Service Life Period Research Articles

Reliability-oriented design of PCM thermodimensionally stable space structures

The problem of ensuring the specified thermo-dimensional stability of structures from laminated polymer composite materials for the service life period is considered. A method of reliability-oriented design of a thermo-dimensionally stable composite structure is proposed, according to which its design parameters are set with regard to the possibility of obtaining thermal strain properties under specific processing and the changes of these properties for the operational conditions and duration of using the article as intended. Within the framework of the presented approach, the features of design upon the dimensional accuracy and stability criterion when meeting the requirements of strength and stiffness are discussed, an algorithm of a packaged solution of the design task is given.

Effect of multi-walled carbon nanotubes reinforcement on self-healing performance of natural rubber

Abstract This work is motivated by the desire to restore the quality of rubber-based product properties with the intention of prolonging the service life period, thus helping create a sustainable environment by proposing effective rubber waste management. This study experimentally investigated an intrinsically self-healing zinc thiolate grafted natural rubber (NRZT) compound filled with multi-walled carbon nanotubes (MWCNT) to assess its influence on mechanical properties and self-healing performance. The MWCNT loading varied to 0, 2, 4, 6, and 8 phr. The Equilibrium swelling test was used to quantify the amount of ionic and covalent crosslinks formed. Fourier Transform Infrared (FTIR) spectra were used to detect the presence of MWCNT in the compound. The mechanical properties computed by the tensile and tear strength tests showed that the incorporation of MWCNT increased both properties up to three and twofold, respectively. However, as expected, the elongation at break (Eb) value was reduced. The unfilled sample showed that it can heal up to ∼98 %, measured from the tensile strength. However, the healing efficiency obtained from tensile strength reduces to ∼88 % by incorporating 2 phr MWCNT. The Eb and its self-healing efficiency gradually decreased as the MWCNT amount increased. All samples showed outstanding properties under the tearing mode, where the healed samples produced higher tear strength (>100 % healing) than the initial value. Scanning Electron Microscopy (SEM) micrographs revealed a noticeable gap along the healed cut line with increased MWCNT numbers, possibly due to the lower reaction between polymerized zinc thiolate (PZTh) radicals with zinc thiolate (ZT) and rubber molecules. The work aims to investigate the influence of MWCNTs on the mechanical and healing performance of self-healing NR composites by comparing them to their unfilled sample.

Flexural Behaviour of FRC Beams Wrapped With FRP

Structural elements such as beams, slabs and columns may require strengthening during their service life period. A concrete structure may need strengthening for many reasons such as to increase live load capacity, to add reinforcement to a member that has been unsigned or wrongly constructed. The FRPs have various advantages like, high strength to weight ratio, corrosion resistance and ease of installation and flexibility in its use. FRP material which are available in the form of sheet are being used to strengthen a variety of RC elements to enhance the flexural, shear and axial load carrying capacity of these elements. The objective of this experiment is to strengthen the RC beams using fibres and FRP sheets in flexure. In this experimental program CFRP and GFRP sheets were applied to the bottom surface and sides of the concrete beam with different configuration and their performance in flexure were studied. In this experimental program eight RC beams of size 1500 x 150 x 200mm were casted with two 10mm dia. bars as tension zone, two 8mm dia. bars as compression zone and 8mm dia. bars @ 200mm c/c spacing as shear reinforcement. The experimental result shows that the flexural strength of FRP wrapped beams were increased in the range of 23.49% to 67.9% in comparison with the flexural strength of the control beam (unwrapped). The flexural strength of the beam wrapped with the single layer CFRP at the soffit and around the sides (for full depth of the beam) and beam wrapped with the single layer GFRP at the soffit and around the sides (for full depth of the beam) exhibits better performance compared with other FRP beams and increase in flexure was 67.9% in comparison with the capacity of the control beam.

Optimization of stone matrix asphalt mixture design based on fracture mechanics approach

Low-temperature cracking is one of the most common pavement distresses that occurred in a short period of service life and is known as premature distress. Stone matrix asphalt (SMA) with gap gradation, which has high strength and rutting performance, should also perform well against low-temperature cracking. So in this research, the criteria of SMA mixture design based on the National Cooperative Highway Research Program (NCHRP) 9–8 were optimized in a way so that SMA has the best performance against low-temperature cracking. Therefore, the optimization process was carried out using the response surface method (RSM) considering the combined effect of compaction energy (Ndesign) and binder content as mixture design factors. The fracture evaluation was done based on stress and energy. So critical stress intensity factor (KIC) and critical fracture energy (Gf) were used as fracture evaluation parameters. After conducting the tests and analyzing the results, it was found that 6.09 % binder with Ndesign = 78 leads to a design with a desirability of 0.869, which passed all the NCHRP 9–8 criteria of the mixture design in line with the maximum fracture performance.

A Highly Sustainable Timber-Cork Modular System for Lightweight Temporary Housing

In recent years, global society has been subjected to great change due to unpredictable events such as pandemics, migrant flow, urban homeless, wars, and natural disasters. There has been an increased demand for fast and easily constructed buildings characterized by limited space and used for a limited time, modular and flexible self-assembly homes that are reusable without compromising comfort and environmental sustainability. A highly sustainable timber-cork modular system for lightweight temporary housing (LTH) is proposed in this paper. The structure of the proposed LTH was designed as a succession of modular timber portal frames composed of spruce boards hinged together. The concept of the prototype was a full modular shelter. It was possible to interchange every piece of the building, the structural elements, and the walls with each other. Due to the modularity of the elements of which the shelter was composed, this system could offer different solutions to the events above. The proposed LTH was analyzed in terms of its structural, thermal, and environmental performance. The structural system is very reminiscent of the platform frame, characterized by a light load-bearing frame consisting of solid timber uprights and crosspieces connected to the internal frame by means of a mechanical connection. The structural FEM analysis highlighted the structure’s capacity to withstand wind with a velocity of 72 m·s-1, corresponding to the F3 of the enhanced Fujita Scale (EF Scale) of tornado damage intensity. The thermal analysis highlighted a yearly energy use of 430.49 kWh to maintain a set-point temperature indoors of 20-26°C compared with a yearly energy use of 625.93 kWh for a common container house (CH) with the same dimensions under the same environmental conditions. Finally, a Life Cycle Analysis comparison between the proposed LTH and the CH was carried out by means of the One Click LCA software. Two different scenarios of service life were considered: one of 10 years and the other of 5 years. The results highlighted the higher sustainability of the proposed LTH than that of the CH for the required service life (Req SL) period. In particular, the calculated greenhouse gas emissions of the LTH (3.52ž103 kgCO2 eq) were less than 1/2 of the gas emissions of the CH (8.53ž103) for a Req SL of 10 years and about 1/3 for a Req SL of 5 years. Furthermore, the LTH showed a value of biogenic carbon storage (7.76E2 kgCO2) about 6 times bigger than the temporary house container (1.31E2 kgCO2). Doi: 10.28991/CEJ-2022-08-10-020 Full Text: PDF

Optimal Design Method for Vessel-Bridge Collision Based on Life-Cycle Theory

As structures crossing waterways, bridges are obstacles to vessels. Vessel-bridge collisions are inevitable. They not only involve the safety of vessel passage but also seriously affect the safe operation of bridges. Vessel-bridge collisions cause not only huge economic losses and casualties but also severe political and environmental losses. Vessel collision safety of existing and new bridges is one of the key technical problems that engineers and bridge managers must solve. Comprehensive consideration of vessel-bridge collision risk loss and structural performance in the design stage to achieve optimal cost over the life cycle is an important aspect of bridge design. Based on the current life-cycle design theory of engineering structures, this paper proposes a theoretical framework for vessel-bridge collision optimization design based on the life cycle, which includes three parts: vessel-bridge collision probability analysis, vessel-bridge collision vulnerability analysis, and vessel-bridge collision hazard. Taking the minimum cost of the bridge structure in the design service life period as the objective function, the optimization design model and design process of vessel-bridge collision based on whole life are established, and the key problems to be solved in each part are expounded.

Development of statistical modeling of the pipelines' reliability projections of the main heat networks, according to the period of operation and diameter

Using the method of statistical modeling of pipeline reliability, the statistical model for forecasting the dependence of the failure parameter of pipelines of main heating networks on the service life and diameter was developed and analyzed. This method includes two techniques. The first allows to obtain predictive dependences of pipeline reliability indicators for systems that include sections of different diameters with different service life periods and actual data on damage over several years. The second increases the correctness of the obtained dependences by optimizing the service life step in the study of damage to heat pipes. As a result of the study, the dependence of the reliability of main pipelines on the service life and diameter was established. The condition and forecast values of the specified indicator of reliability of main heat pipelines, and also dynamics and range of its changes are defined. The average value of the failure rate parameter increases from 0.23 1/km year (diameter 300 mm) to 0.62 1/km year (diameter 800 mm), which is 2.7 times larger than the pipes with the diameter 300 mm. The multiplicity of changes in the value of the parameter of the flow of failures was also established in accordance with the change in the diameter of the pipelines. According to the developed statistical model the dependence for calculation of the forecast of quantity of damages of the main heat pipelines according to their service life, diameter and length is established. This will increase the reliability of heating systems and effectively plan the cost of material, technical and labor resources. The given method can be used to assess the forecast of the reliability of pipelines, respectively, of their diameters for other engineering systems and networks

Fuzzy mamdani logic inference model in the loading of distribution substation transformer SCADA system

<span id="docs-internal-guid-152e332e-7fff-7073-a541-1d420decb47b"><span>The research objective of supervisory control and data acquisition (SCADA), with fuzzy Mamdani logic simulation on the loading section of distribution transformer substations. Data acquisition is available when saving SAIFI SAIDI data and storing the results of monitoring equipment. The method used is Mamdani fuzzy logic, there are two input variables, namely current and voltage devices. The membership function in Mamdani fuzzy logic has been created based on the input current and voltage variables. Currently: parameter {0, 600} low is created {0, 350, 450, 600}, normal {400-650} parameter is created {400, 500, 550, 650}, parameter high {≥600} is created {600, 650, 750, 1000}, when determining the voltage: low {≤10.5} parameters {0 4 7 10.5}, normal {9-14} parameters {9, 10, 13, 14} and high {≥13} - parameters {13, 14, 15, 16}. Based on the results of the Mamdani logic rule test on the output current containing a transformer and a voltage sensor, the results obtained are IF (normal current; (630) AND voltage (high); (13.2) (high load transformer). The components in the simulation tool include miniature substations made with the 1A travel substation model, 3A substation as the main substation, the relay as distribution substation as the monitoring application. Telestatus and Telecontrol use a microcontroller. Initial scenario. After substation is resumed, data is stored after downtime, service life, duration, and data period. Initial scenario After substation is resumed, data is stored after downtime, service life, duration, and data period.</span></span>

The expired period of Liquefied Petroleum Gas (LPG) rubber hose supports consumer safety aspects

Liquefied Petroleum Gas (LPG) rubber hose has the corrosive characteristic with hydrocarbon compounds (butane and propane). This makes LPG rubber hose has an expired period. Standards or technical specifications are needed to guarantee the quality of the product and increasing product safety. Until now, the expired period of LPG hose has not been regulated in the Indonesian National Standard (SNI). This study aims to analyse expired period of LPG rubber hose for gas stoves. In this study, the descriptive qualitative method is used based on primary data (questionnaire and interview) and secondary data (literature study). The result of this study concluded that the determination of LPG rubber hose expired period based on shelf life and service life. The service life of rubber hose will vary due to different raw materials, additives, and usage conditions (time, temperature, pressure, and environment). Seventy-five percent (75%) of LPG rubber hose industry respondents conducted research on LPG rubber hoses service life and recommended service life period is one year.

Risk assessment of aging offshore jacket platform group: a case study on “B” Field platforms

Offshore jacket platforms are designed to fulfil their intended purpose in oil and gas exploitation at designated service life periods. During the operational development, a number of field operators extend their platform service life if the reserves are still available. This technical paper proposes the method to assess the structural integrity of several aging platforms in a field with a simplified approach. Taking the case of “B” Field platforms installed in the mid-1990s, the detailed procedure and example are discussed thoroughly. Five indicators furnished with quantification procedures are also presented to propose the ranking methodology. This paper also proposes the method of jacket platforms grouping based on several similarity criteria. The results of this approach can be used as a baseline for more detailed structural integrity assessment for each group representation.

СРОК СЛУЖБЫ КАК ПАРАМЕТР ОБОБЩЕННОГО УЗЛА ПРИ РАСЧЕТЕ ИНДЕКСА ТЕХНИЧЕСКОГО СОСТОЯНИЯ ЭНЕРГЕТИЧЕСКОГО ОБОРУДОВАНИЯ

In accordance with the energy digitalization program, the single integral indicator - the technical condition index (TCI) - is used for the assessment of the technical condition and physical wear and tear of energy equipment. Service life is one of the components of this index. The article discusses the influence of the service life of power equipment on the final value of the index, explains the contradictions in assessing wear on TCI and on the lifetime indicators. For aging equipment that has reached the end of its design life, it is suggested to use the individual service life or individual period of safe operation extension as the normal value of service life under the assessment of TCI.

Wear Behavior of a Bio-inspired Bearing for off-center Loads

Misalignment is one of the most common causes of wear in bush bearings. Design improvements have been proposed by many researchers. Unfortunately, it did not efficiently reduce the misalignment. Classic geometrical designs sometimes reach their limits. For this reason, a bio-inspired design is proposed to solve the impediment. In this article, a bio-inspired bearing suited to misalignment was tested and compared to a classical bush bearing. The contact pressures of both bearings were compared with static Finite Element (FE) simulations for off-center load. Due to the complex shape of the involved contact, the performances of both bearings were also studied over time. Their wear behaviors were predicted with a numerical method. The methodologies emplaced to simulate the wear were described in this paper. Particularly, the wear coefficient determination obtained by experimental testing was detailed. The pressure value, the contact zone and the wear depth were compared and discussed. The wear results for the classical bearing are in accordance with the literature. The simulations show a deeper wear on the classical bush bearing than on the bio-inspired bearing. This leads to a longer period of service life for the bio-inspired bearing.

Analysis of resistance to accelerated aging of the top layer of small-sized concrete elements. A case study

Selected series of concrete pavement blocks and flags were subjected to a test of 500 atmospheric aging cycles under simulated conditions, corresponding to a period of 10 years in natural conditions. In order to test the resistance of pavement texture and to determine material changes, comparative tests of physical and mechanical properties were carried out at the initial state and after the test. The following features were subjected to testing: absorbability, bulk density, compressive strength and, for selected samples, the pull-off strength of the textures after further 100 cycles. Additionally, for the selected textures, changes of surface morphology were analyzed using scanning electron microscopy (SEM), and the changes of pore structure were examined using mercury intrusion porosimetry (MIP). The results confirmed good adhesion of the textures to the substrate and good resistance to climatic impact. The absorbability of textures slightly increased, and there were slight changes in their pore structure. Scanning analyses enabled to identify surface defects in the form of microcracks and binder losses, but they did not adversely affect the positive results of macroscopic examination. The presented aging tests enabled to diagnose the resistance of construction products to the atmospheric environment in considerably shorter time than the assumed period of service life.

Design method for reinforced concrete structure durability with the use of safety coefficient by service life period

The given method uses the safety coefficient by service life period and similar principles as for stochastic method. Moreover, the problem of forecasting the safety is examined in a deterministic form. The given option for the solution is compact in terms of design on an applied level in the format of the boundary conditions method, keeping the efficient control of safety within the service life period. This method has the advantage to design reinforced concrete structures for specified service life period. The proposed method is also applicable for the design of reinforced concrete elements of hydraulic structures in cases when the application of the other stochastic methods would be very complicated. The advantage of the given method is allowing including the stochastic nature of loading parameters and material strength.

Behaviour of green ultra-high-performance concrete beams with corrosion resistant alloy steel (MMFX) bars

The aim of this study is to investigate the efficiency of using green ultra-high-performance concrete (GUHPC) with corrosion resistant alloy steel (MMFX) Bars in overcoming concrete cracking and steel corrosion, which will help in reducing inspection, maintenance, and repair works. To do so, a nonlinear finite element (FE) analysis was carried-out to model full-scale concrete beams which are often subjected to cracks during its service life time. The obtained results were compared with experimental data and the comparison was most satisfactory. In addition, a comparison was made between the proposed materials and traditional reinforced concrete in terms of crack widths, the intensity of cracks and service life period. The obtained results showed that using GUHPC and MMFX as a construction material in concrete structures provides high stiffness, high strength, enhanced service life and crack control beside its cost efficiency.

RILEM TC 247-DTA round robin test: carbonation and chloride penetration testing of alkali-activated concretes

Many standardised durability testing methods have been developed for Portland cement-based concretes, but require validation to determine whether they are also applicable to alkali-activated materials. To address this question, RILEM TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ carried out round robin testing of carbonation and chloride penetration test methods, applied to five different alkali-activated concretes based on fly ash, blast furnace slag or metakaolin. The methods appeared overall to demonstrate an intrinsic precision comparable to their precision when applied to conventional concretes. The ranking of test outcomes for pairs of concretes of similar binder chemistry was satisfactory, but rankings were not always reliable when comparing alkali-activated concretes based on different precursors. Accelerated carbonation testing gave similar results for fly ash-based and blast furnace slag-based alkali-activated concretes, whereas natural carbonation testing did not. Carbonation of concrete specimens was observed to have occurred already during curing, which has implications for extrapolation of carbonation testing results to longer service life periods. Accelerated chloride penetration testing according to NT BUILD 443 ranked the tested concretes consistently, while this was not the case for the rapid chloride migration test. Both of these chloride penetration testing methods exhibited comparatively low precision when applied to blast furnace slag-based concretes which are more resistant to chloride ingress than the other materials tested.

Modeling and Simulation of Film Cooling Effectiveness on a Flat Plate

Abstract Gas turbine components are exposed to very high temperature and pressure and require effective cooling to ensure the effective, efficient and prolonged service life period. In the present work ANSYS FLUENT was employed to numerically investigate performance of cooling on a flat surface using circular coolant hole with entrance of coolant at different blowing ratios entering at 300 forward and backward directions. The proposed simulative methodology was validated with a zero velocity coolant entrance which showed no change in the plate temperature, which was expected and also found. The results found were also validated using various experimental results available in different literatures. The simulation results indicated that orientation of cooling hole governs the extent of film cooling effectiveness. The results of this work had a mixed outcome. Forward coolant entrance provided better centerline cooling effectiveness but spreadability was better for backward entrance

Assessment of individual reliability indicators and rational service life of agricultural tractors

Nowadays, a case-by case approach to optimizing and rationalizing the machine usage parameters is relevant. One of the ways to improve the efficiency of the machine and tractor fleet operation with regard to individual reliability indicators is to assess the rational tractor service life. According to the proposed model, the tractor is to be decommissioned when it ceases making a profit. Aiming to test the proposed model, ten 3 kN class tractors, operated in agricultural enterprises in the Vologda district of the Vologda region, have been under research for five years. As a result, it has been found out that all the tractors under study have different reliability and, consequently, different rational service life periods.

Cost Estimation Method of Coastal Navigation Sign Measurement and Control Project Based on Big Data's Analysis

Zheng, S.; Wang, L.; Chen, R.; Xing, F., and Chen, J., 2019. Cost estimation method of coastal navigation sign measurement and control project based on Big Data's analysis. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 830–835. Coconut Creek (Florida), ISSN 0749-0208.The method for estimating and controlling the coastal navigation mark measurement and control cost of the coastal navigation mark measurement and control project is to maintain the safety of the coastal navigation mark measurement and control project, to reduce the cost of the project and to guarantee the service level. The traditional cost estimation method of the coastal navigation mark measurement and control project is based on the experience-based evaluation of the cost prediction model of the coastal navigation mark measurement and control engineering, which cannot effectively meet the principle of minimizing the present value of the measurement and control cost of the coastal navigation mark and the maximization of the state index during the service life period. In this paper, a method for estimating the cost of a coastal navigation mark measurement and control project based on the characteristics of large data correlation is proposed, and the measurement and control model of the conventional coastal navigation mark is designed. Cost estimation model of coastal navigation mark measurement and control project based on performance and energy supply survival period assessment model based on comprehensive coastal navigation mark measurement and control strategy. The cost estimation model of the coastal navigation mark measurement and control engineering is designed by using the first-order Bessel function, a reliable index evaluation equation of the cost all-sample regression analysis is obtained, the measurement and control cost of the coastal navigation mark, the user cost and the social cost are calculated. The cost present value of the measurement and control project of the coastal navigation mark is minimized as the objective function, and the financial constraint and the performance constraint are obtained as the boundary conditions. The plan optimization of the cost of the measurement and control engineering of the coastal navigation mark is realized, and the measurement and control scheme of the coastal navigation mark with the minimum cost present value is obtained under the limited financial resources. The numerical simulation results show that the model can improve the reliability and reliability of the measurement and control engineering structure of the coastal navigation mark, optimize the measurement and control cost of the coastal navigation mark, and obtain the minimum measurement and control scheme of the coastal navigation mark with the minimum cost present value under the limited financial resources, thus saving the measurement and control cost of the coastal navigation mark by 15%.

Distribution of Magnetic Field Parameters in the Surface Layer of the Material of Reaction Furnace Coils after Operation Period

One of the main reasons for the limited service life period of the reaction furnace coils is the carburization of the surface layers, which leads to a decrease in the performance characteristics of the pipe material, decrease in plasticity, generation of internal stresses, change in the metal structure. Therefore, monitoring the state of coils surface in order to detect critical parameters of the carburized layer thickness, using non-destructive methods of control is relevant. The results of the distribution of magnetic parameters over the depth of the carburized layer in the fragments of pipes made of steel 20Х25Н20C2, operated under furnace conditions at high temperatures, for 1300, 6000, 8000, 10000 hours are presented in the article. Analysis of the results showed that the magnetic properties are manifested only in the surface layers of the reaction furnace tubes. At the same time, the longer the service life period, the deeper is the layer exercising the magnetic properties and the higher in this layer the values ​of the constant magnetic field intensity. Analysis of magnetic properties distribution in all studied pipe fragments, both from the inner and from the outer side, showed the non-uniformity of the constant magnetic field intensity distribution, while zones of extremely high values ​are observed. The layer-by-layer surface removal in these zones with the determination of the resultant constant magnetic field intensity showed that there are critical values of the carburization depth, after which a sharp increase of this parameter is registered. These results can be used as a method for carburization depth determination, and also used to develop criterion for rejecting coils of reaction furnaces.