PSI - Issue 54

Ela Marković et al. / Procedia Structural Integrity 54 (2024) 156 – 163

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6

Ela Markovi ć et al. / Structural Integrity Procedia 00 (2023) 000–000

2200

1400

600 Stress, MPa

0

0,1

0,2

0,3

Plastic strain, mm/mm

Fig. 6. Multilinear stress – plastic strain curves for different values of hardness.

3. Results of finite element analyses 3.1. Mechanical behavior of unnotched specimen

In order to initially evaluate the distribution of stresses and strains in the FGM specimen, a simulation was conducted on a rectangular specimen without a notch. A displacement of Δ y = 4 mm was applied to the nodes on the top line of the 1/4 th specimen, which corresponds to a displacement of Δ y = 8 mm for the entire specimen. Homogeneous specimen is modeled as not being surface hardened with hardness of 300 HV (lowest curve in Figure 6) throughout the entire specimen, and FGM as surface hardened, utilizing the pseudo-temperature method and multilinear curves from Figure 6 (Young's modulus 200 GPa, Poisson's ratio 0,3). Figure 7 displays the nodal results of the von Mises stress distribution for the homogeneous and FGM specimen without the notch. The data, additionally including also plastic strain, was interpolated and mapped to 40 equally spaced points in x direction with y -coordinate of 50 mm which resulted in a diagram shown in the Figure 7. It can be seen that the stress and plastic strain results follow the initially conditioned hardness distribution.

2000 3000

0,044 0,046 0,048 0,050 0,052

1000

MPa

Plastic strain, mm/mm

0

0 von Mises stress,

5

10

Distance from surface x , mm

Fig. 7. Von Mises stress field of a specimen with homogeneous material (left) and FGM specimen defined with 20 multilinear piece-wise curves (right) with graph of stress and plastic strain distribution along a horizontal path. Quarter of a specimen is shown.

3.2. Mechanical behavior of notched specimen Two cases of functionally graded material specimens are presented in Figure 8, one being modeled as surface hardened prior to the creation of notch (FGM 1), while the other modeled as surface hardened after the creation of notch (FGM 2). Consequently, latter case results in a hardened notch.

Fig. 8. Two cases of functionally graded notched material specimen. Surface hardening applied prior to notch creation marked FGM 1 (left) and after the notch creation marked FGM 2 (right).