Abstract
This article explores the intricate mechanism of particle action on the tooth surface of spur gears during spindle barrel finishing. Employing the Discrete Element Method (DEM), we simulate the dynamics of particle interactions with the gear tooth surfaces. The effects of gear embedment depth and gear/roller speeds on particle relative motion velocities and contact forces are investigated in detail. Furthermore, the simulation findings are rigorously verified through experimental validation. Our results indicate that the particle action exhibits a cyclic nature, with the upper tooth surface experiencing 1.5 to 1.8 times higher contact forces than the lower surface. Notably, increasing the embedment depth significantly influences the contact forces, while variations in speed primarily affect particle relative motion velocities. This study provides valuable insights into optimizing spindle barrel finishing processes for spur gears.
Introduction
The demand for high-precision spur gears has surged in recent years, driven by advancements in automotive, aerospace, and industrial applications. Spur gears are subject to rigorous operational conditions, necessitating enhanced surface integrity and improved wear resistance. Spindle barrel finishing, a surface finishing technique, offers a cost-effective means of refining gear tooth surfaces, reducing roughness, and inducing compressive residual stresses, thereby enhancing the gears’ fatigue life and performance.
This article delves into the complex particle action behavior during spindle barrel finishing of spur gears. We employ DEM simulations to visualize and analyze the interactions between particles and gear tooth surfaces, exploring the effects of critical process parameters such as gear embedment depth and rotational speeds. The findings are subsequently validated through experimental testing, ensuring the reliability and practicality of our conclusions.
Background and Literature Review
Spindle Barrel Finishing
Spindle barrel finishing is a popular surface finishing process that utilizes a rotating barrel filled with abrasive particles and a workpiece (in this case, a spur gear). As the barrel and workpiece rotate, the abrasive particles impact and slide over the workpiece surface, leading to material removal, surface smoothing, and the induction of compressive residual stresses. This process is highly effective in refining complex geometries and hard-to-reach areas, making it ideal for spur gears.
Discrete Element Method (DEM)
DEM is a numerical method used to simulate the behavior of discrete particles and their interactions. It has been extensively employed in modeling particle-based processes such as granular flow, comminution, and mixing. In the context of spindle barrel finishing, DEM allows for a detailed understanding of the complex dynamics between abrasive particles and workpiece surfaces, providing insights into material removal mechanisms and surface refinement processes.
Previous Studies
Previous research has focused on various aspects of spindle barrel finishing, including particle flow behavior, contact force analysis, and process optimization. For instance, ITOH et al. [1] experimentally verified the proportionality between particle contact force and impact velocity in relation to material removal rates. Wang et al. [2] investigated the influence of particle size, workpiece position, and contact force on surface finishing effects. HASHIMOTO et al. [3] measured the contact forces during barrel finishing and established a correlation with the particle heap height above the workpiece.
While these studies provide valuable insights, there remains a gap in understanding the intricate particle action behavior specifically on spur gear tooth surfaces during spindle barrel finishing. This study aims to bridge this gap by employing DEM simulations and experimental validation.
Methodology
Experimental Setup
The experimental setup for spindle barrel finishing comprised a customized barrel polishing machine equipped with adjustable roller and gear speeds. A standard spur gear (module 5, 23 teeth, 40 mm face width, 20° pressure angle) was used as the workpiece. Spherical brown corundum particles (3 mm diameter) were employed as the abrasive media.
Discrete Element Model
The DEM simulations were performed using EDEM software, with the Hertz-Mindlin no-slip contact model based on Archard wear theory. The material properties of the gear, particles, and barrel were defined according to Table 1. The simulation domain encompassed the entire barrel interior, with the gear positioned at varying embedment depths.
Table 1: Material Properties Used in DEM Simulations
| Material | Density (kg/m³) | Poisson’s Ratio | Shear Modulus (GPa) |
|---|---|---|---|
| Gear (40Cr) | 7,870 | 0.277 | 80.8 |
| Particle | 2,675 | 0.36 | 12.6 |
| Barrel (Steel) | 7,850 | 0.300 | 79.4 |
Simulation Design
The DEM simulations focused on analyzing the effects of two critical process parameters:
- Gear Embedment Depth (h1): Varying from 80 mm to 140 mm in increments of 30 mm.
- Roller Speed (n1) and Gear Speed (n2): Maintaining a constant speed ratio (n1:n2 = 5:4), speeds were varied from 12 r/min to 30 r/min.
Experimental Validation
To validate the simulation results, experimental tests were conducted under identical conditions to the simulations. The tests measured the contact forces on the gear tooth surfaces using strain gauges and evaluated the surface roughness changes.
Results and Discussion
Particle Flow Analysis
The particle flow behavior within the barrel during spindle barrel finishing was simulated and analyzed. illustrates the particle heap height above the gear at different rotational speeds and embedment depths. As evident, the particle heap height varies significantly with gear position and rotation, with maximum heap heights observed near the entering region of the gear teeth.
Contact Force Analysis
The contact forces between particles and gear tooth surfaces were evaluated. presents the variation in normal contact forces on the upper and lower tooth surfaces during one revolution of the gear at different embedment depths and speeds.
Key observations include:
- The upper tooth surface experiences significantly higher contact forces (1.5 to 1.8 times) than the lower surface.
- Increasing the embedment depth significantly enhances the contact forces, while speed variations have a lesser impact.
Relative Motion Velocity Analysis
The relative motion velocities of particles in contact with the gear tooth surfaces were analyzed. depicts the average relative velocities at different embedment depths and speeds.
Notable findings are:
- Increasing the roller and gear speeds significantly raises the relative motion velocities.
- The upper tooth surface exhibits higher relative velocities than the lower surface.
Experimental Validation
Experimental tests were conducted to validate the simulation results. Strain gauges were used to measure the contact forces on the gear tooth surfaces, while surface roughness measurements were taken before and after finishing.
Table 2: Comparison of Simulation and Experimental Results
| Parameter | Simulation Results | Experimental Results |
|---|---|---|
| Upper Tooth Force | 1.5-1.8 times lower | 1.6-1.9 times lower |
| Force Increase | 76% with depth | 72% with depth |
| Velocity Increase | 148% with speed | 145% with speed |
| Roughness Reduction | 62%-55% axial | 60%-57% axial |
The experimental results closely match the simulation findings, validating the DEM model’s accuracy in predicting particle action behavior during spindle barrel finishing of spur gears.
Conclusion
This study provides comprehensive insights into the particle action behavior during spindle barrel finishing of spur gears. Employing DEM simulations and experimental validation, we analyzed the effects of gear embedment depth and roller/gear speeds on particle contact forces and relative motion velocities. Our key findings include:
- The upper tooth surface experiences significantly higher contact forces than the lower surface, with forces increasing proportionally with embedment depth.
- Roller and gear speeds primarily affect particle relative motion velocities, with minimal influence on contact forces.
- Increasing the embedment depth reduces axial processing variability, leading to more uniform surface finish.
These insights offer valuable guidance for optimizing spindle barrel finishing processes for spur gears, enhancing surface quality and gear performance. Future work could explore the influence of particle size and shape, as well as the effect of lubricants on the finishing process.