1,720,987 research outputs found
CAE tools as valid opportunity to improve quality control systems performances for sheet metal formed components
No full textNumerical Modeling of Ductile Plastic Damage in Tensile Test
No full textMaterial behaviour description frequently used in commercial codes may not be adequate
to simulate real forming processes. One of the reasons is the fact that they rarely include the
modeling of internal damage of material. This is a decisive feature in order to be able to predict
defective parts in processes like forging or to describe processes in which fracture is a part of the
process itself as in sheet blanking or metal cutting. In large deformation of metals, when plastic
deformation reaches a threshold level, which may depend on the loading, the fatigue limit and the
ultimate stress, a ductile damage process may occur concomitantly with the plastic deformation due
to the nucleation, growth and coalescence of micro-voids. Although damage and plastic deformation
are two distinct dissipative processes, they influence each other. In this paper a numerical
benchmark of the uniaxial tensile tests, for aluminium alloy, has been performed using LS-Dyna and
Deform 2D without damage. Then, a numerical uniaxial tensile tests has been studied using a
coupled model of elasto-plasticity and ductile damage implemented in LS-Dyna. Experimental
material property present in literature has been used
Development of a non conventional bulging test through numerical simulation
No full textThe metal stamping is a forming process by plastic deformation of a metal surface carried by a punch in a die. During the process different deformation modes are possible. Thus, formability, the proneness of the material to be subjected to this kind of operation, it is very important for the process feasibility. If the blank is restrained between the die and the blank-holder, the metal stamping is said by stretching. In this case, the deformation status is of pure stretching. The Erichsen test is usually adopted to verify the material formability in this deformation conditions. In this test, the blank deformation is obtained thanks to a spherical punch. The friction in the contact of the sheet metal and the punch has influence in the deformations distribution. An alternative testing procedure for stretching conditions it is represented by the conventional bulging test. In this case, the deformation action is made by a pressurized fluid avoiding the effect of friction during the material deformation. This test condition better represents the deformation conditions when an unconventional process like direct hydroforming is adopted. In the present work authors have developed appropriate numerical models for the Erichsen test and, using the same tooling, except for the punch, a new bulging test has been developed.
For the two different testing conditions the deformation status has been evaluated. The obtained results from the numerical analysis have confirmed a better formability in the case of the non conventional bulging test, with a more uniform distribution of the plastic deformation and of the thickness percentage reduction of the formed blank
The Effect of Temperature, Strain Rate and Strain on the Induced Mechanical Properties of Biaxially Stretched PET
No full textBending can be considered one of easier sheet metal forming processes. In fact, it represents one of the basic variants of applied deformations to metal blanks. However, the numerous research contributions dedicated to sheet metal bending that have been published over the past decade and the constant stream of announcements by R&D departments of machine constructors are strong indications that not all research challenges related to sheet metal bending have been done. This paper reports the developed activity carried out to design a bending testing rig characterized by: a working horizontal axis, a maximum bending length equal to 200 mm, a maximum applicable force equal to 80 kN. A partitioned blankholder has also been designed to allow bending operations on tailored blanks. Moreover, a Graphical User Interface hollows to set up the process parameters and the acquisition of testing data (Temperature and/or Force as function of the process time or punch stroke). CAE tools application had a strategic role to develop the best layout and to find the optimum solutions for the process variables tuning. CAE techniques have allowed to investigate and verify different layout solutions both for the bending process and the structural components of the tooling
Numerical and Experimental Validation for Sheet Metal Hydroforming Process Rules
Full text linkA research program, whose objective is to
understand the influence and the management of the process variables in sheet
metal hydroforming, is developed [1].
The main project objective is to demonstrated how it is possible to orient the
process designer choices in the ndimensions process space, where n is the
number of its variables.
The present work illustrates the results
obtained trying to define the best practise
rules for sheet metal hydroformin
Computer Aided Simulation as valid tool for sheet hydroforming process development
No full textSheet Hydroforming is considered a good opportunity when it is necessary to deal with complex shapes. However, it is common knowledge that it is quite difficult to control such a kind of technology because of an appropriate press tooling is necessary and the press tooling supplier is often the technology supplier for the given problem [1]. Within a larger research program it is demonstrated that it is possible to use traditional hydraulic press tooling having the chance to manage a high level of process variables thanks to the development of a dedicated forming tool named hydroforming cell. The architecture and the number and type of process variables are developed thanks to the extensive usage of CAE techniques. An implicit solver is used to verify the structural behaviour of the hydroforming cell in terms of maximum stress levels and components stiffness while an explicit solver has helped to define the samples shapes and their main features and thanks to them it is possible to explore the process design space. An appropriate experimental phase has demonstrated the effectiveness of the developed procedure
Non Deterministic Approach in Metal Forming Springback Simulation
No full textAn uncertain approach has been evaluated to analyze the finite element analysis
responses for the springback evaluation on a stamped part. In the Metal Forming and Springback
simulations a deterministic approach does not take in account uncertain physical variations related
to material characteristics, friction conditions, tools active surfaces status, etc. Then, if one of the
purposes of the process design it is its reliability, a CAE study in aleatory conditions is the only way
to evaluate the process robustness. A study case has been defined and the explicit simulation was
performed for the forming stage while, the implicit simulation was performed for the springback
phase. Subsequently, a stochastic problem was solved to found the aleatory influence of process
parameters such as: anisotropy coefficient, Young modulus and friction between blank and tools to
evaluate their effect on the component springback. The evaluation of finite element models in
uncertain conditions can be considered like a CAE usage in order to obtain a “Robust Design” for
the examinated problem
Design for Manufacturing for energy absorbing systems
No full textIn the typical scenario of a helicopter crash, impact with the ground is preceded by a substantially vertical drop, with the result that a seated occupant of a helicopter experiences high spinal loads and pelvic deceleration during such crash due to the sudden arresting of vertical downward motion. It has long been recognized that spinal injuries to occupants of helicopters in such crash scenario can be minimized by seat arrangements which limit the deceleration to which the seated occupant is subjected, relative to the helicopter, to a predetermined maximum, by allowing downward movement of the seated occupant relative to the helicopter, at the time of impact with the ground, under a restraining force which, over a limited range of such movement, is limited to a predetermined maximum. In practice, significant benefits, in the way of reduced injuries and reduced seriousness of injuries, can be afforded in this way in such crash situations even where the extent of such controlled vertical movement permitted by the crashworthy seat arrangement is quite limited. Important increase of accident safety is reached with the installation of crashworthy shock absorbers on the main landing gear, but this solution is mostly feasible on military helicopters with long fixed landing gear. Seats can then give high contribution to survivability. Commonly, an energy absorber is a constant load device, if one excludes an initial elastic part of the load-stroke curve. On helicopter seats, this behavior is obtained by plastic deformation of a metal component or scraping of material. In the present work the authors have studied three absorption systems, which differ in relation to their shape, their working conditions and their constructive materials. All the combinations have been analyzed for applications in VIP helicopter seats
- …
