Deformation-induced Roughening Research Articles

Deformation-Induced Roughening by Contact Compression in the Presence of Oils with Different Viscosity: Experiment and Numerical Simulation

The aim of the work is to show both the similarities and differences in the formation of deformation-induced roughness in contact compression in the presence of oil and the problem of free surface roughing during uniaxial stretching in a plastic area. The relationships between changes in the roughness are caused by the deformation of the sample and the viscosity of oil at the contact area. It has been shown that normal contact loading with the presence of oil initially leads to an increase in surface roughness, then to its smoothening. The results of the experimental research have been compared with numerical simulation made using FSI (Fluid Structure Interaction) and ABAQUS systems. Using finite element calculations, it was possible to explain the phenomenon of roughness formation on the surface of a smooth steel sample. The changes in the structure of the smooth surface resulting from compression in the presence of oil are caused by the rotation and deformation of surface grains. The roughness of this structure is dependent on the viscosity of oil: the more viscous the liquid is, the rougher texture is formed.

Modeling the topographic evolution of a rough metallic surface resulting from impact of water droplets

Waterjet peening (WP) is usually used to roughen metallic surfaces in order to improve cell adhesion on biomedical implants. Hence, surface roughness control using WP is of prime importance for such applications. A random finite element model of WP was developed, aimed at characterizing the surface coverage (the ratio of jet-affected area over total contact area) and surface roughness (in particular, the heights distribution). One perfectly flat and three rough metallic surfaces with different initial Sa (area arithmetic mean height) were generated, impacted and compared with each other. Numerical results show that a rougher initial surface necessitates more impingements than a smooth one to attain full surface coverage. The mechanisms influencing surface topography evolution, namely plastic deformation-induced roughening, peak clipping, valley deepening and valley filling are discussed. By modeling the roughness evolution resulting from WP, it appears that the process can be applied not only to roughen but also to polish rough initial surfaces in the investigated range. The present approach allows for systematic tuning of the system parameters in order to control the surface roughness.

Numerical study of the surface hardening effect on the deformation-induced roughening in titanium polycrystals

A three-dimensional numerical analysis is performed of the deformation-induced roughening in polycrystalline specimens with and without surface-hardened layers. Three-dimensional microstructure-based constitutive models are developed, using crystal plasticity, and employed in finite element calculations of uniaxial tension. Grain structure is shown to be responsible for free surface roughening under uniaxial loading. Microscale stresses acting normally to the free surface in the bulk of the material are associated with normal displacements. The surface-hardened layer moves the grain structure away from the free surface, smoothing out the microscale folds formed due to displacements of individual grains, while the mesoscale surface undulations remain clearly visible.

Predicting deformation-induced polymer–steel interface roughening and failure

Abstract A novel integrated framework is presented for the prediction of deformation-induced interface roughening and failure in polymer-coated steels. Crystal plasticity is employed to predict the change in steel surface roughness in-situ. The steel substrate is coated with a thin polymer layer and the polymer–steel interface is modeled using an exponential cohesive zone law. Uniaxial tensile simulations are performed and the results show that the predicted roughness increases with the applied deformation. The local changes in the steel surface profile result in initiation and growth of local interface failure. Furthermore, a compression simulation shows that the roughening rate of the steel is increased compared to tension, with an increase in the predicted interface damage as a result. The presented framework thus allows for a detailed numerical study of the initiation and growth of interface damage in polymer-coated steels during applied deformation. The incorporation of the crystal plasticity model to predict the changes in the steel surface profile complements the cumbersome measurements of detailed experimental displacement fields that accompany deformation-induced roughening and thus enables the analysis of deformation processes where measuring the steel surface profile is difficult if not impossible, e.g. industrial forming processes such as deep-drawing.