Determining the Service Life of a Thread: Quicker, More Precise and More Economical – Even for Custom Solutions
Threaded spindles and nuts have been a central part of modern life since the dawn of industrialisation. A startling fact: at present, it is practically impossible to predict their durability and wear, which is of critical importance for securing your investments. Introducing the new TriboLife thread testing system: it can rapidly reproduce wear through experimental testing, rendering expensive endurance test stands largely redundant.
Friction produces heat. Even non-engineers can grasp this statement with ease. But friction is much more. More precisely, friction is the resistance that occurs when two contacting bodies move. Friction provides grip. Friction lets us to come to a stop on a damp tiled floor after we shower.
Ancient Laws of Friction from 1699 – and Many Unanswered Questions
There are many examples of the positive effect of friction. But friction also causes much consternation for engineers and technical applications, which can be easily seen for the example of threaded spindles. If threaded spindles are installed in machines and systems, they are usually exposed to heavy loads. Reliability and maximum durability are therefore of particular importance, especially in the case of lifting equipment. The issue: even today, science still finds it difficult to calculate frictional forces accurately. The laws of friction that we use today can be traced back to Guillaume Amontons in the year 1699.
In Threads and Machines: Friction Leads to Vibration
The effects of static friction and sliding friction have a direct influence on workpiece vibrations and therefore make it difficult to reliably predict the service life of threads. However, researchers are now focusing on the topic once again. If we look at the surfaces of two contacting surfaces at an atomic level, measurements show that surfaces experience extreme vibrations above a certain amplitude. These vibrations continue as vibrations in the thread and are completely disordered and chaotic at an atomic level. In other words: friction is and remains difficult to calculate in exact numbers. In practice, reaching a reliable statement on the durability and service life of threads often involves lengthy stress tests over many weeks. The simulation of ageing takes up resources, costs a lot of money and puts pressure on productivity.
“Of course, as thread specialists, we are constantly asked about the service life of our products,” says Moritz von Soden, Managing Director of Bornemann Gewindetechnik. “Our engineers then have to explain the complexity of physical friction. For trapezoidal threads especially, there are hardly any reliable calculation methods. However, in collaboration with SincoTec Test & Engineering GmbH, we have managed to develop a test procedure that allows us to determine the service life of a spindle/nut system very precisely and much faster.”
Innovative, Fast, Precise: the TriboLife Thread Testing System
Fatigue damage is generally used to calculate the service life of components in mechanical engineering (a material fracture, for instance). For threads, however, “total failure” is a less important factor than the calculation of wear. In the case of trapezoidal threads in particular, the design is therefore not synonymous with the calculation of the service life.
With TriboLife, ageing processes can be experimentally reproduced faster than ever before. It makes long-term testing on specially designed test stands largely redundant. Pre-loads of several tons can be applied. A huge variety of different lubricants can be introduced. Interaction between nut and thread is ensured thanks to a freely adjustable angle. In addition, the threads can be subjected to a wide range of temperatures during testing. TriboLife reaches test frequencies of 25 hertz, which means the wear that occurs over 10 years can be reproduced within one week. For many designers, especially those working on new developments, this type of reliable wear data is important, particularly when it comes to comparing materials and production methods in several test series to each other.
Experimental Service Life Calculation for Complex Threaded Components
“Accurately predicting the service life of threads is still a challenge, even with TriboLife. But its scope of application is wide ranging. The fast testing system is really beneficial, especially for designing trapezoidal threads correctly,” explains Dipl.-Ing. Steffen Krause, Head of Development at SincoTec Test & Engineering GmbH. “It lets our collaborative partner Bornemann assist demanding customers on a completely new level. Remember: up to now, intensive endurance tests were simply too expensive for most applications. TriboLife lets us do more – we will be able to make accurate statements about wear and service life in the future, even for special threads.”
You can also find more information about TriboLife on YouTube:
Bornemann Gewindetechnik (www.bornemann-gewindetechnik.de) manufactures threads of all special shapes and sizes. We produce custom solutions for lifting technology and hydraulic steelwork applications, and platform equipment and gate valves for dams, to name just a few. Alongside challenging high-precision work on buttress threads, feedscrews and multi-start threads, we also focus on the production of large, ready-to-install trapezoidal thread spindles and nut sets. Any kind of machinable material can be used as the starting material. The standard sizes for threaded spindles range in diameter from 10 to 300 mm and up to 10 m in length. Longer lengths of up to 100 m can be produced in multi-part designs. Bornemann’s optimised manufacturing process produces thread surfaces that achieve a quality equivalent to ground threads.» Zurück zur Artikelübersicht