📚 Year 8 CAIE Engineering: Case Study Practical Exercises | CAIE 八年级工程：案例分析实战演练
Engineering is about turning ideas into real solutions that make lives easier, safer and more sustainable. In Year 8 CAIE Engineering, case studies help you practise the design thinking cycle that all engineers use. You will analyse real problems, research constraints, sketch ideas, choose materials, build models and evaluate outcomes. This article walks you through a complete case study exercise, with practical tips for every stage. By the end, you will feel confident tackling any engineering challenge in your coursework.
工程学是将想法转化为让生活更便捷、更安全、更可持续的实际解决方案的学科。在 CAIE 八年级工程课程中，案例分析帮助你演练所有工程师都会使用的设计思维循环。你将分析真实问题、研究限制条件、绘制草图、选择材料、制作模型并评估成果。本文会带你完整演练一个案例分析，并为每个阶段提供实用技巧。学完后，你将自信地应对课程中的任何工程挑战。
1. The Engineering Design Process | 工程设计流程
Engineers do not just build things on the first try. They follow a structured cycle: Ask – identify the problem and constraints; Imagine – brainstorm possible solutions; Plan – draw designs and list materials; Create – build a prototype; and Improve – test and refine. This process is iterative, meaning you often go back to earlier steps when tests reveal weaknesses.
工程师并不是一次就成功。他们遵循一个结构化的循环：提问——明确问题与约束；构思——头脑风暴可能的解决方案；计划——绘制设计图并列出材料；创造——制作原型；改进——测试并优化。这个过程是迭代的，当测试揭示出不足时，你常常需要回到前面的步骤重新调整。
In your case study, you will apply this process. For example, if asked to design a mobile phone stand, you first ask 'Who will use it? What angles are best?' Then you imagine several shapes, plan with sketches, create a cardboard model, and finally test it with a real phone.
在你的案例分析中，你将应用这个流程。比如，要求设计一个手机支架，你首先要提问“谁会使用它？最佳角度是多少？”然后构思多种形状，画出草图制定计划，用纸板制作模型，最后用真实的手机进行测试。
2. Problem Identification and Constraints | 问题识别与约束
A good case study starts with a clear problem statement. You must read the brief carefully and underline the needs, wants and 'must-haves'. A need might be 'must hold a 500 g tablet', while a want could be 'adjustable viewing angle'. Constraints are limits such as cost, size, weight, time and available tools.
一个好的案例分析始于清晰的问题陈述。你必须仔细阅读简介，划出需求、期望和“必备条件”。需求可能是“必须能承托 500 克的平板电脑”，期望可能是“可调节视角”。约束条件则是成本、尺寸、重量、时间和可用工具等限制。
Use a table to organise constraints. For a bridge case study, you might note: maximum span 30 cm, materials limited to balsa wood and glue, load must be 2 kg, and only four weeks to build. Keeping constraints visible helps you stay realistic.
用表格梳理约束条件。对于桥梁案例，你可以列出：最大跨度 30 cm，材料仅限于轻木和胶水，必须承重 2 kg，且只有四周时间来制作。将约束条件展示出来有助于保持设计的可行性。
Example constraint table:
| Constraint / 约束 | Details / 详情 |
| Span / 跨度 | 30 cm |
| Materials / 材料 | Balsa wood, PVA glue / 轻木, 白胶 |
| Load / 载荷 | 2 kg at centre / 中心 2 kg |
| Time / 时间 | 4 weeks / 4 周 |
3. Research and Specification Writing | 研究与规格书撰写
Before drawing, you need to research. Look at existing products, study how they solve the problem, and learn from technologies already in use. For a bridge, research truss patterns (Warren, Pratt) and look at real footbridges. Collect images and note what works well.
在动手绘制之前，你需要进行研究。观察现有的产品，研究它们如何解决问题，从已投入使用的技术中学习。对于桥梁，研究桁架结构（华伦式、普拉特式），并观察真实的人行桥。收集图片，记录哪些设计行之有效。
From your research, write a design specification – a list of measurable targets your solution must hit. Use precise language: 'The bridge must support a 2 kg load without breaking' rather than 'it should be strong'. Include dimensions, weight, safety and user needs.
根据研究结果，撰写一份设计规格书——这是你的解决方案必须达到的可量化的目标清单。使用精确的语言：“桥梁必须在不断裂的情况下支撑 2 kg 的载荷”，而不是“它应该很坚固”。包含尺寸、重量、安全性和用户需求。
Specification points often cover function ('allow water to flow under bridge'), aesthetics ('look like a real bridge'), materials ('use only supplied balsa') and cost ('use less than 200 cm of wood'). These points will be used later to judge your design's success.
规格要点通常涵盖功能（“让水从桥下流过”）、美学（“像一座真实的桥梁”）、材料（“只使用提供的轻木”）和成本（“使用少于 200 cm 的木材”）。这些要点日后将用来评判你的设计是否成功。
4. Idea Generation: Brainstorming | 方案生成：头脑风暴
Now you let creativity flow. Brainstorm at least three different ideas without judging them yet. Sketch quickly – beam bridge, arch bridge, suspension bridge, or a truss frame. Label key parts and materials. The goal is quantity and variety, not perfection.
现在让创意自由迸发。对至少三种不同方案进行头脑风暴，暂不做评判。快速绘制草图——梁桥、拱桥、悬索桥或桁架框架。标注关键零件和材料。目标是数量和多样性，而非完美。
Use techniques like SCAMPER: Substitute a part, Combine two ideas, Adapt something from nature, Modify shape, Put to another use, Eliminate unnecessary material, Reverse orientation. For a bridge, could you substitute wood beams with a arch? Adapt a spider-web pattern?
使用诸如 SCAMPER 这样的技巧：替代某个部件、结合两种想法、借鉴自然结构、修改形状、另作他用、移除不必要的材料、反转方向。对于桥梁，能否用拱替代木梁？能否借鉴蛛网图案？
Working in a team, you can put all sketches on a board and comment on each. Remember, at this stage no idea is 'wrong'. Even wild concepts can spark a practical solution later.
在团队协作中，你可以把所有草图贴在白板上并互相评论。记住，在这个阶段没有“错误”的想法。即使是大胆的概念也可能在之后激发实际的解决方案。
5. Evaluating and Selecting Solutions | 评估和选择方案
With several ideas in front of you, it is time to pick the best one. Use a decision matrix where you score each idea against your specification points. For example, rate bridge ideas on strength (1-5), ease of building (1-5), material use (1-5) and appearance (1-5). Multiply by importance weight if some criteria matter more.
面对多个方案，是时候选出最佳的那一个了。使用决策矩阵，根据你的规格要点为每个方案打分。例如，对桥梁方案的强度（1-5）、搭建容易度（1-5）、材料使用（1-5）和外观（1-5）进行评分。如果某些标准更重要，则可乘以权重。
An idea that scores highest is your primary design. However, you can also combine strong features from two ideas into a hybrid design. Document why you chose it, referring back to your specification. This justification is important for your portfolio.
得分最高的方案就是你的主要设计。不过，你也可以将两个方案中的优势特征结合成一个混合设计。记录下你选择的理由，并回溯到规格书。这一论证对你的作品集非常重要。
For our bridge case study, a Pratt truss might score highly on strength but be complex to build. A simple beam bridge could be easier but weaker. You might decide on a truss with easy-to-cut joints, balancing strength and build time.
在我们的人行桥案例中，普拉特桁架在强度上可能得分很高，但建造复杂。简单的梁桥可能更容易制作但强度较弱。你也许会选择一种带有易切割节点的桁架，以此来平衡强度与搭建时间。
6. Sketching and CAD Modelling | 草图与计算机辅助建模
Refine your chosen idea with detailed sketches. Use isometric or orthographic projections, adding dimensions in millimetres. Show how parts fit together, label each component and indicate materials. A neat, annotated drawing communicates your design clearly.
用详细的草图完善你的选定方案。使用等轴测图或正交投影，并标注以毫米为单位的尺寸。展示零件是如何组合在一起的，为每个部件注明标签和材料。一副整洁、带注释的图纸能清晰地传达你的设计。
If you have access to CAD software like TinkerCAD or Fusion 360, create a 3D model. CAD allows you to check fits, measure volumes and even simulate forces. For Year 8, a simple 3D model of a bridge upright and truss members is excellent practice.
如果你能使用 TinkerCAD 或 Fusion 360 等计算机辅助设计软件，可以创建一个三维模型。CAD 可以让你检查配合情况、测量体积，甚至模拟受力。对于八年级而言，制作一个桥梁立柱和桁架杆件的简单三维模型就是很好的练习。
Always keep your drawings to scale where possible. A scale of 1:1 or 1:2 helps you transfer measurements directly to your building materials later. Print or save your CAD files to include in your project report.
尽可能按比例绘制图纸。1:1 或 1:2 的比例能帮助你在后续制作时直接将测量数据转移到材料上。打印或保存你的 CAD 文件，以便纳入项目报告。
7. Materials and their Properties | 材料及其性能
Choosing the right material is as important as the shape. An engineer must understand properties like tensile strength, compressive strength, density, stiffness and corrosion resistance. For a model bridge, balsa wood is light but has good compressive strength; however, it splinters easily under tension.
选择合适的材料与选择形状同样重要。工程师必须了解材料的抗拉强度、抗压强度、密度、刚度和耐腐蚀性等性能。对于模型桥梁，轻木虽轻但抗压强度良好；然而，它在受拉时容易开裂。
Compare common materials in a table. For each, list its Young's modulus (stiffness), density and typical use. When you justify your choice, say ' for the top chord because it is light (density ≈ 160 kg/m³) and resists compression well.'
通过表格来比较常见材料。列出每种材料的杨氏模量（刚度）、密度和典型用途。在你论证选材时，可以这样说：“我选择轻木作为顶弦杆，因为它重量轻（密度约为 160 kg/m³）且抗压性好。”
| Material / 材料 | Density / 密度 | Strength / 强度 | Use in models / 模型用途 |
| Balsa wood / 轻木 | 160 kg/m³ | Good compression / 良好的抗压性 | Truss members / 桁架杆件 |
| Cardboard / 硬纸板 | 700 kg/m³ | Moderate / 中等 | Deck, gussets / 桥面, 节点板 |
| String / 棉线 | Very low / 极低 | Good tension / 良好的抗拉性 | Suspension cables / 悬索 |
8. Forces and Structural Analysis | 力与结构分析
Every structure experiences forces: tension (pulling), compression (pushing), bending, shear and torsion. In a truss bridge, top chords are typically in compression and bottom chords in tension. Understanding this helps you place stronger materials where they are most needed.
所有结构都会承受力：拉力（拉伸）、压力（压缩）、弯曲、剪切和扭转。在桁架桥中，上弦杆通常受压，下弦杆受拉。理解这一点能帮助你在最需要的地方使用强度更高的材料。
m with a central load W, the reactions at each end are W/2. You can practise calculating these using simple equilibrium: sum of vertical forces = 0.
绘制桥梁的受力图。箭头表示载荷（向下）和来自支座的支反力（向上）。对于承受中心载荷 W 的简支梁，两端的支反力各为 W/2。你可以用简单的平衡条件来练习计算：竖向力的总和为零。
Equilibrium: ΣFy = 0, so Rₐ + Rₙ = W
平衡条件： ΣFy = 0，所以 Rₐ + Rₙ = W
Use this analysis to improve your design. If a joint is under high tension, reinforce it with a gusset plate or extra glue. Testing a simple model before the final build can reveal weak points early.
利用这些分析来改进你的设计。如果某个节点承受很高的拉力，可以通过添加节点板或额外胶水进行加固。在最终建造之前先测试简单模型，可以及早发现薄弱环节。
9. Ethical and Sustainable Design | 伦理与可持续设计
Engineering is not only about strength and cost; you must also think about people and the planet. Ethical design means your product does not harm users, respects privacy (if it uses cameras or sensors) and is accessible to people with disabilities.
工程学不仅仅关乎强度和成本；你还必须考虑人与地球。合乎伦理的设计意味着你的产品不会伤害用户、尊重隐私（如果使用了摄像头或传感器），并且对残障人士友好。
Sustainability asks: Can materials be recycled? Is energy used wisely? For a school bridge, you might choose FSC-certified balsa wood, avoid toxic glues and design for disassembly so parts can be reused. Even small choices matter in a case study.
可持续性要求回答：材料能回收吗？能源是否得到合理利用？对于学校的桥梁模型，你可以选择 FSC 认证的轻木，避免使用有毒胶水，并设计成可拆解结构以便零件重复使用。即使是在案例分析中，微小的选择也很重要。
In your report, add a paragraph on how your design reduces waste. For instance, you could nest parts in CAD to minimise offcuts, or specify that leftover balsa can be used in garden stakes. This shows you think like a responsible engineer.
在你的报告中，可以添加一段文字说明你的设计如何减少浪费。例如，你可以在 CAD 中排版零件以减少余料，或者说明多余的轻木可用作花园支架。这体现了你具备负责任的工程师思维。
10. Case Study: Designing a Footbridge | 案例分析：设计一座人行桥
Let's work through a complete mini case study. Problem: A school wants a footbridge over a small stream for students. Span: 1.2 m. Maximum load: 10 kg (equivalent to a child's weight scaled down). Materials: balsa wood, string, PVA glue. Constraint: must be less than 300 g and built in two double lessons.
让我们完整演练一个迷你案例。问题：一所学校希望在一条小溪上为学生建造一座人行桥。跨度：1.2 m。最大载荷：10 kg（缩放后相当于一名儿童的体重）。材料：轻木、棉线、白胶。约束：重量小于 300 g，并在两节连堂课内完成。
Step 1 – Ask: Identify needs: safe crossing, non-slip deck, handrails. Constraints: weight limit, time, only supplied materials.
步骤 1——提问：明确需求：安全通行、防滑桥面、扶手。约束条件：重量限制、时间、只能使用指定材料。
Step 2 – Imagine: Brainstorm three ideas: (a) simple beam bridge with side beams, (b) Warren truss with top and bottom chords, (c) suspension bridge with string cables. Sketches show (b) is likely strongest but (c) uses least wood.
步骤 2——构思：头脑风暴出三个方案：(a) 带边梁的简单梁桥，(b) 带上下弦杆的华伦桁架桥，(c) 使用棉线拉索的悬索桥。草图显示方案 (b) 可能强度最高，但方案 (c) 用木量最少。
Step 3 – Plan: riangles. Spec: top chord 4 mm × 4 mm balsa, bottom chord same, web members 2 mm × 2 mm, gusset plates from card.
步骤 3——计划：决策矩阵给出 (b) 得分最高，因为它平衡了强度与搭建时间。详细图纸采用华伦桁架，包含等边三角形。规格：上弦杆 4 mm × 4 mm 轻木，下弦杆相同，腹杆 2 mm × 2 mm，节点板用硬卡纸制作。
Step 4 – Create: Build prototype. Use a jig to hold pieces square. Glue joints, clamp and let dry. Attach deck from thin card. Test joints for stiffness.
步骤 4——创造：制作原型。使用定位模具保持直角。胶接接合处，用夹子固定并等待干燥。安装薄卡纸桥面。检查节点的刚度。
Step 5 – Improve: Test with 10 kg load. If deflection is too large, add web members or increase chord size. Document changes in logbook. Final bridge holds 12 kg and weighs 280 g – success!
步骤 5——改进：用 10 kg 载荷进行测试。如果挠度过大，增加腹杆或增大弦杆尺寸。在日志中记录更改。最终桥梁承重 12 kg，自重 280 g——成功！
11. Teamwork and Communication | 团队合作与沟通
Engineering projects are rarely done alone. During a case study you may work in a group of three or four. Clear roles (designer, builder, tester, documenter) help everyone contribute. Rotate roles so each person experiences different tasks.
工程项目很少由单人完成。在案例分析中，你可能需要以三到四人的小组合作。明确角色（设计员、施工员、测试员、记录员）有助于人人都能贡献力量。实行轮岗，让每个人都能体验不同的任务。
Use communication tools like a shared design notebook or a simple online board. Hold quick stand-up meetings at the start of each session: what did you do, what will you do, what blocks you? This keeps the team aligned.
使用共享设计笔记本或简易在线白板等沟通工具。每次活动开始时召开简短的站立会议：你完成了什么？将要做什么？遇到了什么障碍？这能确保团队步调一致。
Respect different ideas and resolve conflicts by referring back to the specification. If two members disagree on a shape, test both small models and let data decide. Good teamwork is a key skill assessed in CAIE Engineering.
尊重不同的想法，并通过回溯规格书来解决分歧。如果两位成员对形状有不同意见，可以分别制作小模型进行测试，用数据说话。良好的团队合作是 CAIE 工程课程重点评估的技能之一。
12. Presentation and Reflection | 展示与反思
Your case study ends with presenting your work. Prepare a short report or slideshow covering problem, research, sketches, CAD models, prototype photos, test results and conclusion. Include a reflection on what went well and what you would change.
你的案例分析以展示作品收尾。准备一份简短的报告或幻灯片，涵盖问题描述、研究、草图、CAD 模型、原型照片、测试结果和结论。纳入反思，说明哪些做得好以及你会改变哪些地方。
Use the 'What? So what? Now what?' reflection model: What did you do? So what did you learn from the result? Now what would you do differently next time? This shows deep thinking and earns top marks.
使用“What? So what? Now what?”反思模型：你做了什么？从结果中学到了什么？下一次你会做出哪些不同的改变？这展现了深度思考，可为你赢得高分。
Finally, create a display board with your best drawings and the finished prototype. Practise explaining your design choices using technical terms like 'compression member', 'truss' and 'factor of safety'. Your ability to communicate engineering ideas clearly is just as important as the build itself.
最后，用你最出色的图纸和最终原型制作一块展示板。练习使用“受压杆件”、“桁架”和“安全系数”等专业术语来解释你的设计选择。你清晰表达工程理念的能力与建造本身同样重要。
Published by TutorHao | Engineering Revision Series | aleveler.com
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