• Fatigue i
• Adrenal Fatigue - The Stress Factor
• Anti Fatigue - Fatigue Reducing Systems
• Causes Of Fatigue - The Stress Agents
• Chronic Fatigue Relief - Respite From The Weariness
• Chronic Fatigue Syndrome - Unexplained Stress
• Compassion Fatigue: Is Fatigue Possible Out Of Compassion?
• Fatigue Mats - Your Stress Busters:
• Fatigue Matting: Learn All You Want To About Fatigue Matting
• Fatigue-the Loss Of Vitality:
• Metal Fatigue:
• Muscle Fatigue - Reduced Contraction Capacity Of The Muscles
• Stop Constant Fatigue:
• Thermal Cycling Fatigue

Thermal Cycling Fatigue

Thermal Cycling Fatigue is a testing of coatings. Under a recent STTR program by the Advanced Ceramics and Glasses group a rig was built to test the adhesion of coatings under thermal cycling fatigue conditions from 1135 °C to room temperature. It was noticed that quench rates can be controlled using cold air passing through a vortex tube and the samples were photographed every cycle. Thermal barrier coatings were being subjected to a cooling rate of 10°C per second.

The purpose of this study was to develop a method to predict the low-cycle (large strain - from 0.1 to 0.35 strains) fatigue life of solders subject to thermal cycling. Solders are commonly used in electronic assemblies and electronic units. Using thermal fatigue data measured, a low-cycle fatigue curve solder subject to the thermal cycling was developed. Specifically a Coffin-Manson relationship was derived for the solder, with a high degree of correlation for different failure criteria. This relationship, together with calculated strains in the solder joint, allows the low-cycle fatigue life of the solder joint can very well be predicted.

The development of a low cycle thermal fatigue curve poses a number of experimental challenges and confusions. Failure of a solder joint subjected to thermal cycling fatigue can take several months. For some materials, accelerated testing has been used to develop such curves. Accelerated testing involves high cycle and isothermal mechanical loading and thermal cycling fatigue. However, it was decided not to use these tests in this study because the validity of this technique is uncertain. There are insufficient data available to be able to relate accelerated test behavior with low thermal cycling fatigue behavior. This study will go half way to addressing this lack of data.

The mechanisms for mechanical fatigue (which would be observed in accelerated tests) can be quite different from those meant for thermal fatigue. Such differences have been seen in accelerated fatigue tests for tin/ lead solders. In addition to this, for a statistically robust fatigue life curve for a number of data points at each of several different strain levels is needed. Thus, development of such a fatigue life curve has the potential to be a very lengthy and rigorous process.

This study will ensure that a thermal cycling plant can complete its initial operating life of 40 years. The study will be continued as scheduled so that the thermal cycling fatigue effects on the reactor pressure vessel and associated components can be determined. It is also important to assess more precisely the extent that the related Technical Specifications impact current and future plant operations.