WELDING RESEARCH AW-6060 tubes in the T66 condition with an outer diameter of 40 mm (1.574 in.) and a thickness of 1 mm (0.039 in.) and 1.5 mm (0.06 in.). The static yield stress of the material was 222 MPa (32.2 ksi), determined by tube tensile tests. The base material was a cylinder of C45-grade steel with a diameter of 33 mm (1.3 in.). The chemical compositions of the aluminum and steel alloys are given in Tables 1 and 2. Both the flyer and base material were used in an uncoated, unpolished state; the measured roughness average Ra of the parent parts was approximately 2 m (7.9e–5 in.). An abrasive cleaning followed by ethanol wash were used to remove oxides and debris from the workpiece surfaces. Single-turn coils made of a CuCrZr alloy with maximum working zones lcoil of 10 mm (0.39 in.) and 15 mm (0.59 in.), and an inner diameter of 42 mm (1.65 in.) were used for forming. The coils have an asymmetric 45- deg tapered cross section to facilitate the positioning of the parts to be joined — Fig. 3. The coils were designed to be able to conduct photon doppler velocimetry (PDV) measurements of flyer deformation by integrated PDV collimators. Holes bored radially in the coil and at a 90-deg offset allow the small-sized collimator probes (outer diameter 2.5 mm/0.1 in.) direct access to the flyer’s outer surface, which is a requirement for the application of PDV measurements during MPW. The basics of this heterodyne method were described by Strand et al. (Ref. 14). This reference contains an indepth description of the PDV measurement principle and system properties. A 1000-mW RIO GrandeTM fiber laser module (Redfern Integrated Optics, Inc.) was used to generate the required laser beam with a wavelength of 1550 nm. In Ref. 15, a detailed report on the features of the applied PDV system used within this analysis is presented. The maximum velocity that can be MARCH 2016 / WELDING JOURNAL 103-s A B Fig. 4 — A — Flow stress of the used flyer material depending on the strain rate; B — free tube compression, comparison of final necking. A B Fig. 5 — Overview of welding results with images of samples pulsed at constant energy for various working lengths. A — 15mm coil; and B — 10mm coil. Impact areas are marked by dashed lines. Table 2 — Steel C45 (1.0503) Alloy Composition (by wt%) (Ref. 13) C Mn P S Si Ni Cr Mo Cr + Mo + Ni C45 0.42–0.5 0.5–0.8 0.045 0.045 ≤0.4 0.4 ≤0.4 ≤0.1 ≤0.63
Welding Journal | March 2016
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