Analysis of grain kernel rebound motion

Grain rebound movement in a combine cleaning shoe is a major factor causing grain loss during harvesting. Grain loss occurs if a kernel rebounds on chaffer vanes and fails within grain dwell time to find an opening to pass through the chaffer. Grain rebound motion can be described by two parameters: the resultant restitution coefficient and rebound direction. Since the analysis of resultant restitution coefficient and rebound direction is the same for a kernel rebounding on one chaffer vane or on a series of chaffer vanes, therefore, in this study grain rebound movement on combine chaffer vanes is simplified by releasing a kernel above a single steel plate whose angle can be changed to simulate the chaffer vane angle.;The analysis of the mechanism of kernel impact showed that due to the irregular shape of the grain kernel, the resultant restitution coefficient was not a constant but a variable associated with materials, biologic structure, impact velocity, and kernel orientation.;In this study, the factors affecting the resultant restitution coefficient and rebound direction such as the kernel release height, grain moisture content, size, type and impact plate angle were studied. The grain type, impact plate angle and kernel release height were the three significant factors affecting the resultant restitution coefficient. The grain resultant restitution coefficient increased as the increase of impact plate angle. An increase of the kernel release height resulted in an increase in kernel striking velocity which reduced the value of the resultant restitution coefficient. Different grain types had different resultant restitution coefficient. Soybeans and cheat presented the largest resultant restitution coefficients, goatgrass the smallest. Among those factors, only the impact plate angle had a significant effect on rebound angles ;The stroboscopic photography equipment was designed to take photos of kernel fall and rebound motion trajectories. A mirror was used to obtain an additional view of kernel motion trajectory, termed the virtual kernel image. Image processing techniques were applied to digitize both the real and virtual kernel motion trajectories. An image analysis method was developed to obtain kernel motion coordinates in thee dimensions in terms of the kernel image coordinates in the photos. In turn, the kernel impact velocity, rebound velocity, resultant restitution coefficient, and rebound direction could be determined.