Structures testing and evaluation facilities catalog
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Residual stress measurements<br />
(hole drilling method)<br />
The strength behaviour of components is influenced by residual stresses<br />
existing in these components without showing any visible signs.<br />
The most widely used practical technique for determining residual<br />
stresses is the hole-drilling strain gauge method described in ASTM<br />
St<strong>and</strong>ard E837. With this method, a specially configured strain gauge<br />
rosette is bonded to the surface of the test object. A small shallow hole<br />
is introduced into the structure, through the center of the gauge, with a<br />
precision drilling apparatus. Strains in the immediate vicinity of the hole<br />
are measured, <strong>and</strong> the relaxed residual stresses are computed from<br />
these measurements.<br />
Residual stress measurement<br />
Courtesy: Airbus Defence & Space Netherl<strong>and</strong>s<br />
System:<br />
• Vishay RS 200<br />
Fibre Optic Sensors<br />
Fibre bragg gratings (FBGs) appear to offer the best prospect for large<br />
scale commercial exploitation of fibre optic sensor (FOS) technology.<br />
Main applications:<br />
Structural Health Monitoring (SHM)/ damage detection<br />
• environmental, accidental<br />
• disbond/debond detection<br />
• impact detection<br />
• internal crack detection<br />
Deminsys system<br />
Monitoring of physical parameters<br />
• like strain/temperature/pressure/impact/vibration/flow; but also<br />
chemical parameters (gasses, humidity, corrosion,...)<br />
Process monitoring of composite materials<br />
• state of cure during manufacturing<br />
• internal strain after manufacturing<br />
General attributes<br />
• High spatial resolution, high sensitivity, low signal loss<br />
• Small diameter, light weight, flexible<br />
• Immunity against, i.e. applicable in<br />
--<br />
Electro-magnetic fields, high voltage, lightning<br />
--<br />
Explosive or chemically aggressive + corrosive media<br />
--<br />
High <strong>and</strong> low temperatures<br />
• Read-out unit galvanically separated from object<br />
• Ability to measure different parameters such as strain, temperature,<br />
pressure, moisture, chemical compounds<br />
Demonstration of the feasibility of<br />
specific SHM systems on a representative<br />
structure (Glare fuselage panel with<br />
bonded <strong>and</strong> riveted repair patches)<br />
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