Justification of the Application of Resource-Saving Technology for the Restoration of Metal-Intensive Rear Semi-Axles of Trucks Using Hot Plastic Deformation

The article is devoted to the substantiation of technological foundations for the restoration of extremely worn-out, metal-consuming, and resource-consuming parts, in a method consisting of applying a compensating metal wear with subsequent plastic deformation. Currently, there are no technologies for their restoration in a repair facility that guarantee the resilience of the factory product. The proposed technological process of repair consists of butt welding onto the end of the spline semi-axle shank, compensating for the wear of the metal, the volume of which takes into account the losses resulting from the wear of the slots, as well as allowances for their machining. In the example of forging the axle shaft of a truck’s driving axle, the regularities of the plastic flow of metal during part deformation in the stamp are revealed. In the process of hot volumetric upsetting of long cylindrical parts with a variable diameter, it is important to know the possible directions of metal movements, as well as the energy-power characteristics of the process at various stages of forging. The evaluation criteria of the level of perfection of the technology were indicators of resource conservation and efficiency of the recovery route. The technological direction of the conducted research was analyzed, step by step, from the standpoint of saving repair materials and energy resources. The results of theoretical studies are crucial in the design of die tooling, for the manufacture of blanks, when restoring the rear axle shafts of trucks with pressure. Production tests carried out on the models, obtained as a result of mathematical processing of experimental data, confirmed the reliability of the experimental information. The introduction of the proposed set of repair equipment for the restoration of semi-axles will allow the formation of additional production in the region for the recycling of worn-out metal-intensive steel parts of agricultural machinery.

VACUUM SYSTEM OF KLYSTRON REPAIR FACILITY FOR ELECTRON ACCELERATORS

KIU-12AM “AVRORA” klystron has been the main source of rf power for the accelerators for decades. Large accumulations of malfunctioning klystrons made it possible to recycle them using the donor parts, which are well preserved and still functional. Klystron repair process comprises of few stages and part of these stages requires maintaining the high vacuum inside the klystron and adjacent systems.

Major restoration of massive bridge supports

The object of research in this article is the methods of restoring massive bridge supports, depending on the nature and volume of destruction. The work is based on the analysis of publications of domestic and foreign scientists, by the method of theoretical study, analysis and generalization of the material. From an organizational point of view, minor work on the repair of supports can be carried out by the order of the roads themselves, but as for large-scale work, they are sharply different from work on temporary restoration. The repair of damaged supports from a broken part of the masonry is not much different from the repair and reinforcement of supports performed on existing bridges. The greatest difficulties will be the repair of supports in the underwater part. To work on each individual repair facility, organizations with high mobility, skilled labor and a sufficient supply of materials are needed.

OVERVIEW OF MOBILE MACHINE DESIGNS FOR LARGE-SIZED PRODUCTS

The repair of large-sized products without a specialized repair facility is usually not available due to the impossibility of ensuring high accuracy when performing mechanical processing. Nevertheless, dismantling and moving large-sized items to the repair facility significantly increase the downtime of the equipment being repaired, or it is technically impossible to perform. Specialized machines that are used to repair large-sized items in such facilities are unique and expensive. They are heavily loaded and this can lead to various risks associated with the timing of the repair. Therefore, it is necessary to reduce the time required for dismantling, moving and processing large-sized items. In this regard, the rejection of these operations in favor of the use of mobile machines will significantly reduce the time and cost of repairs of large equipment. The article discusses domestic and foreign achievements in the field of mobile machines and systems that are used for maintenance and machining of large-sized products on site without dismantling. A number of designs of specialized mobile machines for use in various industries are described.

Performance Analysis of Photovoltaic Systems Using (RAMD) Analysis

The primary aim of this present study is to examine how reliability, availability, maintainability, and dependability (RAMD) are used to describe the criticality of each sub-assembly in grid- connected photovoltaic systems. A transition diagram of all subsystems is produced for this analysis, and Chapman-Kolmogorov differential equations for each variable of each subsystem are constructed using the Markov birth-death process. Both random failure and repair time variables have an exponential distribution and are statistically independent. A sufficient repair facility is still available with the device. The numerical results for reliability, maintainability, dependability, and steady-state availability for various photovoltaic device components have been obtained. Other metrics, such as mean time to failure (MTTF), mean time to repair (MTTR), and dependability ratio, which aid in device performance prediction, have also been measured. According to numerical analysis. it is hypothesized that subsystem S4, i.e. the inverter, is the most critical and highly sensitive portion that requires special attention in order to improve the efficiency of the PV device plant. The findings of this research are very useful for photovoltaic system designers and maintenance engineers.

Stochastic Model on Three-Similar Units Three Phased Mission System with FCFS Repairs Pattern

The paper allocates a stochastic model on threesimilar units three-phased mission system. The developed system consists of units working in parallel, series and parallel configurations respectively. Initially, the three similar units are operational. Each component has only three states: good, degraded and failed. In this case, the single repair facility that repairs the units in first come first serve (FCFS)pattern has been thought of. Using Semi-Markov Process and regenerative point techniques, various measures of the system performance at each phase are obtained. The system has been analyzed graphically taking a particular case. Various conclusions are made regarding the reliability and cost consideration of the system at each phase as well as for the whole system(as combined Phase I, Phase II, Phase III).

Optimizing a Multi-State Cold-Standby System with Multiple Vacations in the Repair and Loss of Units

A complex multi-state redundant system with preventive maintenance subject to multiple events is considered. The online unit can undergo several types of failure: both internal and those provoked by external shocks. Multiple degradation levels are assumed as both internal and external. Degradation levels are observed by random inspections and, if they are major, the unit goes to a repair facility where preventive maintenance is carried out. This repair facility is composed of a single repairperson governed by a multiple vacation policy. This policy is set up according to the operational number of units. Two types of task can be performed by the repairperson, corrective repair and preventive maintenance. The times embedded in the system are phase type distributed and the model is built by using Markovian Arrival Processes with marked arrivals. Multiple performance measures besides the transient and stationary distribution are worked out through matrix-analytic methods. This methodology enables us to express the main results and the global development in a matrix-algorithmic form. To optimize the model, costs and rewards are included. A numerical example shows the versatility of the model.