Purpose

These wiki pages will regroup information about practices to design Flexible tubes / hoses

it will contains sections for 

• Flexibletube routing UI usage
• Specific design use cases
• Management of Hose assemblies
• ...

Introduction

Generatilies

A flexible hose is a type of piping used to connect two distant points to transport or transfer fluid.

Hoses are used when there is a considerable relative movement at the 2 extremities

Normal Flexible hoses are made of non-metals like soft plastic material or synthetic rubber & they can have external reinforced metalic braid layers.

In some industry like chemical some of the hose used to absorb pipe movements are fully made of metallic materials.

Challenges

DESIGN: 

Design right at first time :  Better accuracy of 3D mockup ; having more realistic shape for Flexible tube taking into account external/internal conditions

• Tube internal conditions : tube material, internal fluid nature, pressure, temperature
• Tube external conditions / constrains : protection, support, end fitting 
• Mechanical environment : assembly motion, parts around (clash, contact)

SIMULATE :

Ensure that there is no risk (or anticipate) of hose rupture : Hose are design to ensure that they will resist to usage constrain all along the product life. In this context 2 main considerations must be taken at the design phase

• Position & Shape : The tube is at a sufficient distance from every other part in any condition (kinematic of the Wheel). 
• Working stress : Torsion,  Bending ...   

Values

Reduce design cost

• Powerful 3D flexible tube routing functions
• Integrated solution , no need of third party software

Reduce manufacturing cost :

• Less rework in shop floor
• Reduce number of physical prototype

Reduce maintenance cost

• Anticipate possible problem during product usage

Tubing design process & needs

Create Hose 

Designing flexible tube involves different step : 

• Select the system to work on
  • fluid, operating conditions (temperature, pressure)
• Selecting the good tube reference
  • sizes, material, minimum bend radius 
• Define the path of the tube
  • Extremity connections
  • Intermetiate fixed parts along the route (supports)
• Defining the the initial tube constrain
  • slack, length .
• Defining additional parts that are attached to the tube (follow the tube, not fixed)
  • protection, insulation
  • load parts

From this input the design tool should calculate the more realistic shape.

To do it, a pure geometrical mathematical computation is a good approximation but could not be sufficient ; in this case,  you need to have a calculation based on finite element simulation. 

To even be more precise in the tube shape, you need to take into account the external mechanical environment to be able to compute contact/clash and deform the tube accordingly

Bundles case

it can happens that hoses are routed alone but in many cases they are regrouped in bundle on some portion using strips and/or tape and/or protection.

In this case, in real life, the tubes will behave as a unique  flexible object which will have different property (resulting from each of the internal element). This case is very difficult to simulate because it request to know the physical properties of the bundle 

To increase the complexity for realistic simulation, Bundles can be composed on a mix of tubes and cables.

Constrain Elements

the increase complexity, the tube/bundle can be constrain along their rout by other external elements

Along the tube locally

The hose or bundle can go though different elements that will constrain it position and possible movement differently.

• A clamp support  will completely constrain the hose on a fixed element
  • the tube center curve is constrain by the point position
  • the length of the tube portion before and after will be always the same.
• a fixed guide will leave some degree of fredom
  • the tube center curve is constrain by the point position (port on the guide)
  • the tube can slide inside the guide --> the length of the tube portion before and after can change during the assembly motion.
  • 
• A strip will constrain the tubes between each other to create a bundle
  • strip position is following the tube
  • the length of the tube portion before and after will be always the same.
  • 
• Load parts, to force the tube to deform along gravity direction
  • load part position is following the tube centerline but it has an influence on the deformation 
  • the length of the tube portion before and after will be always the same.
  •  

On tube portion

Protection, insulation are additional layer put on top of the tube 

• it cover it on the total length or on portion.
• they have they own physical properties link the shape and material and they will increase the rigidity of the tube on this portion
• tube is not supposed to slide inside

At tube Extremities

Tube is fixed at its 2 extremities. there are different types of connections that will constrain the tube differently especially in torsion.

if the slack on the tube is not enough, it can generate some stress between the hose and the end fitting

The orientation of the end fitting can introduce some torsion on the flexible which generate also some stress. Some fitting allow to have a additional degree  of freedom in rotation (between the tube end and connected element) to minimize tube torsion. it is usually called "swivel" and it is a property of the connection 

CONCLUSION

We have seen that many element can influence the shape of a flexible hose.

A pure mathematical computation of the shape could be a good approximation in lots of cases but for some other, to  be able to have the more realistic shape of the tube in the DMU, it will be necessary to used a finite element solver that takes as inputs the tube physical properties and operating condition but also all attached elements

• This solver should be able to retrieve most of the information from the 3D design object and connections
• this solver is the prerequisite for more advance simulation at assembly / motion level (see next chapter)
• At the end we can have more or less complex assembly involving single of multiple tube 

3DEXPERIENCE CATIA Piping & Tubing 3D Design App capabilities

​​​ As of Today 2024, 3DEXPERIENCE CATIA Piping & Tubing 3D Design App 

• provides commande to route Flexible tube and compute the shape based on geometrical algorism
• provides commande to route a single Flexible tube and compute the shape based on physical tube properties and operating conditions ( temperature, pressure)
• doesn't provide advanced simulation solver that will allows to simulate precisely the deformation of a full tubing assembly network 
  • this should be managed with 3DEXPERIENCE SIMULIA tools