Failure Of Elements Research Articles

Preferred Seismic Performance Attainment in Important Buildings

In the aftermath of earthquakes, hospital buildings are expected to remain occupiable to treat the injured. For the purpose, firstly, an appropriate structural system that ensures no or limited structural damage should be provided in such buildings; wall-frames are the recommended structural systems in hospital buildings. Secondly, it is also essential to adequately design wall-frames to help meet the preferred Occupiability seismic performance. The work presented in this paper examines the contributing factors for failure of structural elements in hospital buildings and explores structural configuration and design strategies for mitigating these failures. Nonlinear analyses studies of a typical hospital building in high seismic region in India are carried out to help provide quantitative guidelines for: (a) Structural Plan Density (SPD) of structural walls, and (b) design parameters, for achieving the preferred performance. Displacement-based limit state of structural damage adopted from traditional displacement demand estimation rules is proposed. Lateral stiffness, strength, and ductility are evaluated of study buildings, and efficacy of results obtained from nonlinear static analyses confirmed by performing nonlinear time history analyses in commercial software PERFORM 3D. Results demonstrate inadequacy of moment frame structural system in hospital buildings under strong earthquake shaking, identifies optimum overall SPD of structural walls and relative column-to-beam strength ratio of frame members, required to achieve Occupiability. A minimum 3% SPD of structural walls in Wall – Special Moment Resisting Frame (WSMRF), 4% SPD in Wall – Ordinary moment resisting frame (WOMRF) hospital buildings, and a minimum column-to-beam strength ratio (CBSR) of 2 is required in hospital buildings to attain Occupiability performance.

Evaluation of operational reliability of diesel fuel system elements

In the article, as a result of a review and analysis of studies on the reliability of elements of the power system of diesel engines, it was determined that the cause of most failures of elements of the power system is the presence of impurities and water in the fuel, and the use of a defective fuel filter. The purpose of the study is to assess the degree of reliability of elements of the power supply system of diesel engines under normal operating conditions. For this purpose, an observation program has been drawn up for a group of intensively working tractors. Taking into account apriori information, the following elements (nodes) were selected as observed elements. P1—fuel tank and fuel lines, P2—settler filter, Pz— high pressure fuel pump; P4 – fuel nozzle. The observation results were subjected to statistical processing and the probabilities of failure-free operation of each element were constructed. The correlation dependence of failure-free operation between the observed elements of the power system was assessed. To assess the actual reliability, the main statistical characteristics of the time between failures of the elements of the power system of the diesel engines of the tractors participating in the experiment were calculated. Graphs of the distribution of time between failures of power system elements were constructed, conclusions were drawn regarding the reliability and service life of the elements.

STABILITY ROBUSTNESS OF CONTROL SYSTEMS OF MULTIROTOR UNMANNED AERIAL VEHICLES

Multirotor unmanned aerial vehicles (UAVs) are broadly used in various military and civilian areas and tasks. In real flights of the multirotor UAVs, certain unexpected situations may occur, which can lead to improper functionality and even failures of elements or devices of the UAV’s control system. In some cases, this can even lead to the complete collapse of the UAV. Therefore, the safety of UAV flights is nowadays of prime importance. A method of analysis of the stability robustness of the UAV’s control systems with respect to the parameters multiplicative uncertainties (or perturbations), including possible efficiency degradation of DC motors, is proposed in the paper. Stability robustness is determined by a simple graphical procedure on the complex plane of the Nyquist or Nichols hodographs of the control system’s separate channels. That procedure is quite similar to the well-known classical feedback control procedure of determining the peak gain of the single-input, single-output closed-loop control system by the Nyquist hodograph of the open-loop system. A numerical example illustrating the proposed method is given.

Метод оптимизации алгоритма поиска неисправностей

The article provides a brief overview of ways to optimize binary algorithms for identifying a failed element. For a continuous object specified by a functional circuit, a mathematical model has been synthesized in the form of a table of fault functions (TFN). Using the TFN, you can calculate the minimum diagnostic test and build a troubleshooting dictionary. On the basis of the fault dictionary, the sequence of checks has been determined, i.e. an optimized and effective algorithm for binary identification of a failed functional element for the object of diagnosis in the form of a graph has been built.

Corrosion and brittle fracture of high strength steel in prestressed concrete structures: a critical review of the problem

Corrosion of high-strength steel (wire, strand, bars, etc.) for prestressed concrete structures always raises a great concern in builders as well as in structure owners. Corrosion can occur in service due to improper protection, construction defects, improper design, and unsuitable materials or improper steel element storage before construction. Corrosion can lead, because of a significant cross-section reduction and the high load, to the failure of the prestressing steel element. However, brittle fracture, the most significant and dreaded event, can also occur when a limited corrosion attack is observed. Brittle fracture is a consequence of different damage mechanisms, and it is strongly dependent on the type of steel element. Starting from a critical analysis of the theoretical aspects and from a literature review, a comprehensive framework for correctly approaching the problem is reported.

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.

Building practice of energy efficient earthquake-resistance buildings

The article discusses technologies for constructing energy-efficient, earthquake-resistant buildings that have increased rigidity and strength in their main components. These technologies utilize structures with enhanced damping and active seismic insulation systems. Practical implementations, design features, and technological aspects are examined. An analysis is conducted on the characteristics of current technologies, the conditions for production and installation, repairability, and their impact on the building's energy efficiency during operation. Technologies are systematized and categorized based on their principles of seismic protection during the analysis process. The analysis was conducted based on the following main criteria: steel consumption, suitability of repairable technologies used, possibility of implementing seismic protection during building reconstruction, ability to withstand seismic effects, feasibility of implementation, and energy efficiency. It has been determined that traditional technical solutions to increase rigidity and strength, such as introducing structures with increased damping used for buildings with precast, monolithic, and precast-monolithic frames, require a significant amount of additional resources. These solutions are characterized by accumulation of failures in individual hidden elements due to seismic loads, low maintainability, and often decrease the energy efficiency of the building. The use of seismic energy-absorbing mechanisms with high efficiency can significantly reduce resource costs for construction and increase maintainability, thus improving the overall sustainability of the structure. Based on the findings of the analysis, the following recommendations are made for conducting further studies on active protection systems in terms of design, development of construction technology, and potential application in the renovation of existing buildings.

Methods for predicting failures of functional elements of rocket and space technology products using visual decomposition and machine learning

Methods for predicting failures of functional elements of rocket and space technology products using visual decomposition and machine learning

ON THE SUPPRESSION OF VIBRATIONS IN ELASTIC LINKS OF A THREEMASS ELECTRIC DRIVE SYSTEM

The main reason for failures of technological mechanisms is associated with the failure of elements of the electric drive system. One of the main reasons for the malfunction of electric drive elements is the presence of vibrations in the elastic links of the mechanical part of the electric drive. Such phenomena mainly occur during transient processes of starting and stopping an electric drive, as well as under the influence of a load that is variable in nature. From the above, it is obvious that suppression of vibrations in the elastic links of the mechanical part is of practical interest. The most promising studies aimed at studying and suppressing vibrations in the elastic links of a three-mass electric drive system are analyzed. A comparative analysis of these studies shows that they consider the operating features of individual specific electric drive systems, which cannot provide a complete understanding of a comprehensive solution to the problem of ensuring the suppression of vibrations, arising in the mechanical part for various reasons. That is why it is necessary to evaluate the possibilities of suppressing elastic vibrations of the electric drive system, taking into account all its links. The goal of this work is to propose an approach for suppressing vibrations in the elastic links of a three-mass electric drive system. The change in the elastic moment under various characteristics of the load created by the mechanism is considered, in particular, in cases of constant moment, exponential and step laws of change. The capabilities of proportional-integral (PI) and proportional-integral-derivative (PID) controllers for suppressing oscillations are analyzed. It is substantiated that although the system stabilizes with a PID controller in a short time, it does not provide the expected result and therefore it is recommended to use a controller with a fuzzy logic due to its simple control and rather high efficiency. The results obtained can be successfully used to improve the reliability of a three-mass electric drive system.

COMPLEX DESIGNING ALGORITHM FOR SPACECRAFT ENERGY-CONVERTING EQUIPMENT

Introduction. The complication of the spacecraft payload requires the use of non-standard circuits. The analysis of scientific and technical publications shows that there is no formalized methodology for spacecraft energy-converting equipment designing. Reviewed publications consider some design algorithms taking into account one (efficiency) or two criteria (efficiency, weight and size characteristics). At the same time, the issues of ensuring trouble-free operation of energy-converting equipment are not sufficiently considered which leads to rejection of most part of proposed circuitsolutions and reduces developer efficiency.
 
 The research purpose is to form a spacecraft energy–converting equipment designing algorithm, taking into account the reliability, efficiency and relative power coefficient requirements.
 
 Materials and methods. The main provisions of the electrical circuit theory and the theory of technical systems reliability were used. All calculations were carried out in Mathcad 15.0.
 
 Research results. The article step-by-step discusses the design process using the example of boost and buck voltage converters. It is shown that taking into account the reliability requirements leads to a decrease of weight and size indicators (due to the additional mass of redundant elements) and efficiency (due to power losses on redundant elements). Converters with an AC-current node based on a double active bridge (active front end bridge inverter) and add-voltage circuits are considered. It can be seen that the use of converters with AC-current node in spacecraft energy-converting equipment is complicated because of low reliability or high weight and size meters.
 
 Conclusions. A converter circuit must ensure operation in the event of a single failure of a random power element. At the same time, scheme with a minimum number of power elements have the greatest prospects for application. A converter energy characteristic must be evaluated after ensuring the reliability.

Biomechanical Effect of Bone Variables and Implant Position on Femoral Damage Mechanism in Total Hip Arthroplasty

The impact of bone variables, including density, geometry, angle of femoral torsion, and thickness of the femoral cortices, on the formation of bone micro-damage following THA was investigated. Using CT images of avascular necrosis patients, we developed 28 intact femoral bone models with ages ranging from 19 to 87 years to explore the relationship between age and bone density. Among these 28 femur models, 10 models were selected for implantation with the Zweymuller stem, divided into two groups based on the highest and lowest bone mineral density (BMD). After proper stem insertion into the femoral bone canal, finite element analyses with nonlinear damage analysis were performed on the THA models under three boundary conditions: stance, lateral bending, and torsion. Using the Pearson’s correlation coefficient, the study revealed a strong correlation between bone density and fracture load in the 10 THA models, which remained consistent across all three boundary conditions: stance (r = 0.74), lateral bending (r = 0.79), and torsion (r = 0.88). However, a moderate correlation was observed between bone density and the number of solid element failures, which also remained consistent across all boundary conditions: stance (r = -0.40), lateral bending (r = -0.51), and torsion (r = -0.48). It was found that femoral models with a bent shape of the femoral shaft and thin cortices experienced greater bone damage compared to models with normal geometry. Additionally, THA models with retroversion stem placement resulted in higher bone damage compared to models with normal anteversion placement.

A pre-failure narrow concrete cracks dataset for engineering structures damage classification and segmentation

Monitoring of structures’ condition plays a fundamental role in providing safety for users and extending the structures’ lifespan. The monitoring is conducted through on-site inspections by engineers thus this process is time-consuming, labor-intensive and prone to subjective engineering opinions. Detecting damage using machine learning algorithms on images can support engineers’ work, especially for early damages which are difficult to see with the human eye. This article is focused on the concrete crack detection problem in engineering structural elements. Despite the availability of several concrete crack detection datasets, no dataset allows semantic segmentation of cracks narrower than 0.3 mm (the crack width limit for typical engineering structures elements and environmental conditions according to EC 1992-1-1) and the ability for crack classification is limited. The provided open dataset represents only cracks below the crack width limit of 0.3mm, which do not yet indicate concrete elements failure. It is dedicated for early crack classification and segmentation, so that damage protection can be taken at an early stage to prevent structural element damages.

Solution of the integral equation for the average cost of restoration in the theory of reliability of technical systems

Failures of elements during the operation of technical and many other systems are, as a rule, random in nature. This leads to various models of the recovery process, studied in probability theory and mathematical reliability theory. During the restoration process, failed elements are restored or replaced with new ones, and there is often a change in the costs and quality of the restored elements (time-to-failure distribution functions). The work examines the cost function (average cost of restoration) in the process of restoration of order k1,k2,in which, according to a certain rule, the costs of each restoration and the distribution functions of operating time change. Considering, that the recovery function (average number of failures) is well studied in reliability theory, a solution to the integral equation for the cost function is obtained through the recovery function of the model under consideration. For the order restoration process k1,k2,a formula is obtained for calculating the cost function through the restoration function of a simple process formed by the convolution of all distribution functions of the periodic part. For practical application, explicit formulas are obtained for the cost function during the restoration process, in which the periodic part is distributed according to an exponential law oran Erlang law of order with the same exponent α. The resulting formulas can be used to study the properties of the cost function and solve optimization problems in strategies for carrying out the restoration process in terms of price, quality, risk, if, for example, the average number of failures is taken as quality, the average cost of restorations as price, the dispersion of the number of failures as the risk, or cost of restoration.

Algorithm for Calculating Reliability of Single Linear Section of Steel Underground Pipeline

One of the most widespread technical systems in the world is underground steel pipeline communications (heat pipelines, main and distribution oil and gas pipelines, etc.). Accordingly, reliability assessment of such technical systems and their components is of great theoretical and practical interest. At the modern level of development, reliability calculation has become a mandatory stage in the design and diagnostics (during operation) of any technical systems in ge-neral, and in particular pipeline systems. A reliable calculation, either explicitly or implicitly, is always based on the model of the object being calculated. It is the adequacy of the model to the real physical relations and processes inside the technical object that determines the accuracy and practical value of calculation methods. It is proposed to consider a single linear section of an underground steel pipeline as a complex technical system of unequal elements from the point of view of reliability – the main element (steel pipe) and auxiliary protective elements combined into subsystems (blocks). The algorithm for calculating the reliability of the object is based on the method of block diagrams, taking into account the influence of the aftereffect of the failure of an auxiliary element (elements) on the reliability parameters of the main element, which more adequately reflects the specific features of the design and operation of steel pipelines compared with the applied static models. The variants of structural design of a steel underground gas pipeline with a protective insulation coating and with complex corrosion protection (insulation and electrochemical protection) are considered, for which refined formulas are obtained for calculating the main reliability (failure-free) indicators.

Fatigue Analysis and Estimation of the Number of Exposure Cycles until the Failure of the Sensitive Element of a Micromechanical Capacitive Accelerometer

Fatigue Analysis and Estimation of the Number of Exposure Cycles until the Failure of the Sensitive Element of a Micromechanical Capacitive Accelerometer

The superstructure behavior assessment of the railway bridge with truss element damage

The analysis of railway bridge accidents shows that at the present stage, the number of accidents and mechanical superstructures damage is associated with vehicle impacts. Bridge design standards recommend to check bridge structures for survivability, operational control standards do not cover such issues. To superstructure behavior assessment of a single-track railway bridge with truss element damage, a numerical study of changes in the stress-strain state of bridge superstructure was carried out within the framework of the dissertation research «Assessment of the operational reliability of metal spans with damage and methods of their monitoring». The object of the research is a typical superstructure with an estimated length of 66 m in the condition of complete or partial failure of various truss elements due to mechanical damage. As a result of the research, the nature of the redistribution of the stress-strain state of the superstructure was revealed. It is determined that the spatial redistribution of the stress-strain state occurs along the path of increasing stresses in the lattice elements of the parallel truss and longitudinal links. According to the control of allowable stresses and deflections, the survivability of the superstructure is maintained while 70 % of the single truss element elimination is reached. The elements for which mechanical damage is most dangerous have been identified.

Mechanism of balloon burst during transcatheter aortic valve replacement pre-dilatation: Image observation and validation by finite element analysis

BackgroundBalloon burst during transcatheter aortic valve replacement (TAVR) is serious complication. This study pioneers a novel approach by combining image observation and computer simulation validation to unravel the mechanism of balloon burst in a patient with bicuspid aortic valve (BAV) stenosis. MethodA new computational model for balloon pre-dilatation was developed by incorporating the element failure criteria according to the Law of Laplace. The effects of calcification and aortic tissue material parameters, friction coefficients, balloon types and aortic anatomy classification were performed to validate and compare the expansion behavior and rupture mode of actual balloon. ResultsBalloon burst was dissected into three distinct stages based on observable morphological changes. The mechanism leading to the complete transverse burst of the non-compliant balloon initiated at the folding edges, where contacted with heavily calcified masses at the right coronary sinus, resulting in high maximum principal stress. Local sharp spiked calcifications facilitated rapid crack propagation. The elastic moduli of calcification significantly influenced balloon expansion behavior and crack morphology. The simulation case of the calcific elastic modulus was set at 12.6 MPa could closely mirror clinical appearance of expansion behavior and crack pattern. Furthermore, the case of semi-compliant balloons introduced an alternative rupture mechanism as pinhole rupture, driven by local sharp spiked calcifications. ConclusionsThe computational model of virtual balloons could effectively simulate balloon dilation behavior and burst mode during TAVR pre-dilation. Further research with a larger cohort is needed to investigate the balloon morphology during pre-dilation by using this method to guide prosthesis sizing for potential favorable outcomes.

Intelligent decision support system for assessing the risk of failures of complex technical systems

A decision support system has been developed that allows assessing the risk of failure of elements and components of complex technical systems using artificial intelligence. The proposed algorithm for the functioning of a decision support system implements the task of automating the process of assessing the technical condition of complex systems. The use of the proposed decision support system for assessing the technical condition of complex systems will improve the reliability of operating systems with insufficient information about their technical condition.

Research into the Peculiarities of the Individual Traction Drive Nonlinear System Oscillatory Processes

Auto-oscillations may occur in moving vehicles in the area where the tire interacts with the support base. The parameters of such oscillations depend on the sliding velocity in the contact patch. As they negatively affect the processes occurring in the electric drive and the mechanical transmission, reducing their energy efficiency, such processes can cause failures in various elements. This paper aims to conduct a theoretical study into the peculiarities of oscillatory processes in the nonlinear system and an experimental study of the auto-oscillation modes of an individual traction drive. It presents the theoretical basis used to analyze the peculiarities of oscillation processes, including their onset and course, the results of simulation mathematical modeling and the experimental studies into the oscillation phenomena in the movement of the vehicle towards the supporting base. The practical value of this study lies in the possibility to use the results in the development of algorithms for the exclusion of auto-oscillation phenomena in the development of vehicle control systems, as well as to use the auto-oscillation processes onset and course analysis methodology to design the electric drive of the driving wheels.

A Numerical Study of the Dynamic Crack Behavior of Brittle Material Induced by Blast Waves.

Blast stress waves profoundly impact engineering structures, exciting and affecting the rupture process in brittle construction materials. A novel numerical model was introduced to investigate the initiation and propagation of cracks subjected to blast stress waves within the borehole-crack configuration. Twelve models were established with different crack lengths to simulate sandstone samples. The influence of crack length on crack initiation and propagation was investigated using those models. The linear equation of state was used to express the relationship between the pressure and density of the material. The major principal stress failure criterion was used to evaluate the failure of elements. A triangular pressure curve was adopted to produce the blast stress wave. The results indicated that the pre-crack length critically influenced the crack initiation and propagation mechanism by analyzing the stress history at the crack tip, crack propagation velocity, and distance. The inducement of a P-wave and S-wave is paramount in models with a short pre-crack. For long pre-crack models, Rayleigh waves significantly contribute to crack propagation.