Material Selection and Design Consideration Submitted to: Engr. Mary Jeanne Servigon
Submitted by: Jean Clauden C. Banks ChE4 Cloe Ferolino ECE 3 Mark Christian Basbano
What is Material Selection?
It is the foundation of all engineering applications and design.
It is the step in the process of designing an y physical object.
The main goal of material selection is to minimize cost while meeting product performance goals.
What is Design Consideration?
They are not requirements, but do present information that is important to consider in the design, construction and maintenance of improvements within public rights-of-way.
As an engineer, you don’t want to be famous for designing a component that failed.
Why Study Material Selection and Design Consideration?
An engineering student should be familiar with and versed procedures and protocols that are normally employed in the process.
Inappropriate or improper decisions can be disastrous from both economic and safety perspectives.
An important task for an engineer to perform is that of material selection with regard to component design.
Material Selection and Design Consideration Involves
Selecting a material,
How to wisely select a material;
Choosing a manufacturing process.
Materials
The matter from which a thing is or can be made. The substance or substances out of which a thing is or
A physical object, as opposed to something spiritual or mental, or something that is essential and relevant.
Types of Materials
can be made.
Ceramics
A ceramic is a non-metallic material composed of inorganic molecules, normally prepared by heating and subsequent cooling.
Polymers/ Plastics Plastics/polymers are made up of millions of repeated links to make a long molecule.
Metals
Metals are materials that are easily shaped by forming. They are excellent conductors of electricity and heat. Metals have an orderly arrangement of atoms, resulting in a crystalline structure.
Composites
Composites are the mixture of two materials, which in combination, offer superior properties to the materials alone.
Properties of Materials
When studying materials and especially when selecting materials for a project / design, it is important to understand key properties.
The expected level of performance from the material
Metallic and Nonmetallic Materials
It is the most common, and useful classification of a material. Metallic materials are those which are metals. The most common metals are iron , steel, bronze, copper and aluminum. The nonmetallic group includes materials such as wood, brick, concrete, rubber and plastic. Importance: Metals will be the more important of the two groups from the viewpoint of production, the relative importance of the nonmetallic group is increasing and will undoubtedly continue to do so BUT the selection of materials from either group is dependent, in the main, upon properties and cost.
Physical and Mechanical Properties In order to distinguish one material from another the physical properties are considered as the: color, density, specific heat, coefficient of thermal expansion/ conductivity, electrical conductivity, strength and hardness. Importance: Some of these are of prime importance in selecting materials for specific uses in the electrical or nuclear fields
Physical properties describe the reaction of a material to mechanical usage these often are called the mechanical properties of materials. To determine their mechanical properties, materials are subjected to standardized laboratory tests, wherein the influencing conditions are controlled. In this manner the reaction to changes in the variables may be determined. Importance: The results will be useful only to the extent to which service conditions duplicate the test conditions
Stress and Strain
When materials are used in mechanisms or structures they are subjected to applied forces.
For example a weight, W is suspended by means of a bar, the bar will elongate an amount equal to, ΔL elongation.
The internal reactive forces are called stress. Stress is measured quantitatively as the stress per unit area s-W/Ao, where Ao is the original cross-sectional area of the bar.
The weight tends to lengthen the bar it is called a tensile strain and the stress is called tensile strain.
Strength
The ability of a material to stand up to forces being a
applied without it bending, breaking, shattering or deforming in any way.
Tensile Strength
The ability of a material to stretch without breaking or snapping.
.
Ductility
The ability of a material to change shape
(deform) usually by stretching along its length.
Plasticity
The ability of a material to be change
in shape permanently.
The technician and his twin brother demonstrate the ‘plasticity’ of a molten aluminum by pouring it into a mould. Once the aluminum has cooled down, it can be removed from the casting sand. It has a new shape.
Elasticity
The ability of a material to absorb force and
flex in different directions, returning to its original position.
Material Selection Charts
Allow you to view the selection charts.
Enable you to interactively 'explode' particular classes of materials.
Give brief definitions of the properties on the chart
Provide general information about each chart and some insights into the physical reasons underlying it
Young’s Modulus- Density
'
Stiffness' measures how much something stretches when a load is applied. Young's modulus measures stiffness and is a material constant, i.e. it is the same whatever the size of the test-piece. Many applications require stiff materials, e.g. roof beams, bicycle frames - these materials lie at the top of the chart Many applications require low density materials, e.g. packaging foams these materials lie to the left of the chart.
•
•
•
•
•
Young's Modulus - Cost
Young's modulus measures stiffness and is a material constant, i.e. it is the same whatever the size of the test-piece. Many applications require stiff materials, e.g. roof beams, bicycle frames these materials lie at the top of the chart Many applications require low cost materials, e.g. packaging foams - these materials lie to the left of the chart. Cheap stiff materials lie towards the top left of the chart – mostly metals and ceramics.
Strength-Toughness
Strength measures the resistance of a material to failure, given by the applied stress (or load per unit area) The chart shows yield strength in tension for all materials, except for ceramics for which compressive strength is shown (their tensile strength being much lower) Toughness measures the energy required to crack a material; it is important for things which suffer impact There are many cases where strength is no good without toughness, e.g. a car engine, a hammer Increasing strength usually leads to decreased toughness Tempered steel is tougher but less strong than after quenching.
Strength-Cost
Strength measures the resistance of a material to failure, given by the applied stress (or load per unit area) The chart shows yield strength in tension for all materials, except for ceramics for which compressive strength is shown (their tensile strength being much lower) Many applications require strong materials, e.g. screw drivers, safety belts these lie at the top of the chart Unfortunately there are few cheap high strength materials (top left)
Electrical Resistivity
This chart is important for designing components requiring good electrical insulation (e.g. plug casings) or good electrical conductivity (e.g. electric POWER CABLES) at a good price Good electrical conductors are usually good thermal conductors and good electrical insulators are good thermal insulators The similarity between electrical and thermal properties means that the chart can also be used to identify materials requiring good thermal insulation (e.g. for kiln walls) or thermal conductivity (e.g. for FRYING PANS)
How To Select a Material
Material selection is a step in the process of designing any physical object. The main goal of material selection is to minimize cost while meeting product performance goals.[Systematic selection of the best material for a given application begins with properties and costs of candidate materials. Material selection is a step in the process of designing any physical object. In the context of product design, the main goal of material selection is to minimize cost while meeting product performance goals. Systematic selection of the best material for a given application begins with properties and costs of candidate materials.
Criteria when selecting material: •
thermal stress
•
mechanical stress
•
chemical stress
•
physiological harmlessness
•
thermal conduction / insulation
•
electrical requirements
•
optical requirements
•
fire behavior
•
weather resistance
•
radiation exposure
•
special specifications
When Selecting a Material for a Particular Design
Mechanical properties Wear of materials Corrosion Ability to manufacture
Mechanical properties •
Cost When a certain design is going to be actually produced it must be subjected to a number of manufacturing practices depending on the material and the design process.
•
•
It’s important for any material which is going to be subjected to mechanical forces in use. These forces cause the material to deform (i.e. change shape) and may cause it to fail (i.e. break).
Examples of Failures
A 737 engine; one of the turbine blades broke away and exited through the engine casing, nearly taking someone’s head off!
Wear of materials •
Wear is a problem when the materials are contacting each other in a product. So it must be ensured that the selected materials have sufficient wear resistance. This is also very important factor to consider when selecting a material for a particular design. In the engineering design process this has to be considered with great care.
Cost •
Cost is a critical fact to consider when selecting materials for a certain design for most products because they are facing a severe competition in the market.
Corrosion
Some materials are very likely to be corroded in the service depending on the service environment. Therefore it must be assured that the material is capable of being employed for the particular design before selecting it. Ability to manufacture •
To make the dimensions more accurate it has to be machined in the production. If this selection criteria is neglected the manufacture process might be very costly making it unprofitable as a commercial product. So before selecting the materials this fact also must be considered.
Material Cost and Availability •
Material must be priced appropriately (not cheap but right)
•
Material must be available (better to have multiple sources)
Manufacturing a Product Thought processes and procedures involved in designing and manufacturing common products. Example: Paper Clip Must meet its basic functional requirement: hold pieces of paper together with sufficient clamping force so that the papers do not slip away from each other. Design based on strength of materials and mechanics of solids, dealingwith the stresses and strains involved during manufacturing and during normal use of the product. Material selected must have certain stiffness and strength: Force to open the clip too high? Not enough clamping force on the paper? Permanent bend during use due to low yield stress?
Manufacturing a Product Other considerations: Style, appearance, surface finish or texture of clip Corrosion properties: rust marks on paper Production concerns: Bending of selected material during manufacturing without cracking or breaking Cutting the wire from a long piece without excessive wear Cutting the wire with a smooth edge The most economical way of manufacturing the clip to make a profit Consider the design, material selection, and processing methods involved in manufacturing a jet engine! Criteria for Selecting a Manufacturing Process Shape of the final product and raw material Type of material and its basic properties: Brittle and hard materials cannot be formed easily, but they can be cast or machined. Manufacturing process often alters the properties of the materials: metals that are formed at room temperature become stronger, harder, and less ductile than prior to processing. Design requirements
Additional Criteria Dimensional and surface finish requirements: Size, thickness, and shape complexity: parts with thin crosssections cannot be cast properly; complex parts cannot be formed easily. Tolerances and surface finish: better in hot-working vs. coldworking; dimensional changes, warpage, surface oxidation at elevated temperatures. Additional operations: grinding, polishing (better finish but more expensive!) Operational and Cost considerations: Design and cost of tooling Lead time required to begin production Effect of workpiece material on tool and die life Expensive materials: minimize scrap (e.g., machining produces too much scrap) Availability of machines and equipment Number of parts or products required and desired production rate Environmental concerns
Manufacturing Processes for Metals Casting: expendable mold and permanent mold Forming and Shaping: rolling, forging, extrusion, drawing, sheet forming, powder metallurgy, molding Machining: turning, boring, drilling, milling, planing, shaping, broaching, grinding, ultrasonic machining, chemical machining, electrical discharge machining (EDM), electrochemical machining, high-energy beam machining Joining: welding, brazing, soldering, diffusion bonding, adhesive bonding, mechanical joining Finishing Operation: honing, lapping, polishing, burnishing, deburring, surface treating, coating, plating
Choosing Methods of Production
Casting Processes Among the oldest methods of manufacturing: used to make arrowheads, ornaments, about 4000 B.C. Introduction of molten metal into a mold cavity; upon solidification, metal conforms to the shape of the cavity Capable of producing intricate shapes, with internal cavities, in a single piece Very large, very small, and hollow parts can be produced economically Typical cast products: engine blocks, crankshafts, pistons, valves, railroad wheels
Expendable mold casting : molds made of sand, plaster, ceramics, investment casting Permanent mold casting : molds, made of metals, can be re-used; pressure casting, die-casting, centrifugal casting
Forming and Shaping Processes Bulk deformation processes induce shape changes by plastic deformation under forces applied by tools and dies Take cast metal and roll it down into general shapes such as slabs, plates, billets, then forge it into near-net shape Forging: plastic deformation carried out by compression into a die (e.g., crankshafts, connecting rods, turbine disks, gears, wheels, bolt heads, hand tools,...)
Rolling: reducing the thickness or changing the cross-section of a long workpiece by compression through a set of rolls (e.g., plates for ship hulls, bridges, machine structures, nuclear vessels; sheets for automobile bodies, appliances, containers for food and beverages, ...) Extrusion: forcing a billet through a die opening by compression, hot or cold
Drawing: reducing the cross-section of a bar by pulling it through a converging die by tension (rods used for small components;wires used for cables, springs, musical instruments, fencing, shopping carts)
Sheet-Metal Forming Processes Producing thin sheets of metal at room temperature (metal desks, appliance bodies, aircraft panels, beverage cans, car bodies) Shearing: cutting a sheet metal by subjecting it to shear stress, between a punch and a die Bending: used to form flanges, curls, seams, corrugations Drawing: a flat sheet-metal blank is formed into a cylindrical or box-shaped part by means of a punch that presses the blank into the die cavity
Spinning: forming assymetric parts over a rotating mandrel with the use of rigid tools or rollers
Machining Processes Material removal from a workpiece: cutting, grinding, nontraditional machining processes Finishing operations that remove small amounts of material Pros: improves dimensional accuracy, can create hard-to-obtain features (e.g., sharp corners), can control surface fi nish Cons: expensive, generates waste, can have adverse effects on surface quality and properties of product Cutting to produce round shapes (e.g., shafts, pistons, cylinders, gun Drilling: making holes Turning: removing material while part turns (e.g., shafts, spindles, pins, handles, and various machine components) Facing, boring, parting Cutting to produce various shapes: Milling: cutting with a multi-tooth tool which rotates
Broaching: cutting with a multi-tooth tool which makes progressively deeper cuts (e.g., holes of circular, square, or irregular section, keyways, teeth of internal gears, ...) Planing, shaping, sawing, filing Workpiece material is too hard or brittle, or its shape is difficult to produce with sufficient accuracy by cutting Grinding: cutting with a rough wheel to finish a surface
Surface grinding, cylindrical grinding, internal grinding, centerless grinding
Joining Processes Includes welding, brazing, soldering, adhesive bonding, mechanical joining Reasons for importance: Product is impossible to manufacture as a single piece Product is easier and more economical to manufacture as individual components Products may have to taken apart for repair or maintenance Transporting the product in individual components and assembling them later may be easier and less costly Manufacturing Processes for Plastics Plastics are shipped to manufacturing plants as pellets or powders and are melted just before the shaping process. Polymers melt at relatively low temperatures and, unlike metals, are easy to handle and require less energy to process. Plastics can be molded, and formed, as well as machined and joined, into many shapes with relative ease and with little or no additional operations required. Extrusion: Raw powder is placed into a hopper and fed i nto the extruder barrel; the barrel has a screw that blends and conveys the powder down the barrel; the powder is heated and liquefied; the molten plastic is then forced into a die. Injection Molding: the powder is melted inside a heated chamber; the melt is forced into a split-die chamber either by a hydraulic plunger or by a rotating screw (cups, containers, knobs, toys,...)
Blow Molding: a tube is extruded and clamped into a mold cavity and then blown outward to fill the mold (e.g., hollow containers)
Thermoforming: a sheet is heated to the softening point and placed over a mold and pulled against the mold through the application of vacuum (e.g., advertising signs, packaging, panels for shower stalls,...) Compression Molding: a preshaped part or premeasured amount of powder is placed directly in a heated mold cavity; forming is done under pressure with a plug (e.g., dishes, handles, fittings, container caps,...)
