Chapter6Vehicle EngineeringEnglish for Mechanical Engineering
Chapter 6 Vehicle Engineering English for Mechanical Engineering
CONTENTVehicle Structure Reliability6.1Vehicle System Dynamics and Control6.2Vehicle Vibration and Noise Control6.36.4VehicleDigital Design2
CONTENT 6.1 Vehicle Structure Reliability 6.3 6.2 Vehicle System Dynamics and Control 6.4 Vehicle Digital Design Vehicle Vibration and Noise Control 2
PARTONEVehicle Structure Reliability车辆结构可靠性3
PART ONE Vehicle Structure Reliability 车辆结构可靠性 3
Vehicle Structure ReliabilityReliability Definition Development--- Brief Historyfree ofdefects orsystematicfailuresatthe1960timeitleftthemanufacturer.（出厂无故障）freefromdefectsand systematicfailures at timet=o (whenthey areputintooperation)（出厂无故障）perform therequiredfunctionfailureNOWfreeforastatedtimeinterval（规定时间内无故障）haveafail-safebehaviorincaseofcriticalorcatastrophicfailures.（失效时具有故障保护功能）4
Vehicle Structure Reliability 4 Reliability Definition Development- Brief History 1960 free of defects or systematic failures at the time it left the manufacturer.（出厂无故障） NOW ✓ free from defects and systematic failures at time t = 0 (when they are put into operation) （出厂无故障） ✓ perform the required function failure free for a stated time interval （规定时间内无故障） ✓ have a fail-safe behavior in case of critical or catastrophic failures. （失效时具有故障保护功能）
VehicleStructureReliabilityProbabilityHow to Define Reliability?概率值If n statisticallyidenticaland independent items are put intooperation attimet=O to performagiven missionand v≤n of themaccomplish itsuccessfully,then theratiov/ nis a randomvariable which convergesforincreasingntothetruevalueof thereliability.t=0: v≤nsuccessfullyrandom v / nConverge:Atthetruevalue of thereliability.5
Vehicle Structure Reliability 5 How to Define Reliability ？ Probability 概率值 If n statistically identical and independent items are put into operation at time t = 0 to perform a given mission and v ≤ n of them accomplish it successfully, then the ratio v / n is a random variable which converges for increasing n to the true value of the reliability. random v / n Converge: At the true value of the reliability. t = 0： v ≤ n successfully
Vehicle Structure Reliability6.1.1 Basic Concepts(1) Reliabilitytheability of the item to remainfunctionalDefinition:the probabilitythat no operationalinterruptionswilloccurduring a statedtime intervalMission durationOperatingconditions行驶里程铁路条件气候条件行驶时间日历时间行驶速度Reguired function不发生安全性事件一一致命的能够正常行驶一一严重的不降低功能一一一般的不会引起维修一一轻微的
Operating conditions • 铁路条件 • 气候条件 • 行驶速度 Vehicle Structure Reliability 6.1.1 Basic Concepts (1) Reliability Definition： ◆the ability of the item to remain functional ◆the probability that no operational interruptions will occur during a stated time interval Mission duration • 行驶里程 • 行驶时间 • 日历时间 Required function 不发生安全性事件 —— 致命的 能够正常行驶 —— 严重的 不降低功能 —— 一般的 不会引起维修 —— 轻微的
Vehicle Structure Reliability6.1.1 Basic Concepts(1) ReliabilityR—R(t)Numerical statement:R(t) is the probability that no failure at item levelwilloccurintheinterval (O,t).R(0) = 1R(t)R(t) = P(T > t) = 「f(t)dtlim R(t) = 0t→01.00≤R(t)≤1R= R,R,R固有可靠度R,（lnherentReliability)使用可靠度Ru(Use Reliability)RR (Redundant Reliability)储存可靠度7
Vehicle Structure Reliability 6.1.1 Basic Concepts (1) Reliability Numerical statement： R(t) t 1.0 = = t R(t) P(T t) f(t)dt 0 ( ) 1 lim ( ) 0 (0) 1 = = → R t R t R t 7 R—R(t) R(t) is the probability that no failure at item level will occur in the interval (0, t). RI（Inherent Reliability） 固有可靠度 RU （Use Reliability） 使用可靠度 RR （Redundant Reliability） 储存可靠 度 R = RU RI RR
Vehicle Structure Reliability6.1.1 Basic Concepts(2) FailureMode: brittle rupture, creep, cracking, seizure, fatigue ...Cause:(1)intrinsicreason:weaknesses,wearout,(2) extrinsic reason: errors,misuse, mishandling during the designproduction,oruse.Effect: It can be different if considered on the item itself or at higherlevel.Ausualclassificationis non relevant,partial,complete,and criticalfailure.Sinceafailurecanalsocausefurtherfailures,distinctionbetweenprimaryandsecondaryfailureisimportant.Mechanism: Failure mechanism is the physical, chemical, or otherprocess resulting in a failure.8
Vehicle Structure Reliability 6.1.1 Basic Concepts (2) Failure ❖Mode: brittle rupture, creep, cracking, seizure, fatigue . ❖Cause: （1）intrinsic reason：weaknesses, wear out, （2）extrinsic reason：errors, misuse, mishandling during the design, production, or use. ❖Effect：It can be different if considered on the item itself or at higher level. A usual classification is non relevant, partial, complete, and critical failure. Since a failure can also cause further failures, distinction between primary and secondary failure is important. ❖Mechanism: Failure mechanism is the physical, chemical, or other process resulting in a failure. 8
Vehicle Structure Reliability6.1.1 Basic Concepts(3) Failure rate 入(t), MTTF, MTBF入(t) : 3 phases1(0)Early failures:BathtubCurveWearoutfailures:入(t) increases with time(t) decreasesrapidly with time;Failures with constant failure rate:入(t)isapproximatelyconstant9
λ(t) : 3 phases Vehicle Structure Reliability 6.1.1 Basic Concepts (3) Failure rate λ(t), MTTF, MTBF Wear out failures: λ(t) increases with time 9 Early failures: λ(t) decreases rapidly with time; Failures with constant failure rate: λ(t) is approximately constant Bathtub Curve
Vehicle Structure Reliability6.1.1 Basic Concepts(3) Failure rate, MTTF, MTBFNon-repairableMean time to failure (MTTF)> MTTFjsastatisticalvalueandismeant to bethemeanoveralongperiodoftimeandalargenumberof units.Meantimebetweenfailure (MTBF)Repairable&Non-repairable> MTBFisa reliabilityterm usedtoprovide the amountoffailurespermillionhoursforaproduct.10
Vehicle Structure Reliability 6.1.1 Basic Concepts (3) Failure rate, MTTF, MTBF Mean time to failure (MTTF) Mean time between failure (MTBF) 10 ➢ MTTF is a statistical value and is meant to be the mean over a long period of time and a large number of units. ➢ MTBF is a reliability term used to provide the amount of failures per million hours for a product. Non-repairable Repairable & Non-repairable