Answer
Load relaxation, or 'set', occurs when the internal stresses in the spring exceed the material's elastic limit during the first few cycles of compression. This results in a permanent reduction in the spring's free height. To ensure stable performance in the field, manufacturers often 'preset' or 'remove set' from the springs by compressing them to their solid height or the maximum operating deflection during production. This induces beneficial residual compressive stresses on the outer fibers. After presetting, the spring will maintain a constant load-deflection curve during subsequent cycles, provided the operating stress does not exceed the newly established elastic limit. This is critical for precision bearing preload applications where a constant force is required.
