas (EDHs) commonly develop by rupture of the meningeal arteries. EDH caused by an injury of the diploic channel (DC) has not been reported. Case Description: A 21-year-old man suffered a head injury while falling off the skateboard. At presentation, the patient was drowsy but did not exhibit any focal neurological deficits. Cranial computed tomography (CT) revealed a biconvex intracranial hematoma with 18-mm thickness in the high parietal region and a linear fracture that involved both the outer and inner tables and passed above the hematoma. A well-developed and large DC was observed near the hematoma. Patient’s consciousness level decreased at 12 h after admission with considerable growth of the hematoma. A frontoparietal craniotomy revealed an EDH. The dura mater and the meningeal arteries underneath the hematoma were intact. The medial bone cut caused brisk bleeds from the large DC. Postoperative CT revealed the cut of the DC and other finer DCs exhibiting air density and lying near the fracture. Based on these findings, we assumed that the EDH was developed by an injury of the DCs. Conclusion: Traumatic EDH can develop by an injury of the DCs. Careful observation of patient’s neurological status and precise interpretation of neuroimages is important to identify venous EDHs.

Nominal Stress-Based Estimation of Fatigue Life of Welded Joints

The paper presents methods for determining the fatigue life of welded joints with particular emphasis given to typical joints. In addition, the article presents various possible nominal stress-based ways enabling the calculation of stresses, including structural stresses and involving the most complex linear fracture mechanics. The paper also discusses recommendations by the International Institute of Welding related to the determination of the fatigue life of welded joints in flat elements exposed to tension-compression conditions. The work is focused on assessing the fatigue life of welded joints (selected types) in accordance with the guidelines specified in related recommendations issued by the International Institute of Welding and taking into consideration the analysis concerned with the safety of such structures.

Estimating probability of fatigue failure of steel structures

The article deals with the analysis of failure probability of the effect of random factors in uencing fatigue crack propagation in a steel element under bending moment. The theoretical model of fatigue crack progression is based on linear fracture mechanics. When determining the required degree of failure probability, it is possible to specify the time of the first inspection of the construction, which will focus on the fatigue damage. Using a conditional probability, subsequent inspection times are specified. The failure probability is examined using a fairly new sensitivity analysis subordinated to a contrast. The importance ranking of the input random variables to the failure probability is investigated. Fatigue properties of steel are taken from recent experimental research. Numerical results are obtained using the Monte Carlo simulation.

Probabilistic fatigue analysis of existing steel structure

The paper deals with evaluation of possible fatigue damage of existing steel crane structure. It is possible to use the some traditional methods to solve the problem - a concept of fatigue S-N curves (which are mainly used for designing of a new structures) or the procedures based on linear fracture mechanics utilizing the Paris-Erdogan’s law (which are suitable for estimation of remaining lifetime). For the resistance assessment the relevant data of load effects caused by cyclically loaded structure operation are necessary for both concepts. For the prediction of fatigue damage over time, calibration functions for short edge cracks were derived based on the results of the experiment, and the acceptable size of the fatigue crack in damaged structural component under analysis was determined. Using the derived relationships, a stochastic analysis of the selected element was performed and the results are discussed.