Research article
The cumulative detrimental impact of pressure and autofrettage on the fatigue life of an externally cracked modern tank gun barrel

Aaron Fish Professor Emeritus of Mechanical EngineeringFracture Mechanics and graduate student respectively. Department of Mechanical Engineering, BenGurion University of the Negev, BeerSheva, 84105, Israel

Received:
11 May 2019
Accepted:
06 September 2019
Published:
17 September 2019




The fatigue life of an externally cracked modern tank gun barrel is controlled by the prevailing combined stress intensity factor (SIF) K_{IN}, which consists of two components:K_{IP}the SIF caused by internal pressure; K_{IA}the positive SIF due to the tensile residual stresses induced by autofrettage. K_{IA} values for a single external radial semielliptical crack originating at the outer surface of an autofrettaged gun barrel were calculated for a large number of crack configurations by Perl and Saley. In order to assess the combined effect of overstraining and the pressurizing of the barrel during firing, values of K_{IP}, the SIF caused by internal pressure, and those of K_{IN}, the combined SIF, are evaluated. The 3D analysis is performed using the finite element method (FEM) employing singular elements along the crack front. The novel realistic overstrain residual stress fields, incorporating the Bauschinger effect, for the three types of autofrettage, Swage, Hydraulic and Hill's, previously developed, are applied to the barrel. The RSFs are simulated in the finit element (FE) analysis using equivalent temperature fields. Values of K_{IP} and K_{IN} are evaluated for a typical barrel of radii ratio R_{0}/R_{i}=2, crack depths (a/t=0.0050.1), crack ellipticities (a/c=0.21.0), and five levels of the three types of autofrettage, (ε=40%, 60%, 70%, 80%, and 100%). A detailed analysis of the effect of the above parameters on the prevailing SIF is conducted. All three types of autofrettage are found to have a detrimental effect on the barrel's fatigue life. However, the magnitude of life reduction is autofrettagetype dependent. In the case of external cracking, Hydraulic autofrettage is found to be somewhat superior to Swage autofrettage, and Hill's autofrettage is found to be nonrealistic. Finally, the results accentuate the importance of the three dimensional analysis and the incorporation of the Bauschinger effect.
Citation: Mordechai Perl, Tomer Saley. The cumulative detrimental impact of pressure and autofrettage on the fatigue life of an externally cracked modern tank gun barrel[J]. AIMS Materials Science, 2019, 6(5): 833851. doi: 10.3934/matersci.2019.5.833

Abstract
The fatigue life of an externally cracked modern tank gun barrel is controlled by the prevailing combined stress intensity factor (SIF) K_{IN}, which consists of two components:K_{IP}the SIF caused by internal pressure; K_{IA}the positive SIF due to the tensile residual stresses induced by autofrettage. K_{IA} values for a single external radial semielliptical crack originating at the outer surface of an autofrettaged gun barrel were calculated for a large number of crack configurations by Perl and Saley. In order to assess the combined effect of overstraining and the pressurizing of the barrel during firing, values of K_{IP}, the SIF caused by internal pressure, and those of K_{IN}, the combined SIF, are evaluated. The 3D analysis is performed using the finite element method (FEM) employing singular elements along the crack front. The novel realistic overstrain residual stress fields, incorporating the Bauschinger effect, for the three types of autofrettage, Swage, Hydraulic and Hill's, previously developed, are applied to the barrel. The RSFs are simulated in the finit element (FE) analysis using equivalent temperature fields. Values of K_{IP} and K_{IN} are evaluated for a typical barrel of radii ratio R_{0}/R_{i}=2, crack depths (a/t=0.0050.1), crack ellipticities (a/c=0.21.0), and five levels of the three types of autofrettage, (ε=40%, 60%, 70%, 80%, and 100%). A detailed analysis of the effect of the above parameters on the prevailing SIF is conducted. All three types of autofrettage are found to have a detrimental effect on the barrel's fatigue life. However, the magnitude of life reduction is autofrettagetype dependent. In the case of external cracking, Hydraulic autofrettage is found to be somewhat superior to Swage autofrettage, and Hill's autofrettage is found to be nonrealistic. Finally, the results accentuate the importance of the three dimensional analysis and the incorporation of the Bauschinger effect.
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