Tetsuya Yoshida

Strength of Highly Ductile Acrylic Adhesive in Butt-Joint under Combined Tension and Torsion

Combined tension-torsion experiments of an adhesively bonded butt-joint were performed using a highly ductile acrylic adhesive. From the experiments, it was found that the multi-axial flow stresses and fracture limits are strongly dependent on shear strain rate and stress multi-axiality. The multi-axial flow stresses are calculated with an extended version of the present authors’constitutive model, and they are compared with the corresponding experimental data. Furthermore, fracture limit curves expressed in the normal and shear stress plane is discussed based on the experimental data and the numerical predictions.

EFFECTS OF TEMPERATURE AND FORMING SPEED ON PLASTIC BENDING OF ADHESIVELY BONDED SHEET METALS

This paper deals with the temperature and rate-dependent elasto-viscoplasticity behaviour of a highly ductile acrylic adhesive and its effect on plastic bending of adhesively bonded sheet metals. Tensile lap shear tests of aluminium single-lap joints were performed at various temperature of 10-40°C at several tensile speeds. Based on the experimental results, a new constitutive model of temperature and rate-dependent elasto-viscoplasticity of the adhesive is presented. From V-bending experiments and the corresponding numerical simulation, it was found that the gull-wing bend is suppressed by high-speed forming at a lower temperature.

Viscoplastic Behavior of Acrylic Adhesive in Butt-Joint at Various Temperatures under Complex Loading : Experimentation and Modelling

The effects of temperature and strain rate on flow stress of a highly ductile acrylic adhesive were investigated by performing tensile lap shear experiments on an adhesively bonded single-lap joint, as well as torsion experiments on a tubular butt-joint at temperatures ranging from 10 to 40oC at various shear strain rates. The flow stress decreases considerably with decreasing strain rate and with temperature rise. The stress-strain responses under multi-axial stress conditions were also examined by performing combined tension-torsion experiments on the butt-joint. A constitutive model of temperature-dependent elasto-viscoplasticity that describes multi-axial stress-strain behavior of the adhesive is presented.

Die-Bending of Adhesively Bonded Sheet Metals

In this paper, the deformation behavior of adhesive layer in die-bending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the bending/unbending shear deformation of the adhesive layer during the die-bending of adhesively bonded sheet metals by using highly ductile acrylic adhesive. Major results obtained are summarized as follows: (1) The bending/unbending shear deformation of the adhesive layer was observed during the die-bending. (2) The punch radius has a large influence on the die-bending in the adhesively bonded sheet metals. (3) It is desirable to perform die-bending at high speed as well as air-bending.

Effects of Thicknesses of Sheet and Adhesive Layer on Plastic-Bending of Adhesively Bonded Sheet Metals

In this paper, the effects of the thicknesses of sheet and adhesive layer on plastic forming of adhesively bonded sheet metals were investigated by experiments and the corresponding numerical simulation. The main conclusions obtained are as follows: (1) When the thickness of the adherends increases, the gull-wing bend of the bent sheet and the transverse shear deformation in the adhesive layer become larger, which in some cases the delamination occurs in the adhesive layer. (2) The gull-wing bend of the bent sheet becomes larger with increasing adhesive layer thickness, but conversely the shear strain in the adhesive layer becomes smaller.

Plastic-Bending of Adhesively Bonded Dissimilar Sheet Metals

In this paper, the effect of material characteristics on plastic forming of adhesively bonded dissimilar sheet metals was investigated by experiments and finite element method (FEM). The acrylic adhesive employed in the experiments has visco-plasticity characteristics with high ductility and strong strain-rate and temperature sensitivity in strength. Major results obtained are summarized as follows: (1) In the adhesively bonded dissimilar sheet metals, the gull-wing bend and the shear deformation of the adhesive layer are suppressed by the combination of the sheet metals when a bending inside sheet has high-tensile strength. (2) The gull-wing bend is suppressed by high-speed forming at a lower temperature as well as the same kind of sheet metals. (3) The calculated results using MSC Marc2010 are relatively good agreement with the experimental results.

Elastic-Plastic Bending Deformation of Adhesively Bonded Sheet Metals in Tensile Lap Shear Tests with Special Reference to Effect of Tensile Speed

In order to investigate the effect of tensile shear-induced bending deformation of sheet metals in adhesively bonded single-lap joint on the shear strength of adhesive, in the present work, tensile lap shear experiments on an aluminium sheet joint bonded with the acrylic adhesive were performed at room temperature. Since this type of adhesive has strong rate sensitivity in flow stress, bending deformation becomes larger with increasing tensile speeds. For the prediction of bending deformation, a numerical analysis of elastic-plastic bending deformation of single-lap sheet metals is presented. From the experimental data and the corresponding numerical results, the effect of tensile speed on the bending deformation is discussed. To reduce the bending deformation, a new experimental technique of reinforcement of an adherend sheet with a high-rigidity plate is proposed.

Asymmetric-Shaped Bending of Adhesively Bonded Sheet Metals

In sheet metal industries, press-formed sheet elements are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, the present authors proposed a new technique that first flat sheets are adhesively bonded together and then press-formed into the final products. In previous study, the problem of the die-bending (V-bending and hat-shaped bending) with symmetrical shape has studied. In this study, asymmetric-shaped bending of adhesively bonded sheet metals was investigated by experiments and FEM analysis method. In the case of asymmetric-shaped bending, it was found that the timing of contact from the die corner to the die hypotenuse is early in the press-forming process compared with symmetrical bending (V-bending and hat-shaped bending). For the FEM analysis results, the maximum shear strain in asymmetric-shaped bending was smaller than that in symmetric-shaped bending at the hat-shaped side. Thus, the shape of the die has a large influence on the die-bending of adhesively bonded sheet metals.

Deformation Behavior of Adhesive Layer in Stretch-Bending/Unbending for Adhesively Bonded Sheet Metals

In this paper, the deformation behavior of adhesive layer in stretch-bending/unbending for adhesively bonded sheet metals was investigated by experiments and finite element method (FEM). We paid special attention to the cyclic shear deformation of the adhesive layers during the plastic working. Major results obtained are summarized as follows: (1) When the adhesively bonded sheet metals is bent and pulled out at a 90° angle, shear deformation due to bending of the adhesive layer starts shortly before reaching the die corner and unbending starts at the middle of the corner. (2) The die radius has a large influence on the bending behavior. (3) It is possible to suppress shear deformation of the adhesive layer by using a material with small tensile strength as one of the two adherends.

205 Finite element analysis of elastio-viscoplastic deformation behavior of high ductile adhesive using complex-step derivative method

Takeshi UEMORI, Kinki University, 1 Takaya-Umenobe, Higashi-Hiroshima, Hiroshima, 739-2116 Japan Taro TOKUDA, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsaki-kamijima, Toyotagun, Hiroshima, 725-0231 Japan Tetsuya YOSHIDA, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsaki-kamijima, Toyotagun, Hiroshima, 725-0231 Japan Michihiro TAKIGUCHI, Hiroshima National College of Maritime Technology, 4272-1, Higashino, Ohsaki-kamijima, Toyotagun, Hiroshima, 725-0231 Japan Fusahito YOSHIDA, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-8527 Japan