Hasil untuk "Mechanical engineering and machinery"

Ammar Mrabti, Ramdane Younes, Nouredine Ouelaa et al.

Fault detection in rotating machinery is critical to reliability and safety. However, it faces difficulties due to complex, noisy fault signatures, non-stationary behavior, and the impracticality of obtaining large labeled datasets, limiting the effectiveness of both traditional and deep learning-based methods in real-world applications. This paper introduces a novel approach that combines Variational Mode Decomposition (VMD) and Long Short-Term Memory (LSTM) networks to improve gear and bearing defect detection, filling a gap in fault diagnostics by effectively handling limited training data. VMD decomposes signals into intrinsic mode functions (IMFs), while LSTM classifies fault types and severity levels based on time-domain features extracted from the IMFs. Tested on the Case Western Reserve University Dataset (CWRUDS) for bearing defects and the Laboratory of Mechanics and Structures Dataset (LMSDS) for combined gear and bearing defects, the method outperforms vibratory analysis and conventional classifiers such as MLP, 1D-CNN, 2D-CNN, and standalone LSTM. The results show that the VMD-LSTM model is superior at reliably detecting defects and accurately diagnosing faults in complex, data-limited scenarios, making it a promising solution for machinery health monitoring.

فرهاد وحیدی نیا

در این مقاله، عملکرد انرژی و اگزرژی یک کلکتور خورشیدی سهموی خطی حاوی روغن حرارتی با دریافت‌کننده مجهز به پره داخلی و توربولاتور ستاره‌ای‌شکل به صورت عددی مطالعه شده است. جریان سیال داخل لوله جاذب کلکتور به صورت مغشوش و عدد رینولدز در بازه‌ی 104×2 تا 105 در نظر گرفته شده است. به منظور شبیه‌سازی جریان سیال از نرم‌افزار انسیس- فلوئنت استفاده شده است. در این مقاله از یک لوله جاذب جدید مجهز به پره داخلی و توربولاتور ستاره‌ای شکل با پره‌های طولی مستطیلی استفاده شده و لوله جاذب پره مرکب نامیده شده است. بر این اساس عملکرد انرژی و اگزرژی کلکتور با وجود و یا عدم وجود پره و توربولاتور در داخل لوله جاذب در 6 حالت مختلف مقایسه و تحلیل شده است. بررسی نتایج نشان داد که کلکتور با لوله جاذب پره مرکب با پره داخلی بزرگ بیشترین بازده انرژی و اگزرژی را دارد. همچنین بیشترین افزایش بازده انرژی و اگزرژی کلکتور هنگام استفاده از این نوع لوله جاذب به‌جای لوله جاذب ساده به ترتیب برابر با 96/5 و 76/6 درصد است. از طرفی دیگر نتایج نشان داد که مقادیر معیار ارزیابی عملکرد برای لوله‌های جاذب پره مرکب با پره داخلی بزرگ و لوله جاذب پره داخلی بزرگتر از 1 و بیشترین مقدار آن 62/1 نتیجه شد.

Lei Zhang, Yiru Huang, Leiming Yan et al.

Making computers automatically extract latent scientific knowledge from literature is highly desired for future materials and chemical research in the artificial intelligence era. Herein, the natural language processing (NLP)‐based machine learning technique to build language models and automatically extract hidden information regarding perovskite solar cell (PSC) materials from 29 060 publications is employed. The concept that there are light‐absorbing materials, electron‐transporting materials, and hole‐transporting materials in PSCs is successfully learned by the NLP‐based machine learning model without a time‐consuming human expert training process. The NLP model highlights a hole‐transporting material that receives insufficient attention in the literature, which is then elaborated via density functional theory calculations to provide an atomistic view of the perovskite/hole‐transporting layer heterostructures and their optoelectronic properties. Finally, the above results are confirmed by device experiments. The present study demonstrates the viability of NLP as a universal machine learning tool to extract useful information from existing publications.

Jinping Zhao, Ali Arefi, Alberto Borghetti et al.

There is a general concern that the increasing penetration of electric vehicles (EVs) will result in higher aging failure probability of equipment and reduced network reliability. The electricity costs may also increase, due to the exacerbation of peak load led by uncontrolled EV charging. This paper proposes a linear optimization model for the assessment of the benefits of EV smart charging on both network reliability improvement and electricity cost reduction. The objective of the proposed model is the cost minimization, including the loss of load, repair costs due to aging failures, and EV charging expenses. The proposed model incorporates a piecewise linear model representation for the failure probability distributions and utilizes a machine learning approach to represent the EV charging load. Considering two different test systems (a 5-bus network and the IEEE 33-bus network), this paper compares aging failure probabilities, service unavailability, expected energy not supplied, and total costs in various scenarios with and without the implementation of EV smart charging.

Jheison Duvier Diaz-Ortega, Octavio Gutiérrez-Frías, José Alejandro Aguirre-Anaya et al.

In the present work, based on an approximate modelling of a rover-type robot and a proportional control law, a simplified trajectory tracking strategy for a passive suspension rover-type mobile robot was developed. This strategy achieves trajectory tracking and the autonomous displacement of a rover, of which its configuration involves complex kinematics and dynamics. All these lineaments reduce the complexity of the analysis, the number of electronic components to implement, the computational requirements and the energy consumption. The robotic system used is based on the <i>Shrimp</i> rover, which is a robot with a passive suspension that is capable of carrying out displacements over rough terrain. The tests were performed using numerical simulations with different desired trajectories, and also using experimental tests using a passive suspension rover-type mobile robot.

Mahdi Dolatabadi, Seyedreza Seyednouri, Albin Hasselström et al.

Abstract This study aims to develop an optimization strategy for determining the optimal type and capacity of batteries in a building‐applied photovoltaic system, taking into account battery degradation, consumption profiles, and regional solar irradiation. Key performance indicators such as peak shaving, savings, net present value, self‐consumption, return on investment, and payback period are examined. The best trade‐off among these indicators is determined using the fuzzy decision‐making method. A study was conducted using real data from Kpenergy Company, focusing on a building with a 50 kW photovoltaic system located in Stockholm. Three cases were examined in MATLAB software, each categorized based on the type of contract between the utility (Vattenfall Company) and the subscriber. The results of these case studies highlight the effectiveness of the proposed optimization approach. Using the proposed approach, optimal batteries are determined, minimizing subscriber costs while maximizing profit.

Yang Liu, Fangqi Chen, Xiaojie Liu et al.

To reduce the heat island effect brought by conventional asphalt roofing products with high solar absorption, we propose a category of self-cleaning and self-cooling composited roofing tile (CRT) made of old corrugated containers (OCC) and tung oil inspired by traditional Chinese oil-paper umbrellas, which can be fabricated at scale and easily recycled for roofing applications. Compared with asphalt shingles, CRTs can improve the solar reflection due to the randomized structure of the cellulose microfibers, contributing to a significant temperature difference of ∼13.2 °C. In addition, they have a high thermal emissivity of 0.93 in the atmospheric window, radiating great amounts of heat into the cold outer space (∼ 3 K). The top layer tung oil film smeared on the OCC pulp fibers transforms the roofing tile from a waterabsorbing to a waterproofing state and significantly enhances the mechanical strength, contributing to a stable thermal performance in outdoor applications. Furthermore, dyed CRTs can selectively reflect visible light for desired colors and effectively reflect near-infrared light to reduce solar heating, which synchronously achieves roof cooling and aesthetic variety. These cheap, eco-friendly, and multifunctional roofing tiles can provide a value-added path for OCC recycling, which may inspire more radiative cooling composites purely from recycling waste towards an energy-saving and sustainable society.

K. Shaler, A. N. Robertson, J. Jonkman

<p>Wind turbines are designed using a set of simulations to determine the fatigue and ultimate loads, which are typically focused solely on unwaked wind turbine operation. These structural loads can be significantly influenced by the wind inflow conditions. Turbines experience altered inflow conditions when placed in the wake of upstream turbines, which can additionally influence the fatigue and ultimate loads. It is important to understand the impact of uncertainty on the resulting loads of both unwaked and waked turbines. The goal of this work is to assess which wind-inflow-related and wake-related parameters have the greatest influence on fatigue and ultimate loads during normal operation for turbines in a three-turbine wind farm. Twenty-eight wind inflow and wake parameters are screened using an elementary effects sensitivity analysis approach to identify the parameters that lead to the largest variation in the fatigue and ultimate loads of each turbine. This study uses the National Renewable Energy Laboratory (NREL) 5 MW baseline wind turbine, simulated with OpenFAST and synthetically generated inflow based on the International Electrotechnical Commission (IEC) Kaimal turbulence spectrum with the IEC exponential coherence model using the NREL tool TurbSim. The focus is on sensitivity to individual parameters, though interactions between parameters are considered, and how sensitivity differs between waked and unwaked turbines. The results of this work show that for both waked and unwaked turbines, ambient turbulence in the primary wind direction and shear are the most sensitive parameters for turbine fatigue and ultimate loads. Secondary parameters of importance for all turbines are identified as yaw misalignment, streamwise integral length, and the exponent and streamwise components of the IEC coherence model. The tertiary parameters of importance differ between waked and unwaked turbines. Tertiary effects account for up to <span class="inline-formula">9.0 <i>%</i></span> of the significant events for waked turbine ultimate loads and include veer, non-streamwise components of the IEC coherence model, Reynolds stresses, wind direction, air density, and several wake calibration parameters. For fatigue loads, tertiary effects account for up to <span class="inline-formula">5.4 <i>%</i></span> of the significant events and include vertical turbulence standard deviation, lateral and vertical wind integral lengths, non-streamwise components of the IEC coherence model, Reynolds stresses, wind direction, and all wake calibration parameters. This information shows the increased importance of non-streamwise wind components and wake parameters in the fatigue and ultimate load sensitivity of downstream turbines.</p>

Takeshi Yoshida, Yuki Onishi, Takuya Kawahara et al.

Abstract In this study, we propose a method to automate fruit harvesting with a fruit harvesting robot equipped with robotic arms. Given the future growth of the world population, food shortages are expected to accelerate. Since much of Japan’s agriculture is dependent on imports, it is expected to be greatly affected by this upcoming food shortage. In recent years, the number of agricultural workers in Japan has been decreasing and the population is aging. As a result, there is a need to automate and reduce labor in agricultural work using agricultural machinery. In particular, fruit cultivation requires a lot of manual labor due to the variety of orchard conditions and tree shapes, causing mechanization and automation to lag behind. In this study, a dual-armed fruit harvesting robot was designed and fabricated to reach most of the fruits on joint V-shaped trellis that was cultivated and adjusted for the robot. To harvest the fruit, the fruit harvesting robot uses sensors and computer vision to detect and estimate the position of the fruit and then inserts end-effectors into the lower part of the fruit. During this process, there is a possibility of collision within the robot itself or with other fruits depending on the position of the fruit to be harvested. In this study, inverse kinematics and a fast path planning method using random sampling is used to harvest fruits with robot arms. This method makes it possible to control the robot arms without interfering with the fruit or the other robot arm by considering them as obstacles. Through experiments, this study showed that these methods can be used to detect pears and apples outdoors and automatically harvest them using the robot arms.

Yaxiong Li, Feng Wang, Xiangcheng Li et al.

The effect of B4C addition (0, 3 wt%, 6 wt%, 9 wt%) on the mechanical properties and oxidation resistance of Al2O3-C refractory ceramics was studies in the paper. The results indicated that the addition of B4C could reduce the apparent porosity, increase the mechanical strengths and improve the oxidation resistance. After fired at 1100 °C, the specimen with 6 wt% B4C achieved lowest porosity and permanent linear change. The cold crushing strength was improved from 14.65 MPa to 47.18 MPa. The cold modulus of rupture was significantly improved from 12.1 MPa to 36.29 MPa. When the fired temperature rose to 1450 °C, the lowest porosity and permanent linear change were obtained when B4C additive was 3 wt%. CCS was significantly improved from 12.40 MPa to 57.32 MPa. CMOR was also increased from 7.16 MPa to 28.71 MPa correspondingly. Meanwhile, the oxidation index could be also reduced from 47.6% to 3.9% when B4C content was 6 wt%. These improved properties were due to the formation of liquid phase B2O3 by the reaction between B4C and O2/CO. The compact structure was constructed by volumetric expansion of B2O3.

Jiaxin Chen, Pingan Chen, Xiangchen Li et al.

In this paper, the effect of B4C content and heat treatment temperature on microstructure, mechanical properties and oxide resistance of SiC refractory ceramics were investigated. The results show that the inclusion of B4C could improve the crystallinity of gengerated SiC and graphitization. When the B4C content was 6%, the linear change of SiC-based refractory ceramics after heat treatment at 1450°C decreased from 1.39% to 0.58%. At the same time, the cold modulus of rupture and cold compressive strength increased by 1.8 times and 2 times, respectively. Meanwhile, with the increase of B4C content, the oxidation index of the SiC-based refractory ceramics decreased from 30.33% to 16.63% after oxidation at 1400°C.

David Sanchez-Londono, Sofia Posada-Ceron, Giacomo Barbieri et al.

In engineering education, it is universally recognized that the development of higher-order thinking skills must be encouraged. On the one hand, the backwards design approach allows for the design of courses or activities focused on learning goals rather than on specific content, establishing basic tools to foster these skills. On the other hand, Bloom’s taxonomy allows for the separation of macro learning goals into specific learning objectives and adequate evidence. This work integrates the two approaches for the development of an active learning activity for a design of machinery course. The activity consists of introducing students to the design of mechanisms, is developed following the backwards design process and Bloom’s taxonomy of learning objectives, and focuses on both technical skills and critical thinking. After designing and testing the activity, the authors found that it allows the acquisition of technical skills in kinematics and kinetics of mechanisms and provides insights for the development of the main components of critical thinking within the machinery design process.

Ruirui Fang, Nana Deng, Hongbin Zhang et al.

In this paper, selective laser melting (SLM) was used to manufacture corrax stainless steel samples under different parameters. It was found that the SLMed samples were mainly composed by lots of fine martensite (including cellular structure, cellular dendritic grains and blocky grains), and trace austenite. During SLM forming process, a large number of low-angle grain boundaries (LAGBs) and high-density dislocations were formed in the matrix. Meanwhile, the samples showed weak texture and no obvious preference orientation. Moreover, the relative density of all SLMed samples reached above 90%, and the relative density was above 97% when the laser energy density was 54.13–78.19 J·mm−3. Under the optimal process parameters of P = 190 W, V = 1.1 m·s−1, the relative density of sample reached above 99.52 ± 0.09%, while the sample exhibited the best mechanical properties, including the highest microhardness (374.2 ± 6.5HV), yield strength (YS = 946 ± 7.3 MPa), ultimate tensile strength (UTS = 1084 ± 3 MPa) and elongation (EL = 17.64 ± 0.18%). Moreover, the strengthening mechanisms of SLMed samples mainly included grain boundary strengthening, dislocation strengthening and precipitation strengthening, while dislocation strengthening played a dominant role. Besides that, the fracture mechanisms of SLMed samples belonged to ductile fracture, except for the samples prepared with laser energy density below 54.13 J·mm−3.

Takatoshi HONDO, Shoya KUNIYUKI, Takayuki TANAKA et al.

Instrumented wheelsets are widely utilized in the railway industry for the purpose of the measurement of the wheel-rail interaction force. In the conventional instrumented wheelset, the measurement accuracy of the lateral force is reduced due to the bending moment induced by the wheel load. The authors have proposed a new configuration of the instrumented wheelset to reduce the influence of the wheel load on the measurement of the lateral force. This proposed configuration utilizes the shear strains of the wheel web as a measure of the lateral force. This paper describes the accuracy verification of the proposed configuration under the wheel rotating condition. The single-wheelset roller-rig tests are carried out and the test results show that the proposed method can reduce the influence of the wheel load even under the rotating condition.

Qingwei Gao, Yumeng Zhang, Shuting Xu et al.

In modern chemical engineering processes, the involvement of solid/fluid interface is the most important component of process intensification techniques, such as confined membrane separation and catalysis. In the review, we summarized the research progress of the latest theoretical and experimental works to elucidate the contribution of interface to the fluid properties and structures at nano- and micro-scale. We mainly focused on water, alcohol aqueous solution, and ionic liquids, because they are classical systems in interfacial science and/or widely involved in the industrialization process. Surface-induced fluids were observed in all reviewed systems and played a critical role in physicochemical properties and structures of outside fluid. It can even be regarded as a new interface, when the adsorption layer has a strong interaction with the solid surface. Finally, we proposed a perspective on scientific challenges in the modern chemical engineering processes and outlined future prospects.

Cho W. S. To

محمد جعفری, محمدباقر نظری

بر پایۀ تئوری ترموالاستیسیته دوبعدی حالت پایدار میدان تنش در اطراف گشودگی های مختلف در یک صفحۀ نامحدود همسان‌گرد مورد بررسی قرار می گیرد. صفحه در بی نهایت تحت جریان حرارتی یکنواخت است و مرز گشودگی مرکزی عایق است. بااستفاده از توابع پتانسیل مختلط و به کارگیری نگاشت همنوا و حلّ معادلات انتگرالی، تأثیر انحنای گوشۀ گشودگی بر توزیع تنش اطراف گشودگی مطالعه می شود. روش حل بر پایۀ بسط روش گودیر و فلورنس است. آنها از روش متغیّر مختلط برای تحلیل تنش ورق نامحدود همسان گوشۀ گرد حاوی گشودگی دایره ای و بیضی شکل استفاده کردند. برای سادگی استفاده از انتگرال کوشی ورق نامحدود شامل گشودگی غیردایروی به ناحیة درون دایره ای به شعاع واحد نگاشته می شود. نتایج حاصل نشان می دهند که انحنای گوشۀ گشودگی تأثیر بسزایی بر توزیع تنش دارد.

Abdoullah Namdar, Ershad Darvishi, Xiong Feng et al.

The flexural failure of plain concrete beam occurs along with development of flexural crack on beam. In this paper by using ABAQUS, mechanism failure of plain concrete beam under three steps have been simulated. The cracking moment has been analytically calculated and applied on the both sides of the fixed beam, and flexural crack has been simulated on beam. Displacement, von Mises, load reaction, displacementcrack length, von Mises-crack length and von Mises-displacement of beams have been graphical depicted. Results indicated that, the flexural crack governs beam mechanism failure and its effects on beam resistance failure. It has been found that the flexural crack in initial stage it developed slowly and changes to be fast at the final stage of collapsing beam due to reduction of the flexural resistance of beam. Increasing mechanical properties of concrete, collapse displacement is reduced.

S. Eiamsa-ard, M. Pimsarn, C. Thianpong

The thermohydraulic performance in a tube containing a modified twisted tape with alternate-axes and wing arrangements is reported. This work aims to investigate the effects of wing arrangements (opposite (O) and parallel (P) wings) at different wing shapes (triangle (Tri), rectangular (Rec), and trapezoidal (Tra) wings) and on the thermohydraulic performance characteristics. The obtained results show that wing twisted tapes with all wing shape arrangements (O-Tri/O-Rec/O-Tra/P-Tri/P-Rec/P-Tra) give superior thermohydraulic performance and heat transfer rate to the typical twisted tape. In addition, the tapes with opposite wing arrangement of O-Tra, O-Rec, and O-Tri give superior thermohydraulic performances to those with parallel wing arrangement of P-Tra, P-Rec, and P-Tri around 2.7%, 3.5%, and 3.2%, respectively.

Long-Chang Hsieh, Tzu-Hsia Chen, Po-Cheng Lai

Typically, the motion of the output link of the mode clamping mechanism has reciprocating linear motion, but the motion of the input link can be reciprocating rocking motion or reciprocating linear motion. In addition, the mold clamping mechanism must have a dead-position configuration for the mold at the closed position. This article focuses on the kinematic design of a mold clamping mechanism having an input link with reciprocating linear motion and having dead-position configuration at closed positions. First, four design concepts of mold clamping mechanisms are proposed based on the mechanism creative design methodology. Then, one of the design concepts is chosen as the design example to illustrate the kinematic design of the mode clamping mechanism with minimal maximum acceleration. According to the design requirements, the best design of the mode clamping mechanism of this article is better than the existing patent by reducing 43.5% acceleration and 18.6% driving force.