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Numerous simplified numerical models have been established to optimize the ball burnishing of steel surfaces. Nevertheless, their conceptualization has not considered the tool–part interaction, leading to an unsatisfactory process parameterization. As a solution, a structured numerical simulation has been defined that reproduces this interaction by several friction coefficient approximations. This study provides the tribological process inputs (friction and initial surface conditions) to this model, adapting it to a pre-textured martensitic precipitation hardening stainless-steel. Results show the versatility of the model to reproduce the surface integrity alterations. Hence, this consistent model configuration can be postulated as an economical and efficient approach to tackle ball burnishing parameterization according to the applicability of the manufactured steel parts.

This paper deals with the improvement of the material surface state of friction stir welding paths modified in situ by plastic deformation through ball burnishing. The metallurgical and topological states of materials joined by this welding technique are typically detrimental to the ulterior performance of the workpiece, and it is believed that ball burnishing can improve these states to enhance functioning. This study is divided into two phases. The first one is experimental and consists of welding aluminum AA2024-T3 plates while combining different tool rotations and welding speeds. Then, the welding line is deformed locally by ball burnishing. The improvement of the topology and deep hardness distribution is measured and discussed, and the evolution of mechanical properties is assessed through tensile tests. The second phase is oriented towards estimating the residual stresses by combining two pre-existing models of friction stir welding and burnishing developed by the same authors using ANSYS®. Friction stir welding experimentation and measurements show a decrease in the values of all measured mechanical properties compared to the original material. The dominant factor affecting the properties and texture of the materials is the rotational speed of the tool, with the rupture point in the tensile test located in the distinct zone with the lowest value of microhardness on the advancing side. The higher the ratio of the rotational speed to the welding speed, the lower the roughness value. Finally, ball burnishing is proven to be an effective method to enhance the surface integrity of friction stir welded joints in light of the results, achieving a reduction of 11% to 36% in average roughness and an increase of about 22% in hardness profile, along with an integrated numerical model estimation of a remarkable effect on compressive residual stresses in-depth on the retreating side of the welded samples. However, in some tests, this treatment reduced some characteristics (yield stress and failure strain).

Ball burnishing is a superfinishing operation whose objective is the enhancement of surface integrity of previously machined surfaces, hence its appropriateness to complement chip removal processes at the end of a production line. As a complex process involving plastic deformation, friction and three-dimensional interaction between solids, numerical solutions and finite element models have typically included a considerable amount of simplifications that represent the process partially. The aim of this paper is to develop a 3D numerical finite element model of the ball burnishing process including in the target workpiece real surface integrity descriptors resulting from a ball-end milled AISI 1038 surface. Specifically, its periodical topological features are used to generate the surface geometry and the residual stress tensor measured on a real workpiece is embedded in the target surface. Secondly, different models varying the effect of the coefficient of friction and the direction of application of burnishing passes with regards to the original milling direction are calculated. Results show that the resulting topology and residual stresses are independent of the burnishing direction. However, it is evident that the model outputs are highly influenced by the value of the coefficient of friction. A value of 0.15 should be implemented in order to obtain representative results through finite element models.