Fibre Rope Modeller (FRM)

PC based modelling software for rope design and performance prediction

FRM is an advanced suite of calculation and simulation modules, encompassed in a single computer program for use by engineers in the design or selection of synthetic fibre ropes. The modules are based on work performed by TTI for the US Navy and is intended to supplement or replace expensive prototype rope testing.

The FRM programs are presently available for use in two ways:

• TTI staff can perform analyses to meet the needs of rope makers and rope users.
• TTI can license the program for use by experienced rope engineers.

Use of FRM

When used during rope design and development, FRM replaces the time-consuming and expensive trial-and-error process of prototype rope production and evaluation. Alternative yarn properties and rope construction details can be input to predict important properties, for both new and cycled ropes. More precise predictions are achieved when FRM is "calibrated" against known properties of a similar "bench-mark" rope.

Comparison of predicted and measured rope test results can serve as a quality check to reveal errors during rope manufacturing. In addition to their immediate utility, the FRM programs can be enhanced to provide manufacturing information, costings, dimensions, and a range of rope properties for all types of rope, cord and cable, according to the needs of clients.

For ease of use, the program is split into a series of modules:

• FRM-I provides means for input of data on the yarn and rope construction.
• FRM-T predicts load/extension/torque/twist properties of twisted ropes.
• FRM-F predicts cyclic load performance, e.g. residual strength and cycles to failure.
• FRM-P predicts load/extension and cyclic load responses of parallel-yarn ropes.
• FRM-S covers features of twisted rope splice behaviour.
• FRM-B, for braided ropes, is planned for implementation when needed.

Mechanical properties of twisted ropes

FRM-T, using FRM-I for data input, is a highly developed and well validated rope analysis program, intended particularly for high-performance synthetic fibre ropes. It can model almost any form of twisted or laid rope construction, including: twisted yarns; simple 2-strand, 3-strand, and 4-strand structures; multi-layered ("wire-rope" form) ropes of 6, 18 or 36 strands; and parallel-strand ropes. FRM-T predicts the important mechanical properties of ropes: break load; load-elongation; torque-twist; and interaction of tension and twist. FRM-T accounts for friction and computes contact forces between components.

Long-term durability and effects of cycling

FRM-F quickly predicts changes in rope performance due to cycling over long service life, for example by wave action. With yarn creep property input, it gives good predictions of rope creep rupture. Relative but not absolute predictions can be made of some other effects, because data on relevant yarn properties is limited. It can be used to explore the following problems: heating due to dynamic losses in fibres and friction between fibres; internal abrasion due to components rubbing on one another; and "kink-band" failure when components suffer axial compression fatigue due to rope twisting or construction variability.

Example: Design of a 7-strand Aramid Rope
Load elongation	Torque Balance

Applications for FRM

Tension Technology International can now use FRM to provide advice to:

• Ropemakers on changes in rope properties which might result from new yarn materials or finishes or different rope construction details. 
• Fibre producers on the potential of new fibres or fibre finishes in rope applications. 
• Rope users, such as oil companies and civil engineers, on optimum choices and expected performance of high-performance ropes in critical situations. 
• Customised versions of the FRM program can be developed for use by ropemakers, fibre suppliers and rope users for their purposes in investigating rope design alternatives and rope performance. TTI can also provide training and useful yarn and construction input data.

To purchase FRM, contact TTI

Papers
Read a Technical Paper on Fibre Rope Modeller