Experimental investigation of frictional characteristics of vibro-impact moling

In order to investigate the dynamical behaviour of a vibro-impact mechanism under the influence of friction, a new experimental vibro-impact moling machine has been designed and manufactured. The combination of resonance in an RLC circuit and a solenoid is known to create oscillatory motion of a metal bar within the solenoid. In the experimental rig, a bolt held in place by a block of aluminium obstructs this oscillatory motion of the metal bar. This results in impacts of the metal bar on the bolt. At the same time, the electromagnetic force created winthin the solenoid acts as a nonlinear spring. Hence, a vibro-impact mechanism has been created. The source of excitation is also part of the system characteristics as well. By varying the excitation volatge and initial gap between the metal bar and the bolt, a variety of system reponses are observed. The forward motion of the mole mimicking a soil penetration rate may be scrutinised by plotting time histories and phase planes. The design of the experimental rig is also detailed. A comparison is made between experimental results and numerical predictions. The equations of motion of the vibro-impact system were numerically integrated. These equations model the friction between the Teflon surfaces and the aluminium rails as well as the electromagnetic force generated by the solenoid. By tightening a bolt beneath the experimental mole, the frictional force is varied. The main result of this investigation is the influence of the extent of friction on the dynamical behaviour of the vibro-impact system.