Honeycomb substrates are widely used to reduce harmful emissions from gasoline engines and are exposed to numerous thermal shocks during their lifetime making thermal shock resistance one of the key factors in designing honeycomb substrates. More stringent emission regulations will require the honeycomb substrates to be lighter in weight to improve light-off performance and to have better thermal shock resistance than conventional honeycomb substrates to handle higher expected temperature gradients.
Thermal shock resistance is generally evaluated on a substrate by evaluating the thermal strain caused by temperature gradients inside the substrate during durability testing [1,2]. During the test, a heated substrate is cooled at a surface face to generate temperature gradients while the temperature inside the honeycomb substrate is monitored by multiple thermocouples. Next generation lighter weight substrates have equal or lower thermal capacity than the installed thermocouples causing the measurement to show a slower temperature change than the actual substrate and would, therefore, misrepresent the thermal shock resistance.
This paper describes a new evaluation method for thermal shock resistance of honeycomb substrates. It uses a newly developed analysis method which can eliminate the delay in measurement response by thermocouples. The method consists of experimenting with a thermal imaging camera and thermocouples and data analysis, taking into account the heat capacity and thermal conduction of honeycomb substrates and thermocouples. This method enables the calculation of the rapid thermal behavior of lighter weight substrates.