📚 IGCSE WJEC Engineering: Core Knowledge Review | IGCSE WJEC 工程：核心知识点梳理
Engineering is a multidisciplinary field that integrates science, mathematics, and technology to design and create solutions. For the IGCSE WJEC Engineering syllabus, a strong grasp of core principles is essential. This article provides a comprehensive review of key topics, including materials, mechanics, electronics, manufacturing, and design, aiding students in their revision and understanding.
工程学是一个融合科学、数学和技术以设计和创造解决方案的多学科领域。对于 IGCSE WJEC 工程学课程来说，牢固掌握核心原理至关重要。本文全面梳理了关键主题，包括材料、力学、电子、制造和设计等，帮助同学们复习和加深理解。
1. Classification of Engineering Materials | 工程材料分类
Engineering materials are broadly categorised into four main groups: metals, polymers, ceramics, and composites. Metals are further divided into ferrous and non-ferrous types based on their iron content.
工程材料大致分为四大类：金属、聚合物、陶瓷和复合材料。金属根据含铁量进一步分为铁金属和非铁金属。
Ferrous metals, including carbon steel and cast iron, are known for their high tensile strength and durability but are susceptible to rust. Non-ferrous metals such as aluminium, copper, and brass are lighter, corrosion-resistant, and often have good conductivity.
铁金属，包括碳钢和铸铁，以高抗拉强度和耐用性著称，但容易生锈。非铁金属如铝、铜和黄铜更轻、耐腐蚀，且通常具有良好导电性。
Polymers are classified as thermoplastics (e.g., ABS, polyethylene) which soften when heated and can be remoulded, and thermosets (e.g., epoxy resin) that undergo a permanent chemical change and cannot be reshaped. Composites like fibreglass and carbon fibre combine materials to achieve unique properties.
聚合物分为热塑性塑料（如 ABS、聚乙烯），加热会变软并可重塑；和热固性塑料（如环氧树脂），经历永久化学变化无法再塑形。复合材料如玻璃纤维和碳纤维结合材料以获得独特性能。
2. Material Properties and Testing | 材料特性与测试
Key mechanical properties determine a material’s suitability for an application. Strength is the ability to withstand load without failure, hardness resists indentation, toughness absorbs energy before fracture, ductility allows drawing into wire, and elasticity enables return to original shape after deformation.
关键机械性能决定材料是否适用于特定场合。强度是承受载荷而不失效的能力，硬度抵抗压痕，韧性在断裂前吸收能量，延展性可拉成丝，弹性使变形后恢复原状。
Common mechanical tests include the tensile test, which records stress-strain curves to determine yield strength and Young’s modulus. Hardness tests such as Brinell and Rockwell use indenters to measure resistance. Impact tests like Izod and Charpy evaluate toughness under sudden loads.
常见机械测试包括拉伸试验，记录应力-应变曲线以确定屈服强度和杨氏模量。硬度测试如布氏和洛氏使用压头测量阻力。冲击试验如艾氏和夏比评估承受突然载荷的韧性。
3. Forces and Moments | 力与力矩
A force is a push or pull that can cause an object to change motion or shape. In engineering, understanding forces is critical for structures and mechanisms. A moment is the turning effect of a force about a pivot, calculated as the product of the force and the perpendicular distance from the pivot.
力是能使物体改变运动状态或形状的推或拉。在工程中，理解力对结构和机构至关重要。力矩是力绕支点的转动效应，等于力与支点到力作用线的垂直距离的乘积。
M = F × d
An object is in equilibrium when the sum of all forces acting on it is zero and the sum of all moments about any point is zero. Free-body diagrams are used to visualise forces and solve for unknown reactions in beams and trusses.
当作用于物体的所有力之和为零，且对任意点的力矩之和也为零时，物体处于平衡状态。自由体图用于可视化力并求解梁和桁架中的未知反力。
4. Stress and Strain | 应力与应变
When a material is subjected to an external force, internal stresses develop. Stress (σ) is defined as force per unit area. Strain (ε) is the proportional deformation, measured as the change in length divided by the original length.
当材料承受外力时，内部会产生应力。应力（σ）定义为单位面积上的力。应变（ε）是比例变形，量度为长度变化除以原始长度。
σ = F / A ε = ΔL / L₀
Within the elastic limit, most materials obey Hooke’s Law, where stress is proportional to strain. The constant of proportionality is Young’s modulus (E). Beyond the elastic limit, plastic deformation occurs and the material does not return to its original shape.
在弹性极限内，多数材料遵循胡克定律，应力与应变成正比。比例常数即为杨氏模量（E）。超出弹性极限后发生塑性变形，材料不再恢复原状。
E = σ / ε
5. Basic Electrical Principles | 基础电学原理
Voltage (V) is the electrical potential difference that drives current around a circuit. Current (I) is the rate of flow of charge, measured in amperes. Resistance (R) opposes the flow and is measured in ohms. Ohm’s Law defines the relationship between these quantities.
电压（V）是驱动电流在电路中流动的电位差。电流（I）是电荷流动的速率，单位为安培。电阻（R）阻碍流动，单位为欧姆。欧姆定律定义了这些量之间的关系。
V = I × R
Power dissipated in a component is the product of voltage and current. Components can be connected in series, where current is the same but voltage divides, or in parallel, where voltage is the same but current divides.
元件消耗的功率是电压与电流的乘积。元件可串联连接，此时电流相同而电压分配；或并联连接，此时电压相同而电流分配。
P = V × I
6. Electronic Components and Circuits | 电子元件与电路
Resistors limit current and divide voltage; their value is coded with colour bands. Capacitors store electrical energy and are used in timing and filtering. Diodes allow current to flow in only one direction and are essential in rectification. LEDs emit light when forward biased.
电阻器限制电流并分压；其阻值用色环编码。电容器储存电能，用于定时和滤波。二极管仅允许单向电流，是整流的关键。发光二极管在正向偏置时发光。
Transistors can act as electronic switches or amplifiers. Integrated circuits (ICs) combine many components into a single chip, enabling complex functions. Understanding standard circuit symbols is vital for reading and creating schematic diagrams.
晶体管可用作电子开关或放大器。集成电路（IC）将众多元件集成到单一芯片中，实现复杂功能。理解标准电路符号对于阅读和绘制原理图至关重要。
7. Digital Logic | 数字逻辑
Digital systems use binary values 0 and 1 to represent low and high voltages. Logic gates perform basic operations on these inputs. The primary gates are AND, OR, NOT, NAND, NOR, and XOR. Each gate has a defined truth table that maps input combinations to the output.
数字系统使用二进制值 0 和 1 表示低电压和高电压。逻辑门对这些输入执行基本操作。基本门有与门、或门、非门、与非门、或非门和异或门。每个门都有明确的真值表，将输入组合映射到输出。
For example, an AND gate gives output 1 only when both inputs are 1. Boolean algebra can be used to simplify logic expressions, reducing the number of gates required in a circuit. This is crucial in designing efficient control systems.
例如，与门仅当两个输入均为 1 时输出 1。布尔代数可用于简化逻辑表达式，减少电路中所需门数量。这对设计高效控制系统至关重要。
AND gate truth table:
与门真值表：
| Input A | Input B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
8. Manufacturing Processes | 制造工艺
Manufacturing transforms raw materials into finished products. Forming processes include casting, where molten metal is poured into a mould; forging, which shapes metal using compressive forces; and rolling, which reduces thickness. Machining processes like turning, milling, and drilling remove material to achieve precise dimensions.
制造将原材料转变为成品。成形工艺包括铸造，将熔融金属浇入模具；锻造，利用压缩力塑形；以及轧制，减小厚度。机械加工工艺如车削、铣削和钻削去除材料以获得精确尺寸。
Joining techniques such as welding, soldering, and adhesive bonding assemble components. Modern additive manufacturing (3D printing) builds parts layer by layer directly from a CAD model, enabling complex geometries and rapid prototyping. Each process has its own cost, speed, and material compatibility considerations.
连接技术如焊接、锡焊和粘接用于组装部件。现代增材制造（3D 打印）直接从 CAD 模型逐层构建零件，可实现复杂几何形状和快速原型制作。每种工艺都有各自的成本、速度和材料兼容性考量。
9. Engineering Drawing and CAD | 工程制图与 CAD
Engineering drawings are a universal language used to convey design specifications. Orthographic projection presents 2D views (front, top, side) that fully describe the shape of an object. Isometric drawings show a 3D representation at 30-degree angles for visual clarity.
工程图是传达设计规格的通用语言。正交投影呈现完全描述物体形状的二维视图（前视图、俯视图、侧视图）。等距图以30度角展示三维图像，便于视觉理解。
Computer-aided design (CAD) software allows engineers to create accurate 3D models, run simulations, and generate 2D drawings automatically. Proper dimensioning, tolerances, and scale are essential to ensure parts fit together and function as intended. Standards such as BS 8888 define drawing conventions.
计算机辅助设计（CAD）软件使工程师能够创建精确的三维模型、运行模拟并自动生成二维图纸。恰当的尺寸标注、公差和比例对于确保零件配合并按预期运行至关重要。BS 8888 等标准定义了制图规范。
10. Sustainable Engineering and Life Cycle | 可持续工程与生命周期
Sustainable engineering aims to meet present needs without compromising future generations. Life cycle assessment (LCA) evaluates environmental impact from raw material extraction through manufacturing, use, and disposal. Designers seek to reduce energy consumption, emissions, and waste at every stage.
可持续工程旨在满足当前需求而不损害后代。生命周期评价（LCA）评估从原材料提取、制造、使用到处置的环境影响。设计师力求在每个阶段降低能耗、排放和废弃物。
The 6Rs framework guides sustainable decisions: Reduce material and energy use, Reuse components, Recycle materials, Repair products, Refuse unnecessary consumption, and Rethink designs for circularity. Choosing renewable materials and designing for disassembly are increasingly important in modern engineering.
6R 框架指导可持续决策：减少材料和能源使用、重复使用部件、回收材料、修复产品、拒绝不必要的消费以及为循环性重新思考设计。选择可再生材料和设计可拆解性在现代工程中愈发重要。
Reduce → Reuse → Recycle → Repair → Refuse → Rethink
Published by TutorHao | Engineering Revision Series | aleveler.com
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