Accession Number : ADA019931

Title :   RFI Shielding Effectiveness of Steel Sheets with Partly Welded Seams

Descriptive Note : Final rept.

Corporate Author : CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL

Personal Author(s) : Honig, Jr, E M

PDF Url : ADA019931

Report Date : Nov 1975

Pagination or Media Count : 31

Abstract : This report presents the results of an investigation to determine the effect of six forms of incomplete welds containing slots and holes on the shielding effectiveness of shielded enclosures. The test specimens were butted plates and slotted plates (with and without tacked backing strips), wide-slot plates, and drilled plates. The plates were subjected to radio frequency interference (RFI) radiation from nominally 10 kHz to 10 GHz in frequency. Shielding effectiveness as a function of flaw size was determined for each defect class. Three critical, or transition, flaw sizes were determined for the three minimum specified shielding levels for each class of defect. Since through-thickness slots and holes are limiting, or worst, cases of cracks and porosity respectively, the critical flaw size determine the sizes of the cracks and porosity in welds that are not cost-effective to repair. Results showed that weld seams having unwelded, but tightly butted, lengths up to 4 1/2 in. (11.43 cm) afford at least 60 dB shielding effectiveness at all test frequencies. Slots of finite width seriously compromise shielding by acting as resonant radiators. Backing strips tacked (without burn-through) over welded seams have minor effect on shielding effectiveness. Holes up to 0.3 in. (0.762 cm) can be tolerated at all test frequencies since at least 60 dB shielding effectiveness is maintained.

Descriptors :   *ELECTROMAGNETIC SHIELDING, *RADIOFREQUENCY INTERFERENCE, *WELDS, CRACKS, DEFECTS(MATERIALS), HOLES(OPENINGS), POROSITY, SHEETS, STEEL

Subject Categories : Electrical and Electronic Equipment
      Couplers, Fasteners, and Joints
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE