Fatigue damage to mechanical element measuring appts. - assesses change of resonance frequency and damping of tested structure and compares results with those of structure unused

摘要

A beam (1) is fixed to a support (2) at a vibration node. A low frequency generator (3) is connected to the beam via an amplifier (4) and electrode (5) placed close to one end. A second electrode, (6) which is placed close to the other end, provides an output signal via an amplifier (7). A metallic cap which is grounded avoids direct reception of the radiation from the transmitting electrode. At resonance the output voltage is examined on an oscilloscope to determine the damping factor for comparison with that from an unused beam. To determine the damping of the vibrations induced, the variations in voltage from output (8) can be recorded. The vibration generator (3) is then stopped and the logarithmic decay is measured. The damping factor can be extracted from the decay.