PSI - Issue 13

Robert Kruzel et al. / Procedia Structural Integrity 13 (2018) 1626–1631 Kruzel and Ulewicz / Structural Integrity Procedia 00 (2018) 000 – 000

1628

3

Table 2. Chemical composition of steel used for cords D - G .

Content of the chemical element, %

Material type (cord)

C

Mn

Si

K

S

Cr

Ni

Cu

Al

Mo

N

C86D2 (cord D ) C82D2 (cord E ) C80K (cord F ) C72DP (cord G )

0.87 0.81 0.79 0.73

0.66 0.62 0.67 0.59

0.21 0.18 0.22 0.28

0.006 0.007 0.006 0.005

0.015 0.021 0.019 0.016

0.052 0.064 0.056 0.071

0.043 0.039 0.056 0.049

0.041 0.054 0.087 0.077

0.004 0.006 0.009 0.005

0.007 0.009 0.006 0.008

0.015 0.016 0.018 0.026

Fig. 1. The fatigue testing machine of the authors' design.

(a)

(b) Fig. 2. Schematic diagram of the machine for cord fatigue testing: (a) unidirectional bending conditions; (b) bidirectional bending conditions. An analysis of the microstructure of wires used for cords, made in compliance with the recommendations of standard PN-EN 10323:2005, was also made within the study using an Axiovert 25 optical microscope. The microstructures were observed on Nital-etched micro-sections. The microscopic examination did not show any significant differences in the structure of wire specimens tested. Figure 3 shows a sample microstructure image obtained for wire of steel D76. The microstructure depicted in the photograph, composed mainly of pearlite, shows cold work effects after performed plastic working. The material was not subjected to recrystallizing annealing, as evidenced by the oblong, heavily deformed structure. All of the wires tested were made of unalloyed pearlitic steel and the employed cold drawing process yielded a large degree of their plastic deformation. A similar deformation degree (in the range of 80 – 90%) has been observed for wires of eutectoid steel, Grygier and Rutkowska-Gorczyca (2016).