ISTs Fatigue Testing Methodology and Capacity

 

IST will carry out a brief spring design assessment to check the test parameters/requirements so as to establish the most appropriate of IST’s suite of fatigue test equipment to be used for the work. The spring design details (i.e. material type, wire size, outside diameter, number of coils, free length and test lengths) are all input into IST’s Spring Calculator Professional software from which the most appropriate test speed is established – this is either 1/13th of the spring natural frequency or the maximum speed of the test machine, whichever is the lower.

 

All of IST’s fatigue testing is accredited to ISO 17025.

 

IST’s fatigue test machines.

 

FM13/14/15       These test machines are capable of testing springs up to 1000 N in load with a maximum stroke of 30 mm deflection, and can accommodate a maximum outside diameter of 90 mm. The test speed is load dependant, so could be between a maximum of 3000 rpm and a minimum of 120 rpm. The deflection is set to an accuracy of ±0.02 mm and initial test length of ±0.02 mm. These machines have the facility to test at elevated temperature up to 200°C or at sub-zero below -40°C using carbon dioxide pellets.

 

FM18                     This test machine is capable of testing springs up to 3000 N in load with a maximum stroke of 30 mm deflection, and can accommodate a maximum outside diameter of 90 mm. The test speed is load dependant, so could be between a maximum of 3000 rpm and a minimum of 120 rpm. The deflection is set to an accuracy of ±0.02 mm and initial test length of ±0.02 mm.

 

FM17                     This test machine is capable of testing springs up to 15000 N in load with a maximum stroke of 200 mm deflection, and can accommodate springs with a maximum free height of 600 mm and outside diameter of 300 mm. The test speed is load dependant, so could be between a maximum of 600 rpm and a minimum of 60 rpm. The deflection is set to an accuracy of ±0.02 mm up to 50 mm and ±0.05 mm over 50 mm; the initial test length is set to an accuracy of ±0.02 mm up to 300 mm and ±0.1 mm above 300 mm.

 

FM8                       This test machine is capable of testing springs up to 40000 N in load with a maximum stroke of 250 mm deflection, and can accommodate springs with a maximum free height of 600 mm and outside diameter of 300 mm. The test speed is load dependant, so could be between a maximum of 500 rpm and a minimum of 600 rpm. The deflection is set to an accuracy of ±0.02 mm up to 50 mm and ±0.05 mm over 50 mm; the initial test length is set to an accuracy of ±0.02 mm up to 300 mm and ±0.1 mm above 300 mm.

 

All test machines have a digital display of the number of cycles. During testing, an electrical circuit linked to the machine control system is created which incorporates the spring; if failure occurs, this circuit is broken, the test machine stops and the digital display shows the number of cycles at failure. The machines also stop when the maximum required number of cycles has been completed.

 

Once the test is completed, the results would be issued on a UKAS test certificate.


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