机械加工工艺危险性控制研究

机械安全是制造业赖以生存和发展的基础,涉及到国民经济各个部门和人民的安全与健康。为了有效地控制机械加工工艺的危险性,防止机械事故发生,减少人员伤亡和财产损失,运用事故统计方法,对我国机械加工行业各类生产事故进行统计分析,从不同伤害形式的角度出发,将机械伤害事故类型从绞伤、碾压伤害、夹挤伤害等方面进行研究,重点以锻工、车工、铣工、钳工等11种常见加工工艺为研究对象,分析其操作过程中发生的事故原因和事故类型,得出我国机械加工行业事故发生规律和各加工工艺危险性的大小。与以往机械伤害事故类型统计不同,本文将机械伤害从不同工种和不同伤害形式进行分类统计,更能体现机械加工事故伤害特点,对加强我国机械加工行业的安全生产管理有一定的参考意义。     

Lead and polycyclic aromatic hydrocarbons (PAHs) in surface soil from day care centres in the city of Bergen, Norway

Surface soil (0-2cm) quality in 87 day care centres in the city of Bergen, Norway has been studied. Approximately 45% of the day care centres contained Pb and PAH values above recommended action levels. There are clear variations between different areas of the city. The old central part of the city hosts most of the contaminated day care centres. In suburban areas most of the day care centres have Pb and PAH concentrations below action levels. City fires, gas work emission, lead-based paint, and traffic are probably important anthropogenic contamination sources, together with uncontrolled transportation of soil from contaminated to clean areas. Geological or other natural sources are probably not an important contributor to the high levels of lead and PAH.     

Electrochemical machining characteristics and resulting surface quality of the nickel-base single-crystalline material LEK94

Nickel-base single-crystalline materials such as LEK94 possess excellent thermo-mechanical properties at high temperatures combined with low density compared to similar single-crystalline materials used in aero engines. Since the components of aero engines have to fulfil demanding safety standards, the machining of the material used for these components must result in a high geometrical accuracy in addition to a high surface quality. These requirements can be achieved by electrochemical and precise electrochemical machining (ECM/PECM). In order to identify proper machining parameters for PECM the electrochemical characteristics dependent on the microstructure and the chemical homogeneity of LEK94 are investigated in this contribution. The current density was found to be the major machining parameter affecting the surface quality of LEK94. It depends on the size of the machining-gap, the applied voltage and the electrical conductivity of the electrolyte used. Low current densities yield inhomogeneous electrochemical dissolution of different microstructural areas of the material and lead to rough surfaces. High surface qualities can be achieved by employing homogenous electrochemical dissolution, which can be undertaken by high current densities. Furthermore, a special electrode was developed for the improvement of the quality of side-gap machined surfaces.     

机械加工振动公害控制

根据多年从事机械、环保科研设计及工厂的实践 ,仔细分析了机械加工振动污染源对操作者及周围居民的危害。并提出了对其所造成的公害进行适应控制的基本措施。     

涂装循环水、机加工乳化液处理站的运行技术

五羊－本田摩托（广州）有限公司生产基地有年产40万台发动机和摩托车外观件的生产车间，其中，机加工乳化液和涂装循环水是由污水处理站处理的，通过工艺流程的改造利用及加强制度管理，使处理站平衡高效运行，出水达到了广州市一级排放标准。     

A survey of rainstorms as weather hazards in southern Nigeria

This paper examines the role played by winds as a weather hazard in urban centres of southern Nigeria. It is observed that strong winds associated with rainstorms at the beginning of the rainy season are a threat to urban centres as they directly affect buildings and infrastructure. Wind hazards also have indirect social and economic consequences on the communities affected. Much of the damage done to buildings is as a result of inappropriate building designs that have not taken into consideration the wind environment. An inventory of reports of damage caused by winds during the first half of 1995 showed that different towns in eight states were affected. These incidences occurred mainly at the beginning of the rainy season when strong winds are associated with linesqualls. Although wind related hazards have not been adequately acknowledged as an environmental problem that needs to be properly addressed in Nigeria, as in the case of flooding, results have shown that it is a problem that requires government intervention in view of global climate change and consequent extreme weather events. Wind hazard awareness and preparedness as integral aspects of development policy and planning of the environment is therefore needed in West African countries where linesqualls are very significant rain producers.     

A holistic approach to achieving energy efficiency for interoperable machining systems

In the twenty-first century, the continuous demand in energy resource has put sustainability on the agenda of many businesses. This is particularly true for the manufacturing industry, where a large amount of energy is consumed to sustain daily operations. This paper studies energy-efficient computer numerical control machining systems. To achieve overall energy efficiency in machining systems, several activities are involved as in the proposed research framework of a global energy-efficient machining system (GEMS). These activities are described as modules, i.e. energy monitoring, energy analysis and optimisation, energy-based optimal control and energy-enriched database. In a GEMS, one critical issue is data interoperability. Seamless data sharing enables collaboration for improving energy efficiency. Using the EXPRESS language, energy data models are proposed for each module in the GEMS, and integrated with the existing STEP-NC (STandard for Exchange of Produce-compliant Numerical Control) standards. Two case studies are presented to demonstrate how the proposed data models may be used. One study updates an existing production file to include general energy information for auditing or reviewing purposes; the other study maintains machine tool energy profiles in a database. Many other energy-efficient activities, e.g. online energy optimisation, can be realised with the proposed data models. The present study proved that interoperable energy information can enhance the energy-efficient performance of a machining system.     

Computational energy estimation tools for machining operations during preliminary design

The aim of this paper is to develop computational machining energy estimation tools during the early design stage of product development. In the preliminary or embodiment design, a product's shape and materials are determined. At this stage, it is crucial for a designer to be able to compare alternative designs and materials based on many different criteria, such as cost, functionality, energy, etc. Automated tools for estimating energy consumption that could later be used to integrate with CAD/CAM systems are in demand. This study presents computational tools for estimating the energy consumption of machining operations during the early design phase. The computational tools utilize a preliminary computer representation of a product (CAD model), its material and candidate machining operations to automatically analyse and estimate a range of energy consumption during machining operations. Detailed steps for computing turning and milling energy consumption are presented. Case studies of both parts and assemblies were conducted to test the validity of the tools and to evaluate the performance of the tools. Environmental impacts such as carbon weight will also be estimated. The computation tools will assist users with little knowledge about energy computations to estimate energy consumption during the design stage. Such energy estimation can be used to redesign parts and assemblies, leading to the development of products with reduced machining energy. The computation tools are part of a larger research on estimating energy consumption throughout a product's life cycle.     

Effect of fluid concentration in titanium machining with an atomization-based cutting fluid (ACF) spray system

The aim of this work is to investigate the effect of metal-working fluid (MWF) concentration on the machining responses including tool life and wear, cutting force, friction coefficient, chip morphology, and surface roughness during the machining of titanium with the use of the ACF spray system. Five different concentrations from 5 to 15% of a water-soluble metalworking fluid (MWF) were applied during turning of a titanium alloy, Ti–6Al–4V. The thermo-physical properties such as viscosity, surface tension and thermal conductivity of these concentrations were also measured. The test results demonstrate that the tool life first extends with the increase in MWF concentration and then drops with further increase. At low concentration (e.g., 5%), a lack of the lubrication effect causes to increase in a higher friction at the tool–chip interface resulting in severe chipping and tool nose/flank wear within a short machining time. On the other hand, at high concentration, the cooling effect is less. This increases cutting temperature and a faster thermal softening/chipping/notching of the tool material and higher friction at the tool–chip–workpiece interaction zones resulting in early tool failure. A good balance between the cooling and the lubrication effects seems to be found at the 10% MWF concentration as it offers the best machining performance. However, machining with flood coolant is observed to perform the best in the range of 5–7%.     

High speed ball nose end milling of hardened AISI A2 tool steel with PCBN and coated carbide tools

High speed machining (HSM) of tool steels in their hardened state is emerging as an attractive approach for the mold and die industry due to its potential for significant cost savings and productivity improvement. An experimental study was conducted to investigate the tool wear mechanism and surface integrity in high speed ball nose end milling of hardened AISI A2 tool steel using coated tungsten carbide and polycrystalline cubic boron nitride (PCBN) tools. It is found that coated carbide tools can only be used at low speed (120 m/min) while high content PCBN tools are suitable for HSM range (470 m/min). PCBN tools produce a damage free workpiece with better surface finish and less work hardening. Despite the higher tool cost, HSM with PCBN tools lead to reduction in both total cost and production time per part.