PSI - Issue 42

5

Yahar Sarafraz et al. / Procedia Structural Integrity 42 (2022) 125–132 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The distance from specimens was considered by y = 219 mm to gain the same voxel size for all performed scans. The software Volume Graphics VGStudioMax 2.2 was applied to reconstruct the volume and measure the geometrical deviation of the friction drilled bores and formed threads from the nominal dimension. The experimental setups to conduct the tensile and fatigue tests are presented in Fig 4. The mechanical experiments were carried out at room temperatures on a servo-hydraulic testing system (Schenck PC63M, Instron 8800 control unit). The strength of the formed M6 threads was evaluated by axial tension of clamped M6 steel rods, which were engaged for four initial turns into the manufactured threads (L t = 4 mm).

Fig 4. (a) Tensile and (b) fatigue test setup coupled with NDT measurements (L t = 4 mm)

A strain rate of 2.5∙10 -4 1/s was chosen for the tensile tests and the test was stopped, when the abort criteria F = 10% F max was achieved. Continuous load increase tests were conducted to evaluate the cyclic properties of the front faced manufactured internal threads, influenced by various process parameters. A load ratio of R = 0.1 and a frequency of f = 10 Hz were chosen for the fatigue tests. The load amplitude started from the maximum load of F max,start = 0.5 kN and was then increased by dF max /dN = 0.5 kN/10 4 until failure. The measured change in deformation-induced temperature ΔT near the fourth thread was correlated with hardening and softening mechanisms according to changes in course of the plastic deformation until failure. Additionally, ACPD-method was used to correlate the crack initiation, propagation and contact surface reduction at threads flank to the change in potential. 3. Results Fig. 5 shows the CT scan of the friction drilled bore and formed thread in cross and longitudinal views.

Fig 5. CT scan of (a) friction drilled bores, (b) threads in cross sand longitudinal sections