Phased array ultrasonic testing (PAUT) techniques are widely used for the non-destructive testing (NDT) of austenitic welds to find defects like cracks. However, the propagation of ultrasound waves through the austenitic material is intricate due to its inhomogeneous and anisotropic nature. Such a characteristic leads beam path distorted which causes the signal to be misinterpreted. By employing a reference block which is cutout from the mockup of which the structure is a dissimilar metal weld (DMW), a new method of PAUT named as Referencing Delay Law Technique (RDLT) is introduced. With the RDLT, full matrix capture (FMC) was used for data acquisition. To reconstruct the images, total focusing method (TFM) was used. After the focal laws were calculated, PAUT was then performed. As a result, the flaws are more precisely positioned with significantly increased signal-to-noise ratio (SNR).
Eddy Current Testing has been mainly used to determine defects of conductive materials and wall thicknesses in heavy industries such as construction or aerospace. Recently, high frequency Eddy Current imaging technology was developed. This enables the acquirement of information of different depth level in conductive thin-film structures by realizing proper standard penetration depth. In this paper, we summarize the state of the art applications focusing on PV industry and extend the analysis implementing achievements by applying spatially resolved Eddy Current Testing. The specific state of frequency and complex phase angle rotation demonstrates diverse defects from front to back side of silicon solar cells and characterizes homogeneity of sheet resistance in Transparent Conductive Oxide (TCO) layers. In order to verify technical feasibility, measurement results from the Multi Parameter Eddy Current Scanner, MPECS are compared to the results from Electroluminescence.
The magnetic Barkhausen Noise technique is a well suited method for the characterization of
ferromagnetic materials. The Barkhausen effect results in an interaction between the magnetic
structure and the microstructure of materials, and is sensitive to the stresses and microstructure
related mechanical properties. Barkhausen noise is a complex signal that provides a large amount of
information, for example frequency spectrum, amplitude, RMS value, dependence of magnetic field
strength, magnetization frequency and fractal behavior. Although this technique has a lot potentials,
it is not commonly used in nondestructive material testing. Large sensors and complex calibration
procedures made the method impractical for many applications. However, research has progressed in
recent years; new sensor designs were developed and evaluated, new algorithms to simplify the
calibration and measurement procedures were developed as well as analysis of additional material
properties have been introduced.
New processes introduced by nano science into much more conventional industrial applications require fast, robust and
economical reasonable inspection methods for process control and quality assurance. Developed for semiconductor
industries the methods available for thin film characterization and quality control are often complex and require highly
skilled operation personnel. This paper presents a new concept based on high frequency eddy current spectroscopy that
allows reliable and robust thickness measurements of thin conducting films on silicon or insulation substrates with a
thickness resolution of about 2.5 nm. The transmission mode sensor configuration is a more practical method for inlinemonitoring
of thin film characterization. Due to the insensitivity of the transmission mode to dislocations or slight tilting of the sample the high frequency eddy current method is a practical method for thin film characterization in the industrial environment.
For near surface characterization a new high frequency eddy current device was been developed. By using a
measurement frequency up to 100 MHz information of near surface areas can be acquired. Depending on the investigated
material high resolution depth profiles can be derived. The obtained data with the new device were compared to those
obtained with a high precision impedance analyser. It could be demonstrated that the new device measures the eddy
current conductivity signal in the high frequencies much better than the impedance analyser. By sweeping the frequency
from 100 kHz up to 100 MHz the technique delivers a depth profile of the electrical conductivity of the material. This
kind of high frequency eddy current technique can be used for quality assurance, surface contamination control or near
surface material characterization e.g. microstructure and cold work influences. It can be a powerful tool to obtain
information for process control or a good / bad decision in mass production processes like for example rolling, coating,
and surface treatments. The big advantage of the high frequency eddy current method is that it is fast und precise. This
paper presents results with a new developed prototype
Eddy-Current-Device for measurement frequencies up to 100
MHz which is first time suitable in rough industrial environment and makes expensive lab network analysers unnecessary
for this kind of investigations.