Experimental and Theoretical Analysis of the Impact with Solid and Flexible Surfaces
Type of DegreePhD Dissertation
MetadataShow full item record
Impact plays an important role in many engineering applications, mechanical systems, and different areas such as robotics, machine design, etc. It is a complex phenomenon that occurs when two or more bodies collide. In the textile industry, weaving machines with projectile and shuttle filling insertion systems provide good examples of collision during fabric manufacturing. This work investigates the normal and oblique impact on flexible and rigid surfaces through experimental and analytical methods. Three different cases, including, the impact of a hollow sphere on a flexible flat, the impact of a solid rubber sphere on a wooden flat, and the impact of a rod on a deformable flat have been studied. The experiments are performed using either a high speed or an infrared camera depending on the study. The high speed camera provides the opportunity to study the motion during the impact due to better frequency. The motions of the spheres have been captured at 10,000 frames per second. The image processing technique with a digital image correlation method has been developed to measure the motion of the spheres. A speckle pattern study has been done to find the optimum pattern for the image processing method. The Hough transform method has been used to track the position of the centroid of the spheres. The linear and angular motion of the spheres have been analyzed before, during, and after the impact. The oblique impact of a hollow sphere on a flexible surface has been modeled with a spring-damper system. The impact has been divided into two sub-phases: compression and restitution. The contact force expression has been determined for the compression and the restitution phases using the experimental data from the normal impact experiments. Experiments have been done for a wide range of impact angles and initial velocities. The coefficient of restitution and effective coefficient of friction have been analyzed experimentally. The simulation and experimental results have been compared, and the model is verified for the oblique impacts. The oblique impact of a solid rubber sphere on a wooden flat has been studied. The wooden flat is considered to be rigid. The digital image processing method has been used to measure the linear and angular velocities of the sphere during the impact. A theoretical model has been proposed for both the normal and tangential directions. The normal force has been divided into two sub-phases: compression and restitution. The tangential force is considered to be the friction force and has been divided into three sub-phases during the impact: sliding, sticking and post-sliding. The model has been compared and verified with the experiments. An experimental study has been done for the impact of a rod on a deformable flat. The motion of the rod before and after the impact has been accurately captured with a 3D infrared camera. The results in terms of rebound angular velocity, coefficient of restitution, and permanent deformation on the flat have been compared for different impact angles. An optical profilometer has been used to measure the permanent deformation after the impact.