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137 Cards in this Set
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- Back
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3 ways to join plastics |
1. chemical -> glue, adhesives, solvents 2. thermo bonding -> heat/friction to fuse together plastic parts 3. mechanical -> physical attachments to bond plastic parts together (e.g. rivets) |
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what is solvent bonding? what happens after the solvent evaporates? |
also known as welding involves a chemical agent dissolving the outer skin of a resin sufficiently to allow it to be able to joined with other compatible parts solvent evaporates and a true bond is created with NO INTERMEDIATE MATERIAL |
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what are 3 factors that may be influenced by the evaporation rate of the solvent used? |
cleanliness of the area to be bonded type of joint design influence of speed |
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what's good about scoring when solvent bonding? |
more surface area to be bonded |
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when using adhesives, the cure cannot exceed ___ |
the heat-deflection temperature (e.g. melting of plastic) |
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what is ultrasonic welding? what happens when pressure is applied? |
a tool or horn vibrating at an ultrasonic frequency is brought into contact with one-half of the heat being assembled pressure applied and frictional heat generated cuz high frequency vibratory energy melts a molded ridge of plastic on one of the mating surfaces |
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what are benefits of ultrasonic welding? what is one drawback? |
heat is consistent and you get very clean joints cuz heat is confined to the joint area very high tensile shear strength so it's a very strong joint it's considered PERMANENT which means it can't be dissected -> could be a drawback |
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what is ultrasonic staking/swaging? what 2 types of materials does it involve? |
involve the assembly of plastic to metal or other dissimilar materials a hole in the part to be joined is located to receive a molding mating stud in the plastic part the vibrating horn has a CONTOURED tip so when it's brought into contact with the stud, it melts and reforms it to a locking head -> looks like a butt |
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what are 2 benefits of ultrasonic staking/swaging? |
consistent frequency, pressure, and time tight assemblies are assured cuz the reformed stud is allowed to cool |
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what is snap-fit assembly? why is it advantageous? |
method of assembly that works well with many resins no additional material are needed so mating parts can be assembled quickly/economically on the assembly line |
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what's the max amount of times you should use a snap-fit assembly? why? and what type of beam will provide a more efficient/stronger hold? |
generally used less than 10 times so many cycles (if you keep taking it apart) could accelerate fatigue a tapered beam will provide a more efficient and stronger hold |
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what are hinges and snap/locks? what is one thing you don't want in the mold? |
products with lids or covers normally designed with molded hinges and snaps don't want undercuts in the mold so designing hinges can be tricky |
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what is a self-tapping screw? why are they advantageous? what is it not intended for? |
they make their own thread (dig into the plastic) low residual stresses in area around the boss not intended for more than 3-4 disassemblies as the hole will strip and threads will not be able to grab |
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how to bond metal? 3 ways and describe them |
1. adhesives - need strength, toughness, resistant to fluids/chemicals/environmental degradation 2. thermo - soldering, brazing, gas welding, arc welding 3. mechanical fasteners - screws, bolts, etc. |
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what is brazing? what's the difference between brazing and soldering? is it stronger than solder? |
similar to soldering except it's done at temperatures ABOVE 850 degrees you use a torch kit and a brazing rod stronger than soldering cuz some limited alloying occurs between filler metal and base metal (they kinda both melt and amalgam) |
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what is gas welding? what are pros and cons of gas welding? |
in oxyacetylene welding, oxygen and acetylene gases are combined in a torch and ignited pro: metal parts are heated above melted temp so they flow together and no filler materials are needed con: pieces have to be a similar thickness cuz melting temperature would be different |
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what is arc welding? what are pros and cons? |
type of welding that uses welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point can use direct current or alternating current pros: used for various applications including shipbuilding, can be used for diff thickness con: welding region is usually protected by some sort of shielding gas, vapour |
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what is spot seam? what industry is it used in? |
metal sheets clamped between two electrodes that conduct a measured current small depressions are created at the spots of contact used in automobile industry |
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what is laser beam welding? what is it suitable for? |
focused high-powered light beam directed, shaped, and focused precisely on the work piece suitable for wielding narrow and deep joints and can be used on materials used to 1 inch thick |
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what are pems and what are they used for? |
fasteners for insertion into sheet metal if the metal is too soft to accept to withstand the expected tensile and torque stresses (e.g. aluminum), a thread insert can be used |
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what are shearing forces? what are compression forces? |
unaligned forces pushing one part of a body in one direction and another part of the body in opposite direction compression forces are when forces are aligned into each other |
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how to add artwork to plastics? 4 ways |
1. heat transfer printing 2. hydro printing/dripping - polyvinyl alcohol film with artwork and the piece is lowered into the floating ink layer which wraps around 3. decals - pigmented decorations printed on pre-cut adhesive |
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how to finish plastics? 3 ways |
put pattern/textures on it that are modled onto the final part flocking/suede flocking -> fuzzy finish with fibers metallization via electroplating |
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how to remove paint on metal? |
sandblasting |
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what are burrs? |
razor like thin triangular ridges created when a sheet is sheared, or a cast or forged part is cleaned by a trimming shear |
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how to deburr metal parts? 3 ways |
grinding fluids - reduce wear and lower power consumption polishing - using fine abrasive and soft smearing material produce a lustrous finish shot/sandblasting |
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what is electroplating? how does it work? why is it advantageous? |
coating of an electrically conductive object with a layer of metal using electrical current ions traveling through the electrolyte solution deposit on the work piece surface deposits a surface layer of a metal having some desired property (wear resistance, etc.) onto something lacking that can build up thin parts |
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what is electropolishing? what does it do? |
electrolytes attacks projections and smooths it down roughs out imperfections |
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what is anodic coating/anodizing? what's the process? |
oxidation process that converts the surface of aluminum and magnesium to an oxide layer, providing a decorative finish and protection piece is dipped into acid bath, resulting in chemical absorption of oxygen and dyes producing decorative surface films |
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what is vacuum metallizing? |
plating metal is evaporated at high temperatures in a vacuum and deposited on the part can provide uniform coating on complex parts popular in trophies! |
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what is porcelain-enamel? what does it do? how is colour added? when was it first used and where? |
durable glass permanently fused to metal under high temperatures acts as a protective surface for cooking utensils, kitchen/bathroom fixtures and appliances colour added through the addition of minerals 1850 in Austria and Germany |
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what is flame spraying? how does it work? |
coating processes in which melted materials are sprayed onto a surface a metal rod/wire/powder melted in a stream of oxy-acetylene flame |
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what is wear caused by? what does each substance relinquish? |
caused by the friction of one substance against another each substance relinquishes a certain quanNty of ma]er to the tearing acNon of the other |
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the most common direction of wear is _______ with human interaction |
parallel |
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what is a wiping action in which substances pass each other in a parallel course? |
polishing |
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how to reduce wear? how does it work? what else can this product do? |
lubricant build a cushion between the two materials in contact to reduce friction the cushion makes the surface in contact smooth by leveling the ins and outs and compromises the movement from both sides lubricant can also act as a means to cool or prevent overheaFng between parts |
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how to classify oil lubricant? |
through viscosity, which is a measure of its resistance to gradual deformation by shear stress or tensile stress |
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high viscosity versus low viscosity |
high = very thick and gooey, good for lubricating parts with loose tolerances low = thinner oil has lower number and flows easier, lubricates with high precision because it goes into crevices better |
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what is seize/seizing? |
when you run out of lubricant and your engine jams |
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what are machine bearings made purposely of to aid lubrication? what is a bearing? why are they designed to wear out? |
soft lead or bronze alloy bearing is like a crank shaft or wheel, something that spins designed to wear out cuz the shaft (what they're attached to) is harder to replace |
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what is rot caused by? |
fungi which live parasitically on cellulose since fungi can't photosynthesize for themselves and need a host |
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what is the moisture content of wood in an unheated structure? |
around 15-18% |
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what can prevent the growth of fungi? |
good ventilation and dry heat |
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what was the DeHavilland Mosquito and why was it an example of engineering ingenuity inspired by the challenges of war? |
aircraft made out of plywood and it's important because all-wood design was a major advantage during a time of acute storage of light metal alloys AND wood is light so it could go very fast |
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what are 3 ethical issues of plastic? what is plastic made out of? |
1. raw materials are not unlimited -> almost 7% of a barrel of oil is dedicated to creating raw material for plastic production 2. plastic waste products are a major component of land fills 3. costs will rise cuz petrochemical raw materials are becoming more scarce |
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what are 5 options to recycle plastic/go greener with plastic? what are pros and cons? |
1. reclaim energy from burning plastics pro: plastic waste constitutes a significant energy source con: HCI from burning comes from burning PVC, which damages ozone layer 2. breaking down plastics for reuse con: not as robust as original 3. degradable plastics 4. smart manufacturing to avoid waste 5. make longer-lasting products |
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what is pyrolysis? pro and con? |
process to reduce plastic to simple petrochemical raw materials thermal decomposition in the absense of oxygen and commonly carried out at temperatures between 400-800 degress celsium pro: regenerated end productsof this route differ only slightly from virgin material con: such materials can only be reused for arFcles which are not subject to high stresses |
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types of polymer degradation |
physical degradation - involve environmental stress cracking and plasticizer migration and loss chemical reactions - include oxidation and hydrolysis, particularly affect cellulose esters (cellulose nitrate and cellulose acetate), which emit acidic degradation products |
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what are biodegradable plastics made with? why? does it work? |
made with 5% cornstarch or vegetable oil the idea is that hungry bacteria will devour the starch/oil in the plastic and causing it to disintegrate to a fine dust BUT some environmentalists say it doesn't work cuz nothing degrades quickly in a modern landfill cuz they designed to inhibit degradation, not promote it |
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what are photodegradable plastics made with? what's a problem? |
they're made with a special blend of plastic or resin that breaks down at the presence of sunlight landfills have layers and things are buried, so UV light might not get to the plastic |
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what is planned obsolescence? |
business practice where products are designed to fail after a certain period of time or cycles |
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we use "design" to narrowly refer to _____ |
creaJve human acJvity |
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what engineering are design paradigms rooted in? 3 |
software engineering human factors engineering usability engineering |
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what are 3 design paradigms (patterns)? |
Engineering paradigm (Ford’s model) Human Information Processing (HIP) Paradigm Design-Thinking Paradigm |
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what 4 things do design paradigms focus on? |
reliability user performance user productivity avoiding errors |
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what does human information processing focus on? what is it based on? |
focus on metaphor of mind and computer as symmetrically coupled information processors based on study of how information is sensed, accessed, and transformed in human mind |
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design thinking includes _________ and ________ concerns |
emotional and phenomenological |
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what is the human factors engineering view of car design? 4 things to consider |
Steering wheel thickness so it "fits" an average human's hand size and strength Seat height Fit of the curve on the seat to fit lower back shape Safety restraints |
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what is the HIP view of car design? 3 things to consider |
presentation of critical information needed for driving meets limits of human signal detection modalities used to communicate a problem (e.g., low tire pressure): tactile via steering wheel, audio cue, blinking visual cue |
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what is the design thinking view of car design? 4things |
joy of driving thrill of speed pride of ownership how a car can be an integral part of one's lifestyle |
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design thinking is about _________ concerns what does that blank mean? |
phenomenological means first person consciousness |
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what is considered for phenomenological concerns for design thinking? |
Long-term emotional impact is considered |
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what did Bill Buxton say about a product? |
“A product is not just a product; it is an experience” |
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what is a design process that caters to importance of user? |
Empathize Define Ideate Prototype Test |
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empathy is the foundation of ___________ what are 3 strategies for designers to deal with empathy? |
foundation of human or user-centered design (UCD) 3 strategies Observe: Users and their behaviour in context Engage: Interact with and interview users Immerse: Experience what users experience |
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why empathize with users? 3 reasons |
- need to understand end users cuz you're solving their problems - watch what ppl do and understand what they think and feel - engage to uncover unexpected insights and needs |
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what can interviews help you understand? what can they help you identify? |
people’s thoughts, emotions, motivations, choices and behaviours |
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____ + ____ = insight |
USER + NEED = INSIGHT |
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5 tools for problem definition |
Storytelling Personas Clustering Task Flow Analysis Frameworks |
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what are personas? what are they based on? |
an hypothetical archetype that represents the behaviourand goals of a group of users sased on insights and observations from customer research |
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what do personas liberate designers from having to do? |
liberates designers from having to sort through all conflicting details of multiple user classes -> we can focus on designing for one person |
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what is the process of choosing a persona? |
1. generate a dozen candidate personas 2. select a couple to be accounted/included in design 3. identify best choice as primary persona |
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what is meant by stress in the context of materials? what is stress? |
when a force is applied to an elastic body, the body deforms stress is measure of the internal forces acting within a deformable body |
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what happened in the comet airliner disaster? what was the problem |
British, American and Russians embarked on a race to exploit jet turbine technology for commercial aviation after WW2 British DeHavilland Comet won -> it was the world's first commercially successful jet-powered airliner and had pressurized cabin... but one of the planes mysteriously exploded THE PROBLEM: crack had developed due to metal fatigue, and it quickly deteriorated under PRESSURE and fuselage would break |
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what is metal fatigue? |
progressive and localized structural damage that occurs when a material is subjected to cyclic or repeated loadings |
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what was the solution to the problem of the Comet airline disaster? |
design fuselage windows with larger radii or completely round |
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4 mechanical properties of metals |
- ductility - compression - hardness - brittleness |
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what is ductility? what's an example? |
the ability of a material to withstand plastic deformation without rupture (e.g. balloon and bubble gum) |
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how do ship designers counter catastrophic deformation? |
employ expansion joints to allow the ship’s hull to flex |
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what is compression? what's an example? |
a measure of the extent to which a material deforms prior to rupture warm bubble gum is an example because no matter how hard you step on it or squeeze it, it won’t rupture |
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what is hardness? |
ability of a material to withstand penetration and scratching |
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what is brittleness? what's a good example of brittle material? |
opposite of ductility glass good example of brittle material |
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Which (of the four) mechanical property of metal causedthe metal fatigue in the Comet? |
ductility |
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what are the 5 forces of stress? |
compression, tension, torsion, shear, and bending |
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what is compression? |
direct expression of gravity pulling everything to the center of the earth |
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______ holds most of man-made structures tightly together in compression |
gravity |
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Form wise, the designed and natural forms that assume mostly compressive loads are usually ______ and _______ |
thick and short |
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how can compression be produced? 2 ways |
1. tightening edges of a screw or bolt in the squeezing of a peg inside a hole 2. gas shock for your car, the air or gas inside the tension membrane acts as the compression element |
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what is tension? what is an example? |
completely opposite from compression (think of stretching) e.g. braided licorice |
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tension structures are typically ____, ____, and often ______ in appearance |
light, thin and oden linear in appearance |
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what is shearing? |
shearing is present when you rub your hands together, shearing sheets of paper with scissors etc |
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if you have a deck of cards in your hand and compress them, why do the cards on top appear longer than those on the bottom? what forces are present? what is a combination of those forces? |
curve is a shorter diameter on the inside versus outside forces present: compression, bending, tension shearing is combination of those |
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what is torsion? what is it a combination of? |
in simple terms, it's like twisting it's a combination of all the other four forces |
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how does the operation of the automobile rely on torsion? |
the driver’s hands turn the steering wheel, exerting a torsional force which is transferred torsionally to the front wheels |
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what is bending/flexure? |
in engineering terms, characterizes the behavior of a slender structural element subjected to an external load applied perpendicularly to a longitudinal axis of the element |
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what is an example of a structure with a mixture of stresses? |
bicycle wheel self-containedtension/compression structure spokes on a bike wheel are in tension pulling the outside rim into the center and the rim is in compression |
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the most direct links between material and form come through what? |
come through the forces that materials transmit and carry |
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who discovered/invented the arch and what force does the arch use? |
Romans discovered/invented the arch, which allowed them to cover great open areas or spans without columns using compression |
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stone and cemented brick are strong in what force and weak in what force? |
strong in compression, weak in bending and tension |
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wood is strong in what 3 forces? |
tension, compression and bending |
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wrought iron and steel have overcome the ________ of cast iron and can accommodate _______ and ______ |
Wrought iron and steelhave overcome the brittleness of cast iron, allowing slender members that can accommodate tension or bending |
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fabrics and high-tensile strength steel are strong in what force and weak in what 2 forces? |
strong in tensile force unable to carry bending and compression because they buckle |
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how to make a square rigid? |
add a cross member (diagonal) to make it two triangles |
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what is triangulation? |
when builders use diagonal struts or angle brackets to strengthen the intersections |
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what is a frame? what are three main designs for frame rails? |
a frame is the main structure and all components fasten to it 1. C-shape 2. Boxed 3. Hat |
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what are 3 design considerations for using self-tapping screws? |
1. diameter of the boss (extrude) should be at least three times the diameter of the hole 2. boss height should be less than or equal to 5 times the thickness of the nominal wall 3. thickness of the base of the boss wall should be less than or equal to 60% of the nominal wall |
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how to strengthen the boss? |
incorporating gussets at the base or by using connecting ribs attaching to nearby walls (little triangular supports attached) |
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what are threaded metal fasteners? what are 2 considerations? |
metal screws, nuts and bolts uncontrolled assembly torques with this type of assembly can cause excessive compression forces in the molded parts you may get what looks like sink holes or depressions |
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what is ultrasonic insertion? what is ultrasonic energy converted into and what does that do? |
when an insert is “vibrated” into place by using an ultrasonic transducer called the “horn” that is mounted into the ultrasonic device ultrasonic energy is converted to thermal energy by the vibrating action, which allows the insert to be melted into the hole |
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a good metal joint should be able to withstand what 3 forces? |
shear, compression, and tensile forces |
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what is soldering primarily used for? what's the process? when is solder best used and why? what are 3 solder alloys? |
conduct electric current and to seal food tins and similar products a non-ferrous filler metal called solder and flux are used to join metals using temperatures below 850 degrees Fahrenheit best used when stress is not a factor cuz soldering has little strength solder alloys: tin-lead, tin-silver, zinc aluminum |
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when are mechanical fasteners used in metal joining? are they a significant part of the cost? |
used during the assembly phase of production and are often a significant part of the cost |
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what are special purpose fasteners in the context of metal joining? |
range from paper clips to door locks and hinges |
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what is polyvinylchloride (PVC)? what are its features? what are its uses? |
PVC one of the cheapest and most versatile polymers in pure form, PVD rigid but not very tough uses: substitute for rubber/leather, pipes, road signs, dolls, medical tubes |
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what is the history of nylon? what are its features? what are they used in? |
developed during WW2 as substitute for silk and used for garment design features: strong, durable, low coefficient for friction, easy to inject mold nylons used in light duty gears, ropes, bushings, book bindings |
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what is the history of acrylic? what are its features? main uses? |
developed in 1872 and commercialized in 1933, used for aircraft cockpit canopies in WW2 hard and stiff and has several forms: sheet, rod, tube uses: glasses lenses, aircraft windows, lighting |
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what category of thermoplastics is polycarbonate and what does that mean? what are its features? uses? |
PC is one of the "engineering" plastics meaning they have better mechanical properties than cheaper polymers good toughness/rigidity and optical transparency used for car parts, toasters, visors, police riot shields, hockey helmets |
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what are polyurethanes? are they easily foamed? what are its uses? |
polyurethanes are soft stretchy materials like spandex easily foamed -> 40% of PU is foamed by mixing with blowing agent used mainly for garments |
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what are silicones? what are its features? uses? |
silicones are high-performance high-cost materials most chemically stable of all elastomers but low strength uses: breast implants, adhesives, wire/cable insulation |
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what are polyesters (PET)? what are its features? uses? |
thermoplastics that are mineral-filled and glass-fiber reinforced and withstand high pressures -> can also mimic elastomers used for carbonated drink containers, brushes, boats, car parts |
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what is polyethylene? features? uses? |
strong mechanical stiffness and strength uses: milk bottles, toys, oil containers |
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what is added to resins to make them flow better into molds? what does adding this product do to the resin that normally produces a rigid product? |
plasticizers if added to a resin that produces a rigid product, it makes it flexible and rubberlike |
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what is added to resins so that the finished product is coloured throughout? why does this make plastics have an advantage over wood/metal? |
colouring agents advantage over wood/metal cuz colour can only be added on the surface for those |
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how did Goodyear make illuminated tires? |
Goodyear experimented with a petroleum based rubber that was near transparent and mounted them on a set of wheels with lights on the inner rim -> illuminated tires! |
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what is hydro printing/dripping? how does it work? |
method of applying printed designs to three dimensionalobjects (e.g. curved) 1. polyvinyl alcohol film is gravure printedwith the graphic image to be transferred, and is then floated on the surface of a vat of water 2. activator chemical is sprayed on the film to dissolve it into a liquid and activate a bonding agent 3. piece is then lowered into the vat, through the floating ink layer, which wraps around and adheres to it 4. top coat applied to protect the design |
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what is the process of flocking? |
fibers are first adhered to the part surface, followed by electrical charge to make the fibers stand erect |
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what is metallization available by? |
metallization is available via electroplating and sputtering vacuum metallization |
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what does sputtering provide? what does it require and what is the process? |
provides a bright, durable metallic finish with abrasion resistance requires the use of a base coat and topcoat that sandwich a metallized layer bombarded with ionized molecules that cause the atoms to break away from the target metal and then deposit on the plastic metal |
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why can a fly walk up a window plane? |
seemingly smooth sheet of glass to our fingers feels very even and slick but any material magnified under the microscope will be revealed as craggy and rough |
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what 3 things can wear be caused by? |
wind water human appendages/factors |
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why are tires designed to wear down on a hard surface? |
if they were harder than the road surface, they would not provide traction or be resistant to things like potholes or road imperfections |
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what happened with rot and wooden British airplanes? how did they check for rot? |
aircraft were left outside in the rainy English and tropical war theatres, the compartments of the wooden fuselages began to collect water rot, either in the glue or wood would develop within a few months only way to check for rot was to check for bad smells |
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what did Henry Ford do with soybeans? |
he was aware of the limitations of steel as a building material for automobiles and researched into alternate materials, such as plastic derived from the lowly soybean he built a car that used plastics from soybean and a steel frame and it was 25% lighter than conventional cars problems: looked conservative and not futuristic and the controversy of the composition of the plastic |
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what is hydrolysis? |
a process which decomposes plastic materials into their original building blocks use high pressure steam to hydrolyse (hydro=water, lyse=splitting) polyurethane foam |
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when does the degradation of plastics begin? when does it increase? what can it be followed by? |
as soon as the polymer is synthesized, and increased by residual stresses leg by molding processes can be followed by exposure to light (especially UV), humidity, oxygen, heat, bacteria and stress |
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can biodegradable plastics be recycled? can photodegradable plastics be recycled? |
biodegradable can't because the starch or oil additives compromises the quality of recycled plastics photodegradable can because they don't contain organic additives |
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how do we respond the near-term problem of reducing the impact of usage? |
do more with less material reductions are made possible with recycling, by the use of renewable materials made from things that grow, by miniaturization and by replacing goods by services AND we can also design products to have a longevity or long product life |
