Strain energy definition

Traditional definitions of safety factors in terms of strength requirements, such as load-resistance factors or allowable stresses, are not applicable in blast resistant design. Safety factors arc more appropriately measured in terms of strain energy demand versus strain energy absorption capacity, Allowable deformations arc a practical method to quantify energy absorption capacity. 

When using the generalised Hooke s law strain energy function there are a number of possible strain definitions that can be used depending on the situation. When material deformation is very small the infinitesimal strain approach is a valid approximation with the strain defined as... 

The heats of formation are not convenient quantities for comparing compounds having different numbers of carbons. Here, the strain energies are much more useful. The simplest definition is the difference between the observed AH and that calculated using a strain-free model. In the case of cyclopropane, AHf = 12.73 kcal mol If cyclohexane is taken as strain-free, the expected AHf for cyclopropane is one-half that for cyclohexane, or —14.75 kcal mol The difference is 27.5 kcal mol and is the strain energy. The strain-free model is frequently derived from Franklin s group equivalents, and for common hydrocarbon groups they are in kcal mol ... 

In order to have a positive definite strain energy density the conditions cited above demand that... 

This reaction may be identified as an acyclic counterpart of reaction 23 with X = CH2, and so the difference between the heat of this reaction and that of reaction 23 may be identified as the strain energy of cyclopentene. Using the data in Reference 12, we find the acyclic reaction to be endothermic by 4.4 kcal mol-1 and so the strain energy of cyclopentene is 4.4-( — 0.7) = 5.1 kcalmol-1 by the definition used in this chapter. 

The dissipation is a positive-definite quantity and represents the irreversible conversion of mechanical energy to thermal energy due to the action of fluid stresses. The remaining part of the stress work that goes into internal energy, — pdUj/dXj, represents reversible strain energy and can carry either sign. 

---