1,721,001 research outputs found
Experimental springback evaluation in hydromechanical deepdrawing (HDD) of large products
No full textSpringback is a really troublesome effect in
sheet metal forming processes. In fact changes in geometry
after springback are a big and costly problem in the automotive
industry. In this paper the authors want to analyse
the springback phenomenon experimentally in sheet metal
hydroforming. Compared with conventional deep drawing,
sheet hydroforming technology has many remarkable
advantages, such as a higher drawing ratio, better surface
quality, less springback, better dimensional freezing and
capability to manufacture complicated shapes. The
springback phenomenon has been extensively analysed in
deep drawing processes but there are not many works in the
literature about springback in sheet metal hydroforming. In
order to study it, the authors have performed an accurate
measuring phase on the chosen test cases through a coordinate
measuring machine and the obtained measurements
have been utilised for the determination of springback
parameters, taking into account the method proposed by
Makinouchi et al. The authors have focused their attention
on the possibility of adopting a modified Makinouchi et al.
approach in order to measure the springback of the large
size considered test cases. Through the implemented
methodology it has been possible to calculate the values of
the springback parameters. The obtained results correspond
to the observed experimental deformations. Analysing the
springback parameter values of the different combinations
investigated experimentally, the authors have also studied
the pre-bulging influence on the springback amount
Multi Shape Sheet Hydroforming Tooling design
No full textIn order to value the process of variables influence in sheet metal hydroforming, a special
hydroforming cell has been developed. Generally, sheet hydroforming is obtained using appropriate
press tooling. This option requires large investments completely dedicated to this technology of
production. As an alternative, conventional hydraulic presses can be used for sheet hydroforming in
combination with special hydraulic tooling named “hydroforming cells”. A special “hydroforming
cell” concept has been developed to perform experimental analysis for different shapes using the
same tooling set up. CAE tools had a strategic role just to develop the best layout and to find the
optimum solutions for the process variables. FEA has been used to define the distribution of the
blank holder variable forces: a solution which implies the use of twelve independent actuators have
been implemented. The position and the load path of each one of them has been chosen for each
formed shape, in accordance with the FEA results. Customized actuators have been used to solve
interferences between mechanical parts of the hydroforming cell. For this specific aspects the
virtual 3D design was necessary for the appropriate decisions. The developed process system is
very effective so that is possible to set up experimental campaigns for sheet hydroformed
components
Virtual Try Out and Process Optimization for an Innovative Konic Poles Production Concept
Full text linkDearborn (MI - USA
Process Performances Evaluation Using a Specific Shape Factor in the Case of Sheet Hydroforming
No full textThe increasing application of numerical simulation in metal forming field has helped
engineers to solve problems one after another to manufacture a qualified formed product reducing
the time required. Accurate simulation results are fundamental for the tooling and the product
designs. Many factors can influence the final simulation result like for example a suitable yield
criterion [1]. The wide application of numerical simulation is encouraging the development of
highly accurate simulation procedures to meet industrial requirements. Currently, industrial goals of
the forming simulation can be summarized in three main groups [2]: time reduction, costs reduction,
increase of product quality. Many studies have been carried out about: materials, yield criteria [3, 4,
5] and plastic deformation [6, 7, 8], process parameters [9, 10, 11] and their optimization, geometry
modification of the stamped part to evaluate if process responses modifications are required,
reaching the goal to perform a virtual tryout of the whole deformation process [12]. In this paper
proper metal forming numerical model and experimental analysis have been developed in order to
foresee process responses in the case of sheet hydroforming technology. The interactions among the
process performances and its variables are the most interesting aspects of the research because their
knowledge means the possibility to drive the process feasibility which can be represented by the
absence of ruptures and/or wrinkles in the stamped component. This paper analyzes the sheet
thickness variation during the hydroforming process, according to a specifically defined “shape
ratio”, useful to characterize product’s geometry. The latter is an hydroformed product characterized
by a rectangular characteristic section with a drawing depth of 150mm, obtained by a hydroforming
operation on a blank having a hexagonal shape. The physical and numerical experimentations were
carried out on multiple geometries, different each others in punch radius and die radius, and on
multiple materials, steel FeP04 (with a thickness of 1mm and 0,7mm) and Aluminum Al6061 (with
a thickness of 0,7mm). The numerical simulation, validated by the experimental investigations
[13,14], allowed to define a relationship, specific for sheet metal hydroforming, between the defined
shape ratio and the key performance indicator, that is the percentage reduction thickness measured
on specific areas of the formed part. The development of numerical models with an high level
accuracy could give the real possibility to evaluate process feasibility with different combinations of
geometrical and materials parameters without, at the first glance, simulation but only analyzing the
specific curves (y = percentage reduction thickness, x = shape ratio
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