PSI - Issue 17

Thomas Simson et al. / Procedia Structural Integrity 17 (2019) 843–849

848

Author name / Structural Integrity Procedia 00 (2019) 000 – 000

6

Table 3. Average values of mechanical properties. Sample Rp 0.2 (MPa )

ε tot (%)

Rm (MPa)

HV10

Energy difference (J) 20 °C -20 °C

-50 °C 74 +/- 6 14 +/- 1 72 +/- 4 13 +/- 1

Horizontal

805 +/- 5.9

1081 +/- 8.4 1982 +/- 27.4 1096 +/- 6.5 1964 +/- 24.9 1056 +/- 7.0 2102 +/- 43.8

15.5 +/- 0.9 4.5 +/- 0.4 16.0 +/- 0.2 3.6 +/- 1.0 11.3 +/- 0.4 2.0 +/- 1.1

337 +/- 8 640 +/- 11 341 +/- 9 648 +/- 13 333 +/- 10 656 +/- 12

98 +/- 21 13 +/- 1

81 +/- 20 13 +/- 1

Horizontal + HT 1977 +/- 28.4

Vertical

839 +/- 22.9 1954 +/- 25.5 916 +/- 20.4 1963 +/- 44.4

102 +/- 11 83 +/- 5

Vertical + HT

14 +/- 1

12 +/- 1

Wrought

103 +/- 10

Wrought + HT

12 +/- 1

3.3. Component test

For the test of ball joints for attaching headlamps a test setup was realized (Fig. 5a)). To connect them, a prototype frame made by LPBF was used. For testing automotive headlamps, frequency ranges of excitation from low (5-10 Hz) to high (200-1000 Hz) are typically used for multi-hour tests. The typical acceleration is about 1 to 3 g (RMS) at resonant frequencies in the range of 30 to 50 Hz. The tests are carried out in the low frequency range of 5-50 Hz, in which the resonance frequency of the headlamp is to be expected. Fig. 5a) shows the experimental setup. In the experimental setup, 6 points for measurement and one point on the excitation plate are defined as reference. Points 1-3 are on the metal frame produced by LPBF , and points 4-6 refer to the aluminum weights. The experiment was repeated several times, tightening of plastic ball joints and other joints for better results. The measurement itself was first performed for discrete frequencies (5, 10, 15-50 Hz) and later with continuous increment of frequency from 5-50 Hz. For each test, 6 points were measured on the frame and aluminum weights and one point on the excitation source (to calculate the relative amplitude). The measured signal has the lowest noise on the clean reflective aluminum surface of the excitation plate. Higher noise is measured on the AM frame, possibly due to the surface roughness. The measured time-dependent velocity signal from excitation plate is shown Fig. 5b) (top) and from point 2 of the frame with noise (bottom). The noise was then removed by the digital filtering before analysis. The measured signals were filtered and then the accelerations calculated by numeric method. The calculated accelerations of the frame points 1, 2, 3 are shown in Fig. 5c) (green, blue, magenta). It is obvious that we achieve resonant frequency. The time in second is plotted on the x-axis of the signal (measurement with continuous frequency increase). The x-axis was then converted to the corresponding frequency, the acceleration amplitude was divided by amplitude of point 0 (excitation frequency) and resulting relative amplitude is shown in Fig. 5d). Through data analysis, a range of 30-35 Hz for the resonant frequency could be determined. This is a typical result for car headlamps. The resonant frequency range is a parameter for tightening the ball joints. However, it has been stated that the frame produced by LPBF does not give different results than a conventionally produced frame. This shows that AM components can be used for prototype testing.

Fig. 5. Component test: (a) experimental setup, (b) raw velocity signal, (c) filtered signals, (d) relative amplitude.