Engineered Products Flashcards
What happened when electricity was introduced to society?
Most duties at home went from being manual labour to having electrical appliances to assist them.
What is the transmissibility of forces?
does not matter here strong person is in a tug of war; doesnt matter what order forces are acting in
What is the three force axiom?
if three forces are on a body in equilibrium all forces are concurrent (graphical)
What are moments? whats the formula? unit?
a turning effect
M=F*d f is force, d is perp. distance
Nm
What is a couple? Whats the formula?
two parallel forces of equal magnitude but opposing direction form a ‘couple’ which creates a turning effect.
M=F*d where f is the force and d is distance between them
What are ethics?
doing the right thing.
Why would we reduce, reuse and recycle? 4
less waste, limited materials, limited energy, ethical
What is the difference between hot and cold working?
Hot working is above the recrystallisation temperature, cold working is below it.
What happens when a material is cold worked?
equiaxed grains turn elongated; in chemical structure, tangled forest of dislocations –> energy loss –> work hardening
What is grain flow?
Grain flow occurs when an object is worked and not cut into shape. It is when the grains are curved to follow the shape of a product, so there are no weak grain boundaries
Compare cold working (5) to hot working (4)
Cold - No heat, more force –> bigger machines, no oxides (bright steel), higher hardness and strength, lower malleability and ductility
Hot - heat=money, less force –> smaller machines, oxide layer (black steel), no property change.
What are the three phases of recrystallisation of metals after cold working (both names of each stage, and briefly what happens in each stage.
Recovery/stress relieving- nothing really happens; internal residual stresses relieved
Recrystallisation/normalisation - elongated grains –> small equiaxed grains - decreased hardness and strength, increased ductility
Grain Growth/annealing - grains get big, ductility increases
What affects the recrystallisation temperature?
the type of metal and how much it has been worked
What is heat treatment?
the process of improving/changing the properties of a material (usually metal) by the controlled heating and/or cooling of the material.
Heat treatment - what does hardening do?
hardens material
usually stronger but brittle
Heat treatment - what does tempering do?
toughening
Heat treatment - what does annealing do?
Softening
Heat treatment -What is normalising?
refining grain structure e.g. recrustallising elongated grains to remove grain defects
What are two ways of changing the properties of metals?
heat treatment, alloying
What is an alloy?
a mixture of two or more metals OR a non-pure metal that acts like a metal
GENERALLY what does alloying do to strength, hardness, corrosion resisitance and ductility?
increase strength
increase hardness
decrease corrosion resistance
decrease ductility
What are 2 other names for voltage? what is it cause by?
voltage or EMF, caused by difference in charge (-ve–>+ve)
What are the parts of an engineering report and what they do?
Title page
Abstract - summary of entire report to prevent unnecessary reading
Intro - sets the scene
body
conclusion; recommendation, make a decision
references; for further studies, prevents plagiarism, credibility
appendix; extra information
What is Ohms law?
V=IR
