Ultrasonic Technique & Equipment for Residual Stress Measurement
An Ultrasonic Computerized Complex (UCC) for residual stress measurement was developed recently in a joint project between Integrity Testing Laboratory Inc. and Ukrainian scientists. The UCC includes a measurement unit with supporting software and a laptop with an advanced database and an Expert System for analysis of the influence of residual stresses on the fatigue life of welded elements. The Complex allows one to determine uni- and biiaxial applied and residual stresses for a wide range of materials and structures. In addition, the developed Expert System (ES) can be used for calculation of the effect of measured residual stresses on the fatigue life of structural elements, depending on the mechanical properties of the materials used, type of structural elements and parameters of cyclic loading.
The supporting software allows one to control the measurement process, to store the ultrasonic measurement data, to calculate and draw the distribution of residual stresses. The software allows the use of the designed method and equipment with standard PC’s.
Using the ES, it is possible to assess, through calculations, the influence of the residual stresses and their redistribution under the effect of various improvement treatments and cyclic loading on the service life of structural components without having to perform time- and labor-consuming fatigue tests. The program package enables one to calculate the fatigue life of structural components after application of heat-treatment, vibration treatment, overloading, UP and other improvement treatments.
The major components of the system are:
1. The main measurement unit with built-in microprocessor
2. A set of two gauges for measurement of the velocities of ultrasonic waves thorough the investigated material
3. Ultrasonic transducer holder
4. Portable oscilloscope (optional) for visualization of the ultrasonic signals
5. Laptop computer (optional) with an advanced database and an Expert System for analysis of the influence of residual stresses on the fatigue life of welded elements – Software UltraMARS (a different computer model will be supplied).
Main Technical Parameters of the Measurement Unit
The developed equipment allows one to determine the magnitudes and signs of uni- and biaxial residual and applied stresses for a wide range of materials as well as stress, strain and force in bolts (pins). Quartz plates measuring from 3×3 mm to 10×10 mm in cross-section are used as ultrasonic transducers. These gauges are attached to the object of investigation by special clamping straps and/or electromagnets.
- stress can be measured in materials with thickness 2 – 150 mm
- error of stress determination (from external load) 5 – 10 MPa
- error of residual stress determination 10%
- stress, strain and force measurement in bolts (pins) 25-1000 mm long
- power requirement 220 V/50Hz or 115v/60Hz (as requested)
- independent power supply (accumulator battery 12 V – optional)
- overall dimensions of measurement device 300x200x150 mm
- weight of unit with transducers 6 kg
