There are numerous fields of application for non-destructive testing methods in the automotive industry. In addition to quality control related to safety standards, prototypes can also be inspected before they go into mass production.
Non-destructive testing also provides a more sustainable way to use raw materials, which is becoming increasingly important in today’s world. Because components are not changed in the process by non-destructive testing methods, the results of an inspection can be significantly more reliable. Common methods include visual inspection, radiography, industrial CT, eddy current and ultrasonic inspection. For instance, industrial computed tomography can be used to create three-dimensional models of components and assemblies by using reverse engineering (reverse engineering of complex components with CT | Microvista) to improve or develop new products.
Visual Inspection
Visual inspection is a non-destructive testing method in which the part to be inspected is visually examined to identify surface defects such as cracks, scratches, holes or wear marks. This inspection method does not require any special equipment or tools and only needs sufficient illumination and visibility of the part.
Visual inspection is used in many industries, such as automotive, aerospace, electronics and construction, to ensure that parts meet requirements. Therefore, special tools such as magnifying glasses, mirrors or endoscopes are used to examine areas that are difficult to access.
Radiographic Testing
Industrial radiographic testing uses X‑rays to examine the inside of materials and components. In this process, the X‑rays are emitted from an X‑ray source and passed through the material or component. The absorption of the X‑rays by the material creates a two-dimensional shadow image on a detector, which can then be analysed by a qualified inspector.
Industrial CT
With this non-destructive testing method, it is possible to create three-dimensional images of the interior of an object. The object is penetrated by an X‑ray source and the attenuation of the radiation is recorded by a detector. In contrast to simple radiographic testing, a high-resolution 3D representation of the object can be created by combining the data from different beam directions.
Industrial CT is used across industries such as automotive to inspect components and materials for internal defects such as voids, cracks, inclusions or material irregularities. In the process, CT testing can also make details visible in the micrometre range that are not visible with other testing methods.
CAD target/actual comparison
A CAD target/actual comparison may be necessary, for example, if a production batch is reordered after a longer period of time. It is necessary to check whether there are any discrepancies between the previous batch and the current CAD. Microvista uses state-of-the-art computer tomography to ensure that the new production batch is not lost.
Without the use of non-destructive testing, there would normally is a risk that unwanted deviations and other defects would only be detected during final assembly or even during test runs. In such a case, the entire batch would not be usable or would have to be tested at random.
Assembly and joint control
When a vehicle is not functional after it has been assembled, the cause must be found as quickly as possible. However, disassembly is not always allowed or is too time-consuming. Industrial computed tomography can check the vehicle for completeness or components for correct seating and joining. In this way, blocked batches can be released again quickly and cost-effectively.
Eddy Current Testing
This non-destructive testing method is used to examine electrically conductive materials. An electromagnetic alternating field is generated that causes eddy currents in the material. The reaction of these currents is measured to gain information about the material. Eddy current testing is often used on main cylinders, bearing rings and pistons for crack detection and hardness testing. Here, modern eddy current systems have the advantage of a high sampling frequency, which makes it possible to test even at very high line speeds. Delayed alarm output signals are used to control downstream marking units or acceptance/selection gates, which facilitates the automation of testing processes.
Air-Coupled Ultrasonics
In contrast to conventional ultrasonic methods, no contact is required between the probe and the material to be tested, as the sound is transmitted via an air coupling mechanism. This eliminates the need for time-consuming cleaning and the risk of damage to the test object.
The air coupling mechanism is realised by means of an ultrasonic transducer that emits sound into the air on one side and picks up the received signals on the other side. The sound is transmitted from the air to the material to be inspected, where it encounters defects and is reflected. The reflected signals can then be used to draw conclusions about the condition of the material.
Example plastic tailgate
Plastic tailgates are regularly spot-checked within the production process. The Atline system — a quality control system in production installed at a stationary location near the production line — is designed to detect defects in the plastic joints.
For complex components such as tailgates, an ultrasonics method using air-coupling mechanisms is ideal because all corners and edges can be reached and correctly analysed. This is done fully automatically with the help of YouScan (YoUScan! — non-destructive material testing with air-coupled ultrasonics). A percentage indicates how much area of the glued seam is damaged or undamaged.
Conclusion
Non-destructive testing methods such as industrial computer tomography or air-coupled ultrasonic testing replace costly manual quality control procedures. The evaluation for quality analysis of the components can often be carried out automatically, thus saving time and costs.
