Hoop-stress controlled shrinking for exhaust component

1. A method of assembling an exhaust component comprising:

(a) providing a substrate assembly including a substrate body and a mat wrapped around the substrate body;

(b) determining a hoop stress for the substrate assembly; and

(c) predicting a shrinking diameter for an outer shell that is to receive the substrate assembly based on the hoop stress determined in step (b).

2. The method according to claim 1 wherein step (b) further includes inserting the substrate assembly into an instrumented pipe structure and determining the hoop stress for that substrate assembly.

3. The method according to claim 2 wherein the substrate assembly comprises a first substrate assembly and including the steps of removing the first substrate assembly from the instrumented pipe, inserting a second substrate assembly into the instrumented pipe, determining a second hoop stress for the second substrate assembly, and predicting a second shrinking diameter for a second outer shell based on the second hoop stress.

4. The method according to claim 2 wherein step (b) includes measuring strain on the substrate assembly while in the instrumented pipe, and subsequently determining the hoop stress based on the measured strain.

5. The method according to claim 2 including recording hoop stresses determined in step (b).

6. The method according to claim 2 including weighing the mat before wrapping the mat around the substrate body.

7. The method according to claim 2 including

(d) removing the substrate assembly from the instrumented pipe structure and inserting the substrate assembly into an un-shrunk outer shell; and

(e) shrinking the outer shell to the shrinking diameter predicted during step (c).

8. The method according to claim 1 including inserting the substrate assembly within the outer shell subsequent to step (c) and applying the shrinking diameter predicted in step (c) to the outer shell to form a final exhaust component.

9. The method according to claim 8 wherein the final exhaust component comprises a catalytic converter.

10. The method according to claim 8 wherein a predicted shrinking diameter is to provide a desired gap bulk density value, and including the steps of performing a gap bulk density check subsequent to applying the shrinking diameter to ensure that the predicted shrinking diameter is actually providing the desired gap bulk density value.

11. The method according to claim 1 including

(d) shrinking the outer shell to the shrinking diameter predicted during step (c) in a single shrinking step to form a finished exhaust component.

12. The method according to claim 1 wherein step (b) includes measuring strain to determine hoop stress.

13. The method according to claim 1 including using predicted shrinking diameter from step (c) to provide a desired gap bulk density.

14. The method according to claim 13 including

(d) shrinking the outer shell to the shrinking diameter predicted during step (c), and

(e) performing a gap bulk density check can be performed subsequent to step (d) to ensure that the predicted shrinking diameter is actually provides the desired gap bulk density.

15. The method according to claim 1 including

(d) performing steps (b) and (c) prior to inserting the substrate assembly into an outer shell.

16. The method according to claim 15 including

(e) inserting the substrate assembly into the outer shell subsequent to predicting the predicted shrinking diameter, and

(f) shrinking the outer shell to the predicted shrinking diameter.