Abstract
Roll bonding is a process to join two or more different materials permanently in a rolling process. A typical industrial application is the manufacturing of aluminum sheets for heat exchangers in cars where the solder is joined onto a base layer by roll bonding. From a modelling point of view the challenge is to describe the bond formation and failure of the different material layers within a FE-process model. Most methods established today either tie the different layers together or treat them as completely separate. The problem for both assumptions is that they are not applicable to describe the influence of tangential stresses that can cause layer shifting and occur in addition to the normal stresses within the roll gap. To overcome these restrictions in this paper a 2D FE-model is presented that integrates an adapted contact formulation being able to join two bodies that are completely separated at the start of the simulation. The contact formulation is contained in a user subroutine that models bond formation by adhesion in dependence of material flow and load. Additionally if the deformation conditions are detrimental already established bonds can fail. This FE-model is then used to investigate the process boundaries of the first passes of a typical rolling schedule in terms of achievable height reductions. The results show that passes with unfavorable height reduction introduce tensile and shear stresses that can lead to incomplete bonding or can even destroy the bond entirely. It is expected that, with adequate calibration, the developed FE-model can be used to identify conditions that are profitable for bond formation in roll bonding prior to production and hence can lead to shorter rolling schedules with higher robustness.
Highlights
In roll bonding two or more separate metal strips or plates are fused together via the plastic deformation generated in the roll gap of a rolling mill
This paper proposes a FE-model using a user subroutine to model bond formation and failure at the interface of the bodies based on parameters obtained from laboratory experiments
In the current paper a FE-model to describe bond formation and failure was introduced based on the Abaqus user subroutine UINTER
Summary
In roll bonding two or more separate metal strips or plates are fused together via the plastic deformation generated in the roll gap of a rolling mill. To obtain the bond strength of an arbitrary material as a function of surface enlargement and temperature for different stress component combinations, complex laboratory experiments detailed elsewhere [8] are necessary. Curves that schematically show the maximum bond strength reached in experiments with two different surface enlargements in the normal-tangential-stress-space relevant for rolling are shown as red lines in Within the process model all mechanical interactions that occur at the interface between the layers are handled by the UNITER subroutine.
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