Showing 1–12 of 26 results
A fuzzy control system of diesel generator speed
Diesel generator, inرایگان!
Diesel generator, in which the generator is driven by the diesel engine to generate alternating current which frequency should keep stable and constant, is broadly used as mobile, urgent or field power sourc. The alternating current frequency is determined by the diesel speed. So the diesel speed should keep stable and constant too. This paper introduces two analogue control systems: rigid feedback and constant-speed feedback control system, and constructs a fuzzy control system of the diesel speed. Comparison of their control performances and practical applications indicate that the fuzzy control method is feasible and better than the others.
A REVIEW ON NANOFLUIDS – PART II: EXPERIMENTS AND APPLICATIONS
Research in convectiرایگان!
Research in convective heat transfer using suspensions of nanometer-sized solid particles in base liquids started only over the past decade. Recent investigations on nanofluids, as such suspensions are often called, indicate that the suspended nanoparticles markedly change the transport properties and heat transfer characteristics of the suspension. This second part of the review covers fluid flow and heat transfer characteristics of nanofluids in forced and free convection flows and potential applications of nanofluids. Opportunities for future research are identified as well.
Acoustic emission based drill condition monitoring during drilling of glass/phenolic polymeric composite using wavelet packet transform
Monitoring of tool cرایگان!
Monitoring of tool condition on the basis of sensor signals requires a selection of suitable signal processing technique and monitoring index, to assess the tool condition. In this paper, wavelet packet transform is used as a tool, to characterise the acoustic emission signals released from glass/phenolic polymeric composite during drilling. The results show that the selected monitoring indices from the wavelet packet coefficients are capable of detecting the drill condition effectively.
Alleviation of rolling contact fatigue on Sweden’s heavy haul railway
A test has been undeرایگان!
A test has been undertaken on Sweden’s Malmbanan, or iron ore railway, to reduce rolling contact fatigue (RCF) damage by developing a preventative maintenance regime involving routine grinding of the rails. In just the first 2 years of the test, the total cost of grinding plus rail replacements was reduced by almost 40%, while both the rail and track quality generally improved immensely. Although it may not be possible to reproduce such savings everywhere that RCF damage occurs, some lessons from the test are of general relevance. In particular, the development of even existing surface-initiated defects can effectively be halted by grinding and thereafter regularly reinstating, a profile which substantially removes loading from those cracks. In this test, the rate of metal removal by grinding was about 0.2 mm per 25 MGT. Methods were also developed for objectively monitoring the transverse and longitudinal profiles of the ground rail, and the depth of metal removed from the rail, i.e. the overall grinding “quality”. It would appear that the desired benefits of grinding can be obtained even if deviations of the transverse profile from a desired reference profile exceed specified limits over a significant fraction of the track.
An investigation of microstructure/property relationships in dissimilar welds between martensitic and austenitic stainless steels
The metallurgical chرایگان!
The metallurgical characteristics, tensile, hardness, toughness and corrosion resistance of dissimilar welds between X5CrNi18-10 grade austenitic and X20CrMo13 grade martensitic stainless steel have been evaluated. Both austenitic and duplex stainless steel electrodes were used to join this combination, using multipass manual metal arc welding process. Defect free welds were made with each welding consumable. It was found that the tensile strength of weldment, which was produced by duplex electrode (E2209-17), was slightly lower than that of austenitic electrode (E308L-16). The toughness of the both E2209-17 and E308L-16 deposits was acceptable even at low temperature regardless of heat input. Hardness was increased in both welds made with E2209-17 duplex and E308L-16 austenitic electrode along the X20CrMo13/weld metal fusion boundary due to heat annealing and then following high cooling rate. The pitting corrosion resistance of the weld metal made with E308L-16 and E2209-17 filler metal was found acceptable. Although, heat affected zone in the weldment and X20CrMo13 base metal were affected by electrolytic corrosion. This investigation has shown that both filler metals can be used to join austenitic stainless steel to the martensitic stainless steel.
Development of Brake System and Regenerative Braking Cooperative Control Algorithm for Automatic-Transmission-Based Hybrid Electric Vehicles
In this paper, a braرایگان!
In this paper, a brake system for an automatic transmission(AT)-based hybrid electric vehicle (HEV) is developed, and a regenerative braking cooperative control algorithm is proposed, with consideration of the characteristics of the brake system. The brake system does not require a pedal simulator or a fail-safe device, because a hydraulic brake is equipped on the rear wheels, and an electronic wedge brake (EWB) is equipped on the frontwheels of the vehicle. Dynamic models of the HEV equipped with the brake system developed in this study are obtained, and a performance simulator is developed. Furthermore, a regenerative braking cooperative control algorithm, which can increase the regenerative braking energy recovery, is suggested by considering the characteristics of the proposed hydraulic brake system. A simulation and a vehicle test show that the brake system and the regenerative braking cooperative control algorithm satisfy the demanded braking force by performing cooperative control between regenerative braking and friction braking. The regenerative braking cooperative control algorithm can increase energy recovery of the regenerative braking by increasing the gradient of the demanded braking force against the pedal stroke. The gradient of the demanded braking force needs to be determined withconsideration of the driver’s braking characteristics, regenerative braking energy, and the driving comfort.
Drilling of carbon composites using a one shot drill bit. Part I: Five stage representation of drilling and factors affecting maximum force and torque
The thrust force andرایگان!
The thrust force and torque produced during drilling contain important information related to the quality of the hole and the wear of thedrill bit . In this paper, the force and torque produced during drilling of carbon fibre using a ‘one shot’ drill bit is investigated. The signals in the time domain were divided into stages and common problems and defects associated with each stage discussed. It is also shown how tool wear and thickness of the workpiece affect the thrust force and torque throughout the drilling process. The findings of this paper are used to develop a mathematical model of the maximum thrust force and torque as described on Part II of this paper and are a valuable reference for future optimisation of drilling carbon composites with a ‘oneshot’ drill bit.
Effect of PWHT cycles on fatigue crack growth and toughness of quenched and tempered pressure vessel steels
Transportable pressure vessels, commonly manufactured from quenched and tempered (QT) steels, require mandatory postweld heat treatment (PWHT) regardless of plate thickness. During their life, transportable pressure vessels may have up to 4 PWHT cycles at temperatures between 540 and 590 ◦C, and concerns have emerged about possible effects on the mechanical properties of the base (parent) plate. This paper reports work on the resistance to fatigue crack growth, impact toughness and CTOD fracture toughness of two types of QT steels. The parent metal region was examined for both steels, and then exposed to temperatures and times in the PWHT range. Although there was a marginal decrease in the resistance to fatigue crack growth for up to four postweld heat treatment cycles, there was a significant decrease in impact toughness and CTOD fracture toughness.
Electrical discharge machining of ceramic/carbon nanostructure composites
The miniaturization of mechanical components with complex shapes is a great challenge in emerging applications. Silicon nitride (Si3N4) ceramics are excellent candidates for such applications due to their outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using normal mechanical machining methods. If the material were electrically conductive, electrical discharge machining (EDM) could be applied to produce precise and complex shapes. In this paper, in order to investigate the effects of electrical conductivity on the EDM characteristics, several carbon nanostructure composite materials are fabricated and EDMed using the assisting electrode method proposed by the current authors. The performance of the process is evaluated as a function of the carbon nanostructure content and type. The former is separately selected to be close to the electrical percolation threshold (0.9 vol.% and 5.3 vol.% for carbon nanotube (CNT) and graphene Nano platelet (GNP) composites, respectively), and well above that limit (5.3 vol.% and 20.6 vol.%), where electrical conductivities on the order of 10 and 100 S·m-1 are attained for CNTs and GNPs-based nanocomposites, respectively. In addition, bare Si3N4 specimens are also tested. Material removal rate, electrode wear ratio, and surface roughness of the machined pieces are analyzed for all testing conditions.
Fault-Tolerant Control for Electric Ground Vehicles With Independently-Actuated In-Wheel Motors
This paper presentsرایگان!
This paper presents an in-wheel motor fault diagnosis and fault-tolerant control method for four-wheel independently actuated (4WIA) electric vehicles. The 4WIA electric vehicle is one of the promising architectures for electric vehicles. While such a vehicle architecture greatly increases the flexibility for vehicle control, it also elevates the requirements on system reliability, safety, and fault tolerance due to the increased number of actuators. A fault diagnosis approach for finding the faulty in-wheel motor=motor driver pair is developed. The proposed diagnosis approach does not need an accurate knowledge on tire-road friction coefficient (TRFC) and is robust to tire force modeling inaccuracies. Based on the in-wheel motor=motor driver fault diagnosis mechanism, a control-allocation based vehicle fault-tolerant control system is designed to accommodate the in-wheel motor=motor driver fault by automatically allocating the control effort among other healthy wheels. Simulations using a high-fidelity, CarSimV R , full-vehicle model show the effectiveness of the proposed in-wheel motor=motor driver fault diagnosis and fault-tolerant control approaches.