Preparation of the projectile rotating band and its performance evaluation

Alternative materials are being investigated as substitution of the traditional copper rotating band, in order to solve problems associated with their mechanical and physical properties. Meanwhile, new processes for joining the rotating band on the projectile body have also to be developed because of different material physical properties. In this paper, swaging, welding, and newly developed spraying technologies for fabricating rotating band are analyzed, respectively. Quasi-static and dynamic engraving methods are presented for evaluating the performance of as-prepared rotating band. The former was performed on an 810 Material Testing System and the latter was carried out by using a specially developed gas-gun-based impact test rig. Hoop and axial direction strain gauges were positioned on the exterior of the barrel to monitor the effect of the rotating band on the barrel during engraving process. It is suggested that aluminum bronze coating prepared by the High Velocity Arc Spraying (HVAS) process should be a good candidate for application to a rotating band of medium- and large- caliber projectiles. The measured strains were found to be dependent on a set of variables, such as loading rate, band material and structure, forcing cone and rifling (land and groove) structure, bore condition (oiled or dry), etc. The loading rate has been verified as the most important factor and the essential difference among quasi-static engraving, dynamic engraving, and actual firing.     

Development of a mechanical rock breakage experimental platform

With social and economic development and improvement of science and technology, tunnel boring machines, raise boring machines, reaming machines and road headers have been unprecedentedly applied to underground engineering construction. Mechanical rock breakage experiments became an indispensable mean for mechanical excavation of underground engineering. It can also guide the design and operation of excavation machines. This paper introduces the new mechanical rock breakage experimental platform developed by Beijing University of Technology. The design and manufacture of this platform considered the influence of high in situ stress, cutter head rotation and rock breakage by multi-cutters at the same time on the rock breakage process. Different tools, such as rolling cutters, scraper, ripper, and pick, for different excavation machines can be tested in the platform. It can also take into account the different rock mass structure in the sample box. Different construction conditions with different cutting tools can be realistically modeled. The experimental platform consists of a mechanical system, a hydraulic system, an automatic control system and a data acquisition system. After installation of the designed experimental platform, several tests with different construction conditions were conducted. The experimental results showed that the platform reached its design requirements.     

Encoder based online motion planning and feedback control of redundant manipulators

This paper proposes and investigates an online motion planning and feedback control (OMPFC) scheme for redundant manipulators via techniques of quadratic programming and rotary encoder. The proposed OMPFC scheme is performed on a planar six degrees-of-freedom (DOF) manipulator. This robotic scheme incorporates the feedback of task-space position error. The joint state is obtained in real time via rotary encoders equipped on the physical manipulator. The original scheme is finally reformulated as a unified quadratic program (QP). The QP is solved online during the joint motion by employing an efficient numerical algorithm. Simulation and experimental results validate the physical realizability, online property, and efficacy of the proposed OMPFC scheme (including the employed numerical algorithm).     

Nitrogen in SL/RN direct reduced iron: origin and effect on nitrogen control in EAF steelmaking

Abstract

In the steel plant considered here, direct reduced iron (DRI), produced by the coal based Stelco–Lurgi/Republic–National (SL/RN) process, makes up 50% or more of the total iron charge. The SL/RN DRI samples from a kiln cooler had high nitrogen contents (50–250 ppm, depending on particle size), contributing to elevated nitrogen levels in liquid steel produced in the electric arc furnaces. The proposed mechanism of nitriding of SL/RN DRI involves gaseous nitrogen (present within the rotary cooler) diffusing into the solid bed and is supported by a simple diffusion model. A strong correlation was found between the melt-in carbon content of the liquid steel and the final tap nitrogen content, with melt-in carbon of 0·3%C or higher resulting in nitrogen levels below 50 ppm at tap, even when charging DRI material that is high in nitrogen.     

Metal forming and forging – finding a new place within high value manufacturing through advanced,industrial scale research

Abstract

Since the banking crisis governments have placed renewed emphasis on the importance of manufacturing in providing the basis for a balanced economy. The term High Value Manufacturing (HVM) has been used in the UK to describe manufacturing based industries with a high R&D content and therefore which in turn will support knowledge based job creation into the future. The UK Government has supported the development of a network of manufacturing research centres aimed at providing a step change in research and development activity and impact termed the HVM Catapult. The Advanced Forming Research Centre (AFRC) within the University of Strathclyde is a founder member of the HVM Catapult, with a focus on metal forming and forging technologies.

To outsiders however, forming and forging are established technologies employed within traditional, and in many cases declining, manufacturing environments whose roots can be traced back to the industrial revolution and beyond. It is not surprising, therefore, that the position of metal deformation technologies within the HVM taxonomy is sometimes questioned. This paper aims to address the common arguments which are used to question the position of metal forming and forging within HVM at a general level, and through examples of ongoing work themes with the AFRC.     

Fabrication of hybrid micro/nano-textured surfaces using rotary ultrasonic machining with one-point diamond tool

A novel rotary ultrasonic texturing (RUT) technique is proposed to fabricate hybrid periodic micro/nano-textures on flat surfaces. Different from conventional rotary ultrasonic machining, a tailored one-point diamond tool was manufactured and employed for RUT on surfaces of electroless nickel–phosphorus (Ni–P) plating. A one-dimensional longitudinal-vibration mode is used. The combined effect of ultrasonic vibration, rotation and feed motion leads to high-frequency periodic change of cutting edge׳s motion, which is the basic principle for the RUT process. Therefore, to accurately predict and control the texturing process, the cutting locus is firstly mathematically calculated. Hybrid periodic micro/nano-textures comprising linear grooves at the micrometer scale and sinusoidal grooves at the micrometer or nanometer scale were successfully fabricated on machined surfaces, which are in compliance with the results of the mathematical calculations. Different types of surface textures were generated by changing machining conditions. The surface generation mechanism of RUT is illustrated and discussed by analyzing the surface textural features, the cutting locus and the tool tip׳s geometry, including various tool faces, cutting edges, and the cutting corner. The requirements for RUT technique are concluded.     

Gaseous reduction of ultrafine metallurgical dust in rotary furnace

A laboratory scale rotary furnace has been developed for gaseous reduction of ultrafine metallurgical dusts to produce iron, zinc and other metal resources at submelting point temperatures. The kinetics of this process is much higher than say static or moving bed systems. By way of example, using dust with 38%Fe and 10%Zn, a 17?min treatment at 900°C produces an iron product of ～92%Fe and a zinc product of ～86%Zn.     

Important Parameters for the Manufacture of Slow-Release Matrix Pellets With an Aqueous Dispersion of Quaternary Poly(meth)acrylates in the Rotary Fluidized Bed

ABSTRACT

The manufacture of slow-release matrix pellets with an aqueous dispersion of quaternary poly(meth)acrylates was investigated in the rotary fluidized bed. By considering the moisture content of the fluidized bed to be the key process parameter, it was measured on-line throughout the whole manufacturing process. A specially designed sampling device opened new ways to apply NIR spectrometry in laboratory scale processes. It was shown that reproducibly improved pellet properties can be achieved by reproducing the moisture content of the (rotary) fluidized bed. Moisture plateaus proved to be a suitable way to optimize the sphericity of the pellets. Premoisturizing was found to be a very effective tool to achieve slow-release dissolution of the model drug theophylline.     

滚切剪的剪切力计算

滚切剪在中厚板生产线上发挥重要的作用,准确地计算滚切剪剪切力有助于其结构合理设计。但是经过对国内外滚切剪剪切力的计算公式的详细分析,这些计算公式得出的剪切力与实际的剪切力存在较大差异。根据滚切剪的工作过程特点,推导出更接近实际的剪切力计算公式。经实验证明此公式得出的结果与实际相符。     

回转窑密封结构的改进

密封装置对烧成系统的影响大致体现在对产量、热耗、电耗、污染和工艺的稳定操作等方面。就目前使用在水泥、冶金、化工等行业中的回转窑密封装置的各种型式进行了分析和比较,针对回转窑特点及密封装置的使用情况,对其结构进行了改进,选择一种好的密封装置一复合柔性密封,它能很好地适应回转窑端部的复杂运动,耐磨耐高温,有效地消除回转窑轴向、径向和环向间隙,实现了无间隙密封。