Quality control with maximum precision

Wall thickness measurement is the most often applied ultrasonic testing technique.

Precision wall thickness measurement is mainly used for the quality control of individual and serial parts. It may either be carried out manually or by means of ultrasonic systems integrated into the production process. Suitable side conditions allow for wall thickness measurement with a tolerance of ± 0,01 mm .

However, this method is more often used for the detection of erosion and corrosion damages than for precision wall thickness measurement. In comparison with the mechanical measuring the ultrasonic wall thickness measurement is of advantage because it may be carried out even if only one side of the part to be tested is accessible for the NDT-technician. Thus for instance the wall thickness of tubes in operation may be determined by ultrasound without any problems.

Layer thickness testing may be considered to be a special case of wall thickness measurement. However, for this purpose are not only applied ultrasonic but also electric-magnetic procedures.

Reliable and responsible

Weld seam testing is one of the classical fields of ultrasonic
testing applications. It is applied if after the joining of metallic
materials a non-destructive testing is required either by the
product or by the customer and if due to the material thickness
and/or the kind of material X-ray testing cannot supply reliable information. In many industrial branches ultrasonic weld seam testing is required, the most important are the pipeline and tank construction.

Weld seam testing may be carried out by means of radiation, ultrasonic, magnetic crack detection or dye penetrant testing.

Ultrasonic testing is mostly carried out in accordance with regulations or a company’s specification. Usually weld seams are tested by means of 70 °, 45 °, 60 ° probes or in case of ground weld seams also by means of a straight beam probe.

The definition of defects depend on the thickness of the sheet metal or the pipe wall, the material as well as the part stress. They are determined by means of the applicable specifications resp. the regulations.

The weld seam form and the kind of welding determine the typical defects, which may for instance be slag inclusion, pores or joining defects.

Quality testing and focussing on spotwelds

Resistance spot welding is the most important joining method for large series production of motorcar bodies. Numerous influences determine the production quality of spotwelds. They are subject to a high quality standard. Therefore, the systematic control of the produced spotweld joints is necessary. Up to now the conventional hammer and chisel testing is mainly applied for the quality control of spotweld joints in the automotive industry. By using a hammer and a chisel the spotweld joint is destroyed. The quality is tested on the basis of the breaking characteristics. The spotweld diameter and the characteristics of the spotweld are the quality features.

For the following reasons this type of testing is of disadvantage:

• Destructive testing method, destruction or deformation of the test body
• Relatively long testing times
• Increased work risk during destruction of the test body

The non-destructive ultrasonic testing of the spotwelds is a real alternative, which has proved to be indispensable particularly for galvanised sheet steel.
Ultrasonic testing is applied for galvanised sheet metal, covered and non- accessible spotwelds and for cost reduction purposes replacing the destructive method for individual production and prototype construction.

The new digital ultrasonic testing analysers are laid out for complete documentation and offer an operator friendly display adapted to the testing process and therefore, it is of essential advantage. When monitoring a large number of resistance spotwelds rapid, flexible and safe operation and documentation are a must. For a number of sheet metal combinations a safe quality evaluation may be carried out by means of the state of the art ultrasonic method. Correlation with hammer and chisel testing and examinations on reproducibility prove the practicability of the system.

Quality testing of semi-finished products

The ultrasonic volume inspection is mainly applied for the production or processing of semi-finished products, such as rods, bars, pipes or sheet metal. Preceding the following processing step volume testing with ultrasonic guarantees that there are no internal and, as the case may be, external defects which could lead to the part being rejected during the further production process.

HIC-testing, testing for hydrogen induced crack corrosion or condition monitoring of driveshafts for turbine rotors are examples for volume testing of parts being in operation.

Condition monitoring of shafts, axles and pins

The continous condition monitoring of critical shafts, axles and
pins in a number of built-in and mobile plants is normally almost
impossible because these kinds of components are usually built in deeply within a plant. The most effective method of inspecting this kind of parts is to use magnetic particle inspection (MPI); however, this is only possible if the part is removed from the wheel set to gain access to the outer surface.

VOGT Ultrasonics GmbH is able to improve current UT techniques with their flaw detection system and inspect various critical shafts, axles and pins which are still in operation. This kind of inspection offers the following advantages:

The system detects cracking early avoiding unexpected failures, allowing
more efficient maintenance planning. The used inspection system provides reproducible data collection to allow accurate monitoring of crack growth and permanently stores a detailed 3D signature of the shaft for comparison with later measurements.

The test results can be fully analyzed away from the test shaft ensuring minimal access and downtime of equipment. We give you results which are reported in a meaningful graphical format allowing more informed maintenance decisions.

We only require access to the end(s) of the shaft for the inspection. The parts can stay in operational position.

This kind of inspection can provide major cost savings by maximizing the service lifetime of shafts and avoiding catastrophic failures.

Keeping on track with material flaws

In our high-tech and automated world, reliable technique is of enormous importance. In our everyday life we often trust unknowingly in constructions that are subject to high safety standards.
This trust is naturally justified, because especially vital parts are subject to legal guidelines. This is why these parts are subject to ongoing inspections, which therefore secure the functionality and safety while being in operation.

The surface crack testing can be carried out by means of dye penetration or magnetic particle inspection or even eddy current crack testing. These testing methods are reliable possibilities to detect surface material flaws.

Dye penetration testing

The dye penetration procedure is one of the oldest non-destructive surface crack-testing methods. This test benefits from the capillary effect of material cracks open towards the part surface.

The NDT-technician applies dye on the part surface which penetrates into the cracks where it remains inside the material cracks even after the part surface has been cleaned. A developer, being applied after the cleaning of the part surface, extracts the dye from the material cracks. Due to this kind of "bleeding" the cracks become visible on the surface.

The dye penetration testing is suitable for the surface crack testing of almost all materials. It is broadly used in the industry so that we may desist from listing the great variety of applications.

Magnetic Particle Testing

Magnetic particle testing is a process that detects surface defects and subsurface defects, like for example hairline cracks on steel and ferrous materials. By magnetizing the test part, flux leakage occurs so that magnetizable particles in the test suspension are attracted and will remain stuck. Due to the contrast between test supension and underground this effect becomes visible.

Eddy Current Method

Eddy current testing is a fast, precise and cost effective method of non destructive testing for detecting surface and subsurface material defects. The advantage when using eddy current is the virtual contact-free working method, the high sensitivity with microscopic small defects as well as very high test speed. This method applies for testing raw materials, maintenance testing or quality control on finished products.