Recent governmental regulations have prompted development and application of exhaust aftertreatment systems to reduce particulate matter emissions from both on-highway and off-highway vehicles. Exhaust aftertreatment systems for diesel engines, for example, typically include a diesel particulate filter. Particulate filters, such as a diesel particulate filter, typically include a cylindrical shape with a honeycomb structure cross section. Generally, these honeycomb structures are formed by bringing a powder of ceramic, metal or the like together with a binder, and extruding the mixture with a honeycomb shape. This structure is then fired to fix the honeycomb shape.
Filtration occurs by passing exhaust gas through walls of the honeycomb structure while trapping particles. In some instances, these filters may then be coated with a suitable catalyst to facilitate exhaust aftertreatment of other constituents, such as by the inclusion of a diesel oxidation catalyst for oxidizing hydrocarbons and carbon monoxide to carbon dioxide gas and other more desirable compounds. It is well known that, during the production process, occasional internal defects, such as cracks and internal voids, can sometimes occur in the honeycomb structures of the particulate filters. When a crack occurs in cell walls of the particulate filter, the crack can significantly affect the durability of the particulate filter and can result in a substantial deterioration in the ability of the filter to trap particles, at least in the area of the crack, according to expectations and specifications. Visual inspections have proven an inadequate strategy for detecting internal flaws in particulate filters.
It is known to employ an ultrasound testing strategy to detect internal flaws in particulate filters. For example, in the testing strategy described in U.S. Publication No. 2007/0144260, a test apparatus may include one or more ultrasound transducers for performing either a pulse echo test or a through transmission test. In either arrangement, the test apparatus moves the one or more transducers into engagement with the particulate filter to test from a first discrete location along a surface of the particulate filter. After the test is performed, the test apparatus may reposition the one or more transducers to test from a second discrete location along the surface of the particulate filter. While this inspection method may prove successful at detecting internal flaws at the tested locations, it ultimately tests only a small volume of the particulate filter. Testing more locations across the filter surface is possible, but requires repositioning of the one or more ultrasonic transducers, which undesirably increases inspection time.
The present disclosure is directed to one or more of the problems set forth above.