The stress analysis of photoelastic models of pressure vessels with drumheads shaped by free explosive forming showed that discontinuities of profile of up to 34° at the drum-knuckle junction are permissible because the resulting peak knuckle stresses are lower than in vessels with equivalent torispherical drumhead.
Free explosive forming, by forcing flat plates through ring dies, produces repeatable, approximately torispherical shapes. For annealed mild steel the geometric and explosion parameters have been related to permit prediction of dish shapes. It was found that no size effect existed.
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