Rubber pads used with mechanical or hydraulic jacks serve as critical safety components, providing load cushioning, surface protection, and anti-slip performance. Their compressive deformation characteristics directly influence lifting stability, structural safety, and overall service life. Understanding these properties is essential for developing optimized pad designs that balance strength, resilience, and durability.
Compressive Deformation Characteristics
Rubber is a hyperelastic material whose deformation behavior under load is nonlinear. When subjected to vertical compression from a jack:
1. Elastic Compression Zone
At low to medium loads, the pad exhibits recoverable elastic deformation. Its stress–strain response is strongly influenced by rubber hardness, modulus, and molecular network density. Higher hardness reduces compressive strain but increases localized stress.
2. Nonlinear High-Strain Zone
As load increases, deformation enters a nonlinear region where molecular chains stretch significantly. Excessive compression can cause lateral bulging, surface cracking, or internal shear stress concentration. Pads with insufficient thickness or improper geometry deform more rapidly in this stage, reducing stability.
3. Permanent Set or Structural Fatigue
Long-term or cyclic loading may lead to permanent deformation (compression set), loss of elasticity, and reduced grip. Factors such as rubber formulation, filler content, temperature exposure, and load frequency determine the rate of degradation.
Key Factors Affecting Compressive Performance
Rubber hardness: Higher hardness provides better load capacity but reduces surface conformability.
Geometric design: Pad thickness, footprint area, and rib/groove patterns significantly influence deformation and stress distribution.
Material composition: Reinforcing fillers such as carbon black can increase modulus and reduce creep.
Operating temperature: Rubber softens at high temperatures and becomes stiffer at low temperatures, affecting compressive response.
Optimization Design Solutions
1. Hardness–Thickness Coupling Optimization
Selecting appropriate hardness based on expected load is essential. For automobile jacks (1–5 tons), a hardness range of Shore A 70–80 combined with a thickness of 15–25 mm provides adequate deformation resistance without excessive stiffness.
2. Structural Reinforcement Using Layered Design
A multi-layer pad design—such as a soft upper contact layer bonded to a harder support layer—allows better friction at the interface while maintaining structural integrity. This reduces extreme bulging and prolongs service life.
3. Groove and Pattern Geometry Optimization
Adding cross grooves, honeycomb patterns, or ribbed textures helps improve anti-slip performance and distribute compressive stress. Finite Element Analysis (FEA) can identify optimal groove depth and spacing to minimize stress concentration.
4. Use of High-Resilience Rubber Compounds
Formulations using high-performance elastomers (e.g., NR/SBR blends, EPDM, or TPU-modified rubber) enhance elasticity and reduce permanent compression set. For heavy-duty industrial jacks, rubber reinforced with carbon black or silica improves load-bearing strength.
5. Anti-Bulging Edge Design
Chamfered or reinforced edges reduce lateral expansion under compression. Circular or rounded-corner pads distribute stress more uniformly than square pads, improving overall stability.
Conclusion
Optimizing rubber pad design requires balancing hardness, geometry, and material properties to control compressive deformation. By integrating layered structures, improved formulations, and optimized surface patterns, designers can significantly enhance load stability, safety, and durability in jack applications.
References
Gent, A. N. Engineering with Rubber: How to Design Rubber Components. Hanser Publishers.
ISO 7743 – Rubber, Vulcanized or Thermoplastic — Determination of Compression Stress–Strain Properties.
Rivlin, R. S. & Saunders, D. W. (1951). “Large Elastic Deformations of Isotropic Materials.” Philosophical Transactions of the Royal Society A.
Smith, J. (2020). “Mechanical Optimization of Elastomer Pads under Compressive Loads.” Journal of Elastomer Technology.
