Papers by Keyword: Upsetting Test

Abstract: Open-cell Al-Si foam samples were produced using infiltration casting technique. The metal infiltration process was performed in a specially designed and built setup consisting of a vertical chamber resistance furnace, a pressurization chamber connected to an Argon gas cylinder through a control manifold. To control the relative density of the produced foams, non-compacted and compacted preforms (5 MPa) were prepared from 2 or 4 mm NaCl particles. The compaction was performed using a hydraulic press in the same infiltration chamber. Argon pressure of 3 bars was applied to infiltrate the preforms with the aluminum alloy after melting at 750 °C. The produced aluminum foam specimens show no lack of filling, a high degree of preform replication, and good homogeneity of pore sizes. The preliminary physical and mechanical characterization tests, including relative density, plateau stress, densification strain, and elastic modulus of the foam, are comparable to the values reported in previous investigations, in which more complicated, time-consuming, higher energy, and costly techniques were used. Further investigations on wider ranges of particle sizes, compaction, and infiltration pressures are currently in progress.

Abstract: The advantages of polymer materials such as high strength and stiffness to weight ratio, corrosion resistance and manufacturing flexibility have increased the industry demands to utilize them in high performance applications. Designing polymer structures depends on a high understanding of their hyper-elastic behaviour, therefore investigating the mechanical behaviour of polymers is necessary. In this paper, the nonlinear behaviour of epoxy polymer is examined under upsetting test. The main aim of the study is to analyse the effect of strain rate on the mechanical behaviour of epoxy polymer. The cylindrical polymer epoxy specimen, 20mm in length and in diameter, was manufactured. The upsetting tests provided quasi-static compressive loads which were adjusted in the loading rates of 0.1, 1, 50, 100, 200 and 500 mm/min. The loadings were continued until complete fracture was observed. Each loading rate was repeated for at least 3 specimens to ensure a reasonably good statistical sampling. The average data of each test is used to produce the load-displacement graphs of the specimens, from which stress-strain curves are extracted to show the behaviour of epoxy polymer. The results show a 37% increase of yield stresses when the loading rate is increased from 0.1 to 500 mm/min and the yield strains increase by 26%. The stress-strain curves are nonlinear where the slope increases when the loading rate is raised from 0.1 to 100 mm/min but then decreases when the rate is further raised from 100 to 500 mm/min. The maximum load that can be sustained is increased with loading rate. This can be due to the microstructure deformation response of epoxy polymer. This polymer is categorised as large-strain material by showing exhibiting large deformations under different rates of compression loading.

Abstract: Metal foams are two-phase compounds of a gas and a solid with several interesting physical and mechanical properties; in particular they have very low density, good rigidity, excellent energy absorption, high vibration damping. At now, the final shape of foamed devices is directly obtained through the foaming process itself and no further shaping steps are expected. Anyway, the plastic formability of metal foams, in order to both characterize the material itself and to produce more complex parts, seems to be useful for several industrial applications. Since metal foams are quite new products, the basic aspects ruling plastic deformation processes are still partially unknown and FEM methods may represent a valid tool for deepening these topics. This work deals with the formability of Aluminum Foam Sandwich (AFS) panels and it is focused on the FEM simulation of a compression processes. A numerical model was set up by using the FEM code Deform 2D v10.1. Foam behaviour was simulated by means of a compressible (porous) material model and the foam cracking was simulated using a damage model based on the foam density parameter. Some FEM routines were implemented into the FEM code to take into account both the non-homogeneous distribution and the strain hardening effect of the foam cells. An experimental campaign based on the compression of AFS panels made of close cells foam was carried out to fine tune and to validate the model. In particular, experimental data regarding load stroke curves and foam density were used to optimize the material description. An innovative solution, based on a non-linear relation between foam density and effective strain of the foam, was implemented into the FEM code.

Abstract: Bulk Al6082 alloy is subjected to ECAP using route Bc. This paper focuses on the determination of the anisotropy coefficients and equivalent stress-equivalent strain curve using continuum mechanics equations. Assuming the material to be rigid-plastic, the parameters of the constitutive equation are determined with the aid of measuring the deformation and the uniaxial yield stress during upsetting tests in three perpendicular directions.

Abstract: The flow behavior of a semi-solid A356 alloy at high solid fraction was studied. The mushy zone was considered as an effective two-phase, so that the solid continuum can be compressible porous media, and the liquid phase interaction with the solid skeleton was of Darcy type. The semi-solid flow through the upsetting test was modeled in ABAQUS finite element method software. The Gurson yield criterion has been developed for the modeling process of the flow behavior of solid porous medium. Specimens were globulized by a thermomechanical process and then were tested for various percentages of upsetting. The distribution of solid fraction along the radius of the specimens at different height reduction showed a good correlation with model prediction.