Procedia Structural Integrity最新文献

The proposed computational model for crack propagation in high-temperature creep in metallic materials under the influence of a hydrogen environment and neutron irradiation is based on the first law of thermodynamics and the balance of the rates of change of energy components for an elementary crack propagation act in a metallic body under long-term static loading, high temperature, hydrogen-containing environments, and neutron irradiation. The application of the model for determining the residual life of bodies with cracks under the mentioned loading conditions in specified operational conditions is demonstrated using an analogy to Griffith’s problem, which represents a two-dimensional problem for thin-walled structural elements.

The potential of employing nanostructured metallic multilayer to increase the durability and extend the service life of welded joints of metal structures is analyzed. Using a nickel and copper-based multilayer nanocoating as an example, a notable increase in the durability of the welded joint of up to 300...600% is observed. Corrosion tests reveal that the use of nickel and copper nanostructured metallic multilayer leads to the localization of corrosion processes at the "base metal-nanocoating" boundary. Considering the significant improvement of fatigue characteristics of welded joints and lower corrosion rate compared to welds without lamination, Ni-Cu nanocoatings can be used on offshore structures, provided that the condition of the protective anti-corrosion coating is monitored to mitigate the risk of galvanic corrosion at the base metal-nanolamination boundary.

The organization of the movement of freight trains in Ukraine is an important factor in integrating the country’s railway transport into the European system. A situation that requires a significant renewal of the freight wagon park with modern wagons to meet the freight transportation requirements has arisen. Also, a significant drawback of railway transport in Ukraine is the limitation of the speed of trains, which include freight wagons with a reduced container in an empty state, therefore, at the moment, the issue of improving the methodological and software and instrumental testing tools for evaluating the quality and safety indicators of the movement of such wagons is relevant at the moment. At present, laboratory wagons are used during field tests related to the evaluation of traffic quality indicators, acceptance and admission to operation of railway rolling stock, but the modern state of development of measuring equipment allows in most cases to abandon the use of such wagons during running tests of units rolling stock in favor of mobile hardware and software complexes.

This study deals with the evaluation of corrosion resistance and other utility properties of selected austenitic nodular cast irons and their comparison with other (non-austenitic) nodular cast irons. For the investigations, two types of austenitic nodular cast iron were selected: nickel-manganese nodular cast iron EN-GJSA-XNiMn13-7 and nickel-chromium nodular cast iron EN-GJSA-XNiCr20-2. Basic mechanical properties, such as yield strength, tensile strength, elongation, absorbed energy and hardness, were evaluated using mechanical tests. The fatigue limit was determined using low-frequency fatigue tests. Corrosion properties, such as average corrosion rate, corrosion potential and corrosion current density, were determined by the exposure immersion test and the electrochemical potentiodynamic polarisation test. Both corrosion tests were performed in a 3.5% NaCl solution (to simulate seawater) at room temperature. The results of mechanical, fatigue and corrosion tests show that austenitic nodular cast irons have lower strength and fatigue properties but significantly higher plastic properties and corrosion resistance compared to non-austenitic nodular cast irons.

Fracture mechanics plays a crucial role among the mechanisms causing damage, meant as capacity fade, in lithium-ion batteries. Mechanical stresses arise in the electrode active material particles because of the interaction of lithium ions with electrode microstructure during battery operation. The stresses lead to fractures growth in the electrode, which accelerates detrimental chemical reactions. In this work, a modelling approach is presented to assess the fracture level in the electrode microstructure, evaluating the influence of the current delivered by the battery, and electrode design characteristics, such as the electrode thickness, the electrode active material fraction and the size of the electrode micro-particles. The results show that stress intensity factor linearly increase with the current delivered by the battery. Furthermore, thicker electrodes, greater active material fraction and greater electrode micro-particles represent a more detrimental condition from the fracture mechanics point of view. The results provide a practical electrode design guideline for electrode manufacturing, especially for choosing the right particle size in the electrode powder, the electrode thickness and its composition to limit fracture according to the current expected to be delivered by the battery.

Modular construction has gained popularity for its cost-effectiveness, time savings, and environmental benefits. This research delves into innovating modular buildings to enhance their aesthetic value in contemporary architectural designs. Traditional rectangular modules have lost architectural significance in the modern era. The study focuses on the failure mechanisms of hexagonal intra-module connections under nonlinear static analysis, aiming for advanced structural design and performance in modular construction. The study tested a control model, a Welded Flange Bolted Web (WFBW) connection, and three variations with different parameters: boundary condition, bolt arrangement, and steel grade. For the boundary condition, the tie constraint between the beam's flanges and the diaphragm was removed. Bolt arrangement was assessed with staggered and non-staggered bolts. Steel grade variations included S275 and S355. Results showed that the WFBW connection outperformed the Bolted Web (BW) connection in load resistance. The most damaged component was the beam, with bearing failure at the upper bolt hole. Non-staggered bolts exhibited larger displacements than staggered bolts. The study emphasized the significance of steel material strength in terms of stress and strain on bolt capacity. It highlights the importance of intra-module connections in modular steel structures and the need to consider design parameters carefully. The findings offer insights into improving modular connections' performance and failure mechanisms, facilitating the creation of aesthetically pleasing and structurally sound modular structures. This nonlinear static analysis aids in developing advanced modular construction designs, enhancing architectural significance in the modern era. By merging structural performance and aesthetics, the study promotes innovative modular construction to meet contemporary architectural demands.

T-joint has an important function in the lightweight structure to connect and transfer loading from one component to the other component. Failure analysis of the T-joint is necessary to obtain the optimum geometry. Since experiments require complex preparation and large costs, numerical modeling is needed to reduce the number of experiments that must be carried out. Numerical modeling in this study was performed to observe the failure modes of foam-core sandwich T-joint under low velocity impact loading. Three failure modes were considered in the current model: delamination, core crushing, and core shearing. To capture these failure modes, traction-separation response and ductile damage were implemented in the adhesive layer and foam material, respectively. The validation process was carried out by comparing the simulation results with experimental results from the literature. The simulation results showed similar failure modes as the experimental results from the literature, which confirms that the parameters used in the current numerical were accurate.

The slurry-infiltrated fiber-reinforced cementitious composite (SIFRCCs) material used to show much greater flexural strength and fracture toughness than normal cement concrete. By using these performance, the SIFRCCs could be applied for the blast resistant structures such as military purpose structures. However, most gas explosions are accompanied with fire afterward so that these high fracture toughness material needs high temperature resistance simultaneously. The SIFRCCs in this study contains fibers up to 5% by volume fraction. In addition, polymer powder was incorporated into SIFRCCs in order to enhance the fire resistance. The flexural strength and fracture toughness were compare with respected to the variation of polymer powder content, 0%, 0.5%, 1.0% and 1.5%. Powder polymer create capillary pores due to melting and burning when exposure to high temperature and minimize the vapor pressure inside the concrete model and reduces the failure of the concrete model. Specimens were covered with single layer of basalt sheet to study the flexural properties of SIFRCCs with basalt fiber sheet. The flexural strength and toughness of the specimens were investigated before and after the high temperature exposure per ISO 834 standard fire curve.

This paper presents a robust artificial neural network (ANN) loss function in solving samples with questionable data. The Latin hypercube sampling and the uniform experimental design are used as sample generation while ANN with various loss functions is the limit state function approaching method and Monte Carlo simulation is the failure probability computing technique. A marine lubricating oil cooler under a plus-minus triangular wave and internal pressure (1Mpa) is considered as representative of the dynamic implicit model. Three kinds of questionable data are considered: tiny vibrations(±δ₁) caused by the surrounding environment, small deviations caused by equipment error(±δ₂), and large deviations(±Δ) caused by accidental events. And two small probability events are considered: 1. Surrounding error + positive equipment error + a large shock (±Δ) in partial samples; 2. Surrounding error + negative equipment error + a large shock (±Δ) in partial samples. ANN with advanced loss function performs better than traditional loss function in dealing with samples including incorrect data.

Engineering structures, such as bridges, wind turbines, airplanes, ships, buildings, and offshore platforms, often experience uncertain dynamic loadings due to environmental factors and operational conditions. The lack of knowledge about the load spectrum for these structures poses challenges in terms of design and can lead to either over-engineering or catastrophic failure. This research introduces a robust and innovative device, analogous to a "Fitbit" for structures, capable of measuring complex loading conditions throughout the structure's lifespan. The proposed approach involves developing a middleware, referred to as an "extension," which facilitates the transfer of mechanical deformation to a piezoelectric sensor. This approach overcomes challenges associated with directly attaching piezoelectric sensors to the structure's surface such as rupture possibility in higher strain and attaching on rough surfaces. The feasibility study primarily focuses on validating the performance of the extension and monitoring variation trends. The ultimate objective is to develop an Internet of Things (IoT) sensor node capable of measuring applied cyclic loads. To achieve this goal, an electronic system and embedded software will be developed to capture the complex load spectrum and convert it into a fatigue damage index for predicting the structure's fatigue life. The collected data will be transmitted to the user through a wireless communication platform. The proposed sensor design is versatile, allowing for both attachment and embedding and is demonstrated here for monitoring fatigue in engineering structures.