Top 47 Machine Design Interview Questions You Must Prepare 19.May.2024

An increase in the speed of the outer wheel.

The factors effecting notch sensitivity are:

  1. Material
  2. Notch radius
  3. Size of component
  4. Type of loading
  5. Grain Structure

While selecting a material for a machine element, the following factors are to be considered

  1. Required material properties
  2. Manufacturing ease
  3. Material availability
  4. Cost

Factors affecting endurance strength are

  1. Load ii. Surface finish
  2. Size
  3. Temperature
  4. Impact
  5. Reliability

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, then

Actual endurance strength = Theoretical endurance limit x K

The different the modes of fractures are:

  1. Mode I (Opening mode) – Displacement is normal to crack surface.
  2. Mode II (Sliding mode) – Displacement is in the plane of the plate.
  3. Mode III (Tearing mode) – Out of plane shear.

It is the property of the material enabling it to be drawn into wire, with the application of tensile force. It must be both strong and plastic. It is usually measured in terms of percentage elongation and reduction in area, (e.g.) Ni, Al, and Cu.

Endurance limit or fatigue limit is the maximum stress that a member can with stand for an infinite number of load applications without failure when subjected to completely reversed loading.

Repeated stress refers to a stress varying from zero to a maximum value of same nature.

Reversed stress of cyclic stress varies from one value of tension to the same value of compression.

Types of variable stresses are:

  1. Completely reversed or cyclic stresses
  2. Fluctuating stresses
  3. Repeated stresses

Uniform wear condition is assumed because it leads to safer design.

The profiles used for splines in machine elements are straight sided splines, triangular splines and in volute splines.

In brittle fracture, crack growth is up to a small depth of the material.

In ductile fracture large amount of plastic deformation is present to a higher depth.

Computer is able to store lot of information and same can be retrieved fast.

It performs calculations very fast. The design can be visualized on screen and any alterations made and its effects clearly seen. Thus optimum designs can be achieved much faster and these are thoroughly tested from all angles.

When length of the member is increased, the member may fail due to buckling even though the member is symmetrical in all respects and the load is concentric.

If the time of load application is less than one third of the lowest natural period of vibration of the part, it is called an impact load.

Some of the methods are:

  1. Avoiding sharp corners.
  2. Providing fillets.
  3. Use of multiple holes instead of single hole
  4. Undercutting the shoulder parts.

The factors involved in arriving at factor of safety are:

  1. Material properties
  2. Nature of loads
  3. Presence of localized stresses
  4. Mode of failures

The failure theories are:

  1. Maximum principal stress theory.
  2. Maximum shear stress theory.
  3. Maximum principal strain theory.

The various phases of design process are:

  1. Recognition of need.
  2. Definition of problem
  3. Synthesis
  4. Analysis and optimization
  5. Evaluation
  6. Presentation

Stress concentration is the increase in local stresses at points of rapid change in cross section or discontinuities.

Stress concentration factor is the ratio of maximum stress at critical section to the nominal stress.

To prevent relative axial movement between the shaft and the bearing.

Notch sensitivity (q) is the degree to which the theoretical effect of stress concentration is actually reached.

The relation is, Kf = 1 + q (Kt-1)

Endurance limit is the maximum value of completely reversed stress that the standard specimen can sustain an infinite number (106) of cycles without failure.

Allowance in limits and fits refers to maximum clearance between shaft and hole.

When a material is subjected to repeated stress, it fails at stresses below the yield point stress; such type of failure of the material is called fatigue.

To vary the torque at the road vehicles.

It is the property of the material, which refers to a relative ease with which a material can be cut. It is measured in a number of ways such as comparing the tool life for cutting different material.

A crack can propagate if the energy release rate of crack is greater than crack resistance.

In Hazop (Hazards and operatibility) study each and every conceivable process deviation from normal operating condition of a system having identical design intention, is thoroughly analysed for causes and consequence and required action plan to mitigate hazard/operability problems are suggested on the basis of available protective system.

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.

Pipe threads are used for pressure tight joints and square threads for power trmission.

In curved beam the neutral axis does not coincide with the centroidal axis.

They are used to solve the problems of variable stresses.

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

Factor of safety = Maximum stress /Working stress

Different loads on machine components are:

  1. Steady load.
  2. Variable load.
  3. Shock load
  4. Impact load.

The two types of fracture are

  1. Ductile fracture
  2. Brittle fracture

A plane which has no shear stress is called principle plane the corresponding stress is called principle stress.