Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model

Free-Cutting Steels (FCS), also referred to as Free Machining Steels, are characterised by their excellent chip formation and low cutting force during machining. However, the microstructure features which provide the advantageous machining properties have been linked to poor formability during secondary processing such as those occurring during hot rolling of bar products (Y. Liu et al., On micro-damage in hot metal working Part 1: Experimental investigation, Eng. Trans.54 (2006) 271–287). In this paper physically-based modelling equations are formulated from microstructure and flow stress observations, specifically for the high temperature deformation of FCS. The isotropic, viscoplastic-damage and stress state dependent material model is determined for a typical low-carbon FCS. The model is integrated with the commercial FE code ABAQUS Explicit through user routine VUMAT. Results are validated with the recently introduced conical splay test.

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Continuum Damage Model for Ductile Materials Based on Stress-State-Dependent Damage Functions

Encyclopedia of Continuum Mechanics ◽

10.1007/978-3-662-53605-6_253-1 ◽

2019 ◽

pp. 1-9

Author(s):

Michael Brünig

Keyword(s):

Stress State ◽

Damage Model ◽

Continuum Damage ◽

Damage Functions ◽

Continuum Damage Model ◽

Ductile Materials ◽

State Dependent

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Modeling of Stress-State-Dependent Damage and Failure of Ductile Metals

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.784.35 ◽

2015 ◽

Vol 784 ◽

pp. 35-42 ◽

Cited By ~ 6

Author(s):

Michael Brünig ◽

Daniel Brenner ◽

Steffen Gerke

Keyword(s):

Stress State ◽

Evolution Equations ◽

Damage Model ◽

Continuum Damage ◽

Ductile Metals ◽

Damage And Failure ◽

State Dependent ◽

Wide Range ◽

Stress States ◽

Failure Conditions

The paper discusses an anisotropic continuum damage model. It takes into account the effect of stress state on damage and failure conditions as well as on evolution equations of damage strains. To validate the proposed framework experiments with biaxially loaded specimens and corresponding numerical simulations are performed covering a wide range of stress states. In addition, scanning electron microscope images of the fracture surfaces show different fracture modes corresponding to stress states revealed by numerical analyses.

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Contrasting the Role of Pores on the Stress State Dependent Fracture Behavior of Additively Manufactured Low and High Ductility Metals

Materials ◽

10.3390/ma14133657 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3657

Author(s):

Alexander E. Wilson-Heid ◽

Erik T. Furton ◽

Allison M. Beese

Keyword(s):

Stainless Steel ◽

Stress State ◽

Pore Size ◽

Fracture Behavior ◽

316L Stainless Steel ◽

Equivalent Stress ◽

Failure Behavior ◽

High Ductility ◽

State Dependent ◽

Fracture Models

This study investigates the disparate impact of internal pores on the fracture behavior of two metal alloys fabricated via laser powder bed fusion (L-PBF) additive manufacturing (AM)—316L stainless steel and Ti-6Al-4V. Data from mechanical tests over a range of stress states for dense samples and those with intentionally introduced penny-shaped pores of various diameters were used to contrast the combined impact of pore size and stress state on the fracture behavior of these two materials. The fracture data were used to calibrate and compare multiple fracture models (Mohr-Coulomb, Hosford-Coulomb, and maximum stress criteria), with results compared in equivalent stress (versus stress triaxiality and Lode angle) space, as well as in their conversions to equivalent strain space. For L-PBF 316L, the strain-based fracture models captured the stress state dependent failure behavior up to the largest pore size studied (2400 µm diameter, 16% cross-sectional area of gauge region), while for L-PBF Ti-6Al-4V, the stress-based fracture models better captured the change in failure behavior with pore size up to the largest pore size studied. This difference can be attributed to the relatively high ductility of 316L stainless steel, for which all samples underwent significant plastic deformation prior to failure, contrasted with the relatively low ductility of Ti-6Al-4V, for which, with increasing pore size, the displacement to failure was dominated by elastic deformation.

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