Tube hydroforming process: A reference guide

Deformation and fracture behaviors of AZ31B Mg alloy at elevated temperature under uniaxial compression

Damage in metal forming

Implementation of the forming limit stress diagram to obtain suitable load path in tube hydroforming considering M–K model

In micro-scaled plastic deformation or micro-forming process, workpiece usually consists of only a few grains in deformation zone. The so-called size effect thus exists and the material deformation behaviors are quite different from the conventional ones in macro-scaled. Size effect affects the deformation capability or the forming limit of sheet metals. To explore this effect, uniaxial tensile tests of different-shaped specimens were conducted to obtain the left-hand-side forming limit diagram of sheet metals from macro to micro-scaled. The deformation process was recorded by a digital camera and the limit strains of different deformation conditions were measured using the digital image correlation method. The left-hand-side forming limit diagrams under different thickness-to-grain-size ratio conditions were then constructed. The experimental results show the existence of the significant size effect and the forming limit decreases with the thickness-to-grain-size ratio. However, the scatter of forming limit gets much worse if there are only one or two grains over the thickness of material. To analyze how the size effect affects the ductile fracture in micro-forming, Oyane׳s ductile failure criterion was modified to model the forming limit in micro-scaled plastic deformation. Through calculation, the modified criterion is found to be able to model the decrease of forming limit caused by size effect. The revised Oyane criterion can then be used to analyze the forming limit of sheet metals in micro-scale.

Geometry and grain size effects on the forming limit of sheet metals in micro-scaled plastic deformation

Analytical and numerical approach to prediction of forming limit in tube hydroforming

Characterization of mechanical property of magnesium AZ31 alloy sheets for warm temperature forming

Analytical approach to bursting in tube hydroforming using diffuse plastic instability

Based on plastic instability, an analytical prediction of bursting failure on tube hydroforming processes under combined internal pressure and independent axial feeding is carried out. Bursting is an irrecoverable phenomenon due to local instability under excessive tensile stresses. In order to predict the bursting failure, three different classical necking criteria – diffuse necking criteria for a sheet, and a tube, and a local necking criterion for a sheet – are introduced. The incremental theory of plasticity for an anisotropic material is adopted and the hydroforming limit, as well as a diagram of bursting failure with respect to axial feeding and hydraulic pressure are presented. In addition, the influences of material properties such as anisotropy parameter, strain hardening exponent and strength coefficient on plastic instability and bursting pressure are investigated. As a result of the above approach, the hydroforming limit with respect to bursting failure is verified with experimental results.

A prediction of bursting failure in tube hydroforming process based on plastic instability

Analytical and numerical analysis of bursting failure prediction in tube hydroforming

Sang-Woo Kim

Papers

Analytical and numerical approach to prediction of forming limit in tube hydroforming

Characterization of mechanical property of magnesium AZ31 alloy sheets for warm temperature forming

Analytical approach to bursting in tube hydroforming using diffuse plastic instability

A prediction of bursting failure in tube hydroforming process based on plastic instability

Analytical and numerical analysis of bursting failure prediction in tube hydroforming