**Machine Design Basic | Interview Question and Answers**

**Machine Design Basic – Interview ,viva , Objective Question and Answers **

**1. Define design.**

Design is a process of activities to gather all the information necessary to realize the designer’s idea as real product.

**2. What are the various phases of design process?**

(i) Recognition of need

(ii) Definition of problem

(iii) Synthesis

(iv) Analysis and optimization

(v) Evaluation

(vi) Presentation

**3. List some factors that influence machine design.**

(i) Strength and stiffness

(ii) Surface finish and tolerance

(iii) Manufacturability

(iv) Economic and aesthetics

(v) Working atmosphere

(vi) Safety and reliability cost

**4. Define optimization?**

Optimization is the process of maximizing a desired quantity or minimizing the unwanted one.

**Read more ; Optimization Project List For Mechanical Students**

**5. What are the various optimization methods available?**

(i) Optimization by evaluation

(ii) Optimization by intuition

(iii) Optimization by trial& error

(iv) Optimization by numerical algorithm

**6. Describe material properties hardness, stiffness and resilience.**

- Hardness is the ability of material to resist scratching and indentation Stiffness is the ability of material to resist deformation under loading.
- Resilience is the ability of material to resist absorb energy and to resist shock and impact load.

**7. What is an impact load? Give examples.**

If the time load application is less than one third of the lowest national period of vibration of the part, the load is called an impact load. Example: Punching presses, hammers, loads exerted on cams during the motion due to eccentricity, loads imposed on gear teeth due to irregular tooth profile.

**Read more : Types Of Loads Used in Engineering Field**

**8. Define principal plane and principal stresses?**

A plane where only normal stresses act, with no shear stress acting is called principal plane. The (normal) stress acting on this plane is called principal stresses.

**9. Define factor of safety?**

The ratio between maximum stresses to working stress is known as factor of safety.

Factor of safety= Maximum stress/ working stress

**Read More : Factor Of Safety Used in Machine Design | Significance | Importance**

**10. What are the factors to be considered in the selection of material for a machine element?**

a. Required material properties

b. Manufacturing ease

c. Material availability

d. Cost

**11. Why normal stress theory is not suitable for ductile materials?**

Ductile materials mostly fail by shearing. But this theory considers only tensile or compressive stresses. So this is not suitable for ductile materials.

**12. State the various methods of finding stresses concentration factors?**

a. Photo elasticity method

b. Grid method

c. Brittle coating method

d. Strain gauge method

e. Finite element techniques

**13. Give some methods of reducing stress concentration?**

a. Avoiding sharp corners

b. Providing fillets

c. Use of multiple holes instead of single holes.

**14. What are the factors that affect notch sensitivity?**

a. Materials

b. Notch radius

c. Size of component

d. Type of loading

e. Grain Structure

**15. What are the types of variable stresses?**

a. Completely reverse or cyclic stresses

b. Fluctuating stresses

c. Repeated stresses

d. Alternating stresses

**16. What are the various theories of failure?**

a. Maximum principal stress theory

b. Maximum shear stress theory

c. Maximum principal strain theory

d. Maximum strain energy theory

**17. Explain size factor in endurance strength?**

Size factor is used to consider the effect of the size on endurance strength. A large size object will have more defects compared to a small one. So endurance strength is reduced.

If K is the size factor,

Actual endurance strength = theoretical endurance limit x K

**18. What are the methods used to improve fatigue strength?**

(i) Cold working like short peening, burnishing

(ii) Heat treatments like induction hardening

(iii) Pre stressing

**19. What is an S-N curve?**

An S-N curve has fatigue stress on Y- axis and number of loading cycles in X- axis. It is used to find the fatigue stress value corresponding to a given number of cycles.

**20 What is low and high cycle fatigue?**

Fatigue within 10 ^3 cycles is known as low cycle fatigue. Fatigue at high number cycles is called high cycle fatigue.

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