Drawbead Performance and Model of Drawbead Forces for Sheet A 5182-0

(Received on June 29, 1994)

Toshihiko KUWABARA, Hisashi NISHIMURA and Masayuki SHUUNO

Experiments on drawbead restraining have been carried out with several bead configurations, using sheet aluminum alloy A5182-0. The geometry of the male beads considered is round. With the binder hold-down force (BHF) as an independent variable, the magnitude of the drawbead restraining force (DBRF), the coefficient of friction and the thickness reduction of sheet strips are measured. Moreover, a simple method for predicting the DBRF is presented using energy method. The results obtained are as follows. 1) The coefficient of friction is found to decrease with increasing the BHIF. 2) The configurations of a sheet strip passing throu-h a drawbead vary with the BHF: they come to conform gradually to the profile radius of the beads with increasing BHF. 3) The calculated drawbead restraining forces are in good agreement with measured ones, provided that the configuration of a sheet strip passing through a drawbead is properly assumed in the calculation model. 4) The nominal thickness strain of sheet strips having passed through a drawbead decreases linearly with increasing the BHF.

Keywords: sheet metal forming, drawbead, sheet aluminum alloy A5182-0, energy method, thickness@reduction



Plastic Deformation of Pipes for Automotive Side Impact Beams during Static 3-Point Load Type Bending Test

(Received on July 7, 1994)

Hiroto TANABE, Akihiro MIYASAKA, Kazumasa YAMAZAKI and Yoshikuni TOKUNAGA

With regard to pipes for automotive side impact beams used as car body reinforcing member at the time of a car side crash, some variations of bending deformation were studied experimentally by a static 3-point load type bending test. The process of the deformation was classified into the following three : pipe flattening in a cross section, plastic collapse and circumferential buckling. Such deformation process are discussed together with the applied load versus punch stroke relationship and the absorbed energy characteristics, and the resultant maximum loads are estimated. Plastic collapse and circumferential buckling occurred at the maximum load point and the point, load start to decrease abruptly, respectively. As the plastic deformation of pipe during bending is concentrated at the center of the pipe, absorbed energy characteristics of pipes depend on the plastic deformation of pipes at the center portion of the device not depend on bending span.

Keywords:die bending, 3-point load type bending, plastic collapse, buckling in circumferential direction,@absorbed energy characteristic in bending,plastic deformation, automotive side impact beams.



Influence of Strain Rate on Elastic Modulus of Polymers

(Received on July 15, 1994)

Tetsuya AYA and Toshio NAKAYAMA

Uniaxial tension tests of polymers, such as high-density polyethylene (HDPE), poly (vinylidene fluoride) (PVdF), polyoxymetheylene (POM), polyamideimide (PAI) and polyetheretherketone (PEEK), are carried out at various strain rates. When the strain rate increases ftom the order of 10-'S-' to 10-'s-', the elastic modulus increases as well as the other cases. The dependence of elastic modulus on strain rate is very different among the tested polymers. Specially, in the case of PEEK, a significant change of the value appears between above and below glass-transition temperature. A spherical model has been proposed to understand the elastic moduli of polymers under hydrostatic pressure in the previous paper. This model is extended to propose an experimental equation of the clastic modulus at various strain rates in these experimental regions in the present paper. lt is concluded that the equation is able to des(,-rihe the dependence of elastic modulus on strain rate with only one parameter.

Keywords:tension test, polymer, strain rate, tensile speed, elastic modulus, Young's modulus,intermolecular force, potential theory, elastic defc)rmation, glass-transition temperature



Elasto-Plastic Finite Element Method of the Deformation of Plate with Voids or Inclusions Arranged Regularly

(Received on August 15, 1994)

Toshio TATENAMI

When an external force in planc is exerted on a plate material on which many holes or inclusions are regularly arranged, incremental elasto-plastic F.E.M. is applied to the minimum material region which is an unit shape of repetition of hole or inclusion. The extemal force may be considered as a macroscopically uniform stress state and microscopic stress acfing on the material is calculated. The direction of principal stress of the external force will be different from the symmetric axis of arrangement of holes or inclusions. The treatment of the boundary conditions is the most important in this problem, and the proposed procedure for the calculation method is described in detail. This concept will bc possible to be adapted to F.E.M. for rigid plastic materials, and extended to a three dimensional problem of composite materials.

Keywords:numerical analysis, finite clement method, elasto-plastic FEM, boundary@condition, composite material, hole, inclusion, porosity, uniform stress, plate, unit shape