PSI - Issue 23

C. Skotarek et al. / Procedia Structural Integrity 23 (2019) 463–468 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2. Material and experiments The pins used were provided by Soehnergroup 1 , Type FlexxPin (see Fig. 3a). They were inserted into a printed circuit (type IT 180 provided b y Göttle 2 ) at a loading rate of 50mm/min with the load-displacement curves carefully recorded. An hourglass specimen with the hole (diameter 1mm) and the pin in its center was cut from the printed board (see Fig. 3b, 3c). The specimen was then placed in a micro-tensile device (Kammrath & Weiss 3 ) and loaded in axial direction. Stress-strain curves were recorded with the average values determined from the cut-out section of the printed circuit. The relative movement of the pin tips to the plating of the hole (see Fig. 4a) were obtained by digital image analysis using virtual extensometers as shown in Fig. 4b. The database was acquired using a long-range stereo microscope Leica M165 FC, a LaVision controller and DaVis software 4 .

a) pin

b) specimen dimensions

c) specimen with inserted pin

Fig. 3: Specimen geometry

350

-0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035

300

250

stress

200

150

pin opening

dL pin [mm]

100 stress [MPa]

50

0

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

strain [%]

a) Typical result; dL pin corresponds to pin tip opening

b) definition of virtual extensometers

Fig. 4 Stress-strain curve and pin tip opening

The distinct changes in the slope of the virtual extensometers can be attributed to the opening/closing of the pin tips. First, the contact stresses are released and the pin tip closes. Then, the pin is forced to open up, as its flanks are

1 https://www.soehnergroup.com/ 2 https://www.goettle.de 3 https://www.kammrath-weiss.com 4 https://www.lavision.de