Fracture-based transient thermo-mechanical analysis of reciprocating engine thermal barrier coatings

Koutsakis, G.; Begley, Matthew R.; Hutchinson, John W.; Ghandhi, J. B.

doi:10.1016/j.engfracmech.2022.108568

Cited by 8 publications

(6 citation statements)

References 31 publications

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“…For all of the conditions tested, the maximum energy release rate was found to occur on the cycle that had the highest surface temperature (other criteria tested included cycles with the highest heat flux, highest temperature difference between combustion and oil surface, and highest interface temperature). Additionally, previous results indicated 51 that the peak energy release rate was found to occur later in the cycle than the peak surface temperature. Delamination was often located within the coating as compared to at the coating-substrate interface where there was a mismatch in coefficient of thermal expansion, or at the coating surface where the stress was maximum.…”

Section: Computational Approachmentioning

confidence: 84%

“…where U whole , U bottom , and U top are the strain energy of the intact multilayer, piston substrate, and debonded coating, respectively. The general methodology to calculate the energy release rate and the the equations that estimate each strain energy, which are involved and can not be easily summarized, are given in Koutsakis et al 51,52 The hypothesis is that the crack will advance when G exceeds a threshold that depends only on thermomechanical material properties. This critical parameter is the toughness G c of the material or the interface -it is an experimental measurement, not a calculated parameter.…”

Section: Multilayer Mechanics Analysismentioning

confidence: 99%

“…The durability analysis is the last step before the optimizer decides whether or not this solution is feasible. The mechanics model described earlier 51 is called separately because it is too computationally expensive to run at every time step. For all of the conditions tested, the maximum energy release rate was found to occur on the cycle that had the highest surface temperature (other criteria tested included cycles with the highest heat flux, highest temperature difference between combustion and oil surface, and highest interface temperature).…”

Section: Computational Approachmentioning

confidence: 99%

Section: Uncoupled Thermo-mechanical Analysismentioning

confidence: 99%

“…This study employs a methodology to evaluate coatings' durability due to thermomechanical loading. A brief overview of the durability mechanics technique is given below and further details can be found in Koutsakis et al 51,52 This coating delamination framework was employed to predict the delamination of several thermal-barrier-coated pistons that had been tested in a high-output, single-cylinder diesel engine. 53 The onengine coating durability observations and model results were consistent, verifying this methodology.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of thermal barrier coating performance and durability over a drive cycle

Koutsakis

Ghandhi

2022

International Journal of Engine Research

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A methodology to thermo-mechanically optimize a piston thermal barrier coating over a full drive cycle was established. The optimization objective was to minimize the heat transfer to the engine wall while maintaining structural integrity of the coating. Over 800 candidate materials were investigated and the optimization required more than one million non-road transient drive cycle calculations; real materials were investigated to ensure a realizable result and the existence of thermal and mechanical properties. High computational efficiency was achieved using a recently developed analytical heat transfer technique for multilayer engine walls. An uncoupled approach was utilized for the optimization, wherein the gas temperature and heat transfer coefficient profiles from a fully coupled and calibrated baseline model over the 20-min drive cycle were employed. The coating/piston interface temperature was constrained to be below the maximum piston service temperature limit. The durability was assessed using a recently developed analytical coating delamination framework for engine in-cylinder coatings based on the energy release rate when a crack forms. Results are presented for a mechanically unconstrained optimization and for cases constrained to three fixed levels of drive-cycle maximum energy release rate, and also constrained by the individual material’s toughness. The best-performing coating materials identified were verified using the fully coupled system-level model, which compared well to the uncoupled predictions. A study on the effect of adding a sealing layer to some high-performing, but porous, coatings showed a reduction in fuel consumption benefit and an increased exhaust temperature over the cycle, but the system still outperformed the uncoated case. The results of the study elucidate the importance of including engine performance and mechanical failure considerations in thermal barrier coating design.

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Section: Computational Approachmentioning

confidence: 84%

Section: Multilayer Mechanics Analysismentioning

confidence: 99%

Section: Computational Approachmentioning

confidence: 99%