Many critical elements of building and machine-building structures during their operation are in difficult operating conditions (high temperature, aggressive environment, etc.). In this case, they ...can be subject to a double effect: corrosion and material damage. Corrosion leads to a decrease in the cross-section of a structure, resulting in stress increase therein. In turn, damage to the material is accompanied by the appearance of microcracks and voids therein, due to inelastic deformation (creep), leading to a deterioration in its physical properties (for example, the elastic modulus) and a sharp decrease in the stress values at which the structure is destroyed. This article continues the study in the field of the optimal design of structures subject to the aforementioned double effect by the example of the optimization of plates with holes in the plane stress state, exposed to high temperatures (in previous works, the use of this approach was demonstrated in the optimization of the bending elements of rectangular and I-sections). Used as a corrosion equation is the modified Dolinsky mode, which takes into account the (additional) effect of the protective properties of an anticorrosive coating on the corrosion kinetics. Taken as a kinetic equation describing the change in material damage, is Yu. N. Rabotnov’s model, which enables to determine the duration of the incubation period of the beginning of the tangible process of material damage. To study the stress state of a plate, the finite element method is used. With a given contour of the plate, found is the optimal distribution of the thickness of the finite elements into which the given plate is divided. Acting as a constraint of the optimization problem is the parameter of damage to the plate material. The approach proposed in this work can be used to solve similar problems of the optimal design of structures operating under conditions of corrosion and material damage, using both analytical solutions and numerical methods.
Operation of structures in high temperature conditions and aggressive environments leads to such phenomena as corrosion and material damage. Corrosion leads to a reduction in structural cross-section ...and, consequently, an increase in stresses. As to material damage, namely, the appearance of micro-cracks and voids resulting from inelastic creep strain, it leads to a deterioration of physical characteristics (for example, the elastic modulus) and a sharp decrease in the stress values at which structural failure occurs. This paper is a continuation of the research in the field of optimal design of structures operating under conditions of corrosion and material damage (high temperature, aggressive environment, etc.). A first paper in this field was devoted to the optimization of bendable rectangular cross-section elements. This paper considers the optimization of the lengthwise thickness of flanges of bendable I-section elements, using the same principle of equal damage, which was applied to optimize the bendable rectangular cross-section elements. It is assumed that the flange width and web height of an I-section element are fixed. Since, during bending, mainly I-beam flanges work (their moment of inertia is 85% of the moment of inertia of the entire cross-section), the web is not taken into account in the calculation. As an equation of corrosion, V. M. Dolinsky’s model is adopted, taking into account the effect of tension on the corrosion wear of structures. In the model of the kinetic equation that describes the change in material damage, Yu. N. Rabonov’s model is adopted, where the value of damage ω varying from 0 to 1 is taken to be a variable parameter. As the criterion of optimality, the minimum weight of structures is adopted. In conclusion, presented is an algorithm for solving a more complete problem of optimizing the parameters of bendable I-section elements, namely, the web height and the flange width, using the obtained analytical expressions that determine the optimal distribution of the thickness of flanges along the length of the structure.
The prevailing view in international jurisprudence is that no one can claim compensation for the fact of being alive. This view was developed based on so-called ‘wrongful life’ cases, in which, due ...to medical malpractice, parents were deprived of the opportunity to perform a legally permitted abortion, resulting in the birth of a disabled or unwanted child. A new chapter in this category of claims was opened by the case under review. The German Supreme Court took up what, in view of the ageing of Western societies, is a very topical and socially difficult issue of a son’s claim for damages for keeping his father alive. The ruling concerns a special category of civil claims so far not commented on in Polish literature or jurisprudence – ‘wrongful survival’. The German Supreme Court rejected the possibility of claiming compensation under German law for prolonging human existence, even if it involved suffering. Much of the reasoning of the Court is also applicable under Polish law. However, depending on the interpretation of the norms concerning the patient’s right to self-determination, the possibility of partial compensation for the costs of unlawfully keeping someone alive also seems to be acceptable under Polish law.
During operation, many of the critical elements of building and engineering structures are in difficult operating conditions (high temperature, aggressive environment, etc.). In this case, they may ...be subject to a double effect: corrosion and material damage. Corrosion leads to a reduction in the cross-section of a structure, resulting in stress increase therein. In turn, the damage to the material is accompanied by the appearance of microcracks and voids therein due to inelastic deformation (creep), which leads to a deterioration of physical characteristics of the material (for example, elastic modulus) and a sharp decrease in the stress values at which the structure is destroyed. This paper considers the optimization of bending rectangular cross-section elements operated in conditions conducive to the appearance of both corrosion and material damage. As the equation of corrosion, the model of V. M. Dolinsky is taken. This model takes into account the effect of stresses on the corrosion wear of structures. As a kinetic equation describing the change in material damage, the model of Yu. N. Rabotnov is used. The optimality criterion is the minimum mass of the structure. The height of the rectangular cross-section bending element along its length is optimized using the principle of equal damage at the final moment of the lifetime of the structure. The proposed approach can be used to solve similar problems of the optimal design of structures operating in conditions of corrosion and material damage with the use of both analytical solutions and numerical methods.
Active infrared thermography is a fast and accurate non-destructive evaluation technique that is of particular relevance to the aerospace industry for the inspection of aircraft and helicopters' ...primary and secondary structures, aero-engine parts, spacecraft components and its subsystems. This review provides an exhaustive summary of most recent active thermographic methods used for aerospace applications according to their physical principle and thermal excitation sources. Besides traditional optically stimulated thermography, which uses external optical radiation such as flashes, heaters and laser systems, novel hybrid thermographic techniques are also investigated. These include ultrasonic stimulated thermography, which uses ultrasonic waves and the local damage resonance effect to enhance the reliability and sensitivity to micro-cracks, eddy current stimulated thermography, which uses cost-effective eddy current excitation to generate induction heating, and microwave thermography, which uses electromagnetic radiation at the microwave frequency bands to provide rapid detection of cracks and delamination. All these techniques are here analysed and numerous examples are provided for different damage scenarios and aerospace components in order to identify the strength and limitations of each thermographic technique. Moreover, alternative strategies to current external thermal excitation sources, here named as material-based thermography methods, are examined in this paper. These novel thermographic techniques rely on thermoresistive internal heating and offer a fast, low power, accurate and reliable assessment of damage in aerospace composites.
Hydrogen could gradually replace fossil fuels, mitigating the human impact on the environment. However, equipment exposed to hydrogen is subjected to damaging effects due to H2 absorption and ...permeation through metals. Hence, inspection activities are necessary to preserve the physical integrity of the containment systems, and the risk-based (RBI) methodology is considered the most beneficial approach. This review aims to provide relevant information regarding hydrogen embrittlement, its effect on materials’ properties, and the synergistic interplay of the factors influencing its occurrence. Moreover, an overview of predictive maintenance strategies is presented, focusing on the RBI methodology. A systematic review was carried out to identify examples of the application of RBI to equipment exposed to hydrogenated environments and to identify the most active research groups. In conclusion, a significant lack of knowledge has been highlighted, along with difficulties in applying the RBI methodology for equipment operating in a pure hydrogen environment.
•The occurrence of hydrogen-induced material failures requires safety enhancements.•Hydrogen embrittlement relies on a synergistic interplay of several factors.•Tailored inspection activities could aid to monitor equipment exposed to hydrogen.•RBI approaches are not used for planning inspections of hydrogen technologies.•Material science and safety are often considered two separated research fields.
•A thermo-mechanical coupled PD model for ECC-concrete bonding specimens.•Within the PD framework, models for ECC and concrete as well as their interface model are constructed.•Considering the ...degradation of mechanical and thermal properties under high temperature.•The damage of ECC-concrete bonding specimens under fire scenarios are analyzed.•The flow and heat transfer of thermos fluids are modeled using PDDO.
The current application of Peridynamics (PD) models in addressing thermally induced failures within Engineered Cementitious Composites (ECC) and concrete bonding specimens is relatively limited. This study introduces a novel semi-discrete PD model for ECC and a random heterogeneous PD model for concrete. These models are grounded in the microscopic constitutive relationships between ECC and concrete materials and incorporate the strain softening behavior of cement-based materials. The effectiveness of the interface model is evaluated through splitting tensile tests on ECC-concrete bonding specimens, employing a series model alongside PD surface effects for material interface correction. Considering the performance degradation of materials at elevated temperatures, a PD thermo-mechanical coupling model, which integrates PD thermal diffusion and motion equations, is proposed to analyze the failure of ECC and concrete under high thermal loads. The validity of both the thermo-mechanical coupling and concrete heterogeneity models is confirmed via thermal cracking tests on heated concrete columns subjected to drilling. Lastly, considering the dynamic response of fire, the Navier-Stokes equation are reformulated into a non-local form utilizing the Peridynamic differential operator (PDDO) to simulate fire environment. A thermo-fluid-mechanical coupling model is developed, and applied to analyze ECC and concrete bonding specimens’ failure behaviors under fire scenarios.
•A thermo-mechanical coupling PD model for non-homogeneous concrete.•Taking into account the degradation of mechanical parameters and thermal properties at high temperatures.•The damage of ...heterogeneous concrete due to the thermal flux caused by fire.•The flow and heat transfer of the thermal fluid are modeled by using PDDO.
A coupled thermo-mechanical bond-based peridynamical (PD) method is developed to simulate thermal cracking processes in concrete. Based on the bond-based PD heat conduction and motion equations, the PD differential operator (PDDO) is used to express the classical computational fluid dynamics basic equations in a non-local integral form, establishing a PD model for the thermo-mechanical coupling problems. In this model, concrete is considered a heterogeneous material composed of aggregates and mortar, with material parameters assumed to be temperature-dependent. The multi-rate explicit time integration scheme is proposed to overcome the multi-scale time problem in coupled thermo-mechanical systems. The model is applied to simulate the transient heat transfer problem of a homogeneous plate. The results show good agreement with the analytical solution, providing evidence for the correctness and accuracy of the proposed coupled numerical method. The damage behavior of the borehole heated concrete plate is analyzed, followed by the simulation of the damage to the concrete plate under a fire scenario. The numerical results accurately predict the temperature distribution within the heterogeneous concrete and the resulting material damage. This study provides new theoretical basis for the fire resistance design and high-temperature performance improvement of concrete materials and structures.
A boiling liquid expanding vapor explosion (BLEVE) is one of the most serious accidents which generates overpressure and ejected fragments with potential great impact on the safety of the tank area. ...Hence, it is important to reveal the dynamic characteristics of the axial crack propagation at the top of the horizontal tank in a BLEVE accident. The rupture behavior of tanks under one-step BLEVE accidents is investigated and the detailed dynamic characteristics of crack opening angle and crack propagation rate were assessed through the small-scale BLEVE experiments with variations in tank wall thickness and filling levels. An extended Gurson-Tvergaard-Needleman (GTN) model was proposed to calculate the dynamic damage of the tank during the rupture process. The dynamic stress-strain damage characteristics of the tank during the one-step BLEVE process and the circumferential transformation mechanism of the axial crack were explored. Based on an analysis of the material damage and the size characteristics of the tank structure, criteria were proposed for judging whether the direction of crack growth will change.
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