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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

    Bucket with lead weights

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

    read from the spring scale.

    ? 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

    start_temperatureDo your relative measurements match your predictions from above?

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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