tensile tests description

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TENSILE TESTING

ME556 Lab Experiment

Lab Report Due Tuesday October 9

Goal: To measure Young’s modulus and Poisson’s ratio using strain gages mounted on seven differentspecimens:

- 6061-T6 aluminum alloy- 4340 steel alloy- IM7/5260* composite with a [0]8 stacking sequence

- IM7/5260 composite with a [90]16 stacking sequence- IM7/5260 composite with a [±45]4s stacking sequence- IM7/5260 composite with a [0/ ±45/0]2s stacking sequence- IM7/5260 composite with a [90/ ±45/90]2s stacking sequence

Procedure:

(1) Watch the “Tensile Test Lab” video. Loads are applied to various tensile test specimens using aModel 8551 Instron test frame. A Vishay Model P3500 strain gage amplifier and SB-10 Switch andBalance are used to monitor four strain gages mounted to each specimen. The video begins with a

general discussion of this equipment, and also describes the specific steps used to perform the testsinvolved in this lab.

(2) Download BOTH of the following Excel files from the website:(a) Empty_Data_Sheet.xls(b) Official_Data.xls

Note: the cross-section dimensions of the specimen to be tested are included in these Excel files.

(3) Perform the tensile tests; enter the data you collect in the Empty_Data_Sheet.xls file.

(4) Determine Young’s Modulus and Poisson’s ratio for each specimen using the data contained in the

Official_Data.xls file and the Data Reduction Procedure described on the following page. (Note: the“official” data is used to simplify grading. Your data should return nearly identical results, however.)

(5) Submit lab report by 5PM on Tuesday October 9:

- If submitted as hardcopy, deliver directly to M. Tuttle or to ME Receptionist, Wanwisa Kisaling- If e-mailed, send as a single pdf file to: [email protected]

*

IM7/5260 refers to a composite material system produced using the 5260 bismaleimide resin reinforced with continuousIM7 graphite fibers (note: bismaleimide is often abbreviated “BMI”)



Data Reduction Procedures

1) Use Excel to calculate:

(a) the axial tensile stress (σ ) that corresponds to each load level(b) the average axial and transverse strains recorded at each load level

2) Assume the average axial and transverse strains (εa and εt, respectively) are linearly related to axial

stress σ according to the general form:

σ = ma(εa) + ba

σ = mt(εt) + bt

Use Excel to perform a linear regression analysis to determine the slopes (ma and mt) and intercepts (ba

and bt) relating axial stress to the average axial and transverse strains. There are several ways of performing linear regression using Excel. One way is to:

- determine slopes using the command: = slope(known y’s, known x’s)- determine intercepts using the command: = intercept(known y’s, known x’s)

It is suggested that you confirm that the slopes and intercepts determined using Excel are identical tothose calculated using Eq 20.33 in the Shukla and Dally textbook. Enter the slope and intercept valueson the attached data sheet.

[Note: If the experiments were "perfect," the intercepts would equal zero in all cases, i.e., the

linear fit to the measured data would indicate that strain is zero if stress is zero. The experimentswill (of course!) be imperfect, and hence it is unlikely that the intercepts will equal precisely zero

for any test. Nevertheless, the magnitude of the intercepts should be "small" (…are they “small”?...)

and will be ignored during subsequent data reduction.]

3) For each specimen,

Young’s modulus = σ / εa

Poisson’s ratio = -1*(εt / εa)Calculate Young’s modulus and Poisson’s ratio using the slopes determined for each specimen and enterin the “Measured elastic properties” table shown on the following page. Be sure to report your valuesusing the units indicated in the table. Also report results using SI units, as indicated.

Lab Report

Submit a brief lab report, containing:- basic description of the test set-up and equipment- plots of stress vs strain for each specimen (be sure to label axes and include units)- the (completed) tables- any discussion of the lab experiment or results that you deem appropriate



ME 556 TENSILE TEST LAB EXPERIMENT

Table 1. Results from linear regression:

SpecimenDescription

StrainComponent

Slope, m

(psi/ µin/in)

Intercept, b(psi)

IM7 [0]8 axial

transverse

IM7 [90]16 axial

transverse

IM7 [±45]4s

axial

transverse

IM7 [0/ ±45/0]2s axial

transverse

IM7[90/ ±45/90]2s

axial

transverse

Aluminum6061-T6

axial

transverse

Steel 4340axial

transverse

Table 2. Measured elastic properties

Specimen DescriptionYoung’s modulus Poisson’s

ratioMsi GPa

IM7 [0]8

IM7 [90]16

IM7 [±45]4s

IM7 [0/ ±45/0]2s

IM7 [90/ ±45/90]2s

Aluminum 6061-T6

Steel 4340

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