Albert

What you ask for goes pretty deep into physics of failure. The problem is the question what you go for. If you are going to define a new accelerated test you have to know what is going on.
- Corrosion
- Migration
- Diffusion

Depending on what you want to activate you need to adjust the parameters involved in the process you want to accelerate. But be aware that the acceleration factors are to be determined. Thus, the more parameters the more work. 

In my experience temperature is the real driving force in constant climate. Humidity has a certain on / off characteristic. this means if you have no humidity you have no humidity related effects. If you have humidity you have the effect. With rising humidity the effect gets stronger but the initial increase in influence of the humidity is far stronger than lets say between 60% or 80%.
 I would suggest that you keep your humidity at 80% ( or 85% ) and test your product at 3 or more different temperatures monitoring the parameters you are interested in. Since the effects that occur are chemical or electrochemical  processes that are thermal activated you can find an acceleration factor with the Arrhenius law. Note, this is an estimate. Any extrapolation from a short test time to a long service time has a good deal of uncertainty (like if you want to get an estimate out of one week on the behaviour of a specimen in service). Take the results in orders of magnitude.
I know this sounds academic. But you see, many people come and ask us about accelerated testing not caring what the problem is. Usually I suggest, instead to start an expensive accelerated test without knowledge of the processes that happen, to attach the specimen with a rope to my car and drive some kilometres on the highway. The meaning of the result will be the same its both a waste of time and money.


Have a great day

Guenter 

Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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