James Earthman - Profile on Academia.edu (original) (raw)
Papers by James Earthman
High temperature intergranular crack growth processes in copper and copper with 1 wt% antimony
Acta Metallurgica, 1985
ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K u... more ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K under various loading conditions. The presence of Sb in Cu facilitates brittle intergranular fracture at low temperatures and permits a study of cavitation at the crack tip using SEM techniques. Steep gradients in cavitation damage are observed under constant load conditions wherein the crack accelerates in the course of growth. With a constant stress intensity factor, the crack decelerates during growth and the cavitation spreads evenly over the ligament ahead of the crack tip. The crack growth rate is compared with the stress intensity factor and C*, which have been determined for different loading conditions. Results similar to those of Landes and Begley were obtained, indicating that C*, evaluated experimentally, correlates with crack growth rate under constant displacement rate conditions. Crack growth under constant displacement rate conditions can be described by a simple steady state model.
An evaluation of quantitative percussion diagnostics for determining the probability of a microgap defect in restored and unrestored teeth: A prospective clinical study
The Journal of Prosthetic Dentistry
Trans Tech Publications Ltd. eBooks, Nov 15, 2005
Atomic layer deposition (ALD) enables deposition of dense nanometer thick metal oxide nanoshells ... more Atomic layer deposition (ALD) enables deposition of dense nanometer thick metal oxide nanoshells on powder particles with precise thickness control. This leads to products with low weight fraction coating, also when depositing on nano-or micron sized powder particles. This study aimed at investigating the aluminium oxide nanoshell thickness required to prevent moisture sorption. The nanoshells were produced with ALD on spray-dried lactose, which is amorphous and extremely hygroscopic. The particles were studied with dynamic vapor sorption between 0 to 50% RH, light scattering, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and polarized light microscopy. The ALD did not induce any recrystallization of the amorphous lactose. The dynamic vapor sorption indicated that the moisture sorption was almost completely inhibited by the nanoshell. Neat amorphous lactose rapidly recrystallized upon moisture exposure. However, only ca. 15% of the amorphous lactose particles recrystallized of a sample with 9% (by weight) aluminium oxide nanoshell at storage for six months upon 75% RH/40°C, which indicate that the moisture sorption was completely inhibited in the majority of the particles. In conclusion, the aluminium oxide nanoshells prevented moisture sorption and dramatically improved the long term physical stability of amorphous lactose. This shows the potential of the ALD-technique to protect drug microparticles. Abbreviations ALD, atomic layer deposition; Cp Tg , magnitude of the step change in heat capacity at the glass transition temperature; DVS
Laser scanning crack detection for fine wire fatigue testing
Although fine wire is used in a variety of important applications, from massive woven ropes which... more Although fine wire is used in a variety of important applications, from massive woven ropes which support bridges to microcircuit connecting leads, the equipment and techniques for determining a wire product`s lifetime are not well developed. This can be largely attributed to the practical difficulties associated with testing sub-millimeter sized specimens. Since large specimens are not appropriate for evaluating the fatigue properties of fine wires, there is a need for a crack detection and monitoring technique that can be directly applied to the wires themselves. This presentation provides a description of a novel scanning laser crack detection technique that has been developed to detect fatigue cracking in specimens made directly from fine wire.
Journal of The Korean Society of Civil Engineers, Mar 1, 1991
Metallurgical and Materials Transactions, Nov 10, 2017
Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks ... more Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks per second detected using a laser beam that is scanned across a surface at a constant predetermined frequency. In the present article, a mechanistic approach was taken to develop a methodology for deducing crack length and crack growth information from defect frequency data generated from laser scanning measurements made on fatigued surfaces. The method was developed by considering a defect frequency vs fatigue cycle curve that comprised three regions: (i) a crack initiation regime of rising defect frequency, (ii) a plateau region of a relatively constant defect frequency, and (iii) a region of rapid rising defect frequency due to crack growth. Relations between defect frequency and fatigue cycle were developed for each of these three regions and utilized to deduce crack depth information from laser scanning data of 7075-T6 notched specimens. The proposed method was validated using experimental data of crack density and crack length data from the literature for a structural steel. The proposed approach was successful in predicting the length or depth of small fatigue cracks in notched 7075-T6 specimens and in smooth fatigue specimens of a structural steel.
Introduction to Creep and Stress-Relaxation Testing
Proceedings of SPIE, Aug 18, 2005
Single crystal Lithium Fluoride (LiF) has been base-lined as one of the optical materials for the... more Single crystal Lithium Fluoride (LiF) has been base-lined as one of the optical materials for the Near Infra-Red Camera (NIRCam) on the James Webb Space Telescope (JWST). Optically, this material is outstanding for use in the near IR. Unfortunately, it has poor mechanical properties that make it very difficult for use in any appreciable size on cryogenic space based instruments. In addition to a dL/L from 300K to 30K of ~-0.48% and room temperature CTE of ~37ppm/K, LiF deforms plastically under relatively small stresses. This paper will discuss the heritage of LiF in space-based systems and summarize the mechanical and thermal material data for LiF that is available in the literature. New data will be presented relative to a design limit load for the material so that designers can use this material for space flight applications. Additional new data relative to the cryogenic index of refraction of the material over the near infrared is also provided.
High temperature intergranular crack growth processes in copper and copper with 1 wt% antimony
Acta Metallurgica, May 1, 1985
ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K u... more ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K under various loading conditions. The presence of Sb in Cu facilitates brittle intergranular fracture at low temperatures and permits a study of cavitation at the crack tip using SEM techniques. Steep gradients in cavitation damage are observed under constant load conditions wherein the crack accelerates in the course of growth. With a constant stress intensity factor, the crack decelerates during growth and the cavitation spreads evenly over the ligament ahead of the crack tip. The crack growth rate is compared with the stress intensity factor and C*, which have been determined for different loading conditions. Results similar to those of Landes and Begley were obtained, indicating that C*, evaluated experimentally, correlates with crack growth rate under constant displacement rate conditions. Crack growth under constant displacement rate conditions can be described by a simple steady state model.
An evaluation of quantitative percussion diagnostics for determining the probability of a microgap defect in restored and unrestored teeth: A prospective clinical study
Journal of Prosthetic Dentistry, May 1, 2023
Quantitative percussion diagnostics for evaluating porosity and surface roughness of cold sprayed and laser deposited materials
Journal of materials research and technology, Sep 1, 2021
Abstract Quantitative percussion diagnostics (QPD) is a non-destructive evaluation method that ha... more Abstract Quantitative percussion diagnostics (QPD) is a non-destructive evaluation method that has been used successfully in a number of applications. This technique involves a rod that is actuated to impact a specimen with a given amount of kinetic energy and the resulting mechanical response of the specimen as a function of time is measured using a piezoelectric force sensor. The mechanical energy returned to the rod is then analyzed. Because contact with the specimen is on the order of a few hundred microseconds, QPD can be used in situations and for specimen conditions (e.g. high temperature) that are not feasible for other nondestructive testing methods. The objective of the present study was to evaluate the use of QPD for characterization of defects in specimens fabricated using two additive manufacturing methods, i.e. cold spray deposition and laser powder directed energy deposition (LPDED). Cold spray specimens were produced using commercially pure nickel with varied process conditions including gas type (i.e. helium and nitrogen) and deposition rate. In addition, a Ti–6Al–4V specimen was manufactured using LPDED with varying porosity content. All specimens were characterized using both QPD and destructive methods (i.e. cross-sectional metallography) to compare results for observed defect characteristics. Cold spray specimens exhibited a lower energy return when they contained more porosity and/or surface roughness. Microscopic plastic deformation at highly porous surfaces was indicated during percussion testing that reached a saturation level after repeated percussion. Overall, the results showed that QPD can effectively evaluate cold spray and LPDED specimens for porosity and surface roughness.
The Effect of Heat Treatment on the Corrosion Resistance of 440C Stainless Steel in 20% HNO<SUB>3</SUB> + 2.5% Na<SUB>2</SUB>Cr<SUB>2</SUB>O<SUB>7</SUB> Solution
Journal of Materials Engineering and Performance, Apr 1, 2003
The effect of heat treatment on the corrosion resistance of 440C stainless steel was investigated... more The effect of heat treatment on the corrosion resistance of 440C stainless steel was investigated in a 20% HNO3 + 2.5% Na2Cr2O7 solution using electrochemical noise (ECN) measurements, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) examinations. The noise resistance (Rn), which has been found to be inversely related to the localized corrosion rate, was measured to be 5.7E
ACS Applied Materials & Interfaces, Aug 31, 2020
Nanobubbles have been widely studied for their use in water treatments. Conventional methods for ... more Nanobubbles have been widely studied for their use in water treatments. Conventional methods for producing nanobubbles require significantly high levels of electric power. A system that involves inducing an alternative magnetic field (AMF) in flowing water has been developed which has relatively low power requirements compared to other methods. Experimental results are presented that indicate nanobubbles are generated by this AMF system. These results include zeta potential measurements in deionized water, light scattering observations and nanoparticle tracking analysis (NTA) measurements of object size and relative scattering intensity for water containing 510-4 M CaCO 3. The NTA results also suggest the formation of nanobubblenanoparticle clusters. Finally, an earlier work is reviewed which demonstrated that this AMF treatment led to the removal of tubercles on the inner walls of pipe samples. This prior result is discussed in light of the present evidence of nanobubble formation and a hypothesis is proposed based on the dissolution of CaCO 3 as a result of nanobubble-nanoparticle clustering.
Creep and fracture of engineering materials and structures : proceedings of the Seventh International Conference held at the University of California, Irvine, August 10-15, 1997
Minerals, Metals & Materials Society eBooks, 1997
The Effect of Electrical Discharge Machining on Electro-Deposited Nano-Crystalline Ni Sheet
Microscopy and Microanalysis, Aug 1, 2007
Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Fl... more Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007
Journal of Materials Research, Aug 1, 1997
X-ray diffraction (XRD) technique has been used to characterize the low cycle fatigue (LCF) damag... more X-ray diffraction (XRD) technique has been used to characterize the low cycle fatigue (LCF) damage in 9Cr-1Mo ferritic steel. In this study, full-width at half-maximum (FWHM) of the XRD peak has been measured for assessing the fatigue damage. Fully reversed totalaxial-strain controlled fatigue tests have been performed at ambient temperature (300 K) at strain amplitudes of^0.25%,^0.50% and0 .75%. FWHM measurement of {3 1 0} plane has been carried out on specimens interrupted at different fatigue life fractions, which represent the various stages of deformation and fracture such as cyclic hardening, cyclic softening, saturation and surface crack initiation and propagation. The cyclic hardening, which occurred in the early stages of fatigue deformation, exhibited broadening of diffraction profile and a rapid increase in the FWHM at all strain amplitudes. Also, large oscillations were observed in the d(2u) vs. sin 2 C curves. With further cycling, FWHM remained almost constant in the softening and saturation stages. Finally, at the onset of rapid stress drop in the cyclic stress response and cusp formation in the compression portions of stress-strain hysteresis loops, which indicate surface crack initiation and propagation, a rapid decrease in FWHM was observed. This drop in FWHM is attributed to relieving of microstresses owing to surface crack initiation and propagation. Relieving of micro stresses has also been confirmed by a significant reduction in oscillations in the d(2u) vs. sin 2 C curves.
Change of structure, creep fatigue behaviour and life of X 20 CrMoV 12 1
Reduction of calcified plaque volume in ex vivo pericardial tissue, with nanobubbles
Colloids and Surfaces B: Biointerfaces
Scanning Laser Detection of Crack Precursors in High RAP Content Asphalt Mixture with Improved Fatigue Performance
Formation of microcracks under fatigue conditions is a complex mechanism and difficult to detect.... more Formation of microcracks under fatigue conditions is a complex mechanism and difficult to detect. A microcrack is not apparent until late in fatigue life of the section. However, structural changes and microcracks can occur earlier and could be used as an originator for fatigue crack formations that lead to failure. Therefore, it is important to develop methods to promptly detect microcracks early in fatigue life well in advance of macrocrack growth. This paper presents the test procedure and analysis approach developed for a non-contact Scanning Laser Detection (SLD) for capturing and monitoring cracks in asphalt mixtures. The study focuses on utilizing SLD to investigate damage resistance of asphalt mixtures containing high Recycled Asphalt Pavement (RAP) content. Use of more RAP in asphalt materials is becoming increasingly popular due to the economic and environmental benefits of recycled materials. On the other hand, stiffer mixes resulting from RAP addition has raised concern ...
NANO HIGHLIGHT Ideal Strength and Nanomechanics
High temperature intergranular crack growth processes in copper and copper with 1 wt% antimony
Acta Metallurgica, 1985
ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K u... more ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K under various loading conditions. The presence of Sb in Cu facilitates brittle intergranular fracture at low temperatures and permits a study of cavitation at the crack tip using SEM techniques. Steep gradients in cavitation damage are observed under constant load conditions wherein the crack accelerates in the course of growth. With a constant stress intensity factor, the crack decelerates during growth and the cavitation spreads evenly over the ligament ahead of the crack tip. The crack growth rate is compared with the stress intensity factor and C*, which have been determined for different loading conditions. Results similar to those of Landes and Begley were obtained, indicating that C*, evaluated experimentally, correlates with crack growth rate under constant displacement rate conditions. Crack growth under constant displacement rate conditions can be described by a simple steady state model.
An evaluation of quantitative percussion diagnostics for determining the probability of a microgap defect in restored and unrestored teeth: A prospective clinical study
The Journal of Prosthetic Dentistry
Trans Tech Publications Ltd. eBooks, Nov 15, 2005
Atomic layer deposition (ALD) enables deposition of dense nanometer thick metal oxide nanoshells ... more Atomic layer deposition (ALD) enables deposition of dense nanometer thick metal oxide nanoshells on powder particles with precise thickness control. This leads to products with low weight fraction coating, also when depositing on nano-or micron sized powder particles. This study aimed at investigating the aluminium oxide nanoshell thickness required to prevent moisture sorption. The nanoshells were produced with ALD on spray-dried lactose, which is amorphous and extremely hygroscopic. The particles were studied with dynamic vapor sorption between 0 to 50% RH, light scattering, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and polarized light microscopy. The ALD did not induce any recrystallization of the amorphous lactose. The dynamic vapor sorption indicated that the moisture sorption was almost completely inhibited by the nanoshell. Neat amorphous lactose rapidly recrystallized upon moisture exposure. However, only ca. 15% of the amorphous lactose particles recrystallized of a sample with 9% (by weight) aluminium oxide nanoshell at storage for six months upon 75% RH/40°C, which indicate that the moisture sorption was completely inhibited in the majority of the particles. In conclusion, the aluminium oxide nanoshells prevented moisture sorption and dramatically improved the long term physical stability of amorphous lactose. This shows the potential of the ALD-technique to protect drug microparticles. Abbreviations ALD, atomic layer deposition; Cp Tg , magnitude of the step change in heat capacity at the glass transition temperature; DVS
Laser scanning crack detection for fine wire fatigue testing
Although fine wire is used in a variety of important applications, from massive woven ropes which... more Although fine wire is used in a variety of important applications, from massive woven ropes which support bridges to microcircuit connecting leads, the equipment and techniques for determining a wire product`s lifetime are not well developed. This can be largely attributed to the practical difficulties associated with testing sub-millimeter sized specimens. Since large specimens are not appropriate for evaluating the fatigue properties of fine wires, there is a need for a crack detection and monitoring technique that can be directly applied to the wires themselves. This presentation provides a description of a novel scanning laser crack detection technique that has been developed to detect fatigue cracking in specimens made directly from fine wire.
Journal of The Korean Society of Civil Engineers, Mar 1, 1991
Metallurgical and Materials Transactions, Nov 10, 2017
Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks ... more Defect frequency, a fatigue crack prognostics indicator, is defined as the number of microcracks per second detected using a laser beam that is scanned across a surface at a constant predetermined frequency. In the present article, a mechanistic approach was taken to develop a methodology for deducing crack length and crack growth information from defect frequency data generated from laser scanning measurements made on fatigued surfaces. The method was developed by considering a defect frequency vs fatigue cycle curve that comprised three regions: (i) a crack initiation regime of rising defect frequency, (ii) a plateau region of a relatively constant defect frequency, and (iii) a region of rapid rising defect frequency due to crack growth. Relations between defect frequency and fatigue cycle were developed for each of these three regions and utilized to deduce crack depth information from laser scanning data of 7075-T6 notched specimens. The proposed method was validated using experimental data of crack density and crack length data from the literature for a structural steel. The proposed approach was successful in predicting the length or depth of small fatigue cracks in notched 7075-T6 specimens and in smooth fatigue specimens of a structural steel.
Introduction to Creep and Stress-Relaxation Testing
Proceedings of SPIE, Aug 18, 2005
Single crystal Lithium Fluoride (LiF) has been base-lined as one of the optical materials for the... more Single crystal Lithium Fluoride (LiF) has been base-lined as one of the optical materials for the Near Infra-Red Camera (NIRCam) on the James Webb Space Telescope (JWST). Optically, this material is outstanding for use in the near IR. Unfortunately, it has poor mechanical properties that make it very difficult for use in any appreciable size on cryogenic space based instruments. In addition to a dL/L from 300K to 30K of ~-0.48% and room temperature CTE of ~37ppm/K, LiF deforms plastically under relatively small stresses. This paper will discuss the heritage of LiF in space-based systems and summarize the mechanical and thermal material data for LiF that is available in the literature. New data will be presented relative to a design limit load for the material so that designers can use this material for space flight applications. Additional new data relative to the cryogenic index of refraction of the material over the near infrared is also provided.
High temperature intergranular crack growth processes in copper and copper with 1 wt% antimony
Acta Metallurgica, May 1, 1985
ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K u... more ABSTRACT Creep crack growth in Cu and Cu + 1 wt% Sb has been studied at temperatures near 773 K under various loading conditions. The presence of Sb in Cu facilitates brittle intergranular fracture at low temperatures and permits a study of cavitation at the crack tip using SEM techniques. Steep gradients in cavitation damage are observed under constant load conditions wherein the crack accelerates in the course of growth. With a constant stress intensity factor, the crack decelerates during growth and the cavitation spreads evenly over the ligament ahead of the crack tip. The crack growth rate is compared with the stress intensity factor and C*, which have been determined for different loading conditions. Results similar to those of Landes and Begley were obtained, indicating that C*, evaluated experimentally, correlates with crack growth rate under constant displacement rate conditions. Crack growth under constant displacement rate conditions can be described by a simple steady state model.
An evaluation of quantitative percussion diagnostics for determining the probability of a microgap defect in restored and unrestored teeth: A prospective clinical study
Journal of Prosthetic Dentistry, May 1, 2023
Quantitative percussion diagnostics for evaluating porosity and surface roughness of cold sprayed and laser deposited materials
Journal of materials research and technology, Sep 1, 2021
Abstract Quantitative percussion diagnostics (QPD) is a non-destructive evaluation method that ha... more Abstract Quantitative percussion diagnostics (QPD) is a non-destructive evaluation method that has been used successfully in a number of applications. This technique involves a rod that is actuated to impact a specimen with a given amount of kinetic energy and the resulting mechanical response of the specimen as a function of time is measured using a piezoelectric force sensor. The mechanical energy returned to the rod is then analyzed. Because contact with the specimen is on the order of a few hundred microseconds, QPD can be used in situations and for specimen conditions (e.g. high temperature) that are not feasible for other nondestructive testing methods. The objective of the present study was to evaluate the use of QPD for characterization of defects in specimens fabricated using two additive manufacturing methods, i.e. cold spray deposition and laser powder directed energy deposition (LPDED). Cold spray specimens were produced using commercially pure nickel with varied process conditions including gas type (i.e. helium and nitrogen) and deposition rate. In addition, a Ti–6Al–4V specimen was manufactured using LPDED with varying porosity content. All specimens were characterized using both QPD and destructive methods (i.e. cross-sectional metallography) to compare results for observed defect characteristics. Cold spray specimens exhibited a lower energy return when they contained more porosity and/or surface roughness. Microscopic plastic deformation at highly porous surfaces was indicated during percussion testing that reached a saturation level after repeated percussion. Overall, the results showed that QPD can effectively evaluate cold spray and LPDED specimens for porosity and surface roughness.
The Effect of Heat Treatment on the Corrosion Resistance of 440C Stainless Steel in 20% HNO<SUB>3</SUB> + 2.5% Na<SUB>2</SUB>Cr<SUB>2</SUB>O<SUB>7</SUB> Solution
Journal of Materials Engineering and Performance, Apr 1, 2003
The effect of heat treatment on the corrosion resistance of 440C stainless steel was investigated... more The effect of heat treatment on the corrosion resistance of 440C stainless steel was investigated in a 20% HNO3 + 2.5% Na2Cr2O7 solution using electrochemical noise (ECN) measurements, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) examinations. The noise resistance (Rn), which has been found to be inversely related to the localized corrosion rate, was measured to be 5.7E
ACS Applied Materials & Interfaces, Aug 31, 2020
Nanobubbles have been widely studied for their use in water treatments. Conventional methods for ... more Nanobubbles have been widely studied for their use in water treatments. Conventional methods for producing nanobubbles require significantly high levels of electric power. A system that involves inducing an alternative magnetic field (AMF) in flowing water has been developed which has relatively low power requirements compared to other methods. Experimental results are presented that indicate nanobubbles are generated by this AMF system. These results include zeta potential measurements in deionized water, light scattering observations and nanoparticle tracking analysis (NTA) measurements of object size and relative scattering intensity for water containing 510-4 M CaCO 3. The NTA results also suggest the formation of nanobubblenanoparticle clusters. Finally, an earlier work is reviewed which demonstrated that this AMF treatment led to the removal of tubercles on the inner walls of pipe samples. This prior result is discussed in light of the present evidence of nanobubble formation and a hypothesis is proposed based on the dissolution of CaCO 3 as a result of nanobubble-nanoparticle clustering.
Creep and fracture of engineering materials and structures : proceedings of the Seventh International Conference held at the University of California, Irvine, August 10-15, 1997
Minerals, Metals & Materials Society eBooks, 1997
The Effect of Electrical Discharge Machining on Electro-Deposited Nano-Crystalline Ni Sheet
Microscopy and Microanalysis, Aug 1, 2007
Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Fl... more Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007
Journal of Materials Research, Aug 1, 1997
X-ray diffraction (XRD) technique has been used to characterize the low cycle fatigue (LCF) damag... more X-ray diffraction (XRD) technique has been used to characterize the low cycle fatigue (LCF) damage in 9Cr-1Mo ferritic steel. In this study, full-width at half-maximum (FWHM) of the XRD peak has been measured for assessing the fatigue damage. Fully reversed totalaxial-strain controlled fatigue tests have been performed at ambient temperature (300 K) at strain amplitudes of^0.25%,^0.50% and0 .75%. FWHM measurement of {3 1 0} plane has been carried out on specimens interrupted at different fatigue life fractions, which represent the various stages of deformation and fracture such as cyclic hardening, cyclic softening, saturation and surface crack initiation and propagation. The cyclic hardening, which occurred in the early stages of fatigue deformation, exhibited broadening of diffraction profile and a rapid increase in the FWHM at all strain amplitudes. Also, large oscillations were observed in the d(2u) vs. sin 2 C curves. With further cycling, FWHM remained almost constant in the softening and saturation stages. Finally, at the onset of rapid stress drop in the cyclic stress response and cusp formation in the compression portions of stress-strain hysteresis loops, which indicate surface crack initiation and propagation, a rapid decrease in FWHM was observed. This drop in FWHM is attributed to relieving of microstresses owing to surface crack initiation and propagation. Relieving of micro stresses has also been confirmed by a significant reduction in oscillations in the d(2u) vs. sin 2 C curves.
Change of structure, creep fatigue behaviour and life of X 20 CrMoV 12 1
Reduction of calcified plaque volume in ex vivo pericardial tissue, with nanobubbles
Colloids and Surfaces B: Biointerfaces
Scanning Laser Detection of Crack Precursors in High RAP Content Asphalt Mixture with Improved Fatigue Performance
Formation of microcracks under fatigue conditions is a complex mechanism and difficult to detect.... more Formation of microcracks under fatigue conditions is a complex mechanism and difficult to detect. A microcrack is not apparent until late in fatigue life of the section. However, structural changes and microcracks can occur earlier and could be used as an originator for fatigue crack formations that lead to failure. Therefore, it is important to develop methods to promptly detect microcracks early in fatigue life well in advance of macrocrack growth. This paper presents the test procedure and analysis approach developed for a non-contact Scanning Laser Detection (SLD) for capturing and monitoring cracks in asphalt mixtures. The study focuses on utilizing SLD to investigate damage resistance of asphalt mixtures containing high Recycled Asphalt Pavement (RAP) content. Use of more RAP in asphalt materials is becoming increasingly popular due to the economic and environmental benefits of recycled materials. On the other hand, stiffer mixes resulting from RAP addition has raised concern ...
NANO HIGHLIGHT Ideal Strength and Nanomechanics