PSI - Issue 48

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Fašun et al/ Structural Integrity Procedia 00 (2023) 000–000

Gašper Fašun et al. / Procedia Structural Integrity 48 (2023) 19–26

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E-mail address: nenad.gubeljak@uni-mb.si

The main input parameter in the lifetime analysis is certainly the pressure created by the combustion of the explosive acting on the inner wall of the cannon barrel. In this paper, the maximum values of pressure most commonly found in the literature for cannon barrels of similar geometries are used. In the analysis of the lifetime of the classic cannon barrel we can find the pressure value of 380 MPa [1,2]. Experimental measurements in closed container for testing howitzer barrel pressure showed maximum pressure of 420 MPa for barrel with inner radius of 155 mm [3]. In the analysis of the exit pressure of a howitzer muzzle with the same diameter, a maximum value of 377 MPa has been measured [4]. In the analysis of simulation of artillery chambers [5], a pressure of 322 MPa for barrels with a diameter of 130 mm is mentioned. Besides, for a howitzer of the same dimensions a pressure of 309 MPa was found [6]. The distribution of pressure in barrel, p(x), whose value depends on position, can be summarized according to [7]. Based on the pressure distribution p(x), the location of the samples where the maximum pressure pmax is experimented can be determined for further analyses. Fig. 1 shows the cannon barrel geometry, the pressure distribution along the barrel and a cross section with schemas of all the specimens used for the experimental characterization of the material, and their localization and orientations. This paper analyses the fatigue lifetime of a howitzer cannon barrel using a fracture mechanics approach. The study considers a maximum pressure range of 300-420 MPa for two different heat treatments of a 35NiCrMoV12-5 alloy. Fig. 1 shows the geometry and cross-section of the analysed barrel, with an external diameter of 2R0 = 341 mm and an internal diameter of 2Ri = 155 mm.

Nomenclature 2R o

External diameter Interna diameter Wall thickness

2 R i

t

Grain size Crack length

d a c

Half of a crack’s width

Crack length that produces failure of component – Critical crack length

a crit

Initial crack length – defect size Inclusion size (Material A, B)

a i

d iA,B   ,  R     ܥ  ,  ∆ K ∆ K th ∆ K thR ∆ K dR  T   eR

Change of temperate when loading samples during thermographic method

Ultimate tensile strength (Material A, B)

Loading ratio Hoop stress

Applied stress amplitude

Fatigue limit

Fracture toughness (Material A, B) Applied stress intensity factor range Fatigue crack propagation threshold

Fatigue crack propagation threshold for long cracks in respect to loading ratio

Microstructural threshold

Geometric configuration correction factor Fatigue material constants in Paris range

Y

C and m

Material constant

k p

Pressure

Maximum pressure value of applied pressure function p(x)

p max