Procedia Structural Integrity最新文献

In this paper, the modelling strategies of Fluid-Structure Interaction impact simulation between amphibious aircraft float structure and water are investigated. Fluid-structure interaction in the form of constant velocity hydrodynamic impact was numerically modelled using finite element software by employing the coupled Eulerian-Lagrangian method. Four types of modelling strategies of the float, i.e., (1) full shell, (2) full solid, (3) multi-stage multi-scale, and (4) concurrent multi-scale modelling, are implemented and compared to obtain the most accurate model to obtain stress distribution on the float structure components. The modelling procedure and the advantages and disadvantages of each strategy are discussed comprehensively. The results show that the simulation using the structure modelled as shell elements is the most accurate strategy to obtain stress distribution on the float structure components while the solid elements model is the worst since the stresses predicted by using this model is lower than that of the shell elements model, especially when insufficient elements in the thickness direction is used. The multi-stage multi-scale in terms of shell-to-solid sub-modelling can be an alternative strategy since the results are similar to that using the shell geometry model. The concurrent multi-scale modelling, on the other hand, predicts acceptable stress values with a reasonable computational resource while maintaining computational accuracy and efficiency.

A theoretical consideration of the damping problem in frame engineering structures made of functionally graded materials with non-linear viscoelastic behaviour is carried-out. The frames studied are under external mechanical load and varying temperature. In particular, damping in a two-legged frame with supports on different levels is analyzed. The frame is subjected to a cyclic side load with simultaneous variation of the temperature. The material of the frame is functionally graded in the thickness direction. Thus, the material properties change smoothly along the thickness. Equilibrium equations are used for determining the curvature and the neutral axis coordinates in the members of the frame structure. The damping energy density is integrated in the volume of the frame members in order to find-out the damping energy in the whole frame structure. A parametric investigation is performed by using the solution of the damping energy in order to clarify the influence of various factors (the frame geometry, loading, etc.) on the damping phenomenon at different temperatures.

The paper addressed the challenge of minimizing the scattering of initial parameters in the limit state of a welded truss under the complex influence of design, technological, and operational factors. Methodologically, this objective was accomplished through a combination of full-scale, small-scale, and computer simulation experiments. The conducted experiment yielded mechanical properties of the A570-36 steel batch, displaying significantly lower dispersion of values compared to state standards and material quality certificates. Additionally, the mechanical properties of the welded samples were determined through small-scale force and computer simulation experiments on the 600x120 welded truss physical model. The computer simulation results demonstrated a reliability level of 94.6%. By compiling an input information array from the mechanical properties indicators of A570-36 steel and utilizing finite element model parameters, the simulation of the limit state parameters for a full-scale welded truss measuring 18000x3600 mm was executed. This process provided numerical, graphical, and visualized information on the truss’s limit state parameters, including maximum stresses and strains, along with their localization. Based on the research findings, a structural and technological solution was proposed to enhance the truss’s strength by 8.4%.

In the paper, there were presented the studies of the process of Ni-based specimens fatigue fracture by means of registration of the AE parameters in various frequency bandwidths. There were investigated the samples made of the high-temperature strength vacuum-arc-melted Ni-alloy. During the fatigue tests the count rate of AE signals were recorded simultaneously in three frequency bands. The experimental results have shown that the specimens having various processing inheritance, being tested on different load levels of high-cycle fatigue, had identical type of the AE count rate distribution. The specific changes of the AE count rate in various frequency bandwidths determine the certain stages of the fatigue failure.

The article presents the test outcomes on the dynamic performance of protective steel-reinforced concrete slabs. These results have been verified and demonstrate the viability and effectiveness of utilizing high-strength, fast-hardening concretes in their production. The use of high-strength concrete enables a reduction in plate thickness by 2 to 3 times compared to conventional concrete grades. PC Lira can be used to a limited extent for modeling shock effects on reinforced concrete structures by applying impulse loads, as it does not have the ability to use the shock interaction of different bodies with the penetration of one into another.

Corrosion problems in offshore wind power plants are a significant contributor to operation and maintenance (O&M) costs, typically around 15–30 percent of the total life cycle costs. Corrosion can degrade the structural material, contribute to fatigue cracking, brittle failure, and unstable failure, and the integrity of the entire structure can be significantly compromised. In the literature, there are many numerical simulations of the growth of pits and cracks in seawater under the influence of mechanical loads. Computer modeling allows quick assessment of the corrosion processes development; however, most software packages have limitations when building models. To study the corrosion processes of wind power plants, it is suggested to use modeling in COMSOL Multiphysics followed by its correction using experimentally measured electrochemical parameters in order to quickly assess the impact of changes in environmental parameters on the speed of corrosion processes and to identify areas of the structure that require additional protection and regular monitoring. In the future, combining field and experimental studies with computer modeling of corrosion processes is necessary.

Considered means of the typical and composite open wagon bodies repair, which will prevent the possible loss of bulk cargo and increase the level of the train traffic safety. Defects of open wagon bodies were identified and analyzed. Malfunctions and damage to wagon bodies are diverse and depend on the operating conditions of the wagon and its design features. The most typical malfunctions for all types of wagons are cracks, holes, deflections, dents, corrosion damage to metal parts and rotting of wood, as well as damage to the fastening parts of door sides, hatch covers, bodies. Considered technical requirements for nodes and parts of freight wagons in operation. Malfunctions of bodies and frames of freight wagons were analyzed. When designing highly loaded parts with complex geometry, the application of combined solutions is considered. Typical and prospective (composite) designs of open wagon bodies were also considered. The work examines the equipment for the repair of typical and composite open wagon bodies. The wagon repair machine for operational depots VRM-E, which is designed for mechanization of production, current uncoupling repair of freight wagons at the PTO and is designed to correct defects in the open wagon bodies, the considered open wagon tilter is mobile, which is designed for positioning the body of the open wagon in two directions in the conditions of wagon repair depots and wagon-building enterprises. Installation for fixing the upper binding frame of open wagons that can be used in wagon repair depots. Installation which is intended for correcting all major types of deformations of the upper binding frame of an open wagon, installation of straightening the side walls of the body of the open wagons. Calculations for the strength of the semi-wagon body in the empty state under repair loads were also conducted.

This paper analyzes the hydrogen assisted microdamage (HAMD) region in high-strength eutectoid pearlitic steel on the basis of slow strain rate tests (SSRT) on axisymmetric round-notched samples under hydrogen embrittlement environmental conditions. The use of very different notched specimens and their associated stress and strain distributions in the vicinity of the notch tip allows a study of local triaxiality effects on hydrogen embrittlement of the round notched samples, as well as the important role of the hydrostatic stress state on hydrogen diffusion and micro-cracking (or micro-damage). The microscopic appearance of the hydrogen-affected region –the so-called tearing topography surface (TTS)– resembles micro-damage, micro-cracking or micro-tearing at a micro- or nano-scale due to hydrogen degradation, thereby affecting the notch tensile strength of the specimens and producing the phenomenon of hydrogen embrittlement/degradation. A micromechanical model is proposed to explain these hydrogen effects on the material on the basis of the lamellar micro- and nano-structure of the pearlitic steel under consideration.

Sleepers are railway elements subjected to demanding working conditions and strict structural requirements. The acceptance procedures proposed by standard EN 13230-2 for concrete sleepers include the execution of a sequence of static 3-Point Bending Tests. In each step, the maximum applied force is increased by a pre-fixed amount. As a main crack is detected, the corresponding width and residual opening displacement are measured. This kind of testing was performed in previous research work, monitoring fracture propagation by Digital Image Correlation (DIC). This contribution considers a different experimental setup and procedure, consisting of a 4-Point Bending Test with a continuous loading-unloading process. The deformation of the central portion of the sleeper, subjected to uniform bending, and the fracture pattern are monitored by DIC also in this case. The results demonstrate the substantial equivalence of the two alternative approaches compared here for the evaluation of the in-service mechanical performance of these structural elements.

Comprehensive research was conducted to assess the feasibility of repairing CuZn37 brass products using the Tungsten Inert Gas (TIG) welding process. Standard welding wires designed for copper and its alloys (4 wire grades) were used as filler materials. The research on the macro- and microstructure of the weld joints revealed that the recrystallization region did not exceed 2 mm. The single-phase α-solid solution structure was characteristic of the welds made with CuSn4Zn3 filler wire. Microhardness measurements of the welds and the heat-affected zone showed significant softening up to 22-25 mm from the weld axis due to the thermal influence of the welding process on cold-rolled brass.

As a result of the comprehensive research, a fundamental technology for repairing CuZn37 brass products using TIG welding with CuSn4Zn3 filler wire was developed. This approach ensures high-quality defect-free weld joints, dense welds with satisfactory mechanical properties, and a minimal zone of softening.