Barragán Edú R, Ambriz Ricardo R, Frutos José A, García Christian J, Gómora César M, Jaramillo David
Instituto Politécnico Nacional CIITEC-IPN, Cerrada de Cecati S/N Col. Sta. Catarina, Azcapotzalco, Mexico City 02250, Mexico.
Materials (Basel). 2022 Jun 28;15(13):4553. doi: 10.3390/ma15134553.
The localized compressive deformation (LCD) effect generated by an indentation process at the crack tip on the fatigue crack growth of the 7075-T651 aluminum alloy is reported. Eccentrically loaded single-edge crack tension specimens (ESE(T)) were pre-cracked at a crack length of about 20 mm by applying a constant amplitude fatigue loading. Subsequently, the LCD process was performed by using a semi-spherical indenter with a radius of 16 mm to compress the crack tip zone at different forces (5.0, 7.0, 12.5, 13.5, 15.5 kN), applied on the opposite surfaces of the specimens. The fatigue cracking process was continued on the compressed samples until an overall crack length of about 30 mm was obtained. The compressive load and the number of delayed cycles is discussed in terms of crack length and crack tip opening displacement (CTOD). A direct relationship between the compressive force induced by the LCD process and the delay of the crack propagation due to the crack arrest was observed. This effect became evident at a compressive force of 5.0 kN, where the crack propagation was arrested for about 9000 cycles in comparison with the non-LCD sample. However, when the force increased, the crack arrest also increased. The crack was considered to be completely arrested at a compressive load of 15.5 kN, since the crack did not grow after the application of more than 3 × 10 cycles.
报道了7075-T651铝合金疲劳裂纹扩展过程中，裂纹尖端压痕过程产生的局部压缩变形（LCD）效应。通过施加恒幅疲劳载荷，在裂纹长度约为20 mm的情况下，对偏心加载的单边裂纹拉伸试样（ESE(T)）进行预裂纹处理。随后，使用半径为16 mm的半球形压头，在不同力（5.0、7.0、12.5、13.5、15.5 kN）下对试样相对表面施加压力，以压缩裂纹尖端区域，进行LCD过程。对压缩后的试样继续进行疲劳开裂过程，直至获得约30 mm的总裂纹长度。从裂纹长度和裂纹尖端开口位移（CTOD）的角度讨论了压缩载荷和延迟循环次数。观察到LCD过程引起的压缩力与裂纹止裂导致的裂纹扩展延迟之间存在直接关系。在5.0 kN的压缩力下，这种效应变得明显，与未进行LCD处理的试样相比，裂纹扩展在此处停止了约9000个循环。然而，当力增加时，裂纹止裂也增加。在15.5 kN的压缩载荷下，裂纹被认为完全止裂，因为在施加超过3×10个循环后裂纹不再扩展。
