Wall Forces, Bulk Flow and Impact Speeds in a Vibratory Finisher: Modeling and Force Measurements

Vibratory finishing (VF) is a mass finishing process that employs loose abrasives inside a vibrating container and, although widely used, its design is still mostly based on experience due to the complex behavior of vibrating granular media. In this work, experimental and numerical methods were employed to investigate the relationship between the container motion and the granular media behavior inside a commercial VF tub. The objectives were to understand the influence of different process parameters on the media motion, to reveal the mechanisms behind these influences, and to assess the accuracy of discrete element methods (DEM) predictions of the wall-media interactions. A parametric study was performed using DEM to understand how parameters such as amplitude and frequency of vibration influence the particle behavior in terms of media bulk flow (responsible for moving workpieces during VF processes) and local impact velocities between particles (which do work on the workpiece surface). This study revealed that local impact speeds varied more with changes in amplitude than in frequency, and that they were determined by the work done by the walls on the media per vibration cycle. In contrast, the bulk flow rate depended mostly on the vibration frequency rather than on amplitudes and it was determined by the direction of the wall-media shear in regions of greater particle density. Given the importance of wall forces in explaining the media behavior, a method for measuring wall-media contact forces was developed where a force sensor was embedded in the vibrating walls. Measurements revealed that wall forces were determined by the granular bed viscous resistance to deformation rate and that it increased with both media pressure and wall velocities. With this method, the impulse and work done by the walls on the media were also measured. The results were compared to DEM simulations and it was found that although DEM could predict the overall trends of wall forces and impulse with varying amounts of media and tub frequency, some differences from experiments, such as consistently shorter and more random collisions in DEM, persisted throughout all simulations.

Department dc:contributor.department

Mechanical and Industrial Engineering

Year dc:date.issued

2019

Author dc:creator

• da Silva Maciel, Lucas

Advisor dc:contributor.advisor

• Spelt, Jan K

• Discrete Element Methods
• Granular Flows
• Polishing
• Vibratory Finishing

Handle dc:identifier.uri

http://hdl.handle.net/1807/97360

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/97360