. ▁The ▁model ▁is ▁based ▁on ▁Ron ald ▁Riv lin ' s ▁observation ▁that ▁the ▁el astic ▁properties ▁of ▁rub ber ▁may ▁be ▁described ▁using ▁a ▁stra in ▁energy ▁density ▁function ▁which ▁is ▁a ▁power ▁series ▁in ▁the ▁stra in ▁invari ants ▁ ▁of ▁the ▁C auch y - Green ▁de formation ▁tens ors . ▁The ▁Ye oh ▁model ▁for ▁in com press ible ▁rub ber ▁is ▁a ▁function ▁only ▁of ▁. ▁For ▁compress ible ▁rub bers , ▁a ▁dependence ▁on ▁ ▁is ▁added ▁on . ▁Since ▁a ▁polynomial ▁form ▁of ▁the ▁stra in ▁energy ▁density ▁function ▁is ▁used ▁but ▁all ▁the ▁three ▁invari ants ▁of ▁the ▁left ▁C auch y - Green ▁de formation ▁tensor ▁are ▁not , ▁the ▁Ye oh ▁model ▁is ▁also ▁called ▁the ▁reduced ▁polynomial ▁model . ▁ ▁Ye oh ▁model ▁for ▁in com press ible ▁rub bers ▁ ▁St rain ▁energy ▁density ▁function ▁ ▁The ▁original ▁model ▁proposed ▁by ▁Ye oh ▁had ▁a ▁cub ic ▁form ▁with ▁only ▁ ▁dependence ▁and ▁is ▁applicable ▁to ▁purely ▁in com press ible ▁materials . ▁ ▁The ▁stra in ▁energy ▁density ▁for ▁this ▁model ▁is ▁written ▁as ▁ ▁where ▁ ▁are ▁material ▁constants . ▁The ▁quantity ▁ ▁can ▁be ▁interpreted ▁as ▁the ▁initial ▁she ar ▁mod ulus . ▁ ▁Today ▁a ▁slightly ▁more ▁generalized ▁version ▁of ▁the ▁Ye oh ▁model ▁is ▁used . ▁ ▁This ▁model ▁includes ▁ ▁terms ▁and ▁is ▁written ▁as ▁ ▁When ▁ ▁the ▁Ye oh ▁model ▁reduces ▁to ▁the ▁ne o - H oo ke an ▁model ▁for