【作者】 李跃峰；

【导师】 王广林；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 一般常用的机械系统、设备或装置都是长期运行、反复使用的，本文称之为“常规机械”。而在某些特殊场合中，有一类机械只使用一次后就被放弃不用，这类机械被称为“一次性机械”。一次性机械中的机械零件可以笼统地称为“一次性机械零件”。一次性机械零件的设计理论和方法与常规机械零件设计方法应当有所不同，然而，由于目前并未对一次性机械零件与常规机械零件给予明确的区分，所以一次性机械零件的设计仍然沿用常规机械零件的设计思想和方法，这就导致将常规机械设计准则中用于一次性机械零件设计时，不可避免的出现设计结果冗余，造成整体设计指标下降，有时甚至无法满足设计要求。虽然采用试验样机法在一定程度上能够完成一次性机械的研制，但是该方法的研制周期较长、效率较低、成本过高，不能满足日益增加的研制任务要求。因此，有必要深入研究一次性机械零件的设计理论和方法，以便为一次性机械设计理论体系的建立打下基础。在归纳总结常规机械零件设计准则和方法的基础上，本文将一次性机械中承受循环载荷次数少的机械零件定义为一次性机械零件，明确了一次性机械零件不同于常规机械零件的基本特征，提出了在一次性机械零件设计时应该遵循的基本原则，并通过与常规机械零件设计方法的对比计算，阐明了一次性机械零件概念提出的意义。在提出了一次性机械零件概念的基础上，本文研究了一次性机械零件与常规机械零件的区分界限。首先，基于疲劳理论，根据机械零件失效形式的不同，将一次性机械零件划分为两类分别进行研究。特别针对发生弹性失效的情况，以常用齿轮钢40Cr为试验材料，深入研究了40Cr在较高循环应力水平下的低周疲劳失效和棘轮失效行为。根据实验结果，定义了产生0.2%的总塑性应变时所对应的循环载荷作用次数为疲劳弹性失效寿命，并用疲劳弹性失效替代疲劳断裂作为高应力作用下的一次性机械零件疲劳失效的判断依据，修正了材料在高应力作用下的疲劳失效寿命模型。为了满足一次性机械零件的高可靠性要求，在40Cr的疲劳特性研究中，根据试验结果，确定了疲劳弹性失效寿命的概率分布类型为三参数Weibull分布，并采用灰色估计和最大相关系数优化法进行了参数估计，在参数估计中依据最可靠原则来确定疲劳概型参数，在提高材料许用应力范围的同时保证一次性机械零件高可靠性要求。本文还以直齿渐开线圆柱齿轮零件为例研究了典型一次性机械零件的设计方法。在研究过程中，规划了一次性齿轮零件的研究内容，继承和改进了常规齿轮零件设计准则和方法，使之适用于一次性齿轮零件的设计。建立了小模数直齿渐开线圆柱齿轮的低周疲劳强度设计模型。该模型由两个子模型组成，首先建立了基于啮合过程的齿轮接触有限元仿真模型，利用该模型研究了较高载荷下齿轮的齿间载荷分布特征，分析了主要安装误差对齿轮应力状态的影响，获取齿根处应力应变信息。然后，基于FS模型和临界平面理论，利用有限元模型得到的应力应变信息，进行了齿根弯曲强度设计。为验证该疲劳强度设计模型的准确性，研制了小模数齿轮对称疲劳试验机。以40Cr小模数齿轮为试验对象，验证了所建立的疲劳强度设计模型的有效性。开展了某型号箭用舵机减速器的研制工作，该减速器采用谐波传动形式，减速比300，具有输出80Nm扭矩的能力，总重量约1000g。在研制过程中，采用一次性机械零件设计方法，运用所建立的疲劳强度设计模型，对直筒形柔轮的进行了疲劳强度设计，最后，通过专用测试台测试了所研制的谐波减速器性能，结果表明各项指标均满足要求。更多还原

【Abstract】 This paper calls the long-term and repeated machines as “general machines”. Insome special occasions, there is a kind of machines used only once before beingabandoned. Such kind of machines are called as "disposable machines”. Mechanicalelements in the disposable machines can be loosely called as “diposable mechanicalelements (DME)”. It could be foreseeable that the design method and theory ofDME should be different from general mechanical elements. However, until now theDME have not been distinguished from general mechanical elements, so the designof DME still follows design methods and theories of the general mechanicalelements, although it will be inevitable to obtain redundant design results. Even attimes, the design tasks can not be completed. A test prototype method is commonlyused in the design of DME now. However, the method with long period is inefficientand high cost, which can not meet the heavy design tasks. Therefore, it is necessaryto focus on the research of design methods and criteria of DME, which will build thefoundation of the design theory system of DME.Based on the summary of design methods and criteria of general mechanicalelements, this paper provides the definition of DME, that is the elementsundertaking fewer cyclic loading numbers in the disposable machinery. The basicproperties and principles of DME design is explicitly provided. Furthermore, thesignificance of DME design theory is clarified by the contrast calculation betweenthe DME design theory and general mechanical design theory.Distinguish boundaries of DME and general mechanical elements areconcerned in this paper. Firstly, according to the fatigue theory and failure types ofmechanical elements, the DME are divided into two categories. In particular, for theelements with elastic failures, steel40Cr is selected as test materials to research thelow cycle fatigue and ratcheting behaviors of metals under high level cyclic stresses.On the basis of the test results, the fatigue elastic failure life (FEFL) is defined asthe cyclic numbers when the plastic strain reach0.2%. The fatigue elastic failurewas used to replace the fatigue fracture as the failure criteria of metals under highlevel cyclic stresses. The failure models of materials under high level stresses aremodified. To meet the high reliability requirements of DME, three-parameterWeibull distribution is used to evaluate the material fatigue elastic failure life data.The gray theory and maximum correlation coefficient method are selected toestimate the parameters of three-parameter Weibull distribution. In the parameterestimation process, the most reliable principle is used. By this way, allowancestresses range are improved and the reliabilities of DME are certified at the same time.This paper used straight involute gears as the typical DME to research thedesign method of DME. The research content is firstly determined. The generalmechanical design criteria and methods are partly accepted and improved to besuitable for the design of DME. A low cycle fatigue strength design model ofstraight involute cylinder gear with small modulus is built. The model consists oftwo parts. The first part is a gear contact finite element model based on the meshprocess. According to the model, load distribution properties under high level loadand installation errors are researched. In addition, the deddendum stress informationcould be obtained from the model. The second part is a fatigue strength designmodel based on the FS model and critical plane theory. The stress informationobtained from the finite elements model are used in the second model for thestrength design. A fatigue test machine which could be used for the gearsymmetrical fatigue test is developed. By using this machine, fatigue tests on thesmall modulus gears manufactured by40Cr steel are conducted. Experiment resultsshow that the fatigue strength design model provided in the paper is effective. Forthis reason, the DME design theory is proved to be feasible.Certain type rocket steering reducer is developed based on the DME designtheory. The harmonic reducer type is selected. The reducer ratio is300and theoutput torque is up to80Nm. The weight of the reducer is about1000g. In the designprocess, the fatigue strength of straight shape flexsplines are researched by using theDME design methods combined with the fatigue strength design model built in thepapaer. Finally, the performance test of the reducer is conducted on a special testmachine. The test result shows that the performance of the reducer meets thespecification requirements.更多还原