As engineering systems continue to evolve, so too do the demands placed on tribological testing. Electrified drivetrains, alternative fuels advanced materials are introducing operating conditions that are increasingly difficult to replicate using conventional laboratory approaches. In this context, a longstanding challenge in tribology is becoming more visible: behaviour observed in controlled bench tests does not always translate cleanly to real-world systems. At PCS Instruments, this is something we see increasingly across both research applied testing environments.

This disconnect is not new, but it is becoming more important as systems become more complex the limits of simplified testing approaches become clearer. Bench testing remains essential, but its role is being redefined. The question is no longer whether laboratory testing is useful but whether it is sufficiently representative to support meaningful engineering decisions.

Understanding the Gap Between Laboratory Application

At a research level, this challenge is often framed in terms of scale complexity. Pranjal Nautiyal, Assistant Professor of Mechanical Aerospace Engineering at Oklahoma State University, focuses on understanding interfacial behaviour across length scales, from atomic interactions to macroscopic contact. His work combines in-situ experimental approaches with fundamental analysis of friction, wear, bonding at interfaces, with the aim of designing materials lubricants that can perform under demanding conditions.

His work highlights a persistent limitation in experimental tribology:
“One major challenge is the lack of tools that can accurately replicate real-world contact conditions.” [1]

This speaks to a broader issue. Laboratory tests are designed to isolate variables, reduce uncertainty, enable repeatable measurement. In doing so, they simplify the system. Real applications, by contrast, are defined by interaction. Contact conditions evolve, surfaces change, multiple physical chemical processes occur simultaneously. As a result, behaviour observed in tribometers does not always map directly onto real applications such as gears, bearings or electrified powertrains. Operating conditions are rarely steady, the combination of load, speed, temperature, lubrication, environment produces behaviour that cannot always be reduced to a single controlled test.

Bridging this gap often requires multiple stages of testing, moving from simplified experiments to component-level validation. While this layered approach is effective, it adds time, cost, uncertainty, particularly when early-stage results are not fully representative of the final system. As Nautiyal notes, this can make it more difficult to rapidly adopt new materials lubricants in industry, where confidence in performance under real conditions is critical [1].

Mechanisms Over Metrics

While this challenge is well understood in research, its implications in applied environments are more immediate. For organisations working to solve engineering problems or deliver performance improvements, non-representative testing can lead directly to incorrect conclusions. 

Peter Lee, Institute Engineer Chief Tribologist at Southwest Research Institute, is clear in his assessment:

“The friction, wear failure mechanism seen in the bench test has to be the same as that seen in the real application. If that is not the case, the test is wrong.” [2]

What this highlights is a shift in emphasis. A test may produce highly repeatable data, but if it does not reproduce the dominant wear or friction mechanisms present in the real system, it becomes much harder to rely on those results when making decisions. This is an important distinction. Traditional bench testing often focuses on outputs such as friction coefficient or wear rate. However, these metrics only become meaningful when they reflect the same physical processes that govern behaviour in service. If the mechanism differs, the numbers may still be precise, but their value becomes limited.

Lee’s perspective also highlights how easily this process can break down in practice. If the real system is not fully understood at the outset, or if a test is adapted to fit the constraints of available equipment rather than the application itself, the resulting data may appear valid but fail to reflect real performance.

Designing tests that capture the correct mechanisms therefore requires a clear understanding of the application a deliberate alignment between test configuration real system behaviour. This includes identifying the dominant contact conditions, understanding how they evolve, ensuring that the test configuration reflects these conditions without introducing artefacts. As Lee outlines, this is not just about selecting a method, but about following a structured process: understanding the real system, designing a test to replicate it, selecting the appropriate instrumentation interpreting the results with an awareness of their limitations [2].

The Hidden Influence of the Test System

Even when the correct conditions are identified, another layer of complexity remains. It is often assumed that tribological measurements reflect only the behaviour of the contact under investigation. However, this is not always the case.

Ramalho Vilhena (2025) shows that the dynamic response of tribological test equipment can significantly influence measured friction wear results [3]. Factors such as system stiffness, inertia, vibration, the method used to apply normal load all affect how forces are transmitted recorded during testing.

In their study, different loading configurations produced substantial variations in both friction wear behaviour, despite nominally identical test conditions. These differences were not driven by the material system alone, but by the interaction between the contact the test apparatus. In some cases, changes in vibration even altered the dominant wear mechanism, highlighting that the test system can influence not only measurement, but behaviour itself [3].

This has important implications. It suggests that differences between laboratory real-world performance may not only come from simplified contact conditions, but also from how the test system behaves during measurement. In that sense, the test setup itself becomes part of the system being studied. Understanding this interaction is key to ensuring that results are both reliable meaningful. It reinforces the idea that experimental design needs to consider the full measurement system, not just the contact interface.

Confidence in Results

As testing becomes more complex, the importance of confidence in experimental results increases.

Working in applications where operating conditions are often harsh unpredictable, particularly in areas such as electrified systems wind energy, Parker LaMascus highlights the importance of benchtop testing that can move beyond simplified outputs. In his work on antiwear tribocoatings, the challenge was not just measuring friction or wear, but understanding how protective films form, evolve, behave under changing conditions. In these systems, performance is not defined by a single value. It depends on how surfaces respond over time, how coatings develop at the interface, how those changes influence behaviour under load. Capturing that requires more than a steady-state measurement. It requires visibility into the process itself.

To support this, his team utilised PCS instrumentation to access multiple streams of data within a single experiment, including time-resolved friction behaviour in-situ film thickness measurements. This allowed them to move beyond average values begin linking measured performance to the underlying mechanisms driving it.

“PCS machines have a robust operating range for our use cases, but more importantly, the tool allows our team confidence that our results are repeatable scientifically sound.” [4]

This confidence is not only a function of repeatability, but of understanding. When experimental data captures how behaviour develops, rather than just the outcome, it becomes easier to assess whether a test reflects real conditions or simply produces consistent numbers.

In this context, the role of instrumentation becomes more than measurement. It becomes a way of connecting laboratory observations to real-world behaviour, giving researchers greater assurance that what they are seeing in the lab has meaning beyond it.

Looking Forward

As engineering systems continue to increase in complexity, the gap between laboratory testing real-world performance is unlikely to diminish. If anything, it will become more noticeable. Addressing this challenge requires a shift in how testing is approached. Rather than applying standard methods in isolation, experimental programmes need to be designed with a clear understanding of the system they are intended to represent. This includes identifying key mechanisms, selecting appropriate conditions, being aware of how the measurement system itself may influence results.

It also requires collaboration. Researchers, industry, instrumentation developers all have a role to play in ensuring that testing approaches evolve alongside application demands. In this context, the role of tribology extends beyond measurement. It becomes a way of building understanding, connecting controlled experiments to complex real-world systems. Ensuring that this connection is both reliable relevant will remain central to the field in the years ahead.

References

[1] Nautiyal, P. (2025). US Voices: Dr Pranjal Nautiyal. PCS Instruments. https://us.pcs-instruments.com/articles/us-voices-dr-pranjal-nautiyal/

[2] Lee, P. (2025). US Voices: Dr Peter Lee. PCS Instruments. https://us.pcs-instruments.com/articles/us-voices-dr-peter-lee/

[3] Ramalho, A., & Vilhena, L. (2025). Experimental approach in tribology: Effects of test equipment dynamic response on the reliability reproducibility of the results. Wear, 205770. https://doi.org/10.1016/j.wear.2025.205770

[4] LaMascus, P. (2025). US Voices: Dr Parker LaMascus. PCS Instruments. https://us.pcs-instruments.com/articles/us-voices-dr-parker-lamascus/