6. Conclusion

For heavily loaded assemblies, we recommend using bolts of quality classes 8.8, 9.8, 10.9, 12.9.

It's good to remember:

• that these screws are highly resistant to static loads (R _m ≍ 1,000 MPa), which means they can be used to install high levels of prestressing;

• that they have very low fatigue strength (40 to 60 MPa) and that the assembly should be designed and dimensioned to ensure that stress variations in the screw are low;

• that the uncertainty over the installed prestress is always great (with a torque wrench, we have Q _min < Q _real < 1.5 Q _max ) and that...