Sonic drills systems are best described as resonant systems. It is one of several mechanical systems that are made to work on mechanical resonance. In the past, engineers were made to believe that mechanical resonance is one phenomenon they need to veer away from.
Despite that, resonant systems are known to offer 2 unique advantages. First one, it can transfer energy without having to expend much power in itself in the mechanical system. This significantly helps in paving the way for higher amplitudes.
These attributes of the sonic drill allow it to transfer the mechanical energy it generates and has it as input at the top of the drill string which is the sonic drill head. This is usually situated above the earth’s surface. The mechanical energy is then successfully transmitted to the drill bit which will perform the drilling part.
A resonant system is best described as being on resonance if the input power is transferred directly to the damping of the system. In the meantime, it expends little to no energy in the actual mechanical system. This is likely to occur at specific frequencies where the system’s capability to main kinetic energy is directly proportional to its ability to keep in potential energy.
While the system is oscillating, the kinetic and potential energies are relayed back and forth between these 2 types of energies. The resonant condition makes it possible for additional energy to be carried through the system without being taken in as either kinetic or potential energy while the system’s mechanical oscillations are ongoing.
While the system’s mechanical resonance amplitude is growing, the system’s total stored energy, which is either kinetic or potential energy, increases. In addition to this, the amount of energy that is stored as either kinetic or potential power in the system will remain constant.
If the system will operate below mechanical resonance, more energy should be added to the system to all the potential energy to continuously charge. This is because the system will store greater amounts of potential energy as opposed to the kinetic energy in given oscillation amplitude.
Putting it differently, the oscillator will need to put on additional energy. This should help in driving the system that has incessantly charged the system’s potential energy because there is no way it can store potential energy, even though it remains in its kinetic energy form. If the kinetic and potential energies do not match, the oscillator will need to continually put more energy into the system. This should help in sustaining the desired oscillatory amplitude.
Similarly, frequencies that are above mechanical resonance, there is a need to input more energy into the system because the stored potential energy will not be enough or become enough to recharge the kinetic energy needed in oscillating the system.
In a mechanical resonance environment, the system is likely to charge up reaching the maximum energy stored as kinetic or potential. This way it will allow the energy that is flowing into the system to pass through and get absorbed by the damper.
If the damper is having a hard time absorbing those energies, then it renders the oscillation amplitude to grow continuously until such time that the system fails.
Sonic drilling failures have become as common as putting too much stress on the joints that bind the pipe drill as one as well as stressing out the sonic drill driver. This is likely to occur when excessive acceleration is applied at the drill head. Nonetheless, the surrounding resonant condition may also work to the advantage of the operator. They refer to as a “lock-in” frequency.
By scaling up the driving frequency, operators can handle the sonic drill until it reaches that point when the system would start increasing the frequency on its own. This is brought about by the reduced energy required to operate under mechanical resonance.