Abstract
The aim of the work was to evaluate the effect of ultraviolet-ozone (UV-O3) irradiation with different times on the structure and thermal properties of hydroxypropyl methylcellulose (HPMC) in the form of a thin film to be used as bioequivalent materials according to their important broad practical and medical applications. HPMC thin films were exposed to UV-O3 radiation in air at a wavelength of 184.9 nm.The beneficial effects of this treatment on the crystallinity and amorphousity regions were followed by X-ray diffraction technique and FTIR spectroscopy. Differential scanning calorimetry, thermogravimetric and differntial thermal analyses were used in order to study the thermal properties of HPMC samples following the process of photodegradation. The obtained results indicated that the rate of degradation process was increased with increasing the exposure time. Variations in shape and area of the thermal peaks were observed which may be attributed to the different degrees of crystallinity after exposing the treated HPMC samples. This meant a change in the amorphousity of the treated samples, the oxidation of its chemical linkages on its surface and its bulk, and the formation of free radical species as well as bond formation.
Key Words
HPMC; photodegradation; x-ray diffraction; FTIR spectroscopy; thermal properties
Address
Nabawia A. Abdel-Zaher: Textile Metrology Lab, National Institute for Standards, Giza, Egypt
Manal T.H. Moselhey: Al-Safwa High Institute of Engineering, Cairo, Egypt
Osiris W. Guirguis: Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt
Abstract
In this work we introduce a higher-order hyperbolic shear deformation model for bending and frees vibration analysis of functionally graded beams. In this theory and by making a further supposition, the axial displacement accounts for a refined hyperbolic distribution, and the transverse shear stress satisfies the traction-free boundary conditions on the beam boundary surfaces, so no need of any shear correction factors (SCFs). The material properties are continuously varied through the beam thickness by the power-law distribution of the volume fraction of the constituents. Based on the present refined hyperbolic shear deformation beam model, the governing equations of motion are obtained from the Hamilton\'s principle. Analytical solutions for simply-supported beams are developed to solve the problem. To verify the precision and validity of the present theory some numerical results are compared with the existing ones in the literature and a good agreement is showed.
Key Words
deflection; dynamic analysis; functionally graded material; hyperbolic shear deformation theory; refined theory
Address
Ismail Bensaid, Abdelmadjid Cheikh and Ahmed Mangouchi: Department of Mechanical Engineering, IS2M Laboratory, Faculty of Technology, University of Tlemcen, Tlemcen, Algeria
Bachir Kerboua: EOLE Laboratory, Faculty of Technology, University of Tlemcen, Tlemcen, Algeria
Abstract
The transient thermo-mechanical behavior of a simply-supported beam made of a functionally graded material (FGM) under the effect of a moving heat source is investigated. The FGM consists of a ceramic part (on the top), which is the hot side of the beam as the heat source motion takes place along this side, and a metal part (in the bottom), which is considered the cold side. Grading is in the transverse direction, with the properties being temperature-dependent. The main steps of the thermo-elastic modeling included deriving the partial differential equations for the temperatures and deflections in time and space, transforming them into ordinary differential equations using Laplace transformation, and finally using the inverse Laplace transformation to find the solutions. The effects of different parameters on the thermo-mechanical behavior of the beam are investigated, such as the convection coefficient and the heat source intensity and speed. The results show that temperatures, and hence the deflections and stresses increase with less heat convection from the beam surface, higher heat source intensity and low speeds.
Key Words
transient; thermo-mechanical; FGM; beam; moving heat source
Address
Naser S. Al-Huniti and Sami T. Alahmad: Department of Mechanical Engineering, The University of Jordan, 11942, Amman, Jordan
Abstract
In this article, static deflection and buckling of functionally graded (FG) nanoscale beams made of porous material are carried out based on the nonlocal Timoshenko beam model which captures the small scale influences. The exact position of neutral axis is fixed, to eliminate the stretching and bending coupling due to the unsymmetrical material change along the FG nanobeams thickness. The material properties of FG beam are graded through the thickness on the basis of the power-law form, which is modified to approximate the material properties with two models of porosity phases. By employing Hamilton\'s principle, the nonlocal governing equations of FG nanobeams are obtained and solved analytically for simply-supported boundary conditions via the Navier-type procedure. Numerical results for deflection and buckling of FG nanoscale beams are presented and validated with those existing in the literature. The influences of small scale parameter, power law index, porosity distribution and slenderness ratio on the static and stability responses of the FG nanobeams are all explored.
Key Words
nonlocal elasticity theory; bending; buckling; FG nanobeam; porosities
Address
Ismail Bensaid: IS2M Laboratory, Faculty of Technology, Mechanical engineering Department, University of Tlemcen, Tlemcen, Algeria
Ahmed Guenanou: Faculty of Technology, Mechanical engineering Department, University of Tlemcen, Tlemcen, Algeria
Abstract
A hat section was designed and developed for maximum impact energy absorption and/ or transmission under low velocity impact. Towards this, different hat sections, having material properties of thermoplastic, were modeled and investigated numerically using finite element analysis (FEA) in the range of 20-50 J impact energy. In the study it was experienced that the design configuration of hat section with curvilinear profile (HSCP) was excellent in energy attenuation capacity and for even distribution of maximum impact force around and along the hat section under low velocity impact loading. To validate the numerical findings, polypropylene copolymer (Co-PP) HSCP and low density polyethylene (LDPE) HSCP were developed and evaluated experimentally in the said impact energy range. A correlation was established between FEA and experimental test results, thereby, validating a numerical model to predict results for other thermoplastic materials under given range of impact energy. The LDPE HSCP exhibited better performance as compared to Co-PP HSCP in the said range of impact energy. The findings of this study will enable the engineers and technologists to design and develop low velocity impact resistance devices for various applications including devices to protect bone joints.
Key Words
hat section, curvilinear profile, low velocity impact, attenuation, numerical, experimental
Address
Kumresh K Gaur and Naresh Bhatnagar:Department of Mechanical Engineering, Indian Institute of Technology Delhi, Hauz Khas, 110016, New Delhi, India
Mayank Dwivedi: Defence Research and Development Organization (DRDO), DRDO Bhawan, Rajaji Marg, 110011, New Delhi, India
Abstract
In the present work, a design of experiment (DOE) technique using Taguchi method, has been applied to optimize the properties of ODS tungsten heavy alloys(WHAs). In this work Taguchi method involves nine experiments groups for four processing parameters (compaction pressure, sintering temperature, binding material type, and oxide type) with three levels was implemented. The signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed to obtain the optimal process parameter levels and to analyze the effect of these parameters on density, electrical conductivity, hardness and compressive strength values. The results showed that all the chosen factors have significant effects on all properties of ODS tungsten heavy alloys samples. The density, electrical conductivity and hardness increases with the increase in sintering temperature. The analysis of the verification experiments for the physical properties (density and Electrical conductivity) has shown that Taguchi parameter design can successfully verify the optimal parameters, where the difference between the predicted and the verified values of relative density and electrical conductivity is about 1.01% and 1.15% respectively.
Key Words
oxide dispersion strengthened; tungsten heavy alloys; Taguchi method; S/N ratio; ANOVA; density; electrical conductivity
Address
Mohamed A. Sayed and Osama M. Dawood: Department of Mechanical Engineering, Faculty of Engineering, Helwan University, 1Sherif St., Helwan, Cairo, Egypt
Ayman H. Elsayed: Department of Powder Technology, Central Metallurgical R&D Institute (CMRDI), B.O 87Helwan, Egypt
Walid R. Daoush:
1) Department of Production Technology, Faculty of Industrial Education, Helwan University, 30 El Sawah Street, Cairo, Egypt
2) Department of Chemistry, Faculty of Science, Al-Imam Muhammad Ibn Saud Islamic University, Al Riyadh, KSA
