APS机械专业第三学期

1.马克思主义基本原理概论 Survey of Marxism TheoryBecause China is a socialist country, we must study in college political course, the basic principles of Marxism is one of the important required courses. This course mainly includes three main components, which are also the three components of Marxism, namely, Marxist political economics, dialectical materialism and historical materialism, and scientific socialism. In the course of Marxism is expounded the specific meaning of each part, analyzers the application and development of the fundamental principle of Marxism in China.2.力学基础 Basis MechanicsSome basically concepts about theoretical mechanics and material mechanics，just an introduction。

And specific knowledge was taught in next term.3.工程图学基础 Fundamental of Engineering GraphicsTaught us many rules methods about engineering graphics.The course can train the student’s ability of space analyzing. It introduces some drawing methods such as the projection of the point, line, plane and body and three-view drawing,details drawing, it also tells you how to read the assembly drawing. Thisis an example(give an example, illustrate by) that we use the RectangularProjection Theorem to confirm the relations between the lines, lines andthe planes(whether the lines are parallel). And also some section linessuch as the intersection line are really complex. This course is thefoundation of the Mechanical Design.4.机械基础The Basis of MachineChapter 0●Mechanism机械制造a device装置designing to transform改变force and moment into adesigned output输出force and moment.●What is the relation between mechanism机制and machines机器?Same. 1. Combinations组合of rigid bodies刚体. 2.motions运动are definite确定的Difference 1.machines can transform转变energy.●Degree of freedom DOF:the number of independent movement自主运动in a plane 3 DOF. in a space 6 DOFChapter 1●Kinematic运动学constraints约束---decrease减少DOF●Kinematic pairs运动副1.Lower pairs---area contact---removes去除2 DOF2.Higher pairs ----line/point contact---removes 1 DOFEquation: F=3n-2P l-P h Davon n---except frame除了框架PS: a. Compound joint复合铰链double count双重计算b. Passive DOF局部自由度. Ignore 忽略eg. Roller of cam凸轮滚子:the rotation转动of roller does not influence the DOF of the whole system.→c. Passive constraint虚约束Ignore●Assur group杆组:can not be devided认定& DOF=0Second link group第二个链接组n=2 p=3●Lower pairs replace higher paris高幅低代DOF V t.a t. Not changeChapter 2 planar links mechanism平面联系机理●1.crank-rocker曲柄摇杆mechanism2.double-rocker双摇杆mechanismParallelogram平行四边形mechanism :wheels of train火车轮antiparallelogram等边梯形mechanism: door open at the same time同时开门系统3.double rocker●application of planar 4 links应用4连杆平面mechanismsin. slide-crank曲柄滑块mechanism guide-bar导杆mechanism●the conditions of the existence for crank 曲柄的存在条件1.shortest+longest≤the rest A+B2.shortest is side link连架杆(crank-rocker) or frame机架(double-crank双曲柄)●The quick-return characteristic快回特性coefficient of velocity variation速度变化系数. K21180 180v Kvθθ+==-imbalance angle极位夹角(closed angle). θ●The dead point 死点The rocker is driving link, when the driving angle γ=0. dead point position位置solution?→ 1.inertia惯性. 2.more than one driving with different driving angle like trains' left& right wheels飞轮●the instance center of velocity速度瞬心number of instance center of velocity 2(1) 2N N NK C -==(including GROUND)●the Aronhold-Kennedy theorem三心定理（DH. theorem of three center ）3 instance center of 3 planar member must be located on the same line●Self-lock自锁For sliding pair滑动幅. f=tanφ. driving angle stay in the φ. -- self lock area For revolute pair.转动副the radius of frictional circle 摩擦圆半径: ρ=f v * re=ρ uniform rotation匀速转动or start to rotate开始转动e＞ρ accelerate to rotate加速转动e ＜ρ self lock 自锁force analyse 受力分析:1.find 2-force pole 受力杆,pull 拉 or press 压, find out de direction :out inner2.analyse the change 变化 of the angle, the f should prevent 防止 its motion3.three balanced force cross at one point, friction angle 摩擦角 φ.Chapter 3. Cam 凸轮● driver rotation 驱动旋转follower line motion : forward 前进 backward 后退● rigid impact 刚性冲击: same speed 相同速度soft impact 柔性冲击: same acceleration 相同加速度 sin cos 345● offset distance 偏心量. Clockwise 顺时针.left. anticlockwise 逆时针right ● prime circle 基圆. the pitch curve 理论廓线 (track of 跟踪 the center of thecam). the cam contour 实际廓线(the contact point)Chapter 4. Gears 齿轮● planar gear mechanisms 平面齿轮机构spur gear 直齿圆柱齿轮,helical gear 斜齿轮,double helical gear 双斜齿齿轮,rack 齿条 and pinion 小齿轮, planetary gear train 行星轮系● spatial gear mechanisms 空间齿轮机构bevel gear 锥齿轮,worm 蜗杆and worm wheel 蜗轮● Fundamentals of Engagement of Tooth Profiles 齿轮啮合基础121221O P i O Pωω==. the pitch point 节点 is the instance 实际 center of velocity ● the shape 形状 of the Toothinvolute 渐开线(depended on the base circle 基圆) make sure the transmission ratio 传动比 is a constant value 不变的值.● Tooth profiles 齿廓addendum circle 齿顶圆 d adedendum circle 齿根圆 d fthe face width 齿宽 + tooth space width 齿间距= pitch 节距 pthe reference circle 分度圆 dthe base circle 基圆 d b = mzcosαaddendum circle-dedendum circle=tooth depth 齿全高tooth number 齿数 zmodule 模数 m┌p=πm└d=mzpressure angle 压力角 α. normally 20º in CHN , sometimes for more strength 25º is recommended 推荐the coefficient 系数 of addendum. h'a . h a =h'a *mthe coefficient系数of bottom clearance顶隙--prevent the interference干扰c=c'*mnormal tooth h a'=1 c'=0.25. shorter tooth短齿. h a'=0.8 c'=0.3rotation frequency旋转频率nangular frequency角频率ω●the manufacturing method of involute profile渐开线齿廓的制造方法generating cutting范成法/滚齿法:just like 2 gears mesh啮合together, considering the complex motion考虑到复杂的运动, normally we use gear hobbing 滚齿to manufacture(internal内部external外部standard标准corrected纠正. gears)form cutting仿形法: use a cutter , whose shape形状is like the gear's tooth space齿隙, to manufacture .for example use a disk milling cutter圆盘铣刀to mill a tooth space one by one. Advantage & disadvantage: cheap ,but low accuracy精度,low efficiency●the undercutting根切reason :the addendum circle of the cutter exceed超过the limit meshing拟合pointsolution解决: 1.add the number of tooth ,there're some lower limit for example ,spur gear 17, helical gear 14, bevel gear 12.e modified gears 变位齿轮●proper meshing conditions正确啮合条件m1=m2. α1=α2. if helical gears. β1=β1●the gearing equation without backlash无侧隙啮合方程with the purpose of prevent the impact(backlash)防止侧隙的目的. p'=s1'+s2' when standard gears +standard install安装, the meshing angle 啮合角α' should be equal to pressure angle α.For corrected gears use the equation to find the meshing angle α' to install.●Contact ratio重合度ε shows the average number平均数of the meshing gears at the same timeε is influenced by addendum coefficient h a' and z1 z w (the more the more) normally for a continuous and steady motion, ε should ≥1.3/1.4,but the maxima is1.98●Helical gear斜齿轮the normal plane法面---the transverse plane端面m n=m t cosβ. p n=p t*cosβ. but h'a=x t m t=x n m nNormally we use the parameter参数in the normal plane, but for the calculation of diameter we use m t. d=m t*zβ: external helical gear +-. internal helical gear ++the virtual gear: z v=z/cosβ(cube). can be used in calculation of. gear's strengthadvantage①more load bearing ability更大的承载能力②compact structure结构紧凑③steady平稳& less noise减少噪音disadvantage : axial force轴向力→ friction摩擦●Worm蜗杆& worm wheel蜗轮normally we use right handed右旋(left handed左旋) & ZA-wormp--linear pitchd--pitch diameter●proper meshing conditionsm t2=m x1=m.αt2=αx1.β2=γ--lead angle●have huge transmission ratio传动比i12=ω1/ω2=z2/z1. z1--the number of the threads less_more i_ low efficiency●advantage ①huge transmission ratio in 2 vertical axis不同轴②less noise & steady③self lock,when γ is smallDisadvantage ①low efficiency 效率低②produce heat发热③big axial force●bevel gear锥齿轮all the parameter参数& size is depended on the big endwe use back cone to simulate模拟(approximate) the shape外形of gear, for a simple calculationvertical垂直motion to transmitChapter 6 Other Mechanism●ratchet mechanism:棘轮机构driver rocker move back and forthfollower one way intermittent motion间歇式移动APP: feed back wheel of a bike exceed.●Geneva mechanism槽轮机构driver continually revolute持续的转动follower intermittent revolute间歇转动APP : film picture one by one show●universal coupling万向联轴器●rack & pinion齿条，齿轮5.电工基础 Fundamentals of Electrical EngineeringI this lesson , I studied circuit , basic concept , basic law , analyze circuit, sine alternating current circuit, three-phase circuit.Ohm`s lawElectric current is equal to voltage divided bu resistance.I=U/RKirchhoff `s current law (KCL)The total outflow and inflow current of a point is 0.I1+I2=I3Kirchhoff `s voltage law (KVL)U1-U2+U4-U3=0Series connection R=R1+R2Series connection R=R1R2/(R1+R2)Branch current methodUse KCL and KVL , we get can calculate the branched currents.Node-pair method结点电压法Sine alternating current circuitThree-phase circuitY connectionDelta connectionAbout electrotechnics, I learned circuit, basic concept定义, basic law, how to analyze circuit, sine alternating current circuit正弦交流电路 and three‐phase circuit, etc.●Ohm law欧姆定律I=E/(R+R')→R＞＞R' good load capacity好的承载能力●Kirchhoff's current law基尔霍夫电流定律In any moment, in one node Iin=Iout equal to 等于●Kirchhoff's voltage law基尔霍夫电压定律start from one point in a loop clockwise, Vup=Vdown绕一周，电压和为零。