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Compressive strain behaviour

The compressive strain behaviour of cellular Vulkollan® is determined by its chemical structure, its density and the shape of the specimen. From the compression load/deflection diagram illustrated in Fig. 24, a number of points emerge :

• The higher the density, the higher the energy absorption.
• At below approx. 35% deflection, compressive stress is roughly proportional to deformation as is the case with frictionless metal springs.
• When the deflection exceeds about 35%, the force needed to produce further deformation increases progressively.

Another highly significant fact is that the compressive strain behaviour at up to approx. 50% deflection remains practically constant over temperatures ranging from about + 20 °C to + 80 °C (cf. Fig. 26).

Figs. 27 and 28 show that the properties of cellular Vulkollan® change only gradually even under long-term dynamic loading. Whether at room temperature or at + 80 °C, the spring characteristic is always found at the same level, and is therefore a calculable factor. Fig. 29 shows that even after 10⁶ compressions of 60%, permanent set only amounts to about 3.5%.

With this exceptional resilience, cellular Vulkollan® can be used to design smaller, lighter springs giving reliable, long-term functional performance.

Fig. 24: Compression load / deflection diagram of cellular Vulkollan® at 23°C obtained using a cube with 40 mm edges; deflection rate 50 mm / min

Fig. 25: Compressive stress values obtained using a cube with 40 mm edges; deflection rate 50 mm / min

Fig. 26: Compression load / deflection diagram at various temperatures; density 505 kg / m3; deflection rate 20 mm / min

Fig. 27: Compression load / deflection diagram of a spring element at 23°C; density 500 kg / m3; deformation 60%; test frequency 2 Hz

Fig. 28: Compression load / deflection diagram of a spring element at 80°C;density 500 kg / m3; deformation 60%; test frequency 2Hz

Fig. 29: Permanent set as a function of degree and frequency of deformation at 23°C

Fig. 30: Torsion pendulum test to DIN 53445

Fig. 31: Torsion pendulum test to DIN 53445