Surface integrity parameters such as surface topography, hardness gradient, and residual stress have significant impacts on contact fatigue of tooth surface. To meet the needs of efficient and stable contact fatigue calculations, efficient mixed lubrication calculations were achieved in this study by dividing the lubrication region and reconstructing the asperities. By considering the influence of the residual stress and hardness gradient on the tooth surface, a calculation model for gear contact fatigue was established and verified based on fatigue tests of gear contact. The results are as follows: (1) Due to the influence of rough surfaces, there were two high-stress peaks in the near-surface layer (6 μm) and sub-surface layer (245 μm) of the tooth surface, which corresponded to micro-pitting and pitting areas, respectively. (2) Ignoring the influence of various integrity parameters led to errors of several orders of magnitude in predicting the contact fatigue life of the tooth surface. (3) The fatigue failure area predicted by the model proposed in this paper was consistent with the experimental results, and the average error in the fatigue life was approximately 14.3%. The method proposed in this paper can effectively predict the contact fatigue life and dangerous areas of the tooth surface, with advantages of high computational efficiency and good stability, laying a foundation for research on tooth surface anti-fatigue design.
Shogo NAKAMURA, Kenichi NAKANISHI, Kenji OHARA
et al.
Low-frequency vibration cutting (VC) is a machining technology wherein a tool periodically vibrates to break cutting chips. However, VC produces tool paths that include air cuts to break up chips, which deteriorates surface roughness and roundness. This study aims to address these limitations. Low-frequency vibrations are applied to both the upper and lower turrets of a multitasking lathe. To improve surface roughness with simultaneous VC, this study presents a theoretical method to calculate the optimal values for frequency and amplitude of VC and the starting positions of the Z-axis of two upper and lower turrets. Simulations and actual machining experiments were conducted after adjusting VC frequency and amplitude and the starting positions of Z-axis of both turrets. Results show that the surface roughness improves with two-turret simultaneous VC compared to one-turret single VC in stainless steel and brass machining experiments, while succeeding in breaking up cutting chips. Furthermore, the surface roughness of simultaneous VC is improved to a level close to that of single and simultaneous conventional cutting (CC) results in stainless steel. Although there is some variation in material, the roundness of simultaneous VC is generally improved compared to single VC and CC. For the machining of brass, the roundness results of the simultaneous VC were better than those of single CC, VC, and simultaneous CC.
Engineering machinery, tools, and implements, Mechanical engineering and machinery
Elham Nejadmoghadam, Abdenour Achour, Olov Öhrman
et al.
Understanding and mitigating catalyst deactivation is crucial for enhancing the efficiency of hydrodeoxygenation (HDO) processes in the production of biofuels. In this study sulfided metal catalysts, NiMo/Al2O3, NiMo/SiO2-Al2O3, and NiW/Al2O3 along with bare supports (Al2O3, SiO2-Al2O3, and zeolite Y) were placed in a refinery green hydrotreating unit. Potassium, phosphorus and sodium were identified as major poisons. The HDO activity of spent catalysts was assessed in a lab-scale batch reactor at 58 bar H2 and 325 °C for deoxygenation of oleic acid. The results highlighted that the active metals, particularly NiW, had a more pronounced tendency to attract poisons compared to the supports. However, with bare supports, coking was more significant and simultaneously less poisons were trapped, which could be due to blocking of the pores with coke. In the presence of these poisons there was a significant decline in oxygenate conversion compared with fresh catalysts, with a gradual reduction in activity for both decarbonation and direct-HDO products. Solvent washing treatments with DMSO and water were employed in an attempt to recover the activity of the spent catalysts, by partially removing the poisons. However, through these treatments, the activity of the NiMo/Al2O3 catalyst could not be restored.
Data-driven intelligent fault diagnosis methods have been extensively researched and applied in rotating machinery. In practical application scenarios, factors such as variable operating conditions and scarcity of labeled samples in rotating machinery hinder the engineering application and promotion of diagnostic models. To address these challenges, this paper proposes an unsupervised domain adaptation network called the Multi-scale Hybrid Domain Adaptation with Attention (MHDAA). Firstly, a multi-scale convolutional module was developed to extract fault features at different scales. Secondly, a multi-channel attention mechanism was proposed to enable the convolution layers of different convolution kernels fully extract feature information. Finally, a hybrid domain adaptation was constructed to dynamically extract invariant features from both the source and target domains. The method was evaluated in multiple transfer scenarios of planetary gearboxes and bearings. Experimental results demonstrate that the proposed method can effectively utilize fault features with high correlation from multiple source domains to complete fault diagnosis with unknown data labels in the target domain. Moreover, the proposed method exhibits superior diagnostic performance.
AbstractThe local heat source of a civil aircraft affects the temperature of the lower panel structure of the center wing. In this paper, a local heat source is arranged on the lower panel structure of the center wing. The strain of the center wing lower panel skin under different temperature gradients under local thermal loads and the corresponding temperature gradients around the heat source were investigated. The natural mesh model and the fine finite element model were used to analyze the thermal load of the center wing lower panel. The temperature on the node was applied according to the real temperature in the test, and the analysis results were compared with the test values. After comparative analysis, the strain value of the natural mesh model has a high degree of fit with the test value, and the analysis results of the natural mesh model can be used to analyze the thermal stress intensity of the center wing lower panel.
Taking the upper sub-member of Sha 4 in Well Fanye 1 and Well Niuye 1 in Dongying Sag, Jiyang Depression, Bohai Bay Basin as a typical example, this paper adopts the method of combining macro and micro laminar characterization and complementing each other. The characteristics of laminar development are studied by means of fine description of rock thin sections by cores and electron microscopic observation Reconstruction of the Bohai Bay Basin in sand four period of ancient sedimentary environment, it is concluded that the sand on the four period of development of four complete filling sedimentary cycle. Using Milankovitch cycles method, reveals the ancient climate control mechanism of lithofacies, formed by organic laminae under hot and humid climate and a small amount of calcite laminated lithofacies, in hot and humid climate, the lithofacies is mainly composed of organic lamina and a small amount of calcite lamina, while in cold and dry climate, the lithofacies is mainly composed of calcite lamina, and the lithofacies is mainly composed of organic lamina, silty lamina and gypsum lamina. Micro-laminar research is an important scientific issue in unconventional oil and gas eology. It can provide basic data for unconventional oil and gas exploration, such as the types, distribution and extension of laminar, especially the determination of sampling targets. Different laboratory samples can be analyzed according to the laminar types.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources
The metal fabrication sector involves a variety of processes, activities, products, and by-products. This involves various interventions such as milling, turning, welding, drilling, and grinding. Firms in this sector use one or a combination of these interventions where machinery is used, which can expose workers to machinery hazards if proper safety procedures are not observed. Occupational Safety and Health (OSH) is vital in Technical Vocational Education and Training (TVET) institutions, especially in mechanical engineering programmes where metal fabrication is practised. The objective of this study was to assess the awareness of occupational machinery hazards in mechanical engineering workshops in TVET Institutions. The study adopted a descriptive research design and employed a structured questionnaire for data collection. Purposive sampling was used to identify institutions participating in the study. SPSS version 25 was used to analyse the data and present it in tables and graphs. Noise (90.4%) and vibration (71.9%) were reported as the most common occupational hazards, respectively, in mechanical engineering workshops. Regarding workstations, the grinding section (39.4%) and milling section (15.8%) were reported as experiencing high levels of noise. The study recommends that adequate control measures be put in place to mitigate against these hazards.
In the current studies an investigations were made to know the effect of 63 micron sized B4C particles addition on the mechanical and wear behavior of aerospace alloy Al2618 metal composites. Al2618 alloy with different weight percentages (2, 4, 6 and 8 wt. %) of 63 micron sized B4C particles reinforced composites were produced by stir cast process. These synthesized composites were tested for various mechanical properties like hardness, compression strength and tensile behavior along with density measurements. Further, microstructural characterization was carried by SEM/EDS and XRD analysis to know the micron sized particles distribution and phases. Wear behavior of Al2618 alloy with 2 to 8 wt. % of B4C composites were studied as per ASTM G99 standards with varying loads and sliding speeds. By adding 63 micron sized B4C particles hardness, compression and tensile strength of Al2618 alloy was enriched with slight decrease in elongation. Further, wear resistance of Al2618 alloy was enriched with the accumulation of B4C particles. As load and speed on the specimen increased, there was increase in wear of Al2618 alloy and its composites. Various tensile fracture surface morphology and worn surface behavior was observed by SEM analysis.
Mechanical engineering and machinery, Structural engineering (General)
Micro perforation plate (MPP) sound liner is a very effective method to control pipe noise in high-speed airflow environment based on the principle of Helmholtz resonator. It generally has single layer, double-layer or even multi-layer structure. At present, the acoustic design theory of MPP sound liner is mature and reliable in the absence of air flow, but the design process is complicated in the presence of air flow, especially in the environment of high-speed air flow, and there are many influencing factors, so it has not formed a mature and unified theoretical basis for design. In this paper, an acoustic impedance model of double-layer MPP sound liner with two resonant frequencies is derived which is based on the acoustic impedance model of single layer MPP sound liner by the transfer matrix method (TMM). The model is used to calculate acoustic impedance and acoustic absorption of a known double-layer MPP sound liner at 130 dB sound intensity level and 60 m/s velocity. At the same time, the flow tube method is used for measurement. The results show that the theoretical results are close to the measured results. The maximum error of sound absorption coefficient is only 0.05, which can meet the requirements of engineering application.
Control engineering systems. Automatic machinery (General), Technology
Abstract This paper develops a novel observer‐based robust tracking predictive controller for discrete‐time nonlinear affine systems capable of dealing with changing setpoints and non‐additive non‐slowly varying unknown disturbance with bounded variations. The existence of disturbance and/or sudden changes in a setpoint may lead to feasibility and stability issues in the stabilizing terminal constraint‐based MPC. Since robust tracking MPCs usually consider additive disturbance, the recursive feasibility of these methods may be lost in the presence of non‐additive non‐slowly varying disturbance. The robust tracking MPC presented here extends the artificial reference‐based MPC to deal with both changing setpoints and non‐additive non‐slowly varying disturbance. The key idea is the addition of tightened input and state constraints as new system constraints. The authors also guarantee the boundedness of disturbance observation error and closed‐loop tracking error. In this method, the optimal tracking error converges asymptotically to the terminal region, and the perturbed system tracking error remains in a variable size tube around the optimal tracking error. It is shown that the proposed controller can achieve offset‐free tracking in the presence of constant disturbance. The simulation results of the satellite attitude control system are provided to demonstrate the efficiency of the proposed predictive controller.
Control engineering systems. Automatic machinery (General)
This work aims to provide a fundamental understanding on the dispersive behaviors of shear horizontal (SH) surface waves propagating in a layered piezoelectric nanostructure consisting of an elastic substrate and a piezoelectric nanofilm by considering the surface effects. Theoretical derivation based on the surface piezoelectricity model was conducted for this purpose, and analytic expressions of the dispersion equation under the nonclassical mechanical and electrical boundary conditions were obtained. Numerical solutions were given to investigate the influencing mechanism of surface elasticity, surface piezoelectricity, surface dielectricity, as well as the surface density upon the propagation characteristics of SH surface waves, respectively. The results also reveal the size-dependence of dispersive behaviors, which indicates that the surface effects make a difference only when the thickness of the piezoelectric nanofilm stays in a certain range.
Ching-Lin Fan, Chun-Yuan Chen, Shih-Yang Liu
et al.
This paper proposes a new 6T1C pixel circuit based on low-temperature polycrystalline oxide (LTPO) technology for portable active-matrix organic light-emitting diode (AMOLED) displays with variable refresh rates ranging from 1 to 120 Hz. The proposed circuit has a simple structure and is based on the design of sharing lines of switch-controlling signals. It also provides low-voltage driving and immunity to OLED degeneration issues. The calculation and analysis of programming time are discussed, and the optimal storage capacitor for the proposed circuit’s high-speed driving is selected. The results of the simulation reveal that threshold voltage variations in driving thin-film transistors of ±0.33 V can be well sensed and compensated with a 1.8% average shift of OLED currents in high-frame-rate operation (120 Hz), while the maximum variation in OLED currents within all gray levels is only 3.56 nA in low-frame-rate operation (1 Hz). As a result, the proposed 6T1C pixel circuit is a good candidate for use in portable AMOLED displays.
To modify the rapid carburization and heat treatments of 18Cr2Ni4WA heavy-duty gears on coal-cutting machines, numerical modeling and experimental investigations are carried out for understanding the evolution of microstructure and properties. Through numerical modeling, the fractions of austenite, bainite, and martensite are evaluated. The Vickers hardness distribution across the hardening layer, calculated by the Maynier equation, compares well with the experimental measurement. The microstructure of the hardening layer is mainly composed of fine martensite and carbides, while that of the interior area is the martensite. The gradient of the microstructure from the hardening layer to the interior area leads to the variation of the hardness distribution. The experimental results show that the high-temperature tempering and quenching are beneficial for the refinements of the grains in the hardening layer and the interior area. The present study indicates that the combination of numerical modeling and experimental observation provides a powerful tool for the modification and improvement of the carburization and heat treatment processes.
Because of the rapid development key industries like aerospace, energy, rail transportation, engineering machinery and other industries there exist a growing demand for high speed and precise manufacturing of large and heavy parts. CNC Machine Tools with kinematical feed chains with great distance between slides, Gantry type, are the main tool to machine large and heavy parts. In such type of machines, the mobile element (the mechanical coupling between the two kinematical feed chains) has a significant effect upon the static and dynamic characteristics of the machine. Deformation of the mobile element has a significant impact upon machining accuracy. A study of the static proprieties and the deformation that effect the mobile element is extremely useful for improving the machining accuracy and efficiency of the machine. The weight of the mobile element it is extremely important and effects the overall dimension and weight of the machine. Using FEA analysis on a 3D CAD model this papers objectives are mesh optimization and topological optimization of the mobile element. This study will show that the topological optimization preformed on the mobile element has reduce the inertial forces, 10 to 30 %, while maintaining rigidity.
Cells and tissues are constantly exposed to mechanical stress. In order to respond to alterations in mechanical stimuli, specific cellular machinery must be in place to rapidly convert physical force into chemical signaling to achieve the desired physiological responses. Mechanosensitive ion channels respond to such physical stimuli in the order of microseconds and are therefore essential components to mechanotransduction. Our understanding of how these ion channels contribute to cellular and physiological responses to mechanical force has vastly expanded in the last few decades due to engineering ingenuities accompanying patch clamp electrophysiology, as well as sophisticated molecular and genetic approaches. Such investigations have unveiled major implications for mechanosensitive ion channels in cardiovascular health and disease. Therefore, in this chapter I focus on our present understanding of how biophysical activation of various mechanosensitive ion channels promotes distinct cell signaling events with tissue-specific physiological responses in the cardiovascular system. Specifically, I discuss the roles of mechanosensitive ion channels in mediating (i) endothelial and smooth muscle cell control of vascular tone, (ii) mechano-electric feedback and cell signaling pathways in cardiomyocytes and cardiac fibroblasts, and (iii) the baroreflex.
The health of a rotating electric machine can be evaluated by monitoring electrical and mechanical parameters. As more information is available, it easier can become the diagnosis of the machine operational condition. We built a laboratory test bench to study rotor unbalance issues according to ISO standards. Using the electric stator current harmonic analysis, this paper presents a comparison study among Support-Vector Machines, Decision Tree classifies, and One-vs-One strategy to identify rotor unbalance kind and severity problem – a nonlinear multiclass task. Moreover, we propose a methodology to update the classifier for dealing better with changes produced by environmental variations and natural machinery usage. The adaptative update means to update the training data set with an amount of recent data, saving the entire original historical data. It is relevant for engineering maintenance. Our results show that the current signature analysis is appropriate to identify the type and severity of the rotor unbalance problem. Moreover, we show that machine learning techniques can be effective for an industrial application.
One of the production problems that arise at the Gathering Station is an unstable production problem, this is caused by controlling the level of fluid in the wash tank that is less than the maximum for that need to be improved by changing the system from manual to automatic. To maintain the stability of production at the gathering station, special measures such as controlling fluid levels in the storage tanks need to be carried out, monitoring pressure, temperature monitoring and so on that can have a positive effect on oil production at the gathering station.
Wash Tank is a tank that is useful for temporary storage of liquid fluid (liquid) that comes from the boot gas. The liquid fluid entering the wash tank consists of a mixture of crude oil and water. At the Wash tank the process of separation between crude oil and water. This washing tank is the largest tank compared to other processing tanks at the gathering station, its diameter is around 85 ft to 90 ft, and its height is around 35 ft to 40 ft. The normal level in the separation process is 36 ft, where the level 1 ft - 29 ft is the water level, while the level 29 ft - 36 ft is the oil level. The 1ft - 29 ft level is referred to as the interface level, where the water level is expected to be at level 29 and the thickness of the oil / oil stock tank 7 ft in the wash tank.
Research conducted on the problem of controlling the level of fluid in the wash tank, where manual control is ineffective and inefficient, for this reason it is necessary to change from a manual to automatic process with the ROC (Remote Operation Control) system, the changes made are expected to maintain the interface and the oil stock tank in accordance with the set point that has been determined and where the amount of oil production per day at the gathering station is very influential on the oil stock tank so that the oil pumped to the shipping line has a BS&W below 1% and has a temperature of 130 ° F -150 ° F In order to obtain this value, we must maintain the interface and the oil stock tank in accordance with the specified set point and where the amount of oil production per day at the gathering station is very influential on the oil stock tank