MARCOS LUGO | University of Texas of the Permian Basin (original) (raw)

Papers by MARCOS LUGO

Research paper thumbnail of Integrating Temperature Dependence into a Microstructure-Sensitive Fatigue Model for Titanium Alloys

Research paper thumbnail of Cultural Flourishing: Technology & Infrastructure Resiliency

Research paper thumbnail of Anti-Roll Bar Fatigue Analysis and Redesign

Research paper thumbnail of Diversifying Nuclear Technology: A Technical Analysis on Small Modular Reactors and Its Impact on Nuclear Energy Policy

is currently pursuing her master's degree in public policy at Liberty University. Previously, she... more is currently pursuing her master's degree in public policy at Liberty University. Previously, she obtained her bachelor's degree in mechanical engineering with a nuclear track. Her interest in is in contributing to the contemporary energy and environmental challenges of our time with some emphasis on nuclear energy based on her background. She expects to compile her knowledge of both technical and policy aspects of nuclear energy to provide viable solutions that promote the benefits of the energy source.

Research paper thumbnail of Cyclic behavior and modeling of small fatigue cracks of a polycarbonate polymer

International Journal of Fatigue

The fatigue behavior of a polycarbonate (PC) thermoplastic material was experimentally investigat... more The fatigue behavior of a polycarbonate (PC) thermoplastic material was experimentally investigated and modeled using a MultiStage Fatigue (MSF) model that evaluates fatigue crack incubation, Microstructurally Small Crack (MSC) growth, and Long Crack (LC) growth. A set of fully reversed strain controlled tests were conducted, and an analysis of the fracture surfaces was performed using Scanning Electron Microscopy (SEM) in order to quantify the structure-property relationships for the MSF model. Fractography of the microstructure revealed that incompletely melted PC pellets were present in the polymer material that nucleated the cracks along with crazes generated on the surface. Crack lengths and fatigue crack growth rates for the MSC regime were measured from striation observations on the fracture surfaces. Discontinuous crack growth (DCG) cycles between fatigue striations, for the current iteration of the model, are accounted for by the MSF crack incubation regime. Finally, the microstructure sensitive MSF model was implemented using the observed fatigue crack growth measurements. In addition, a Monte Carlo (MC) Simple Random Sampling (SRS) routine was implemented to quantify the model uncertainty for crack growth.

Research paper thumbnail of Finite element modeling of plasticity induced crack closure and a mechanics based study of crack closure measurement techniques

Research paper thumbnail of Microstructure‐based fatigue modeling of an acrylonitrile butadiene styrene (ABS) copolymer

ABSTRACT In this article, we experimentally investigate the structure–property relationships of a... more ABSTRACT In this article, we experimentally investigate the structure–property relationships of an acrylonitrile butadiene styrene (ABS) copolymer for fatigue and use a microstructure-based multistage fatigue (MSF) model to predict material failure. The MSF model comprises three stages of fatigue damage (crack incubation, small crack growth, and long crack growth) that was originally used for metal alloys. This study shows for the first time that the MSF theory is general enough to apply to polymer systems like ABS. The experimental study included monotonic testing (compression and tension) and fully reversed uniaxial cyclic tests at two frequencies (1 Hz and 10 Hz) with a range of strain amplitudes of 0.006 to 0.04. Cyclical softening was observed in the ABS copolymer. Fractography studies of failed specimens revealed that particles were responsible for crack incubation. Although polymeric materials can be argued to be more complex in terms of failure modes and thermo-mechano-chemical sensitivity when compared with most metal alloys, results showed that the MSF model could be extended successfully to capture microstructural effects to polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40882.

Research paper thumbnail of Effects of Microstructural Inclusions on Fatigue Life of Polyether Ether Ketone (PEEK)

Journal of the Mechanical Behavior of Biomedical Materials, 2015

Fatigue life estimation Structure-property relations Strain-life approach Fatigue modeling Polyet... more Fatigue life estimation Structure-property relations Strain-life approach Fatigue modeling Polyether ether ketone (PEEK) a b s t r a c t In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semicrystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strainlife results and the observed microstructure of fatigue specimens, a microstructuresensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK. (J. Simsiriwong).

Research paper thumbnail of Fatigue Behavior and Modeling for Thermoplastics

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Fatigue mechanism and multistage fatigue modeling for wrought Mg-3Al-1Zn

The cyclic and fatigue behavior of an extruded AZ31 Mg alloy were evaluated and the microstructur... more The cyclic and fatigue behavior of an extruded AZ31 Mg alloy were evaluated and the microstructure-fatigue properties relation was developed based on multiscale fatigue experiments. The unusual nonlinear initial compressive unloading and cyclic hardening behaviors were observed. The large intermetallic particles in coarse grains at or near the surface are identified as the fatigue damage incubation sites. The morphology of the inclusion particles as well as bonding strength between the particle and alloy matrix, affects fatigue incubation life as observed in micromechanical simulations in conjunction with the modified microscale Coffin-Manson law. Crack growth rate was directly quantified as a function of applied stress amplitude weighted by the applied stress ratio. The fatigue long crack growth was modeled combining a generalized Paris law with the application of a strip-yield model at the crack tip. Finally, the multistage fatigue model was implemented to evaluate the fatigue life of a simple component in an automobile Mg-front end application.

Research paper thumbnail of Investigation of Cyclic Behavior and Structure-property Relations of a 304 Stainless Steel

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Fatigue Behavior of Ti-6Al-4V Alloy Additively Manufactured by Laser Engineered Net Shaping

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Microstructure and damage evolution during tensile loading in a wrought magnesium alloy

Scripta Materialia, 2011

Damage evolution in a wrought magnesium alloy under uniaxial tensile deformation is investigated.... more Damage evolution in a wrought magnesium alloy under uniaxial tensile deformation is investigated. Sectioned specimens subjected to interrupted tensile deformation were examined under optical microscopy to quantify the number density of cracked intermetallic particles as a function of applied strain. Digital image analysis of the optical images was employed to quantify damage by separating cracked from non-cracked particles. Finally, an internal state variable damage model was shown to adequately capture the experimentally observed damage progression due to the intermetallics.

Research paper thumbnail of Observations and modeling of the small fatigue crack behavior of an extruded AZ61 magnesium alloy

International Journal of Fatigue, 2013

ABSTRACT The objective of this paper is to quantify the microstructurally small fatigue crack gro... more ABSTRACT The objective of this paper is to quantify the microstructurally small fatigue crack growth of an extruded AZ61 magnesium alloy. Fully reversed and interrupted load-controlled tests were conducted on notched specimens that were taken from the material in the longitudinal and transverse orientations with respect to the extrusion direction. In order to measure crack growth, replicas of the notch surface were made using a dual-step silicon-rubber compound at periodic cyclic intervals. By using microscopic analysis of the replica surfaces, crack initiation sites from numerous locations and crack growth rates were determined. A marked acceleration/deceleration was observed to occur in cracks of smaller length scales due to local microheterogeneities consistent with prior observations of small fatigue crack interaction with the native microstructure and texture. Finally, a microstructure-sensitive multistage fatigue model was employed to estimate the observed crack growth behavior and fatigue life with respect to the microstructure with the most notable item being the grain orientation. The crack growth rate and fatigue life estimates are shown to compare well to published findings for pure magnesium single crystal atomistic simulations.

Research paper thumbnail of Role of different material processing methods on the fatigue behavior of an AZ31 magnesium alloy

International Journal of Fatigue, 2013

The influence of extrusion, plate rolling, and sheet rolling on the fa tigue life of an AZ31 magn... more The influence of extrusion, plate rolling, and sheet rolling on the fa tigue life of an AZ31 magnesium alloy is investigated with a microstructure-sensitive fatigue model that comprises both crack incubation and growth stages. The model describes the effect of primary processing on the microstructure by incorporating specific mechanical properties and microstructural attributes such as grain and inclusion sizes. As such, the fatigue model successfully captured the experimentally observed differences in fatigue lifetimes of the Mg alloy due to the induced in-plane constraint effects resulting from different material processing methods. Quantitative prediction of cumulative damage due to cyclic loading and its comparison with experimental data is described in detail.

Research paper thumbnail of A mechanics based study of crack closure measurement techniques under constant amplitude loading

International Journal of Fatigue, 2011

An elastic-plastic finite element model was used to simulate a growing fatigue crack in a middle-... more An elastic-plastic finite element model was used to simulate a growing fatigue crack in a middle-crack tension specimen made of an aluminum alloy. The finite element analysis provided the load-displacement curve at various locations as is commonly done in experimental work, and the crack opening stress intensity factor (K op ) was determined with ASTM standard methods, Elber's method, and the Adjusted Compliance Ratio (ACR) method. The performance of ACR was compared against the established standard methods. Measurement location effects on K op and ACR were investigated. ASTM (2% offset) and ACR methods gave values that were dependent upon measurement location. Whereas, Elber's method (0% offset) gave values that were independent of measurement location.

Research paper thumbnail of The influence of T-stress on plasticity induced crack closure under plane strain conditions

International Journal of Fatigue, 2011

... The Influence of T-stress on Plasticity Induced Crack Closure Under Plane Strain Conditions M... more ... The Influence of T-stress on Plasticity Induced Crack Closure Under Plane Strain Conditions M. Lugo and SR Daniewicz Department of Mechanical Engineering Mississippi State ... For the stress level max/ 0=0.4 a normalized opening value of K0/Kmax=0.20 was reported. ...

Research paper thumbnail of Microstructural Relationship in the Damage Evolution Process of an Az61 Magnesium Alloy

ABSTRACT The damage evolution process of magnesium AZ61 alloy under monotonic tensile loading con... more ABSTRACT The damage evolution process of magnesium AZ61 alloy under monotonic tensile loading conditions is investigated. Specimens that have been subjected to interrupted tensile loading were examined under optical microscopy to quantify the number density of cracked intermetallic particles as a function of applied strain. Digital image analysis of the optical images was employed to automatically quantify damage by separating cracked from non-cracked particles. Lastly, an internal state variable damage model was shown to adequately capture the experimentally-observed damage of intermetallic particles in the magnesium AZ61 alloy.

Research paper thumbnail of Microstructure-based fatigue modeling of an acrylonitrile butadiene styrene (ABS) copolymer

Journal of Applied Polymer Science, 2014

ABSTRACT In this article, we experimentally investigate the structure–property relationships of a... more ABSTRACT In this article, we experimentally investigate the structure–property relationships of an acrylonitrile butadiene styrene (ABS) copolymer for fatigue and use a microstructure-based multistage fatigue (MSF) model to predict material failure. The MSF model comprises three stages of fatigue damage (crack incubation, small crack growth, and long crack growth) that was originally used for metal alloys. This study shows for the first time that the MSF theory is general enough to apply to polymer systems like ABS. The experimental study included monotonic testing (compression and tension) and fully reversed uniaxial cyclic tests at two frequencies (1 Hz and 10 Hz) with a range of strain amplitudes of 0.006 to 0.04. Cyclical softening was observed in the ABS copolymer. Fractography studies of failed specimens revealed that particles were responsible for crack incubation. Although polymeric materials can be argued to be more complex in terms of failure modes and thermo-mechano-chemical sensitivity when compared with most metal alloys, results showed that the MSF model could be extended successfully to capture microstructural effects to polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40882.

Research paper thumbnail of Quantification of damage evolution in a 7075 aluminum alloy using an acoustic emission technique

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011

The use of acoustic emission for quantifying the microstructural damage evolution under tensile l... more The use of acoustic emission for quantifying the microstructural damage evolution under tensile loading is studied for a 7075 aluminum alloy. First, the cracking of intermetallic particles present in the material was evaluated using interrupted tensile tests combined with digital image analysis of large optical image montages. Subsequent acoustic emission tests under tensile monotonic loading produced an in situ signature that correlated with the quantitative stereology results obtained destructively. Acoustic emission is a viable option for quantifying the evolution of microstructure damage in terms of particle cracking for the 7075 alloy.

Research paper thumbnail of Integrating Temperature Dependence into a Microstructure-Sensitive Fatigue Model for Titanium Alloys

Research paper thumbnail of Cultural Flourishing: Technology & Infrastructure Resiliency

Research paper thumbnail of Anti-Roll Bar Fatigue Analysis and Redesign

Research paper thumbnail of Diversifying Nuclear Technology: A Technical Analysis on Small Modular Reactors and Its Impact on Nuclear Energy Policy

is currently pursuing her master's degree in public policy at Liberty University. Previously, she... more is currently pursuing her master's degree in public policy at Liberty University. Previously, she obtained her bachelor's degree in mechanical engineering with a nuclear track. Her interest in is in contributing to the contemporary energy and environmental challenges of our time with some emphasis on nuclear energy based on her background. She expects to compile her knowledge of both technical and policy aspects of nuclear energy to provide viable solutions that promote the benefits of the energy source.

Research paper thumbnail of Cyclic behavior and modeling of small fatigue cracks of a polycarbonate polymer

International Journal of Fatigue

The fatigue behavior of a polycarbonate (PC) thermoplastic material was experimentally investigat... more The fatigue behavior of a polycarbonate (PC) thermoplastic material was experimentally investigated and modeled using a MultiStage Fatigue (MSF) model that evaluates fatigue crack incubation, Microstructurally Small Crack (MSC) growth, and Long Crack (LC) growth. A set of fully reversed strain controlled tests were conducted, and an analysis of the fracture surfaces was performed using Scanning Electron Microscopy (SEM) in order to quantify the structure-property relationships for the MSF model. Fractography of the microstructure revealed that incompletely melted PC pellets were present in the polymer material that nucleated the cracks along with crazes generated on the surface. Crack lengths and fatigue crack growth rates for the MSC regime were measured from striation observations on the fracture surfaces. Discontinuous crack growth (DCG) cycles between fatigue striations, for the current iteration of the model, are accounted for by the MSF crack incubation regime. Finally, the microstructure sensitive MSF model was implemented using the observed fatigue crack growth measurements. In addition, a Monte Carlo (MC) Simple Random Sampling (SRS) routine was implemented to quantify the model uncertainty for crack growth.

Research paper thumbnail of Finite element modeling of plasticity induced crack closure and a mechanics based study of crack closure measurement techniques

Research paper thumbnail of Microstructure‐based fatigue modeling of an acrylonitrile butadiene styrene (ABS) copolymer

ABSTRACT In this article, we experimentally investigate the structure–property relationships of a... more ABSTRACT In this article, we experimentally investigate the structure–property relationships of an acrylonitrile butadiene styrene (ABS) copolymer for fatigue and use a microstructure-based multistage fatigue (MSF) model to predict material failure. The MSF model comprises three stages of fatigue damage (crack incubation, small crack growth, and long crack growth) that was originally used for metal alloys. This study shows for the first time that the MSF theory is general enough to apply to polymer systems like ABS. The experimental study included monotonic testing (compression and tension) and fully reversed uniaxial cyclic tests at two frequencies (1 Hz and 10 Hz) with a range of strain amplitudes of 0.006 to 0.04. Cyclical softening was observed in the ABS copolymer. Fractography studies of failed specimens revealed that particles were responsible for crack incubation. Although polymeric materials can be argued to be more complex in terms of failure modes and thermo-mechano-chemical sensitivity when compared with most metal alloys, results showed that the MSF model could be extended successfully to capture microstructural effects to polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40882.

Research paper thumbnail of Effects of Microstructural Inclusions on Fatigue Life of Polyether Ether Ketone (PEEK)

Journal of the Mechanical Behavior of Biomedical Materials, 2015

Fatigue life estimation Structure-property relations Strain-life approach Fatigue modeling Polyet... more Fatigue life estimation Structure-property relations Strain-life approach Fatigue modeling Polyether ether ketone (PEEK) a b s t r a c t In this study, the effects of microstructural inclusions on fatigue life of polyether ether ketone (PEEK) was investigated. Due to the versatility of its material properties, the semicrystralline PEEK polymer has been increasingly adopted in a wide range of applications particularly as a biomaterial for orthopedic, trauma, and spinal implants. To obtain the cyclic behavior of PEEK, uniaxial fully-reversed strain-controlled fatigue tests were conducted at ambient temperature and at 0.02 mm/mm to 0.04 mm/mm strain amplitudes. The microstructure of PEEK was obtained using the optical and the scanning electron microscope (SEM) to determine the microstructural inclusion properties in PEEK specimen such as inclusion size, type, and nearest neighbor distance. SEM analysis was also conducted on the fracture surface of fatigue specimens to observe microstructural inclusions that served as the crack incubation sites. Based on the experimental strainlife results and the observed microstructure of fatigue specimens, a microstructuresensitive fatigue model was used to predict the fatigue life of PEEK that includes both crack incubation and small crack growth regimes. Results show that the employed model is applicable to capture microstructural effects on fatigue behavior of PEEK. (J. Simsiriwong).

Research paper thumbnail of Fatigue Behavior and Modeling for Thermoplastics

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Fatigue mechanism and multistage fatigue modeling for wrought Mg-3Al-1Zn

The cyclic and fatigue behavior of an extruded AZ31 Mg alloy were evaluated and the microstructur... more The cyclic and fatigue behavior of an extruded AZ31 Mg alloy were evaluated and the microstructure-fatigue properties relation was developed based on multiscale fatigue experiments. The unusual nonlinear initial compressive unloading and cyclic hardening behaviors were observed. The large intermetallic particles in coarse grains at or near the surface are identified as the fatigue damage incubation sites. The morphology of the inclusion particles as well as bonding strength between the particle and alloy matrix, affects fatigue incubation life as observed in micromechanical simulations in conjunction with the modified microscale Coffin-Manson law. Crack growth rate was directly quantified as a function of applied stress amplitude weighted by the applied stress ratio. The fatigue long crack growth was modeled combining a generalized Paris law with the application of a strip-yield model at the crack tip. Finally, the multistage fatigue model was implemented to evaluate the fatigue life of a simple component in an automobile Mg-front end application.

Research paper thumbnail of Investigation of Cyclic Behavior and Structure-property Relations of a 304 Stainless Steel

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Fatigue Behavior of Ti-6Al-4V Alloy Additively Manufactured by Laser Engineered Net Shaping

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 2015

ABSTRACT

Research paper thumbnail of Microstructure and damage evolution during tensile loading in a wrought magnesium alloy

Scripta Materialia, 2011

Damage evolution in a wrought magnesium alloy under uniaxial tensile deformation is investigated.... more Damage evolution in a wrought magnesium alloy under uniaxial tensile deformation is investigated. Sectioned specimens subjected to interrupted tensile deformation were examined under optical microscopy to quantify the number density of cracked intermetallic particles as a function of applied strain. Digital image analysis of the optical images was employed to quantify damage by separating cracked from non-cracked particles. Finally, an internal state variable damage model was shown to adequately capture the experimentally observed damage progression due to the intermetallics.

Research paper thumbnail of Observations and modeling of the small fatigue crack behavior of an extruded AZ61 magnesium alloy

International Journal of Fatigue, 2013

ABSTRACT The objective of this paper is to quantify the microstructurally small fatigue crack gro... more ABSTRACT The objective of this paper is to quantify the microstructurally small fatigue crack growth of an extruded AZ61 magnesium alloy. Fully reversed and interrupted load-controlled tests were conducted on notched specimens that were taken from the material in the longitudinal and transverse orientations with respect to the extrusion direction. In order to measure crack growth, replicas of the notch surface were made using a dual-step silicon-rubber compound at periodic cyclic intervals. By using microscopic analysis of the replica surfaces, crack initiation sites from numerous locations and crack growth rates were determined. A marked acceleration/deceleration was observed to occur in cracks of smaller length scales due to local microheterogeneities consistent with prior observations of small fatigue crack interaction with the native microstructure and texture. Finally, a microstructure-sensitive multistage fatigue model was employed to estimate the observed crack growth behavior and fatigue life with respect to the microstructure with the most notable item being the grain orientation. The crack growth rate and fatigue life estimates are shown to compare well to published findings for pure magnesium single crystal atomistic simulations.

Research paper thumbnail of Role of different material processing methods on the fatigue behavior of an AZ31 magnesium alloy

International Journal of Fatigue, 2013

The influence of extrusion, plate rolling, and sheet rolling on the fa tigue life of an AZ31 magn... more The influence of extrusion, plate rolling, and sheet rolling on the fa tigue life of an AZ31 magnesium alloy is investigated with a microstructure-sensitive fatigue model that comprises both crack incubation and growth stages. The model describes the effect of primary processing on the microstructure by incorporating specific mechanical properties and microstructural attributes such as grain and inclusion sizes. As such, the fatigue model successfully captured the experimentally observed differences in fatigue lifetimes of the Mg alloy due to the induced in-plane constraint effects resulting from different material processing methods. Quantitative prediction of cumulative damage due to cyclic loading and its comparison with experimental data is described in detail.

Research paper thumbnail of A mechanics based study of crack closure measurement techniques under constant amplitude loading

International Journal of Fatigue, 2011

An elastic-plastic finite element model was used to simulate a growing fatigue crack in a middle-... more An elastic-plastic finite element model was used to simulate a growing fatigue crack in a middle-crack tension specimen made of an aluminum alloy. The finite element analysis provided the load-displacement curve at various locations as is commonly done in experimental work, and the crack opening stress intensity factor (K op ) was determined with ASTM standard methods, Elber's method, and the Adjusted Compliance Ratio (ACR) method. The performance of ACR was compared against the established standard methods. Measurement location effects on K op and ACR were investigated. ASTM (2% offset) and ACR methods gave values that were dependent upon measurement location. Whereas, Elber's method (0% offset) gave values that were independent of measurement location.

Research paper thumbnail of The influence of T-stress on plasticity induced crack closure under plane strain conditions

International Journal of Fatigue, 2011

... The Influence of T-stress on Plasticity Induced Crack Closure Under Plane Strain Conditions M... more ... The Influence of T-stress on Plasticity Induced Crack Closure Under Plane Strain Conditions M. Lugo and SR Daniewicz Department of Mechanical Engineering Mississippi State ... For the stress level max/ 0=0.4 a normalized opening value of K0/Kmax=0.20 was reported. ...

Research paper thumbnail of Microstructural Relationship in the Damage Evolution Process of an Az61 Magnesium Alloy

ABSTRACT The damage evolution process of magnesium AZ61 alloy under monotonic tensile loading con... more ABSTRACT The damage evolution process of magnesium AZ61 alloy under monotonic tensile loading conditions is investigated. Specimens that have been subjected to interrupted tensile loading were examined under optical microscopy to quantify the number density of cracked intermetallic particles as a function of applied strain. Digital image analysis of the optical images was employed to automatically quantify damage by separating cracked from non-cracked particles. Lastly, an internal state variable damage model was shown to adequately capture the experimentally-observed damage of intermetallic particles in the magnesium AZ61 alloy.

Research paper thumbnail of Microstructure-based fatigue modeling of an acrylonitrile butadiene styrene (ABS) copolymer

Journal of Applied Polymer Science, 2014

ABSTRACT In this article, we experimentally investigate the structure–property relationships of a... more ABSTRACT In this article, we experimentally investigate the structure–property relationships of an acrylonitrile butadiene styrene (ABS) copolymer for fatigue and use a microstructure-based multistage fatigue (MSF) model to predict material failure. The MSF model comprises three stages of fatigue damage (crack incubation, small crack growth, and long crack growth) that was originally used for metal alloys. This study shows for the first time that the MSF theory is general enough to apply to polymer systems like ABS. The experimental study included monotonic testing (compression and tension) and fully reversed uniaxial cyclic tests at two frequencies (1 Hz and 10 Hz) with a range of strain amplitudes of 0.006 to 0.04. Cyclical softening was observed in the ABS copolymer. Fractography studies of failed specimens revealed that particles were responsible for crack incubation. Although polymeric materials can be argued to be more complex in terms of failure modes and thermo-mechano-chemical sensitivity when compared with most metal alloys, results showed that the MSF model could be extended successfully to capture microstructural effects to polymeric materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40882.

Research paper thumbnail of Quantification of damage evolution in a 7075 aluminum alloy using an acoustic emission technique

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011

The use of acoustic emission for quantifying the microstructural damage evolution under tensile l... more The use of acoustic emission for quantifying the microstructural damage evolution under tensile loading is studied for a 7075 aluminum alloy. First, the cracking of intermetallic particles present in the material was evaluated using interrupted tensile tests combined with digital image analysis of large optical image montages. Subsequent acoustic emission tests under tensile monotonic loading produced an in situ signature that correlated with the quantitative stereology results obtained destructively. Acoustic emission is a viable option for quantifying the evolution of microstructure damage in terms of particle cracking for the 7075 alloy.