Wear measurement with n-RAI radionuclide measurement technology

for a reliable edge in engine and lubricant development

Radionuclide measurement technology in model testing (n-RAI) lets you measure nanowear precisely and efficiently by counting radioactive particles in the SRV® test system. For engine and lubricant development, this represents a cost-effective, easy-to-use analysis and measurement method with good practical correlation and accurate, conclusive results in short test times.

  • Radionuclide measurement technology for motors and lubricant development
  • Efficient tests with highly precise results in the nanorange
  • Economical; short test times

Background: Radionuclide technology

Radionuclide technology (RNT) is a proven methodology for the continuous measurement of wear. Because of its complexity and high radiation safety requirements, it was previously used only in special test rigs. With n-RAI, you can now take advantage of the analysis capabilities of the RNT method in the SRV® model testing environment.

These primarily include continuous measurement of wear in the nanorange, 2-isotope technology, the determination of realistic wear rates as a basis for extrapolating system lifetime, the differentiation between running-in and constant wear as well as the option of mechanism-oriented wear tests.

The activity concentrations of the used radioisotopes are between 5% and 30% of the limit values for permit-free handling of radioactive substances. This means that testing can take place in any lab environment.

n-RAI: Indispensable for your development work

The n-RAI option lets you perform numerous practical measurement scenarios on the SRV® test system during engine and lubricant development. Not only does n-RAI expand the SRV® measured variables-spectrum in standard tests (e.g. with ball-disk geometry, standard tests), it can also help clarify specific tribological issues.

Relevant application examples from research and development:

  • Determining the difference between running-in and constant wear
  • Using 2-isotope technology to separately determine wear, e.g. on the piston ring and cylinder wall or any two friction partners; or observing wear on two different locations of one test body.
  • Mechanism-oriented studies of wear processes through direct measurement of wear particles and element-specific selection of isotopes
  • Screening tribosystems before costly test rig trials
  • Dynamic testing of tribosystems properties, such as the piston ring-cylinder wall in relation to the load collective (load, temperature, stroke, speed and angle of inclination [0° - 90°]).
  • Creating the complete tribometric profile of a tribosystem
  • Determining the effect of different additives and additive concentrations in a known oil on wear behavior (comparison of wear profiles)
  • Optimizing lubricants/additives/fuels: Aging tests of lubricating oils under consideration of all tribological parameters
  • ERP analyses of lubricating oils
  • Estimating service life based on wear rate/failure conditions of a lubricating oil
  • Determining the wear behavior of different metal alloys with a reference lubricant
  • Determining the effects of fuel composition on the wear behavior of vehicle modules/components (e.g. piston ring/cylinder lining)
  • Determining the emergency running properties of engine components

n-RAI: Wear measurement technology for many measurement options


  • Wear protection and adhesive properties
  • Lubricity under varying conditions (temperature cycles, varying sliding speed, load cycles)
  • Investigating the impact of biological or mineral fuel residue in the engine lubricant
  • Investigating the influence of different oil aging conditions on the wear process


  • Reducing friction losses by optimizing the surfaces and shape of friction partners in the tribosystem (e.g. piston ring/cylinder liner)
  • Precisely quantifying wear on basic or opposing body during testing
  • Investigating the impact of biological or mineral fuel residue in the engine lubricant
  • Determining the effects of surface treatment (e.g. hard layers, honing, laser texturing)


  • Determining the resolution capacity depending on surface composition and activity distribution of up to 10 nm wear depth
  • Investigating system behavior under particular load situations, e.g. at the upper dead center
  • Determining the interactions between the lubricant and the material (interface)
  • Simultaneous recording wear as well as all previous SRV® measured variables

Short portrait of n-RAI

Specially developed for the SRV® model testing environment, radionuclide wear measurement technology is based on the marking of specimens via thin-layer activation. This allows study of the wear processes of tribologically loaded surfaces with nano-precision. The SRV® test system provides realistic wear rates at acceptable test times as early as the model testing phase.

Special characteristics:

  • Material-specific activity and isotope distribution:
    For each alloy system, the spatial and quantitative distribution of the radioactive isotope is determined and verified.
  • Zonal activation:
    The sample is only activated where specifically necessary for the measurement.
  • Activation of a super-thin surface layer:
    Only a very thin surface layer of the sample is activated by particle bombardment. This results in clearly defined, extremely small bulk doping.
  • Precise calibration:
    Precise calibration of the complete detector, test body and model testing system enables determination of wear in the nanometer range. Only state-of-the-art radiation detectors are used.
  • User-friendliness:
    The selection of suitable isotopes, together with the distribution of activity, ensures that n-RAI can be used in your laboratory without the security measures associated with the handling of radioactive material. The total activity of a sample remains well below the statutory limit (EU directive*).
  • Continuous wear measurement in real time:
    Wear behavior can be monitored online. A detailed statement on wear development featuring nm/h-accuracy is provided within several minutes.
  • Consistent overall model:
    Rigorous application of scientific statistics results in a consistent overall model. This model is based on the latest findings and thus offers the evaluation of realistic wear rates.

* Council Directive 96/29/EURATOM (May 13, 1996) laying down basic safety standards of the health of workers and the general public against the dangers arising from ionizing radiation

Advantages of n-RAI technology

Radionuclide wear measurement integrates radionuclide technology analysis in the SRV® model testing environment.

This gives you many compelling benefits:

  • Wear can be measured within minutes and displayed in real time.
  • Determination of initial and constant wear rates in nm/h
  • Activation of a super-thin surface layer:
    Only a very thin surface layer of the sample is activated by particle bombardment. This results in clearly defined, extremely small bulk doping
  • Typical questions concerning motor testing can be investigated with good practice correlation to engine test benches on the SRV®
  • Short test times compared to engine test benches
  • User-friendly handling of the samples because overall activity remains below the legal limit
  • System life can be extrapolated with this procedure
  • Realistic load collectives result in realistic wear rates
  • Continuous monitoring and display of the wear behavior
  • Cost-effective analysis and measuring method
  • Competent, single-source consulting and support in questions of tribological model testing as well as practices related to specimens and radioactivity
  • • On request, we perform all handling including supply and disposal of activated test specimens

Employing n-RAI technology in SRV®

n-RAI is used in the SRV® model test environment as follows:

  • Samples with activated zones are tribologically loaded in the SRV® Test System.
  • A pump transports wear particles to the radiation detector via the lubricant circuit.
  • The ionizing radiation is measured, which allows correlation of the number of counted radioisotopes to the total number of wear particles.
  • Based on the known activity and isotope distribution, the wear in nm/h is determined from the data measured by the detector and displayed online.
  • Typically, only a few minutes are needed to measure significant evidence of a few nanometers of wear height. The longer the measurement and testing time selected, the better lower wear rates can be distinguished.
  • n-RAI technology can be used in SRV® or 2disk test systems.

We would be happy to perform n-RAI wear measurements for you in our tribological testing institute. Contact us for more information. > Contact