He registered for the draft and was found 'physically able'. Maybe you can look at this Draft Registration Card online - serial numbers etc. to find out more - although by the late date of this registration in Sept. 1918 - he may never have been inducted into service.
U S World War I Draft Registration Cards, 1917-1918
Citing this Record "United States, World War I Draft Registration Cards, 1917-1918," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/K68T-PSD
IMAGE OF DOCUMENT: https://familysearch.org/pal:/MM9.3.1/TH-1942-26303-30316-77?cc=1968530&wc=M9MT-5LT:n1684528991
Ralph Haney Burke
Residence: 11240 S. Irving, Chicago, Cook, IL
Civil Engineer Employer Sanitary District of Chicago
Draft Registration date Sept. 12, 1918
event place: Chicago City, IL
Local Board no 77, Ridgefield House, 97th and Longwood, Chicago
Male White Age Married
birth date: 22 May 1884
birthplace: , , United States
Spouse: Mrs. Edna Burke, (same address)
Physically qualified
country of citizenship: United States
nara publication title: World War I Selective Service System Draft Registration Cards
nara publication number: M1509
film number: 1503986
digital folder number: 005248309
image number: 05612