Thermomechanically induced failures

However, to compete with and ensure the same reliability and long-term stability that traditional power systems provide, better understanding and management of the component regions susceptible to failure are required. Accordingly, this chapter is intended to elucidate the status of the current numerical modeling activities considering the thermomechanically induced stress within SOFCs. In... 

Thermomechanically induced failures are a consequence of the internal stresses which can be established because of the mismatch between the thermal expansion coefficient of the plastic ( 25x 10 per°C), and those of the die and the leadframe ( 12x 10 per°C). These stresses build up when the plastic cools down after moulding, and cyclic stresses are induced by changes in temperature during service. Until recently, the most frequently reported failure mechanism caused by the internal stresses was fracture of either the bond wires or the... 

Elastic Deformation Due to High-Intensity Localized Heating. If plastic deformation is avoided, elastic deformation may still induce material cracking and/or failure. The thermomechanical response of an opaque material to high intensity localized heating has been considered. When strain rates are insufficiently high to induce internal heating (and deformations are small), the conduction solutions of the previous section may be combined with the classical equation of elastic stresses ... 

Under field-use conditions or under accelerated thermal cycling qualification conditions, the solder joints experience cyclic thermomechanical loads due to GTE mismatch or thermal gradients among various parts of a packaging assembly and failure due to such thermomechanical loads. In addition to thermomechanical fatigue loads, the solder joints experience stresses due to mechanical loads such as vibration, shock, etc. However, such mechanically-induced failures and other chemically or electrically-induced failures are not the focus of this chapter. 

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