ICT2014 Abstracts

The integration of thermoelectric generators in automobile for conversion of exhaust heat energy to electric energy represents a promising solution in the reduction of fuel consumption and CO2 emission. In this context many studies were made over the past few years to improve the efficiency of thermoelectric modules (TEM) for high temperatures ranges. One crucial aspect which is commonly underestimated is the mechanical reliability of these TEM. In this work we have analyzed the reliability of a high temperature TEM made of skutterudite legs, which are connected to conductor bars using silver sintering process. The work focuses on material characterization and stochastic analysis to assess the reliability of TEM.

For high temperature applications the failure of TEM results majorly from the disruption of solder joints or brittle fracture of thermoelectric legs. Thus, in this work both mechanisms were considered and corresponding experiments were performed to characterize the involved materials. For the skutterudite p and n type material, strength at room temperature (RT) and 500°C as well as cyclic fatigue resistance at RT were determined using ring-on-ring bending method. The sintered silver was analyzed at temperatures up to 500°C using tensile, creep, and thermo-cycling tests. From the experiments the deformation behavior of materials were identified and adequate constitutive models were chosen for the finite element analysis (FEA). For lifetime prediction we used the coffin-Manson model based on inelastic strain energy for disruption of solder joint and the critical stress intensity factor for the fracture of skutterudite legs. By this approach we were able to perform a reliability analysis which allows us to compute the lifetime of TEM for harsh automotive thermal environment. This procedure can easily be applied on other TEM designs as well.