The failure behavior of buckling pin valve: Theoretical, numerical, and experimental study

At present, buckling pin in the bypass of piping as pressure relief valve has been gradually utilized in the low-concentration coal-bed methane (CBM), which bends to release pressure when the main valve fails leading to pipeline blockage. However, current researches mainly focused on the buckling behavior of hydraulic cylinder rod or rod string, and less consideration was given to the operational reliability of buckling pin valves. This paper deduced the calculation formula of the critical failure load based on Euler formula in the buckling pin under buckling load. Besides, three finite element models (FEM) based on Johnson−Cook constitutive model were compared to predict failure strength of buckling pin which were verified by experiment. In addition, the defect sensitivity analysis of the buckling pin under different initial geometric defects rate was carried out. The results showed that a) the experimental value of the critical failure load in the buckling pin was 206.04 N and the bending position was in the middle of the buckling pin; b) the analysis result adopting explicit dynamic method was in best agreement with the experimental results within deviation of 0.24%; and c) the initial geometric defect of buckling pin should be controlled within 1%. This study provides an important reference to predict the critical failure load of the buckling pin valve and achieve safe transportation of low-concentration CBM.

Photo de-mixing in mixed halide perovskites: the roles of ions and electrons

Mixed halide perovskites have attracted great interest for applications in solar cells, light emitting diodes and other optoelectronic devices due to their tunability of optical properties. However, these mixtures tend to undergo de-mixing into separate phases when exposed to light, which compromises their operational reliability in devices (photo de-mixing). Several models have been proposed to elucidate the origin of the photo de-mixing process, including the contribution of strain, electronic carrier stabilization due to composition dependent electronic energies, and light induced ionic defect formation. In this perspective we discuss these hypotheses and focus on the importance of investigating defect chemical and ion transport aspects in these systems. We discuss possible optoionic effects that can contribute to the driving force of de-mixing and should therefore be considered in the overall energy balance of the process. These effects include the selective self-trapping of photo-generated holes as well as scenarios involving multiple defects. This perspective provides new insights into the origin of photo de-mixing from a defect chemistry point of view, raising open questions and opportunities related to the phase behavior of mixed halide perovskites.

Ensuring Operational Reliability of Overpass on "Almaty-Kapshagai" Highway Section in Kazakhstan

The article presents results of the overpass condition survey, technical survey, static tests and assessment of the structure operational reliability, a doubledecker overpass on Almaty-Kapshagai highway section in Kazakhstan. Technical survey determined the dimensions of the overpass, the camber of reinforced concrete superstructures main beams and checked the values of the overpass roadway actual transverse and longitudinal slopes. The calculation and analytical assessment of the overpass load-bearing structures, for the strength of the bending moment, are performed. Static tests of the overpass split beam superstructure of a length of 33.0m were conducted. Trucks loaded with ballast were accepted as a test load.

State of open wagon body when loading on a rotary car dumper

The use of modern means of mechanization of loading and unloading operations in places of mass processing of bulky loads in railway and water connection allows to increase the efficiency and productivity of various types of transport, to ensure the safety of load and rolling stock. The most common method of unloading open wagons in ports, mining enterprises, thermal power plants, etc. is the use of special rotary car dumpers. However, it should be noted that unloading on the car dumpers leads to damage of the carriages structural elements. The article presents the results of strength calculations of the car dumper body under the influence of specified dynamic loads from the expiring cargo. They show that the safety margin of the load-bearing elements of the car body is not enough at critical corners of rotation of the car dumper rotor. The studies were carried out using modern computer modeling methods used in the development of new-generation freight car designs. The software package took into account the effects of dynamic loading as external factors that occur at different corners of the car dumper rotor. The implementation of the results obtained at the design stage of innovative structures of open wagon car bodies will allow predicting the operational parameters of load-bearing structures. The presented studies are aimed at improving the safety and operational reliability of the cargo car fleet.

Features of monitoring storage of methane-hydrogen mixtures

The storage of methane-hydrogen mixtures (MHM) in existing underground gas storage facilities (UGS) is a prerequisite for the development of a "carbonneutral" strategy of the Russian Federation. The use of technologies for storage and delivery of MHM in industrial volumes should be ensured by experimental research, the creation of a regulatory framework and the introduction of modern methods for maintaining the operational reliability of the existing Unified Gas Transportation System (UGSS). The need for scientific and project work is determined by the peculiarities of the storage of MHM and the assessment of the likelihood of negative technogenic and mechanical consequences during the operation of the equipment. The materials provide the main risk models of the processes that arise in the case of hybrid storage of MHM. The use of cluster technology for storage and transportation of MHM is proposed, and the need to ensure constant monitoring of the component composition of gas as part of the implementation of an integrated automated flow technology is shown. Keywords: methane-hydrogen mixtures; hydrogen energy; underground gas storage; hardware control; risks.

Statistical Estimation of Resistance to Cyclic Deformation of Structural Steels and Aluminum Alloy

Resistance to cyclic loading is a key property of the material that determines the operational reliability of the structures. When selecting a material for structures operating under low-cycle loading conditions, it is essential to know the cyclic deformation characteristics of the material. Low-cycle strain diagrams are very sensitive to variations in chemical composition, thermal processing technologies, surface hardening, loading conditions, and other factors of the material. The application of probability methods enables the increase in the life characteristics of the structures and the confirmation of the cycle load values at the design phase. Most research papers dealing with statistical descriptions of low-cycle strain properties do not look into the distribution of low-cycle diagram characteristics. The purpose of our paper is to provide a probability assessment of the low-cycle properties of materials extensively used in the automotive and aviation industries, taking into account the statistical assessment of the cyclic elastoplastic strain diagrams or of the parameters of the diagrams. Materials with contrasting cyclic properties were investigated in the paper. The findings of the research allow for a review of durability and life of the structural elements of service facilities subjected to elastoplastic loading by assessing the distribution of low-cycle strain parameters, as well as the allowed distribution limits.

ASSESSMENT OF THE IMPACT OF TECHNOLOGICAL HEREDITY ON INDICATORS OF RELIABILITY, DURABILITY AND ENVIRONMENTAL SAFETY OF ELEMENTS OF GAS TRANSMISSION SYSTEMS

Modern gas transmission systems are power facilities based on a main pipeline, which is a continuous pipe, along which devices are placed that provide gas pumping at predetermined parameters. Unlike other linear structures, such as roads, railways, the main pipeline throughout the entire period of operation is in a complex stress state under the influence of the internal pressure of the pumped product and functions as a pressure vessel. The operational reliability, durability and environmental safety of gas transmission systems are ensured by various control devices and pipe fittings. The article discusses issues related to predicting the operation of pipe fittings during the operation of the gas transmission system, while ensuring the required reliability, durability and environmental safety. An analysis of the phenomena of technical heredity is given, with the help of which it is possible to determine the causes of deviations in the output parameters of pipe fittings in the process of their manufacture or repair. It has been proved that the main feature of technological heredity is the transfer of a certain technological property from the previous technological operation to subsequent ones, characterized by the transfer coefficient of technological heredity. An indispensable condition for the monotonicity of changes in the transmission coefficient of technological heredity in order to ensure the required quality of manufacture or repair of pipe fittings is revealed. The economic principle of predicting the quality of manufacturing or repair of products is proposed for use, a relationship is found between the initial and output technological properties of pipe fittings, a route is chosen to achieve the required quality of its manufacture or repair, including procurement and finishing technological operations.

Operational reliability of suspended facade structures with variable thickness of the cladding layer

The article presents the results of laboratory tests of experimental samples for mechanical safety, aimed at obtaining data pertaining to the performance of protective and decorative brick facade structures on metal substructures. The designs of the samples are atypical, with a different arrangement of bricks in the face layer and with ledges evenly distributed over the surface of the sample. Based on the test results, structure behavior under load, the absolute values of the displacement of the cladding layer, and the values of the bond strength between bricks and mortar were established. During the tests, the displacement of the protective and decorative structure in the direction of the applied load and the values of the forces, corresponding to the strength limit, were recorded.The article addresses the issue of the lack of rules for the design and testing of suspended facade systems made of bricks on metal substructures in the regulatory and technical documentation of the Russian Federation.

Transport systems load-bearing structures state diagnistics and monitoring

Aim: To provide the study and control of the stress-strain state of load-bearing structures during the operation of magnetolevitation transport systems. Methods: Experimental and theoretical studies of dynamic parameters. Results: To assess the stress-strain state of the main load-bearing structures of magnetolevitation transport systems using string superstructure it is proposed to measure the natural vibration frequencies. Conclusion: The organization of diagnostics or monitoring of changes in the natural vibration frequencies of load-bearing structures ensures the operational reliability of load-bearing structures for Maglev.

An Overview of Digital Twin Concept for Key Components of Renewable Energy Systems

Renewable energy (RE) is green and low-carbon energy, which can not only protect the environment, promote the technological diversification of the energy supply system, accelerate the adjustment of energy structure, but also has important significance for the sustainable development of economy. With the increasing complexity of the problems of renewable energy system asset management and ensuring the operational reliability of electric power equipment, it's necessary to establish remote, online, reliable monitoring and inspection techniques for the state evaluation of electrical equipment during the full life cycle. In order to meet these demands, the digital twin is a very suitable technology. In recent years, there are numerous scientific papers demonstrating DT's capabilities in virtual simulation, condition monitoring (CM), power optimization and fault diagnosis for RE generation systems, transmission and transformation equipment and storage systems. The majority of the research focusing on product design, maintenance of operation, condition monitoring and fault decision-making has provided many valuable contributions to academia and industrial fields. Nevertheless, all this valuable information is scattered over many literatures and it is lack of systematic generalization. In this article, different applications of DT technology in RE system are analyzed, advanced methods and theories are summarized comprehensively, and the development trend of DT technology in renewable energy system in the future is introduced.