Investigations of ultrasonic frequency effects on surface deformation in rotary ultrasonic roller burnishing Ti-6Al-4V

The objective of this paper is to present a comprehensive study of the effects of ball burnishing on the low cycle fatigue endurance of cylindrical specimens subjected to alternative bending stress, by constructing fatigue S-N curves to evaluate the impact of the process on the general fatigue behavior of AISI 1038. The specimens were burnished through five different force-number of passes couples, displacing the as-machined-material S-N curve towards higher lifespans as the degree of cold work is increased, either by effect of a higher force and more burnishing passes. The derived surface hardening effect also proved to be correlated analytically with the fatigue lifespan increase at all tested maximum-stress levels, as prove the correlation of the parameters that represent the potential equation associated to the Wohler model with the hardening effect. It is concluded that the process performed with 120 N and 7 passes results in the most favorable results, represented by a 41% increase of hardness and a 77% increase in the lifespan in the best of cases.

Hardening effect and fatigue behavior enhancement through ball burnishing on AISI 1038

Metal additive manufacturing (AM) has been attracting attention as a new manufacturing method, but a surface finishing process is usually needed to improve the surface quality. As a new surface finishing process, ultrasonic vibration-assisted burnishing (UVAB) is promising. In this study, UVAB was performed on an additive-manufactured AlSi10 Mg workpiece to improve its surface/subsurface integrity. The effects of ultrasonic vibration (UV) and lateral tool pass width on the burnishing performance were investigated. It was observed that the surface roughness, filling ratio, and hardness of the surface layer were simultaneously improved after burnishing. This study shows the effectiveness of applying UVAB to improve the surface quality of additive-manufactured products for various industrial uses.

Improving the Surface Integrity of Additive-Manufactured Metal Parts by Ultrasonic Vibration-Assisted Burnishing

Additive manufactured parts often require post-processing to obtain the desired surface finish. In this sense, this work investigates the ball burnishing process’s applicability as a finishing method for fused filament fabricated (FFF) parts. Ball burnishing is a mechanical finishing procedure based on the plastic deformation of the treated surface that could provide significant advantages, as it is non-abrasive and does not chemically interact with the model material. Following Taguchi’s design methodology, optimal values of four burnishing parameters have been identified, and significant improvements in surface quality have been quantitatively and qualitatively proven. Mechanical performance under tensile and flexural loading, impact testing, and bending fatigue of ball-burnished samples has been compared to pristine values. Besides the enhanced surface quality of the samples, a notable finding of the study is a minimum twofold increase in the fatigue life of ball-burnished samples, as well as a higher impact energy absorption. Accordingly, this research provides experimental evidence to set ball burnishing as a novel post-processing technique for FFF parts.

On the effect upon the surface finish and mechanical performance of ball burnishing process on fused filament fabricated parts

Ultrasonic vibration cutting has been proved to be an effective cutting technology for its excellent cutting performance and has been widely applied in turning and drilling process. However, this k...

Study of milling force variation in ultrasonic vibration-assisted end milling

Burnishing is a mechanical finishing operation performed on workpieces to enhance their surface quality through plastic deformation. One of the main issues to understand the overall process is the behavior of the elastoplastic deformations caused by the burnishing ball on the workpiece. The first burnishing passes performed on the workpiece surface lead to its plastic strain and self-hardening, thus influencing the results of consecutive passes. Some references have studied the phenomenon of indentation, finding that there is a certain self-hardening coefficient threshold which allows to predict the presence of pile-ups at the edges of the indentation path. Nevertheless, burnishing is not a single-pass operation. On the contrary, burnishing a whole surface requires successive adjacent and/or overlapping passes, i.e., parallel passes separated consecutively a certain lateral pass width. No reference has been found in the literature defining the adequate values of the lateral pass width with regards to the pile-up effect to enhance the final topology of the burnished surface. This paper explores that influence by studying the presence of the pile-up effect after burnishing a single or several overlapping passes on two materials (aluminum and steel), by characterizing the topology of the generated path. Afterwards, two adjacent passes are performed, varying the lateral pass width, to compare the final surface roughness derived from each operation. An optimum value for the lateral pass width was found, to improve the final roughness after burnishing in different conditions and to increase the productivity of the process.

B. Gomis de la Calle

Papers

Experimental study of lateral pass width in conventional and vibrations-assisted ball burnishing