Experimental and numerical study of formability in stainless steel 304 tube by hydroforming process.

In this paper, with the aim of providing a new test pattern for empirical prediction of FLD of 304 stainless steel tube, first, numerical investigation of hydro-bulging process with various load paths and die geometries has been performed on strain path and plastic instability. Study on geometry of dies has been performed by varying die corner radius (R) and bulging length (W). Here, effect of axial feeding on strain ratio (β) has been studied. In this condition, by increasing W. strain ratio (β) tends to avalue of zero, a situation that is independent of boundary condition. By increasing die corner (R) in free loading condition, reduction of p occurs and the strain path approaches to plane strain state; while in loading with axial feeding condition, increasing of R has negligible effect on strain path and ratio. In loading with axial feeding condition, increase in axial feeding strain ratio (β) is reduced drastically. From the simulated tests, number of 10 tests with distributed loading path on strain diagram was selected for empirical study. Meshed tubes are loaded controllably until tearing and the FLCs were drawn using strains obtained near tearing locations. [ABSTRACT FROM AUTHOR]