CREEP DEFORMATION

By: Nikolas Anthony Bryan-Dunaway

In Engineering Materials

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

What Is

Next?

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

Why Read This?

PURPOSE STATEMENT

The purpose of this presentation is to familiarize you as an up and, coming engineer, with the concept of creep deformation in engineering materials. Common

creep testing machines

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

Creep Deformation Defined

INTRODUCTION (1/3)

Question:

What is Creep Deformation?

Answer: Creep deformation is a naturally occurring situation where a material becomes stretched, or deformed, by being subjected to constant forces at a given temperature. It is a function of changing strain over time.Guitar Strings

Become Detuned after initially being strung because of creep deformation.

INTRODUCTION (2/3)

First, lets define strain.

Strain, in engineering, can be defined as the direct proportionality of the change in dimension and the inverse proportionality of its original dimension such that:

New Dimension –

Original Dimension

Original Dimension Strain

INTRODUCTION (3/3)

A graphic representation of creep. -The Stages of Creep-

Stage 3: “Necking”- the strain becomes exponential because of “necking”, or, the rapid reduction in cross sectional area.

Stage 2: Linear strain- Strain increases at fixed rate due to work hardening (becoming stronger under stress) and annealing (thermal softening) which happen simultaneously throughout portions of the material.

Stage 1: Initial Strain- Material is “strain loaded” which seems to be almost instantaneous after which the strain rate begins to drop off.

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

A Case In

Study

MATERIALS & METHODS (1/3)

We conducted our own creep test. This is what we used to perform the experiment:Materials:

1. 24-30in, 0.093 Gauge Solder Wire, 60% Tin-40% Lead (2)2. 1200g Weight (1)3. 1500g Weight (1)4. Wooden Dowel (1)5. Work Shop Tool Mounting Hooks (4)6. Workshop Tool Mounting Board (1)7. Yard Rulers (2)

MATERIALS & METHODS (2/3)

•We started by hanging the wooden dowel on the mounting hooks that were fixed to the board

Step 1

•We then fixed two pieces of wire to the dowel by winding the material around it.

Step 2

•Finally we set two yard rulers parallel to each wire and fixed them in place by tape.

Step 3

•We marked two gauge points on the wire within the rulers measurable area and attached the weights at the ends of the wires.

Step 4

Wooden Dowel

Mounting Hooks

Solder Wire

Yard Ruler

1200g Weight

1500g Weight

Mounting Board

Gauge points at which to calculate change in length.

-Experiment Setup-

MATERIALS & METHODS (3/3)

We let the samples sit for a couple of weeks. The

experiment took place indoors at room temperature.

We took measurements by reading the measurement

coinciding with the marks and subtracting the two to

get our change in length. We repeated this process a

few times during the day. After finishing, we plotted

the data and determined the wires creep deformation

graphically. We measured the time since the start of

the experiment in cumulative minutes.

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

Graphical Interpretatio

n

Analysis (1/3)

After conducting the

experiment we saw

that our graph looked a

lot like the graph at the

beginning of the

presentation. Look at

the graph again. 1.0001.5002.0002.5003.0003.5004.0004.5000.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

CREEP OF 60%Sn-40%Pb SOLDER w/1200g Weight

CREEP CURVE

LOG (TIME,MIN)

STRA

IN (Δ

L/Lo

)

Analysis (2/3)

1.0001.5002.0002.5003.0003.5004.0004.5000.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

CREEP OF 60%Sn-40%Pb SOLDER w/1200g Weight

CREEP CURVE

LOG (TIME,MIN)

STRA

IN (Δ

L/Lo

)

Analysis (3/3)

Our graph is missing stage 1

of the creep deformation.

The reason for this is

because this stage happens

very rapidly, especially in a

material like solder, and we

were unable to record the

early stage of creep. 1.0001.5002.0002.5003.0003.5004.0004.5000.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

CREEP OF 60%Sn-40%Pb SOLDER w/1200g Weight

CREEP CURVE

LOG (TIME,MIN)

STRA

IN (Δ

L/Lo

)

OUTLINE

Purpose Statement Introduction (1-3)Materials & Methods (1-3)Analysis (1-3)Conclusions

And so…

CONCLUSIONThis presentation was created to provide other

engineers with a familiarization of creep deformation.

In the process of experimenting and recording data on

the test samples, I believe we achieved that. Creep

deformation is fundamentally important in the use and

assignment of engineering materials to projects when

time is important. Creep deformation can be defined

by the deformation of a material at a constant

temperature while under constant forces.

THE END

REFERENCES Buddinski, K., & Buddinski, M. (2010). Engineering

Materials: Properties And Selection. Upper Saddle River: Pearson Education.

Horton, H., Jones, F., Oberg, E., & Ryffel, H. (2008). Machinery's Handbook: 28th Ed. New York: Industrial Press.

Kopeliovich, D. D. (2009, Febuary 3). Creep. Retrieved November 7, 2010, from substech.com: http://www.substech.com/dokuwiki/doku.php?id=creep

Wikipedia.org. (2010, October 15). Creep (deformation). Retrieved November 7, 2010, from Wikipedia.org: http://en.wikipedia.org/wiki/Creep_(deformation)