柔性加工中高功率激光束空间变换研究

在国民经济中占有重要地位的汽车工业中，对于大型覆盖件模具的表面强化处理，最常见的是火焰淬火。火焰淬火对操作人员的要求高，可控性差，效果不理想，但是由于一直没有适合的方法，目前也只能继续使用。而激光表面强化技术结合柔性加工系统正是解决这类问题的新途径。传统的激光表面强化是采用把激光束离焦后进行扫描的方式，这种方法不能充分利用激光功率密度，而且往往要用转镜或振镜形成条形光斑来加快处理速度，这就需要复杂的机械结构，而且产生难以避免的重叠回火。我们提出一种新方法，利用二元光学元件来获得一种新型的周期光强分布，实现其在高功率激光系统中的应用，并设计成为集成到柔性加工系统中的组成部分，能够完成对大、中型模具表面的激光强化处理。本论文的工作主要是有关激光柔性加工系统中的光束传输及变换子系统，不仅包括理论设计、加工制作，同时还包括把该子系统有效的结合到整个系统中。本研究工作广泛涉及激光理论，光束变换和光纤传输，系统中的模块化集成应用技术，金属材料的特殊分布光强表面改性试验研究等等，是跨学科的交叉研究工作。在本论文中，重点是二元光学元件的设计方法的选择、计算机辅助设计的实现、二元光学元件的制作和在高功率激光传输中的应用，以及特殊光强分布应用于金属表面改性中的相关工作。通过把二元光学元件引入到高功率激光加工中，对出现的新现象给出一定的预测和分析，并获得了良好的强化结果，最终实现了系统的集成化，并具有实际生产所要求的可靠性和灵活性。本论文共分六章，主要包括两方面的内容。第一章为绪论，第六章为结论。第一方面内容在第二章到第四章中说明，是用于高功率激光应用中的二元光学元件的原理、设计和制作。第二方面的内容在第五章中，是关于应用前面设计制作的二元光学元件，在实际的金属材料表面处理中的实验研究，给出了相关试验结果。

Introduction: improving manufacturing performance through technology diffusion, implementation and management

The role of technology management in achieving improved manufacturing performance has been receiving increased attention as enterprises are becoming more exposed to competition from around the world. In the modern market for manufactured goods the demand is now for more product variety, better quality, shorter delivery and greater flexibility, while the financial and environmental cost of resources has become an urgent concern to manufacturing managers. This issue of the International Journal of Technology Management addresses the question of how the diffusion, implementation and management of technology can improve the performance of manufacturing industries. The authors come from a large number of different countries and their contributions cover a wide range of topics within this general theme. Some papers are conceptual, others report on research carried out in a range of different industries including steel production, iron founding, electronics, robotics, machinery, precision engineering, metal working and motor manufacture. In some cases they describe situations in specific countries. Several are based on presentations made at the UK Operations Management Association's Sixth International Conference held at Aston University at which the conference theme was 'Achieving Competitive Edge: Getting Ahead Through Technology and People'. The first two papers deal with questions of advanced manufacturing technology implementation and management. Firstly Beatty describes a three year longitudinal field study carried out in ten Canadian manufacturing companies using CADICAM and CIM systems. Her findings relate to speed of implementation, choice of system type, the role of individuals in implementation, organization and job design. This is followed by a paper by Bessant in which he argues that a more a strategic approach should be taken towards the management of technology in the 1990s and beyond. Also considered in this paper are the capabilities necessary in order to deploy advanced manufacturing technology as a strategic resource and the way such capabilities might be developed within the firm. These two papers, which deal largely with the implementation of hardware, are supplemented by Samson and Sohal's contribution in which they argue that a much wider perspective should be adopted based on a new approach to manufacturing strategy formulation. Technology transfer is the topic of the following two papers. Pohlen again takes the case of advanced manufacturing technology and reports on his research which considers the factors contributing to successful realisation of AMT transfer. The paper by Lee then provides a more detailed account of technology transfer in the foundry industry. Using a case study based on a firm which has implemented a number of transferred innovations a model is illustrated in which the 'performance gap' can be identified and closed. The diffusion of technology is addressed in the next two papers. In the first of these, by Lowe and Sim, the managerial technologies of 'Just in Time' and 'Manufacturing Resource Planning' (or MRP 11) are examined. A study is described from which a number of factors are found to influence the adoption process including, rate of diffusion and size. Dahlin then considers the case of a specific item of hardware technology, the industrial robot. Her paper reviews the history of robot diffusion since the early 1960s and then tries to predict how the industry will develop in the future. The following two papers deal with the future of manufacturing in a more general sense. The future implementation of advanced manufacturing technology is the subject explored by de Haan and Peters who describe the results of their Dutch Delphi forecasting study conducted among a panel of experts including scientists, consultants, users and suppliers of AMT. Busby and Fan then consider a type of organisational model, 'the extended manufacturing enterprise', which would represent a distinct alternative pure market-led and command structures by exploiting the shared knowledge of suppliers and customers. The three country-based papers consider some strategic issues relating manufacturing technology. In a paper based on investigations conducted in China He, Liff and Steward report their findings from strategy analyses carried out in the steel and watch industries with a view to assessing technology needs and organizational change requirements. This is followed by Tang and Nam's paper which examines the case of machinery industry in Korea and its emerging importance as a key sector in the Korean economy. In his paper which focuses on Venezuela, Ernst then considers the particular problem of how this country can address the problem of falling oil revenues. He sees manufacturing as being an important contributor to Venezuela's future economy and proposes a means whereby government and private enterprise can co-operate in development of the manufacturing sector. The last six papers all deal with specific topics relating to the management manufacturing. Firstly Youssef looks at the question of manufacturing flexibility, introducing and testing a conceptual model that relates computer based technologies flexibility. Dangerfield's paper which follows is based on research conducted in the steel industry. He considers the question of scale and proposes a modelling approach determining the plant configuration necessary to meet market demand. Engstrom presents the results of a detailed investigation into the need for reorganising material flow where group assembly of products has been adopted. Sherwood, Guerrier and Dale then report the findings of a study into the effectiveness of Quality Circle implementation. Stillwagon and Burns, consider how manufacturing competitiveness can be improved individual firms by describing how the application of 'human performance engineering' can be used to motivate individual performance as well as to integrate organizational goals. Finally Sohal, Lewis and Samson describe, using a case study example, how just-in-time control can be applied within the context of computer numerically controlled flexible machining lines. The papers in this issue of the International Journal of Technology Management cover a wide range of topics relating to the general question of improving manufacturing performance through the dissemination, implementation and management of technology. Although they differ markedly in content and approach, they have the collective aim addressing the concepts, principles and practices which provide a better understanding the technology of manufacturing and assist in achieving and maintaining a competitive edge.

A Compliant Mechanism Kit with Flexible Beams and Connectors

We present the concept, prototypes, and an optimal design method for a compliant mechanism kit as a parallel to the kits available for rigid-body mechanisms. The kit consists of flexible beams and connectors that can be easily hand-assembled using snap fits. It enables users, using their creativity and mechanics intuition, to quickly realize a compliant mechanism. The mechanisms assembled in this manner accurately capture the essential behavior of the topology, shape, size and material aspects and thereby can lead the way for a real compliant mechanism for practical use. Also described in this paper are the design of the connector to which flexible beams can be added in eight different directions; and prototyping of the spring steel connectors as well as beams using wire-cut electro discharge machining. It is noted in this paper that the concept of the kit also resolves a discrepancy in the finite element (FE) modeling of beam-based compliant mechanisms. The discrepancy arises when two or more beams are joining at one point and thus leading to increased stiffness. After resolving this discrepancy, this work extends the topology optimization to automatically generate designs that can be assembled with the kit. Thus, the kit and the accompanying analysis and optimal synthesis procedures comprise a self-contained educational as well as a research and pragmatic toolset for compliant mechanisms. The paper also illustrates how human creativity finds new ways of using the kit beyond the original intended use and how it is useful even for a novice to design compliant mechanisms.

Preparing for flexible delivery in industry : learners and their workplaces

This thesis examines the learning preferences and learning strategies of apprentices, and the contexts within which they learn in their workplaces. Since the end of the 1980s Australian vocational education and training (VET) structures and processes have undergone radical change in attempts to develop skills in the workforce that will ensure enterprise, national, and international competitiveness. A major strategy in the national reforms has been the encouragement of flexible delivery as a means through which workplace-based learning can be accessed by a larger number of workers in ways that are cost-efficient, and that reduce the amount of time that workers spend away from their jobs. Although flexible delivery has been championed by governments and industry alike, there has been little attempt to identify the preparedness of either learners or their workplaces for the demands of flexible learning. The thesis examines the economic context for these changes to VET, and also examines the literature available on workplace learning. Additionally, the thesis examines the conceptualisations of flexible delivery that are available in the literature, pointing to the possibility that the wide range of meanings associated with the term ‘flexible delivery’ may result in quite different practices and expectations. The thesis also examines the literature on independent learning and self-directed learning, and explores the concept of ‘client-focused’ flexible delivery. The study of learner preferences uses data collected from apprentices over a period of some years, in the four occupational areas commanding the highest number of apprentices in Australia. These occupational areas are Metals and Machining, Building, Electrical, and Hairdressing. These data on learning preferences are collected using the commercially available Canfield Learning Styles Inventory (CLSI). The data from the sample of 389 apprentices are analysed statistically through analyses of variance, and indicate that variables such as age, gender, and occupational area are related to learning preferences. Apprentices are shown by this analysis to prefer structured programs of instruction that are instructor-led, and to not have a high preference for independent learning or the development of their own learning goals. Additionally, they are shown to have very low preferences for learning through reading, preferring instead to learn through direct hands-on experience. While these characteristics are largely common among the four occupational groups, the Hairdressing apprentices are shown to have a slightly higher preference for independent learning and goal setting. Females are shown to have a higher preference than males for learning qualitative material through reading. Interestingly, the younger apprentices are shown to have a higher preference than the older ones for self-directed learning. Some possibilities for that finding are discussed. The research also shows that the learning preferences displayed by different groups of apprentices in any one program are much the same over time, providing some confidence that data generated from one group of apprentices can be used to make instructional decisions for future groups in the same program. The data are also factor analysed to indicate three major factors underlying apprentice learning preferences. The first factor indicates a Verbal–Non-verbal preference factor, with apprentices clearly preferring to learn through non-verbal means. A second factor is described as Structure–Content, with apprentices showing a preference for learning from structured programs in a structured environment. A third factor, Self-directed–Social preference, indicates apprentices preferring to learn through socially mediated presentations and contexts rather than through more independent forms of learning. Qualitative data are also generated through interviewing eight apprentices, and focusing on the learning strategies they employ while constructing knowledge in the workplace. That component of the research uses a modification of the Marland, Patching and Putt (1992a, 1992b) stimulated recall technique, and a set of learning strategies derived from the work of O’Malley and Chamot (1990) and Billett (1996a). The eight apprentices are drawn from the Metals and Machining, Electrical, and Hairdressing trades. The findings indicate that the learning strategies most often used by apprentices in the workplace are those associated with the construction of knowledge that is structured and provided by the instructor or learning program, and those that include social mediation of learning. Additionally, the strategies associated with demonstration and hands-on practice are most favoured. The qualitative data are confirmatory of the quantitative data. The research also indicates, through the apprentice interviews, that support for apprentice’s learning in their workplace is typically unplanned and haphazard. Their experience was sometimes characterised by a reluctance on the part of the workplace to acknowledge learning needs such as trialling and practice of new knowledge, or pro-actively seeking understanding from other more skilled workers. The learning preferences and learning strategies findings for apprentices, coupled with the findings of typically poor or unplanned support in the workplace, indicate that effective flexible delivery of training to apprentices in the workplace provides a number of challenges. These challenges, it is argued, demand strategies to be developed and implemented to prepare both learners and workplaces for effective engagement with flexible delivery. Using as a theoretical framework Kember’s (1995) two-dimensional model of open learning for adults, the thesis integrates the findings into a proposed two-dimensional model of learner and workplace preparedness for flexible delivery. The model provides for a Learner Development Space, a Workplace Development Space, and a Strategy Space. Within the Learner Development Space, focuses for the development of learner preparedness are identified in terms of self-directed learning, skills developments, and effective participation in a community of practice. Focuses for workplace development identified in the Workplace Development Space are those associated with development of training policies, training structures, and trainer skills and abilities. The Strategy Space then provides detail of seventy-nine specific strategies developed to enhance learner and workplace preparedness within each of the focuses identified.

Responsive fixture design using dynamic product inspection and monitoring technologies for the precision machining of large-scale aerospace parts

When machining a large-scale aerospace part, the part is normally located and clamped firmly until a set of features are machined. When the part is released, its size and shape may deform beyond the tolerance limits due to stress release. This paper presents the design of a new fixing method and flexible fixtures that would automatically respond to workpiece deformation during machining. Deformation is inspected and monitored on-line, and part location and orientation can be adjusted timely to ensure follow-up operations are carried out under low stress and with respect to the related datum defined in the design models.

Multi-threaded parallel numerical modelling of femtosecond pulse propagation in laser machining

Femtosecond laser microfabrication has emerged over the last decade as a 3D flexible technology in photonics. Numerical simulations provide an important insight into spatial and temporal beam and pulse shaping during the course of extremely intricate nonlinear propagation (see e.g. [1,2]). Electromagnetics of such propagation is typically described in the form of the generalized Non-Linear Schrdinger Equation (NLSE) coupled with Drude model for plasma [3]. In this paper we consider a multi-threaded parallel numerical solution for a specific model which describes femtosecond laser pulse propagation in transparent media [4, 5]. However our approach can be extended to similar models. The numerical code is implemented in NVIDIA Graphics Processing Unit (GPU) which provides an effitient hardware platform for multi-threded computing. We compare the performance of the described below parallel code implementated for GPU using CUDA programming interface [3] with a serial CPU version used in our previous papers [4,5]. © 2011 IEEE.