Severity of the Bend and Its Effect on the Subsequent Hydroforming Process for Aluminum Alloy Tube

Tube bending and hydroforming of aluminium alloy S-rails

“…The main variable in the bending operation that affects the level of thickness change, work hardening and residual stresses within the tube is the bend severity (R/D), which is the ratio of the centre line bend radius to the outer diameter of the tube. To this effect, the level of thickness and strain changes increase with increasing bend severity, as shown by several researchers [7,12,13,15,19]. An effective way to control the thickness and strain levels within a pre-bent tube is to apply an axial boost force on the end of the tube during the bending process [14,15,17].…”

“…The distinction is that the low-pressure process induces near-zero circumferential expansion of the tube and does not utilize end-feed. The high-pressure hydroforming process induces circumferential strain and thinning within the pre-bent tube due to circumferential expansion [12,13,15,17], which may further exhaust the ductility of the tube. End-feed within the hydroforming process is generally used to control the degree of thinning within the tube and also induces axial strain.…”

“…The rotary-draw tube bending process, which is the most common bending process used in automotive structural applications, has been shown to consume most of the material ductility before any subsequent hydroforming operation [12][13][14][15][16][17]. Bending with a mandrel to support the inside of the tube is commonly employed since it reduces ovalization of the cross-section and assists in the prevention of buckles and wrinkles on the inside of the bend, which is more common for thinner gauge tube [7,[18][19][20][21].…”

Dual Phase Steel Characterization for Tube Bending and Hydroforming Applications

“…The manufacture of complex tubular components produced using hydroforming often requires pre-forming operations before hydroforming can take place [50,51]. The most common of these pre-forming operations is tube bending, in which a straight length of tube is bent in one or more locations to get its rough shape close enough to the final shape so that it can be placed in the hydroforming die.…”

“…Bending influences the properties of the tube and consequently its formability in subsequent hydroforming operations [51,57]. While strains experienced in hydroforming are mainly circumferential, tube bending strains are predominately axial.…”