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Biopolymer stabilization of clayey soil

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2801-2812页

作者： Mahdieh azimi amin Soltani Mehdi Mirzababaei Mark B.Jaksa Nanjappa Ashwath College of Engineering and Aviation School of Engineering and TechnologyCQUniversityMelbourneVIC 3000Australia Institute of Innovation Science and Sustainabilityand Future Regions Research CenterFederation UniversityChurchillVIC 3842Australia Department of Infrastructure Engineering Faculty of Engineering and Information TechnologyThe University of MelbourneParkvilleVIC 3010Australia School of Architecture and Civil Engineering The University of AdelaideAdelaideSA 5005Australia School of Health Medical and Applied SciencesCQUniversityRockhamptonQLD 4701Australia

This study investigates the efficacy of sodium alginate(SA),xanthan gum(XG),guar gum(GG)and chitosan(CS)d each applied at five different solid biopolymer-to-water mass ratios(or dosages)and cured for 7 d and 28 d d on the unconfined compressive strength(UCS)performance of a high plasticity clayey ***,on identifying the optimum biopolymer-treatment scenarios,their performance was compared against conventional stabilization using hydrated *** a given curing time,the UCS for all biopolymers followed a riseefall trend with increasing biopolymer dosage,peaking at an optimum dosage and then subsequently decreasing,such that all biopolymer-stabilized samples mobilized higher UCS values compared to the unamended *** optimum dosage was found to be 1.5%for SA,XG and CS,while a notably lower dosage of 0.5%was deemed optimum for ***,for a given biopolymer type and dosage,increasing the curing time from 7 d to 28 d further enhanced the UCS,with the achieved improvements being generally more pronounced for XG-and CS-treated *** of the investigated biopolymers was able to produce UCS improvements equivalent to those obtained by the 28-d soilelime samples;however,the optimum XG,GG and CS dosages,particularly after 28 d of curing,were easily able to replicate 7-d lime stabilization outcomes achieved with as high as twice the soil’s lime ***,the fundamental principles of clay chemistry,in conjunction with the soil mechanics framework,were employed to identify and discuss the clayebiopolymer stabilization mechanisms.

关键词： Soil stabilization High plasticity clay Biopolymer dosage Hydrated lime Curing time Unconfined compressive strength(UCS)

Microstructure and Quasi-Static Mechanical Behavior of Cryoforged AA2519 Alloy

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Materials Sciences and Applications 2019年第2期10卷 137-149页

作者： amin azimi Gbadebo Moses Owolabi Hamid Fallahdoost Nikhil Kumar Horace Whitworth Department of Mechanical Engineering Howard University Washington DC USA Department of Mechanical Engineering Materials Science and Engineering Program Binghamton University (SUNY) Binghamton NY USA

In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-static loading were investigated to determine the influence of cryogenic forging on alloys’ subgrains dimensions, grain boundaries interactions, strength, ductility and toughness. In addition, the failure mechanisms at the tensile rupture surfaces were characterized using scanning electron micro-scope (SEM). The results show significant improvements in the strength, ductility and toughness of the alloy as a result of the cryogenic MAF process. The formation of nanoscale crystallite microstructure, heavily deformed grains with high density of grain boundaries and second phase breakage to finer particles were characterized as the main reasons for the increase in the mechanical properties of the cryogenic forged samples. The cryogenic processing of the alloy resulted in the formation of an ultrafine grained material with tensile strength and toughness that are ~41% and ~80% higher respectively after 2 cycles MAF when compared with the materials processed at ambient temperature. The fractography analysis on the tested materials shows a substantial ductility improvement in the cryoforged (CF) samples when compared to the room temperature forged (RTF) samples which is in alignment with their stress-strain profiles. However, extended forging at higher cycles than 2 cycles led only to increase in strength at the expense of ductility for both the CF and RTF samples.

关键词： AA2519 Aluminum Alloy Cryogenic Forging Quasi-Static Mechanical Behavior Microstructure Investigation Fractography Analysis

The Effects of Build Parameters and Strain Rate on the Mechanical Properties of FDM 3D-Printed Acrylonitrile Butadiene Styrene

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Open Journal of Organic Polymer Materials 2019年第1期9卷 1-27页

作者： Kemar Hibbert Grant Warner Celeste Brown Olusegun Ajide Gbadebo Owolabi amin azimi Department of Mechanical Engineering Howard University Washington DC USA Department of Mechanical Engineering University of Ibadan Ibadan Nigeria

In this paper, the effects of build parameters on the mechanical properties of 3D-printed acrylonitrile butadiene styrene (ABS) produced using fused deposition modeling (FDM) are investigated. Full factorial experimental design incorporating a 2-level, 3-factor design with raster angle, layer thickness and interior fill style was carried out. Tensile tests were performed at four different strain rates to determine how the build parameters influence the mechanical properties of the 3-D printed ABS and to assess its strain rate sensitivity under quasi-static loading. It was found that the modulus of toughness of ABS material is most influenced by raster angle, while the interior fill style is the most dominant build parameter that dictates the specimen’s modulus of resilience, yield strength and ultimate tensile strength. At all strain rates, it is further revealed that higher mean values of yield strength, ultimate tensile strength and modulus of resilience were obtained when the interior fill style is solid as opposed to high density. This can be attributed to the denser structure and higher effective cross-sectional area in solid interior fill style in comparison with high density interior fill style. However, the influence of the layer thickness on the investigated mechanical properties was found to be inconsistent. It was noted that specimens built with both 0.254 mm layer thickness and the cross [0°/90°] raster angle had superior mechanical properties when compared to those built with the 0.3302 mm layer thickness and cross [0°/90°] raster angle. This suggests that there is a key interaction between the layer thickness and the raster angle. At any FDM build parameter, it was found that all the mechanical properties investigated in this work exhibited modest sensitivity to strain rates. This study has provided a platform for an appropriate selection of build parameters combinations and strain rates for additive manufacturing of 3D-printed ABS with improved mechan

关键词： Build Parameters Mechanical Properties Additive Manufacturing 3D Printing Acrylonitrile Butadiene Styrene

Fatigue Responses of Three AA 2000 Series Aluminum Alloys

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Journal of Materials Science and Chemical Engineering 2019年第3期7卷 32-48页

作者： Gbadebo Moses Owolabi Mark Thom Olusegun Ajide Nikhil Kumar amin azimi Horace Whitworth Grant Warner Department of Mechanical Engineering Howard University Washington DC USA Department of Mechanical Engineering University of Ibadan Ibadan Nigeria

In this paper, smooth specimens of three aluminum alloys: AA 2219-T8, AA 2519-T8 and AA 2624-T351, were subjected to the same level of uniaxial (tension/compression) fatigue loading to compare their fatigue responses. Fractographic investigations of the failed specimens after fatigue loading was also conducted using a scanning electron microscope. The fatigue test results showed considerable differences in the fatigue lives of the three investigated alloys with AA 2219-T8 having the shortest fatigue life and AA 2624-T351 the longest fatigue life. The fractographic analysis showed that coalescence of micropores, microvoids, particles cleavage and microcracks are the predominant features in the fracture surface of AA 2219-T8. The fracture surface features of AA 2519-T8 revealed higher resistance to fatigue cracks nucleation and growth when compared to AA 2219-T8. The features depicted mainly partly ductile and partly brittle fracture. The AA 2624-T351 fracture surface features revealed noteworthy ductile failure mechanism. The results suggest a strong correlation between the surface fractographic features and the fatigue lives of the alloys. It is also observed that in addition to the yield strengths and ultimate tensile strengths, the total strain energy densities (SED) may provide a reasonable indication of the relative fatigue performance of the three alloys. AA 2219-T8 had the lowest SED and the lowest fatigue life, while AA 2624-T351 had the highest SED and the highest fatigue life. Thus, AA 2624-T351 would be the most suitable materials for components subjected to fatigue loading.

关键词： Fatigue Life Aluminum Alloy Strain Energy Density Fractography

A global overview of the most important zoonotic bacteria pathogens transmitted from Rattus norvegicus to humans in urban environments

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Infectious Medicine 2022年第3期1卷 192-207页

作者： Sahar Sabour Taher azimi Ahmad Nasser Nahal Hadi amin Mohsenzadeh Aref Shariati Department of Microbiology Faculty of MedicineAhvaz Jundishapur University of Medical SciencesAhvazIran Department of Bacteriology&Virology School of MedicineShiraz University of Medical ScienceShirazIran Department of Pathobiology School of Public HealthTehran University of Medical SciencesTehranIran Department of Microbiology Ardabil BranchIslamic Azad UniversityArdabilIran Molecular and medicine research center Khomein University of Medical SciencesKhomeinIran

Zoonotic pathogens,comprising over 61%of all pathogenic microorganisms,can be transmitted from different animals to individuals in numerous ways either in the presence or the absence of a *** new emerging human infectious diseases,these pathogens could be categorized into 4 groups,bacteria,viruses,parasites,and *** the wide range of reservoirs for zoonotic pathogens,tremendous attention has been attracted to wild rats,due to their global distribution not only in urban environments but also in the sylvatic and agricultural *** the nonce,zoonotic bacteria transmitted via wild rats have turned into a global public health problem probably due to their ability to induce re-emerging diseases even after eradication and controlling *** the importance of wild rats in spreading pathogens,little data are available about the bacterial diversity present in urban wild rat *** this review,we present a complete list of zoonotic bacterial pathogens isolated from wild rats in urban environments.

关键词： Zoonosis Bacterial diseases Zoonotic diseases Wild rats Rattus rattus