A new approach to contour error control in high speed machining

High speed machining technology attempts to maximize productivity through the use of high spindle speeds and axis traverse rates. The technology is dependent upon the development of suitable mechanical hardware, electrical drives and associated control software to ensure that all components are used to maximum advantage. The role of the control software is particularly demanding since one needs to maximize traverse rates while providing the necessary accuracy, and indeed providing a margin of safety to deal with unexpected changes in process, or system parameters. There have been relatively few improvements in commercial CAD or CAM systems that would help machine tool users to take maximum advantage of high speed machining; rather the majority of the approaches have been undertaken at the machine tool controller level. This paper uses circular interpolation and corner tracking to compare several such control techniques, (Cross Coupled Control (CCC), Zero Phase Error Tracking Control (ZPETC), and Realtime Frequency Modulated Interpolation (FMI)), each of which have been proposed in the literature order to improve machining accuracy. None of these approaches are found to be universally successful when used alone and the authors, in this paper, examine the use of these systems in combination. Particular attention is focused upon an extension of a simplified version of cross coupled control together with Frequency Modulated Interpolation. It is shown that the combined system performs extremely well, and is easily actuated at high frequencies with conventional hardware. A custom built high speed x-y table is used to confirm system performance with multiple constraints present.     

Safety performance functions incorporating design consistency variables

Highway design which ensures that successive elements are coordinated in such a way as to produce harmonious and homogeneous driver performances along the road is considered consistent and safe. On the other hand, an alignment which requires drivers to handle high speed gradients and does not meet drivers' expectancy is considered inconsistent and produces higher crash frequency.     

TRT发电机启机故障诊断及技术分析

针对重钢16 MW高炉TRT发电机启机过程出现的在通过临界转速时发生较大振动导致联锁停机这一故障进行技术分析,并提出了整改方案,实施后运行状况良好。     

Mobile phone use while driving: A hybrid modeling approach

The analysis of the effects that mobile phone use produces while driving is a topic of great interest for the scientific community. There is consensus that using a mobile phone while driving increases the risk of exposure to traffic accidents. The purpose of this research is to evaluate the drivers’ behavior when they decide whether or not to use a mobile phone while driving. For that, a hybrid modeling approach that integrates a choice model with the latent variable “risk perception” was used. It was found that workers and individuals with the highest education level are more prone to use a mobile phone while driving than others. Also, “risk perception” is higher among individuals who have been previously fined and people who have been in an accident or almost been in an accident. It was also found that the tendency to use mobile phones while driving increases when the traffic speed reduces, but it decreases when the fine increases. Even though the urgency of the phone call is the most important explanatory variable in the choice model, the cost of the fine is an important attribute in order to control mobile phone use while driving.     

高速钢轧辊表面氧化膜研究

借助Gleeble 3500模拟机模拟了高速钢轧辊服役时表面工作层温度的升高,得到了循环加热冷却30次、50次及100次后试样表面的氧化膜。为对比分析,对高铬铸铁轧辊进行了循环50次的试验。利用扫描电子显微镜、X射线衍射分析仪、原子力显微镜对循环氧化后的试样表面氧化产物及其形貌进行了分析。结果表明:随着循环次数增加,高速钢轧辊氧化程度加剧,氧化膜更加致密;同样循环次数下,高铬铸铁轧辊氧化程度要比高速钢严重且氧化膜的粗糙度也大于高速钢。     

低速电机驱动翻板机构的设计与校核

介绍一种低速电机驱动连杆机构来实现接水翻板的运行,连杆机构设计为反平行四边形机构,由一台低速电机作为动力源、连杆作为执行机构、推动翻板打开与合拢,实现翻板接水工作,从而保证压滤机各工艺的正常。此方案结构简单,成本低廉,运行稳定可靠。     

Combustion behaviors and explosibility of suspended metal hydride TiH2 dust

In the production and storage processes of metal hydride material of TiH₂, there are at least three kinds of explosion hazards, for example, TiH₂ dust explosion, H₂ explosion and hybrid H₂/TiH₂ dust explosion. In this study, combustion behaviors of TiH₂ dust cloud under isobaric and isochoric conditions were studied using a visual dust combustion facility and a standard 20-L spherical explosion vessel bomb, respectively, and Ti dust and hybrid H₂/Ti dust were used as the reference materials. Experimental results showed that at equal dust concentrations, the flame propagation speed S_f, burning velocity S_L, maximum pressure rise P_ex and maximum rate of pressure rise (dP/dt)_ex of TiH₂ dust were all higher than those of Ti dust, while much smaller than those of hybrid H₂/Ti dust except the maximum pressure rise P_ex. The hydrogen state and content were the primary factors for the combustion differences of dust explosions. The values of explosion index K_st showed that the explosion risks of these samples increased as follows: Ti ˂ TiH₂ ˂ hybrid H₂/Ti dust.     

A new semi-empirical wind turbine capacity factor for maximizing annual electricity and hydrogen production

The capacity factor is an important wind turbine parameter which is ratio of average output electrical power to rated electrical power of the wind turbine. Another main factor, the AEP, the annual energy production, can be determined using wind characteristics and wind turbine performance. Lower rated power may lead to higher capacity factor but will reduce the AEP. Therefore, it is important to consider simultaneously both the capacity factor and the AEP in design or selecting a wind turbine. In this work, a new semi-empirical secondary capacity factor is introduced for determining a rated wind speed at which yearly energy and hydrogen production obtain a maximum value. This capacity factor is expressed as ratio of the AEP for wind turbine to yearly wind energy delivered by mean wind speed at the rotor swept area. The methodology is demonstrated using the empirical efficiency curve of Vestas-80 2 MW turbine and the Weibull probability density function. Simultaneous use of the primary and the secondary capacity factors are discussed for maximizing electrical energy and hence hydrogen production for different wind classes and economic feasibility are scrutinized in several wind stations in Kuwait.     

Consideration of multi‐coil type magnetization system for magnetic particle testing of omnidirectional crack in all surfaces of 3D shape test object

Mechanical parts, plants, and cross‐linkages inspected with magnetic‐particle testing (MT) are typically complex 3D shapes. In complex 3D shape portions, because a magnetizer often cannot be configured to inspection portions and the test object cannot be appropriately magnetized, there is a possibility of overlooking a crack in such an instance. Thus, MT system development that was successfully able to detect omnidirectional cracks in 3D shape portions was considered in this study's trials. Two multi‐coil type magnetizers were hence arranged face‐to‐face, and the magnetization of omnidirectional scenarios for all surfaces of 3D shape test object was evaluated.