ME 342 Machine Elements I-Spring-2006-Mid 1-Solutions

ME 342 Machine Elements I-Spring-2006-Mid 1-Solutions -...

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Unformatted text preview: Department of Mechanical Engineering, Yeditepe University ME 342 MACHINE ELEMENTS I MIDTERM EXAM I, Spring 2006 NAME:__________SOLUTIONS_______________________Time: 110 Minutes Closed books and notes. Four questions on one page. Q.1 . (20%) Answer the following questions as true (T) or false (F). CIRCLES ONLY . I. Design is as art as it is science. T F II. Design involves analysis, but not synthesis. T F III. Consideration of the total life cycle is a desired product design practice. T F IV. Engineering is the discipline that tries to discover laws from a given system along with its input and output. T F V. Engineering Design is usually a recursive and iterative process. T F VI. In concurrent design all aspects of product creation, from design to manufacturing, to use, and etc., are considered simultaneously. T F VII. Professional societies are also means of technical information. T F VIII. ASME, ISO, TSE, and NASA are all standardization organizations T F IX. Customer’s expression of the need can always be taken as the definition of the problem. T F X. Uncertainty is an inherent problem in engineering design that can be dealt with by using a design factor. T F Q.2. (10%) The stresses for a machine part are determined as MPa, 10 MPa, 50 MPa, 100 = = =- = =- = zy xz xy z y x τ τ τ σ σ σ . Determine, by any method, a) the principal normal stresses and their direction vectors, and b) the maximum principal shear stress. SOLUTION: Since all the shears are zero in xyz directions, then x, y, and z axes must be the principal directions, and the associated stresses are the principal normal stresses. Therefore a) MPa 100 MPa 10 MPa 50 2 1- =- = = z σ σ σ with           =           =           = 1 , 1 , 1 3 2 1 u u u b) MPa 75 2 ) 100 ( 50 2 3 1 3 / 1 max =-- =- = = σ σ τ τ Q.3. (30%) Consider the infinitesimal stress cube taken at a point in a body under loads, on which the calculated stresses are shown in kpsi (some are not shown due to equilibrium). (some are not shown due to equilibrium)....
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ME 342 Machine Elements I-Spring-2006-Mid 1-Solutions -...

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