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MET 311
EXPERIMENTAL MECHANICS

3 CREDITS                       Fall 2014

 

 

 

 

TEXT:

Strain Measurements and Stress Analysis by Khan and Wang

 

PREREQUISITE:

Grade of C or better in MET 211

 

INSTRUCTOR:

Mark French

 

OFFICE HOURS:

8:00 – 10:00 M-F

 

OFFICE LOCATION:

121 Knoy Hall,

Desk: 765-494-7521

Cell: 765-714-9382

 

EMAIL CONTACT:

rmfrench@purdue.edu

 

LECTURE LOCATION:

ME 1051

 

LECTURE TIMES:

  T-Th 9:30 – 10:20

 

LABORATORY LOCATION:

Knoy Hall, Room 106

 

LABORATORY TIME:

Sec 1: T  3:30 – 5:20

Sec 2: W 3:30 – 5:20

 

GRADING:

 

 

A: 

> 90%

Exam 1

20%

B: 

80% - 90%

Exam 2

20%

C: 

70% - 80%

Homework:

15%

D:

60% - 70%

Labs: 

20%

F: 

< 60%  

Project:

25%

 

 

 

Week

 Date

Topic

Reading

Homework

 

 

 

 

Homeworks are due one week after the day they are assigned

1

8/26

Class Intro,

Strength of Materials Review

Axial Stress and Deformation

Torsional Deformation

 

 

 

 

8/28

Strength of Materials Review

Stress and Strain

Material Properties

Beam in Bending

Load-Shear-Moment Diagrams

 

No Lab in Week 1

 

 

2

9/2

Strength of Materials Review

·         Combined Stresses

·         Stress Concentration

What is a Radian? Two-bar truss Review Problem

Statically Indeterminate Problem 

HW #1:  Wing Strut Loads

 

Due: 9/9

9/4

Strength of Materials Review

Long Column Buckling

Short Column Buckling

Distributed Load Example

 

Combined Stress Example

 

Another Combined Stress Example

 

 

 

Lab 1 – Acceleration of Gravity

It might help to have examples of technical articles to review as you write your reports.  Here are some that appeared in a journal called Experimental Techniques. 

 

A Conical Laser Vibrometer Mirror

Weight Falling onto a Spring

Pop Bottle Resonator

 

 

 

 

 

 

3

9/9

Introduction to Mathcad

 

 

 

 

9/11

Strength  of Materials Review

Mathcad Review

Mohr’s Circle

 

HW #2:  Combined Stress

 

1 - For structure in Problem 1, compute stress along the top of the beam for each pin position. Assume the beam is 1” wide and 8” high. Find only the stress on the upper surface of the beam

 

Due: 9/18

 

 

 

Lab 2 – Measurement Variation

 

 

 

4

9/16

End of Strength of Materials Review

Pressure Vessels

 

Pressure Vessel Example 1

Pressure Vessel Example 2

HW #3:  Buckling

 

For structure in problem 1, find minimum weight strut for each pin position

 

Information on Streamlined Tubing

 

  Tensile equivalent is based on cross-sectional area.  Compressive equivalent is based on area moment of inertia.

 

Due: 9/23

 

 

 

9/18

Strain Gauges, Bridge Circuits

Chapter 2

HW #4:  Buckling and Pressure Vessels

(Use K=2) also, assume material is  stainless steel - yield stress is 400 MPa and E=190 GPa.  The wall thickness is 1.0mm

 

Due: 9/25

 

 

Lab 3 - Measuring Area Moment of Inertia

 

5

9/23

Strain Gauges

 

 

 

9/25

Bridge Circuits

 

HW #5: 2.4, 2.6

 

Due: 10/2

 

Lab 4 – Making Bridge Circuits

 

6

9/30

Bridge Circuits

 

10/2

Bridge Circuits with Two Gauges

 

HW #6:  Half bridge with strains due to load and to thermal expansion

 

Due: 10/9

 

 

Lab 5 Continued – Adding Op-Amps

 

7

10/7

Semester Project Description

 

Effect of Long Lead Wires

Bridge: able to support a load of about 210lb in the middle.  That means I will be standing on it.  I wear size 12W shoes and there has to be a place for me to stand comfortably

 

Constraints:

1) Bridge must be portable

2) There must be 2m of clear space between the end supports

3) Bridge cannot touch floor between the supports

4) An upright 2L Diet Coke bottle must be able to pass under the bridge anywhere in the central 1m portion of the bridge (while load is applied)

5) The bridge must support the load (me) for at least 20 seconds

6) Any materials are allowed as long as they are safe and legal (for example, no uranium/baby seal composites)

 

Grading Criteria:

Analysis      25%

Design        20%

Strength     20%

Weight       20%

Aesthetics  15%

HW #7: 

1.      Fig P3.2 (p 88).  If Rg=350Ω,  Vin=12V and ε = 500μ, find Vout

2.      If all four gauges have R=350Ω, find Vout

3.      If all four gauges have R=120Ω, find Vout

All four gauges have R=120Ω and the active gauge is mounted on an aluminum bar.  If the temperature rises 40°C and no load is applied, find Vout

 

Due:

10/9

Strain Gauge Rosettes

Strain gauge rosettes

Rosette example

 

Lab 6 Continued – Adding Op-Amps

 

8

10/14

Fall Break

 

10/16

 

Von Mises Stress

Section 3.4 and 3.5

HW #8

 

3.16, 3.17, Max Force Problem

 

Due:

 

 

 

Lab 7 – Measuring Elastic Modulus using Wave Propagation

 

 

9

10/21

Exam Review

 

10/23

Exam 1

In Class, Open Book, Open Notes

 

Sample Exam from Fall 2006:

Exam 1

Exam 1 Answer Key

 

Fall 2008 Exam Solution

 

 

 

No Lab

 

 

10

10/28

Dynamic Data Acquisition 

 

10/30

Dynamic Data

·         Aliasing

·         Filtering

·         Sample

·         Rates

·         Resolution

Low-pass filter to avoid aliasing 

 

HW #9

 

1.      If an accelerometer is recorded at a sample rate, fs, of 1000 Hz, what is the maximum frequency that could be observed?

2.      If a first order lowpass filter is to be used as anti-aliasing filter for problem 1and it has a resistor of 100kΩ, what capacitance does it need?  Set the corner frequency to the maximum possible.

3.      If you record an accelerometer with fs=2560 Hz and a sample time T=10 seconds, what is the frequency resolution?

4.      If fs=12800, what is the time resolution?

5.      Say you are recording the dynamic output from a strain gauge and you need the frequency resolution to be 0.125 Hz and the time resolution to be 0.25 sec.  What are the required sample frequency and sample time?

 

Due:

 

Lab 8 – Speed of Sound in Solid Bar, Demo and Software Install

 

11

11/4

Dynamic Data using Matlab

High Pass and Low pass Filters

Importing Data

 

 

 

11/6

Dynamic Data Using Matlab

 

Piston Slap Example 

 

 

Lab 8 Continued – Speed of Sound in Solid Bar

 

12

11/11

Review of Data Acquisition

Rotating Equipment

Ordinal Domain

 

 

 

 

 

 

11/13

Beam Bending Frequencies

 

 

 

 

Lab 9 – Measuring Beam Bending Frequencies

Notes 1

Notes 2

Notes 3

Notes 4

Notes 5

 

13

11/18

 Optical Testing

 

HW #10

1        Master grating pitch = 50 lines/in.  Find fringe spacing when rotation angle is 5°, 10° and 15°

2        Master grating pitch = 100 lines/in.  Find fringe spacing when rotation angle is 5°, 10° and 15°

3        If the master grating pitch is 50 lines/inch and the specimen pitch is 55 lines/in, what is the fringe spacing (no strain)?

4        If master and specimen gratings both have spacing = 100 lines/in and the specimen grating is strained to 1% (e = 0.01), find fringe spacing.

 

Due:

 

 

11/20

 Optical Testing Calculations

 

 

 

 

 

Lab 9 - Continued

14

11/25

 

 

 

11/27

Thanksgiving Break

 

 

 

 

Lab 10 – Plate Frequencies

 

15

12/2

Exam Review

 

 

 

12/4

Exam 2

 

 

 

 

No Lab

 

 

16

12/9

Bridge Evaluation

 

12/11

Bridge Evaluation

 

 

No Lab

 

 

Safety:

“As we begin this semester I want to take a few minutes and discuss emergency preparedness. Purdue University is a very safe campus and there is a low probability that a serious incident will occur here at Purdue. However, just as we receive a “safety briefing” each time we get on an aircraft, we want to emphasize our emergency procedures for evacuation and shelter in place incidents. Our preparedness will be critical if an unexpected event occurs.

 

Emergency preparedness is your personal responsibility. Purdue University is continuously preparing for natural disasters or human-caused incidents with the ultimate goal of maintaining a safe and secure campus. Let’s review the following procedures:

 

·         There are nearly 300 Emergency Telephones outdoors across campus and in parking garages that connect directly to the Purdue Police Department (PUPD). If you feel threatened or need help, push the button and you will be connected immediately.

 

·         If we hear a fire alarm, we will immediately suspend class, evacuate the building, and proceed outdoors, and away from the building. Do not use the elevator.

 

 

 

MET 311 EXAMINATIONS:  Two exams are scheduled for the semester.  Exams are open book, open notes and calculators are the only number crunching devices that may be used.

MET 311 HOMEWORK:    Homework problems will be assigned at most class sessions. All problems will be graded. All assigned problems must be handed in at the end of the day on which they are due and will be graded on a ten-point basis.  Homework up to one week late will have a 20% penalty (20% of the possible number of points).  Homework more than one week late will not be graded.  Homework should be turned in at the drop box in Knoy Hall by 4:30 on the day it is due.  I encourage students to work together on their homework if it helps them learn and if the work they turn in is their own.  Test questions are patterned on homework questions.  If you don’t really understand the homework solutions you’ve turned in, the tests are likely to be a problem for you.

 MET 311 POLICIES AND PRACTICES:          

ATTENDANCE: You are expected to attend in all lecture and laboratory sessions, including exam sessions. If a lab or exam absence is unavoidable, contact the instructor beforehand. Any unexcused missed lab session will result in a grade of zero for that lab. In all circumstances, you are responsible for learning the material covered during all class meetings. Safety glasses are required for all labs; bringing a thumb drive is recommended. Assuming extenuating circumstances do not apply, if you miss three lab sessions or fail to submit three reports within two weeks following their due dates, you will automatically fail the laboratory portion of the course.

REPORTS:  Lab reports are due one week after the lab session, unless otherwise specified. Lab reports will be accepted up to one week after their respective due date, with a 5 point per day late penalty. Under extenuating circumstances, late penalties may be waived.

COMMUNICATION: Course communication is primarily electronic. Students will need to have a valid School of Technology career account to access the course website and materials.  Check the course web site regularly for updates and notices.  It will be updated regularly throughout the semester to include new sample problems, test answers keys and class administrative information.  Some information will only be available during class meetings.

PARTICIPATION: You will learn more if you actively participate in all class and lab sessions, complete all assignments (reading, homework, and lab reports), and take responsibility for learning the course material. When you have questions, you need to pursue their answers.  However, if, after a reasonable amount of effort, you are still struggling, come to my office.  I can’t help if I don’t know you have a problem.

INTEGRITY and ETHICS: No student should take unfair advantage of another.  All students are assumed to be acting honorably until they show otherwise.  However, I won’t tolerate cheating in any form. 

If you are not sure whether what you are doing is cheating, ask yourself whether it would make your mother proud of you if she knew about it.  For a more formal description, refer to University Regulations, Part 5, Section III.B.2.a., regarding dishonesty.

Course Core Learning Objectives:

 

1.   Calculate principal stresses, maximum shear stress, and principal direction in a plane when given the loading condition.

2.   Select the appropriate type of strain gage(s) for a given test specimen or component.

3.   Determine the proper strain gage orientation for measurement of the strain induced by a single loading.

4.   Calculate principal strains, maximum shearing strain, and principal direction on a surface from strain gage rosette data.

5.   Convert strain values to stress values when given appropriate material information.

6.   Manipulate strain gages in a simple Wheatstone Bridge circuit configuration to isolate and measure strain from one of several loadings.

7.   Perform an open-ended experimental investigation in solid mechanics.