Forming forces in single point incremental forming: prediction by finite element simulations, validation and sensitivity (original) (raw)
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Identification of material parameters to predict Single Point Incremental Forming forces
2008
The purpose of this article is to develop an inverse method for adjusting the material parameters for single point incremental forming (SPIF). The main idea consists in FEM simulations of simple tests involving the SPIF specificities (the "line test") performed on the machine used for the process itself. This approach decreases the equipment cost. It has the advantage that the material parameters are fitted for heterogeneous stress and strain fields close to the ones occurring during the actual process. A first set of material parameters, adjusted for the aluminum alloy AA3103 with classical tests (tensile and cyclic shear tests), is compared with parameters adjusted by the line test. It is shown that the chosen tests and the strain state level have an important impact on the adjusted material data and on the accuracy of the tool force prediction reached during the SPIF process.
Force prediction for single point incremental forming deduced from experimental and FEM observations
The International Journal of Advanced Manufacturing Technology, 2010
The aim of the study was to establish practical formulae allowing to predict the forces occurring during the single point incremental forming process. This study has been based on a large set of systematic experiments on the one hand and on results of finite elements modeling simulations on the other. This led to analytical formulae allowing to compute the three main components of the force for five selected materials in function of the working conditions (sheet thickness, wall angle, tool diameter, and step down) with a good precision. Moreover, a general model has been deduced, allowing to compute an approximate value for the force for any material, based on knowledge of the tensile strength only.
Evaluation of strain and stress states in the single point incremental forming process
The International Journal of Advanced Manufacturing Technology, 2015
Single point incremental forming (SPIF) is a promising manufacturing process suitable for small batch production. Furthermore, the material formability is enhanced in comparison with the conventional sheet metal forming processes, resulting from the small plastic zone and the incremental nature. Nevertheless, the further development of the SPIF process requires the full understanding of the material deformation mechanism, which is of great importance for the effective process optimization. In this study, a comprehensive finite element model has been developed to analyse the state of strain and stress in the vicinity of the contact area, where the plastic deformation increases by means of the forming tool action. The numerical model is firstly validated with experimental results from a simple truncated cone of AA7075-O aluminium alloy, namely, the forming force evolution, the final thickness and the plastic strain distributions. In order to evaluate accurately the through-thickness gradients, the blank is modelled with solid finite elements. The small contact area between the forming tool and the sheet produces a negative mean stress under the tool, postponing the ductile fracture occurrence. On the other hand, the residual stresses in both circumferential and meridional directions are positive in the inner skin of the cone and negative in the outer skin. They arise predominantly along the circumferential direction due to the geometrical restrictions in this direction.
Material Data Identification to Model the Single Point Incremental Forming Process
2010
In this study, the Single Point Incremental Forming process (SPIF) is applied on a specific aluminium alloy used in the aerospace industry since this technique and material combine a low specific weight, high strength and stiffness properties and high strain levels. To be able to optimize the process, a model and its material parameters are required. It was noticed that a simple isotropic hardening model was not sufficient to provide an accurate tool force prediction [1]. Therefore an elasto-plastic law with a mixed isotropic-kinematic hardening is investigated. The inverse method coupled with the Finite Element (FE) code: "Lagamine" [2] is used to fit the material data of this complex law. In order to validate the model and the material data, a Line test and a Cone test are used.
An FEM-aided investigation of the deformation during Single Point Incremental Forming
Incremental forming is an innovative and flexible sheet metal forming technology for small batch production and prototyping, which does not require any dedicated die or punch to form a complex shape. This paper investigates the process of single point incremental forming of an aluminium cone both experimentally and numerically. Finite element models are established to simulate the process. The output of the simulation is given in terms of final geometry, the thickness profile of the product and the strain history and distribution during the deformation. Comparison between the simulation results and the experimental data is made.
Experimentation and FE simulation of single point incremental forming
Materials Today: Proceedings, 2019
One of the emerging flexible forming technologies in the sheet metal engineering is the incremental sheet forming, it uses universal tooling that is mostly part independent. Hence this process provide higher flexibility reducing the product development greatly and making it useful for low volume production. Single Point Incremental forming is drawing attention of the researchers & scientist all over the world because of the attractive characteristics. Like: improved formability, elimination of die & conventional press and ease of operation on general purpose Vertical Machining Centre. As this way of creating sheet metal formed products is in development stage, the factors affecting this needs comprehensive investigations. In this paper experimental and numerical investigation of formability of Aluminium 8011 alloy are presented and compared by preparing a conical frustum shape using SPIF process. The complete process is simulated using CATIA manufacturing simulation model to generate the path of Hemispherical end tool tip. Numeric Control (NC) part program is generated with the help of this simulated path to form the sheet into conical frustum shape on CNC mill machine. Four process parameters viz. vertical step depth, feed rate, spindle speed and angle of cone are chosen for the experimental investigations keeping height of the cone and material sheet thickness constant. Temperature, thickness reduction, strain and machining time are selected as a response variable. Optimizations are performed using TAGUCHI and ANOVA while the numerical study of the process is performed through ANSYS workbench software to predict stress, strain, temperature and thickness Results of experiments and numerical study are in close accord.
Periodica Polytechnica Mechanical Engineering
Incremental sheet forming (ISF) is an innovative cold forming operation and has enticed great interests owing to its flexibility and capability to manufacture various complex 3D shapes with low costs and minimum requirements. Single point incremental forming (SPIF) is the most popular type of ISF process and has high quality and less occurrence of defects for the formed products if the operating parameters are achieved and evaluated with high precision. In this study, the impact of tool diameter and forming angle on the forming force, thickness distribution, thinning ratio, effective plastic strain, forming depth and fracture behaviour was explored. AA1050 aluminium alloy and DC04 carbon steel were employed to produce a truncated cone in accordance with the SPIF process. A 3D finite element model was required to achieve a well-established investigation. The SPIF of a truncated cone numerical model was adopted to build a model with the same conditions as of the experimental work with...
Experimental Validation of Finite Element Simulations of Single Point Incremental Forming
2005
Single-point incremental forming (SPIF) is a sheet metal forming technique that has gained particular interest in rapid prototyping and small volume production. The study of the underlying forming mechanisms is supported by new developments in finite element simulations and experimental full field strain measurements. This article aims to describe the possibilities and difficulties encountered during validation of finite element predictions of the incremental forming process. The drawing of a straight line into a metal plate was selected as a first test case for this kind of validation. Results of both finite element simulation and experimental work will be discussed.
The deformation in sheet metal forming processes, such as stamping, occurs under plane stress condition in which through-thickness stresses (í µí¼ zz , í µí¼ xz , í µí¼ yz) are negligible and application of a two-dimensional (2D), plane stress yield function is sufficient. However, in incremental sheet forming processes, significant out-of-plane shears develop in the sheet metal, which necessitates the use of a three-dimensional (3D) yield function to account for normal and shear stress components. To simulate the single point incremental forming (SPIF) of 7075-O aluminum alloy sheet, three different yield functions namely; von Mises, Hill's 1948, and Barlat Yld2004-18p were used. The Yld2004-18p was implemented into the commercial FEA code ABAQUS as a user material subroutine (VUMAT), by considering the cutting-plane algorithm for the integration of the elasto-plastic constitutive model. For direct CPU time comparison, the same Yld2004-18p VUMAT was reduced to von Mises and Hill's 1948 yield functions and finite element simulations of SPIF were repeated. Anisotropy coefficients of Yld2004-18p and Hill's 1948 were calculated using uniaxial tensile test data for AA7075-O. A detailed comparison of the three yield functions ' predictions were made with respect to the effective plastic strain distribution, part thickness, tool force and moment, and development of stress and strain tensor components.
Incremental sheet forming (ISF) is a very promising technology to manufacture sheet metal products by the CNC controlled movement of a simple forming tool. It is considered as an innovative and flexible sheet metal forming technology for small batch production and prototyping, which does not require any dedicated die or punch to form a complex shape. Although incremental sheet forming is a slow process, the cost reduction linked to the fact that punches or dies are avoided, makes it a very suitable process for low series production, in comparison with the traditional stamping or drawing processes. This paper investigates the process of single point incremental forming of aluminum truncated cones and square pyramids geometries both experimentally and numerically. Concerning the numerical simulation, the finite element models are established to simulate the process by using a static implicit finite element code ABAQUS/Standard. In this article, the reported approaches were mainly focused on the influence of some crucial computational parameters. The influence of several parameters will be discussed: the initial sheet thickness and the workpiece geometry. The output of the simulation is given in terms of the punch forces evolution generated in this forming process and the final geometry. A comparison between the simulation results and the experimental data is made to assess the suitability of the numerical models. Experimental and numerical results obtained allow having a better knowledge of mechanical responses from different parts manufactured by SPIF with the aim to improve their accuracy. Predicted results show good agreement with experimental data for these geometries of the cones and pyramids. It is also concluded that the numerical simulation might be exploited for optimization of the incremental forming process of sheet metal.