Failure-free Performance Research Articles

Probabilistic approach of state transition elements of truss structures at corrosion

The purpose of the presented study is to determine and mathematically model the reliability of a steel truss with different variants of local failures of rod elements due to corrosion processes. In order to achieve a quantitative reliability assessment, the truss structure is considered as a combination of subsystems containing relatively small groups of rod components. Numerical calculations of truss structures taking into account the influence of corrosion have been carried out. It is shown that the components of the truss system can change their state by different schemes. The transition from one state to another depends on the level of stress state, which is caused by corrosion effects. It is easier to visualize this in a binary system. The probability of failure-free performance of rod components over the operating time can be written in vector form. By the matrix analysis method, failure states and functional states can be determined. As an example, a 5-bar structural system of a metal staircase type truss is considered.

Effect of cyclic loading on the microstructure of thin zirconia tapes

The effect of cyclic loading on the microstructure and the phase composition of thin zirconia tapes was studied. Zirconium oxide stabilized with 3 mol% of yttrium was used for preparing the tapes by the gel-tape casting method. The static and cyclic strengths of the samples with a thickness of approximately 0.2 mm were tested. The average static strength of 1233 MPa was determined in a three-point bend configuration. The maximal flexural stress during cyclic loading had to be kept below 900 MPa to ensure the failure-free performance of the tapes - (107 cycles). No evidence of an excessive transformation of the tetragonal microstructure induced by cyclic loading was found. The transformation toughening mechanism of the tetragonal microstructure was not significantly affected by cyclic loading. Based on the results, thin flexible 3Y-TZP parts possess a low risk of mechanically induced excessive transformational microstructural changes during the service life of the part.

A probabilistic approach to information management of order fulfilment reliability with the help of perfect-order analytics

Supplier reliability and order fulfilment performance are usually assessed using a perfect-order calculation. Information management of perfect-order estimation is frequently reduced to expert estimates and to the multiplication of probabilities of failure-free performance of some logistics operations. Moreover, perfect-order estimation is calculated without consideration of supply chain structure, possible combinations of failures, and operational policies (e.g., safety stock levels and alternative transportation routes). As a result, the existing methods frequently provide different estimates for the same statistics and cannot be consistently used in the allocation of companies’ resources to improve the order fulfilment process. This paper considers different variants of probabilistic assessment of a perfect order and proposes an approach to assess the impact of changes in parameter probabilities and number of parameters on the value of a perfect order. The proposed models are based on an analytical approach using discrete distributions of random variables. We illustrate the applicability of our approach to several numerical examples to confirm the adequacy of the proposed method. Our approach can be immediately applied in practice to assess supply and order fulfilment process reliability and to evaluate the effectiveness of various operational policies (safety stock levels or modes of transportation) to achieve some planned values of a perfect order in the supply chain.

Optimal preventive switching of components in degrading systems

In practice, at many instances, it is important to maintain the failure-free performance of components in a standby system, as each sudden failure of an operating component can result in a failure of a system, e.g., due to imperfect or/and ‘non-instantaneous’ switching on failure and related adverse effects. Therefore, the scheduled preventive switching/replacement to the standby component that can be executed without these consequences is one of the effective methods for increasing reliability characteristics of such systems, especially in the safety-critical applications. In this paper, the corresponding optimal strategy for switching is described and justified for the cold standby system of two aging components with degradation modeled by the counting Poisson and gamma processes. An inspection is carried out at some optimally predetermined time and based on the observed degradation switching is performed after the optimally obtained delay. Detailed numerical examples illustrate our findings.

Raman Spectroscopy Studies of TRISO-Particle Fuel

Development of High Temperature Gas-cooled Reactors opens new horizons for nuclear power in Poland. Good understanding of the failure-free performance of Tri-structural ISOtropic (TRISO)-particle fuel is a key for the safe and efficient operation of those reactors. It is also essential to avoid potential errors in TRISO fuel production for the HTR program in Poland. In a longer perspective to ensure the highest possible quality of the TRISO fuel fabrication and storage before loading into the reactor core, it is necessary to control the quality of the TRISO-particle fuel in order to understand the aging of fresh fuel. Nevertheless, such a solution requires to determine whether the passage of time affects the occurrence of changes in TRISO fuel layer’s structure and at the same time whether it contributes to increasing the probability of damage to the examined fuel material. For this purpose, it is planned to perform an experiment on different types of TRISO fuel, produced in different periods of time. The comparative analysis will be based mainly on the experimental method of Raman spectroscopy.

A novel adaptive control design method for stochastic nonlinear systems using neural network

This paper presents a novel method for designing an adaptive control system using radial basis function neural network. The method is capable of dealing with nonlinear stochastic systems in strict-feedback form with any unknown dynamics. The proposed neural network allows the method not only to approximate any unknown dynamic of stochastic nonlinear systems, but also to compensate actuator nonlinearity. By employing dynamic surface control method, a common problem that intrinsically exists in the back-stepping design, called “explosion of complexity”, is resolved. The proposed method is applied to the control systems comprising various types of the actuator nonlinearities such as Prandtl–Ishlinskii (PI) hysteresis, and dead-zone nonlinearity. The performance of the proposed method is compared to two different baseline methods: a direct form of backstepping method, and an adaptation of the proposed method, named APIC-DSC, in which the neural network is not contributed in compensating the actuator nonlinearity. It is observed that the proposed method improves the failure-free tracking performance in terms of the Integrated Mean Square Error (IMSE) by 25%/11% as compared to the backstepping/APIC-DSC method. This depression in IMSE is further improved by 76%/38% and 32%/49%, when it comes with the actuator nonlinearity of PI hysteresis and dead-zone, respectively. The proposed method also demands shorter adaptation period compared with the baseline methods.

Accelerated testing of the friction pairs of mechanical seals made of composite material of the TiC – SiC system

Novel wear-resistant materials used in friction pairs are being developed to increase their reliability and failure-free performance in operation, reduce the environmental load and energy consumption in manufacturing processes. One of the promising functional materials for manufacturing durable and wear-resistant parts and products that undergo intensive wear in operation is a powder material of the TiC – SiC system obtained by spark plasma sintering (SPS). SPS is an energy-efficient alternative to hot pressing and environmentally-friendly procedure compared to that used in manufacturing serial friction pairs from the lead-graphite composition NAMI GS-TAF-40 for tractor industry. Prototype friction pairs made of the powder material of the TiC – SiC system have been manufactured by SPS technology using sketches of a serial friction pair of the mechanical seal of a centrifugal pump 16-08-140SP of the cooling system of D-180 diesel engine developed for a T10 tractor. The goal of the study is accelerated bench testing of the obtained experimental friction pairs. The tests were carried out on the equipment of a modular block for testing mechanical seals designed for the USI «Climate». The method of accelerated testing provided simulation of the operational tests of experimental friction pairs of mechanical seals of centrifugal pumps of the cooling system of an internal combustion engine with a 2.0 – 2.5-fold acceleration. The criterion for the applicability and evaluation of the results of accelerated tests of experimental friction pairs was the similarity of temperature conditions of the water pump seal and the compression forces of the rings in the friction pair under real diesel operation and the accelerated test modes for the increased rotational speed of the centrifugal water pump shaft. A path traveled by the point of the average radius of the «contact line of touch» of the working surfaces of the rings with allowance for test acceleration coefficient (2.0 – 2.5) was taken as a basis for assessing the reliability and durability of test objects. During accelerated testing, all the test parameters were taken into account in addition to visual inspection of the test equipment and the mechanical seal. The wear resistance of the experimental friction pairs was determined by change in the mass through intermediate measurements of the ring wear after 100 and 200 hours of testing. Accelerated bench tests revealed that a friction pair with parts made of a TiC – SiC-based composite material will provide at least 1.5- fold increase in the service life of the mechanical seal of the centrifugal pump of a D180 diesel cooling system.

Explicit and implicit inclusion of time in the definitions of risk and reliability

In safety, understanding of risk and reliability is generally not possible without reference to time. For example, regarding the risk of some activity or situation, focus is on what might happen in future time in relation to the potential for negative outcomes or consequences. Currently, several definitions of risk are available, indicating a lack of consensus on how to define this, also within international standards. A common characteristic, is that neither of the definitions are explicitly capturing time. In contrast, the concept of reliability is explicit on this, focussing on failure-free performance for a given time interval, indicating a discrepancy and inconsistency between the concepts. There are different temporal aspects and key argumentation for and against inclusion of time in the definition of risk. We discuss the relevance to the understanding and interpretation, and conclude, that it is insufficient to assume time strictly implicitly as part of the possible consequences. As for the reliability concept, the element of time matters to the understanding of risk as a concept, and contributes to a more specific description of risk. A more appropriate definition of this concept that allows for this element to be explicitly captured is suggested in this article.

ИССЛЕДОВАНИЕ ЭКСПЛУАТАЦИОННОЙ НАДЕЖНОСТИ СИСТЕМ ПИТАНИЯ ТОПЛИВОМ ДИЗЕЛЬНЫХ ДВИГАТЕЛЕЙ

The results of the investigation of operational reliability of the fuel supply system of diesel engines F1A FIAT DUCATO cars, the main reasons for the system's loss of operability, the numeri-cal characteristics of its failure-free performance are given. On the basis of processing the array of experimental data on faults and failures in the system, the regularities of change of failure intensi-ty and probabilities of failure-free operation of its main parts depending on vehicle mileage are determined. Methods and algorithm of troubleshooting and timely elimination of damages occur-ring in the fuel supply system are proposed and tested at the FIAT PROFESSIONAL dealership in Vladimir. The introduction of the results of the performed investigations into the production pro-cesses of car service enterprises allows to significantly reduce the costs of maintaining the opera-ble state of the diesel engine fuel supply system in operation.

Evaluation of the main indicators of the reliability of the power transmission of a combine harvester John Deere 9660

The failure-free performance of the components determines the technical and economic efficiency of the use of the combine harvester. A low level of reliability leads to an increase in the cost of harvesting, the need for unscheduled repairs due to failures of parts, assemblies and assembly units. Studies have shown that a significant proportion of failures occur in power transmission units. In this regard, the aim of the work is to assess the reliability of the power transmission of the John Deere 9660 combine harvester. The average time between failures of the power transmission units was 80 hours, which does not meet the regulatory requirements (according to STO AIST 8.22 - 2010 - at least 100 hours). Failures of all powertrain assemblies are caused by a combination of failures: wear and fatigue failure of the bore holes for the bearings of the unit housings, and gears, bearings from dynamic loads.

Factors Influencing Capacity Utilization of Mechanical Resources in Construction Industries

Construction industries in present world do face several challenges from project feasibility status to handing over of the project. With the unbounded scope and inevitable need for automation and machine tools, the success of any project heavily relies on the effective and uninterrupted performance of mechanical resources used in the projects. Companies spend huge amounts to own, operate and maintain these resources. The optimum utilization and failure-free performance of these resources are expected from the stake holder’s perspective. An experiment is carried out using the principles of Design of Experiments to decide as which are the most influential factors affecting the utilization of the mechanical resource with the help of Mini Tab software and the results are discussed.

Засоби автоматизованого формулювання умов працездатності складних технічних систем

Під надійністю техніки розуміють здатність системи або її складових виконувати свої функції за заданих умов та у визначений період часу. Надійність є комплексною характеристикою технічної системи і, відповідно до її призначення, може включати: безвідмовність, довговічність, ремонтопридатність й інші атрибути або їх комбінації. Надійнісний аналіз проводиться з використанням певної кількості засобів графічного моделювання для забезпечення наочності етапів процесу, таких як структурні схеми надійності, дерева відмов та ін. Структурні схеми надійності (англ. Reliability Block Diagram) є простим, але наочним методом демонстрації зв'язків між елементами системи за допомогою блоків і з'єднувальних ліній. Моделювання структури технічної системи і визначення характеристик її складових з використанням структурної схеми надійності є потужним та наочним засобом, але складність його зростає відповідно до кількості елементів та вузлів системи. Методи аналізу структурних схем мають експоненціальну складність, яка залежить від кількості елементів та способу їх розміщення. Для вирішення цієї проблеми розроблено засоби автоматизованого формулювання умов працездатності складних технічних систем, які складаються з: алгоритму обходу структурної схеми надійності, алгоритму виявлення послідовного з'єднання та алгоритму виявлення паралельного з'єднання, які виявляють сегменти, котрі з'єднані між собою послідовно та паралельно відповідно. Також подано програмне забезпечення візуалізації структурних схем надійності та автоматизованого формулювання умов працездатності технічних систем, яке дає змогу звільнити користувача від багаторазового виконання рутинних операцій та автоматизувати процес формування вхідних даних для подальшого надійнісного аналізу.

Development and Performance Validation of a Cylindrical Buoy for Deep-Ocean Tsunami Monitoring

This paper describes the development and performance validation of a cylindrical surface buoy (CSB) used for monitoring tsunamis in Indian seas. The buoy design with multiple compartments provides damage-tolerance curved top surface profile, the subsurface access ensures vandalism resistance, and the shape provides enough space for the power and control systems for an offshore endurance of two years. The scaled-down CSB is numerically modeled and experimentally validated for its stability in a wave basin. The validated numeric model is extended to a diameter of 2.4 m and the mooring loads are analyzed. The field scale prototype CSB is deployed in the open ocean, where the water depth is 2500 m. The performance of the CSB is validated from one year of failure-free performance and capability to remain within the watch circle under all environmental conditions, and it has detected the water level change events during the operational period.

Influence of Minimally Permissible Quantity of Source Materials on the Probability of Failure of a Pump−Tank System

A mathematical model is proposed and practical implementation of an assessment of the reliability of equipment with the use of Markov models is considered. An assessment of the increase of failure-free performance of the entire plant as a function of the minimum residual levels of source materials in the intermediate tanks with failure of the auxiliary equipment is obtained.

ОN THE INTEGRATED CRITERIA OF MACHINERY AND EQUIPMENT RELIABILITY

On the example of chain conveyors, the article shows the relationship between the change in the operation process of constructive, energy and other parameters of a machine and reliability parameters. The authors have presented the analysis of methodological approach that is based on wear and damage of machine parts with increase in the duration of their operation and the impact of these changes on the performance of a machine. On the example of heavy-duty transporters, the paper presents the method which shows that at a constant load of conveyor (Q и W-const ) with increase in the duration of its operation, the power required to drive it will also increase. According to this parameter, one can judge about the current status of power components of a conveyor, and it is also possible to calculate the reliability (longevity, failure-free performance, etc.). If you use a chain with links strengthened by innovative technologies (e.g., wear-resistant coatings and modification of surface layers by diffusion saturation, etc.) longetivity increases. The energy supplied to the machine is spent on useful work and overcoming friction forces and other resistance forces arising in the machine elements. As you increase the duration of operation, the condition of machine parts changes (due to wear, corrosion, fatigue and other destructive processes). These changes mainly cause more energy consumption for overcoming them. Thus, when having a constant load of conveyor (Q и W-const ) with increase in the duration of its operation the power required to drive it will increase too. For this parameter which is easily measured by appropriate instruments, it is possible to judge the current status of the power components of a conveyor, and calculate the reliability (longetivity, failure-free performance, etc.)., etc.). One of the important indicators of reliability of complex machinery is maintainability. Machines parts are restored in parallel in specialized shops or businesses, and the repair time does not overlap with the downtime of the whole machine to be repaired. Therefore, maintainability in such cases can be more properly evaluated using such an indicator as the complexity of maintenance and repair. The article shows the possibility of evaluating machine reliability according to the complexity of works, their maintenance and repair. The obtained dependences established for evaluation of reliability of machines on the basis of complex criteria can be used at the design stage, when calculations of the output parameters can be carried out instead of costly full-scale or bench testings.

Development of Combined ICE Startup System by Means of Hydraulic Starter

Currently there are several known engine startup systems for cars and tractors: a manual one; an electrical starting system; using a special starting engine; featuring the start by means of a switchover to gasoline with electric ignition; pneumatic start. The performed analysis of the startup systems shows that they have significant drawbacks: a relatively low reliability, dependency on the climatic conditions, high energy consumption and complexity of maintenance, low developed torque. These drawbacks can be eliminated by developing a brand new combined engine startup system by means of the hydraulic starter, which is distinguished by its high reliability, failure-free performance, and availability of manual start. This startup system is combined with the turbocompressor lubrication system and comprises an autonomous lubrication-brake device. During the application of the autonomous lubrication-brake device at the laboratory bench we have obtained empiric dependencies of the four variants of the turbocompressor rotor rundown: normal rundown mode; rundown with the hydraulic accumulator; rundown with simultaneous application of the hydraulic accumulator and the brake device; rundown with the brake device. During the application of the autonomous lubrication-brake device the rotor rundown duration is decreased by 30-35% as compared to the free rundown, which allows excluding the risk of dry friction of the turbocompressor bearings. The installation of the combined hydraulic startup system ensures a safe start at any temperature, as well as reliable lubrication and shutdown of the turbocompressor rotor.

Some Remarks on the Asymptotic Behavior of the Empirical Availability Function

We consider the asymptotic behavior of the empirical availability function, which is an important reliability characteristic of technical, communication, information, or transport systems. Our main focus is the case of violation of the classical assumptions of homogeneity of failure flow or the existence of the expectation of failure-free performance or repair duration. Both the classical situation dealing with samples with nonrandom size and the situation where the number of available observations is unknown beforehand, that is, the sample size is random, are considered. In a special situation where the sample size has a negative binomial distribution, an analogue of the law of large numbers is proved for random sums of not necessarily identically distributed random variables describing conditions for the convergence of the distributions of negative binomial random sums to generalized gamma distributions. Thus, a simple limit scheme is proposed, within which generalized gamma distributions turn out to be...

Studuing Lubrication System of Turbocompressor Rotor with Integrated Electronic Control

Forcing of engines together with positive properties – uprating within 5–50 % has a considerable drawback, i.e. the decrease of its service reliability. The performed analysis of literature points at a considerable increase in the number of turbocompressor failures. The main causes are as follows: nonobservance of the startup and shutdown modes by the operators; breach of the maintenance standards; high randomness of the load modes of 10-150%. The operability and increase of the failure-free performance of the turbocompressor and its elements can be achieved by the application of the suggested lubrication system of the turbocompressor internal combustion engines. The use of the lubrication system of the turbocompressor internal combustion engines with an autonomous lubrication-brake device and an autonomous control system of the turbocompressor rotor braking prevents coking of lubricant oil residues in channels of the turbocompressor lubrication system in case of a sudden (emergency loaded) shutdown of the internal combustion engine in the mode of the turbocompressor rotor rundown, and implies a regulated supply (by the volume, time and temperature) of oil in the turbocompressor bearing, as well as a regulated (by temperature) supply of the air compressed by the turbocompressor pump wheel to the inlet of the turbocompressor turbine wheel, which reduces the temperature of the turbine parts with the temperature of 600–700oС, wherein the service reliability of the bearings, rotor, body and the turbocompressor in general is increased. The application of engineering samples of the autonomous lubrication-brake device on car-and tractor and combine machine diesel engines of vehicles allows decreasing the number of turbocompressor failures by 10–15 %. The estimated economic effect comprises 50–80K rubles per season of operation of mobile energy-converting machinery with the increased unit capacity.

Research in behavior of the centre of failure free performance distribution density for redundant complex technical systems

Aim. For complex highly-integrated technical systems that contain elements that vary in their physical nature and operating principles (combination of mechanical, electrical and programmable electronic components), complex dependability analysis appears to be challenging due to both qualitative and quantitative reasons (large number of elements and performed functions, poorly defined boundaries of interfunctional interaction, presence of hidden redundancy, static and dynamic reconfiguration, etc.). The high degree of integration of various subsystems erodes the boundaries of responsibility in the cause-and-effect link of failures. Thus, the definition of the strength and boundaries of interfunctional and cross-system interaction is of great value in the context of complex system analysis from the standpoint of locating bottlenecks, as well as reliable evaluation of the complex dependability level. Methods. In order to solve the tasks at hand, the authors propose a method that is based on the research of the behavior of the centroid of an area bounded above by the failure density function graph, below by the coordinate axis, from the right and left by the boundaries of the considered operation interval. Graphical analysis with construction of centroids is performed for each subsystem or structural unit of a complex technical system. After that, based on the partial centroids of the respective subsystems/units, the average centroid for the whole complex system is constructed. The authors suggest using the average centroid as a conditional universal measure of the average dependability level of highly-integrated technical systems that can be used in the development of specific design solutions. In this case, in particular, it is suggested to use the presented method for identification of the subsystem that, when redundant, ensures the highest all-around growth of dependability of the complex technical system as a whole. This condition is fulfilled by the subsystem/unit of which the partial centroid is situated at the longest distance from the average centroid. The assumptions presented in this article and the results obtained are tested by means of a short verification consisting in the calculation of the probability of no-failure of the system and subsystems, construction and analysis of respective graphs. Results. The method’s implementation is presented using the example of a conventional mechatronic system. For the sake of briefness and focus the information is given in a simplified and abstract form. The application of the proposed method for analyzing complex technical systems dependability through the research of density function centroid introduced in this article was the target criterion of the method’s development, i.e. identification of bottlenecks and areas with the highest potential for increasing the overall dependability. Further publications will be dedicated to proving the applicability of such entity as a centroid as a dependability evaluation criterion, as well as other applications of the presented method in complex technical systems dependability analysis.

Possibilities of the design estimates of the reliability of a high-pressure metal-composite tank

The problem of the estimation of the reliability of a metal-composite overwrapped pressure vessel for the electrojet engine unit of a satellite vehicle is considered. The functions of probabilities of failure-free performance according to impermeability and strength criteria are used as reliability characteristics. The peculiarities of the estimation of the mentioned probabilities of failure-free performance are studied for different stages of the service life of the tank.