The authors acknowledge the Beijing Institute of Precision Mechatronics and Controls for supporting this research.

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The authors have nothing to disclose.

The concept and other technical components of the EVDP have been presented in previous publications6,31, demonstrating the applicability and advantages of the EVDP. Instead of studying the EVDP itself, this paper continued to study the design method in relation to future real application needs. A specific design method is necessary for this type of highly integrated and multidisciplinary coupling product, which calls for delicate performance trade-offs and optimi...

Electro-hydrostatic actuators (EHAs) are receiving increasing interest for applications such as industrial presses, large mobile machinery, crane manipulators, and primary aircraft control due to their combination of the advantages of both electric actuators and hydraulic actuators1. Two basic types of EHAs can be identified: variable-speed EHAs and variable-displacement EHAs2. Currently, the variable-speed EHA is more popular than the variable-displacement EHA due to its higher efficiency and simplicity. However, along with the higher power level of the EHA, which is needed in heavy vehicles, such as heavy launch vehicles3 and submarines4, the driving motor and associated electronics of the variable-speed EHA have issues related to low dynamics, high thermal dissipation, high price, etc. Therefore, the variable-displacement EHA is being reconsidered for these high-power applications (&#62;30 kW), as its control is realized via a low-power device that regulates the pump displacement.
One major concern that prevents variable-displacement EHA being taken as a priority is its cumbersome pump displacement control unit, which itself is a complete valve-controlled hydraulic system. The electro-variable displacement pump (EVDP) has been proposed to address this issue by using a compact electric displacement control unit. This design improves the compactness, efficiency, etc., of the variable-displacement EHA, which resolves the previous weakness to a certain degree. Therefore, the use of variable-displacement EHAs for high-power applications may be facilitated by using the newly proposed EVDP. However, the complexity of the EVDP is significantly greater compared to the conventional hydraulically controlled variable-displacement pump as it integrates components from several new disciplines. Consequently, specific EVDP-based research activities have emerged. Our research group started the EVDP research5 and has continued to develop it6. Liu developed the EVDP for EHA applications and performed experimental tests7. Some hydraulic companies also provide EVDP products. In addition to the research regarding the technical components of the EVDP, the design method for responding to real application requirements is also significant for enhancing the EVDP&#39;s competence by further reducing the cost of using EVDPs and exploring their performance potential. Hence, a specific EVDP preliminary design method is necessary for optimizing trade-offs in its system-level performance by analyzing its coupled disciplines. The simulation-based preliminary design is of interest for this type of multidisciplinary coupling of mechatronic products8.
Although no specific simulation models for EVDP preliminary design have been proposed due to it being a newly proposed concept, much research has been invested in related mechatronic products. A dynamic EHA model has been built to optimize the weight, efficiency, and control performance in preliminary design9, but the lifetime, reliability, thermal characteristics, etc., were not involved, which are essential performance indexes that should be considered in preliminary design. Another dynamic EHA model has also been used to optimize cost, efficiency, and control performance10, and a thermal model was subsequently developed to evaluate the thermal characteristics of the optimized EHA11, but the reliability and lifetime were not considered. A comprehensive electro-mechanical actuator (EMA) preliminary design method has been presented12. Specific models with different functions capable of analyzing different characteristics have been proposed for this method, and reliability and lifetime models have also been developed13. The mechanical strength, power capability, thermal performance, etc., could hereby be evaluated, but the control performance was not involved. Another EMA preliminary design method utilized a dynamic EMA model and associated component sizing models14. The cost, weight, fatigue life, power capacity, physical constraints, etc., were involved in the simulation analysis, but reliability and control performance were not included. A dynamic model was proposed for the optimization design of a hydraulic hybrid drive train15. The power capacity, efficiency, control, etc., could be simulated, but the reliability and life were not considered. Models for analyzing an EHA-based flight control actuation system have been proposed, within which simple power transmission equations and weight functions were used16. Considering that the models were used for vehicle-level and mission-level analyses, the limited attribute coverage of the models was appropriate. As a major component of the EHA, servo motors have attracted separate attention regarding modeling and design, and the results are also instructive for EHA model development. Thermal networks, weight models, etc., can also be considered for EHA modeling17,18,19. The reviewed literature indicates that, even considering the results from products related to the EVDP, the developed models do not analyze all the influential performance attributes of the products for the preliminary design. The control performance, thermal performance, reliability, and lifetime are the attributes that have been most neglected in construction of the models. Therefore, this paper proposes a model package capable of analyzing all the most influential performance attributes for the EVDP preliminary design. The simulation analysis is also presented to better illustrate the model functions. This paper is an extension of a previous publication20, as it improves the parameter generation, involves the lifetime model, reliability model, and control model, optimizes the calculation cost, validates the model, and conducts in-depth simulation analysis, etc.
The conventional hydraulic control unit of a variable-displacement piston pump is replaced with an electric actuator to improve the compactness and reduce heat dissipation, as shown in Figure 1. The electric actuator consists of a ball screw, a gearbox, and a permanent magnet synchronous motor (PMSM). The electric actuator connects the swashplate via a bar to regulate the pump displacement. When applied in EHAs, the EVDP swashplate rotational position is closed-loop controlled by modulating the PMSM. The electric actuator is integrated with the piston pump in a mutual case to form an integral component. This design submerges the electric actuator in the working fluid and hereby strengthens the multi-domain coupling effects.
As the EVDP is a typical multi-domain mechatronic product, its preliminary design plays an essential role in optimizing trade-offs in its system-level performance and outlining the component design requirements. The process is illustrated in Figure 2 based on the simulation-based design scheme10,12. Step 1 firstly analyzes the selected EVDP architecture, as in Figure 1, and concludes the design parameters based on the specified performance requirements. Then, the design task is usually transformed into an optimization problem to explore the performance optimization of the EVDP. This is carried out by converting the design parameters into optimization variables and converting the performance requirements into objectives and constraints. It is worth noting that the design parameters need to be classified into active, driven, and empirical categories. Only the active parameters are used as optimization variables due to their independence features. The other two categories are automatically generated by estimation from the active parameters. Therefore, Step 2 develops the estimation models of the driven and empirical parameters. These estimation tools are used in each iteration of the optimization, as well as in Step 5 for formulating all the required simulation parameters. Step 3 builds the calculation models for each optimization objective or constraint, which reflects the required performance. These models should be computationally efficient; otherwise, the optimization calculation cost would be unacceptable. Step 4 performs the optimization calculation, which is usually multi-objective and multidisciplinary. It also deals with the parameter uncertainties in the preliminary design phase. Step 5 constructs an overall model of the designed EVDP and uses it for validating the optimization results by simulating the EVDP under typical duty cycles. This model is the ultimate tool for evaluating the preliminary design results. Therefore, this model should have the highest fidelity and involve all the influential characteristics in a tight coupling style. Finally, the preliminary design performance results and the system-level dimensioning results are obtained.
This paper focuses on the system modeling and simulation method of the EVDP, which involves conducting the parameter analysis in Step 1 and completing Steps 2 and 5. Firstly, the design parameters are derived based on the EVDP architecture and the design requirements, and they are classified into three sub-categories. Secondly, the estimation models for the non-active parameters are developed based on scaling laws, component catalogs, empirical functions, etc. Thirdly, the overall model of the EVDP is constructed using multidisciplinary coupling equations and additional lifetime and reliability sub-models, and the model is partially verified by experiments. Lastly, the previous sizing results are imported into the constructed model to perform simulation analysis under typical duty cycles. The system-level performance is deduced based on the simulation results. The parameter sensitivity and the robustness of the design are also evaluated. As a result, this paper develops a specific modeling and simulation method for EVDP preliminary design. The EVDP&#39;s performance for application in the EHA is comprehensively predicted. The proposed method stands as a practical tool for developing EVDPs and variable-displacement EHAs for high-power applications. The method can also be referred to for developing simulation tools for other types of mechatronic products. The EVDP in this paper refers to the electro-mechanically controlled variable-displacement pump, but the electro-hydraulically controlled variable-displacement pump is out of the scope of this paper.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Ball screw</td>
			<td>NSK</td>
			<td>PSS</td>
			<td></td>
		</tr>
		<tr>
			<td>EVDP prototype</td>
			<td>Beijing Institute of Precision Mechatronics and Controls</td>
			<td>customized</td>
			<td>7.4 mL/rev, 7000 rpm, 21 Mpa</td>
		</tr>
		<tr>
			<td>EVDP testrig</td>
			<td>Beijing Institute of Precision Mechatronics and Controls</td>
			<td>customized</td>
			<td>Refer to Figure 7, can be adapted upon individual needs. Including Power PMAC controller, ELMO Whistle Driver, etc.</td>
		</tr>
		<tr>
			<td>Gearhead</td>
			<td>Maxon</td>
			<td>GP</td>
			<td></td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>Mathworks</td>
			<td>R2020a</td>
			<td></td>
		</tr>
		<tr>
			<td>Permannet magnet synchronous motor</td>
			<td>Maxon</td>
			<td>393023</td>
			<td></td>
		</tr>
		<tr>
			<td>Piston pump</td>
			<td>Bosch Rexroth</td>
			<td>A10VZO</td>
			<td></td>
		</tr>
		<tr>
			<td>Simcenter Amesim</td>
			<td>Siemens</td>
			<td>2021.1</td>
			<td>system simulation platform</td>
		</tr>
	</tbody>
</table>

a modeling and simulation method for preliminary design of an electro-variable displacement pump

Electro-hydrostatic actuators (EHAs) have been considerably researched in academia, and their applications in various industrial fields are expanding. The variable-speed EHA has now taken priority over the variable-displacement EHA, but its driving motor and associated electronics encounter issues when applied in high-power applications: low-dynamics, high thermal dissipation, high price, etc. Therefore, a variable-displacement EHA equipped with an electro-variable displacement pump (EVDP) has been considered. The EVDP itself is a mechatronic system that integrates a piston pump, a ball screw, a gearbox, and a permanent magnet synchronous motor (PMSM). Consequently, the EVDP needs to be investigated to ensure its system-level performance when applied in an EHA. In addition to the previous research on the technical parameters of the EVDP, a dedicated design method is necessary for further reducing the cost of using the EVDP and exploring its performance potential. Here, a simulation based EVDP preliminary design method is selected for designing a 37 kW EVDP. Firstly, a previously proposed multidisciplinary model of the EVDP is extended by improving the parameter generation, including the EVDP life, reliability, control models, etc. Secondly, the proposed model is partially verified using a downsized prototype. Thirdly, the EVDP is simulated at a system level, supported by the proposed model. The EVDP performance is evaluated according to the specified design requirements. The temperature, bandwidth and accuracy, reliability and lifetime, etc., are all predicted for the EVDP. The simulation results demonstrate the EVDP's applicability in variable-displacement EHA. The proposed modeling and simulation method can be used to evaluate diverse EVDP performance and respond to general design requirements. The method can also support the resolution of the preliminary design challenges in terms of limited information and robustness. Therefore, the proposed method is appropriate for the realization of the simulation-based EVDP preliminary design method.

This section presents the results obtained from performing all the protocol steps, which constitute part of Step 1, all of Step 2, and all of Step 5 of the EVDP preliminary design method in Figure 2. The input information in the protocol includes the EVDP schematics in Figure 1, the optimized active parameters (clarified in Step 5.1.1.) of the EVDP from Step 4 of Figure 2, and the EVDP performance simulation tasks, which relate to t...

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A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump

A simulation model specifically supporting the preliminary design of an electro-variable displacement pump (EVDP) is developed and partially verified by experiments. The control performance, life, reliability, etc., can all be evaluated using the proposed model, which covers the main performance requirements under the EVDP preliminary design task.

Electro-hydrostatic actuators (EHAs) have been considerably researched in academia, and their applications in various industrial fields are expanding. The ...

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Virtual Work

SCIENTISTS IN ACTION

2.9K Views.  Beihang University. Supporto attivatori elettroidrostatici per l'elettrificazione di sistemi heavy duty. Per ottenere un minor consumo di energia, il nostro metodo si concentra sull'ottimizzazione, sull'utilizzo della pompa volumetrica elettromodale dei sistemi. La nostra modellazione e il metodo di simulazione supportano la progettazione preliminare.La nostra pompa a cilindrata elettrovariabile, che dovrebbe scegliere la previsione completa delle prestazioni, la generazione automatica dei parametri e la ...

Video: A Modeling and Simulation Method for Preliminary Design of an Electro-Variable Displacement Pump

Design and Use of a Full Flow Sampling System (FFS) for the Quantification of Methane Emissions

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas industry faces continued scrutiny for methane emissions from across the supply chain, due to methane&#39;s relatively high global warming potential (25-84x that of carbon dioxide, according to the Energy Information Administration). Currently, a variety of techniques of varied uncertainties exists to measure or estimate methane emissions from components or facilities. Currently, only one commercial system is available for quantification of component level emissions and recent reports have highlighted its weaknesses.
In order to improve accuracy and increase measurement flexibility, we have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases based on transportation emissions measurement principles. The FFS is a modular system that consists of an explosive-proof blower(s), mass airflow sensor(s) (MAF), thermocouple, sample probe, constant volume sampling pump, laser based greenhouse gas sensor, data acquisition device, and analysis software. Dependent upon the blower and hose configuration employed, the current FFS is able to achieve a flow rate ranging from 40 to 1,500 standard cubic feet per minute (SCFM). Utilization of laser-based sensors mitigates interference from higher hydrocarbons (C2+). Co-measurement of water vapor allows for humidity correction. The system is portable, with multiple configurations for a variety of applications ranging from being carried by a person to being mounted in a hand drawn cart, on-road vehicle bed, or from the bed of utility terrain vehicles (UTVs). The FFS is able to quantify methane emission rates with a relative uncertainty of &#177; 4.4%. The FFS has proven, real world operation for the quantification of methane emissions occurring in conventional and remote facilities.

Design and Use of a Full Flow Sampling System FFS for the Quantification of Methane Emissions

We have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases from across the natural gas supply chain.

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas ...

Study of Siphon Breaker Experiment and Simulation for a Research Reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively.
To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli&#39;s equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system.
In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results well.

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent ...

The Modular Design and Production of an Intelligent Robot Based on a Closed-Loop Control Strategy

Intelligent robots are part of a new generation of robots that are able to sense the surrounding environment, plan their own actions and eventually reach their targets. In recent years, reliance upon robots in both daily life and industry has increased. The protocol proposed in this paper describes the design and production of a handling robot with an intelligent search algorithm and an autonomous identification function.
First, the various working modules are mechanically assembled to complete the construction of the work platform and the installation of the robotic manipulator. Then, we design a closed-loop control system and a four-quadrant motor control strategy, with the aid of debugging software, as well as set steering gear identity (ID), baud rate and other working parameters to ensure that the robot achieves the desired dynamic performance and low energy consumption. Next, we debug the sensor to achieve multi-sensor fusion to accurately acquire environmental information. Finally, we implement the relevant algorithm, which can recognize the success of the robot&#39;s function for a given application.
The advantage of this approach is its reliability and flexibility, as the users can develop a variety of hardware construction programs and utilize the comprehensive debugger to implement an intelligent control strategy. This allows users to set personalized requirements based on their needs with high efficiency and robustness.

We present a protocol on modular design and production of intelligent robots to help scientific and technical workers design intelligent robots with special production tasks based on personal needs and individualized design.

Intelligent robots are part of a new generation of robots that are able to sense the surrounding environment, plan their own actions and eventually reach ...

Design and Fabrication of an Optical Fiber Made of Water

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with solid-cladding devices, capillary oscillations are not restricted, allowing the fiber walls to move and vibrate. The fiber is constructed by a high direct current (DC) voltage of several thousand volts (kV) between two water reservoirs that creates a floating water thread, known as a water bridge. Through the choice of micropipettes, it is possible to control the maximal diameter and length of the fiber. Optical fiber couplers, at both sides of the bridge, activate it as an optical waveguide, allowing researchers to monitor the water fiber capillary body waves through transmission modulation and, therefore, deducing changes in surface tension.
Co-confining two important wave types, capillary and electromagnetic, opens a new path of research in the interactions between light and liquid-wall devices. Water-walled microdevices are a million times softer than their solid counterparts, accordingly improving the response to minute forces.

This protocol describes the design and manufacture of a water bridge and its activation as a water fiber. The experiment demonstrates that capillary resonances of the water fiber modulate its optical transmission.

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with ...

A Random-displacement Measurement by Combining a Magnetic Scale and Two Fiber Bragg Gratings

Long-distance displacement measurements using optical fibers have always been a challenge in both basic research and industrial production. We developed and characterized a temperature-independent fiber Bragg grating (FBG)-based random-displacement sensor that adopts a magnetic scale as a novel transferring mechanism. By detecting shifts of two FBG center wavelengths, a full-range measurement can be obtained with a magnetic scale. For identification of the clockwise and counterclockwise rotation direction of the motor (in fact, the direction of movement of the object to be tested), there is a sinusoidal relationship between the displacement and the center wavelength shift of the FBG; as the anticlockwise rotation alternates, the center wavelength shift of the second FBG detector shows a leading phase difference of around 90&#176; (+90&#176;). As the clockwise rotation alternates, the center wavelength shift of the second FBG displays a lagging phase difference of around 90&#176; (-90&#176;). At the same time, the two FBG-based sensors are temperature independent. If there is some need for a remote monitor without any electromagnetic interference, this striking approach makes them a useful tool for determining the random displacement. This methodology is appropriate for industrial production. As the structure of the whole system is relatively simple, this displacement sensor can be used in commercial production. In addition to it being a displacement sensor, it can be used to measure other parameters, such as velocity and acceleration.

A protocol to create a full-range linear displacement sensor, combining two packaged fiber Bragg grating detectors with a magnetic scale, is presented.

Long-distance displacement measurements using optical fibers have always been a challenge in both basic research and industrial production. We developed ...

A 100 KW Class Applied-field Magnetoplasmadynamic Thruster

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate plasma to high speed; they have considerable potential for future space applications with the significant advantages of high specific impulse and thrust density. In this paper, we present a series of protocols for designing and manufacturing a 100 kW class of AF-MPD thruster with water-cooling structures, a 130 V maximum discharge voltage, a 800 A maximum discharge current, and a 0.25 T maximum strength of magnetic field. A hollow tantalum tungsten cathode acts as the only propellant inlet to inhibit the radial discharge, and it is positioned axially at the rear of the anode in order to relieve anode starvation. A cylindrical divergent copper anode is employed to decrease anode power deposition, where the length has been reduced to decrease the wall-plasma connecting area. Experiments utilized a vacuum system that can achieve a working vacuum of 0.01 Pa for a total propellant mass flow rate lower than 40 mg/s and a target thrust stand. The thruster tests were carried out to measure the effects of the working parameters such as propellant flow rates, the discharge current, and the strength of applied magnetic field on the performance and to allow appropriate analysis. The thruster could be operated continuously for significant periods of time with little erosion on the hollow cathode surface. The maximum power of the thruster is 100 kW, and the performance of this water-cooled configuration is comparable with that of thrusters reported in the literature.

The goal of this protocol is to introduce the design of a 100 kW class applied-field magnetoplasmadynamic thruster and relevant experimental methods.

Applied-field magnetoplasmadynamic thrusters (AF-MPD thrusters) are hybrid accelerators in which electromagnetic and gas dynamic processes accelerate ...

Structural Design and Manufacturing of a Cruiser Class Solar Vehicle

Cruisers are multi-occupant solar vehicles that are conceived to compete in long-range (over 3,000 km) solar races based on the best compromise between the energy consumption and the payload. They must comply to the race&#39;s rules regarding the overall dimensions, the solar panel size, functionality, and safety and structural requirements, while the shape, the materials, the powertrain, and the mechanics are considered at the discretion of the designer. In this work, the most relevant aspects of the structural design process of a full-carbon fiber-reinforced plastic solar vehicle are detailed. In particular, the protocols used for the design of the lamination sequence of the chassis, the leaf springs structural analysis, and the crash test numerical simulation of the vehicle, including the safety cage, are described. The complexity of the design methodology of fiber-reinforced composite structures is compensated by the possibility of tailoring their mechanical characteristics and optimizing the overall weight of the car.

In this work, several aspects related to the structural design process of a full-carbon fiber-reinforced plastic solar vehicle are detailed, focusing on the monocoque chassis, the leaf springs, and the vehicle as a whole during a crash test.

Cruisers are multi-occupant solar vehicles that are conceived to compete in long-range (over 3,000 km) solar races based on the best compromise between ...

Design and Implementation of a Bespoke Robotic Manipulator for Extra-corporeal Ultrasound

With the potential for high precision, dexterity, and repeatability, a self-tracked robotic system can be employed to assist the acquisition of real-time ultrasound. However, limited numbers of robots designed for extra-corporeal ultrasound have been successfully translated into clinical use. In this study, we aim to build a bespoke robotic manipulator for extra-corporeal ultrasound examination, which is lightweight and has a small footprint. The robot is formed by five specially shaped links and custom-made joint mechanisms for probe manipulation, to cover the necessary range of motion with redundant degrees of freedom to ensure the patient&#39;s safety. The mechanical safety is emphasized with a clutch mechanism, to limit the force applied to patients. As a result of the design, the total weight of the manipulator is less than 2 kg and the length of the manipulator is about 25 cm. The design has been implemented, and simulation, phantom, and volunteer studies have been performed, to validate the range of motion, the ability to make fine adjustments, mechanical reliability, and the safe operation of the clutch. This paper details the design and implementation of the bespoke robotic ultrasound manipulator, with the design and assembly methods illustrated. Testing results to demonstrate the design features and clinical experience of using the system are presented. It is concluded that the current proposed robotic manipulator meets the requirements as a bespoke system for extra-corporeal ultrasound examination and has great potential to be translated into clinical use.

This paper introduces the design and implementation of a bespoke robotic manipulator for extra-corporeal ultrasound examination. The system has five degrees of freedom with lightweight joints made by 3D printing and a mechanical clutch for safety management.

With the potential for high precision, dexterity, and repeatability, a self-tracked robotic system can be employed to assist the acquisition of real-time ...

A Rapid Method for Modeling a Variable Cycle Engine

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft engines. However, developing VCE requires high costs. Thus, it is essential to build a mathematical model when developing an aircraft engine, which may avoid a large number of real tests and reduce the cost dramatically. Modeling is also crucial in control law development. In this article, based on a graphical simulation environment, a rapid method for modeling a double bypass variable cycle engine using object-oriented modeling technology and modular hierarchical architecture is described. Firstly, the mathematical model of each component is built based on the thermodynamic calculation. Then, a hierarchical engine model is built via the combination of each component mathematical model and the N-R solver module. Finally, the static and dynamic simulations are carried out in the model and the simulation results prove the effectiveness of the modeling method. The VCE model built through this method has the advantages of clear structure and real-time observation.

Here, we present a protocol to build a component-level mathematical model for a variable cycle engine.

The variable cycle engines (VCE) that combine the advantages of turbofan and turbojet engines, are widely considered to be the next generation aircraft ...

Crack Monitoring in Resonance Fatigue Testing of Welded Specimens Using Digital Image Correlation

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It is intended as a practical and reproducible procedure to identify macroscopic cracks at an early stage and monitor crack propagation during fatigue tests. It consists of strain field measurements at the weld using DIC. Images are taken at fixed load cycle intervals. Cracks become visible in the computed strain field as elevated strains. This way, the whole width of a small-scale specimen can be monitored to detect where and when a crack initiates. Subsequently, it is possible to monitor the development of the crack length. Because the resulting images are saved, the results are verifiable and comparable. The procedure is limited to cracks initiating at the surface and is intended for fatigue tests under laboratory conditions. By visualizing the crack, the presented procedure allows direct observation of macrocracks from their formation until rupture of the specimen.

Digital image correlation is used in fatigue tests on a resonance testing machine to detect macroscopic cracks and monitor crack propagation in welded specimens. Cracks on the specimen surface become visible as increased strains.

A procedure using digital image correlation (DIC) to detect cracks on welded specimens during fatigue tests on resonance testing machines is presented. It ...