Testing is key to meeting endurance requirements for springs
Springs in different applications are subject to different levels of usage – from modest usage in an automotive seat mechanism to much more demanding duties in typical aeronautical applications – and it can be important to have data for spring fatigue in these real world tasks.
“Fatigue is not just a body function for athletes,” says William Hughes technical director Emma Burgon. “Any component working in a dynamic application is prone to fatigue. We can – and do – model theoretical lifespan, and that’s useful information, but practice can differ from theory so the only way to guarantee lifespan is to test in real life.”
William Hughes has increased its component endurance testing capabilities with the acquisition of two new compression spring fatigue testing machines from Italian test equipment specialist Micro Studio. With the investment in these new machines William Hughes can test fatigue on compression, tension and some torsion springs. There are also facilities for endurance testing of torsion bars and seat mats. This enables the company to guarantee its springs will meet customer requirements for a minimum number of cycles without breaking.
The new machines enable William Hughes to test large numbers of cycles on compression springs very quickly, establishing the minimum number of operations a component or assembly can achieve. “More and more customers are demanding within their production specification that a certain component must be able to achieve a given number of operations,” explains Burgon.
“If a main assembly has to meet, say, 20,000 cycles, then all of the components within that assembly must be able to meet that cycle requirement, under stress conditions, even if they’re not involved in all actions. Knowing that a particular spring will not fail during those 20,000 operations gives the customer confidence, and means he can in turn guarantee the safety of the whole assembly.”
With two machines, William Hughes can test up to 24 springs simultaneously, with the machines ensuring accurate strain tests of compression springs even at the highest speeds. The equipment gives William Hughes the capability to test springs up to a load of 30kN as standard, and the machines can be equipped to test springs up to a load of 40kN. The company can fatigue springs to specified numbers of cycles without breaking, or until the spring breaks. When a spring does finally break, the machines record the number of cycles achieved at that point. “It’s not unusual for us to be asked to produce springs that will offer spring lifecycles of tens of thousands or even tens of millions of operations without breaking,” says Burgon. “With these new machines, we can back up spring theory with real world testing, and offer the guarantees that give our customers the highest levels of confidence.”
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