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钢筋 校直机 设计

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钢筋校直机的设计,钢筋,校直机,设计

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本科生毕业论文（设计）选题审批表毕业论文（设计）题目钢筋校直机的设计指 导 教 师职 称学生具备条件修完人才培养方案及要求的课程选题完成形式开题报告内 容 简 要：钢筋校直机主要是通过电动机带动V带轮传递到主轴，主轴带动送料，输送钢筋到校直机构进行校直。本设计采用的是轮辊式校直方法。结构简单，工人操作起来容易。生产成本低，适用于各种建筑工地。系主任签字： 年 月 日 院长签字： 年 月 日2选题的依据及意义（包括课题的理论价值和实践价值；国内外的研究概况等）：21世纪是一个技术创新的时代，随着我国经济建设的高速发展，钢筋混凝土结构与设计概念得到不断创新，高性能材料的开发应用使预应力混凝土技术获得高速而广泛的发展，在钢筋混凝土中，钢筋是不可缺少的构架材料，而钢筋的加工和成型直接影响到钢筋混凝土结构的强度、造价、工程质量以及施工进度。所以，钢筋加工机械是建筑施工中不可缺少的机械设备。在实际生产中，钢筋全是以圆盘状出现的，这样生产者方便运输，但工地施工时所需要的钢筋都为直钢筋，这时钢筋校直机的作用是不可缺少的，它将盘状钢筋校直成为直钢筋用于建筑中。钢筋技术推广的社会和经济效益十分显著，因此高强钢筋得到了广泛的应用。欧美等工业发达国家对混凝土结构中钢筋的性能要求较高，多采用400到500MPa可焊钢筋，其实物的质量高于标准规定。盘卷供料的钢筋需要校直后才能使用，目前国内还没有能满足校直性能较高的钢筋校直机，国内钢筋校直机现有的校直强度都在350MPa左右。本课题研究内容（1）校直系统的设计我设计的钢筋校直机的校直构，采用的是轮辊式，我的轮辊采用的是相互交错分布，对钢筋施加交变应力，使原来的弯曲抵消。（2）传动系统的设计传动系统采用的是V带传动，电机通过一个二级V带传递到钢筋校直机的主轴上，主轴转动带动送料轮，达到输送钢筋到校直机构的作用。本课题研究方案首先进行设计资料的收集与整理，对设计做初步理解。然后结合所收集的资料，找出合理的设计方案，找出资料中存在的问题，进行改良，使钢筋校直机更加合理化。根据设计要求，选择电动机的型号功率，设计合理的校直系统，传动装置，机架的设计。研究的创新之处结构简单，容易操作，检修方便，电动机功率低，能耗也低。 研究过程(含完成期限)第5周查阅资料，拟订课题第6周查阅相关钢筋校直机的设计资料，并进行概述和文献综合。第7-9周完成钢筋校直机的设计计算并绘制装配图。第10-12周完成设计并绘制装配图和部分零件图。第13周完成所有的图纸并进一步修改。第14-15周在以上基础上完成毕业设计说明书一篇。第16周修改设计，并定稿。第17周答辩，提交相关材料，结束设计。指导教师意见 指导教师签名：年 月 日教研室意见 教研室主任签名：年 月 日院系意见 主管领导签名： 年 月 日本科生毕业设计开题报告题 目 钢筋校直机的设计 学院名称 专业名称 年 级 学生姓名 学 号 指导教师 职 称 年 月 日科技译文题 目 降低商用飞机的直接维护费用的方法 学院名称 专业名称 年 级 学生姓名 学 号 降低商用飞机的直接维护费用的方法商用飞机的维护活动是飞机耐飞性能的一个必要组成部分。飞机维护是令飞机回复到可使用状态下的一个上木。它包括维护、修理、彻底检查、检验和状态测定。它可以分为两种类型。修正的维护。这些活动，即由提供对于某一已知的或疑似的故障及（或）缺陷的方案，来是失败的结果回复到一种令人满意的情况。修正的维护大体上可分为过失确认、过失隔离、拆卸、替换、重新装配、对准或者调整，以及测试。这一种维护的类型即是不预定的维护，而且受益于诊断的使用以减轻在维护资源方面的负担。预防的维护。这些活动，即由系统检验、探测、疲劳项目的替换、调整、口径测定，以及清洁等，来使之保持在可使用状态。在飞机和仪器的整个寿命中，它以一种规定的形式实行。因此，它也被成做预定的维护。维护通常的目标是，在一家航空公司需要维修飞机时，能够以最低的费用提供一套完整的维护服务。现在商用飞机的维护费用对飞机费用的所有权起一个重要作用。维护费用一般占与飞机操作相关费用的10%-20%（Maple,2001）。直接的维护费用（DMC）被定义为，用于维护一个飞机或相关仪器所需的劳动力费用和材料费用（ATA，国际航空运输协会和ICCAIA，1992）。DMC不包括劳动和物质的开支，如行政、监督、使用工具工作、测试仪器、设备、记录及保存等活动的费用（Knotts,1999）。航空公司通常会寻求维护费用的保证，如果DMC超过约定的指定水平，飞机制造者将招致财政上的处罚。我们的研究目标是找出一些为商用飞机减少DMC的方法。本论文首先分析了影响DMC的主要因素，然后讨论了可以减少DMC的一些方法。DMC的主要影响因素依照定义，DMC的公式是：DMC=（+）LR+MC,其中，是指飞机维护人员在飞机上的工作时间；是指飞机维护人员不在飞机上的凌夷部分工作时间；LR是指劳动费用；MC是指材料的费用。影响DMC的因素可以依下列各项分类。设计因素可靠性和可维护性（R&M）是飞机的固有价值。它只能由设计决定。虽然像经过高度训练的人和一个应答的补给系统这样的其他因素，也能使时间限定在一个绝对的最小量中，但是只有国有的R&M才能决定这一最小量。即使改良训练或技术支持也不能够有效的弥补因一架拙劣设计（根据R&M）的商用飞机在可用性方面所造成的损失。将支持飞机飞行的费用减少到最小，最大限度的提高籍由最好设计所生产出的产品的可用性，使之可靠并且可维护。对于商用飞机整个寿命期所花费用来说，大概有70%-80%的费用是由设计阶段来决定的。过失诊断效率系统和技术的复杂性逐渐增加加大了即使、有效的过失诊断的困难。由此成为系统可维护性的问题因素。而且，从减少时间周期和费用方面来看，无效的过失诊断可能会很贵。因为“没有发现错误（NFF）”的情形会对维护费用产生很大的影响。现代系统的设计经历了40%或者更高的仪器错误消除率。这些错误是有歧义的、劳动密集型的测试程序所造成的。航空电子学和电气科学方面的不可预定维护费用占民用飞机DMC的18%，40%与仪器错误消除相关的被归类为NFF。在1992年，一项对部件转移的审计突出了英国空中航线的机群每平均有8000项被转移走。纵观所有的工作室，其所有部件中的14%，被发现有NFF。一台航空电子学仪器平均会产生出30%的NFF。在财政上来看，若是考虑到直接和间接费用，那么 这就等于是每年在NFF上的开支总共就需要两千万英镑（Knotts,1999）。 与组织相关的可变因素这些可变因素跟一家特定的航空公司有关。他们包括飞机机群的规模和共通性，飞机的龄和使用率，维修标准和计划，检查间隔的频率，承做转包工作的水平，会计方法，通货波动，地方劳动力费用，消耗品的可循环率，以及材料价格（Maple,2001）。环境因素这些因素依赖于操作员的位置。举例来说，它是沙漠的环境或者海洋性气候。再举例来说，由于沙和盐的腐蚀，将会对引擎的维护仪器产生重要影响。在本论文中，我们忽略了某一特定的航空公司这一因素，再讨论了设计和过失诊断的影响。一项关于R&M在自由操作期间的维护的新观念在传统方式下，R&M设计的探讨是建立在失败基础上的。这种探讨认为，在仪器设备的整个寿命期间，偶然的失败是不可避免的，并且这种失败将导致许多不可预定的维护工作在日常工作中产生。由于不可预定的维护是不能被计划出来的，所以，从维护费用方面来说，不可预定的维护可能是做昂贵的。最近的研究表明，给大型的商用喷气式飞机每一年每一架飞机的不可预定维护费用在一百万英镑左右（Kumar et al.,1999a）。为了减少费用，一个以维护的自由操作时期（MFOP）为基础的新方法已经发展起来了。MFOP被定义为，仪器设备在没有任何维护措施，也没有因系统错误或限制导致的操作员的约束行为就能够执行现已指定的任务。这个操作的时间段就是MFOP。（Hockley,1998）。在MFOP的时期，籍由设计，任何的维护的必要性应该是保持在一个最小量。并且，仪器设备仅仅允许执行如飞行服务这样的在计划内的最低限度维护。一个MFOP之后，紧接着就是一个维护恢复时期（MRP）。MRP被定义为是一段被限定了的时间。在此期间，需要完成适当的安排和正确的维护，使系统回复到满负荷状态，这样才能够完成接下来的MFOP。由于它们必须包括不同的维护活动，所以不是所有的MRP将会是相同的期间，因为可替换的单位（LRU）个体排成一行，比如那些使用寿命期满的，需要做一些彻底检查，而且不用维护或正确的检验。另外，我们会做出正确的维护来是那些错误的系统回复到满负荷状态（Hockley,1998）。MFOP是一个担保时期的延长。操作员正在考虑在系统的整个使用寿命期间扩充这一概念。产品供应商或者制造商需要作出如下保证，即在指定的一段操作时间内，因为有预先社顶的质量保证登记，不可预定的维护工作是不需要的。这个质量由自由操作时期的存留能力时间（MFOPS）按比例来决定（Kumar et al.,1999b）。MFOPS被定义为某一项目在MFOP的期间存留下来的可能性。对于商用飞机的MFOP，当考虑到R&M的设计时，会有两种减少DMC的方法。飞机的固有可靠性可以得到句到的改变。更高的可靠性可以减低错误的次数，因此，飞机可靠性是有工时和必需的物质决定的，DMC就会相应减低。完成飞机的MFOPS，这就意味着任意的失败应该在MFOP期间被根除。传统的文化认为，错误不仅是不可避免的，而且，从某种角度来看，它是可以接受的，这应该放弃。一种细节详细的知识环境和使用经验，以及对于为什么失败的非常机制下的理解，会被灌输给发展程序员。许多技术或者解决办法都以一条更积极的方式设计其可靠性，不给失败予任何机会。这些技术可以有一种缓慢的设计变化过程，即选择不同的成分，生成一个改进的程序，或者，可以有一种更快速的设计变化过程。完成最适宜的维护计划。很明显，飞机所有的系统在某一时间都需要做一些维护工作，而且，这些工作是在MRP计划中的。MFOP延期事实上是对MRP所有正确的 维护，因此，不可预定的维护部分其实被转化成了更多的计划中的维护，它是建立在有更高可靠性的仪器上的，这才能产生更高的可靠性能。MRP的价值与效率的关系及其平衡的设置建立并支持最好的整个MFOP系统。其实际价值可以在设计期间的系统工程学中的经贸学和方法学来体现。这些能减少维护计划中一定量的百分比。而后勤支援可能被集中到一个特定的飞机操作地点。紧急事故处理资源可能会重新分配到几顶的工作中。这样，MFOP就能为操作者带来灵活性。此时，操作者可以在一定范围内执行组织和正确的维护工作。然后，DMC就会下降，这是因为用于报废飞机的劳动力和材料减少了。举例来说，如今一架飞机在整天寿命期中的直线型维护占所有维护劳动力的50%（Maple,2001），由MFOP设计出的飞机常规工作将会减少到最小量。过失诊断过失诊断的进程一般可氛围感应信号、提取特征以及连续的诊断论证。当对现代的商用飞机诊断失败时，大部分感应信号和提取的特征程序由于感应器、动力学实验和信号检测这些技术的发展，可以是自动完成的。这样，诊断论证（即，怎样找出错误的根源）就成为了决定过失诊断的效率的主要因素。根据过失诊断的观念，飞机是一个复杂的系统。它的结构是多样的阶层建筑结构，它包含有许多次级系统，比如飞机主结构、引擎、自动飞行系统、起落架、联络系统、液压和飞行系统。每个次级系统是由更低级别的次级系统或者次级单元构成的。并且，这些次级系统或次级单元之间通常是有联系的。由于飞机结构和功能的复杂性和多相性，飞机结构水平之间的联系是难以定义的。次级系统或次级单元的输入和输出之间的数量关系往往是无法测知或不正确的。很多技术领域中，先进的技术如机械化、电气化、计算机和自动机械控制，以及电子学都适用于现代的飞机。越来越多的电机械仪器已经用于飞机。这些仪器的机械和电子部分已经不仅整合了飞机的控制，还整合了飞机的功能和结构。飞机的过失诊断囊括了各种学科的知识。我们从以上的议题中总结出了商用飞机的诊断论证的困难性，而且很多时候，这需要有专家的参与。然而，我们需要的专家因为调换、疾病，以及雇佣关系的改变等原因，经常是不到位的。除此之外，很多技术领域已经应用于大型商用飞机，而且一个专家不再可能蚩尤所有现有的系统知识。发展一个包涵系统知识、专长和经验的过失诊断专家系统被视为一个定位困难的方法。这样不仅可以带来比人工更正确，更一致的结果，而且在某种程度上，它可以代替一个专家，使很多使用者可以轻易获得宝贵的专长，尤其适用于相对不熟练的职工和新来者。大部分的NFF将会被专家系统避免，如此一种有成本效益和及时的过失诊断将会帮助减少DMC。结论MFOP的观念已经作为面向未来所作出的一个大步骤被航空宇航工业认同。一些在较早时间所提出的关顶已应用于A340-600（Cini和Griffith,1999）。过失诊断专家系统已经应用于波音777的中央计算机维护系统。毫无疑问，它们能极大地减少DMC。Methods to reduce direct maintenance costs for commercial aircraftElectronic accessThe Emerald Research Register for this journal is available atThe current issue and full text archive of this journal is available at/0002-2667.htmIntroductionCommercial aircraft maintenance activities form an essential part of airworthiness. Aircraft maintenance is actions that can restore an item to a serviceable condition, and consist of servicing, repair, modification, overhaul, inspection and determination of condition. It can be classified into two types. Corrective maintenance. All actions performed as a result of failure to restore an item to a satisfactory condition by providing correction of a known or suspect malfunction and/or defect. Corrective maintenance in general consists of fault verification, fault isolation, disassembly, replacement, reassembly, alignment/adjustment, and test. This type of maintenance is known as unscheduled maintenance, and benefit from the use of diagnostics to ease the burden on the maintenance resource. Preventive maintenance. All actions performed at defined intervals to retain an item in a serviceable condition by systematic inspection, detection, replacement of wear out item, adjustment, calibration, cleaning etc. It is carried out at prescribed points in an aircraft and equipments life. It is also termed as scheduled maintenance. The common goal of maintenance is to provide a fully serviceable aircraft when it is required by an airline at minimum cost. For the present, maintenance costs of commercial aircraft make a significant contribution to an aircrafts cost of ownership. Maintenance costs typically account for 10-20 per cent of aircraft-related operating costs (Maple, 2001). Direct maintenance costs (DMC) is defined as the labor and material costs directly expended in performing maintenance of an aircraft or related equipment (ATA, IATA and ICCAIA, 1992). DMC do not include the labor and material expenditures, which contribute to activities such as administration, supervision, tooling , test equipment, facilities, record keeping etc. (Knotts, 1999). Airlines usually seek maintenance cost guarantees, where the aircraft manufacturer incurs financial penalties if DMC exceed agreed specified levels. The aim of our research is to find our some methods to reduce DMC for commercial aircraft. In the continuation, the paper first analyzes the key factors that influence DMC, then discusses some methods that could reduce DMC, and finally draws a conclusion.Key influence factors of DMCsAccording to the definition, the formula for DMC is DMC = ( +) LR + MCWhere is maintenance man hours off aircraft, LR is labor rate, and MC is material costs. The factors, which effect on DMC, can be categorized as follows.Design factorReliability and maintainability (R&M) is an inherent property of aircraft. It can be achieved only by design. Although other factors, such as highly trained people and a responsive supply system, can help keep down time to an absolute minimum, it is the inherent R&M that determines this minimum. Improving training or support cannot effectively compensate for the effect on availability of a poorly designed (in terms of R&M) commercial aircraft. Minimizing the cost to support an aircraft and maximizing the availability of that aircraft are best done by designing the product to be reliable and maintainable. R&M design has become an essential art of the development process of modern commercial aircraft life costs are determined during the design stage.Fault diagnosis efficiencyThe increasing complexity of systems and technology adds to the difficulty of effective and timely fault diagnosis, thus contributing to the problems of system maintainability. Moreover, ineffective fault diagnosis can be expensive in terms of down time and cost, with “no fault found (NFF)” situations contributing significantly to maintenance costs. Current system designs experience a 40 per cent, or higher, equipment false removal rate as a result of ambiguous and labor intensive test procedures. Avionics and electrical unscheduled maintenance accounts for 18 per cent of a civil aircrafts DMC, 40 per cent of related equipment removals are classified as NFF. In 1992, an audit of component removals highlighted an average of 8,000 items removed from British Airways fleet per month. A total of 14 per cent of components, across all workshops, were found to have NFF. Certain avionics equipment experienced 30 per cent NFF. Financially, considering direct and indirect costs, this equated to an annual NFF expenditure totaling $20 million (Knotts, 1999).Organization-related variablesThese variables are relative to a specific airline. They include fleet size and commonality, aircraft age and utilization, maintain standard and plan, frequency of check intervals level of subcontracting, accounting method, currency fluctuations over time, local labor rates, and material prices (Maple, 2001).Environmental factorsThese factors depend on the location of the operator. For example, it is a desert environment or a maritime climate. For example, corrosion due to sand salt will have a significant influence to engine maintenance equipment. Disregarding factors unique to a particular airline, impacts of design and fault diagnosis are discussed in this paper.A new concept of R&M design- maintenance free operating periodThe traditional approach pf R&M design, which is based on the meantime between failures (MTBF), acknowledge that random failures are inevitable throughout the equipment life, and leads to much unscheduled maintenance to be performed in routine of airline. The unscheduled maintenance tends to be most expensive in terms of maintenance costs because it is unplanned. Recent studies show that the cost of unscheduled maintenance for large commercial jet aircraft is in the range of 1 million pounds per aircraft per year (Kumar et al.,1999a). in order to reduce the costs, a new method based on maintenance free operating period (MEOP) has been developed.MFOP is defined as a period of operation during which the equipment must be able to carry out all its assigned missions without any maintenance action and without the operator being restricted in any way duo to system faults or limitations (Hockley, 1998). During MFOP, the necessity for any maintenance should be, by design, kept to a minimum. And the equipment is allowed to carry out only some planned minimal maintenance, such an flight servicing. A maintenance recovery period (MRP) follows immediately after a MFOP. MRP is defined as the down time during which appropriate scheduled or corrective maintenance is done to recover the system to its fully serviceable state so that it is capable of achieving the next MEOP. Not all MRPs will be of the same duration because they need to encompass different maintenance activities for individual line replaceable unit (LRU), such as those that are life-expired, those that require some overhaul and prevent maintenance or just inspection to be done to restore the full capability of those faulty systems (Hockley, 1998). MEOP is an extension of warranty period. The operators are considering extending this concept throughout the life of the system. The contractor/manufacture will be expected to guarantee that no unscheduled maintenance activities will be required during each defined period operation with the predefined level of confidence. The confidence is scaled by maintenance free operating period survivability (MFOPS) (Kumar et al., 1999b). MFOPS is defined as the probability that the item will survive for the duration of the MEOP. There are two ways to reduce DMC when conducting R&M design with MEOP for commercial aircraft. Inherent reliability of aircraft can be improved greatly. Higher reliability and therefore, the man-hours and material necessary to fix them, so DMC will be brought down. To achieve MFOPs of aircraft, it means that random failure should be eradicated during MEOP. The traditional culture, which believes that not only failures are unavoidable but also that are acceptable in a way, should be discarded. A detailed knowledge of the environment and usage to be experienced, together with a more thorough understanding of the very mechanisms of why things fail, will be fed into development programmers. Many technique or solutions will be applied to design for reliability in a more proactive way, so that failure mechanism is not given the opportunity to occur. The techniques could range from a change in physical design, selecting a different component, an improved build process, or a more radical design change. To achieve an optimum maintenance plan. Obviously, the overall system of aircraft will need some maintenance actions at some point, but there will be performed during the planned MRPs. The MEOP defers virtually all corrective maintenance to MRP, so the “unscheduled” element of maintenance is exchanged for more scheduled maintenance, based on the general improvement of reliability associated with more inherently reliable equipment. A more practical, cost-effective and balanced set of MRPs that build-up and support the best overall system MFOP, can be achieved by means of trade-off and methodology for system engineering during design. This reduce some of the uncertainty present in maintenance planning. Contingency resources could be re-allocated to scheduled work and logistic support could be concentrated in one particular location of aircraft operations. In this way, the MFOP provides the operator with flexibility in where and when it carries out its preventive and corrective maintenance to an extent. Then DMC will be reduced, because of decrease of labor and materials to cope with unserviceable aircraft. For example, line maintenance accounts for 50 per cent of all maintenance labor over the course of an aircrafts lift cycle today (Maple, 2001), the routine work of an aircraft designed by MFOP will be decreased to minimum.Fault diagnosisThe process of fault diagnosis can be generally divided into sense signal, feature extraction and diagnostic reasoning in sequence. When diagnosing failures of modern commercial aircraft, most of the procedure of sense signal and feature extraction can be accomplished automatically, due to the technology development of sensor, dynamic test and signal analysis. Then diagnostic reasoning (how to find out the source of failure) is a key factor to contribute to the efficiency of fault diagnosis. In terms of the concept of fault diagnosis, aircraft is a complicated system. Its structure is a multiple hierarchical architecture, which is comprised of many subsystems, for example, aircraft structure, engine, auto flight system, landing gear, communications system, hydraulic power and navigation system. Each subsystem is formed by subsystem or subunits are lower level. And the subsystems of subunits are usually interactive with each other. Connections between the levels of aircraft structure are usually difficult to define duo to the multiplicity and heterogeneity the structures and functions of aircraft. The quantitative relationships between the input and output of subsystem or unit usually are unavailable or inexact. Advanced technology of much technosphere has been applied to modern aircraft synthetically, such as machinery, electrics, computer, automatic control and electronics. More and more electromechanical equipments have been used in aircraft. The mechanical and electric components of these equipments have been integrated in the manner not only of control, but also of function and structure. Multidisciplinary knowledge is required to diagnose the fault of aircraft. Above issues result in the difficulties of diagnostic reasoning for commercial aircraft, and it always needs the experts participation. However, the required expert is not often available due to shift, sickness, change of employment and so on. In addition, much technosphere has been utilized in large commercial aircraft, and an expert is unl