11. Use multiple materials in Cables with DCableSegment Features

The identification tag for this tutorial is PDS-AAM. Input files for this tutorial are found in the folder named PDS-AAM in the provided tutorial input files.

11.1. Tutorial overview

This tutorial covers:

• Using multiple mooring line materials in a cable (e.g. chain and synthetic rope)

Fig. 11.1 Segmented cable schematic (Not to scale).

11.2. Initialize simulation

• Load the simulation files from the tutorial Simulate a subsurface mooring with a Cable. If the tutorial has not been completed, the input files can be downloaded here.

11.3. Import material libraries

Though a single Cable DObject is used, multiple cable segments will be applied to the Cable to represent chain, wire rope, and synthetic rope sections (see Fig. 4.2).

Material definitions will be imported from the external ProteusDS materials library.

• Download the ProteusDS materials library from the Beta Utilities page and extract the files.
• In PST, select the Configuration menu option along the top tool bar and select Import Feature(s) from External Library...
• Click Open and navigate to the extracted ProteusDS materials library folder.
• Open the Wire rope 6x19 lib library file.
• Select Wire_rope_6x19_1in in the left DCableSegment tree and click Import.
• The Wire_rope_6x19_1in library feature should look like the following:

//Library Version 1.0
//Source: Hanes Supply
//Grade/Type: 6x19 IWRC IPS
//Nominal Diameter (Inches) 1.000
//mass per unit length (pounds/foot) 1.850
//Nominal Strength (Tons) 44.90
 
//Fluid loading 
$CDc 1.5
$CDt 0.045
$CAc 1.0
 
//Mechanical 
$EA 3.547E+07
$EI1 1430.22
$EI2 1430.22
$GJ 1430.22
$Diameter 2.54E-02
$Density 5432.7
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0.0
$TCID 0.0
$CE 1
$BuoyancyDiameter 0.0
$MBS 4.40E+005

• Import the Dyneema_rope_18mm feature from the external Dyneema rope lib library file.
• The Dyneema_rope_18mm library feature should look like the following:

//Library Version 1.0
//Source: Samson Rope Catalogue
//Type: Amsteel Blue
//Nominal Diameter (manufacturer) 0.018
//mass per unit length (assumed dry state) 0.198
//elongation at 30% break 0.96
//Minimum breaking strength (kg) 26300
//Fluid loading 
$CDc 1.5
$CDt 0.045
$CAc 1.0
 
//Mechanical 
$EA 8.06E+06
$EI1 163.268
$EI2 163.268
$GJ 163.268
$Diameter 1.80E-02
$Density 778.1
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0
$TCID 0
$CE 0
$BuoyancyDiameter 1.60E-02
$MBS 258003

• Import the Chain_14mm feature from the external Chain studless grade 3 lib library file.
• The Chain_14mm library feature should look like the following:

//Library Version 1.0
//Source: Jeyco catalogue
//Grade: 3
//Nominal Diameter (manufacturer) 0.014
//mass per unit length (assumed dry state) 3.96
//Material Density 7800
//MBL (tonnes) 15.8
//Fluid loading 
$CDc 2.2
$CDt 1.15
$CAc 1.0
//Mechanical 
$EA 1.65E+07
$EI1 0
$EI2 0
$GJ 0
$FluidDiameter 0.014
$Diameter 0.025
$Density 7800
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0
$TCID 0
$CE 0
$MBS 1.548E+05

The cable segment properties will be specified starting from node 0. This means that the first cable segment property will start at node 0 of the cable and run the unstretched length specified. The second segment listed will then be applied from the end of the previous segment for the length specified.

• Ensure that $CableSegmentMode 1 is set in the Cable_1 input file. Also, ensure any $CableSegment declarations are removed.
• Open the Cable state generator.
• Change the default segment type to Dyneema_rope_18mm segment with an unstretched length of 5 m and 5 elements.
• Add a new segment After the Dyneema_rope_18mm segment.
• Change the segment type to Wire_rope_6x19_1in and give it an unstretched length of 15 m with 3 elements.
• Add a new segment After the Wire_rope_6x19_1in segment.
• Change the segment type to Chain_14mm and give it an unstretched length of 5 m with 2 elements.

Fig. 11.2 Cable segments list

Material properties are constant for each cable element and are defined completely by the DCableSegment feature (e.g. rope and chain features in this example). The cable segments also start and end at nodes.

11.4. Running the simulation and processing results

• Use the existing environment settings.
• Run the simulation.
• View the results in PostPDS.

Note

• In engineering view with Show element nodes activated, the node that demarcates the change in element material properties are indicated.

Fig. 11.3 Segmented Cable in PostPDS