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Engineering Practicum Baltimore Polytechnic Institute M. Scott Error/Uncertainty What are two ways to calculate propagation of uncertainty in calculations?

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Presentation on theme: "Engineering Practicum Baltimore Polytechnic Institute M. Scott Error/Uncertainty What are two ways to calculate propagation of uncertainty in calculations?"— Presentation transcript:

1 Engineering Practicum Baltimore Polytechnic Institute M. Scott Error/Uncertainty What are two ways to calculate propagation of uncertainty in calculations? 1.Max/Min Calculations 2.Relative Uncertainty Equations How do you calculate the uncertainty in your calculation of Young’s Modulus using the Euler Buckling equation,

2 Engineering Practicum Baltimore Polytechnic Institute M. Scott Error/Uncertainty Uncertainty is an interval around a value such that any repetition will produce a new result that lies within that interval. Error refers to the disagreement between a measurement and the true or accepted value

3 Engineering Practicum Baltimore Polytechnic Institute M. Scott Mechanical Material Properties Testing Compression Test Failure by buckling or crushing (or shattering glass) Wood: Crush if L/d 10 Modes of Buckling

4 Engineering Practicum Baltimore Polytechnic Institute M. Scott Materials Lab and Uncertainty Objectives 1.Review materials lab objectives and analysis 2.Understand uncertainty in materials lab

5 Engineering Practicum Baltimore Polytechnic Institute M. Scott Experiment 1: Tensile Test Objective 1: Show that the tensile force required to break a rod is of the form P = kR 2 (where P is the force required to break the material in tension, k is a constant determined by the material, R is the radius of the cylindrical specimen being tested). Objective 2: Determine the tensile strength (maximum stress in tension, ultimate tensile strength) of spaghetti directly

6 Engineering Practicum Baltimore Polytechnic Institute M. Scott Experiment 2: Bending Test Objective 1: Determine Young’s Modulus for spaghetti using the bending equation Objective 2: Determine the tensile strength of spaghetti indirectly

7 Engineering Practicum Baltimore Polytechnic Institute M. Scott Experiment 3: Buckling Test Objective 1: To prove that the Euler buckling load P for a cylindrical specimen of material can be accurately expressed by the following equation: (where P is the “critical” buckling load, A is the cross-sectional area of the specimen tested, E is Young’s Modulus for the material, k is a constant that depends on how the rod is held, L is the length of the specimen, and R is the radius of the cylindrical specimen). Objective 2: To determine Young’s Modulus for spaghetti using the Euler Buckling equation

8 Engineering Practicum Baltimore Polytechnic Institute M. Scott Report Format 12 pt Times New Roman or Calibri 11 pt 1.5 spacing Mini reports combined: – Abstract – Introduction – Procedure: Tension Lab Bending Lab Buckling Lab – Results: Tension Lab Bending Lab Buckling Lab – Discussion: Tension lab Bending Lab Buckling Lab – Conclusion

9 Engineering Practicum Baltimore Polytechnic Institute M. Scott Due Dates 3 mini-labs – Each group member completes a section (3 group members, 3 sections) – due 5pm Sunday to coordinator – Combine sections into one lab report to another group’s coordinator to proofread due 8pm Monday Final group report, single Word or OpenOffice document, due 8am Tuesday by Copy on all of these ed files – assignment grades for each group


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