Unit 12 MECHANICAL PROPERTIES

Material properties

Toby: That’s certainly a scary-looking collection of tools.

Ester: Yes, some of them do look quite menacing, don’t they?

Toby: Is that titanium? The drill handle?

Ester: Um… yes.

Toby: I’m an engineer, that’s why I, am…

Ester: Oh, I see. Yes, titanium’s great. It’s expensive, obviously, but very light. That’s the advantage. Ideally, you want it to be lightweight, to give better control.

Toby: Nn…

Ester: These are the most impressive things, though, the burs on the end. The latest ones can rotate at over half a million revs per minute.

Toby: Nn.

Ester: They are coated with tungsten carbide, which I think is one of the hardest materials in existence, isn’t it? Along with diamond. That’s also used.

Toby: Nn.

Ester: The requirement is abrasion resistance, of course. Obviously, they need to be very durable. And you don’t want them snapping either. The last thing, you want is brittle material. Apparently, that was the trouble they had in the past, making the bur tough enough so it didn’t break. I think part of the problem was heat, as well. Drilling into a tooth at high speed, you obviously get a lot of heat build-up. You need a good degree of thermal stability.

Toby: Nn.

Ester: See what I mean? You can actually smell burning. And that’s after a few seconds. Imagine the heat build-up after several minutes.

Unit 13 NUMBERS

Conversation 1

“When you are going away on holiday?”

“On the ________” (15)

“And when do you get back?”

“On the __________ I’ll give you a ring when we get home.” (24)

Conversation 2

And now the business news. The unemployment rate has risen slightly this month. The national unemployment rate is now __________ and in our area, an estimated __________ people are out of work. (4.2%, 15,000)

Conversation 3

“Can I pay by visa?”

“Yes, that’s fine. Erm – what’s your card number, please?”

“It’s __________ (4929 … 7983 … 0621 … 8849)

“Let me read that back. _____ … _____ … _____ … _____”.

“That’s right”.

Unit 14 NUMERALS

When I was a kid I was top of the class in maths. I was really good at mental arithmetic and doing sums. Things were easy back then, It was all addition and subtraction, multiplication and division. I knew my times tables like the back of my hand. Then, things got difficult when I was about 14. We had to learn stuff like algebra and geometry and lots of other stuff I can’t remember the names of. Suddenly. I wasn’t so good at maths any more. I think there were a few reasons for this. One was my maths teacher, another was because I sat at the back of the class, and another was I talked a lot. I still like maths and know I would be good at it again if I studied. I did statistics when I was at university and loved that.

Unit 15 GEOMETRIC FIGURES

Dimensional

3-Dimensional, 3-Dimensional, this means the shape or something has three dimensions that means a curves up and down, side to side and front and back. That is 3-D. The opposite would be 2-D. So on the computer screen everuthing is 2-D. This is up and down and side to side. For 3-D you need 3-D classes for depth perception.

Unit 16 MEASURING INSTRUMENTS

Gauge

Gauge, sometimes also spelled “gage”, means to estimate the size or amount of something. A gauge is also a tool such as a speedometer inside a car to see how fast the car is going. See the additional examples below:

I wasn’t able to gauge how tall he was from the pictures.

The gauge was broken so I didn't know the temperature was so high.

Unit 17 INVENTIONS

CHRISTOPHER CRUISE: Kevlar is another invention that has saved many people from serious injury and death. Kevlar is a fibrous material with qualities that make it able to reject bullets. Added to clothing, the material protects security officers and soldiers across the world.

The fibers form a protective barrier against gunfire. Bullets lose their shape when they strike Kevlar. Those bullets look like mushrooms, and do not enter the body. Most threats to police and security officers come from handguns. They wear Kevlar vests to protect the upper body. Soldiers wear more extensive clothing protected with Kevlar against heavier ammunition.

BOB DOUGHTY: Kevlar might not have been invented had Stephanie Kwolek been able to seek a career in medicine. From childhood, she wanted to be a doctor. But she lacked the money for a medical education.

Today, thousands of people are glad that Stephanie Kwolek became a research chemist. In that job, she developed the first liquid crystal polymer. The polymer was a chemical product that formed the basis for Kevlar.

BOB DOUGHTY: By the nineteen sixties, DuPont already had produced materials like nylon and Dacron. The company wanted to develop a new fiber. Stephanie Kwolek was part of a DuPont research group that asked to work on its development.

Date: 2015-12-11; view: 1318