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mechanical engineer

12 Jul

Lab#4:  Mechanical Properties of Materials in Tension

Directions: Be a detective and deduce the type of material of each specimen!

Measure the geometry and masses of 3 tensile samples.   Perform tensile tests on the samples and collect force (N) vs. displacement (mm) data and convert it to engineering stress (MPa) vs. strain plots.  Determine the mechanical properties of each sample and compare your results to theoretical values using VMSE, Appendix H, and literature/web resources (e.g. www.matweb.com, www.azom.com).

 

Sample Geometry:

sample Reduced area length (L0, cm) w (cm) t (cm) x-sect.

Area (A0, m2)

Approx.

total volume

Mass (g) &

Weight (N)

Density ρ (g/cm3 or kg/m3) Notes on appearance
1                
2                
3                

 

Stress-strain Properties:  From the plots, determine properties of each sample in the tables below.

sample E (GPa) σy (0.002 offset, MPa) εy σuts

(MPa)

σf

(MPa)

εf Strength/weight ratio Notes during test/fracture
1                
2                
3                

 


 

Questions:

  • Which material was the most stiff? Which was the most flexible?

 

 

 

  • Compare the samples in order from highest to lowest values obtained for: σy, σuts, and strength-to-weight-ratio (σuts/ρ) for each of the 3 samples. Give an example of when each of these of the different strength properties (σy, σuts, and strength-to-weight-ratio ) might be preferred.

 

 

 

 

 

 

 

  • Based on the stress-strain curve, which material is most ductile? Which is most brittle?

 

 

 

 

  • Describe the fracture surface and fracture behavior of each material and what this conveys about the material (necking? shape/angle of fracture?).

 

 

  • Compare the mechanical and physical properties to literature and deduce the material (for additional points, name the alloy or specific grade for the metals). YOU MUST JUSTIFY YOUR RESPONSE!!!!  (i.e. what properties matched with literature and led you to your conclusion)

 

 

 

 

 

***Bonus: Comment on any major sources of error or uncertainty in this exercise. Be specific about how the results will be affected by any uncertainty.

 
 

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