♪ piano background music ♪

(Alan) Non-destructive testing covers

a wide range of techniques

used in industry and science.

And the samples are evaluated

in terms of their material properties

without causing any damage

and is therefore often carried out

in the workplace.

(Steve) Non-destructive testing

is extremely important to industry

because it allows the component

to be used after it's been tested.

OK, what we've got here is

Dye Penetrant Testing,

a very, very simple test

and it's used to detect open pores or

cracks that break the surface.

This is quite important because

if these defects go undetected

it could lead to some catastrophic

failure and potentially deaths.

We've got the dye.

We've got cleaning fluid. OK.

And we've also got some developer

like a talcum powder substance.

It's a very, very simple

technique to do so

you'd be using it in aerospace,

you'd be using it in railways,

you'd be using it in heavy industry.

The uses are pretty much limitless.

So first we need to clean the sample

to get rid of any grease or dirt.

[spray hisses]

And then we're ready

to apply the penetrant.

[spray hisses]

And then you've got to give it

sufficient time for the penetrant

to seep in to any

surface breaking defects.

The finer the defect

you're trying to detect,

the longer you need to leave it.

OK, so this has been sat for about

20-30 minutes, and it should be

sufficient time for

the penetrating media

to seep into any open voids.

OK. So the next stage of this

is we've got to wipe off

any excess penetrant.

Get a rag, some of the cleaner.

Spray the cleaner onto the rag

and then just wipe off any excess.

Nice and simple.

The next section is

to get the developer...

and we give the surface

a nice, liberal, even coating.

[spray hisses]

OK, so we've left this sample

10 minutes to develop,

and what we can see is there's a crack

emanating down the middle

of this sample. You can see that,

all the red that's coming out.

You can also see it

round these holes and

round the edges that's just where

we didn't clean inside the holes

and inside the edges

so that penetrant is then being

sucked back into the developer.

What we've got here

is one that came in from testing.

This is a real life component.

This is the bottom of a glass mould,

and on the back of that we've done

a Dye Penetrant Test and you can see

about 4 nice fine cracks than run

all the way through that specimen.

OK, so that's Dye Penetrant Testing.

A very nice cheap and quick way

of detecting defects without damaging

the actual component or material.

OK, the next test we're going to do is

Magnetic Particle Inspection.

And for that, we need a fluid

containing some magnetic particles,

we need a background contraster,

and we need a cleaner.

We also need a magnet.

Now we've got an electromagnet here.

You can also use permanent magnets,

although the difficulty is taking them

off if you've got nice strong magnets.

So the advantage of this technique over

Dye Penetrant Testing is that you can

detect slightly sub-surface defects.

The main disadvantage is that you've

got to be able to magnetise the

materials so non-magnetic materials

you can't test using

Magnetic Particle Inspection testing.

So the first thing we need to do is

clean the sample.

[spray hisses]

And then the next stage is to spray on

your contrasting background.

And then give it a nice, even coating.

[spray hisses]

And then we need to leave it to dry

before we can apply the ink

and the electromagnet.

OK, the sample's now dry so we need to

bring the sample in contact with the

electromagnet.

I'll need to make sure

we get good contact there.

Turn on, to magnetise the sample

and we spray on the magnetic ink.

[spray hisses]

So what's happening here is

we're inducing a magnetic field

into the material,

if there's defects within the material

those can deviate the lines of

magnetic field

and that's where the magnetic ink

that we sprayed on will congregate.

And that's what we can see here.

If we'd have been testing

this component in industry,

because we've identified these cracks,

which are detrimental to the component,

we'd just probably throw it away.

If we didn't see any cracks,

if it was deemed as good,

then we'd have to make sure that

we cleaned it off so that any materials

on here that might want to contaminate

the component for further work

or its service life.

OK, just to recap then, the

Dye Penetrant Test allows us to detect

surface breaking defects.

The Magnetic Particle Inspection allows

us to detect slightly sub-surface

defects, and what we've got here is

Ultrasonics. And that allows us to look

right inside the material.

OK, so this is us sample,

this is us ultrasonic probe,

and this is where we can see the signal

coming back and detect any

potential differences in the material.

So this is exactly the same sort

of technique you'll see in hospital,

maybe looking at babies, maybe looking

at kidney stones, that sort of thing.

OK, first of all we need to put on

a couplant. And this is something that

excludes air from the sample

and the probe.

Sound doesn't travel very well

through air, so we need to exclude

as much of it as possible.

Once we've got the couplant on,

we pop us probe on top and then

give it a wiggle round to exclude

any air. OK. So the width of this

screen is the equivalent of

100mm depth. Now at the end of this

screen you can see there's a spike

there, and that's the reflection

from the back wall of the sample.

As we traverse along this sample,

what we'll start to see...

is... a spike appearing at about

45mm there. Which is a reflection

from this top surface here.

As we continue to traverse, we get a

reflection at about 15mm and what

that is is a defect 15mm down from

the surface.

Again, continuing the traverse,

because that's only a small defect

that disappears whereas we're still

detecting this defect that's 45mm down.

If we carry on traversing across,

eventually the one at 45mm disappears

and then we start getting the back wall

signal reappearing at 100mm.

What makes ultrasonic testing different

to some of the other non-destructive

testing techniques you've seen is that

it can detect defects, maybe

gas as little bubbles or tiny cracks

within the material but those could be

meters away from the surface

of the material. And that makes it

a very powerful technique.

(Alan) This is a Scanning Electron Microscope.

This is the most sophisticated bit of

equipment we have in the

Materials Research Institute.

The Scanning Electron Microscope

enables us to do two or three things

that we haven't been able to do with

optical microscopy. The first is we can

now look at material at very high

magnification.

An optical microscope will only go

up to about 1000 times magnification.

With the electron microscope, we could

be looking at 500,000-800,000 times

magnification.

It's no good just making things bigger

if you can't then resolve the detail.

The electron microscope gives us

extremely good resolution

at very high magnification.

It's actually made up of some

very small, simple ideas

which if you bring them all together

make it into an incredibly sophisticated

piece of equipment.

At the top of the column

there's a tungsten filament.

That filament is heated up

and that gives off electrons.

The electrons come down the column.

They're focused by the electromagnets

onto the surface of the sample

and there they do two things.

One is that they create the image that

we see on the screen and the other is

that they allow us to do some chemical

analysis of the sample if we need to.

Basically put, the electrons hit into

the surface of our sample fairly hard

and knock out electrons

from the surface which are

characteristic of the element which

the sample is made from.

With this bit of equipment, we can

really get to almost the atomic level

to say what's controlling

and influencing the material behaviour.

As a Materials Engineer I love this

piece of equipment because we can do

so many incredible things with it.

We can use it to develop new materials,

we can use it to enhance existing

materials and we can even use it to

solve crimes in Forensic Engineering.

Forensic Engineering uses the

fundamentals of maths, physics and

some inorganic chemistry to inform and

augment legal argument.

A classic forensic investigation that

we get involved in here is where

there's been a road traffic incident.

Two cars have collided. One claims that

it's the other car's fault because he

didn't have his lights on and therefore

they couldn't see it. The police bring

the broken lamps to us and ask us

if we can establish whether the lamp

was illuminated just prior

to the collision.

And we can do that,

using our electron microscope.

So the chamber's now evacuated.

We've turned the electron beam on.