Modeling dynamic behavior of metal matrix composites

Thesis (Master)--Izmir Institute of Technology, Materials Science and Engineering, Izmir, 2002Includes bibliographical references (leaves: 73-76)Text in English; Abstract: Turkish and Englishx, 84 leavesA numerical investigation has been conducted on the strain rate dependent compression mechanical behavior of a SiC-particulate reinforced Al (2024-O) metal matrix composite. The effect of particle volume fraction on the strain rate sensitivity of the composite was determined using axisymmetric Finite Element unit cell models, where the particles are treated as elastic spheres embedded within a visco-plastic matrix, implemented in LUSAS Finite Element Analysis program. Particles are taken to be elastic, equal-sized, spherical and uniformly distributed in the matrix. The strain rate dependent constitutive behavior of the matrix material uses a linear relation between stress and strain rate formulation and is obtained from independent experimental results on the matrix. The flow stress of the composites is predicted over a range of strain rates for different particle volume fractions. Numerical results of the flow stress and strain rate sensitivity of the composite were also compared with those of experimental results, for 15% SiC particle reinforced 2024-O Al metal matrix composite. Influence of particle shape on the behavior of the MMC at high strain rates is also investigated. A unit cell, which is an elastic cylinder embedded within a visco-plastic matrix, is used. It is also shown that the rate dependent flow stress and local stress in the microstructure are influenced by particle shape. If reinforcement edge sharpness increases, local stress increases at that area. The results show that both the flow stress and the strain rate sensitivity increase with increasing volume fraction of the reinforcement due to the constraining effect of the reinforcement. Numerical calculations have shown an increased strain rate sensitivity of the composite over the matrix alloy. The discrepancy found between numerical and experimental results was finally discussed based on geometrical and microstructural parameters that might affect the composite flow stress and strain rate sensitivity

JOURNAL OF ANALYTICAL CHEMISTRY

Responses of organic fluorophore, perylenediimide derivative N,N'-di[3-[2-(3-thienyl)ethyl]phenyl]perylene-3,4,9,10-bis-(dicarboxyimide) (PDI1) was investigated in polymer matrix of polyvinyl chloride (PVC) by emission spectrometry. Its response to Fe(III) ions was evaluated in terms of the effect of pH. The properties of time dependent response, reversibility, limit of detection, linear concentration range for the metal ion and repeatability characteristics of the sensing element also have been studied. The offered sensor exhibited remarkable fluorescence intensity quenching at pH 6.0 in the concentration range of 1 x 10(-6) to 2.5 x 10(-3) M Fe(III) ions. The reproducibility of the sensor membrane was investigated by alternately changing the solution between 1 x 10(-4) M Fe(III) in Na2HPO4 (4 x 10(-2) M) and NaH2PO4 buffer (2 x 10(-3) M)

DESALINATION AND WATER TREATMENT

A simple and effective biodegradable material known as chitosan-clay composite beads were prepared to remove Pb(II) ions from aqueous solution. For this purpose, various important parameters such as contact time, pH and temperature were examined on the adsorption of Pb(II) ions onto crosslinked chitosan-clay composite beads. Maximum adsorption capacity of Pb(II) was observed at pH 4.5 and 25 degrees C and calculated as 7.93 mg/g according to Langmuir isotherm model. Thermodynamic parameters namely Delta G degrees, Delta H degrees and Delta S degrees of the Pb(II) adsorption process have been calculated as 7.889 kJ/mol, -15.131 kJ/mol and -0.0785 kJ/molK respectively. EDTA was the best eluent for the desorption of Pb(II) ions from the crosslinked chitosan-clay beads. Scanning electron microscope (SEM) was used to characterize the surface morphology of the crosslinked chitosan-clay beads

Akusto optik filtreli edfa modülünün yapay sinir ağı ile kazanç düzleme kontrolü

EKFYʼnin (Erbiyum Katkılı Fiber Yükselteçler) lineer olmayan kazanç karakteristiği nedeniyle farklı dalga boylarında farklı kazançlar elde edilmektedir. Geleneksel EKFYʼlerde düz çıkış profili elde etmek için EKFY iki aşamalı olarak düzenlenmiş ve arada sabit filtreler kullanılmıştır. Ancak değişken girişlere karşı filtrenin de değişmesi gerektiğinden ayarlanabilir akusto optik filtreler geliştirilmiştir. Bu filtrelerin kontrolü için ise EKFYʼnin matematik modelini de kapsayan karmaşık hesaplamalar yapılmalıdır. Bu hesaplamaların yapılması uzun sürmekte ve gerçek zamanlı uygulamalarda verimsiz olmaktadır. Bu çalışmada, gerçek zamanlı çalışmaya uygun olarak hesaplamaların yapay sinir ağı tarafından yapılması amaçlanmıştır. Önce EKFYʼnin matematiksel modeli elde edilmiştir. İki aşamalı EKFY yapısında belirli bir pompa gücü için optimum EKFY uzunluğu ve optimum filtre konumu tespit edilmiştir. Sonra farklı giriş değerlerini kapsayan bir set için EKFYʼnin çıkış değerleri ve düz çıkış profili sağlamak için olması gereken filtre katsayıları hesaplanmıştır. Bu veriler kullanılarak bir yapay sinir ağı oluşturulmuş ve eğitilmiştir. Test verileri kullanılarak yapılan denemelerde girişteki değişkenliğin 0,4 değerine kadar çıkışın değişkenliğinin 0,005 in altında kaldığı gözlenmiştir. Sonuç olarak iki aşamalı ayarlanabilir filtreli EKFY yapısında dinamik kazanç kontrolü yapay sinir ağı tabanlı sistem tarafından sağlanmıştır

SEPARATION SCIENCE AND TECHNOLOGY

In this study poly(N-vinylimidazole-acrylamide) p(N-VI-AAm) hydrogels were prepared as an adsorbent for adsorptive removal of lead (II) and copper (II) ions from aqueous solution. Adsorption studies showed that poly(N-vinylimidazole-acrylamide) p(N-VI-AAm) hydrogels can be effectively used to remove heavy metals. Hydrogel characterization was done by FTIR and SEM. The effect of the removal conditions such as contact time, pH, temperature, and initial metal ion concentration on the Pb (II) and Cu (II) ions binding was also tested. Maximum adsorption was achieved at 30 degrees C and 35 degrees C for Pb (II) and Cu (II) after 24 h, respectively. Experimental capacities were calculated as 262 and 53 mg g(-1) for lead and copper, respectively. The isotherms were analyzed with Langmuir and Freundlich models. Briefly, this economic and high adsorption performance poly(N-VI-AAm) hydrogel is a promising candidate for sewage disposal and metal pollution treatment

都市間旅客交通のためのマルチモーダル計画モデル

要約のみTohoku University奥村誠課