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Aluminum alloys are applicable in marine and aero fields. Alloys AA5083 and AA6061 are aluminum alloys with different chemical and physical properties. Combination of two dissimilar materials could result in enhanced strength. Generally, dissimilar aluminum alloy joint is made by friction stir welding (FSW) to achieve improved physical properties compared with the parent alloys. The purpose of this research is to develop a new FSW dissimilar material with enhanced properties using AA5083 and AA6061 alloys.

In this research, FSW joint was made for butt joint configuration using AA5083 and AA6061 aluminum alloys. Cylindrical pin with threaded profile was used to perform the joint. The tool tilting angle was maintained as constant, and the tool rotational speed and the welding speed were varied. Wear performance and mechanical strength of the joint were analyzed.

The results revealed that the increase of tool rotational speed led to poor wear performance, whereas increase of welding speed showed a better wear performance. Further, the prepared joint was analyzed for different wear parameters such as sliding velocity and applied load. The results displayed that the increase of sliding velocity exhibited low wear rate and the increase of load showed high wear rate.

This work is original and deals with the wear performance of AA5083–AA6061 joint at different tool rotational and welding speeds.

We use a combination of continuum and car-following models to explore the potential impact of speed-controls on (i) decreasing travel times at times of congested flow; and (ii) increasing the safety of motorway flow approaching the site of an accident.

The present findings report a significant influence of disc profile and thickness on the order of excitation leading to critical speed condition. Certain transverse modes of vibration of the disc have been obtained to be more susceptible to get excited while recording the lowest critical speeds.

Numerical simulation using finite-element method has been adopted due to the complicated geometry, complex loadings and intricate analytical formulation. A comprehensive analysis of exclusive as well as combination of thermal and centrifugal loads has been taken up to determine the intensity and characteristics of the individual/combined effects.

The typical gas turbine disc profile has been analyzed to predict the critical speed under the factual working condition of an aero-engine. FEM analysis of uniform and variable thickness discs have been carried out under stationary, rotating and rotating-thermal considerations while emphasizing the effect of disc profile and thickness. Centrifugal stresses developed due to rotational effect result in unceasing stiffening of the discs with higher stiffening for a greater number of nodal diameters. On the other hand, a role reversal of thermal effect from stiffening to softening is figured out with increasing numbers of nodal diameters. However, the discs are subjected to an overall stiffening effect on account of the combined centrifugal and thermal loading, with the effect decreasing with an increase in disc thickness. Under the combined loading, the order of excitation leading to critical speed condition is dependent on disc profile and thickness. Moreover, the vibrational modes (0,1) and (0,2) are identified as more prominent adverse modes corresponding to lowest critical speeds.

The present findings are expected to serve as guidelines during the design phase of gas turbine discs of aeroengine applications.

The present work deliberates on the simulation and analysis of gas turbine disc specific to aeroengine application. The real-life disc geometry has been analyzed with due consideration of major factual operating conditions to identify the critical speed. The identification of various critical speed using numerical analysis can help to reduce the number of experimental tests required for certification.

In service, the periodic clashes of wheel flat against the rail result in large wheel/rail impact force and high-frequency vibration, leading to severe damage on the wheelset, rail and track structure. This study aims to analyze characteristics and dynamic impact law of wheel and rail caused by wheel flat of high-speed trains.

A full-scale high-speed wheel/rail interface test rig was used for the test of the dynamic impact of wheel/rail caused by wheel flat of high-speed train. With wheel flats of different lengths, widths and depths manually set around the rolling circle of the wheel tread, and wheel/rail dynamic impact tests to the flats in the speed range of 0–400 km/h on the rig were conducted.

As the speed goes up, the flat induced the maximum of the wheel/rail dynamic impact force increases rapidly before it reaches its limit at the speed of around 35 km/h. It then goes down gradually as the speed continues to grow. The impact of flat wheel on rail leads to 100–500 Hz middle-frequency vibration, and around 2,000 Hz and 6,000 Hz high-frequency vibration. In case of any wheel flat found during operation, the train speed shall be controlled according to the status of the flat and avoid the running speed of 20 km/h–80 km/h as much as possible.

The research can provide a new method to obtain the dynamic impact of wheel/rail caused by wheel flat by a full-scale high-speed wheel/rail interface test rig. The relations among the flat size, the running speed and the dynamic impact are hopefully of reference to the building of speed limits for HSR wheel flat of different degrees.

Friction pairs of the hydro-viscous drive speed regulating start device should be designed based on the rated torque. To obtain design basis of the rated torque of the hydro-viscous drive speed regulating start device, studies on effect of torque ratio (a ratio of the load torque to the rated torque) on speed regulating start were carried out theoretically and experimentally.

Under different torque ratio, the modified Reynolds, the thermal energy and the viscosity-temperature equations were solved simultaneously by using finite element method to reveal variation laws of the oil film load capacity and torque transmission during the starting process. Then, speed regulating start experiments were carried out to study the following performance of the output speed.

The results show that oil film thickness decreases with the increase of the torque ratio; when oil film thickness is less than 0.05 mm, oil film temperature increases rapidly with the decrease of oil film thickness, which eventually deteriorates performance of the speed regulating start; when the torque ratio decreases to about 0.3, output speed shows a better following performance.

It indicates that, to acquire a better speed regulating start, the rated torque of the hydro-viscous drive speed regulating start device should not be less than three times of the load torque. Achievements of this work provide theoretical basis for optimal design of the friction pairs of the hydro-viscous drive speed regulating start device.

The purpose of this paper is to reveal the effect of working oil temperature, load and starting time on hydro‐viscous drive speed‐regulating start.

The authors developed an experimental equipment and carried out a number of experiments under different temperatures, load and starting time.

The results show that both the temperature rise of working oil and the increase of load can induce fluctuations in output speed, but the effect of the working oil temperature rise is more serious; also the longer the starting time is, the more perfectly the output speed can trace the given speed.

It indicates that the working oil temperature should be kept in a certain range by using a cooling device in practical application; and that under this experimental condition, kinematics viscosity of the working oil should be greater than 45 mm²/s under rated working temperature, and the relatively suitable starting time should range from 90 to 120 s.

The paper explains the effect of various factors on speed‐regulating start, and provides the basis for the design and the application of hydro‐viscous drives.

The purpose of this paper is to introduce the structure design process of the cantilever spindle with limited installation space and wishing to increase its critical speed.

In this paper, the finite element method was used to analyze the influence of the supporting stiffness and the structure of the spindle on the critical speed, and then the structure of the spindle was designed; moreover, the experiment was accomplished and the experiment results show that the spindle can work stably.

Through analyzing the influence of the supporting stiffness and the structure of the spindle on the critical speed, the following conclusions could be obtained: the shape of the first-mode is the bend vibration of the cantilever of the spindle; the first-order critical speed of the spindle gradually decreases with the diameter and length of the cantilever increasing; the first-order critical speed of the spindle increases with the depth and diameter of the blind hole increasing; and the experiment was accomplished and the experiment results show that the spindle can work stably.

In this paper, the finite element method was used to design the spindle of the testing machine, and satisfactory results were obtained. It can provide a theoretical reference for the design of a similar spindle.

It is now well known among aircraft engineers that the compressibility of the air has an increasingly important effect on the aerodynamic forces as the flight speed rises and approaches the speed of sound. As a result of the development of the gas turbine and other improvements, aircraft speeds have risen very rapidly during the last few years, and compressibility effects are, therefore, of great importance in many new aircraft designs. Unfortunately, the designer is faced with very great difficulties in attempting to predict the behaviour of a new aircraft flying at high speeds. The main reason for this is simply that there is very little systematic knowledge of air flow at high speeds past wings and bodies. A further difficulty arises because many of the methods and ideas which have proved so useful in the design of low speed aircraft may have to be changed completely when high speeds are considered. To mention only one example, it is well known that at low speeds a separation of the boundary layer at the rear of an aerofoil causes an increase of drag, but is not so well known that a separation of the same kind at supersonic speeds causes a reduction of drag (for a given incidence). Because there may be differences as important as this between high and low speeds it is not enough that the designer should merely modify his present methods and ideas to allow for compressibility; he must regard the design problems of high speed flight as completely new ones, and acquire a new scientific background to deal with them. It is important that the designer of high speed aircraft should have a sound knowledge of the fundamental principles of air flow at high speeds. Unfortunately, much of the information which is available on this subject is scattered among a large number of books and reports, and is not easily accessible. Thus there is a great need for a book giving a concise introduction to the subject, to enable the aircraft designer to read and understand the current reports dealing with recent developments, and to provide the scientific background which is so necessary for good design.

THE sinking speed of an, aeroplane is defined as the vertical component of the forward velocity in gliding flight. It is easy to show that the sinking speed so defined is included in the general equation of the rate of climb with engine on, the rate of climb being the difference between the “rising speed,” corresponding with the horsepower available, and the sinking speed, which in turn corresponds with the horse‐power required. Thus the sinking speed always plays an important rôle in all conditions of flight and it is the author's opinion that, especially in performance calculations, the use of the quantities rising an,d sinking speed are preferable to the more commonly used power‐quantities.

This paper aims to obtain an accurate and robust estimation method of the rotor flux and speed for the sensorless induction motor (IM) drive.

The reduced order observer has been used as an online tuned rotor flux model in the model reference adaptive system (MRAS) concept applied for the IM speed estimation. The output of this observer was used also as a feedback signal required in the direct field‐oriented control (DFOC) structure of the IM.

It is shown that a new rotor flux and speed estimator are more robust to motor parameter changes in comparison with the classical MRAS estimator and can work stably in the DFOC structure, in the wide speed range, even for relatively high (50 per cent) identification errors of equivalent circuit parameters of the IM.

The investigation looked mainly at the estimation accuracy performance and whole system stability while economic issues will still need to be addressed.

The proposed new improved MRAS speed estimator can be easily realised using modern digital signal processors. The implementation was tested in an experimental set‐up with floating point DSP used as the system controller. The fixed‐point realisation needs to be developed to obtain the practical application in the industrial drive systems.

The application of the reduced order flux observer as a tuned flux model in the MRAS type speed estimator instead of the simple, but very sensitive to motor parameter uncertainties, current flux model, enables much better accuracy and stability of the rotor speed estimation in the complex DFOC structure than in the case of classical MRAS estimator.