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SecondExam(F09)_Soln - T he H ashemiteU niversity Faculty f...

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The Hashemite University Faculty of Engineering Me c hani c al Engine e ring Departme nt Machine Design I Fall 2009 Instructor: Dr. Ala Hijazi Second Exam PartI-ClosedBook Please Read Questions Carefully - GoodLuck! (16 points) I . For the flowing statements circle the correct answer. A steel part is subjected to a fully reversed fatigue stress where the magnitude of the stress is S,, - r > S". Which of the following is true? a) The pan will fail during the first loading cycle. fS) The part will fail after a certain number ofcycles. i) The pan will have infinite life. d) The static factor of safety is larger than one. Which ofthe following failure theories cannot be used for ductile materials? a) Maximum shear stress @ Maximum normal stress -c) Distortion energy d) Coulomb-Mohr The surface finish ofa machine element affects its a) Ultimate strength b) Yield strength @ Endurance limit d) All ofthe above e) None ofthe above The value ofthe fatigue stess concentration factor (K/ is: a ) 1 Z K 7 Z 0 b ) K , : K ; z O @ r , u r r > t d) K, <K, e) None ofthe above The Von-Mises stress will be equal to zerowhen a) o,- orl0 artd o,: r,r: rn: t-:0 b) o, * 0 and or: o": tr: tr: t- = 0 c) tr l0 and o, = or= o- = tr= t^:0 @ None ofthe above e) All ofthe above Name: kz t, Student #: " -t
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A cantilever beam having a rectangular cross section as shown. A force F is to be applied at the free end. The strain energy in the beam @ will behigher if the force is applied in the direction ol tne ir axls.
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