带中心孔的钛合金扩散连接层合板裂纹扩展特性

FATIGUE CRACK GROWTH CHARACTERISTIC FOR DIFFUSION BONDED LAMINATES OF TITANIUM ALLOY WITH CENTERED HOLE

  • 摘要: 为了研究含孔TC4钛合金扩散连接层合板的裂纹扩展行为,进行了含ϕ6中心孔的8mm厚单层板材、三层(3+2+3)扩散连接层合板和三层(3+2+3)含ϕ12止焊区扩散连接层合板的疲劳对比试验,试验中施加标识载荷,通过断口判读裂纹形态和尺寸,得到裂纹扩展(a,N)数据,建立了裂纹扩展da/dN-a曲线,对单层板、层合板和止焊层合板的裂纹扩展行为和规律进行了对比。结果表明:单层板出现规则的半椭圆形孔壁裂纹;层合板由于存在层合界面的影响,出现不规则的半椭圆孔壁裂纹;而止焊层合板以角裂纹为主,裂纹扩展过程分为三阶段;三类试件的da/dN-a曲线可用双对数线性关系描述;三层板的裂纹扩展特性不弱于单层板;止焊层合板的裂纹扩展性能有明显改善,提高了含孔层板的损伤容限特性。

     

    Abstract: To investigate the crack growth characteristics of diffusion bonded (DB) laminates of TC4 titanium alloy with ϕ6 centered hole, the reduplicated fatigue tests for 8mm thick TC4 plate, three-layer DB laminates and three-layer DB laminates with localized ϕ12 no-welded area were conducted under the constant amplitude fatigue stress inserted periodically with marker load. The crack growth (a, N) data were obtained by quantitative fractography. The analysis on the failure surface shows that the typical semi-elliptic surface crack are found for the 8mm plate; the untypical semi-elliptic surface crack for the 3-layer DB laminate; the corner quarter-elliptic crack for the localized no-welded DB laminate whose crack growth could be divided to three phase. The comparison on the da/dN-a curves of those coupons shows that the crack growth characteristic of the DB laminate has no difference with the 8mm thick plate, while the localized ϕ12 no-welded area decreases the crack growth rate and improves the damage tolerance property of the DB laminate.

     

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