Atlas Copco Aktiebolag

Other

Stefan M Skyllermark

Machine for press work

A method and apparatus for tightening a screw joint to a predetermined axial load F.sub.p providing the spring constant k=F/.phi. of the joint is known, wherein the joint stiffness or torque/rotation radient dM/d.phi. is calculated during the tightening process and the torque application on the joint is interrupted as a torque level M.sub.s is obtained that according to the spring constant or axial load/rotation relationship F/.phi. and the calculated joint stiffness dM/d.phi. corresponds to the predetermined axial load F.sub.p.

Method and apparatus for pretensioning screw joints

A method and apparatus for tightening a screw joint to a predetermined axial load F.sub.p providing the spring constant k=(F/.phi.) of the joint is known, wherein the torque/rotation relationship M (.phi.) is determined during the linear, elastic deformation part of the tightening process by calculating the joint stiffness (dM/d.phi.) at an arbitrarily chosen torque level M.sub.2. A theoretical, tensionless angular position .phi..sub.0 of the joint is calculated by extrapolating the determined torque/rotation relationship M (.phi.), and the tightening process is interrupted as an angular interval .DELTA..phi. from said theoretical, tensionless position .phi..sub.0 has been passed, which interval according to the spring constant k of the joint corresponds to the predetermined axial load F.sub.p.

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Nacka, Sweden

Stefan M Skyllermark