Torsional and Pinching Dynamic Characteristics Testing of Rubber Vibration Isolators [JIS K6385]

Importance of the Topic

Rubber vibration isolators play a critical role in reducing noise, shock, and vibration in applications ranging from automotive engines to industrial machinery. Accurate evaluation of their dynamic properties in torsional and pinching modes is essential to ensure durability, comfort, and safety under real-world operating conditions. Following standardized methods such as JIS K6385 helps manufacturers and test laboratories achieve reproducible and comparable results.

Study Objectives and Overview

This work demonstrates dynamic characteristic testing of cylindrical rubber vibration isolators in both torsional and pinching directions according to JIS K6385. The primary goals were to measure frequency-dependent properties from 3 to 20 Hz using a frequency sweep method, and to extract key parameters including spring constants, damping, and loss factors for both test modes.

Methodology and Instrumentation

Test specimens were off-the-shelf cylindrical rubber isolators conforming to JIS K6386 Type A (outer diameter 33 mm, inner diameter 14 mm, length 31 mm). Tests employed a combined axial force and torsion testing machine capable of simultaneous control of axial preload and rotational excitation. Frequency sweep excitation (sine wave, ±5° amplitude) was applied from 3 to 20 Hz at room temperature (24 °C). Dedicated jigs enabled quick switching between torsion and pinching configurations. Data acquisition and analysis were automated using frequency sweep and resonance tracking software.

Použitá instrumentace

• Axial Force and Torsion Testing Machine EHF-EV100 kN/TV 1 kN·m
• Torsional and pinching dedicated jigs
• Biaxial small-capacity load cell 10 kN/100 N·m
• Frequency sweep and resonance tracking software

Main Results and Discussion

Cycle peak and time waveform analyses revealed that torsional torque increased with excitation frequency, whereas pinching torque remained essentially frequency-independent. Torque-angle hysteresis loops showed larger energy dissipation variation in torsion than in pinching across the tested range. Using JIS K6394 formulas, dynamic parameters were calculated:

• Absolute spring constant (K*) and storage spring constant (K′) varied modestly in torsion but more significantly in pinching tests.
• Loss spring constant (K″) and damping factor (c) exhibited similar frequency trends for both modes.
• Loss factor (tan δ) in torsion showed strong frequency dependence, while pinching loss factor remained stable.

Benefits and Practical Applications

The combined machine and automated frequency sweep software allow rapid, repeatable assessment of dynamic isolator behavior under realistic load directions. Manufacturers can optimize material formulations and geometry for specific vibration profiles. Quality control laboratories gain a standardized, efficient method for batch verification.

Future Trends and Possibilities

Emerging developments may include integration of resonance-tracking in real time, expansion to international standards such as ISO 4664-1, and incorporation of smart sensors for in-service monitoring. Advanced data analytics and machine learning could further correlate test results with field performance and predict fatigue life.

Conclusion

This study illustrates the effective use of a combined axial-torsion tester and frequency sweep method to characterize rubber vibration isolators per JIS K6385. The approach provides comprehensive insight into frequency-dependent stiffness, damping, and energy loss in both torsional and pinching modes, supporting improved product design and quality assurance.

References

• JIS K6385-2012 Rubber Vibration Isolators – Testing Methods
• JIS K6394-2007 Rubber, Vulcanized or Thermoplastic – Determination of Dynamic Properties – General Guidance