The Influence Of Cable’s Local Bending Effect Force To Cable Tension Measurement

Wire rope is important part in special equipment and the key part of crane elevator in our country(elevator and crane number accounts for over 50% of the national special equipment amount), and also is an important part of a mine hoist. In the coal system, wire rope broke accident after flooding and gas accident, ranking the third. Wire rope fracture accidents have occurred frequently, the lack of reliable wire rope safety inspection and evaluation standards is an important reason. Tension detection is an important part of wire rope safety assessment. Mechanics principle of wire rope’s stretch and bending is the theoretical base of tension measuring method by three rounds bending. Through the theoretical derivation and experimental study of model of stretch bending, this research obtained some new conclusions, and the more simple measurement method.First, the theoretical research. Started with the deflection differential equation of stretch bending, bending deformation equation of simply supported beam under tension is deduced. And simplified the balance equation, then got tension measurement formula which has a simple form relatively. This formula could response difference between the two kinds of beams, one under the tensile force and the other without tension.Second, verified derived formula by the two aspects of numerical calculation and experiments. On the basis of the theoretical derivation, simulated the stretch bending process of equivalent beam model of steel wire rope with FEA software and got conclusion that the force is still linear relationship with displacement in the process of stretch bending. And, by constructing auxiliary platform in the universal tensile testing machine, completed the wire rope stretch bending simulation test, validated the theoretical solutions. The experiment proved that, for one cable, the calculated value of k has a stable linear relationship with tension S in the steel wire rope. The conclusion opens up a new way for wire rope tension measurement and qualitative research.Third, designed and manufactured a set of modular wire rope tension measure-ment instrument. The equipment is constituted of movable pressure head driven by screw and support roller parts provided variable span. The instrument measured the pressure data by the pressure sensor. The data showed by the strain gauge, and recorded by manual. According to the number of turns of screw rotation, Recorded the relative displacement at the same time. Online prototype test proved that, the instrument can reliably measure the internal tension of wire rope while only span is in a certain range.Last, the new tension measurement method simplified the process of tension measuring. One measurement only needs one bending, recorded displacement and force in the process of bending; the tension of wire rope can be calculated through the values of displacement and lateral load.