- Created by: helizm69
- Created on: 11-04-18 16:31
Factors affecting choice of material?
- hardness and rigidity
- weight and stability
- flexibility and buoyancy
- texture and colour
- wastage and electricity
- labour costs and new training
- repair and servicing machinery
- hard/easy to work with material(gold easy to work with and easy polished as it is soft)
- most products come in stand forms, shape and sizes.
- wood-sheet, plank, box section, tube, coils of wire
- metal-sheet, plate, box section, tube, rod, coils of wire etc.
- plastic-sheet, rod, tube, block etc.
welding-heat, molten metals joined with joining material.
brazing-copper adn steel joined under heat, with rod made of copper and zinc alloy.
soldering-lower temperature than brazing.
riveting-metal pins thorough sheets or plates and hammered.
adhesives-with glue eg.PVA, contact adhesive, epoxy resin
frame joints-**** joints, halving joints, mortice tenon, dovetail joints
can be disassembled
screws,nuts,bolts and washers
snap joints-moulded plastic components
knockdown fittings-screws, corner blocks, self assembly fittings
- amount fo matter(mass) in an object
- mahogany denser than pine
- dense material, less buoyancy
- movement of electricity through a material
- good conductors-gold, silver,copper, some gases
- insulators-woods, ceramics, glass, plastics eg.PVC, acrylic
some semiconductive eg.silicon and germanium
- movement of heat through a material
- asbestos great for keeping heat in and silica tiles also used
- cooking utensils prevent burning
- double glazed windows-glass and air to create barrier and polysterene pumped into cavaties
mechanical properties of a material are related to how the material reacts to various forces that it may be subject to.
deformation is when the force is to significant for the material to endure. There are two types of deformation being temporary(elastic) and permanent(plastic).
the materials ability to withstand force without it breaking or permanently bending.
tensile strength-ability to resist pull forces and used for cables, chains and ropes.
compressive strength-ability to withstand push forces that try to crush or shorten it.
bending strength-force applied to a material in an attempt to bend it.
shear force-force that subjects materials to sliding action across their surfaces. eg.hinges, scissors, secateurs, hedge clippers or drill bits.
torsional force-force that is applied to a material to try to twist it. also known as torque.
Ability of a material to flex, bend and be deformed and return to its original shape when forces are removed eg.elastic band.
ability of a material to permanently change shape when forces are applied without cracking or breaking.
degree to which materials can be deformed in all directions by a compression force such as hammering, pressing or rolling without cracking.
ability of a material to be drawn out longer and thinner eg.wire, by a tensile force. all ductile materials are malleable but not all malleable materials are ductile.
ability to withstand sudden shocks or blows. tested using a large pendulum which swings to hit a notch in the material. the tougher the material the more impact it can take.
Ability to resist indentation.eg.with centrepunch.
scratch tests-minerologists rank scratch resistance of materials. diamond is the hardest material known to man-used in drill bits.
indentation tests-forcing a hard object intot eh surface of a material. the result affected by SA.
brinell test-hard steel ball like shot put
vickers test-pyramid shaped diamond tool
rockwell test-steel ball or diamond cone
capability of withstanding wear and teat and deterioration as a result of weathering. eg.meatls prone to corrosion.
opposite of plasticity and is like a human bone breaking. materials that are brittle break or shatter eg.castiron ro glass. brittle materials possess high compressive properties but low tensile properties. eg.castiron is not used in bridge building.