Abstract:A new non-quadratic orthotropic yield function describable anomalous behavior of materialshas been put forward,which like the yield function raised by Hill recently.has no limitations possessed by the previous similar functions.It is simple and clear,especially.all the n'iaterials constants involved can be determined using only unaxial tension test.Therefore,this function ismore convenient to use.The application of this function to 1100 aluminium sheets indicates thatthe 1100 aluminium alloy is a material possessing anomalous behavior and the reasonable powervalue of its yield function is about 1.68.Most deviations between the calculated values using thisfunction and the experimental data of flow stresses are smaller than 4 percent.

Key words: orthotropy anomalous behavior non-qudratic yield function