Title

A Continuum Damage Model for the Strain Rate Corrosion Testing of Austenitic Stainless Steels

A Continuum Damage Model for the Strain Rate Corrosion Testing of Austenitic Stainless Steels

Authorship

MATTOS, HERALDO SILVA DA COSTA; BASTOS, IVAN NAPOLEÃO; GOMES, JOSÉ ANTONIO DA CUNHA PONCIANO

MATTOS, HERALDO SILVA DA COSTA

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BASTOS, IVAN NAPOLEÃO

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GOMES, JOSÉ ANTONIO DA CUNHA PONCIANO

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DOI

10.5151/2594-5327-2818

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Abstract

Slow strain rate testing is widely used on stress corrosion cracking research as the basic experimental technique to promote the incidence of cracking and to determine the ranking of susceptibility of different alloys in several corrosive environments. With this methodology, however, the assessment of "threshold values" to be used as design parameters is not a simple task in the present state of art of the corrosion area. This limitation induces the use of the SSR testing as "go-no go" test for materials selection and some basic information required, for instance, time to failure in service, can not be inferred by this approach. The most important reason for the limitation described is the complexity of stress corrosion mechanism that involves the conjoint action of mechanical and electrochemical processes. On the present work, a methodology for modeling SSR testing based upon thermodynamics of continuum solids and elasto-plastic damage is proposed. In this macroscopic approach, besides the classical variables (stress, total strain, plastic strain), an additional scalar variable related with the damage induced by stress corrosion is introduced. An evolution law with environment dependent parameters is proposed for this damage variable. The model accounts for the stress corrosion effect through a reduction of the mechanical resistance of the material induced by the damage variable. The model prediction is compared with the curves obtained experimentally in different acid solutions at room temperature showing a good agreement. The alloy/environments system is 304 austenitic stainless steel/acid chloride solutions.

Slow strain rate testing is widely used on stress corrosion cracking research as the basic experimental technique to promote the incidence of cracking and to determine the ranking of susceptibility of different alloys in several corrosive environments. With this methodology, however, the assessment of "threshold values" to be used as design parameters is not a simple task in the present state of art of the corrosion area. This limitation induces the use of the SSR testing as "go-no go" test for materials selection and some basic information required, for instance, time to failure in service, can not be inferred by this approach. The most important reason for the limitation described is the complexity of stress corrosion mechanism that involves the conjoint action of mechanical and electrochemical processes. On the present work, a methodology for modeling SSR testing based upon thermodynamics of continuum solids and elasto-plastic damage is proposed. In this macroscopic approach, besides the classical variables (stress, total strain, plastic strain), an additional scalar variable related with the damage induced by stress corrosion is introduced. An evolution law with environment dependent parameters is proposed for this damage variable. The model accounts for the stress corrosion effect through a reduction of the mechanical resistance of the material induced by the damage variable. The model prediction is compared with the curves obtained experimentally in different acid solutions at room temperature showing a good agreement. The alloy/environments system is 304 austenitic stainless steel/acid chloride solutions.

Keywords

Slow Strain Rate, Damage Mechanics, Stress Corrosion Cracking, Stainless Steel

Slow Strain Rate, Damage Mechanics, Stress Corrosion Cracking, Stainless Steel