外文翻譯--工程故障分析

1、<p><b>　　外 文 翻 譯</b></p><p><b>　　班級：</b></p><p><b>　　學號：</b></p><p><b>　　姓名:</b></p><p><b>　　指導教師：</b>&

2、lt;/p><p>　　Pitting failure of truck spiral bevel gear</p><p><b>　　Abstract</b></p><p>　　Spiral bevel gears are some of the most important elements used in truck differenti

3、al. In this study, the fracture of spiral bevel gear for truck differential produced from case hardening steel is investigated. In order to study the causes of the failure,specimens prepared from the damaged spiral bevel

4、 gears were subjected to experiments, such as visual inspection,hardness, chemical analysis and metallurgical tests. Pitting occurrence on gear surfaces was observed. The effect of microstructure o</p><p>　　

5、1. Introduction</p><p>　　Differential drives are packaged units used for a wide range of power-transmission applications. The spiral bevel gears are beginning to supersede straight-bevel gears in differentia

6、l drives. They have curved oblique teeth that contact each other gradually and smoothly from one end of the tooth to the other, meshing with a rolling contact similar to helical gears (Fig. 1). They have the advantage of

7、 ensuring evenly distributed tooth loads and carry more loads without surface fatigue. Thrust load</p><p>　　2. Techniques used in fracture analysis</p><p>　　From one point of view, causes of gea

8、r failure may include a design error, an application error, or a manufacturing error. Design errors include such factors as improper gear geometry as well as the wrong materials, quality levels, lubrication systems, or o

9、ther specifications. Application errors can be caused by a number of problems, including mounting and installation, vibration, cooling, lubrication, and maintenance. Manufacturing errors may show up in the field as error

10、s in machining or heat </p><p>　　visual inspection and fractography;</p><p>　　hardness tests;</p><p>　　chemical analysis;</p><p>　　metallographic analysis;</p>&

11、lt;p>　　contact stress calculation.</p><p>　　3. Analysis and results</p><p>　　3.1. Visual inspection and fractography</p><p>　　The investigated gears are shown in Fig. 3. The fail

12、ed gears showed similar failure and did bear indication of fatigue crack growth when the fracture surface was examined, indicating that the failure was of a brittle type of fracture. The pitting on gear teeth surfaces as

13、sisted the failure. Pitting is caused by excessive surface stress due to high normal loads, a high local temperature due to high rubbing speeds, or inadequate lubricant. The pitting occurrence and the fractured surfaces

14、of gears</p><p>　　3.2. Hardness analysis</p><p>　　Case-hardened gears are hardened only on the surface of the gear teeth, to a predetermined depth, to about 58 to 62 Rockwell C, or roughly as ha

15、rd as a bearing race. The increased hardness improves the gear’s durability rating by providing greater resistance to pitting and greater strength, or resistance to</p><p>　　breakage [4–6]. Hardness analysis

16、 of fractured gear materials was carried out using a Rockwell hardness test machine. The measurements were carried out on three different surface areas. The core and surface hardness values are given in Tables 2 and 3. C

17、ore hardness over 40 HRC is not recommended due to potential for distortion, residual stresses, and brittleness but the gear 1 core hardness value is higher than the recommended values. The surface hardness of gears was

18、observed as 50–54 HRC which</p><p>　　3.3. Chemical analysis</p><p>　　Chemical analyses of 20MnCr5 and 17NiCrMo6-4 case hardening steels according to EN 10084 are shown in Table 4. The chemical c

19、omposition of the piston materials was determined by spectroscopy chemical analysis. The chemical compositions of gear material are listed in Table 5. It was understood from the chemical composition that the material was

20、 case hardening steel. The gear 1 is 17NiCrMo6-4 and 2, 3 and 4 are 20MnCr5. The composition of gear materials contains low C and Cr, Ni and Mo content, wh</p><p>　　3.4. Metallographic analysis</p>&l

21、t;p>　　The metallographic specimens were first ground, polished and etched using standard techniques in order to examine the inner structure. A light optical microscope was used in the investigations. It can be underst

22、ood from the figures that the gears were carburized and then cooled in the oil ambient. The microstructures of the failed gear materials show that they are similar structures. From the observation, it is concluded that t

23、he case hardening process was not properly done. Also, because of the</p><p>　　3.5. Stress calculation</p><p>　　Since the pitting occurrence was observed at visual inspection, the contact stress

24、 on gear teeth was calculated.The stress experienced by the spiral bevel tooth during operation was estimated using the design torque of 250 Nm. The contact stress on the loaded tooth can be calculated using the equation

25、 [7]。</p><p>　　The terms used in equation are explained in Table 6. Using Eq. (1) and Table 6, the contact stress was calculated to be 1994 MPa. According to literature [6,7], allowable contact stress is 155

26、0 MPa. This value is lower than the calculated value. In this case, gears have about 0.77 safety factors and they have not contact strength. Thus, the pitting failure was observed on gear teeth surface. The occurring pit

27、s have contributed to</p><p>　　the failure of gears.</p><p>　　4. Conclusion</p><p>　　In this research, the influences of microstructure, chemical composition and hardness of the gea

28、rs were investigated and contact stress was calculated. From the experimental observations and calculations, the following conclusions may be made:</p><p>　　1. In order to obtain same hardness and microstruc

29、ture, the gear materials should be of same chemical composition.</p><p>　　2. The surface hardness of gears is low. In order to obtain maximum pitting resistance, the gears outer surface hardness should be in

30、creased to 58–60 HRC.</p><p>　　3. In order to obtain different microstructure between core and surface, carburising heat treatment should be made proper conditions, such as time, case depth. The case depth s

31、hould be under control.</p><p>　　4. Due to the high tooth-contact pressures, oil film thickness may not be enough. The lubrication could be difficult. Therefore, the pitting occurrence increases. On the exam

32、ination of fractured parts, it can be concluded that the gears expose to overloading. In order to decreasing contact pressure, the gears geometry can be optimized in design stage or the pinion design torque can be decrea

33、sed.</p><p>　　卡車螺旋錐齒輪的點蝕故障</p><p><b>　　摘要：</b></p><p>　　螺旋錐齒輪是卡車差動齒輪中的重要組成部分。在這個研究當中，對因表面硬化鋼齒輪而導致卡車差動齒輪中錐齒輪的斷裂進行了調(diào)查。為了研究引起失效的原因，專家們從損壞的錐齒輪樣品中進行實驗，如外觀檢查，硬度、化學分析和冶金測試。齒輪表面

34、的點蝕是可以被觀察到的。微觀結構的效應在斷裂中被考慮了進去。低表面硬度的價值被發(fā)現(xiàn)。被計算的接觸應力高于可允許的接觸應力是這篇文章介紹的重點。</p><p><b>　　介紹</b></p><p>　　差分驅動器廣泛應用于動力傳輸?shù)膯卧?。螺旋錐齒輪開始在差分驅動器中優(yōu)于直錐齒輪。它們有彎曲的斜齒，并且逐漸接觸從一端過渡到另一端，嚙合的螺旋齒輪類似于滾動接觸。它們的

35、優(yōu)點是確保負載均勻的分布在齒上，從而使其攜帶更多的載荷且不發(fā)生表面疲勞。推力載荷取決于旋轉的方向和螺旋角的正負，調(diào)查的螺旋錐齒輪是由倆種不同的表面硬化鋼構成的，表面硬化鋼（20MnCr5,EN10084)具有低的碳-鉻元素，其他鋼（17NiCrMo6-4,EN10084)具有低的鎳-鉻-鉬元素和中等的淬透性，在一般的軋制條件下，供給的最大布氏硬度為280（30HRC）。它的特點是在經(jīng)過滲碳、淬火和回火后，中型材表面硬度提升至62HRC時

36、，可以承受較高的應力并且具有較小的韌性。這些鋼（非滲碳）也可用于作為高強度鋼，并且通過適當?shù)拇慊鸷突鼗鸷?，產(chǎn)生較好的拉伸強度和韌性，可滿足多種應用?？ㄜ囘\行的每個月中大約都有三個齒輪損壞。因此，對卡車中受損的螺旋錐齒輪進行了評估，并且分析了表面硬化鋼制造的齒輪斷裂的原因。</p><p>　　斷裂分析中應用的技術</p><p>　　從企業(yè)的角度來說，齒輪發(fā)生故障的原因可能有設計錯誤、程序

37、錯誤或者制造錯誤。設計錯誤包括齒輪幾何形狀不當，材料不當，質量水平不夠或是潤滑系統(tǒng)不完善。程序錯誤包括安裝、振動、冷卻和維護多個因素構成。制造錯誤可能會發(fā)生在現(xiàn)場的熱處理或是作業(yè)中的不當處理。</p><p>　　在這個分析中，四個損壞的螺旋錐齒輪樣本進行各種實驗。進行的實驗以及測量結果如下：</p><p><b>　　1、外觀和斷口檢驗</b></p>

38、<p><b>　　2、硬度實驗</b></p><p><b>　　3、化學分析</b></p><p><b>　　4、金相分析</b></p><p><b>　　5、接觸應力的計算</b></p><p><b>　　分析方

39、法和結果</b></p><p>　　3.1 外觀和斷口檢驗</p><p>　　在圖3所示調(diào)查的齒輪中。失效的齒輪都表現(xiàn)出了類似的故 障，對疲勞裂紋擴展的斷裂面進行了檢查，表明故障時脆性的折斷。</p><p>　　齒牙上的表面點蝕促進了齒輪的失效。點蝕是由于過多的表面承受高載荷，由于過高的摩擦速度導致局部溫度過高，或是不充分潤滑導致的。示于圖4的齒輪

40、發(fā)生點蝕的斷裂表面，通過其斷面表面，可以說是由于點蝕導致的。</p><p><b>　　3.2 硬度分析</b></p><p>　　表面硬化的齒輪的硬化只發(fā)生在齒輪表面，達到預定深度，達到58到62洛氏溫度。通過增加硬度來提高齒輪的耐用性可以通過增加抗點蝕能力和提高耐斷裂強度來達到。使用洛氏硬度試驗機對斷裂的齒輪材料進行了硬度分析，進行了三個不同表面區(qū)域的測量。其

41、芯部和表面的硬度值分別在表2和表3中給出。由于潛在的失真，剩余應力和脆性，硬度高于40HRC的材料是不推薦的，但是齒輪1的硬度值是高于推薦值的。被觀察到的50-54HRC表面硬度的材料是低于文獻中所提到的數(shù)值的。</p><p><b>　　3.3 化學分析</b></p><p>　　對表面材料20MnCr5和17NiCrMo6-4的齒輪進行化學分析，通過EN100

42、84在表4中給出。由光譜化學分析確定材料的化學組成。齒輪材料的化學成分在表5中給出。通過觀察該材料的化學成分，確定該材料為硬化鋼。齒輪1的材料為17NiCrMo6-4，齒輪2、3和4的材料為20MnCr5。齒輪材料的化學成分含有量較低的C和Cr,Ni和Mo元素，通過急速冷卻后可形成特定的結構。合金添加劑可以提高鋼的淬透性。鉻可以提高耐腐蝕性，而錳有助于脫氧的熔融，同時提高了可加工性。鎳減少淬火開裂后的變形。</p><

43、;p><b>　　3.4 金相分析</b></p><p>　　失效的齒輪材料有著相類似的結構。從觀察中可以得到結論。該情況下，硬化過程不完全。此外由于熱處理應用不當，齒輪材料中的馬氏體在圖5中呈現(xiàn)。</p><p><b>　　3.5 應力計算</b></p><p>　　通過可視觀察齒輪的點蝕，發(fā)生在輪齒上的接觸

44、應力是可以被計算的。在對螺旋錐齒輪試驗中，對齒輪附加扭矩為250NM。對于附加在輪齒上的接觸應力可以由公式7計算。表6中有對該公式的術語解釋。使用公式1和表6可以計算出接觸應力為1994MPa。通過文本給出，可允許的接觸應力為1550MPa。此值低于計算給出的數(shù)值。在這種情況下，齒輪大概有0.77安全系數(shù)且沒有達到其接觸強度。因此，在輪齒表面上可觀察到點蝕現(xiàn)象。點蝕的發(fā)生是齒輪失效的原因。</p><p><

45、;b>　　總結</b></p><p>　　在這次的實驗中，微觀結構、化學組成和齒輪硬度被考慮了進來，同時計算出接觸應力。從實驗觀測和應力計算中，得出以下結論：</p><p>　　為了獲得相同的硬度和微觀結構，齒輪材料應該有相同的化 學組成。</p><p>　　齒輪表面硬度過低。為了獲得最大的耐腐蝕性，齒輪的表面 硬

46、度應提高至58-60HRC。</p><p>　　為了獲得不同的芯部和表面組織，滲碳熱處理應給出適當?shù)?條件，如時間、硬化層深度等等，深度應在控制之下。</p><p>　　由于高的齒接觸壓力，可能達不到足夠的油膜厚度。潤滑可 能非常困難，導致點蝕發(fā)生增加。通過裂隙部位的檢查，可 以得出結論，齒輪承受重載荷。為了降低接觸應力，可以對

47、齒輪的幾何形狀進行優(yōu)化。在設計階段中，小齒輪的設計可 以降低扭矩。</p><p>　　Engineering failure analysis </p><p><b>　　Abstract</b></p><p>　　The scale and complexity of computer-based safety criti

48、cal systems, like those used in the transport and manufacturing industries, pose significant challenges for failure analysis.</p><p>　　Over the last decade, research has focused on automating this task. In o

49、ne approach, predictive models of system failure are constructed from the topology of the system and local component failure models using a process of composition. An alternative approach employs model-checking of state

50、automata to study the effects of failure and verify system safety properties. In this paper, we discuss these two approaches to failure analysis. We then focus on Hierarchically Performed Hazard Origin & Prop</p&g

51、t;<p>　　1. Introduction</p><p>　　Increasing complexity in the design of modern engineering systems challenges the applicability of rule-based design and</p><p>　　classical safety and reli

52、ability analysis techniques. As new technologies introduce complex failure modes, classical manual</p><p>　　analysis of systems becomes increasingly difficult and error prone.To address these difficulties, w

53、e have developed a computerised tool called ‘HiP-HOPS’ (Hierarchically Performed Hazard Origin & Propagation Studies) that simplifies aspects of the engineering and analysis process. The central capability of this to

54、ol is the automatic synthesis of Fault Trees and Failure Modes and Effects Analyses (FMEAs) by interpreting reusable specifications of component failure in the context of a system model</p><p>　　2. Safety an

55、alysis and reliability optimisation</p><p>　　3. Safety analysis using HiP-HOPS</p><p>　　HiP-HOPS is a compositional safety analysis tool that takes a set of local component failure data, which d

56、escribes how output failures of those components are generated from combinations of internal failure modes and deviations received at the components’ inputs, and then synthesises fault trees that reflect the propagation

57、of failures throughout the whole system.From those fault trees, it can generate both qualitative and quantitative results as well as a multiple failure mode FMEA</p><p>　　[35].A HiP-HOPS study of a system de

58、sign typically has three main phases:</p><p>　　Modelling phase: system modelling & failure annotation.</p><p>　　Synthesis phase: fault tree synthesis.</p><p>　　Analysis phase: f

59、ault tree analysis & FMEA synthesis.</p><p>　　Although the first phase remains primarily manual in nature, the other phases are fully automated. The general process in</p><p>　　HiP-HOPS is i

60、llustrated in Fig. 2 below: The first phase – system modelling & failure annotation – consists of developing a model of the system (including hydraulic, electrical or electronic, mechanical systems, as well as concep

61、tual block and data flow diagrams) and then annotating the components in that model with failure data. This phase is carried out using an external modelling tool or package compatible with HiP-HOPS. HiP-HOPS has interfac

62、es to a number of different modelling tools, includ</p><p>　　4. Design optimisation using HiP-HOPS</p><p>　　HiP-HOPS analysis may show that safety, reliability and cost requirements have been me

63、t, in which case the proposed system design can be realised. In practice, though, this analysis will often indicate that certain requirements cannot be met by the current design, in which case the design will need to be

64、revised.This is a problem commonly encountered in the design of reliable or safety critical systems. Designers of such systems usually have to achieve certain levels of safety and reliability wh</p><p>　　is

65、creative. However, we believe that further automation can assist the process of iterating the design by aiding in the selection of alternative components or subsystem architectures as well as in the replication of compon

66、ents in the model, all of which may be required to ensure that the system ultimately meets its safety and reliability requirements with minimal cost.A higher degree of reliability and safety can often be achieved by usin

67、g a more reliable and expensive component, an</p><p>　　alternative subsystem design (e.g. A primary/standby architecture), or by using replicated components or subsystems to achieve redundancy and therefore

68、ensure that functions are still provided when components or subsystems fail. In a typical</p><p>　　system design, however, there are many options for substitution and replication at different places in the s

69、ystem and different</p><p>　　levels of the design hierarchy. It may be possible, for example, to achieve the same reliability by substituting two sensors</p><p>　　in one place and three actuator

70、s in another, or by replicating a single controller or control subsystem, etc. Different solutions will, however, lead to different costs, and the goal is not only to meet the safety goals and cost constraints but also t

71、o do so optimally, i.e. find designs with maximum possible reliability for the minimum possible cost. Because the options for replication and/or substitution in a non-trivial design are typically too many to consider man

72、ually, it is virtually imposs</p><p>　　Recent extensions to HiP-HOPS have made this possible by allowing design optimisation to take place automatically [38].</p><p>　　HiP-HOPS is now capable of

73、 employing genetic algorithms in order to progressively ‘‘evolve” an initial design model that</p><p>　　does not meet requirements into a design where components and subsystem architectures have been selecte

74、d and where redundancy has been allocated in a way that minimizes cost while achieving given safety and reliability requirements. In the course of the evolutionary process, the genetic algorithm typically generates popul

75、ations of candidate designs which employ user-defined alternative implementations for components and subsystems as well as standard replication strategies.These strategies are b</p><p>　　may be represented b

76、y an encoding string of three digits, the value of each of which represents one possible implementationfor those components. However, although this is sufficient if the model has a fixed, flat topology, it is rather infl

77、exible and</p><p>　　cannot easily handle systems with subsystems, replaceable sub-architectures, and replication of components, since this</p><p>　　would also require changing the number of digi

78、ts in the encoding string.The solution used in HiP-HOPS is to employ a tree encoding, which is a hierarchical rather than linear encoding that can more accurately represent the hierarchical structure of the system model.

79、 Each element of the encoding string is not simply just a number with a fixed set of different values, it can also represent another tree encoding itself. Fig. 7 shows these different possibilities: we may wish to allow

80、component A to</p><p><b>　　工程故障分析</b></p><p><b>　　摘要</b></p><p>　　像在交通運輸業(yè)和制造業(yè)中，使用的基于計算機安全的系統(tǒng)的規(guī)模和復雜性，對工程故障分析帶來了重大的挑戰(zhàn)。在過去的十年中，這個任務主要由自動化來完成。有一種系統(tǒng)故障模型是從系統(tǒng)的拓撲結構和

81、本地使用過程中的組成構件來預測故障的模式。另一種方法是采用自動檢查狀態(tài)的模型來研究失效的影響，并驗證系統(tǒng)的安全性能。在本文中，我們將討論倆種方法失效分析。然后，我們專注于分級研究危險的起源和傳播（HIP-HOPS）——一個更先進的構圖方法——故障樹，其功能可以自動合成，組合失效模式后果分析，可靠性和成本，系統(tǒng)通過自動模式transformations.We的應用來優(yōu)化總結這些特點，并通過簡化船舶發(fā)動機的燃油系統(tǒng)來證明HIP-HOPS在其

82、中的應用。根據(jù)這個例子，我們討論了與其他國家先進技術相比較，這種方法的優(yōu)勢和局限性。特別是由于HIP-HOPS能夠演繹，可以歸結出系統(tǒng)故障的原因，并且不容易發(fā)生組合爆炸，更容易的進行迭代。出于這個原因，它成為對故障和優(yōu)化設計進行評估的啟發(fā)式算法。</p><p><b>　　介紹</b></p><p>　　現(xiàn)代工程系統(tǒng)的日益復雜對以規(guī)則為基礎的設計，經(jīng)典的安全性和可

83、靠性分析技術的實用性提出了挑戰(zhàn)。隨著新技術的引入和復雜的故障模式，經(jīng)典的系統(tǒng)分析變得越來越困難并且錯誤百出。我們已經(jīng)開發(fā)出一種計算機工具，稱為HIP-HOPS（分層分析危險來源），用于簡化工程設計和分析過程。這個工具的核心在于自動分析故障樹，以及重復分析系統(tǒng)模式內(nèi)部的失效單元的FMEAs。分析是自動的，只需要初始的組件故障數(shù)據(jù)，因此，減少了手工安全檢查，在相同的時間內(nèi)，可擴展的底層算法可以相對快速的分析復雜的系統(tǒng)，也可以進行碎片式的故障

84、分析。最近，我們通過選擇和復制的組件和替代子系統(tǒng)架構，來解決一個優(yōu)化設計問題：可靠性和成本優(yōu)化。HIP-HOPS從引進遺傳算法得出非最優(yōu)方案進化到以小成本獲得高的可能性的新設計。通過選擇不同的組件實現(xiàn)不同的可靠性和成本特征，或用子系統(tǒng)替代架構，具有更強大的功能，可以解決許多方案，從大的空間探索到快速評估。我們希望在HIP-HOPS下，計算機輔助設計和建模工具能夠結合使用，用于進行高度自動化和簡化集成的安全性和可靠性分析并且改進設計過程。

85、反過來，我們希望解決更廣泛的問題，研究如何讓安全更加可控，以</p><p>　　安全性分析HIP-HOPS</p><p>　　HIP-HOPS的主要部分是安全性分析工具，將一組描述了這些組件如何產(chǎn)生故障的內(nèi)部故障模式的本地組件故障數(shù)據(jù)輸入，然后整合生成令整個系統(tǒng)產(chǎn)生故障的故障樹。通過這些故障樹。可以生成定性和定量的結果以及多種失效模式FMEA。HIP-HOPS系統(tǒng)設計的研究通常有三個主

86、要階段：</p><p>　　建模階段：系統(tǒng)建模和故障注解。</p><p>　　合成階段：故障樹合成。</p><p>　　分析階段：故障樹分析和FMEA合成。</p><p>　　第一階段主要是手動進行，其他階段是完全自動的。圖2所示是HIP-HOPS的一般過程：第一階段——系統(tǒng)建模和故障注解——包括開發(fā)一個模型系統(tǒng)（包括液壓，電氣或電子

87、，機械系統(tǒng)以及概念方框圖和數(shù)據(jù)流圖），然后對該模型的組件故障數(shù)據(jù)進行編序。此階段的進行需要外部建模工具與HIP-HOPS兼容。HIP-HOPS提供一些不同建模工具的接口，包括Matlab的Simulink，基于Eclipse的UML工具，特別是SimulationX。后者集完全集成的接口與HIP-HOPS ITI GmbH公司開發(fā)的工程建模與仿真工具于一身。它的優(yōu)點是無論現(xiàn)存的系統(tǒng)模型或是模型設計到什么程度，它都可以用來做安全性分析，而

88、不用專門為安全性分析去建模。第二階段是在故障樹合成過程當中的。在這個階段，通過與模型相結合，HIP-HOPS可以自動跟蹤由于單個模塊及子系統(tǒng)的局部破壞導致失敗的數(shù)據(jù)傳播路徑。因此，由網(wǎng)絡和故障樹之間的定義關系，得出系統(tǒng)輸出失敗的根源在于單個組件的故障模式。這是一個演繹的過程，追溯到系統(tǒng)的輸出從而決定是哪種因素導致系統(tǒng)的失敗，并能找到涉及什么樣的邏輯組合。這些故障樹分析和生成FMEA。首先將故障樹最</p><p>

89、;　　HIP-HOPS的優(yōu)化設計</p><p>　　HIP-HOPS可以顯示出預期的安全系統(tǒng)的安全系數(shù)，可靠性及成本。實際上，這個分析軟件通常預測出的特定需求不能與現(xiàn)存的設計相符，這就導致要隨著設計的改變而改變。經(jīng)常與設計要求的安全系數(shù)和可靠性不符。這種系統(tǒng)的設計者通常要在有限的成本內(nèi)達到一定的安全系數(shù)和可靠性。設計是一個創(chuàng)造性的工作，依賴于有較強能力的設計團隊，并從早期的成功項目中吸取經(jīng)驗教訓。但是，我們相信

90、，進一步的自動化可協(xié)助迭代設計的過程，幫助選擇替代的組件或子系統(tǒng)架構，以最小的成本確保該系統(tǒng)最終的安全性和可靠性要求。為了獲得較高的可靠性和安全性，通?？梢允褂靡粋€更可靠的組分，通過子系統(tǒng)替代的設計（例如：A 主/備用體系結構），或者通過復制的組件或子系統(tǒng)實現(xiàn)冗余，來確保部件或子系統(tǒng)失效時功能仍然保持。可是，在一個經(jīng)典的系統(tǒng)設計中，在系統(tǒng)的不同區(qū)域在不同的設計層次，會有許多種替代和復制品的選擇。這是可能的，比如使倆個傳感器或是三個驅動器

91、達到相同的可靠性，可以通過單一控制器的復制或是子系統(tǒng)的控制等方案來解決。然而，不同的方案會導致不同的成本，我們的目標不僅要滿足安全的預期還要考慮到成本的限制，所以最大的可靠性和盡可能小的成本設計才是</p><p>　　HIP-HOPS的最新擴展可能使這種設計優(yōu)化自動生效。通過遺傳學算法，使在初始設計中不滿足設計要求的組成和組分，以最小的成本和最大的可靠性，“進化”到預期的設計要求。在遺傳學進化過程中，通過用戶定

92、義實現(xiàn)的組件和子系統(tǒng)來實現(xiàn)人口的候選設計，這也是標準復制的方法。這些方法被廣泛使用，如多數(shù)表決產(chǎn)生的模塊化冗余等等。對于用遺傳算法選擇最佳設計方案，這個選擇過程可以被應用到優(yōu)勝劣汰的生存設計和傳遞給下一代的基因候選設計。每個設計的適用性依賴于其成本和可靠性。因此，為了計算適用性，必須計算這個倆個方面。一個系統(tǒng)的成本意味著每個組分的成本的總和（如果要更精確的計算系統(tǒng)的成本，生命周期成本也應該考慮進去，例如生產(chǎn)、組裝和維護成本等）。雖然計算