PSI - Issue 83

Sze Pei Tan et al. / Procedia Structural Integrity 83 (2026) 28–40

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significantly improved ductility compared to the as-built condition. Improved tensile strength generally increases resistance to crack initiation under cyclic loading, thereby prolonging fatigue life. At the same time, improved ductility contributes to increased plastic deformation capacity at the crack tip, which slows down crack propagation during cyclic loading. Overall, the combined tensile, fatigue life, and crack propagation results demonstrated that post-processing plays an important role in enhancing both crack initiation resistance and crack growth stability in DMLS-fabricated AlSi10Mg.

10 -4

data points power fit curve f(x) = 1.85E-09´•x 3.69

10 -7 Crack growth rate, da/dN ( m/cycles ) 10 -6 10 -5

10 -8

1

10

Stress intensity factors range,  K( MPa  m )

Fig. 9. Crack growth rate ( da/dN ) versus SIF range ( Δ K ).

In addition, the fractography of the CT specimen is observed Fig. 10. The crack grows at straight line after the pre-cracking at constant loading. The fracture surface at this region is more stable and smoother since no SHT is performed on the specimen. The crack starts to grow rapidly when the crack length reaches about half of the width. Notice the fracture surface at this region, the surface is uneven and rougher compared to the previous region. In addition, small shear lips are formed on both sides of the free surface demonstrating brittle fracture. Larger shear lips area means large plastic deformation thus indicating ductility behaviour. Therefore, the shear lips conditions need to be followed otherwise the experiment is invalid. In addition, the evaluation of the critical stress intensity factors ( K c ) is performed based on Eq.(1). The critical crack length ( a c ) is measured from the centre of the applied load to the location before the rapid crack growth. By substituting the all the information needed, the K c is computed and evaluated as 15.54 MPa √ m.