Comparision of costs between Resonant Testing Machine and Servohydraulic testing machine
The following comparision shows the running costs of two testing machines suitable for dynamic loads in the middle to high frequency ranges. A RUMUL high frequency resonant testing machine TESTRONIC 100 kN and a modern servohydraulic machine are compared. The key features are delivered from a large testing laboratory with many years of experience, and all kinds of testing machines. Two characteristic features mark the comparison; to be precise, the high frequency and the low power consumption.
A) The resonant testing machine is designed as a mechanical oscillating system and consists of masses and springs. Also the specimen with its elasticity is part of this system. The natural frequency is excited by an electromagnet. Typical frequencies for such machines lie within the range of 50-250 Hertz and the needed energy consumption is approximately 0.5 kW.
B) The servohydraulic testing machine loads the specimen with a hydraulic actuator which operates in a servo-loop. For frequencies in the range of 50 Hertz very efficient equipment has to be used. The testing load for each cycle has to be built-up by oil pressure, which means that a necessary energy is needed for each cycle. Practically all the energy is transformed into heat and has to be carried off by an additional cooling system.
The comparison has been simplified in serveral points without falsifying the essential. The amortisation has been distributed regularly to 8 years. Takeing into consideration the reduction of interest for the decrease in depreciation of the original investment, the interest of 12 % has been divided to 6 %. This means that for the first years of the amortization period the interest is too little but this will be compensated during the last years. The calculation does not consider engineering- and space-costs.