EAS209 L09_Plastic Deformation-spring 11

# EAS209 L09_Plastic Deformation-spring 11 - EAS 209-Spring...

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EAS 209-Spring 2011 Instructors: Christine Human 1/18/2011 1 09-Plastic Deformation Lecture 9 Stress Concentrations / Plastic Deformation We have assumed that stress is: 1) uniformly distributed 2) less than the yield stress. Today’s Objectives: Consider stress concentrations around bolt holes and fillets Understand what happens when σ > σ Y using an ideal elastoplastic material to model behavior Today’s Homework: EAS 209-Spring 2011 Instructors: Christine Human 1/18/2011 2 09-Plastic Deformation Stress Concentrations Discontinuities of cross section, such as a hole or reduction in area, may also result in high localized or concentrated stresses Define stress concentration factor Assuming linear stress-strain relationship , K is independent of material type and size of member K is only dependent on relative geometry Values for K can be determined experimentally: max ave K

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EAS 209-Spring 2011 Instructors: Christine Human 1/18/2011 3 09-Plastic Deformation Flat bar with hole: K is a function of r/d Flat bar with fillet: K is a function of r/d and D/d EAS 209-Spring 2011 Instructors: Christine Human 1/18/2011 4 09-Plastic Deformation Example Determine the largest axial load P that can be safely supported by a flat steel bar consisting of two portions, both 10 mm thick, and respectively 40 and 60 mm wide, connected by fillets of radius r = 8 mm. Assume an allowable normal stress of 165 MPa. Solution Determine the geometric ratios and find the stress concentration factor from chart Find the allowable average normal stress using the
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EAS209 L09_Plastic Deformation-spring 11 - EAS 209-Spring...

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