| Popis: |
Since a high porosity is needed to maintain a low backpressure with a diesel particulate filter, mechanical strength becomes critical in DPF honeycomb structures. In our mechanical tests, we have observed a quasi-ductilestress-strain behavior of the cellular refiactories used in exhaust gas aftertreatment. In particular, in 3X3-cell cross-section bend bars used for estimating the axial strength, we find a saw-tooth-type behavior. Associated with this behavior are monotonic decreases in bar stiffness with increasing load, as determined by repeatedly interrupting bar loading and measuring the small decreases in beam resonant frequency. Results are interpreted as the stopping of ridge-borne cracks when the greater crack-front length when the perpendicular wall is reached. This interpretation allows an improvement in a calibration factor for estimating overall honeycomb strength from bend testing of such small bars. |
