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# Lab 9 Behavioral Materials

By Louise Ward,2014-05-07 21:19
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Lab 9 Behavioral Materials

Lab 9: Behavioral Materials

Background: In this lab you will repeat a few simple measurements on many different kinds of

materials to appreciate their different properties which include elasticity, thermal conductivity

and diffusivity, density, opacity, and their coefficient of thermal expansion.

Beam Deflection Setup (not to scale)

Displacement Indicator

Test Plate

Dowel Pin

Sample

V- Block

Vertical Stand

Spring scale

Common Deflection Definitions

Quantity Definition Symbol Units English Units

-2psi tension/area = F / A Stress N m = Pa ? (sigma)

extension per original no units no units (ratio Strain ???epsilon??of two lengths) length = ?x / x

1

Young’s Modulus psi -2stress/strain N m = Pa ??= Modulus of Elasticity

Vertical Load deflection force W N lbs

δ Deflection elastic deformation m in

l Length sample length m in

434Moment of Inertia I in= (1/3) * b * h m ??xx

To measure Young’s modulus by deflecting the sample under a measured load

? Repeat this exercise for each of the following:

o Aluminum (pick an alloy) o 2 Plastic samples

o Stainless steel

? Measure the sample’s dimensions [width (w) x thickness (h) x height (b)] with calipers

? Set up the sample as shown in the figure on page 1

? Lift the vertical table using the black pedal until a noticeable deflection can be measured

by the displacement indicator. Write down both the deflection and the measured load as

? Use the following formula to calculate the Modulus of Elasticity for the material.

3W?l?? 48?E?I

Thermal Properties Setup

Displacement Indicator

Thermocouple to Thermometer

Heat Gun Sample V Block

Test Plate

(To relatively measure the thermal conductivity, diffusivity, and coefficient of thermal expansion

of each sample)

? Do this experiment for one sample of aluminum, titanium, and stainless steel

? Measure the sample’s original dimensions

2

? Hold the sample in your hand

o Does it feel warm/cold after 10 seconds?

o Based on this, rate the samples from least to highest thermal conductivity

? Place the sample in the setup as shown

? You will need three people to take three different measurements: 1 keeps track of time, 1

writes down the temperature reading from the thermometer, and 1 records the

measurements from the displacement indicator

? Heat up one end of the sample to for 20 seconds. Every 5 seconds, write down the

required measurement.

? As the sample cools, take measurements every 20 seconds for 1 minute.

? What relationship does your data indicate?

? If available, use the IR thermal sensor to measure the temperature per length of the

sample, make similar measurements

Common Thermal Definitions

Quantity Definition Symbol Units English Units

see eq. below Thermal conductivity k W/(m K) Btu?ft/(h?ft???F)

22Area surface area = b * h m ft ??

Temperature difference T-T ΔT?K psi 12btwn ends of sample

Time difference t-t Δt s s endstart

Added heat from heat gun ΔQ J BTU ft Thermal diffusivity see eq. below m in ??

33Volume A*l V m ft

In terms of the added heat (Q), what is the thermal conductivity and diffusivity?

?QxThermal conductivity: k??A??t?T

k??T?Thermal diffusivity: ?V??Q

new_length

original_lengthCoefficient of thermal expansion: end_temperature

Spring Wires

Goal: Become familiar with elastic materials often used in flexures and other optical mounts

? Cut off a measured amount of wire and bend into a right angle, then try to bend it back to

its original shape

? Use the shape-memory wire to make your name, heat it up with the heat gun, stretch it

out, then lay it on the table

3

Optical Windows

Goal: Have student become familiar with different optical materials, weight, opacity, etc

? Calcium Fluoride ? Sapphire

? Silicon ? Zinc Selenide

? Germanium ? Zinc Sulfide

Specific Heat Capacity

The specific heat capacity (SHC for short) for a material is an intrinsic property of a material that

is the measure of the heat energy required to increase the temperature of a unit quantity of the oC). To measure the material by a certain temperature interval. SHC is usually reported in J/(g?SHC of a metal, we are going to use a calorimeter, which is just a thermally isolated environment

which obeys the laws of thermodynamics (primarily that energy is neither created or destroyed).

By following this law, a material with an unknown SHC will transfer its energy to either a

material with a known SHC or to the environment. When all three (water, matel, and

environment) have the same temperature, the following equation determines the SHC for the

unknown material

?????C?mCT?Tcalwaterwaterwater C?metal??mT?Tmetalmetal

where T is the final temperature, Tis the initial temperature of the water, T is the initial water metaltemperature of the metal, m is the mass of the water, m is the mass of the metal, C is the watermetalcalspecific heat capacity of the calorimeter, C is the SHC of water, and C is the SHC of the watermetalmetal in question o-1 C=4.184 J C water

C=NEED TO DETERMINE (hopefully get it from Michael) cal3 ρ=0.9982 g/cm (for pure water @ 20 ?C) water33 1 fl oz=29.5732 cm (1 ml=1cm)

4

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