In order to make the phase field model better describe the brittle fracture process of materials. a polynomial degradation function is given in this paper. and the elastic limit stress and strain corresponding to the phase field model. the critical phase field value. https://www.roneverhart.com/HP-Pavilion-15-eg1053cl-15-6-FHD-Touch-Intel-Core-i5-1235U-3-30-GHz-Intel-Iris-Xe-Graphics-12-GB-DDR4-RAM-512-GB-SSD-/