Changing demand

As testing equipment gets ever more capable, manufacturers also have to make it flexible to respond to the cross-industry trend of changing material choices.

In the wake of the VW scandal in the autumn, a shockwave has been moving its way through industry. The supply chain is rightfully worried. The pressure on today’s engineers is greater than ever. Target driven innovation see’s more companies become dominated by quarterly results and engineers are expected to deliver savings, add value, and make sure future products meet all the tough future legislative targets on a rolling month by month basis. Clearly, it has become too much.

It has forced many firms to look inwards at their own processes and products. Nowhere was this more apparent than within the testing and analysis sector where the very products are used to quantify and by association judge the resulting engineering effort.

“The question I think about is, can this happen in my organisation,” says Dr Jan Stefan Roell, chief executive of multinational testing equipment manufacturer the Zwick Roell Group.

Headquartered in Germany, the fallout of the scandal is uncomfortably close to home, forcing some difficult questions to be asked. “How much pressure can we put on people to get super performance and when are we over doing it so much that they feel they have to cheat.

“How do we manage our people in a way that they are not afraid to come back and say, listen management, we can’t do it.”

The problem often lies in the culture of the business and industry driven targets. Automotive standards on emissions have placed targets directly on the shoulders of engineers, which have been told, ‘find technical solutions and lower emissions, or this company with face severe sanctions’.

Rapid change

It has seen a sea change in material usage in the last five years, with modern cars having as much plastic on the chassis, as metal. Some have moved to aluminium, others continuing to progressively implement composite. It has not been easy, and it certainly hasn’t been cheap.

The knock on effect has been felt by those providing machines to test the properties of materials, and the methodology to standardise procedures and get repeatable results. Systems for testing materials have needed to become smarter and faster, with new machines and methods needing to be developed all together.

Innovation all round

At the recent Zwick International Forum, things had changed significantly in the two years since my last visit. Its various halls were filled with swathes of machines specifically aimed at composite material testing, developed in response to customer demand.

An example is the patented Hydraulic Composite Compression Fixture (HCCF) used specifically for the testing of carbon-fibre-reinforced plastics (CFRP) and glass-fibre-reinforced plastics (GFRP) with unidirectional fibre-reinforcement. These hydraulically operated grips offer several technical and cost saving advantages compared to existing and often troublesome mechanical fixtures.

The open C-frame construction facilitates the simple and fast loading of specimens, and allows for easy attachment of extensometers. The difficulty in specimen alignment and mechanical set-up often found with traditional fixtures has been eliminated mainly due to a friction free and precise guidance system.

Johannes Buhrle, head of industry management. “HCCF has brought down the reject rate of tests from over 50% to 16%.”

While this is a huge improvement, 1 in 6 tests is still invalid – showing there is plenty of room for improvement. “Customers were tolerating this rejection rate, so to get something that can get it down to 16% is a major step forward,” says Buhrle who blames the standard that requires a maximum offset of 10 microns.

The hydraulic operation of the grips guarantee reliable and reproducible clamping of the specimens, as the clamping force is applied uniformly and securely across it.

The compression testing fixture can also be used at high or low temperatures ranging from -60 to +95°C, and the ability to utilise extensometers saves costs further by avoiding the need to bond strain gauges to the specimen.

Beyond automotive

Another example is the need to test at elevated or cycled temperatures, during something like a tensile test. Material testing in temperature chambers is perhaps more important with plastic and composite materials, as mechanical properties quickly change under the influence temperature, far more so relative to metallics.

Zwick’s temperature chambers have been carefully integrated with its range extensometry, ensuring reliable and repeatable results for both optical or contact measurement. The chambers also allow for temperatures to be cycled between 80 to 250°C, with a short cycling feature available for those that desire this function.

Like the automotive industry, aerospace over the past decade has invested significantly in composite materials. However, in both industries, there is an interesting phenomenon in that despite both using more composite and plastic materials, the use of metallics has not diminished.

“The composite trend in aerospace is still going on, but at the same time we are seeing a trend back to aluminium,” said Dr Stefan Roell. “It’s amazing, but this is normal competition. One material overtakes the other – but these guys are not asleep. So we are seeing the first trends back to aluminium.

“For the automotive guys a huge challenge to pick the right material, as they are normally stuck with it for a decade. We see the trend to composite going on, but with much more down to earth expectations. There have been problems and the production technology is still not quite there. High strength steel is definitely looking like it could be used as an alternative.”

The possibility of having multiple materials, possibly in the same assembly, has seen Zwick adopt a much more modular approach to in its machines allowing users to use the same machine for different needs, depending on how it is set-up.

The critical thing is to ensure there is sufficient force capacity in these universal testing machines. It is the case that it is easier to find supplementary load cells reduce the force range where necessary, but an upper limit tends to be set by the frame itself.

Alan Thomas, marketing manager at Zwick UK says: “Provided you have the correct range of load cells, range of grips, extensometery, the frame doesn’t mind if it is testing composites, steel, aluminium or anything else.”

And it is probably just as well given the number of materials and processes fast coming to the fore. High strength steel and graphene reinforced plastic are just two potentials quickly coming of age and being adopted. However, while a high strength steel might just need a load cell to become ‘beefed up’, testing nano materials has required some fresh innovation.

Testing for coatings and films

The trend towards miniaturisation of components has created a corresponding need for methods of determining the mechanical load capacity of thin films and coatings, including adhesive strength and wear. Investigation of mechanical properties of thin films and coatings is predominately a time consuming and cost intensive exercise.

For this reason, Zwick has developed a process to characterise films only a few µm thick using its nanoindenter. Zwick's ZHN nanoindenter is specifically tailored to test the adhesive strength and wear of films and coatings, while its modular design allows it to cover a wide range of application. Tests involving forces up to 2N and indentation depths smaller than 0.2 µm are performed.

The ZHN’s two measuring-heads can be used as either a normal measuring-head, so the instrument functions as a depth-sensitive hardness tester in the micro range. Or, using the lateral measuring head, which features similar resolution in the nano range, it can enable dynamic measurement.

This combination increases the number of possible measurement procedures considerably. The instrument can be used as a micro scratch tester, micro wear tester, fatigue tester and high-resolution profilometer.

As force generation and force measurement are completely independent of each other, force and displacement control are both possible. External influences such as adhesive forces can also be detected.

Other advantages include the optics with high positioning accuracy and rapid measurement, as the use of two cameras for two magnifications eliminates the need for lens changes. The operator also has the advantage of support from the intuitive InspectorX software, which features individually tailored user rights, easy positioning and special algorithms for determining indenter area function and instrument stiffness.

Mass spectrometer development

Shimadzu, one of the world leaders in analytical instrumentation, has released the LCMS-8060 triple quadrupole mass spectrometer, designed to push the limits of liquid chromatography–mass spectrometry (LC/MS/MS) quantitation for applications requiring the highest sensitivity and robustness.

For example, it detects substances at ultra-trace level as they occur in complex matrices or in the smallest sample concentrations, which have to be diluted in order to avoid matrix effects.

The LCMS-8060 is the latest member of Shimadzu’s Ultra-Fast Mass Spectrometry family and part of the Shimadzu mass spectrometry platform of MS/MS systems with ultra-fast technologies. It underlines Shimadzu’s role as one of the world’s fastest-growing mass spectrometry companies.

The system combines a heated electrospray ion (ESI) source with all ultra fast (UF) technologies including UFsweeper III, a collision cell filled with argon gas. Through its high speed technology, UFsweeper III achieves dwell times of just 0.8ms per multiple reaction monitoring (MRM).

With UF Qarray ion guide technology increasing ion production and signal intensity, the LCMS-8060 a data acquisition scan speed of 30,000u/sec and a polarity switching time of 5ms.

Justin Cunningham

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