Specimens ’ cracking load under dead - load , fatigue failure characteristic , fatigue life , deflection of span - centre , fatigue flexural rigidity , maximal crack width , development of cracks and strain of concrete and steel bars have been investigated . the influence of fatigue cycle characteristic , ratio of reinforcement , kinds of aggregate and concrete compressive strength on the specimens ’ fatigue behavior has been also investigated 对试件的静载下开裂荷载、疲劳破坏特征、疲劳寿命、疲劳荷载作用下的跨中挠度、截面疲劳抗弯刚度、裂缝开展情况及最大裂缝宽度、钢筋及混凝土在循环荷载作用下应变等内容进行了研究,分析了疲劳循环特征值、纵筋配筋率、骨料种类、混凝土抗压强度等因素对试件疲劳性能的影响。
Powder metallurgy turbine disks are worldwide adopted in most advanced aeroengine nowadays . the research of engineering application of them is actively being carried out in our country , and the key problem urgently needed to solve is their low cycle fatigue life prediction . the low cycle fatigue failure of powder metallurgy turbine disks is mainly caused by inclusions , so it ' s important to study the effect of inclusion on the stress intensity factors ( sif ) initiation and development of crack in powder metallurgy turbine disks 当前世界上大多数先进航空发动机均采用了粉末冶金涡轮盘，我国目前正在积极开展粉末冶金涡轮盘的工程应用研究，其低周疲劳寿命预测成了亟待解决的关键问题，夹杂物是引起其低周疲劳失效的主要原因，因此开展夹杂物对粉末冶金涡轮盘应力强度因子及裂纹萌生与扩展的影响具有重要意义。
Comparison of stiffness , strength and obturating performance of the initial obturator of the breech mechanism with those of the optimized one is made , which indicates that the stress concentration that leads to fatigue failure in the optimized structure is eliminated . the flexibility of the optimized obturator of the breech mechanism is considerably increased and its obturating performance is substantially improved 对优化前后炮闩闭气结构刚强度和闭气性能进行了对比，优化后的结构应力集中问题得到了有效控制，消除了潜在的疲劳源，结构的柔性得到很大程度的提高，闭气性能有了明显改善，实现了优化的目的。
