초록 ▼

A truing operation for straightening out of true work pieces such as crankshafts, must not again reduce the fatigue strength of the work piece achieved in a previous strengthening operation. This is achieved by a truing operation, wherein locally bounded compressive residual stresses are induced in

A truing operation for straightening out of true work pieces such as crankshafts, must not again reduce the fatigue strength of the work piece achieved in a previous strengthening operation. This is achieved by a truing operation, wherein locally bounded compressive residual stresses are induced in a surface layer zone of the work piece by a hardening operation, whereby the respective out of true deformation of the work piece is at least reduced. The truing operation is repeated until the out of true deformation is eliminated. The compressive residual stresses are induced in a surface layer zone of the work piece by a locally limited hardening operation, e.g. a surface strengthening rolling operation. By appropriately varying the extent of hardening or the rolling force respectively, any out of true deformation may be even completely eliminated. A machine for performing the method is also disclosed.

대표청구항 ▼

A method for straightening a work piece having cross-sections along its length with fillets forming transition areas between neighboring cross-sections, said cross-sections having a work piece diameter (D1), said work piece having a rotational axis and a bend relative to said rotational axis, said b

A method for straightening a work piece having cross-sections along its length with fillets forming transition areas between neighboring cross-sections, said cross-sections having a work piece diameter (D1), said work piece having a rotational axis and a bend relative to said rotational axis, said bend being determined by three values, namely as to its location by an axial coordinate value, as to its direction by an angular coordinate value, and as to its size by an eccentricity magnitude value, comprising the following steps: (a) first introducing into said fillets of said work piece first residual compressive stresses in a complete circumferential surface layer for increasing a fatigue strength of said work piece, (b) determining from said three values a respective control signal which represents a circumferentially limited angular range (b5°to about 160°around a portion of at least one of said fillets requiring the introduction of further residual compressive stress for said straightening, and (c) second introducing additive second residual compressive stresses in response to said control signal, for adding said second residual compressive stresses to said first residual compressive stresses only in said range (b2) substantially smaller than said work piece diameter (D1) by applying to said rolling tool a straightening force only in said limited angular range (b3) short of a depth where said second residual compressive stresses tend to become subtractive, for increasing said first residual compressive stresses by said second residual compressive stresses only in said limited angular range (b