Material characteristics
       Establishment of the behaviour laws
       Finite element calculations
       Production of prototype parts
       Validation simulation/bench testing

Rubber and plastic parts calculations are performed with the aid of two principal commercial programs adapted to this type of simulation: ABAQUS and MARC.

CALCULATION APPROACH

Numerical simulation permits a reduction in cost and delay in the conception or modification phase of parts. The calculations permit a response to various approaches while the material and geometric parameters can be changed more easily than in the case of a prototype part :

This type of approach is used in all the activity sectors (aeronautical, automotive, energy transportation, medical, recreation, etc.) for plastic and rubber parts. The frequently addressed questions concern the following topics:

       Mechanical behaviour under static load (force, displacement, pressure, contact, etc.)
       Relaxation or creep
       Change in thermal behaviour (changes in stiffness, dilatation)
       Sealing (joint contact pressure, behaviour of bellows, membranes, etc.)
       Ageing forecasting (time/temperature equivalence)
       Behaviour in steady state dynamic mode

EXAMPLES OF CALCULATIONS

Static sealing: four-lobe joint Simulation of the fitting of a lobe joint in its groove permits determination of the contact pressure generated by the joint in order to determine the degree of sealing. The calculation can take into account the influence of the operating temperature in order to check the free volume remaining in the groove at high temperature. One can also take into consideration the pressure exerted by the fluid on the joint and observe the phenomena of extrusion of the joint in the groove.

Behaviour in the dynamic regime: rubber/metal joint For this type of part, used for example in vehicle anti-roll bars, it is possible to calculate the static stiffnesses (radial stiffness, stiffness in torsion, etc.) as well as the dynamic stiffness. As an example, we show the transmissibility curve calculated for a coil radially loaded at 1000 N and excited by an amplitude of +/-250 µm.