Flange with stress attentuation feature

A method of assembling a cooling fan housing, the method comprising:

• at least one or more of casting, machining and additively manufacturing an inner housing comprising inner forward and inner rearward flanges on either side of an inner annulus;
• at least one or more of casting, machining and additively manufacturing an outer housing comprising outer forward and outer rearward flanges on either side of an outer annulus;
• machining at least one of the inner rearward flange and the outer rearward flange to comprise a recessed portion proximate to at least one of the inner and outer annuluses, wherein the inner rearward flange and the outer rearward flange each comprise a non-recessed portion;
• attaching the outer and inner forward flanges in a first tight-fitting condition;
• and
• further attaching at least a portion of the non-recessed portion of the outer rearward flange to at least a portion of the non-recessed portion of the inner rearward flange in a second tight-fitting condition, with the recessed portion of the inner and/or outer rearward flange forming a gap with the outer and/or inner rearward flange and with an attachment location being rearward of the gap.

A cooling fan housing, comprising:

• a first housing comprising a first forward flange and a first rearward flange on either side of a first annulus;
• and
• a second housing comprising a second forward flange and a second rearward flange on either side of a second annulus,
• wherein:
• at least one of the first and the second rearward flanges comprises a recessed portion proximate to the first and second annuluses and a non-recessed portion remote from the first and second annuluses,
• the first and the second forward flanges are attachable in a first tight-fitting condition, and
• the non-recessed portion of the at least one of the first and the second rearward flanges are attachable in a second tight-fitting condition, with the recessed portion of the at least one of the first and the second rearward flanges forming a gap and with an attachment location of the non-recessed portion of the at least one of the first and the second rearward flanges being rearward of the gap.