Journal of Engineering and Thermal Sciences
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Statistical review of literature sources on carbon emissions during the CSPB based on knowledge graphs
Get PDFThe construction industry, a significant contributor to global carbon emissions, is pivotal in implementing carbon reduction strategies. This study delves into the carbon emissions associated with the construction stage of prefabricated buildings (CSPB), a burgeoning field of research. Utilizing the CiteSpace knowledge graph visualization software, we comprehensively analyzed literature from the Web of Science (WoS) database. Our study encompasses several vital dimensions: academic paper publication volume, keyword co-occurrence network, keyword co-occurrence network clustering, and citation burst visualization and analysis. The findings indicate that the topic of carbon emissions in prefabricated building construction is gaining increasing attention globally. Over the past decade, related literature has surged by an average annual growth rate of 41.42 %. Key research themes have emerged around the quantification of carbon emissions, construction methodologies, influencing factors, mitigation strategies, the use of prefabricated components, and predictive studies on emissions. These insights underscore the evolving focus and critical importance of this field in global sustainability efforts
Investigation of the load’s variation rate effect on the efforts and moment intensity factors values in a cylindrical shell with a longitudinal crack
Get PDFThe limit equilibrium of a cylindrical shell with a longitudinal crack under the action of a time-varying load is considered. Dynamic coefficients of intensity of forces and moments near the tips of cracks in shells made of steel, copper, and cast iron are calculated. The influence of the mechanical characteristics of the shell material and the rate of load variation on their behavior is analyzed
Application of ultrasonic vibration in magnesium alloy lap welding
Get PDFIn order to enhance the performance of magnesium alloy and galvanized steel welds, ultrasonic vibration was applied to the laser welding process, and the effect of ultrasonic on mechanical properties was verified through experimental methods. The laser welding system for the lap weld seam was designed, and the ultrasonic vibration module and image detection module were added, which can obtain the influence of ultrasonic vibration on the molten pool area. Under the conditions of ultrasonic vibration power of 1000 W and 0 W, the characteristics of the weld pool area, metallographic structure, tensile strength, fracture morphology, hardness, residual stress, wear resistance, and corrosion resistance of the weld specimen were compared. The image data acquisition structure indicated that ultrasonic vibration can effectively reduce the ineffective area of the molten pool and make the energy in the molten pool more concentrated. Under the influence of ultrasonic vibration, the maximum molten pool area decreased to 5.38 mm2, with a variation range of 3.9 %, and the proportion of pores was greatly reduced. Research found that ultrasonic vibration can significantly improve the microstructure characteristics of the fusion welding zone, with an average grain size reduced to 23 μm. The reduction of grain size and refinement of microstructure were beneficial to the improvement of mechanical properties of magnesium alloy joints, with a yield strength increase of 6.5 %. Ultrasonic vibration had little effect on the hardness of the heat affected zone, it can increase the average hardness of the weld zone by more than 5 % and reduce the maximum residual stress by more than 50 %. Under different pressure and friction speed conditions, the maximum wear amount can be reduced by more than 25 %. At the same time, the resistance to oxidation corrosion and electrochemical corrosion also can be improved to a certain extent
Mathematical modeling of piezoceramic spherical shell actuator for vibration generating devices
Get PDFThe article examines the relevance of piezoceramic spherical shell actuators, which provide a high level of accuracy and stability in the generation of vibrational oscillations over a wide range of amplitude-frequency characteristics. The spherical shape of these actuators is chosen because it allows for uniform distribution of mechanical stresses across the actuator’s surface, thereby enhancing its durability and efficiency compared to traditional flat or cylindrical designs. The study presents analytically derived mathematical models and formulas for determining the electrical impedance of piezoelectric elements and analyzes the dependence of the amplitude of electrical impedance on frequency and the charge ratio on the polarized surfaces of the spherical piezoceramic element. The proposed model enables the determination of electrical impedance as a function of cyclic frequency and various parameters (geometric, physical and mechanical, electrical) of the actuators. The study establishes that spherical shell actuators exhibit a higher quality factor (2-2.5 times greater than disk actuators and 1.4-1.8 times greater than cylindrical actuators) and a significant reduction in impedance (2.5-7 times lower) at electromechanical resonance frequencies around 2.4 kHz. Furthermore, spherical actuators demonstrate 20-30 % better resistance to deformation and 15-25 % lower susceptibility to local resonances compared to other actuator shapes, which enhances operational stability and vibration generation accuracy
Maintenance decision-making and its relevance in engineering asset management
Get PDFEngineering asset management (EAM) has received a lot of attention in the last few decades. Despite this, industries struggle to identify the best strategies for maintaining assets. The decision-making around selecting a relevant maintenance strategy generally considers factors like risk, performance and cost. Risk management is, usually, largely subjective and industries consequently make investments in a subjective manner, making the allocation of budget unstructured and arbitrary. Generally, industries focus only on either overt risks or basic performance of assets, thus creating uncertainties in the decision-making process. Recently, however, maintenance decision-making has evolved from a subjective assessment, chiefly dependent on expert opinions, to utilizing live-data-sensor technology. The attitude towards component failures and how to address them has changed drastically with the evolution of maintenance strategies. Additionally, the emergence and use of several tools and models have assisted the drafting and implementation of effective maintenance strategies. These advancements, however, have only considered discrete parameters while modelling, instead of using an integrated approach. One of the primary factors which can address this shortfall and make the decision-making process more robust is the economic element. To enable an effective decision-making process, it is imperative to consider quantifiable determinants and include economic parameters while drafting maintenance policies. This paper reviews maintenance decision-making strategies in EAM and also highlights its relevance through an economic lens
Testing the effect of functional orthopedic appliance Simões network 6 (SN6) through surface electromyography on rest mandibular position – a pilot study
Get PDFThe maintenance of the lower level of muscle contraction is fundamental for the development and health of the stomatognathic system (SS). Malocclusion leads to unbalance muscle activity, since Class II treatment is not the most prevalent malocclusion in the general population but is the more frequent to search for treatment in dental offices and the most prevalent skeletal component in the class II malocclusion is the retrognathia this pilot investigation aims to study the effect of rest electric activity of bilateral anterior temporal, masseter and suprahyoid muscle in individuals undergoing class II treatment with functional orthopedic appliance Simões Network 6 (SN6). Surface electromyography recordings of bilateral anterior temporal, masseter and suprahyoid muscle in rest position was obtained before and 8 minutes after the functional appliance insertion in mouth. Results showed improvement of electric muscle activity in rest position and balance of bilateral muscle electric activity in all muscle. Based on the preliminary results it can be conclude that jaw functional orthopedics (JFO) provides alteration of the resting records in the mandibular rest position of the studied muscles, indicating relaxation of the muscles studied and a more symmetrical electric activity. Further studies are necessary for a better understanding of the effects of functional orthopedic appliances in the electric activity of stomatognathic muscle in the mandibular rest position
Ultrasonic multi-frequency piezoelectric transducer for generation different sound pressure field patterns
Get PDFThe paper represents numerical and experimental investigation of ultrasonic piezoelectric transducer which operation is based on three different vibration modes. Multi-frequency operation of the transducer allows to obtain sound pressure fields with different patterns, sound fields intensities and frequencies which allows to obtain more flexible and adjustable agglomeration process of fine and ultrafine. Results of numerical investigations have shown that vibration modes of transducer at 25.83 kHz, 34.73 kHz and 52.41 kHz frequencies are suitable for acoustic pressure generation. Moreover, the calculations revealed that at these frequencies sound pressure levels (SPL) reaches up to 142 dB while SPL patterns at different frequencies are different. Experimental investigations have confirmed results of numerical investigations and showed that resonant frequencies of transducer are at 25.65 kHz, 31.1 kHz, 50.8 kHz while SPL values reaches up to 132.5 dB
Influence of the welding cycle on the parameters of material damageability of the high-strength steel connection with an austenitic seam
Get PDFThe distribution of macrohardness of the material of a welded joint made of high-strength steel in the vicinity of a weld with an austenitic structure has been studied. The characteristics of the material's homogeneity, technological damageability, and the intensity of its growth have been determined using the LM-hardness method. The obtained characteristics of the material are considered according to the distance from the axis of the weld. It is shown that using the dispersion of important physical and mechanical characteristics to analyze the material homogeneity makes it possible to consider the differences in relation to the base material, structure, and properties of the weld. The method used in the work to assess the material damageability can be used for a welded joint that is heterogeneous in material. The obtained results are applicable in developing the technique of heterogeneous weld joints made of high-strength steels, as well as in the study of existing welded critical structures of long-term operation, in particular, main pipelines
Fault diagnosis algorithm based on GADF-DFT and multi-kernel domain coordinated adaptive network
Get PDFTo address the problems of low detection accuracy of rolling bearings under different loads and the difficulty of effectively identifying the lack of labelled data, a rolling bearing fault diagnosis method combining GADF-DFT image coding and Multi-kernel domain coordinated adaptation network is proposed. Firstly, the vibration signal is converted into a two-dimensional image using GADF coding technology, and then the GADF image is converted into the frequency domain using discrete Fourier transform to extract deeper feature information. Combined with the multi-source domain adaptive method, the public feature extraction module is used to initially achieve feature mining of the image; the MK-MMD algorithm of the domain-specific adaptive module reduces the difference in feature distribution between the source and target domains; and the final classification difference minimization module reduces the problems caused by the classification errors that may be generated by the different domain classifiers due to the fact that the data samples are located near the category boundaries. The test uses the Case Western Reserve University dataset and divides the dataset with different operating conditions as the source and target domains, and the test results show that the proposed model demonstrates its effectiveness in responding to the complex operating condition changes in rolling bearing fault detection in multiple operating condition migration tasks, good adaptability and robustness, and is able to achieve accurate fault diagnosis under different operating conditions
Effect of AVL-based time-domain analysis on torsional vibration of engine shafting
Get PDFThe torsional vibration of the shaft system in hybrid car engines has a significant impact on the overall performance of the vehicle, and it is more complex in hybrid cars compared to traditional cars. Traditional methods for torsional vibration analysis of shaft systems have significant limitations and cannot handle nonlinear and transient problems. To explore the torsional vibration characteristics of hybrid vehicle shaft systems, a simplified engine shaft system torsional vibration equivalent model is innovatively constructed. In addition, a method for quickly determining the confidence level of the torsional vibration equivalent model is proposed. Additionally, the transient dynamic characteristics of a multi-body dynamics model containing a dual mass flywheel are analyzed in depth using the time-domain solver of AVL-exact PU. The results demonstrated that the simulation of 4th and 6th harmonics resonated at critical speeds of 4,195 rpm and 2,771 rpm, respectively, with angular displacement amplitudes of 0.141 deg and 0.047 deg. In fact, resonance was measured at 4,250 rpm and 3,040 rpm, with amplitudes of 0.14 deg and 0.052 deg. These two were basically consistent in key parameters. When the shaft model was started under operating conditions, the amplitudes of harmonics 1, 2, and 4 were basically consistent below 750 rpm, and there were slight differences after 750 rpm. Therefore, the AVL-based engine torsional vibration simulation model constructed has high credibility