Papers by Keyword: Forming

Abstract: The formability of tailor welded blanks is significantly reduced compared with the homogeneous blanks. One of the important factor that are behind this fact is the material property changes a sides the welding line that merge the base materials. The work presented in this paper deals with numerical simulation concerning forming of a rectangular shaped part made from tailored blanks (TWBs), having the welding line situated symmetrical with respect to the part geometry. Due to dissimilar base materials of the TWBs, it is difficult to predict the maximal depth of the formed part. The presented research is trying to determine the maximal depth of the TWBs part based on the maximal depth of the parts obtained from each base material partly. To simulate the forming process the academically version of the Dynaform 5.8.1 software have been used. The obtained results are presented in the final part of this paper work.

Abstract: This paper presents the development of a machine tool which combines the forming and the surface strengthening processes for large scale aircraft parts together. The developed machine tool produces the required part shape not by bending but by combination of differential compressive plastic stresses induced by shot peening to different areas of the part in a predetermined sequence. It has a total mass under 4200kg and is capable of forming and strengthening panels of 15x1.5x0.02m³ in size. The machine tool has been successfully applied for production of honeycomb wing panels of Be-200 multipurpose amphibious aircraft made of aluminum alloy.

Abstract: Thermoplastic composite has become preferred material for wind turbine blade with high performance, low cost and greenization. The fused mass of the thermoplastic resin has high viscosity and the forming of the thermoplastic composite materials is laborious, quality is not readily guaranteed, thus, the widespread use of thermoplastic composite blades for wind turbine is restricted. Based on the analysis of all kinds of the characteristics of thermoplastic forming technology, the paper has points out that the diaphragm forming is especially suitable for making a hyperboloid, variable thickness, large size wind turbine thermoplastic composite blade structure. The key to improving the forming quality and the efficiency of the thermoplastic blade forming is to establish finite element deformation model of a diaphragm forming process, to effectively control the process parameters such as temperature, pressure, forming rate. Conducting research on thermoplastic blade diaphragm forming technology lay the foundation for the industrialization of thermoplastic wind turbine blade.

Abstract: Standard finite elements can exhibit the numerical artifact of intra-plyshear locking during forming simulations. The displacement fields of elementsare piecewise continuous and cannot correctly capturediscontinuities in the shear field. This shear locking is illustrated insimulations of bias-extension experiments with an unaligned mesh. Two simpletests were developed as a critical indicator of intra-ply shear locking intriangular elements. A single-element-test shows the origin of the locking anda pull-out test indicates locking caused by small misalignments of theelements.

Abstract: A hybrid finite element discrete mesoscopic approach is used to model the forming of composite parts using a unidirectional glass prepreg non-crimp fabric (NCF). The tensile behavior of the fabric is represented using 1-D beam elements, and the shearing behavior is captured using 2-D shell elements into an ABAQUS/Explicit finite element model via a user-defined material subroutine. The forming of a hemisphere is simulated using a finite element model of the fabric, and the results are compared to a thermostamped part as a demonstration of the capabilities of the used methodology. Forming simulations using a double-dome geometry, which has been used in an international benchmarking program, were then performed with the validated finite element model to explore the ability of the unidirectional fabric to accommodate the presence of interlaminate cabling.

Abstract: A new forming procedure was developed to produce shape memory composite structures having structural composite skins over a shape memory polymer core. Core material was obtained by solid state foaming of an epoxy polyester resin with remarkably shape memory properties. The composite skin consisted of a two-layer unidirectional thermoplastic composite (glass filled polypropylene). Skins were joined to the foamed core by hot compression without any adhesive: a very good adhesion was obtained as experimental tests confirmed. The structure of the foam core was investigated by means of computer axial tomography. Final shape memory composite panels were mechanically tested by three point bending before and after a shape memory step. This step consisted of a compression to reduce the panel thickness up to 60%. At the end of the bending test the panel shape was recovered by heating and a new memory step was performed with a higher thickness reduction. Memory steps were performed at room temperature and 120 °C so as to test the foam core in the glassy and rubbery state, respectively. Shape memory tests revealed the ability of the shape memory composite structures to recover the initial shape also after severe damaging (i.e. after room temperature compression). Compressing the panel at a temperature higher than the foam resin glass transition temperature minimally affects composite stiffness.

Abstract: Traditionally forming tools for a press are machined with a CNC-machine. This is quite time consuming - calculating tool tracks, selecting cutting tools, cutting blanks, design fixation and finally machining - especially for a small batch of parts. One alternative method is to cut a die and a draw punch tools from a blank sheet and bunching the plates. Clamping plates together is fast and easy to implement by using for example studs and bars with a certain tolerance to ensure alignment. A laser, a water jet or a plasma cutter can be used for cutting plates. Especially the laser and the water jet cutting are precise methods giving a fine surface quality without a need for fine-tuning. The method saves material compared with machining because a die and a punch could be cut at the same time from a blank sheet as compatible pair as well as the needed amount of plates could be estimated depending of the length of a pressed product. University of Oulu, Oulu Southern institute, Future Manufacturing Technology -group has manufactured several forming tools within this technique and found it extremely suitable for experimenting different solutions and options fast. Furthermore, the method is likely to help especially SMEs in their R&D-phase by lowering production costs in a cost-efficiency way.

Abstract: Simulation of the dry reinforcement preforming, first step of the Resin Transfer Moulding process, become necessary to determine the feasibility of the forming process, compute the fiber directions in the final composite component, and optimize process parameters during this step. Contrary to geometrical approaches, based on fishnet algorithms, finite element methods can take into account the actual physical parameters, the real boundary conditions and the mechanical behavior of the textile reinforcement. The fabric can be modeled either as continuum media with specific material behavior [5, 6], or using discrete structural elements to describe the textile structure at the mesoscopic scale. A semi-discrete approach, which is a compromise between the above continuous and discrete approaches, is also used for simulation. A discrete approach for the simulation of the preforming of dry woven reinforcement has been proposed and presented in a previous paper. This modelling is based on a “unit cell” formulated with elastic isotropic shells coupled to axial connectors. The connectors, which replace bars or beams largely studied in other discrete approaches, reinforce the structure in the yarn directions and naturally capture the specific anisotropic behavior of fabric. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomena with the punch and die. The linear characteristic of the connectors, has been extended to a non linear behaviour in the present paper to better account for fabric undulation. Using this numerical model, we propose, in this work to study the effect of process parameters on the woven fabric deformation during the performing step. The emphasis will be placed on the analysis of the influence of the blank holder pressure on the shear angle distribution.

Abstract: see enclosed file

Abstract: ALEXANDER IVANOVICH OLEINIKOV Aircraft Engineering Faculty, Komsomolsk-on-Amur State Technical University Lenina prospect 27, 681013 Komsomolsk-on-Amur, Russian Federation a.i.oleinikov@mail.ru Keywords: forming, creep, age, transversely isotropic, kind of the stress state effect, wing panel, inverse problem, reverse engineering, computer-aided process design system. Abstract. Problems of inelastic straining of three-dimensional bodies with large displacements and turns are considered. In addition to the sought fields, surface forces and boundary displacements, original size and shape have also to be determined from specified residual displacements in these problems. Currently, forming of light metals poses tremendous challenges due to their low ductility at room temperature and their unusual deformation characteristics at hot-cold work: strong asymmetry between tensile and compressive behavior, and a very pronounced anisotropy. We proposed the constitutive models of steady-state creep of initially transverse isotropy structural materials the kind of the stress state has influence [1]. The forming process considered includes two stages: active stage of elastoviscoplastic straining of the blank in the die tooling and passive stage of unloading of the blank withdrawn from the die tooling. The final stress-strain state at the active stage is the initial state for the passive stage. Unloading is considered as purely elastic straining, with no increments of inelastic strains. The active stage, in turn, also includes two steps. At the first step, the frontal faces of the “cold” blank are pressed to the working surfaces of the die tooling, which results in elastoplastic straining of the blank. The second step includes the processes of stress relaxation and creep strain in the blank fixed in this die tooling during a given time at an elevated ageing temperature. Computer modeling of these forming processes involves the use of the finite element method for consecutive solutions of three-dimensional quasi-static problems of elastoplastic straining, relaxation, and unloading, and also determining boundary conditions from given residual displacements [2] . The paper gives basics of the developed computer-aided system of design, modeling, and electronic simulation targeting the processes of manufacture of wing integral panels. System application data resulting from computation of 3D-involute of a CAD-based panel model, determination of working surfaces of die tooling, three-dimensional analysis of stresses, and simulation of panel shaping under diverse thermo-mechanical and speed conditions are demonstrated. Modeling of forming of wing panels of the SSJ-100 aircraft are considered [2,3]. The modeling results can be used to calculate the die tooling, determine the panel processibility, and control panel rejection in the course of forming [3]. References [1] A.I. Oleinikov, Models for the steady-state creep of transversely isotropic materials with different tension and compression characteristics, J. Ind. Appl. Math. 5 (2011) 406-409. [2] B.D. Annin, A.I. Oleinikov and K.S. Bormotin, Modeling of forming of wing panels of the SSJ-100 aircraft, J. Appl. Mech. Physics 51 (2010) 579-589. [3] A.I. Oleinikov, A.I. Pekarsh, Integrated Design of Integral Panel Manufacture Processes. Dalnauka, Vladivostok, 2010.