### Abstract

Many models use the equilibrium stress, also sometimes known as the back stress, in characterizing the response of both polymeric and non-polymeric materials. We study the characteristics of the equilibrium and show that the tangent modulus and local Poisson's ratio at equilibrium both are rate independent for common modeling assumptions. This fact is used to propose a method based on uniaxial tension or compression to measure the equilibrium stress, and the associated point's tangent modulus and local Poisson's ratio. The method is based on cyclic loading and identification of similar states with vastly different loading rates. The method is used to characterize the equilibrium stress in glassy polycarbonate, and the results are studied in regard to the possible error for such a measurement. The method is faster than most other proposed methods for calculating the equilibrium stress, and provides additional measurements of parameters at equilibrium that are normally not obtained.

Original language | English (US) |
---|---|

Pages (from-to) | 709-716 |

Number of pages | 8 |

Journal | Proceedings of the Society for Experimental Mechanics, Inc. |

Volume | 67 |

State | Published - Dec 1 2010 |

### Fingerprint

### Keywords

- Back stress
- Compression
- Cyclic loading
- Equilibrium stress
- Error analysis
- Glassy polymers
- Local Poisson's ratio
- Polycarbonate
- Tangent modulus
- Uniaxial testing

### ASJC Scopus subject areas

- Mechanics of Materials
- Mechanical Engineering

### Cite this

*Proceedings of the Society for Experimental Mechanics, Inc.*,

*67*, 709-716.

**Experimentally evaluating equilibrium stress in uniaxial tests.** / Goel, A.; Strabala, K.; Negahban, M.; Feng, R.

Research output: Contribution to journal › Article

*Proceedings of the Society for Experimental Mechanics, Inc.*, vol. 67, pp. 709-716.

}

TY - JOUR

T1 - Experimentally evaluating equilibrium stress in uniaxial tests

AU - Goel, A.

AU - Strabala, K.

AU - Negahban, M.

AU - Feng, R.

PY - 2010/12/1

Y1 - 2010/12/1

N2 - Many models use the equilibrium stress, also sometimes known as the back stress, in characterizing the response of both polymeric and non-polymeric materials. We study the characteristics of the equilibrium and show that the tangent modulus and local Poisson's ratio at equilibrium both are rate independent for common modeling assumptions. This fact is used to propose a method based on uniaxial tension or compression to measure the equilibrium stress, and the associated point's tangent modulus and local Poisson's ratio. The method is based on cyclic loading and identification of similar states with vastly different loading rates. The method is used to characterize the equilibrium stress in glassy polycarbonate, and the results are studied in regard to the possible error for such a measurement. The method is faster than most other proposed methods for calculating the equilibrium stress, and provides additional measurements of parameters at equilibrium that are normally not obtained.

AB - Many models use the equilibrium stress, also sometimes known as the back stress, in characterizing the response of both polymeric and non-polymeric materials. We study the characteristics of the equilibrium and show that the tangent modulus and local Poisson's ratio at equilibrium both are rate independent for common modeling assumptions. This fact is used to propose a method based on uniaxial tension or compression to measure the equilibrium stress, and the associated point's tangent modulus and local Poisson's ratio. The method is based on cyclic loading and identification of similar states with vastly different loading rates. The method is used to characterize the equilibrium stress in glassy polycarbonate, and the results are studied in regard to the possible error for such a measurement. The method is faster than most other proposed methods for calculating the equilibrium stress, and provides additional measurements of parameters at equilibrium that are normally not obtained.

KW - Back stress

KW - Compression

KW - Cyclic loading

KW - Equilibrium stress

KW - Error analysis

KW - Glassy polymers

KW - Local Poisson's ratio

KW - Polycarbonate

KW - Tangent modulus

KW - Uniaxial testing

UR - http://www.scopus.com/inward/record.url?scp=79960045186&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79960045186&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:79960045186

VL - 67

SP - 709

EP - 716

JO - Proceedings of the Society for Experimental Mechanics, Inc.

JF - Proceedings of the Society for Experimental Mechanics, Inc.

SN - 1046-6789

ER -