scholarly journals Interfacial microstructures and properties of hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si bimetallic material fabricated by liquid–liquid casting route

2020 ◽  
Vol 11 (2) ◽  
pp. 371-379
Author(s):  
Mohamed Ramadan ◽  
Abdulaziz S. Alghamdi
Keyword(s):  
Control Method ◽  
Casting Process ◽  
Imperfect Interface ◽  
Shrinkage Cavity ◽  
Time Interval ◽  
Material Microstructure ◽  
Casting Technique ◽  
Time Control ◽  
Interface Bond ◽  
Mould Casting

Abstract. The bimetal casting process using the liquid–liquid technique was developed to produce a high-quality hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si alloy bimetal material. Microstructure and microhardness were investigated as a function of the time interval between pouring hypo-eutectic and hyper-eutectic alloys. A bimetal material was successfully fabricated using a liquid–liquid casting technique with a 10 s time interval in a permanent mould casting. A unique structure comprised of hyper-eutectic Al–21Si, hypo-eutectic Al–7.5Si and a eutectic interface of 70 µm thickness was obtained. This structure totally differs from that obtained using a higher time interval above 10 s that showed an imperfect interface bond due to the shrinkage cavity and formation of oxides. The hardness variation from the upper zone of 117.5 HV to the lower zone of 76 HV corresponded to the variation in Si and the content of other alloying elements. The proposed total solidification time control method is a promising approach for the successful fabrication of liquid–liquid bimetal material.

Optimized Non-Dead-Time Control of Inverter with Two-Phase Modulated SVPWM

2012 ◽  
Vol 562-564 ◽  
pp. 1531-1536
Author(s):  
Ming Xing Zhu ◽  
Jing Bo Shi
Keyword(s):  
Control Strategy ◽  
Pulse Width Modulation ◽  
Dead Time ◽  
Control Method ◽  
Short Circuit ◽  
Two Phase ◽  
Zero Crossing ◽  
Time Control ◽  
Bus Voltage ◽  
Current Zero

In the inverter control system, two-phase modulated space vector pulse width modulation (SVPWM) algorithm has the advantages of minimum switch loss and higher utilization of direct current (DC) bus voltage. Non-dead-time control strategy can eliminate the problems of the dead time effects. But the traditional non-dead-time control strategy heavily depends on the current zero-crossing detection, which may cause the output voltage distortion or even a short circuit. Based on the analysis of the reason for the distortion, a new optimized non-dead-time control method is proposed. Two methods for the detection of the overlapping area are enumerated. The conclusions are confirmed by the simulation results with MATLAB/ SIMULINK.

The “Lost Wax” Process of Precision Casting

1950 ◽  
Vol 162 (1) ◽  
pp. 66-74 ◽  
Author(s):  
J. S. Turnbull
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Casting Process ◽  
Alternative Methods ◽  
Casting Technique ◽  
Gas Turbine Blades ◽  
Precision Casting ◽  
Good Surface ◽  
Wax Pattern ◽  
Good Surface Finish

The paper describes a casting process which differs from standard foundry practice in that it uses a wax pattern in a high refractory one-piece mould to produce metal castings with a good surface finish to an accuracy of ±0·002 inch. The process involves making a master pattern in either hard wood or metal, relating it to a soft metal die by precision casting technique, and then the production of wax patterns from the die on an injection machine. Finally, the wax patterns are invested in refractory moulds, the wax is melted out, the mould baked, and the metal component is cast. The “lost wax” process is advantageous in cases where ( a) the metal is unmachinable, or ( b) where the component is of an unmachinable shape, or ( c) where production by other methods takes too long. One of the most common applications is in the manufacture of gas-turbine blades. The tool costs are relatively low compared to the costs involved in alternative methods of manufacture, the die cost being a function of the number of castings required. The production of cheap castings is necessarily dependent on the scrap percentage being kept to a minimum; at present the scrap from the manufacture of gas-turbine blades is less than 30 per cent, and the author surmises that it would not be unreasonable to expect it to be less than 10 per cent in two years' time.

Theory of Temperature Dynamic Control in Arch Dams and its Application

2012 ◽  
Vol 594-597 ◽  
pp. 738-741 ◽  
Author(s):  
Yin Duan ◽  
Xing Hong Liu ◽  
Xiao Lin Chang
Keyword(s):  
Real Time ◽  
Temperature Control ◽  
Control Method ◽  
Dynamic Control ◽  
Arch Dam ◽  
Real Time Control ◽  
New Techniques ◽  
Time Dynamic ◽  
Arch Dams ◽  
Time Control

Main factors of the temperature control and crack prevention in arch dams are summarized. The Space-time Dynamic Control method in pipe cooling process and the Temperature Real-time Control and Decision Database System are introduced to help for temperature real-time control and rapid analysis. Successful application of these new techniques in the construction of Dagangshan arch dam indicates that the proposed method are of significant effectiveness on the temperature control and crack prevention, and have good application prospect in practical project.

scholarly journals Research on Multi-Stage Composite Loading Process Control Method for Roller Staking of Self-Lubricating Spherical Plain Bearings

2021 ◽  
Vol 11 (23) ◽  
pp. 11127
Author(s):  
Qiang Wang ◽  
Jigang Chen ◽  
Haili Zhou ◽  
Xiaokang Wang ◽  
Zhanqi Hu
Keyword(s):  
Process Control ◽  
Control Method ◽  
Groove Depth ◽  
Material Damage ◽  
Technical Standards ◽  
Deformation Degree ◽  
Loading Process ◽  
Time Control ◽  
Multi Stage

The staking quality of Self-lubricating Spherical Plain Bearings (SSPBs) directly affects the safety of aircraft and the service life of bearings. Reliable loading process control methods and precise process parameter indexes will come into the creation of efficacious staking quality. Therefore, this paper aims to analyze the mechanical state of the roller staking process and give a load control method and corresponding parameter indexes for the high-quality roller staking process. First, based on the analysis of quality inspection requirements, five states of the deformation degree of the flanging lip of the V groove during the roller staking process were proposed, and their relationship with the requirements was studied. Then, the mechanical states corresponding to the five deformation states of the flanging lip deformation were obtained by numerical simulation, and the feeding displacement was determined. Meanwhile, a Multi-Stage Composite Loading (MSCL) process control method was first proposed to control the material damage of the flanging lip, i.e., the rotate speed of the roller tool was constant during the roller staking process, and the displacement–time control was adopted first; when the staking load reaches a staking value, the force–time control was used to make the staking quality meet the requirements. Finally, the staking quality of the MSCL method was verified though the test. The research shows that the feeding displacement needs to be added to the requirements, and the recommended value is 0.5–0.6 times of the V groove depth. A good surface quality and non-material-damage of the flanging lip is more likely to be obtained by the MSCL process control method. The research reveals the formation mechanism of process deformation, and gives more precise process control indexes. At the same time, it provides a theoretical reference for more reliable technical standards.

Study on the Causes and Prevention Measures of Shrinkage Defects of Heavy V-Belt Pulley in the Production

2014 ◽  
Vol 722 ◽  
pp. 231-234
Author(s):  
Gui Qin Jin ◽  
Tao Yan ◽  
Cui Feng Chen
Keyword(s):  
Chemical Composition ◽  
Hot Spot ◽  
Casting Process ◽  
Shrinkage Porosity ◽  
Shrinkage Cavity ◽  
Optimized Design ◽  
Prevention Measures ◽  
Pouring Temperature ◽  
Performance Requirements ◽  
Shrinkage Defects

Shrinkage cavity and shrinkage porosity, often occurring during the production of heavy v-belt pulley roughcast, may lead to the decrease of the pulley performance and further result in casting rejection. Therefore, it is necessary to study the causes and prevention measures of shrinkage defects of the casting. The material of V-belt pulley roughcast at issue is HT250 and it adopts resin sand casting process. With a large amount of practice in workshop and times of revision of the design of foundry technology, we have found that the shrinkage in the hot spot of heavy v-belt pulley roughcast can be reduced or even eliminated to fully meet the performance requirements with a moderate control of pouring temperature and speed, an optimized design of foundry technology, and a strict limitation of chemical composition. This finding will bring illumination to the production process of other heavy pulley roughcast.

Study on Local Extrusions' Effects on Improvement of Die Casting Prismatic Parts' Forming Quality

2013 ◽  
Vol 312 ◽  
pp. 475-479
Author(s):  
Wei Gang Zheng ◽  
Cun Hong Yin ◽  
Yu Hong Yuan ◽  
Zhen Min Pan ◽  
Chao Tang
Keyword(s):  
Mechanical Properties ◽  
Die Casting ◽  
Casting Process ◽  
Extrusion Process ◽  
Shrinkage Porosity ◽  
Shrinkage Cavity ◽  
Prismatic Parts ◽  
Porosity Defects ◽  
Die Casting Process ◽  
Casting Production

This paper analyzes traditional die casting process to find out the reasons that cause shrinkage cavity and porosity defects in casting. An optimized process of die casting by using local extrusion is proposed. A device used in local extrusion which realizes forcing compensating contraction on key parts of crankcase is designed and the parameters of local extrusion process are discussed. Compared the mechanical properties and microstructure of local extrusion used in die casting production with traditional. It shows that local extrusion used in die casting production can not only achieve the aim eliminating shrinkage porosity and cavity of a casting but also can refine grain to improve the mechanical properties.

Immersion and invariance adaptive finite-time control of air-breathing hypersonic vehicles

2018 ◽  
Vol 233 (7) ◽  
pp. 2626-2641 ◽  
Author(s):  
Chao Han ◽  
Zhen Liu ◽  
Jianqiang Yi
Keyword(s):  
Control System ◽  
Finite Time ◽  
Control Method ◽  
Sliding Mode ◽  
Second Order ◽  
Hypersonic Vehicles ◽  
Terminal Sliding Mode ◽  
Air Breathing ◽  
Immersion And Invariance ◽  
Time Control

In this paper, a novel adaptive finite-time control of air-breathing hypersonic vehicles is proposed. Based on the immersion and invariance theory, an adaptive finite-time control method for general second-order systems is first derived, using nonsingular terminal sliding mode scheme. Then the method is applied to the control system design of a flexible air-breathing vehicle model, whose dynamics can be decoupled into first-order and second-order subsystems by time-scale separation principle. The main features of this hypersonic vehicle control system lie in the design flexibility of the parameter adaptive laws and the rapid convergence to the equilibrium point. Finally, simulations are conducted, which demonstrate that the control system has the features of fast and accurate tracking to command trajectories and strong robustness to parametric and non-parametric uncertainties.

A New Finite Time Control Solution for Robotic Manipulators Based on Nonsingular Fast Terminal Sliding Variables and the Adaptive Super-Twisting Scheme

2019 ◽  
Vol 14 (3) ◽  
Author(s):  
Vo Anh Tuan ◽  
Hee-Jun Kang
Keyword(s):  
Finite Time ◽  
Control Method ◽  
Sliding Mode ◽  
Robotic Manipulators ◽  
Control Law ◽  
Continuous Control ◽  
Terminal Sliding Mode ◽  
Finite Time Convergence ◽  
Position Errors ◽  
Time Control

In this study, a new finite time control method is suggested for robotic manipulators based on nonsingular fast terminal sliding variables and the adaptive super-twisting method. First, to avoid the singularity drawback and achieve the finite time convergence of positional errors with a fast transient response rate, nonsingular fast terminal sliding variables are constructed in the position errors' state space. Next, adaptive tuning laws based on the super-twisting scheme are presented for the switching control law of terminal sliding mode control (TSMC) so that a continuous control law is extended to reject the effects of chattering behavior. Finally, a new finite time control method ensures that sliding motion will take place, regardless of the effects of the perturbations and uncertainties on the robot system. Accordingly, the stabilization and robustness of the suggested control system can be guaranteed with high-precision performance. The robustness issue and the finite time convergence of the suggested system are totally confirmed by the Lyapunov stability principle. In simulation studies, the experimental results exhibit the effectiveness and viability of our proposed scheme for joint position tracking control of a 3DOF PUMA560 robot.

Assessment of Aedes aegypti (Diptera: Culicidae) Males Flight Ability for SIT Application: Effect of Device Design, Duration of Test, and Male Age

2019 ◽  
Vol 57 (3) ◽  
pp. 824-829 ◽  
Author(s):  
Ariane Dor ◽  
Ana María Maggiani-Aguilera ◽  
Javier Valle-Mora ◽  
J Guillermo Bond ◽  
Carlos F Marina ◽  
...  
Keyword(s):  
Quality Control ◽  
Aedes Aegypti ◽  
Control Method ◽  
Flight Test ◽  
Test Time ◽  
Time Interval ◽  
Flight Ability ◽  
Young Males ◽  
Male Age ◽  
Standard Quality

Abstract The Sterile Insect Technique (SIT) is a pest control method where large numbers of sterile males are released to induce sterility in wild populations. Since a successful SIT application depends on the released sterile males being competitive with wild males, standard quality control tests are a necessary component of any SIT program. Flight ability (ability to fly out from a device) is a reliable indicator of insect quality. Based on previous studies, we developed four new tubular devices constructed with locally available materials to explore their potential as flight test devices for Aedes aegypti (L.) mass-reared males. Males were allowed to fly upwards through a vertical tube, the ones that flew out were considered successful. The effect of male age (0 to 21 d old), test time interval (30 min to 24 h), and the design of the device (40 and 80 cm height and 2 and 3.5 cm diameter) were evaluated. Our devices determined differences in the flight ability of Ae. aegypti males of different ages. During the first minutes, more old males escaped than young males in three out of four types of devices. However, young males reached higher rates of escape in all cases after 24 h. For standard quality control tests, we recommend testing 2- to 3-d-old sexually mature males in the high and narrow device (80 × 2 cm). Further observations for time intervals between 1 and 5 h might be performed to decide the shortest and more representative interval to use.

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