PSI - Issue 42

K. Koch et al. / Procedia Structural Integrity 42 (2022) 506–512 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

508

3

Table 1. Mechanical and physical properties of the investigated materials.

Material

Tensile strength [MPa]

Yield strength [MPa]

Strain at fracture [%]

Young’s modulus [GPa]

42CrMo4

1430

1290

10 22

207 169

EN-GJS-400-18

365

236

Charpy specimens (10 x 10 x 55 mm) were used for the dynamic fracture toughness tests. The stiffness or compliance of the specimens was intentionally varied using different notch and pre-crack lengths. In addition to unnotched Charpy specimens and specimens with a V-notch, specimens with a V-notch and a fatigue pre-crack were used. Tab. 2 provides an overview of the used specimen geometries.

0

/

Table 2. Overview of the used specimen geometries.

Geometry

Notch length [mm]

Pre-crack length [mm]

1 2 3

-

- -

2 2

0.2 0.5

3

The dynamic fracture toughness tests were carried out under three-point bending with an instrumented PSd 300 pendulum impact test machine (WPM Leipzig, Germany). Energy losses due to the specimen and the machine components were first identified in elastic tests at low impact energies. Dynamic fracture toughness tests with pre cracked specimens ( 0 / = 0.5) were then carried out to investigate the effect of energy losses on the calculation of the critical value of the integral under dynamic loading, cd . The impact velocity 0 was varied in the range from 0.22 to 0.84 m/s, which correspond to impact energies 0 in the range from 0.5 to 7.0 J. The test setup is shown in Fig. 1a. The force was measured during tests using strain gauges which are applied on the tup. A single-point laser (type Polytec OFV-525) was used for deflection measurements. This enables the measurement of the tup displacement (after angle correction) using the Doppler effect. The specimen deflection which is required for the force-displacement curve corresponds to the tup displacement. The displacement of the support in the direction of the force was also measured using a single-point laser. Additionally, an in-plane laser (type Polytec LSV-065) was used to record the specimen vibrations, see Fig. 1b. This was done in order to identify causes for energy losses in dynamic fracture tests.

Fig. 1. Test setup, (a) front view; (b) top view. Based on the results of these investigations, the effect of energy losses on the calculation of the integral was investigated. For this purpose, was calculated according to ASTM E 1820, see Eq. (1).