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Challenges of testing

Challenges of testing

By TA News Bureau:

The challenges before tyre testing engineers are enormous. It is because tyre is a highly engineered component. Each tyre can have its own characteristics, or ‘fingerprint,’ which can be represented by its footprint to some extent. There are many variables involved in understanding how a tyre would perform in different situations, says Dr Madhura Rajapakshe, Project Engineer with the Akron-headquartered Smithers Rapra, a 90-year old company specaialising in tyre, rubber, plastics and polymer testing. In an interview to Tyre Asia he says development of tyre test programmes calls for a robust test plan which is an enormous task facing the engineers

Dr Madhura Rajapakshe is a top-flight R&D Project Engineer with Smithers Rapra, a 90-year old company specaialising in tyre, rubber, plastics and polymer testing for global clients. It also offers consulting services, training, publications and market reports focused on the tyre, industrial, automotive, consumer and medical industries.
Since joining the company in 2012 after taking a PhD degree from the University of South Florida, he has been specialising and researching issues such as tyre rolling resistance, durability, tread wear, traction, and footprint mechanics.
Smithers’ clients include government institutions, raw material suppliers, fleet companies, tyre and vehicle manufacturers. He also specializes in software development for testing, data processing, and process improvement.
Says Dr Rajapakshe: “As each tyre can have its own characteristics or ‘fingerprint’, it throws up many variables. Understanding how a tyre would perform in different scenarios demands developmental of test programmes that involve non-standardized test methods. Therefore, coming up with a robust test plan sometimes gets challenging.
“For example, most indoor tyre wear test projects have the main goal of running a very controlled test to compare the wear performance of several tyres. However, in many situations, our customers are also interested in knowing how the indoor wear performance correlates to outdoor wear,” he says.
“The common challenge here is the fine-tuning of our indoor wear drive patterns to fit the outdoor conditions because sufficiently detailed drive-pattern data is not always readily available from outdoor testing.”
He said global tyre manufacturers evaluate their product against both regulatory and OEM requirements, which can vary from country to country. In the tyre development process, sometimes they are interested in benchmarking against their competition or previous iterations of the same product.
“In many such cases, we work with our customers to understand the purpose of the test programme in order to determine the suitable test methods that will fulfil the project’s goals best,” he explains.
Simply using well-established industry testing protocols is sometimes the answer, but in many cases, it requires a creative approach to identify the best test techniques and sampling strategies that deliver reliable results.
“Our global team can assist with this process from material chemistry, modelling, and tyre engineering,” he points out.

Test parameters

Commenting on the key parameters that he would be looking into while testing, Dr Rajapakshe said they would monitor all the test parameters that are known to affect the measured property of a tyre, which are normally specified in the standard test protocols.
Several examples of such tests include endurance, rolling resistance, force and moment, tread wear, and heat aging.
“Smithers continuously invests in new measurement technologies and advanced control systems to stay current with the testing industry trends as well as to ensure we meet or exceed the most recent versions of the entire test protocols covered in our ISO 17025 certification,” he stressed.
Smithers operates tyre testing facilities in both the US and China that can work with clients to understand which parameters are most critical to a given testing programme.
When asked whether there would be differences in the results while testing in controlled laboratory or test track conditions and on the road when checks are made to gauge rolling resistance, energy efficiency, rolling noise, braking, and handling, he said that there would be differences.
“There will be differences in almost all cases that are not specifically designed to closely simulate test track or road conditions in the laboratory,” Dr Rajapakshe said. Some of these differences are attributable to known deviations in the test conditions.
“Various laboratory tests for tyres have been developed over many years with an effort to control as many testing variables as applicable,” he explains. They enable understanding, benchmarking, and improving performance relatively easily without having to go on the road for testing all the time.
“Real world testing involves numerous ever-changing variables that make achieving repeatable results extremely difficult, time-consuming, and expensive.”
Giving an example, he said although there are reliable theoretical conversions for tyre rolling resistance from a laboratory drum test to a flat road surface, the differences in the textures of a variety of road surfaces can account for a difference of several percentage points in the expected fuel efficiency.
“Differences of the same degree of magnitude can occur due to deviations in tyre inflation pressure from warming up at different seasonal temperatures as well as losing air between different drivers’ practices for checking and adjusting tyre pressure,” he points out.
In summary, there are specific tests that are ideal for indoor laboratory settings and some which are better suited for on vehicle, real-world, subjective testing. Both are commonly used to paint a full picture of a given tyre’s performance attributes.

Quality evaluation

When asked whether there are any major differences in the tyre evaluation for quality control under European Union standards and elsewhere, particularly in the United States, Dr Rajapakshe said regulatory requirements for tyre evaluation are normally based on safety requirements, environmental considerations, and consumer information.
“Governing bodies throughout the world seem to have consensus on many regulatory aspects when it comes to tyres, especially in terms of safety and environment,” he says.
This is evident by the development of the Global Technical Regulations for tyres by the United Nations. However, some main differences that exist are the pass-by noise requirements in Europe and the tyre tread wear ratings in the US.
On how Smithers Rapra can help global tyre manufacturers gain from tyre testing by his company, Dr Rajapakshe said it has been providing reliable data to clients for several decades.
“Our global team has over 100 years of collective experience in the tyre industry as manufacturers, raw material suppliers, and automotive OEMs, which brings a very broad perspective to our clients’ testing requirements.”
Through Smithers’ tyre and wheel testing facilities in both the US and China, it provides a full range of tyre testing capabilities required in the industry today. The list includes endurance, ageing, rolling resistance, force and moment, indoor tread wear, and many other test capabilities, such as materials characterization and performance, construction evaluation, dimensions and measurements.
“We can provide clients with comprehensive data sets and advice on what test methods to use and how to properly interpret the data,” Dr Rajapakshe says. “As an independent, third-party test provider, we treat test projects from all our clients with complete confidentiality and go to great lengths to protect confidentiality during every stage of testing.”
On the coming changes in the automobile and tyre industry, he referred to the electrification of mobility where light-weighting is given emphasis.
Autonomy, electrification, and light-weighting have become key development drivers in the past few years. Each trend brings unique and sometimes conflicting implications for tyre design and development.
“In all three trends, we anticipate that the tyre industry will continue to see a shift towards even better fuel efficiency and lower weight before it levels off due to obvious reasons, such as limitations in material technologies, difficulty of optimizing for other tyre performance attributes, or, in some special cases, other reasons such as the benefits of a lower centre of gravity.”
Tyres are also becoming a source of intelligence within the autonomous system. As the tyre is the direct connection between the road and the vehicle, monitoring its condition becomes a key factor for safety and performance in autonomous driving.
Sensors that measure tyre pressure, temperature, tread depth, and surface conditions are being developed for the vehicle of the future. In the case of electric vehicles, heavy battery packs, higher torque, and driving-range requirements call for special performance criteria. A wider contact patch may be required in some cases to accommodate higher starting torque.
Having low rolling resistance while carrying a higher load is a challenging problem to solve considering competing safety-related requirements, Dr Rajapakshe said.

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