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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,

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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

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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

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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

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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

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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

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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

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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

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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 E-mail to another group’s coordinator to proofread due 8pm Monday Final group report, single Word or OpenOffice document, due 8am Tuesday by e-mail Copy mscott@bpi.edu on all of these e-mailed files – assignment grades for each group member.mscott@bpi.edu

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