Forming limit diagram prediction of AA5052/polyethylene/AA5052 sandwich sheets

Experimental and finite element study on the spring back of double curved aluminum/polypropylene/aluminum sandwich sheet

Experimental characterization, analytical and numerical investigations of metal/polymer/metal sandwich composites – Part 1: Deep drawing

Metal/polymer/metal laminated sheets have shown promising properties, as being light weight, in automotive and aircraft industries. In this paper, the effect of punch radius on springback in the early stage of V-die bending process of aluminum/polypropylene/aluminum sheets is studied both numerically and experimentally. To analyze springback behavior, contact pressure evolution during bending process was studied using numerical simulation. Springback behavior relies on bending moment and sheet thinning. Bending moment and sheet thinning depend on circumferential and transverse stress distributions along sheet thickness and sheet length. Overall opposite effect of bending moment and sheet thinning makes an increase in springback with punch radius. Parametric study was performed to investigate the effect of polymeric core on springback. It was observed that in a given thickness configuration, springback of laminate lies between those of polymeric and metallic monolayer sheets with the same thickness. Also, an increase in sandwich sheet thickness leads to a decrease in springback.

Al3105/polypropylene/Al3105 laminates springback in V-die bending

The bending and springback behaviors of sandwich sheets are more complicated than those of monolithic layer metallic sheet due to the extremely large difference in mechanical properties and in the gauges of polymer core and the skin sheet. In the present study, the bending and springback behaviors of aluminum-polymer sandwich sheets were investigated by using analytical method and conducting experiments and numerical simulations. A simplified analytical model was proposed to calculate the bending moments for sandwich sheet in unconstrained bending process through analyzing the strain and stress distributions of skin sheet and core materials. Then, the analytical model was applied to predict the springback of sandwich sheets after bending. Numerical simulations and experiments of unconstrained bending process for aluminum-polymer sandwich sheets were conducted to investigate the influences of mechanical properties of each layer and thickness ratio of two layers on the folding defects, neutral layer location, and springback. The results show that the neutral layer shifts dramatically toward the compression region of the specimen during bending. The folding angle mainly relates to the strength difference between the skin sheet and the core polymer. The springback angle of sandwich sheet is mainly determined by the mechanical properties of skin sheet.

Unconstrained bending and springback behaviors of aluminum-polymer sandwich sheets

In this report an analysis is made of the behavior of sandwich beams in which the core polymer is laminated on both sides with surface metal sheets, each of which has a different thickness and mechanical properties when they are loaded with a uniform bending moment which is then released resulting in springback of the bent sandwich beam. It is assumed that the polymer behaves elastically because the bending strain in the core is small and its elastic limit is much larger than that of metals. Sandwich beams have various elastoplstic stess distributions when bent depending on the mutual relationships between their dimensions, the mechanical moduli, and the applied bending moment. Further, residual curvatures, shifting position of neutral axis, and residual stress distributions in sandwich beams variously elastoplastically stressed initially on the decrease of applied bending moment are analyzed.

Bending and springback theory of metal-polymer sandwich laminates

The cold press workability of aluminum-polyethylene sandwich laminates is experimentally investigated by a deep drawing process with a conical die. “Planium” of 2 mm thickness, in which the core layer, high density polyethylene, is sandwich-laminated between two aluminum sheets, is used as a test specimen. Soybean oil is employed as a lubricant. The dimensions of the drawing die set are determined for a circular, blank so that the tensile fracture of the drawn.cup occurs at the top corner of the punch. The limiting draw ratio (LDR) is experimentally explored by using many blanks of various initial diameters. In general the maximum punch load in successful drawing increases linearly with increasing draw ratio. Because of the sandwich structure, the fracture of the drawn cup occurs twice. The initial fracture (LDRs) corresponds to a fine bending fracture at the aluminum surface. The second fracture (LDRB) is the complete fracture of the whole laminate. The effect of punch corner radius, working velocity and thickness fraction of aluminum and polyethylene on LDRS and LDRB are studied. The strain distributions of deep drawn cup in three orthogonal directions are analyzed experimentally.

Experimental study on cold press workability of aluminum-polyethylene sandwich laminates

Microscopic composite mechanism on upper and lower yield points of amorphous polymer solids

A general theory of linear viscoelasticity under complex stress is analysed by utilizing the Laplace transformation and is applied to Hertz's contact problem for measuring the creep recovery in the penetration of a steel ball. As in the similar method of uniaxial compression, the temperature dependence of characteristic relaxation times can be computed from the experimental results on (residual depth of penetration creep recovery) ∼θ (temperature) curves by using the analytical results. The temperature dependence is in good agreement with that obtained from the results in uniaxial compression. The method using the RN (Rockwell Number) ∼θ curves obtained at a constant rate of temperature rise (2°C min−1) by a conventional Rockwell testing machine, is recommended as the simplest method and may be successfully used for various polymer solids. The effect of differences in molecular structure on the temperature dependence of mechanical behavior can be demonstrated clearly by this method. The results on thermos...

Theoretical and Experimental Studies on Temperature Dependence of the Mechanical Behavior of Polymer Solids by a Creep Recovery Method. Part 2. Penetration of a Steel Ball

Katsuhiko Ito

Papers

Bending and springback theory of metal-polymer sandwich laminates

Experimental study on cold press workability of aluminum-polyethylene sandwich laminates

Microscopic composite mechanism on upper and lower yield points of amorphous polymer solids

Theoretical and Experimental Studies on Temperature Dependence of the Mechanical Behavior of Polymer Solids by a Creep Recovery Method. Part 2. Penetration of a Steel Ball