Design of Machine Elements - 1 - Mechanical Engineering (MCQ) Questions and Answers


Welcome to Design of Machine Elements - 1 multiple choice questions and answers with explanation. These objective type Design of Machine Elements - 1 questions are very important for the campus placement test, semester exams, job interviews and competitive exams like GATE, IES, PSU, UPSC, and diploma.



1)   Determine the number of coils in a helical compression spring, if modulus of rigidity is 80 Gpa and spring stiffness is 50 N/ mm. Assume wire diameter and spring index as 8 mm and 5 respectively


ANSWER: 12.8 turns



2)   Which factor is used to consider the effects of direct shear stress and torsional shear stress when curvature effect stress is not considered?


ANSWER: Shear stress concentration factor



3)   The shear stress concentration factor (Ks) in mechanical springs is given as _____


ANSWER: (1 + 0.5 / C)



4)   Which type of springs have only active coils?


ANSWER: Helical tension springs



5)   Solid length for helical compression springs having square and ground ends is given as _________.


ANSWER: (n + 2)d



6)   Which formula is used to calculate shear strength of butt weld?


ANSWER: P = τ h l



7)   If welds are designed with in-plane eccentric load, then eccentric load can be replaced by _______.


a. parallel force
b. twisting moment
c. both a. and b. 
d. none of the above


ANSWER: both a. and b.



8)   Which of the following statements is/are false?

1. Under fatigue load, casted structures are stronger than welded structures
2. Welding cannot produce complicated structures
3. Welding can join dissimilar materials
4. Rivetted joints produce lightweight constructions as compared to welded joints


a. Statement 1 and Statement 3
b. Statement 1, 2, and Statement 4
c. Statement 1, 2, and Statement 3
d. All the above statements are false


ANSWER: Statement 1, 2, and Statement 4



9)   In the diagram shown below la = lb = 100 mm, what is the load carrying capacity if weld size is 15 mm and shear stress for the weld is 100 MPa


ANSWER: 212.13 kN



10)   Axially loaded unsymmetrical welded joint is shown below, if the total length of the weld is (la + lb)  then the length of weld la is given as



ANSWER: (b / (a+b)) x l



11)   When a coupler nut is subjected to crushing stress, crushing failure can be avoided if _____


ANSWER: permissible crushing stress is more than crushing stress induced in the threads



12)   Which among the following is the condition to avoid separation of connected members?


ANSWER: Force acting on the connected members should be negative



13)   Threads used in screw fasteners are ______


a. having high strength
b. having low-efficiency
c. single start type 
d. all of the above


ANSWER: all of the above



14)   Drilling an axial hole is a method used to achieve ______


ANSWER: uniform strength



15)   What is the approximate nominal diameter for coarse threads?


ANSWER: d = 1.19 dc



16)   Which type of stress is induced in a screw body?


ANSWER: Torsional shear stress



17)   Calculate torque required to overcome thread friction if axial load of 8 kN acts on a power screw having double start square threads of 30 mm mean diameter. Friction angle and lead angle are 7o and 9o respectively.


ANSWER: 34.40 N-m



18)   The efficiency of power screw can be improved if ______


ANSWER: the sliding friction is replaced by rolling friction in the screw threads



19)   In power screws, if friction angle Φ is less than lead angle λ, then the screw undergoes _______


ANSWER: over hauling



20)   A triple start square threaded power screw has torsional shear stress and direct compressive stress of 5 N/mm2 and 7 N/mm2. Calculate maximum shear stress induced in a screw body.


ANSWER: 6.10 N/mm2


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