Uncertainty and Reliability

Question 1

What are the 6 main factors of uncertainty

Answer 1

F.I.C.M.D.L
1.Distributed nature of material properties due to non-uniform
composition or local processing
2. Load fluctuation
3. Fabrication variability in dimensions or surface quality
4. Intensity of stress concentration around a hole or shoulder
5. Corrosion and wear may have adverse effect
6. Mathematical models may be inaccurate. We can only guess
the characteristics from a part of the population of components

Question 2

How do you accommodate uncertainties

Answer 2

With a factor of safety

Question 3

What is a factor of safety and how is it determined

Answer 3

Factor of safety is means of enhancing an
engineering design to account for uncertainties in a part or system,
its applications, and its environment

The Factor of Safety value can be determined based on engineer’s
experience or by stochastic methods

Question 4

What is the eqn of the factor of safety

Answer 4

n_d =

n_d= loss of function load / allowable load and n_d > 1

Question 5

Define Reliability

Answer 5

The probability of a component working for the period of time intended
under operating conditions

Question 6

what is the eqn of reliability

Answer 6

R=(Number of successful components) / (total number of components) Where R is (0

Question 7

What is the coefficient of variation eqn

Answer 7

C_x= (Standard deviation (S_x)) / (mean(bar x))

Expressed as a %