How to Analyse C-scan Mapping?
C-scan mapping is the best ultrasonic testing solution to rapidly control large surfaces!
Ultrasonic NDT technology can acoustically see through material create complete inspection maps called C-scan mapping. Supported by comprehensive colour palettes, these volumetric integrity reports are as easy to interpret as traditional X-Ray.
Basics of C-scan mapping
The latest ultrasonic flaw detectors nowadays record complete A-scan information and can create a two-dimensional C-scan mapping. Associated to a GATE within the A-scan, each pixel of a C-scan mapping tie-in for depth (time-of-flight) or amplitude of the echoes crossing that gate. Using vivid colour palettes to represent % or mm values, it is then possible to analyse the complete volumetric integrity of the part rapidly.
The Linear Array technologie is particularly efficient to create high-resolution C-scan mapping and inspect small to large surface of composite parts or to assess the level of corrosion on a metallic sheet for instance.
Amplitude or Depth Method ?
As we can see below, the depth and amplitude-based C-Scan may reveal complementary information and both mapping methods have advantages and must be well understood to support the NDT professional in his task properly.
Amplitude C-scan is generally used to monitor the behaviour of a specific section of the part. Per example, monitoring the backwall (BW) amplitude can give information on the presence of small mid-wall porosities (BW drops). On the other hand, monitoring a specific composite section can help to spot weak bonding (BW peaks) from the glueing process between two composite layers.
Depth C-scan is generally used to monitor the thickness of a part by giving information on the remaining wall thickness or by precisely positioning an anomaly like a disbond, a large porosity or a flaw within the material.
- Within a single scan (data set), both amplitude and depth C-scan mapping information can be generated.
- This saves significant scanning time for the end-user as there is no need to scan twice the part to make a complete analysis using both modes.
Data Analysis Step
Once the acquisition is made, and the proper analysis mode has been chosen, the data analysis step is often considered laborious because of the interpretation of the data and report writing. Fortunately, there are solutions like the Sonatest UTmap software that are designed and developed to simplify the examination process.
Data alignment and overlapping
A C-scan mapping is generally made of many strips. Before to proceed to data analysis, it is important to make sure all the strips are properly aligned with the part origin and the overlap between strips has been respected. In real life, the position of each strip has to be fine-tuned to give optimal results. For this, UTmap offers the possibility to create a T-scan (for Tiled Scan) where every strip can be individually rotated, translated and overlapped one on top of the others. Once assembled, the T-Scan represents a meaningful image for analysis and reporting.
To improve data alignment precision, UTmap also offers the unique possibility to import 2D CAD drawings of the part (or a simple picture) in the T-scan workspace. The C-scan strips can then be precisely applied with opacity option on the CAD overlay to create even more comprehensive inspection reports.
Software Gain and Re-Gating Adjustment
Compared to other software solutions, UTmap allows post-acquisition C-scan re-gating and sensitivity adjustment of each strip of data. This granular software adjustment feature is especially useful to deal with thickness changes and more importantly when dealing with amplitude assessment-based C-scan mapping. Indeed, this mode is more sensible to coupling or pressure variations often that is unfortunately difficult to avoid during the acquisition step.
Real-Time Automatic Measurements
When all the strips are aligned, and the gates and gain sensitivity have been harmonised, the real-time automatic annotation feature is a key tool to expedite the analysis and reporting process. When activated, the annotation box automatically contours with a specific colour code discontinuity based on a selectable amplitude criteria, depth criteria or both at the same time. These measurements are performed in real-time wherever the box is positioned in the T-scan.
The benefits of this automatic annotation box are dimensions precision improvement, repeatability as well a fast and reliable process.
C-scan Mapping Reporting
At one glance, a report summarises the inspection. Thus, the defect (or the absence of defects) of the parts must be highlighted with images as well as the basic inspection information like ultrasound device, probe, materials and thickness. Most of the software nowadays offer the automated report in a complete, light and shareable PDF format. This report with image configuration, annotation measurements saves time and increase overall productivity.
For the more advanced users, the UTmap software offers the possibility to export the results of the C-scan mapping information into a CSV format. This is especially useful for end-users who want to analyse in depth with advanced algorithms a high-resolution C-scan corrosion mapping for instance.
- Learn more about the concept of ultrasonic NDT Linear Scanning
- Learn more about an optimised linear scanning workflow
- Learn more about RSflite and UTmap composite solution
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