Engineering Marathon (2 Viewers)

[Kaos1]

will that leads me to this question. HOW is glass formed and what is special about toughened glass in the way it was formed?

glass is formed by heating up and melting silicon, floating it on tin to get an eaven, smooth finish, and left to cool / harden

tempereing glass happens after it is finished cooling, and is done by fiering either side of the class to create tension on either side, so if its chipped, it shappers into a million and one pieces

 

[qwertyuiop1234]

an induction motor is chosen for a door lifing mechanism.

outline TWO reasons for this choice of electric motor

good torque (for lifting loads)
low maintenance (doesn't have brushes or any wearing parts)

 

[Kaos1]

2nd part of that question:

what is an induction motor?

 

[qwertyuiop1234]

2nd part of that question:

what is an induction motor?

An induction motor is set up like a squirrel cage with conductors running down the sides, two electromagnets are placed 90 degrees apart with a capacitor between them. The magnets induce a current into the cage and this sets up another field opposing the first one (lenz's law). The two fields repel each other and because the 2 magnets are 90 dgerees out of phase the second magnet attracts the conductor and it keeps going round like that at 3000rpm. Don't know how clear that is, might be easier to find a picture of it

 

[Kaos1]

various systems within a race car can cause interference to radio signals.

Identify ONE source of interference and explain why an FM signal is relatively immune to this form of interferecne

 

[qwertyuiop1234]

Interference can come from many sources such as other electronic equipment. This outside 'noise' does not affect FM because FM relies on the change in frequency not amplitude and the noise does not affect the frequency.

 

[Kaos1]

cummmmooooonnn!!

anyone got any questions for us?!

 

[ShowStopper]

alright guys last question, you need to relax now before the exam.

Explain Annealing, Normalising, Hardening and Tempering. Include all details of the processes, mechanical properties achieved and grain structures.

 

[bossleymaths]

alright guys last question, you need to relax now before the exam.

Explain annealing, normalising, hardening and tempering. Include all details of the processes, mechanical properties achieved and grain structures.

owned!!!

 

[Kaos1]

annealing: fired to austinisation temp, coled in furnace. provides large grains, & relatively sift material.

normailising: fired to austinisation temp, cooled at room temp. provides equiaxied grains, eavenly flexible, maluable, hardened metal.

hardening: process of heating up to a temprature well below austenisation temp, and quenching, cooling at room temp or cooling in furnace depending on specificationg

tempering: again, process of heating and cooling similar to hardening, but to a different specification; usually for a tougher application, and impact resistant

 

[tashisthebest]

alright guys last question, you need to relax now before the exam.

Explain Annealing, Normalising, Hardening and Tempering. Include all details of the processes, mechanical properties achieved and grain structures.

thas a tough one

>Annealing- when the ferrous metal is heated in a furnace above its critical temperature and to a point when its uniformaliy austinite, the metal is then cooled at control temperature within the furnace. the metal can return to equlibrium state, achiving larger unstressed grains, induces softness and improves magnetic and electrical properties of the metal.

>Normalising- Heating the metal just above its critical temp (usually only above by 30 degrees), this austines state of the metal is then allowed to cool in still air. Creating fine grain structure, increased UTS, yield strength and hardness but reduces ductility.

>Hardening - when the steel is heated to its asutiniet state and then quenched quickly, this quick change in temp doesnt not all the FCC austine to change into BCC ferrite and thus causing the steel to be trapped in a Body centered tetragonal structure. Steel becomes very hard but also brittle

>Tempering- When harden steel is once again heated to temp between 200-600 degrees (dont know what they to cool it). due to pricipitation of cememtite it reduces internal stress, tensile strength and hardness. it also improves ductility and toughness.

 

[tashisthebest]

What is Precipitate hardening?

 

[arman]

thas a tough one


>Tempering- When harden steel is once again heated to temp between 200-600 degrees (dont know what they to cool it). due to pricipitation of cememtite it reduces internal stress, tensile strength and hardness. it also improves ductility and toughness.

i'm pretty sure tempering is air cooling

What is Precipitate hardening?

also known as age hardening, copper or silicon (notsure) content of aluminium is dispersed evenly throughout structure

 

[madsam]

i'm pretty sure tempering is air cooling




also known as age hardening, copper or silicon (notsure) content of aluminium is dispersed evenly throughout structure

Not quite

Tempering is reheating below RC temp to convert martensite back into pearlite

Precipitate hardening
1. Heat your alloy (usually an aluminium alloy) above RC to form a single phase homogeneous structure
2. Air cool it, thus "trapping" the single phase in the structure
3. re heat it to about 100-200 degrees to allow some of the phase to 'precipitate out' into grain boundaries, improving strength and hardness while decreasing ductility
4. This will continue to occur throughout the lifetime of the material, getting harder and more brittle as time goes on