Journal Of Mechanics And Physics Of Solids

Posted onNovember 01, 2011 - 6:48 am by Admin | 0 Comments

Xuanhe Zhao 

Soft Active Materials Laboratory, Duke University, Durham, NC 27708

Journal of the Mechanics and Physics of Solids, In press 

Abstract 

Elastomers and gels can be formed by interpenetrating two polymer networks on a molecular scale. This paper develops a theory to characterize the large deformation and damage of interpenetrating polymer networks. The theory integrates an interpenetrating network model with the network alteration theory. The interpenetration of one network stretches polymer chains in the other network and reduces its chain density, significantly affecting the initial modulus, stiffening and damage properties of the resultant elastomers and gels. Double-network hydrogels, a special type of interpenetrating polymer network, have demonstrated intriguing mechanical properties including high fracture toughness, Mullins effects, and necking instability. These properties have been qualitatively attributed to the damage of polymer networks. Using the theory, we quantitatively illustrate how the interplay between polymer-chain stiffening and damage-induced softening can cause the Mullins effect and necking instability. The theory is further implemented into a finite-element model to simulate the initiation and propagation of necking instability in double-network hydrogels. The theoretical and numerical results are compared with experimental data from multiple cyclic compressive and tensile tests.

Link to the paper


If a finite element fretting wear model is based on a commercial software, it is fairly simple to add plasticity.  The plasticity model and constants can be input through the standard material parameters section of the finite element software.  There are four plasticity theories which have been primarily used to model fretting:

  1. elastic/perfectly-plastic (Amrico and Begley, 2000)
  2. isotropic strain hardening (Amrico and Begley, 2000)
  3. kinematic strain hardening (Amrico and Begley, 2000)
  4. viscoplastic plasticity (Dick et al., 2006)

Plasticity has three primary effects on the fretting contact:

  1. Shakedown
  2. Ratcheting
  3. Cyclic Plasticity

The magnitude of these material responses will vary based on the plasticity model selected and constants for that material.

Plasticity is more important when modeling fretting fatigue than when analyzing fretting wear.  However, it can add additional useful information when incorporated in wear modeling.  The jump in cycles procedure can still be applied to reduce computational time when including the effects of plasticity.

  • Ambrico, J.M., Begley, M.R., 2000, “Plasticity in fretting contact,” Journal of Mechanics and Physics of Solids, Vol. 48, pp. 2391-2417.
  • Dick, T., Paulin, C., Cailletaud, G., Fouvry, S., 2006, “Experimental and numerical analysis of local and global plastic behavior in fretting wear,” Tribology International, Vol. 39, pp. 1036-1044.
  • Mohd Tobi, A.L., Ding, J., Bandak, G., Leen, S.B., Shipway, P.H., 2009, “A study on the interaction between fretting wear and cyclic plasticity for Ti-6Al-4V,” Wear, Vol. 267, pp. 270-282.

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