Technical Specification: 

- Specimens    : two spring coils cut from passenger car suspension springs 
- Gripping in the machine : between tips 
- Wire diameter : d < 22 mm 
- Spring diameter : Dm = 40 to 320 mm 
- Test frequency : low speed: f = 0.2 to 1.0 Hz 
                   high speed:f =   8 to 60  Hz 
- Environment  : normal room conditions or tempered salt spray 
- Weight without control panel : 1,000 Kg 
- Dimensions without control panel : L=1,200mm, W=1,100mm, H=1,600mm 
- Load signal : constant amplitude or spectrum loading 
- Set-up time for a single test 
- Power consumption : < 1 kW 
- Installation : no variation, very low noise level 
 
Purpose of Testing:  

Comparative assessment of fatigue strength. The types of tests listed below cannot be carried out on complete springs, at least not at low costs and in a short time. Tests on individual spring coils result in 40% higher stresses compared to the same stroke applied to a coil in the complete spring. 

- Investigation of surface protection, precorrosion and corrosion during fatigue testing (realistic testing conditions) 
- Determination of the testing frequency on fatigue life under corrosion 
- Determination of material, heat treatment, shot peening, pre-setting, surface quality, surface protection etc. 
- Determination of the influence of mean stress (loading of the car) 
- S-N curves 
- Scatter in the infinite and finite life region 
- Investigation of life prediction, methods (damage accumulation) by spectrum testing 

Typical test results of an S-N-test: