📚 CAIE Year 12 Engineering: A Glossary & Mnemonics Guide | CAIE 12年级工程学：词汇术语速记指南
In CAIE Year 12 Engineering, a strong command of subject‑specific terminology is the key to unlocking both theoretical understanding and practical design work. This guide compiles the most frequently tested technical terms across mechanics, materials, electronics, thermodynamics, manufacturing, and design communication. For each term we provide a clear definition, a contextual example, and a memorable shortcut – an acronym, visual cue, or simple analogy – to speed up recall during revision and in the exam hall.
在 CAIE 12 年级工程课程中，牢固掌握学科术语是理解理论知识、开展设计实践的关键。本指南汇集了力学、材料、电子、热力学、制造与设计沟通等模块中最常考查的技术词汇。每个术语都配有清晰的定义、背景示例和简短的记忆诀窍——一个缩略词、一幅视觉提示或一个简单类比——帮助你在复习和考试中快速回想。
1. Materials and Their Properties | 材料及其性质
Tensile Strength: The maximum stress a material can withstand while being stretched or pulled before necking begins. Think of a tug‑of‑war rope – tensile strength is the point just before individual fibres start to snap.
抗拉强度： 材料在被拉伸或拉拔时，开始颈缩前能承受的最大应力。想象拔河比赛中的绳子——抗拉强度就是个别纤维即将断裂前的那个瞬间。
Yield Strength: The stress at which a material begins to deform plastically. Beyond this point the material will not return to its original shape. Memory aid: ‘yield’ means ‘give in’; the material surrenders its elastic behaviour.
屈服强度： 材料开始发生塑性变形的应力值。超过此点，材料不会恢复原状。记忆法：’yield’ 意味着‘让步’；材料放弃了它的弹性行为。
Ductility vs Malleability: Ductility is the ability to be drawn into a wire (think ‘duct’ → conduit); malleability is the ability to be hammered into thin sheets (think ‘mallet’). Both are forms of plastic deformation but in different directions.
延展性与可锻性： 延展性指被拉拔成丝的能力（联想 ‘duct’ → 管道）；可锻性指被锤打成薄片的能力（联想 ‘mallet’ 木槌）。两者都是塑性变形，但受力方向不同。
Hardness vs Toughness: Hardness resists indentation or scratching (diamond is hard); toughness absorbs energy up to fracture (rubber is tough, not hard). A quick mnemonic: ‘Hard to scratch, Tough to snap.’
硬度与韧性： 硬度抵抗压痕或划伤（金刚石硬）；韧性吸收能量直至断裂（橡胶韧而不硬）。速记：’Hard 怕抓，Tough 怕掰’。
Fatigue: The weakening of a material caused by repeatedly applied loads, often leading to sudden failure below the tensile strength. Visualise bending a paperclip back and forth until it breaks.
疲劳： 材料在反复载荷作用下逐渐弱化的现象，常导致低于抗拉强度的突然失效。想象来回弯折回形针直至折断。
Creep: Slow, permanent deformation under constant stress, especially at high temperatures. Think of old lead pipes sagging over decades.
蠕变： 在恒定应力（尤其高温）下缓慢发生的永久变形。想象旧铅水管经过几十年慢慢下垂。
2. Forces, Stress, and Strain | 力、应力与应变
Stress (σ): Force applied per unit area. Formula: σ = F / A. Units: pascals (Pa) or N⋅m⁻². Imagine standing on one leg: the stress on your foot bones is higher than on two.
应力 (σ)： 单位面积上施加的力。公式：σ = F / A。单位：帕斯卡（Pa）或 N·m⁻²。想象单腿站立时脚骨承受的应力比双腿站立时更大。
Strain (ε): The extension per unit original length – a dimensionless ratio. ε = ΔL / L₀. When you stretch a rubber band, the increase in length divided by its original length gives the strain.
应变 (ε)： 单位原始长度的伸长量——无量纲比值。ε = ΔL / L₀。当拉伸橡皮筋时，伸长量除以原始长度即为应变。
Young’s Modulus (E): A measure of stiffness: stress divided by strain in the elastic region. E = σ / ε. Steep slope on a stress‑strain graph means stiff material. ‘E for Elastic!’
杨氏模量 (E)： 刚度度量：弹性区域内应力除以应变。E = σ / ε。应力‑应变图上斜率大意味着材料刚度大。’E 代表弹性！’
Factor of Safety (FoS): The ratio of ultimate tensile strength to allowable stress. FoS = UTS / Allowable stress. Think of an elevator rated for 1000 kg but tested to 5000 kg – a safety margin of 5.
安全系数 (FoS)： 极限抗拉强度与许用应力的比值。FoS = UTS / 许用应力。想象一部额定载重 1000 kg 的电梯实际测试到 5000 kg——安全余量为 5。
3. Structural Mechanics | 结构力学
Moment of a Force (Torque): The turning effect about a pivot. Moment = Force × Perpendicular distance. Unit: N⋅m. Use the mnemonic ‘F×d – push far from the hinge to open a heavy door easily.’
力矩（转矩）： 绕支点的转动效应。力矩 = 力 × 垂直距离。单位：N·m。记住 ‘F×d——推门时离合页越远越省力’。
Equilibrium: A state where the sum of clockwise moments equals the sum of anticlockwise moments AND the net force is zero. Imagine a seesaw perfectly balanced – all forces and moments cancel.
平衡： 顺时针力矩之和等于逆时针力矩之和，且合力为零的状态。想象一个完美平衡的跷跷板——所有力和力矩相互抵消。
Shear Force and Bending Moment: Shear force acts parallel to the cross‑section (sliding action); bending moment causes the beam to curve. An easy visual: shear = scissors cutting paper; bending = an archer’s bow flexing.
剪力与弯矩： 剪力平行于横截面作用（滑动效应）；弯矩使梁弯曲。简单视觉：剪力 = 剪刀剪纸；弯矩 = 弓在拉弦时弯曲。
Truss: A framework of members joined at their ends to form a rigid structure. Triangles are used extensively because they cannot distort without changing side lengths. Think of bridge frameworks or roof supports.
桁架： 由端部连接的杆件组成的刚性骨架。广泛使用三角形，是因为在不改变边长的情况下三角形无法变形。想一想桥梁骨架或屋顶支撑。
4. Dynamics and Kinematics | 动力学与运动学
Velocity (v) vs Speed: Velocity is a vector (has direction); speed is a scalar. ‘Velocity has a Vector, Speed is Simple – just magnitude.’
速度 (v) 与速率： 速度是矢量（有方向）；速率是标量。’Velocity 有 Vector，Speed 是 Simple——只有大小’。
Acceleration (a): Rate of change of velocity. a = (v – u) / t. Negative acceleration = deceleration. When a car brakes, its acceleration is opposite to its motion.
加速度 (a)： 速度的变化率。a = (v – u) / t。负加速度即减速。汽车刹车时，加速度方向与运动方向相反。
Newton’s Three Laws – Quick Memory: 1st: Inertia (object resists change of motion). 2nd: F = ma. 3rd: Action‑reaction pairs. ‘1‑2‑3: lazy, force, push‑back.’
牛顿三定律快速记忆： 第一定律：惯性（物体抗拒运动状态改变）。第二定律：F = ma。第三定律：作用力与反作用力。’123：惰性、力、反推’。
Work, Energy, Power: Work = Force × distance (J). Energy = capacity to do work. Power = work done per second (W). ‘Work is the transfer, Energy is the bank, Power is the rate.’
功、能、功率： 功 = 力 × 距离 (J)。能量 = 做功的能力。功率 = 每秒做功的量 (W)。’功是转账，能量是账户，功率是速度’。
Momentum (p): p = m v. A heavy lorry moving slowly can have the same momentum as a light car speeding. Conservation of momentum: in a closed system, total momentum before a collision equals total after.
动量 (p)： p = m v。一辆缓慢行驶的重型卡车可能与一辆快速行驶的轻型汽车具有相同的动量。动量守恒：在封闭系统中，碰撞前的总动量等于碰撞后的总动量。
5. Thermodynamics Basics | 热力学基础
Temperature vs Heat: Temperature (K or °C) measures average kinetic energy of particles; heat (J) is the total thermal energy transferred. Mnemonic: ‘Temperature is intensity, heat is the amount.’
温度与热量： 温度（K 或 °C）衡量粒子的平均动能；热量（J）是传递的总热能。记忆法：’温度是强度，热量是总量’。
Specific Heat Capacity (c): Energy needed to raise the temperature of 1 kg of a substance by 1 K. Q = m c Δθ. Water has high c – it takes a long time to boil but also cools slowly.
比热容 (c)： 使 1 kg 物质温度升高 1 K 所需的能量。Q = m c Δθ。水的比热容很大——烧水耗时久，但冷却也慢。
Latent Heat: Energy absorbed or released during a phase change at constant temperature (melting, boiling). Q = m L. ‘Latent’ means hidden – the energy is ‘hiding’ in the state change, not showing as a temperature rise.
潜热： 在恒定温度下相变（熔化、沸腾）时吸收或释放的能量。Q = m L。’Latent’ 意为潜藏——能量’藏在’状态变化中，不表现为温度升高。
Thermal Conductivity: A material’s ability to conduct heat. Metals have high conductivity; insulators like polystyrene have low. ‘Copper conducts, wool resists.’
热导率： 材料导热的能力。金属导热率高；聚苯乙烯等绝热体导热率低。’铜导热，羊毛隔热’。
Thermal Expansion: Most materials expand when heated. Linear expansion: ΔL = α L₀ Δθ. Gaps in bridges and railway lines accommodate this expansion.
热膨胀： 大多数材料受热膨胀。线膨胀：ΔL = α L₀ Δθ。桥梁和铁轨的间隙就是为了容纳这种膨胀。
6. Fluid Mechanics Terminology | 流体力学术语
Density (ρ) and Pressure (p): ρ = mass / volume (kg·m⁻³). p = force / area (Pa). In a liquid, pressure increases with depth: p = ρ g h. Deeper in a swimming pool, your ears hurt more – more water pressing down.
密度 (ρ) 与压强 (p)： ρ = 质量 / 体积 (kg·m⁻³)。p = 力 / 面积 (Pa)。液体中压强随深度增加：p = ρ g h。游泳池里越深耳朵越痛——上方水压越大。
Upthrust / Buoyancy: The upward force on a body immersed in a fluid, equal to the weight of the displaced fluid (Archimedes’ principle). Why ships float: they displace a huge weight of water.
浮力： 浸在流体中的物体受到的向上力，等于排开流体的重量（阿基米德原理）。轮船之所以能浮起来，是因为它排开了巨大重量的水。
Viscosity: A fluid’s resistance to flow. Honey has high viscosity; water has low. In engineering, viscous drag affects lubrication and pipe flow design. ‘Slow as molasses = high viscosity.’
黏度： 流体抵抗流动的性质。蜂蜜黏度高；水黏度低。在工程中，黏性阻力影响润滑和管道流动设计。’如糖浆般慢 = 高黏度’。
Laminar vs Turbulent Flow: Laminar: smooth, parallel layers (low velocity, orderly). Turbulent: chaotic, mixing eddies (high velocity). Reynolds number (Re) predicts the transition. Think of a gentle stream vs white‑water rapids.
层流与湍流： 层流：平滑的平行流层（低速、有序）。湍流：混乱的混合涡流（高速）。雷诺数 (Re) 预测转变点。想象宁静的小溪与激流险滩。
Bernoulli’s Principle: In a steady flow, an increase in fluid speed occurs simultaneously with a decrease in pressure. Explains how aeroplane wings generate lift and how a perfume atomiser works.
伯努利原理： 在稳定流动中，流体速度增加的同时压强减小。解释了飞机机翼如何产生升力，以及香水喷雾器的工作原理。
7. Electrical and Electronic Concepts | 电气与电子概念
Current (I), Voltage (V), Resistance (R): Ohm’s Law: V = I R. Current is the flow of charge (amps), voltage is the electrical ‘push’ (volts), resistance opposes the flow (ohms). ‘I follows V, R restrains.’
电流 (I)、电压 (V)、电阻 (R)： 欧姆定律：V = I R。电流是电荷的流动（安培），电压是电’推力’（伏特），电阻阻碍流动（欧姆）。’I 跟着 V，R 拉着’。
Power in Electrical Circuits: P = V I = I² R = V² / R. High power means more energy per second – a kettle (2.2 kW) uses far more power than a LED bulb (10 W).
电路中的功率： P = V I = I² R = V² / R。高功率意味着每秒更多能量——一个电热水壶 (2.2 kW) 比一个 LED 灯泡 (10 W) 消耗的功率大得多。
Series vs Parallel: Series: current same, voltage divides; R_total = R₁ + R₂ + … Parallel: voltage same, current divides; 1/R_total = 1/R₁ + 1/R₂ + … Mnemonic: ‘Series = same on a train (current), parallel = many paths.’
串联与并联： 串联：电流相同，电压分配；R_总 = R₁ + R₂ + … 并联：电压相同，电流分配；1/R_总 = 1/R₁ + 1/R₂ + … 记忆法：’串联像火车一节节（电流通），并联像多条路分岔’。
Semiconductor Basics: Diodes allow current in one direction only (forward bias); transistors can amplify or switch signals. Think of a diode as a one‑way street, a transistor as a tap controlling water flow.
半导体基础： 二极管仅允许单向电流通过（正向偏置）；三极管可放大或开关信号。将二极管想象为单行道，三极管想象为控制水流的水龙头。
AC vs DC: Alternating current (AC) reverses direction periodically (mains electricity); direct current (DC) flows one way (batteries). AC symbol: sine wave ~, DC: straight line – – –.
交流电与直流电： 交流电 (AC) 周期性改变方向（市电）；直流电 (DC) 单向流动（电池）。交流电符号：正弦波 ~，直流电：直线 – – –。
8. Manufacturing Processes | 制造工艺
Casting: Pouring molten metal into a mould. Sand casting is cheap for large parts; die casting gives fine finish. Remember: ‘Casting = liquid into shape.’
铸造： 将熔融金属浇入模具。砂型铸造适合大型零件且成本低；压铸表面光洁。记住：’铸造 = 液体变成形’。
Forming / Forging: Shaping metal through plastic deformation, often by hammering or pressing. Hot forging makes the metal easier to shape; cold forging improves strength. ‘Forge a sword – heat, beat, repeat.’
成形 / 锻造： 通过塑性变形（通常是锤打或压制）使金属成形。热锻使金属易于成形；冷锻提高强度。’锻造一把剑——加热、锤打、反复’。
Machining: Removing material using cutting tools: turning (on a lathe), milling, drilling. Subtractive process. ‘Machining cuts away to reveal the part.’
机械加工： 使用切削工具去除材料：车削（在车床上）、铣削、钻孔。减材工艺。’机械加工切除材料显露零件’。
Welding vs Brazing vs Soldering: Welding melts the base metals; brazing uses a filler metal above 450 °C; soldering uses a filler with a lower melting point (usually below 450 °C). ‘From strongest to least: Weld > Braze > Solder.’
焊接、钎焊与软焊： 焊接熔化母材；钎焊使用 450 °C 以上的填充金属；软焊使用熔点更低的填充料（通常低于 450 °C）。’强度由高到低：焊接 > 钎焊 > 软焊’。
Additive Manufacturing / 3D Printing: Building objects layer by layer from a digital model. FDM (filament), SLA (resin), SLS (powder). Great for prototyping and complex geometries. ‘Add lives, not subtract!’
增材制造 / 3D 打印： 根据数字模型逐层构建物体。FDM（丝材）、SLA（树脂）、SLS（粉末）。非常适合原型制作和复杂几何形状。’增材是加，不是减！’
9. Design and Communication | 设计与沟通
Orthographic Projection: A way of representing a 3D object using 2D views: front, top, side – usually in first or third angle. ‘Ortho = straight, graphic = drawing – straight drawings from different angles.’
正交投影： 用二维视图表示三维物体的方法：正视图、俯视图、侧视图——常用第一角或第三角投影。’Ortho = 正，graphic = 图——从不同方向画的正视图’。
Isometric Drawing: A 3D pictorial drawing where the three axes are 120° apart and dimensions are drawn at full scale. ‘Iso = equal, metric = measure – equal angles, no perspective.’
等轴测图： 一种三维图像，三条轴线互成 120°，尺寸按实际比例绘制。’Iso = 相等，metric = 测量——角度均等，无透视’。
CAD (Computer‑Aided Design): Using software to create precise 2D or 3D models. Enables simulation, rapid modification, and direct transfer to CAM. ‘CAD draws, CAM makes.’
CAD（计算机辅助设计）： 使用软件创建精确的二维或三维模型。可进行仿真、快速修改，并能直接输出到 CAM。’CAD 画，CAM 造’。
Specification & Tolerance: Specifications define the exact requirements (material, dimensions, finish). Tolerance is the permissible limit of variation. Example: a shaft diameter of 20 ± 0.05 mm. ‘Spec sets the goal, tolerance allows a tiny wiggle.’
规格与公差： 规格确定了精确要求（材料、尺寸、表面处理）。公差是允许的变动范围。例如：轴径 20 ± 0.05 mm。’规格定目标，公差留点小余地’。
Dimensions & Annotations: Always include overall dimensions, critical sizes, and notes on surface finish or heat treatment. Good dimensioning avoids ambiguity. Use the ‘same unit everywhere’ rule.
尺寸与注释： 务必标注总尺寸、关键尺寸，以及表面处理或热处理的注释。良好尺寸标注避免歧义。采用’全图统一单位’原则。
10. Health and Safety | 健康与安全
Risk Assessment: Identifying hazards, evaluating the likelihood and severity of harm, and implementing control measures. The hierarchy: eliminate, substitute, engineering controls, administrative controls, PPE.
风险评估： 识别危害，评估伤害的可能性和严重程度，并实施控制措施。层级：消除、替代、工程控制、管理控制、个人防护装备 (PPE)。
Personal Protective Equipment (PPE): Goggles, gloves, steel‑toe boots, hard hats, ear defenders. The last line of defence – never rely on PPE alone.
个人防护装备 (PPE)： 护目镜、手套、钢头鞋、安全帽、耳罩。最后一道防线——绝不能单靠 PPE。
Safety Symbols: Learn the ISO shapes: red circle with diagonal bar = prohibition; yellow triangle = warning; blue circle = mandatory action; green square = emergency escape or first aid. ‘Red forbids, Yellow alerts, Blue commands, Green guides.’
安全标志： 牢记 ISO 图形：红色圆圈加斜杠 = 禁止；黄色三角形 = 警告；蓝色圆形 = 必须行动；绿色方形 = 紧急出口或急救。’红禁，黄警，蓝令，绿引导’。
Manual Handling: Lifting technique: bend knees, keep back straight, load close to body. Assess weight, get help if needed. ‘Lift with your legs, not your back.’
人工搬运： 搬运技巧：屈膝，保持背部挺直，负载贴近身体。先评估重量，必要时求助。’用腿发力，别用腰’。
Fire Classes & Extinguishers: Class A: ordinary combustibles (water). Class B: flammable liquids (foam/CO₂). Class C: flammable gases (dry powder). Electrical: non‑conductive agent (CO₂). Remember ‘A‑water, B‑foam, C‑powder, Spark‑CO₂.’
火灾分类与灭火器： A 类：普通可燃物（水）。B 类：易燃液体（泡沫/CO₂）。C 类：易燃气体（干粉）。电气火灾：不导电灭火剂（CO₂）。记住 ‘A‑水，B‑泡，C‑粉，电火花‑CO₂’。
Emergency Procedures: Know your nearest fire exit, assembly point, and the location of first aid. Drill the mantra: ‘Stop – Think – Act.’
应急程序： 了解最近的安全出口、集合点和急救箱位置。默念口诀：’停——想——动’。
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