Control of Bending Characteristics

The parts to be knuckled are bent by a bending tool. The characteristics of the bending tool, like radius and stretching compensations, may be set up in a so called knuckle control file, described in this paragraph.

The file is an ordinary ASCII text file and its full file specification must be assigned to the environment variable SBH_KNUCKLE_CTRL.

The file is built up in the following way:

• It must always start with a TYPE statement defining the connection type code, for example, TYPE=45 (this is type of connection that is supposed to be defined in the boundaries of subpanels along knuckle lines).

• Directly after the TYPE statement must follow a RADIUS statement defining the bending tool radius, for example, RADIUS=30.

• Then there must follow at least one so called thickness group. It starts with a THICKNESS statement giving the maximum thickness up to which (and including) the following parameters are valid, for example, THICKNESS=10.

The parameters within a thickness group define stretch compensations as a function of the knuckle angle (according to the experience of the individual yard). The values are given two by two and define a knuckle angle up to which (and including) the following stretch compensation should be applied for the current thickness. The number of pairs is not limited but the knuckle angle must be ascending. The pair of parameters belonging to one thickness group is interrupted by a new thickness group within the same connection type, by a new connection type or by the end of the file. Thickness groups within one connection type must be sorted in ascending thicknesses.

The compensation is used in the following way. The nominal size of the plate is considered to be the length of the neutral line (plane) in the bending. This plane is supposed to be located in the middle of the plate. The length of this line is calculated automatically taking the bending radius into consideration and independent of the size of the subpanels when generated (for example, in case there happen to be gaps or overlaps). The compensation will add to the nominal size of the plate if positive, reduce its size if negative. that means, in a case where the bending is found to cause a uniform stretching in the bend the plate will become too big compared to the nominal length of the neutral plane and the compensation should be negative.

If the bending type is omitted when generating the boundaries of the subpanel the type will be set to 9999, that means, the default bending type is 9999. If there is only one type of bending the connection type need never be given, it is enough to indicate a connection across that bounding.

The file may be checked for correctness by a subfunction of the hull utility inithull. If it is not correctly built up, the check will identify the line where the first error occurs. The file should then be corrected and the check rerun until the file is found to be correct.