PSI - Issue 42

Jan Klusák et al. / Procedia Structural Integrity 42 (2022) 1369–1375 Jan Klusák et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1370

2

Nomenclature A

Coefficient of Basquin’s law Coefficient of Basquin’s law

B

Dynamic modulus of elasticity [GPa]

E d R S f u a

Stress ratio

Stress factor [MPa/  m] Amplitude of vibrations [  m]

Density [kg/m 3 ]

  a

Amplitude of loading stress [MPa]

Fatigue limit [MPa]

σ f

1. Introduction The austenitic stainless steels are widely used in many branches of industry. Nowadays they are more frequently used for constructions and load bearing elements, see e.g. Gardner (2005), Baddoo (2008). A new trend in civil engineering can be observed in the use of stainless steels for bridge structures (Lo et al., 2009). They are used for their corrosion resistance and good mechanical properties. As these structures are loaded cyclically for decades, knowledge of long-term fatigue mechanical properties is essential. The study follows our previous investigation of fatigue crack growth in AISI 304L steel ( Jambor et al. 2021, Šmíd et al. 2021, Trávníček et al. 2021, Seitl et al. 2022) and a study of construction steels S355 (Seitl et al. 2018, Seitl et al. 2018a). In this paper, we have focused on fatigue properties of 1.4306 and 1.4207 steels in very high cycle fatigue region under tension-compression mode (stress ratio R = -1). Experiments to obtain fatigue data were performed at ultrasonic fatigue loading device. The fatigue data and occurrences of crack nucleation were analyzed with using traditional fatigue theories (Klesnil & Lukáš , 1992 or Suresh 1998). 2. Material 1.4306 and 1.4307 austenitic stainless steels were chosen for testing and their comparison. Test specimens were machined from rolled sheets. The 1.4306 steel is more highly alloyed and more corrosion resistant than 1.4307. Typical chemical composition is stated in Tab. 1. The main difference is in the nickel content, which is 2 percent higher in 1.4306 steel than in 1.4307 steel. The basic mechanical properties obtained from tensile tests are shown in Tab. 2.

Table 1. Chemical composition [wt %] of examined materials

Material

C

Mn

Si

P

S

Cr

Ni

Cu

N

1.4306 1.4307

< 0.03 < 0.03

< 2.0 < 2.0

< 1.0 < 1.0

<0.045 <0.045

< 0.015 < 0.035

18.0-20.0 17.5-19.5

10.0-12.0 -

< 0.1

8.0-10.0

<1.0

< 0.11

Table 2. Basic mechanical properties of both 1.4306 and 1.4307 austenitic steels Material 0.2% Offset Yield Strength [MPa] Ultimate Tensile Strength [MPa]

Elongation at Fracture [%]

1.4306 1.4307

242.2 ±2.96 266.89±4.36

579.90±1.99 646.32±1.98

56.32±1.01 62.07±0.39