Download
1 / 42
440 likes | 476 Vues
Design in Materials Engineering. MSE 401. Course Description. Classes of materials and materials data in design. Materials indices in design and designing against failure. Selection of materials and manufacturing processes in design. Process data and indices.
E N D
Design in MaterialsEngineering MSE 401
Course Description Classes of materials and materials data in design. Materials indices in design and designing against failure. Selection of materials and manufacturing processes in design. Process data and indices. Materials and industrial design, materials and the environment, Engineering ethics (law, contracts, code of ethics). Capable of working individually and within a team especially
Grading Scheme: Absence from a quiz, lab. or an examination will result in zero grade.
Books Text book 1) M. F. Ashby, Materials Selection in Mechanical Design, 3rd edition, Butterworth-Heinemann, 2005.2) Charles B. Fleddermann, Engineering Ethics, 3rd edition, Prentice Hall, 2007. Reference Books 1) M.M. Farag, Materials Selection for Engineering Design, Prentice Hall, 1997.2) G.E. Dieter, L.C. Schmidt, Engineering Design, 4th edition, McGraw-Hill, 2008.
M. F. Ashby, Materials Selection in Mechanical Design • This book (5 chapters) is about mechanical design, and the role of materials in it. • Mechanical components have mass; they carry loads; they conduct heat andelectricity; they are exposed to wear and to corrosive environments; they aremade of one or more materials; they have shape; and they must be manufactured.
Road Map • Explain the interdependency of product function, material, process, and geometry • Describe fundamental material classes • Define and characterize mechanical and physical properties • Describe and apply methods to evaluate material selection • Differentiate and select primary, secondary , and tertiary processes • Understand and apply methods to select appropriate manufacturing processes • Estimate the costs of manufacturing a product.
Materials Selection • The designer of any product, other than software must get involved with material selection. • Only occasionally will the exact grade of material be specified by the customer. • Even then the designer must understand the material to be able to design the product.
Engineering materials are evolving faster, and the choice is wider than ever before. • Examples of products in which a new material has captured a market are as common • plastic bottles. • aluminium cans. • polycarbonate eyeglass lenses. • carbon-fiber golf club shafts.
Decisions, decisions! So many materials, so much information. How do we decide? How do we begin to choose? First we need to look at the function of the product – product analysis
Design Process Startingpoint Market needor a new idea Endpoint productspecification of a productthatembodiesthe idea
Technical system Product Sub-assembles Components Design converts the inputs into the outputs The resulting arrangement is called the function-structure or function decomposition of the system.The function-structure gives a systematic way of assessing design options.
The design proceeds by developing concepts to perform the functions in the function structure, each based on a working principle. The next stage, embodiment, takes the promising concepts and seeks to analyze their operation at an approximate level. The embodiment stage ends with a feasible layout, which is then passed to the detailed design stage.
The consequences of choices made at the concept or embodiment stages may not become apparent until the detail is examined. The trial paths have dead-ends, and they loop back. It is like finding a track across difficult terrain — it may be necessary to go back many times if, in the end, we are to go forward. Once a path is found, it is always possible to make it look linear and logical.
Types of design • Originaldesign; (a new idea or working principle) • Adaptivedesign (seeks an incremental advance in performance through a refinement of the working principle) • Variantdesign (a change of scale or dimension or detailing without change of function)
Materials selection enters each stage of the design. Ex; a polymer may be the best choice for one concept, a metal for another, even though the function is the same. The problem, at this stage, is not precision and detail; it is breadth and speed of access: how can the vast range of data be presented to give the designer the greatest freedom in considering alternatives? At the embodiment stage the landscape has narrowed. Here we need data for a subset of materials, but at a higher level of precision and detail. These are found in the more specialized handbooks and software that deal with a single class or sub-class of materials The final stage of detailed design requires a still higher level of precision and detail, but for only one or a very few materials. Such information is best found in the data-sheets issued by the material producers themselves, and in detailed databases for restricted material classes
Product Analysis • Just what it says – analyse the product! • What does it do? • How does it do it? • Where does it do it? • Who uses it? • What should it cost?
Case Study – a bike • What is the function of a bike – obvious? • How does the function depend on the type of bike? • Racing • Touring • Mountain bike • Commuter • Childs
Case Study – a bike • How is it made to be easily maintained? • What should it look like (colours etc.)? • What should it cost? • How has it been made comfortable to ride? • How do the mechanical parts work and interact?
Component or system? • 1st problem is……. Is it one component or a system of components working together? A spanner is a component, a cordless screwdriver is a system.
System Analysis • When we analyse a system we need to break the system down into individual components and then analyse each one.
System Analysis – the bike The bike breaks down (we hope not!) into various parts: • Frame • Forks • Wheels • Saddle • Etc.
System Analysis – the bike We now need to look at the following for each part: • Requirements (mechanical, ergonomic, aesthetic etc.) • Function • How many are going to be made? • What manufacturing methods are we going to use?
Manufacturing This is a key question which has a massive influence on materials selection. e.g. The frame, what materials could we use?
Frame Materials • Steel – Strong, stiff, heavy, but cheap • Aluminium – weaker, lighter, more expensive than steel • Composite (CFRP) – strong, stiff, very light, but expensive to buy and to fabricate
What Properties? • Mechanical – Strength, modulus etc. • Physical – Density, melting point. • Electrical – Conductivity, resistivity. • Aesthetic – Appearance, texture, colour • Processability – Ductility, mouldability • And last, but not least………. Cost, cost, cost!
Where do I find the data? • Textbooks • Databooks • Manufacturer’s literature • Internet Sites
Textbooks • Good for general information • Some have tables of properties • Not good for detailed specifications and properties. • A useful first point of call
Databooks • One of the quickest sources of detailed information. • Usually contain grades and specifications as well as properties. • Small and perfectly formed – pocketbooks • Easy to navigate around
Manufacturer’s literature • Variable in quality and usefulness. • Often only cover their products. • Usually do not compare materials. • Can be biased. • Good for final selection before ordering.
Internet Sites • Can be a real minefield. • Lots of poorly presented information. • Google searches bring up lots of rubbish. • Hard to find technical information. • Best to use non-commercial sites.
The interaction between function, material, shape, and process lies at the heart of the material selection process
