专业知识库（按学科 / 专业 / 课程）
按学科门类筛选，可继续下钻到具体专业与课程；内容为各课程复习要点，用于面谈与笔试备考。
数值计算方法·课程总结笔记
核心内容
【数值计算方法】
一、工程问题的求解流程
实际问题 → 数学模型 → 数值方法 → 程序设计与上机计算 → 分析解、结果。
二、误差的产生
误差来源包括：模型误差、数据误差、截断误差、舍入误差（四舍五入）。例如小数位后面只能取一部分来计算，由此产生误差。
误差可避免，措施有：
1. 简化计算步骤；
2. 避免两个相近数相减；
3. 防止大数覆盖小数（例如 ?+1=? 的情形）。
三、插值
插值解决的问题：已知 n 个函数值的节点，如何求出该函数其它点的值。
主要方法：Lagrange 插值（拉格朗日插值）、Newton 插值（牛顿插值）。
Lagrange 插值：优点是容易写出公式，公式整齐，便于理解；缺点是当改变节点时需要重新计算，浪费时间。
Newton 插值：改变节点时不需要重新计算。
四、解方程的方法
1. 二分法；
2. 迭代法（使结果更加精确）；
3. 用 MATLAB 求解。
五、求积分的方法
又称 Newton-Cotes 公式，包括 Simpson 公式。
六、求常微分方程的初值
方法包括：Euler 方法、Runge-Kutta 方法。
参考：来源：WM_HDU-Len 课程总结.pdf｜专业：机械工程｜课程：数值计算方法
机械工程专业课程英文名称·课程总结笔记
核心内容
【专业课程英文名称】
一、机电一体化系统设计（Electrical and Mechanical System Design）
1. 课程定位：选修课，目标是建立机电一体化设计（mechatronics design）的整体思路，内容会综合其他课程知识。系统一般由动力源、电机（motor）等组成。本课程复习了以往知识，涉及装置原理、丝杆螺母（lead screw and nut）、步进电机（stepper motor）原理。
2. 丝杆螺母：实现旋转运动（rotary motion）到直线运动（linear motion）的转换。分为滑动丝杆螺母（sliding screw and nut）和滚动丝杆螺母（rolling screw and nut），两者分别介绍。
3. 步进电机控制：A、B、C 分别通电，通过程序控制，涉及脉冲（pulse）、转速（speed）、步距角（step angle）。
二、材料热处理及实验（Heat Treatment of Materials and the Experiment）
1. 课程定位：其他专业、选修课，对实验感兴趣，知识相同，涉及表面热处理（surface heat treatment）、加热炉（heating furnace）结构、实验。
2. 表面热处理：包括感应加热（induction heating）、火焰加热（flame heating）、激光加热（laser heating）、渗碳（carburizing）、渗氮（nitriding）、发黑（blackening）。
3. 加热炉：电阻热（resistance heating）式，有保温（insulation）、测温（temperature measurement），使用 NiCr 合金（镍铬合金）。
4. 实验：在 900℃ 下，测量硬度变化（hardness change），使用显微镜（microscope）。
三、机械原理（Mechanical Principle）
1. 课程定位：基础课，为机械应用力学知识打基础，涉及平面机构（planar mechanism）、凸轮机构（cam mechanism）、齿轮机构（gear mechanism）等。
2. 平面机构：至少 2 个构件（link），自由度（degree of freedom）公式 F=3n-2P_L-P_H，进行运动分析（kinematic analysis），如求 C 点速度。
3. 凸轮机构：基本知识、设计，包括基圆（base circle）、升程（rise）、回程（return）、升程角（rise angle），设计凸轮步骤：画基圆 → 升程回程 → 分角度 → 找位置 → 画连接。
4. 齿轮机构：传动比（transmission ratio）、基本知识、间歇齿应用，重合度（contact ratio）>1，造齿轮。
5. 轮系结构：定轴（fixed axis）、周转（epicyclic），传动比，判断方向。
四、互换性与技术测量（Interchangeability and Technology Measurement）
1. 课程定位：必修课，基本知识，尺寸公差（dimensional tolerance）、形位公差（geometric tolerance）、粗糙度（roughness）。
2. 基本知识：间隙配合（clearance fit）、过渡配合（transition fit）、过盈配合（interference fit），基孔制（hole-basis system）、基轴制（shaft-basis system）。
3. 尺寸公差：限制尺寸；形位公差：限制形状；公差、形位公差。
4. 粗糙度：Ra、Rz，检测方法（三个）。
五、机械制造工程（Mechanical Manufacturing Engineering）
1. 课程定位：必修，铣削方式（milling method）、切削方法（cutting method）、刀具（cutting tool）、切削速度（cutting speed）、进给量（feed）、深度（depth）、车床夹具（lathe fixture）、表面检测（surface inspection）。
2. 切削方法。
3. 切削速度、进给量、切削深度。
4. 车床（lathe）。
5. 夹具（fixture），提高效率。
6. 粗糙度：切削速度小，粗糙度小。
六、机械设计（Mechanical Design）
1. 课程定位：基础课，两种连接方法，机械传动（mechanical transmission），轴承（bearing）。
2. 螺纹连接（threaded connection）、键连接（key connection），三种螺纹连接，防松（anti-loosening），键连接。
3. 带传动（belt drive）、链传动（chain drive）、齿轮传动（gear drive），设计带传动。
4. 轴承：滑动轴承（sliding bearing）、滚动轴承（rolling bearing），面接触（surface contact），点接触（point contact），组成。
七、液压与气动（Hydraulics and Pneumatics）
1. 课程定位：选修课，液压系统（hydraulic system）组成，液压装置（泵、液压缸）、阀（valve），回路（circuit），液压泵（hydraulic pump）。
2. 泵：机械能（mechanical energy）→ 液压能（hydraulic energy），齿轮泵（gear pump）、叶片泵（vane pump）。
3. 辅助元件：油箱（oil tank）。
4. 执行部件：液压缸（hydraulic cylinder）。
5. 阀：流动方向、压力，单向阀（check valve）、换向阀（directional valve），压力：减压阀（pressure reducing valve）、溢流阀（relief valve）。
6. 基本回路：压力控制（pressure control）、速度控制（speed control）、液压系统。
八、机电传动与控制（Electromechanical Transmission Control）
1. 课程定位：选修课，电机运动规律（motor motion law），直流（DC）、交流（AC）电机，控制电机（control motor）、电机控制方法。
2. 直流电机：启动、改变速度，串电阻用于负载大，使用时间不长。
3. 交流电机：三相电机（three-phase motor），改变方向，Y-Δ 启动（Y-Δ starting），改变速度。
4. 步进电机（stepper motor）。
5. 串电阻启动。
九、工程材料及热加工（Engineering Materials and Thermo-processing）
1. 课程定位：选修，碳钢（carbon steel）钢铁机械性能（mechanical properties），晶体知识（crystal knowledge），铁碳合金相图（iron-carbon alloy phase diagram），热处理方法（heat treatment method）。
2. 刚度（stiffness）、强度（strength）、硬度（hardness），测试硬度方法。
3. 晶体组成物质规则，晶体↓强度、硬度↑，震动（vibration）。
4. 铁碳合金相图：反映各阶段，碳↑渗碳体（cementite）↑，一般 1.3% 以下。
5. 热处理：正火（normalizing）、退火（annealing）、淬火（quenching）、回火（tempering），表面热处理。低碳→正火，高碳→退火。
参考：来源：WM_HDU-Len 课程总结.pdf｜专业：机械工程｜课程：机械工程专业课程英文名称
工程图学（英文要点·大一大二）
核心内容
Basic Concepts:
In this course ,I mainly learned projection method ,three views, drawing of standard parts. And I can use Auto CAD,Auto inventor and Solidworks to draw or model parts.
Explanation of Concepts:
Projection methods:
There are two projection methods. They are central projection method (中心投影)and parallel projection method(平行投影). As for the parallel projection method,there are two kinds of it. One is orthographic projection method (正投影)and another is oblique projection method(斜投影).
The projection rays of central projection method are all come from one point above the workpiece.
The projection rays of parallel projection method are all parallel. As for the orthographic projection, the rays are vertical to the projection plane. But as for the oblique projection method, the projection rays are not vertical to the plane.
The drawing of standard parts:
In this part, i mainly learned about how to draw the bolt connection (螺栓连接)，the threaded connection(螺纹连接), and the expression of the gear.
The bolt connection The threaded connection
We can know how to draw the bolt connection and the threaded connection through the pictures. There is one key point we need to pay attention, in the picture 2 ,we can see the minor diameter of the bolt and the major diameter of the connceted part are used fine line, as for the major diameter of the bolt and the minor diameter of the connected part are used heavy line. So we can remember it as what we can touch using heavy line and we can not touch using fine line. But when the bolt is connected with the part with the threaded connection ,the heavy line is the major diameter of the bolt.
When we only draw a gear, we don’t have to draw the teech of it ,there are some simplified representation of it ,just like above picture. The addendum circle(齿顶圆) is using heavy line. The pitch circle (分度圆)is using dot dash line(点划线). The dedendum circle（齿根圆） is using fine line.
This is the expression of the meshing gears.
The pitch circle of two gears are tangent, and we don’t need to draw the dedendum circle.
And the addendum circle in the messing area is not need to express too.
（齿轮啮合区域两齿轮的分度圆相切，齿顶圆在啮合区域的部分不用表示。）
Drawing Software:
As for the drawing software ,they are very useful and convenient . We can use Auto CAD to draw two-dimensional diagram. And use inventor and Solidworks to build the three-dimensional model. And with the help of Solidworks,we can assemble the parts we built together into a mechanism. And of course ,we can get two-dimensional diagram from the three-dimensional model conveniently,if we use the software.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：工程图学
工程化学（英文要点·大一大二）
核心内容
Basic Concepts:
In this course, i mainly learned about theory of acid and alkali, redox reaction and the crystal structure of the materials.
Explanation of Concepts:
The theory of acid and alkali：
The matter ionizes(电离) in the water solution （水环境）,which produces positive ions and the ions are all H+（hydrogen ion氢离子）,then the matter called acid.
The matter ionizes in the water solution, which produces negative ions and the negative ions are all OH-（hydroxide ion氢氧根离子）, then the matter caled alkali.
The theory of acid and alkali illustrates that if put one kind of material in water solution, then the material will ionize, if all the positive ions are hydrogen ions，then the material is acid. If all the negative ions are all hydroxide ions ,then the material is alkali.
Redox Reaction(氧化还原反应):
If there is some change of the valence（化合价） of elements in the reaction ,then the reaction is called redox reaction.
The essence of the redox reaction is the electron gain and loss.
H2+Cl2=2HCl (chlorine hydride氯化氢)
In above reaction,each hydrogen ion loses one electron and each chlorine ion gains one electron.
CuSO4+Zn=ZnSO4+Cu
In above reaction, the cupric sulfate(硫酸铜) react with the zinc（锌） produce the zinc sulfate（硫酸锌） and the copper（铜）.
The valence in the sulfate radical(硫酸根) are not changed,so we can ignore the sulfate radical ions,and rewrite the chemical equation(化学方程式),like this:
The cupric ions react with the zinc get the zinc ions and the copper.
Then we can divide the equation into two part:
The cupric ion gain two electrons becoming the copper.
The zinc loses two electrons becoming the zinc ion.
The matter gaining electrons called oxidant (比如Cu2+,氧化剂), then what it becomes into called reduzate（比如Cu,还原产物）。Then we can call the process， that the oxidant gains electrons becoming into reduzate， reduction reaction. And the oxidant is reducted.
The matter losing electrons called reducting agent(比如Zn,还原剂)，then what it becomes into called oxidative product(比如Zn2+,氧化产物). Then we can call the process ，that the reducting agent loses electrons becoming into oxidative product ，oxidation reaction. And the reducting agent is oxidated.
Crystal Structure of materials:
This part is about the crystal structure of materials.
There are mainly three kinds of structure of the crystal:
The body-centeral cubic structure(体心立方晶胞): the average count of the atoms in each crystal cell of this kind structure is 8*1/8+1=2, and the minimum distance of the atoms is .
Such as 钾kalium 钠natrium 铁ferrum.
The face-centeral cubic structure（面心立方晶胞）: the average count of the atoms in each crystal cell of this kind structure is 8*1/8+6*1/2=4,and the minimum distance of the atoms is .
Such as 铜cuprum 金aurum 银silver.
The hexagonal closed packed structure(六方密堆晶胞):the average count of the atoms in each crystal cell of this kind structure is 12*1/6+1/2*2+3=6, and the minimum distance of the atoms is EMBED Equation.KSEE3 .
Such as 镁magnesium 锌zinc 钛titanium.
The paraffin wax (石蜡)and glass（玻璃） are non crystal.
We can identify the crystal and non crystal by the melting process. The crystal has melting point . When the crystal melts, it will melt when the temperature of it get the melting point. But the non crystal has no melting point. When the non crystal melts, it will be softer with the increasing of the temperature until it become into liquid. The atom arrangement in crystal is regularly, but it is not regularly in non-crystal.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：工程化学
高等数学（英文要点·大一大二）
核心内容
Basic Concepts:
In this course , I mainly learned about the derivation(导数),differential(微分), definite integral(定积分) and indefinite integral(不定积分).
Explanation of Concepts:
Derivation :
The dirvative of one point of the function is the slope of the point of the function. For example,
F(x)=2x^2+1; the dirvative of F(x) is F’(x)=4x
so when we want to know the slope of one point on the function, we just have to bring the abscissa（横坐标） of the point in to the F’(x).
And in this part, I learned how to get the dirvative of some complex function,
for example,
Differential:
The differential is very similar to the derivation. We just have move the dx to the right of the equality sign. And the derivation becomes into the differential.
Definite integral:
The definite integral is for finding the area between the function f（x）and the abscissa axis(横坐标轴) in the interval [a,b].
Indefinite integral:
In indefinite integral , the original function is
not definite ,because of the constant unknowns.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：高等数学
理论力学（英文要点·大一大二）
核心内容
Basic Concepts:
This course includes three parts: statics(静力学),kinematics(运动学), dynamics(动力学).
Explanation of Concepts:
Statics:
Hooke principle: in the range of the elastic deformation, the change length is proportionate to the force acting on the object.
F=-Kx K is the modulus of elasticity. x is the deformation length.
In the statics part, i mainly learned about the three forces balance concurrent theorem(三力共点平衡原理). And the force analysis which is based on the theorem.
Three forces balance concurrent theorem: there are three forces acting on one rigid body(刚体), and they balance each other, if two active lines of forces intersect, then these three forces are in the same plane and the active line of the third force pass through the point of concurrent.
Because we can regard any two of the three forces as a whole, then we can find out the join force of them, then the active point of the join force must be the concurrent of the two force. The rigid body is in the balance state, so the third force must be balance with the join force of the two forces. So the active line of the third force must be the same as the join force, and they are equal and opposite.
In left picture, in the structure, AB is a beam(横梁), CD is a pole(杆), A,C,D is hinges(铰链), the length of AC is equal to the length of BC(AC=BC), the angle ACD is 45 degree(∠ACD=45°), the F is ten thousand newton(F=10kn), and acts on the point B . Ignore the gravity of the beam and pole. So ask the force acting on the point A and on CD pole.
First , we discuss about the CD pole. There are two only two force acting on it and the two forces are along the direction of CD, and they are equal and opposite.
Then we discuss about the beam AB. There are three forces acting on it. One is the F, one is from the pole CD and the last one is the force acting on point A, and these three forces are at balance state. According to the three forces balance concurrent theorem, we can know their active lines through the same point, and we know that AC=BC, so we can find out the θ, then we know the F=10kN, so we can know the FA, then the FC can be found. As for the F’C, the F’C and FC are the force and counter force(作用力和反作用力), they are equal and opposite. Then the FD is known.
Above is one of the application of the three forces balance concurrent theorem.
Kinematics:
When we learn the movement of objects, for expressing the movement, we usually choose several reference system(参考系), usually we call the coordinate system (坐标系), which is fixed on the earth, the fixed reference system（定参考系）. And other reference systems ,which are moving on the earth, are called moving reference system.
Velocity(速度)：the velocity of point ,which is based on the fixed reference system ,is called absolute velocity(绝对速度). Based on the moving reference system is called relative velocity（相对速度). The velocity of moving reference system which is based on the fixed refenence system is called following velocity(牵连速度).
So the composite motion of points is that at one time , the absolute velocity is the vector sum(矢量和) of the relative velocity and the following velocity.
For example,if you jump on a running train,
The velocity of your jumping is the relative velocity. The velocity of the train is the following velocity. And the vector sum of the relative velocity and the following velocity is the absolute velocity.
As for the accelerated velocity, the method of calculation of it is the same.
Dynamics:
In this part , the key point is the theorem of kinetic energy(动能定理) in dynamics.
First, this part is based on the energy conservation principle(能量守恒原则)，then we know that the force is the reason that the object change its motion state, in this process, the energy of the object is changing ,too. So the theorem of kinetic energy is used for finding the changing energy or finding the velocity after or before the energy changing.
The formula is
The W12 is the work of the force acting on the object. The V1 is the velocity before energy changing, and the V2 is the velocity after energy changing.
It is a link which connects the energy and the velocity of the object.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：理论力学
材料力学（英文要点·大一大二）
核心内容
Basic Concepts:
In this course i learned the pole axial tensile and compression deformation(杆的轴向拉伸与压缩), pole torsion deformation(杆的扭转变形), pole shear deformation(杆的剪切变形) and pole bending deformation(杆的弯曲变形).
Explanation of Concepts:
In this course we don’t regard the objects as rigid body, instead, we think all the objects can deform when they bear different kinds of force.
There are four forms of pole deformation: pole axial tensile and compression deformation(杆的轴向拉伸与压缩), pole torsion deformation(杆的扭转变形), pole shear deformation(杆的剪切变形) and pole bending deformation(杆的弯曲变形).
Pole axial tensile and compression deformation:
When the pole bear force which is along the direction of the axial of the pole, the pole will be compressed or stretched.
In this part i can draw axial force diagram in this chapter. For example,there is a pole like following,
We make it into 3 parts 1-1,2-2,3-3, then we discuss the pole separtately.
Because every part of the pole is in the balance state, so we can get:
It rules that the compression force(压力) is negative and the tensile force（拉力）is positive. So the axial force diagram is
Pole torsion:
In this chapter, i can draw torque diagram of a pole. For example , as the picture, the input power of driving wheel A is 36kW, the output power of the driven wheel B, C, D is PB=PC=11kW, PD=14kW, the rotate speed of the axle is n=300 r/min(300 rotates pear minute).
First we should calculate the torsion couple on each wheel,
The system is in balance, then we make it into three sections, we choose the B→D direction is the forward direction. Look against the forward direction, if the direction of torsion is clockwise, it is negative , if it is not, it’s positive.
T1=-350Nm T2=-700Nm T3=446Nm
So we can get the torque diagram.
Pole shear deformation and bending deformation:
I learned to draw the shear force diagram(剪力图) and bending moment diagram(弯矩图) in this chapter.
For example , there is a beam, and there is uniform load on it. The length of the beam is l.
First we need to know the force on point A and point B.
FA=FB=ql/2
Then we suppose the shearing force on the cross section is downward, and the shearing force FQ which is why the pole ,which is from the A to the acting point of FQ, in balance, so we can get the formula:
FQ=FA-F=ql/2-qx
So according to the formula, we can get the shearing forces of every points on the pole ,then we can get the shearing force diagram:
Then we suppose the bending moment is anticlockwise and it’s positive. We suppose the point ,which the FQ acting on ,is fixed. The point A is not fixed. Then we suppose at the acting point of FQ has a torque M making the left part of the acting point of FQ in balance, we call the M bending moment. Then we can get the formula of the M is: .
Then we can get the bending moment diagram,
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：材料力学
线性代数（英文要点·大一大二）
核心内容
Basic Concepts:
In this course, I mainly learned about the calculation of the determinant(行列式) and the matrix（矩阵） .
Explanation of Concepts:
The calculation of the determinant:
For example:
Above are the formula, and we should remember it.
If the order(阶数) of the determinant is higher then three, then we should make the order become lower until it is three,then we can calculate. For example,
The calculation of the matrix:
There are three main calculation of the matrix: addition of the matrix, subtraction（减法）of the matrix and the multiplication of the matrix.
As for the addition and the subtraction, they only exist between the calculations of the same type of the matrices. For example:
But the multiplication of the matrix exists between the different types of the matrices. For example:
The result is a three rows three columns matrix.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：线性代数
概率论与数理统计（英文要点·大一大二）
核心内容
Basic Concepts:
In this course, I mainly learned conditional probability multiplication formula(条件概率计算方法), geometric probability model(几何概型), and mathematical statistics(数理统计).
Explanation of Concepts:
Conditional probability multiplication formula:
P(AB)=P(B)P(A|B) P(AB) is equal to P(B) times P(A|B)(the probability of A given B).
P(AB) is the probability that event A and event B happen together.
P(B) is the probability that event B happens.
P(A|B) is the probability that the event A happens, when the event B has already happened.
So by this formula, we can get the probability of any part in the formula if we know the other two parts.
Geometric probability model:
We can use some geometric methods to solve the probability problem. If there are two variables, 0<x<1, 0<y<1, then we want to know the probability of x+y<1. It’s a geometric probability model.
First , we should change the form of the inequality.
x+y<1 changes into y<1-x.
Then we know that what we want is the part beneath the line of y=1-x.
And considering the conditions 0<x<1 and 0<y<1, we can draw a diagram.
So the square is the area of 0<x<1 and 0<y<1, and the line through point (1,0) and (0,1) is the line of y=1-x, and the shadow area S is the area of y<1-x, we can get from the diagram that the area of S is half of the area of the square. So the probability of x+y<1 under the condition of 0<x<1,0<y<1 is 1/2.
According to the example, we can know that if we use the geometric probability model, we can solve some kinds of probability problem very easily.
Mathematical statistics:
Mathematical statistics is to collecting, processing and analysising the data, which is get form the tests and experiments. And then we can get some regular conclusions. For example, if we throw a dice for 20 times,
number 1 2 3 4 5 6 times 2 4 1 3 3 7 Then we can see the results clearly by this chart and we can get the average number and other things, like
The average of the number we got is
The variance(方差) is
The standard deviation(标准差) is the square root of the variance
Of course , if we throw the dice for many times and there are no problem with the dice, the probabilities of each number appearing are equal, and are all 1/6.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：概率论与数理统计
机械原理（英文要点·大一大二）
核心内容
Basic Concepts:
In this course ,we learned about the structure analysis of planar mechanism(平面机构结构分析), planar linkage mechanism(平面连杆机构), the cam mechanism(凸轮机构) and its design, gear mechanism(齿轮机构), gear trains(轮系) and calculation of its transmission ratio.
Explanation of Concepts:
Machinery（机械） include machine（机器） and mechanism(机构).
Structure analysis of planar mechanism:
In this chapter, i learned the lower pair(低副), the higher pair(高副) and degree of freedom of planar mechanism.
Direct contact and the movable connecting of two components is called kinematic pair.
Surface contact kinematic pair is called the lower pair. The revolute pair(转动副) and the sliding pair are lower pair.
Point contact and line contact kinematic pair is called higher pair. The gear pair and cam pair are higher pair.
The formula of the degrees of freedom of planar mechanism is
n —— the number of components, which can move;
—— the number of the lower pairs;
—— the number of the higher pairs.
For example,
This is a cam mechanism. It is composed of two moving parts, the A is push rod and the B is cam. The 1 is a sliding pair and the 3 is a revolute pair, they are all lower part. But the 2 is a line contact kinematic pair, it is a higher pair. So the degree of freedom is
When we calculate the degree of freedom, we should pay attention to three mechanisms.
local degree of freedom(局部自由度)： the degree of freedom which is unconcerned with the main movement is called local degree. When we calculate the degree of freedom of mechanism with local degree, we should delete the local degree first.
Compound hinge(复合铰链)：there are three members(构件), two of them have revolute pairs with the third one. When this happens, the number of the revolute pairs is the number of the members minus one.
Virtual constraint(虚约束)：we can regard
the virtual constraint as the repeated constraint,
it is existing for ensuring the strength of
the mechanism. When we calculate the degree
of freedom, we should ignore the virtual constraint.
Low pair replaces the high pair(高副低代):
For solving the problem conveniently, we can replace the high pair with the low pairs. But the degree of freedom, instantaneous velocity and instantaneous acceleration of the replacing institution must be the same as the primary institution.
Look at the above picture , the original mechanism is composed of two wheels, the kinematic pair between the two wheels is a line contact kinematic pair. It is a high pair. And we can replace it with the planar linkage mechanism. The length of the O1O2 is equal to the sum of r1 and r2.
Planar linkage mechanism :
I learned about the crank rocker(曲柄摇杆) , crank block(曲柄滑块) and the condition of the sum of the bar length(杆长之和条件).
The condition of the sum of the bar length:
The sum of the length of the shortest bar and the longest bar is not larger than the sum of two other ones.
If a revolute pair wants to be a full rotation pair , the nearest bar must be the shortest and these 4 bars must meet the condition of the sum of the bar length.
If the institution meet the condition:
If the shortest bar is the rack(机架), it is double crank mechanism.
If the nearest bar of the shortest bar is the rack ,it is crank rocker mechanism.
If the bar against the shortest bar is the rack, it is double rocker mechanism.
If the institution can not meet the condition of the sum of the bar length, then it is always a double rocker mechanism, no matter which bar is the rack.
Geometric features of planar linkage mechanism:
Extreme position angle(极位夹角)：
In the process of cranks rotation, there are twice that the crank and the bar next to it on the same line. The angle between the crank at these two times is called the extreme position angle. The two places of the crank is called the extreme position(极限位置). And extreme position angle is in the range [0°,180°].
The pressure angle and the transmission angle(压力角和传动角)：
The pressure angle: the acute angle(锐角) between the direction of force F and the direction of the velocity of the follower is named pressure angle. Like the angle α.
The transmission angle is the complement angle(余角) of the pressure angle. Like the angle γ.
The larger the transmission angle is , the better for the institution. Because
The γ is changing with the movement of the bars, but for keeping the transmission work well, we usually keep the γ more than 40°.
The dead point position(死点位置):
In this picture, the follower and the next bar is on the same line, the transmission angle is zero, this position is called the dead point position. We should avoid institutions to start at the dead point position ,because this moment the Ft is zero.
The cam mechanism and its design:
Classification of cams according to the shapes:
Dish cam wedge cam(translating cam) cylindrical cam (盘形凸轮) (移动凸轮) (圆柱凸轮)
The follower motion law(从动件运动规律):
The angle AOD(>180°) is called near angle of repose(近休止角).
The angle B’OB is called motion angle for rise travel(推程运动角).
The angle BOC is called far angle of repose(远休止角).
The angle COD is called motion angle for return travel(回程运动角).
This is the diagram of the motion of the follower , h is the distance of the follower moving.
The design of the dish cam:
If we know the base circle and the follower motion diagram, we can design the cam contour. Like the left picture.The base circle is given and the line of follower is through the center of the base circle. If we know the diameter of the wheel on the follower and the follower motion diagram , we can find out the theoretic contour curve. Then we can get the actual contour curve.
Gear mechanism:
I learned types of gears , involute gear（渐开线齿轮） , the size of the standard gear, the transmission ratio of the gears.
The ratio of instantaneous angular velocity(瞬时角速度) of the two gears is called transmission ratio（传动比）.
There are circular gear and non-circular gear.
External meshing gear mechanism and internal meshing gear mechanism.
The external meshing gear mechanism. in this mechanism ,the two meshing gears rotate in opposite directions
The internal meshing gear mechanism. in this mechanism ,the two meshing gears rotate in the same direction.
Pinion and rack mechanism. In this mechanism, it can transform the rotate movement into the linear movement.
Space gear mechanism. In this mechanism, it can change the rotating plane of the rotate movement.
Worm gear mechanism. In this mechanism, it can change the rotating direction of the rotate movement. And the transmission ratio of this mechanism can be very large.
I also learned that the ratio of instantaneous angular velocity of the two gears is called transmission ratio.
And the relative velocity instantaneous center is called meshing pitch point(啮合节点).
The moment locus(瞬心) of pitch point on the gear is called pitch circle(节圆).
Transmission ratio :
the are the pitch circle radius.
The involute gear: choose a point on a straight line, then make the line rotate around a circle, the counter of the point is a involute. The pressure angle of the involute gear never change.
The correct meshing condition of the gear transmission is the modulus(模数) and the pressure angle of two gears must be equal.
Basic parameters of standard gear:
modulus（模数）: it is a very basic parameter of the gear. m for short.
the p is the tooth pitch(齿距). Tooth pitch is equal to the sum of tooth thickness and space width.
For determining the gear geometrical size of each point, we choose a circle as the standard of the calculation, this circle is call the reference circle(分度圆).
name symbol formula Pitch diameter
(分度圆直径) d
Addendum
（齿顶高） Dedendum
(齿根高) whole depth
（齿全高） h Tip diameter
(齿顶圆直径） Root diameter
(齿根圆直径)
Pitch(齿距) p Tooth thickness
(齿厚) s space width
(齿槽宽) e Base diameter
(基圆直径)
Centre-to-centre spacing
(中心距) a Bottom clearance
(顶隙) c z is the tooth number(齿数).
is the addendum coefficient(齿顶高系数), the standard one is 1, the short one is 0.8.
is the bottom clearance coefficient(顶隙系数)， the standard one is 0.25, the short one is 0.3.
x is the modification coefficient, if the gear is not modified, x=0.
the standard of the pressure angle is 20 degree.
In order to prevent the undercutting(根切) when the gears are meshing, the tooth number must larger than 14.
Gear failure form:
1,tooth breakage(轮齿折断); 2, tooth surface wear(齿面磨损);
3,tooth surface pitting(齿面点蚀);4,tooth surface gluing(齿面粘合).
Gear train and its transmission ratio:
The classification of gear train:
There are two types of gear trains, ordinary gear train and epicyclic gear train（周转轮系）.
The ordinary gear train: each axes of the gears are fixed.
The epicyclic gear train : exist axes of the gears are not fixed. Like the gear4.
The transmission ratio of fixed axis gear train:
The product of teeth number of all driven gears(从动轮齿数乘积)
iAB= -------------------------------------------------------------------------------
The product of teeth number of all driving gears（主动轮齿数乘积）
For example,
The gear 1 is the driving wheel, so the 2 is the driven wheel, then the 2’ is the driving wheel ,the 3 is the driven wheel. According to the formula we can get:
As for the direction of the rotate of the gears , we can analysis each pair of gears to get it.
If the gear train is a epicyclic gear train, then we want to find out the transmission of the gear train ,we can just add a im, which is a relative transmission ratio of the planet wheel. Then we can bring the im into the formula, we can get the final transmission ratio.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：机械原理
机械基础综合实验（英文要点·大一大二）
核心内容
Basic Concepts:
In this course , we have made experiment in the lab of our school, the topic of the experiment is to measure the geometric parameter of the turning tool.
Explanation of Concepts:
The aim of the experiment
Learn the method of measuring the geometric parameter of the turning tool and using of the measuring device;
Enhance the definition and understanding of tool geometry;
Draw the mark angle of the 45° external circular tool.
2. The content and requirements of the experiment
(1) Measure the rank angel(前角) ,clearance angle(后角), major cutting edge angle(主偏角), minor cutting edge angle(副偏角)，tool cutting edge inclination（刃倾角）.
(2) Everyone measures two cutting tool, one is 45°external circular tool, another is cutting off tool.
(3) according to the result of the measuring, draw the angle diagram of the 45° external circular tool.
3. Device
CLY-1 type angulometer of the cutting tool(车刀量角仪).
The structure and working principle of the angulometer of the cutting tool
When manufacturing the cutting tool, we all regard the plane which is parallel to the bottom of the cutting tool rod as the base plane. So when we measuring the cutting tool , we should also be based on the bottom.
The working principle : all the geometric parameter are measuring in the coordinate planes(坐标平面) of the cutting tool, include base plane（基面）, cutting plane (切削平面), orthogonal plane(正交平面).
The step of the experiment
Measuring the angle in base plane Pr
There are major cutting edge angle Kr(主偏角) and minor cutting edge angle K’r(副偏角) in the base plane. First , we should put the tool on the shoe plate next to the guide block, and che tool nose(刀尖) towards to the front plane of the measuring pointer. Adjust the shoe plate to make the major cutting lip(主切削刃) next to and parallel with the front plane of the measuring pointer, and now read the reading on the dial scale 1. The reading is the degree of the major cutting edge angle Kr. Then adjust the shoe plate again, to make the minor cutting lip(副切削刃) next to and parallel with the front plane of the measuring pointer, now read the reading on the dial scale 1. The reading is the degree of the minor cutting edge angle K’r.
Measuring the angle in orthogonal plane Po
Rank angle γ0 : put the tool on the shoe plate next to the guide block. Then make the bottom of the measuring pointer contact with the rake face(前刀面), now the reading on the dial scale 2 is the angle of the rank angle.
Clearance angle α0 : put the tool on the shoe plate next to the guide block. Through adjusting the shoe plate and the handwheel , make the minor flank is parallel to the front plane of the measuring pointer. Then read the reading on the dial scale 3. Then the reading of the dial scale 3 is the degree of the clearance angle α0.
Measuring the angle in cutting plane (Ps)
There are only the tool cutting edge inclination(刃倾角) λs in the cutting plane. First , we should make the major cutting lip is next to and parallel to the front plane of the measuring pointer. Then adjust the measuring pointer to make the bottom of it is parallel to the major cutting lip. Then read the reading on the scale 2. The reading is the degree of the tool cutting edge inclination（刃倾角）.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：机械基础综合实验
电工技术与电子技术基础（英文要点·大一大二）
核心内容
Basic Concepts:
In this course, I learned Kirchhoff’s law(基尔霍夫定律), two models of the power supply（两种电源模型）, Thevenin’s theorem（戴维宁定理）, Norton’s theorem（诺顿定理） and series connect and Parallel connect of resistances（电阻的串并联）.
Explanation of Concepts:
Kirchoff’s law:
There is a Kirchhoff’s current law(基尔霍夫电流定律) and a Kirchhoff’s voltage law（基尔霍夫电压定律）.
Kirchoff’s current law:
At one time and at any mode in an electrical circuit , the sum of currents flowing into that mode is equal to the sum of current flowing out of that mode.
Left is an electrical circuit. There are two power supplies and three resistances. Then I3=I1+I2, the current flowing through R3 is equal to the sum of current flowing through R1 and R2.
Kirchhoff voltage law:
At one time, and along one certain direction , the sum of the electrical voltage around any closed network is zero.
When the voltage goes down , it is positive. When the voltage goes up , it is negative. We calculate the voltage along the direction of anticlockwise like left picture. And we can get U1-U2+U4-U3=0.
Series connect and parallel connect of resistances:
The the equivalent resistance(等效电阻) of the series resistors(串联电阻) is equal to the sum of the resistances which are in series. Like left picture, R=R1+R2.
The equivalent resistance of the parallel resistors(并联电阻) is equal to the reciprocal of the sum of the reciprocal of the resistances which are in parallel. Like left picture,
Two models of the power supply:
I learned two models of the power supply, the voltage source model and the current source model.
Any source supplies have electromotive force(电动势EMF) and internal resistance(内部电阻). We often separate them when we calculate.
The voltage source model:
The A is the ideal voltage source, the voltage of it is always E.
The B is the internal resistance, and the resistance of it is R0.
The RL is the load resistance, it is like the power consumption elements.
The I is the current in this electrical circuit.
Above is the voltage source model. The ideal voltage source and the internal resistance are in series. The voltage of this kind of power supply is U=E-R0I.
The current source model:
In this model, the A is the current source, and the current of it is always Is. The R0 is the internal resistance, and it is parallel with the current source. The RL is the load resistance. The U is the load voltage . The current through RL is I=IS-U/R0.
These two kinds of model can transform into each other.
The Is is equal to E/R. We can use this kind of change to solve problem more conveniently.
Is=E/R
Thevenin’s thorem:
The active two-terminal network(有源二端网络)：it is part of the circuit which contains the power source. It can be simple or complicated.
The thevenin’s thorem is that any combination of voltage sources, current sources and resistors with two terminals(终端) can be equivalently replaced(等效替代) by a single ideal voltage source and a single series internal resistance.
The Norton’s theorem:
Any active two-terminal network can be equivalently replace by an ideal current source in parallel with a single internal resistor R.
These two theorems are convenient for us to solve the circuit problem and to calculate.
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：电工技术与电子技术基础
电子技术（英文要点·大一大二）
核心内容
Basic concepts:
In this course , I learned diode(二极管), triode(三极管), basic amplifying circuit(基本放大电路) and basic logic gate circuit(基本逻辑门电路).
Explanation of Concepts:
Diode and triode:
Diode:
Semiconductor(半导体): there are two types of semiconductor, N-type semiconductor and P-type semiconductor.
N-type semiconductor: usually we put some phosphorus(P磷) into the silicon(硅) crystal. There are five electrons in the outside of the P. And there are four electrons in the outside of the silicon. So the fifth electron of the phosphorus isn’t stable. So there are many free electrons in the N-type semiconductor.
P-type semiconductor: usually we put some boron(B 硼) into the silicon crystal.
There are three electrons in the outside of the B . And there are four electrons in the outside of the silicon. So there are many holes in the p-type semiconductor and other electrons will flow to fill the holes. Then the current can come into being.
The surface of the N-type semiconductor and the P-type semiconductor is called P-N junction(PN结).
If we add the forward voltage on the P-N junction, then the free electrons of N-type semiconductor will flow to the holes of P-type semiconductor, then the P-N junction is conducting.
But if we add the backward voltage on the P-N junction , then the P-N junction is not conducting.
Above is the principle of diode. If we add the electrode lead on P-N junction. It’s the diode.
This is the volt-ampere characteristics curve(伏安曲线). We can see, the forward voltage is conducting and the backward voltage is not conducting. But if the backward voltage is too large, the diode will be breakdown(击穿), and the it will be conducting. The minimum voltage when the diode is breakdown is called the breakdown voltage. And we can see , there is a dead zone voltage.
When the voltage is lower than the dead zone voltage , the diode is not conducting as well.
Triode:
The triode has amplified action(放大作用). There are two types triodes: N-P-N type and P-N-P type. Following is the basic structure.
The N-P-N type is used more. IC=βIB, β is only a ratio. As for the N-P-N type, the voltage of the base is highest, the emitter is the lowest. But the P-N-P type ,the voltage of the emitter is the highest, the base is the lowest.
Basic amplifying circuit:
Usually we use a voltage source represent the AC(alternating current) signal source. Left picture is the common-emitter AC amplifying circuit diagram. We use the current amplification function of the triode.
The collector voltage Ucc supplies the energy for the output signal and makes sure the collector junction on reverse bias(反偏).
The collector load resistance Rc turns the current change into the voltage change to realize the voltage amplification.
Bias resistance RB makes the emitter junction forward bias(正偏), and supplies the suitable base current(基极电流) IB.
The coupling capacitance (耦合电容)C1 and C2 make the signal source, amplifying circuit and the load resistance no DC(direct current直流) link and make sure that the AC signal can get through the circuit.
Application: audio power amplifier(扩音器)
Basic logic gate circuit:
The logic circuit belongs to the digital circuit(数字电路). And what we learned before is artificial circuit(模拟电路).
The difference between digital circuit and artificial circuit is the signal of artificial is continuous changing in time and numerical value. But the signal of digital circuits is not continuous changing, it is the pulse signal(脉冲信号). It is “1” or “0” to judge the connect or disconnect.
Following are some basic logic gate circuit.
Logic gate AND-gate OR-gate NOT-gate NOT-OR gate NOT-AND
gate symbol formula Y=A·B Y=A+B Y=Ᾱ Y=
And there are some calculate laws of the logic gate,
Crossover law(交换律):
Binding law(结合律):
Distribution law(分配律):
The truth table for AND-gate:(Y=A·B)
A B Y 1 1 1 1 0 0 0 1 0 0 0 0
参考：来源：大一大二资料（英文.doc｜专业：机械工程｜课程：电子技术
机械设计课程设计（英文要点·大三大四）
核心内容
Major: Mechanical Design, Manufacturing and Automation
The third year
Basic concepts:
This course is the course exercise of the Mechanical Design, it is to design a two stage reducer.
Explanation of concepts:
01905The steps of design:
Make the requirements clearly: We should make the requirements clearly. The requirements are:a、this is a two stage reducer of a winding drum(卷筒), the speed of the winding drum is 1.2m/s, force of it is 2.7kN, diameter of it is 320mm. And we should choose the Y type three phase asynchronous motor(三相异步电机), and it should be closed type(封闭式).
Calculate the basic data of the reducer: we have know the basic requirements of the reducer, then we should calculate the basic data, like the power of the reducer, the transmission ratios and the torque of the axes. The design have given to my teacher after the course exercise, so i can’t find the date of this part. But i can present you some key data of this part. The transmission ratio between the motor axis and the first gear axis is 3. The transmission of the gear axes is 13.50. The three phase asynchronous motor I chose is the Y132S1-2 type, the speed of it is 3000r/min, and the working speed is 2900r/min.
Choose belt of the belt transmission: according to the basic data we have got, we can choose the belt of the belt transmission. First the belt transmission ratio is 3, and then we can decide the diameter of the pulleys. The process of choosing the pulleys is mainly according the standard requirements. In another word, it is chose through look-up table. All the data of the pulleys and the belt has standard, we just have to choose the fit ones. Finally, the first pulley’s diameter is 90mm, the second one is 270mm. And we choose the Z type belt, and using 3 belts. The distance of two pulleys is 700mm.
Calculate of the gears: first we should make sure the transmission ratio of the first stage and the second stage of the gear transmission. According to the formula , we can get that the first stage transmission ratio is 4.27, and the second stage is 3.16. Then we can choose the number of the tooth of the gears. Then we should find out if the endurance bending strength and the Contact fatigue strength meet the requirement. If it is OK, then we can continue to calculate the next gear. Finally, the data of the gears is: z1=25, z2=104, a1=135mm, b1=65mm, b2=60mm,α=20°; z3=30,z4=91, a2=155mm,b3=85mm,b4=90mm,α=20°. And the modulus is 2.
We design the shape of the axes: we have get the data of the gears, then we can use look-up table to find the data of the axes, I can’t find the data about the axes now.
At last we have to choose the auxiliary equipment, such as the air hole bolt, the flow nipple, the bearing and the coupling.
All the things have been chosen, then we should draw the assembly drawing and write the instructions of the two stage reducer.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：机械设计课程设计
专业导论（英文要点·大三大四）
核心内容
Basic concepts:
This course is mainly about the introduce of our major, it is for telling us what we are learning for , what we can do after graduation, and the future of our major. There is nothing important.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：专业导论