Woodpecker
Coin tapping with a small hammer has been traditionally used to inspect honeycomb structures in aircraft. Personal skills that take a long time to acquire are indispensable to keep accurate detection for coin tapping method, which depends on the difference in tapping sound between normal and debonded area. Since coin tapping method depends on human senses, it makes difficult to conduct inspection in a noisy environment and it is almost impossible to sequentially obtain accuracy over a long period. In addition, the most fundamental issue in coin tapping method is that it is not quantitative.
Mitsui has developed the Woodpecker to solve these issues. Woodpecker has made it possible automatic tapping by adopting a solenoid driven hammer. It employs a CPU to comparatively evaluate the output of a force sensor attached to the hammer. The quantified results are indicated by LEDs and digital values. Its compact body and lightweight allows single handed operation, resulting in a handy detector with excellent cost performance.
Solenoid
Diagram
Impulse Wave on Debond
Features
- Quantitative inspection
- Compact and lightweight
- Easy to operate
Applications
- Detection of debonds/damages/moisture in honeycomb structures
- Detection of debonds in composite materials, tiles, clad steel, coatings, etc.
- Detection of debonds of joints in composite structures such as the helicopter blades
- Location of beams in walls
- Detection of boundaries between different materials
- Characteristics analysis of the sounding boards of musical instruments
- Detection of the water level in a container
- Detection of dryness (hardening) of bonding agents, etc.
- Comparison and evaluation of surface hardness (elasticity) of various plates
- Detection of the unfilled area within foamed sandwich panels
Advantages of Tapping Method
When inspecting honeycomb or similar structures, tapping method has advantages over methods using an ultrasonic in the following respects. The skin becomes debonded from the core and comes up loose, or it remains attached to the core even if debonded. The former debond can be detected with ultrasonic method, but the latter cannot, because the debonded skin and core would transmit the sound waves as if they are still boneded together.