IV. Reliability Modeling and Prediction
A. Reliability Modeling
3. Physics of failure models (Apply)
Identify various failure mechanisms (e.g., fracture, corrosion, memory corruption) and select appropriate theoretical models (e.g., Arrhenius, S-N curve) to assess their impact.
Models of stress induced failures take many forms. Each failure mechanisms may have a unique model, which details the relationship between the environmental stresses on a specific structure, material, or combination.
Additional References
Quick Quiz
1-40. The linking of exact relationships between variables is a characteristic of which mathematical model?
(A) deterministic process
(B) stochastic process
(C) random process
(D) predictive link
(A) deterministic process
Algorithms, models, procedures, processes, etc. having only one outcome for a given set of inputs are said to be deterministic because their outcome is predetermined.
In probability theory, a stochastic process, or often random process, is a collection of random variables representing the evolution of some system of random values over time. This is the probabilistic counterpart to a deterministic process (or deterministic system).
Predictive link is not a common phrase and may refer to regression analysis or other stochastic relationship.
1-84. Identity all the valid statements about the Arrhenius model.
I. It is useful for all accelerated testing plans.
II. It does not rely on temperature.
III. It is useful for significant thermal stresses.
IV. It provides a relationship of failure to temperature.
(A) I and II only
(B) I and III only
(C) III and IV only
(D) I, III, and IV only
(C) III and IV only
The Arrhenius rate equation and model describes the chemical rate of reaction, and has been used to empirically fit data on occasion independent of understanding the underlying chemical reaction. The primary use of the Arrhenius model it to relate time to failure to temperature and is useful for “significant” thermal stresses which is true if the temperature is not beyond a phase transition for the material involved.
1-107. The time-to-failure distribution to represent a particular reliability situation should be primarily based upon which of the following?
(A) ease of use
(B) convenience
(C) empirical evidence
(D) a representation of the failure mechanism
(D) a representation of the failure mechanism
Understanding and describing the failure mechanisms behavior over time with a distribution permits an accurate model for decision making, test planning, and analysis. When detailed failure mechanism data is not available you may resort to empirical modeling, with the assumption that each failure in the analysis is from the same failure mechanism.
Ease of use and convenience are important considerations and should not overrule the use of the appropriate model to describe the failure mechanism time to failure behavior.
Leave a Reply