The following links are from Dan Hudson, Michigan State University Extension.
Table 1-29. Estimated Risks to Grain Corn Yield and Quality From
Late-Season Frost Damage
Guidelines for Handling Corn Damaged by Frost Prior to Grain Maturity
Potential Yield Losses in Corn From Fall Frost Damage
Assessing Frost Damage in Soybeans
Ontario perspective on soybeans damaged by frost