PSI - Issue 42

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

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2

Nomenclature RT

Room temperature f tf / f tc Thread forming/cutting feed v c,pd Cutting speed of pre-drilling v p,fd

Peripheral speed of friction drilling Feed speed of friction drilling Peripheral speed of thread forming

v f,fd v p,tf T-T C-C L-L

Transverse section

Cross section

Longitudinal section

Conical length of friction drill Cylindrical length of friction drill Volume of friction drilled bore in 4 mm

l con l cyl V fd L T

Length of thread engagement for fatigue and tensile tests

1. Introduction The mechanical properties of casting materials, which generally possess low static and dynamic properties, can be improved using proper manufacturing methods. Friction drilling (or flow drilling) as a chipless piercing method is applied to make a hole by pressuring a rotational tool with a triangular cross section into the workpiece (J.A. Geffen, 1976). In addition to martial saving advantages of the friction drilling process, bushing into the profile thickness t facilitates the threading of the sheets with more thread turns, which increases the length of thread engagement and results in stronger sheet metal joints consequently (Miller et al. , 2005; Timo et al. , 2010) (Fig 1a). The material at tool-workpiece interface will be sheared significantly by rotation and feed of the friction drill, which induces the positive work-hardening at the subsurface of the friction drilled bores. However, this work-hardening could be decreased due to heat generated by friction at the tool-workpiece interface during friction drilling (Miller et al. , 2005). It was indicated by Felinks et al. (2021b) that temperature can be increased to T = 704 K during the friction drilling of AlSi10Mg alloy.

Fig 1. Friction drilling (a) parallel and (b) perpendicular to the profile thickness, (c) thread forming and (c) cutting (Sarafraz et al. , 2021)