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高强钛合金(Ti—10Mo—8V—1Fe—3.5Al)薄扳K_(IE)值的测定,从实验工艺以及材质的强度和板厚对测试K_(IE)值的影响进行了探讨。实验工艺要求能控制疲劳裂纹的生长长度。同一厚度的薄板,材质的强度愈高,符合平面应变测试K_(IE)值的力学条件逐渐增加,即是断口“平断”部份的面积增加,直至整个断口几乎全部为“平断”外貌。中强或略偏高材质只有达到一定的临界厚度才能测定稳定的K_(IE)值。判断K_(IE)值的条件:一方面大致根据断口“平断”面积与整个断口面积比例;另一方面采用定量地计算Irwin塑性区域尺寸与其韧带宽度之比值。薄板钛合金该比值≤13%,才能称K_(IE)值,即是要求板厚B≥1.7((K_(IE))/(σ_(0.2)))~2;更苛刻的要求是比值≤10%,相应板厚B≥2.0((K_(IE))/(σ_(0.2)))~2。根据实验,本文钛合金其比值≤15%较合适,B≥1.5((K_(IE))/(σ_(0.2)))~2。
The determination of the K_ (IE) value of the thin plate of high strength titanium alloy (Ti-10Mo-8V-1Fe-3.5Al) was discussed from the influence of the experimental process, the strength of the material and the thickness of the plate on the K value. Experimental process requirements can control the growth of fatigue crack growth. For the same thickness of thin plate, the higher the strength of the material, the more the mechanical conditions conforming to the K_ (IE) value of the plane strain test increase, that is, the area of the “broken” part of the fracture increases until almost all of the fracture is “broken” . Medium or slightly high material can only reach a certain critical thickness in order to determine the stability of the K IE value. Judgment of the value of K IE: on the one hand, roughly based on the fracture area and the fracture area ratio; the other hand, the quantitative calculation of Irwin plastic zone size and the ratio of its ligament width. The ratio of the thin plate titanium alloy is less than or equal to 13%, so it can be called the value of K IE, that is to say, the plate thickness B ≥1.7 ((K_ (IE)) / (σ_ (0.2))) 10%, corresponding plate thickness B≥2.0 ((K_ (IE)) / (σ_ (0.2))) ~ 2. According to the experiment, the ratio of titanium alloy is less than 15%, B≥1.5 ((K_ (IE)) / (σ_ (0.2))) ~ 2.