the microscopic plastic deformation of the local crazes cause the change of crack opening loads . therefore, the fatigue crack closure concept could be introduced . a crack closure model of mdyb-3 pmma were recommended and phenomenologically formulated for positive and negative stress ratios separately, according to the testing results of fatigue crack propagation 本文討論了有機(jī)玻璃疲勞裂紋擴(kuò)展機(jī)理,提出,銀紋的形成是裂紋形成和擴(kuò)展的基礎(chǔ),從微觀上解釋了裂紋形成和擴(kuò)展的原因,并結(jié)合金相分析結(jié)果,明確提出塑變誘導(dǎo)閉合和粗糙誘導(dǎo)閉合是有機(jī)玻璃疲勞裂紋面閉合的兩個(gè)主要原因,成功的解析了裂紋面的閉合現(xiàn)象。