Journal des sciences et de l'ingénierie des matériaux

This study describes a methodology to design a custom-made cranial prosthesis for a patient who suffered injuries from road traffic accident. Computer based cranial defect reconstruction techniques is developed. The design approach was based on the 3D reconstruction of the skull of the patient, obtained by a CT scan. Then a reverse engineering (RE) method is used to reconstruct the defect prosthesis computer-aided design (CAD) model. Once the prosthesis CAD design was completed, the 3D models the skull and the prosthesis were transported into Rapid Prototyping (RP) machine to fabricate the physical model. Finally, the RP model is directly used to produce the biomaterial calcium phosphate cement (CPC) prosthesis. The prosthesis was successfully implanted and a satisfactory result was obtained by using this design method.

The aim of the present study is to investigate the effect of High frequency (HF) Electric resistance welding process parameters and post heat treatment on the torsional fatigue life of micro alloyed HSLA steel tubes. Micro alloyed grades exhibit higher strength and formability owing to the presence of fine recrystallized ferritic grains due to thermo mechanical treatment and presence of alloying elements like Vanadium, Niobium and Titanium. Welded tubular components made of micro alloyed HSLA steel grades are highly emerging and manufacturing them remains quite challenging. Weld bond width, HAZ width and bond angle are the significant factors that directly influences the Weld quality and strength. The effect of key welding parameters like Heat input, welding temperature, squeeze roll pressure, Vee-angle, Vee-length and Impeder diameter on the above mentioned significant factors was analysed. Narrow bond, Minimum HAZ width with pronounced Hour glass pattern and optimum bond angle resulted in superior bond strength and formability of HSLA tubes. Microstructural characterization of the samples was carried out using Light optical microscopy and Scanning electron microscopy. Residual stress was determined using X-ray diffract meter and tube slitting method. Higher tensile residual stress of magnitude 200 MPa was observed in the weld region. Since such high magnitude of tensile residual stress is detrimental to torsional fatigue life, stress relieving of the tubes was carried out at different subcritical temperatures 650°C and 700°C with soaking time of 45 minutes. Without significant drop in the tensile properties, compressive residual stress of magnitude 129 MPa was observed at a particular stress relieving cycle. As an effect of stress relieving heat treatment below Ac1 temperature, there is a significant improvement in the Torsional fatigue life of the HSLA steel. Thus, High Frequency welded micro alloyed HSLA steel tubes with enhanced torsional fatigue performance were successfully developed.

DNA aggregates were electro less deposited onto carbon paste electrode, firstly and electrode surface was coated by polymer film to protect the DNA film. Prepared electrode has shown great activity towards the oxidation of methanol, and no effect of empoisoning is observed. The effect of various parameters such as scan rate and methanol concentration, on the electro catalytical oxidation of methanol has also been investigated. The morphological study of electrode surface was investigated by Atomic Force Microscopy (AFM) and optical microscopy.

To study the Mn doping effect on the specific capacitance of PANI, concentration of Mn was varied from 0.3 to 1.5 weight percent. Surface morphology was examined by using Scanning Electron Microscopy (SEM) which showed nanofiber aggregate structure of pure PANI and porous and well distributed nanofibers for the doped PANI. The DC electrical resistivity (ρ) of pure PANI and Mn doped PANI films were measured which shows semiconducting behavior of pure PANI and Mn doped samples.

Fresh water is vital to human life and economic well-being, and societies extract vast quantities of water from rivers, lakes, wetlands, and underground aquifers but most of these freshwater sources are polluted by different chemicals discharged from industries. Our need for fresh water has long caused us to overlook equally vital benefits of water that remains in streams to sustain healthy freshwater habitats. Heavy metals are discharged from different industries into freshwaters and are easily absorbed by fish and other aquatic organisms. Small concentrations can be toxic because heavy metals undergo bio concentration. Chromium is an essential element that is required in small amounts for carbohydrate metabolism, but becomes toxic at higher concentrations. The most bioavailable and therefore most toxic form of chromium is the hexavalent Cr (VI) ion. It is well recognized as an element of environmental and public health concern. The objective of this study was to examine the potential of coffee husk in removing chromium from polluted water. In this study, the adsorption potential of activated carbon for the removal of Cr (VI) ions from industrial wastewater has been investigated. The adsorption of hexavalent chromium from aqueous solution by coffee husk activated carbon prepared by chemical method and its application to real wastewater was studied. The extent of adsorption was studied as a function of pH, contact time, adsorbent dose, and initial adsorbed concentration. Optimum results were found to be 60 min, 80 mg/l, 2 g/l, 3 g/l and 200 rpm for time contact, initial concentration, pH, adsorbent dose and stirring speed respectively at the optimal condition the adsorption of hexavalent chromium was found to be 98.19%.

Vanadis tool steels which are a trademark of the Uddeholm AB Company are high vanadium content (along with chromium and molybdenum) steels with unique mechanical properties such as very high wear resistance along with a good machinability, dimensional stability and grind ability. They are widely used in blanking operations, stamping, and deep drawing, cutting and slitting blades. Microstructural features of Vanadis steels are directly depended upon the distribution of the carbide grains. Based upon the carbon and vanadium contents of the Vanadis tool steels, wear test results and micro hardness values are correlated with the resulting microstructural features

The objective of this paper is to provide an overview of the main welding defects that frequently exist in piping and equipment and how to detect these defects without destroying the welds using Non Destructive Testing (NDT) methods. Then, the sensitization of stainless steel weld, characterization, processing and structure properties of HAZ as well as weld metal will be discussed in details. Furthermore, this paper will illustrate the treatment of the weld decay by recovery of passivation film after welding which will be followed by prevention of intergranular corrosion or weld decay of SS using surface mechanical attrition treatment and all of these will be described with help of characterization techniques XRD, SEM, TEM and EPMA.

The improvement of the mechanical properties such as tensile strength, hardness, and ductility were studied by a new and developed technique in the additions field (ZnO nanorods additions) under as-cast condition. Different melting temperatures, holding times, and ZnO nanorods amount were used and the refining of the microstructures and comparison of the obtained results with heat treatment conditions were also investigated in this paper. The results showed that the network of eutectic silicon particles is agglomerated, refined, and less angular after adding of ZnO nanorods to A356 aluminum casting alloys with quick solidification by water. Good enhancement in ultimate tensile strength and elongation with slightly increasing in the hardness were observed and they reached 222 MPa, 35%, and 78 HB respectively. Moreover, ZnO nanorods additions to A356 aluminum casting alloys give the possibility to improve the ultimate tensile strength, elongation, and hardness without heat treatment. Furthermore, the optimal melting and holding temperature for the present work is 700°C with holding time of 3 hours.

A crystalline Nano powders of 3 mol% yttria-partially stabilized (3Y-PSZ) has been synthesized using ZrOCl2 and Y (NO3)3 as raw materials by microwave pyrolysis with a TE666 resonant mode at 700-900°C. The frequency of the microwave was 2.45 GHz with the maximum power of 10 KW, and a hybrid heating structure was used with insulation of porous mullite and SiC aided heaters. For comparison, conventional heating was performed in air at 750°C for 20 min. The as-synthesized products were characterized by SEM and TEM images, XRD patterns. It was found that microwave energy promotes the conversion of tetragonal ZrO2 (t-ZrO2) to monoclinic ZrO2 (m-ZrO2) phase compared with conventional pyrolysis. TEM images showed that highly dispersed 3Y-ZrO2 powders with ~23 nm in size were obtained by microwave pyrolysis at 750°C for 20 min.

The main objective of this research is to determine corrosion rate and weight loss for the coated and non-coated with several layer of mild steel AISI 1020. This research discussed and focusing on prefabricated material coating and non- coating of light steel structure effect on seawater and study on the research have been done before by others researcher for better understanding on this research. Basically, most of the researches conducted before are only focusing on the type of prefabricated materials. However, in this research the coating will be used in other to improve the properties of materials.

The vibrational heat capacity Cvib of a re-optimized neutral gold cluster was investigated at temperatures 0.5-300 K. The vibrational frequency of an optimized cluster was revealed by small atomic displacements using a numerical finite-differentiation method. This method was implemented using density-functional tight-binding (DFTB) approach. The desired set of system Eigen frequencies (3N -6) was obtained by diagonalization of the symmetric positive semi definite Hessian matrix. Our investigation revealed that the Cvib curve is strongly influenced by temperature, size, and structure and bond-order dependency. The effect of the range of interatomic forces is studied; especially the lower frequencies make a significant contribution to the heat capacity at low temperatures. In addition to that, we have exactly predicted the vibrational frequencies (ωi) which occur between 0.55 to 370.72 cm-1, depending on the nanoparticle morphology at T=0 for small neutral gold clusters AuN=3-20. This result has been proved and confirmed by the size effect values. It was found that beside the particle size, geometric shape, defect structure and an increase in asymmetry of nanoparticles effects on heat capacity. Surprisingly, the Boson peaks are typically ascribed to an excess density of vibrational states for the small clusters. Finally, temperature dependencies of the vibrational heat capacities of the re-optimized neutral gold clusters have been studied for the first time.

Highly strained 3C-SiC/Si (001) epilayers of different thicknesses (0.1 μm-12.4 μm) prepared in a vertical reactor configuration by chemical vapor deposition (V-CVD) method were examined using Raman scattering spectroscopy (RSS). In the near backscattering geometry, our RSS results for “as-grown” epilayers revealed TO- and LO-phonon bands shifting towards lower frequencies by approximately ~2 cm-1 with respect to the “free-standing” films. Raman scattering data of optical phonons are carefully analyzed by using an elastic deformation theory with inputs of hydrostatic-stress coefficients from a realistic lattice dynamical approach that helped assess biaxial stress, inplane tensile- and normal compressive-strain, respectively. In each sample, the estimated value of strain is found at least two order of magnitude smaller than the one expected from lattice mismatch between the epilayer and substrate. This result has provided a strong corroboration to our recent average-t-matrix Green’s function theory of impurity vibrational modes – indicating that the high density of intrinsic defects at the 3C-SiC/Si interface are possily responsible for releasing the misfit stresses and strains. Unlike others, our RSS study in “as-grown” 3C-SiC/Si (001) has reiterated the fact that for ultrathin epilayers (d<0.4 μm) the optical modes of 3C-SiC are markedly indistinctive. The mechanism responsible for this behavior is identified and discussed. PACS: 78.20.-e 63.20.Pw 63.20.D.

Among the very few efforts for the preparation of stable pillared graphene nanostructures, there is no report of tin porphyrin intercalated between TiO2-graphene (TG) nanosheets. In this study, a nanostructure material of pillared graphene made of tin porphyrin functionalized graphene-TiO2 composite (TG) was successfully synthesized. The prepared compound showed high activity in the photodegradation reaction under irradiation of visible light. Photocatalytic results showed that the composite of graphene-TiO2 containing 3% graphene had the highest photoactivity. The photoactivity of TG (3%) was about 1.5 times higher than that of the pure TiO2. Besides, tin porphyrin-pillared TG composite (TGSP) material exhibited an excellent visible light photocatalytic performance in degradation of methyl orange dye. This compound could destruct 100% of methyl orange dye in 180 min. Such pillared carbon nanostructure exhibited unique photoactivity due to the synergistic effect between the graphene sheets and the SnTCPP pillars. It is found that the highly efficient light-harvesting structure of the SnTCPP pillared TG composite can be attributed to densely embedded porphyrin chromophores with high visible absorptivity within the framework. The investigation of photocatalytic mechanism determined that hydroxyl radical is a main species in photodegradation process of methyl orange over TGSP compound.

Within this work GROMACS computational molecular dynamics simulations were performed to determine the free energy of solvation of an n-decane molecule. The pull-code was utilized to draw the molecule across z-space to span from an initial gas state to a final solubilized state. The free energy was computed at each location of the molecule and this quantity is presented as a function of space for multiple alcohol contents. A single simulation of n-dodecane is considered for comparison in 100% water.

The basis of the quantitative conical/pyramidal (nano) indentation, without fittings, iterations, or simulations, is the physically founded FN=k h3/2 relation. The constant k (penetration resistance, mN/μm3/2) from linear plot with excellent regression discards initial surface effects, identifies important phase transformation onsets, conversion and activation energies, and reveals errors. The failing Sneddon theory of ISO with unphysical exponent 2 on h lacks these possibilities, disregards shear-force work, and violates the first energy law since 50 years. The denied but strictly quantified loss of energy (20% for physical h3/2; 33.33% at believed h2) violates the first energy law and disregards the force remaining for penetration. Straightforward correction is performed for the dimensions, by replacing unphysical exponent 2. The correction factors hmax 1/2 and 0.8 are applied via joint maximal force to the universal, FE-simulated, (approximately) ISO hardness, and ISO modulus that unduly rely on h2, to give the physically founded values with their correct dimensions. Previous corrected k-values obtain Hphys directly from the loading curve regression. Previous incomplete corrections are rectified. The new dimensions and daily risk liabilities from ISO versus physics dilemma are discussed, considering the influence on all mechanical parameters from hardness and modulus, regarding technique, biology, medicine, daily life.

Medium carbon low alloy forged steels (EN 18, EN19, EN 24, and EN25) have been investigated with respect to their mechanical properties after heat treatment. For heat treatment solutionizing temperature of 855°C with a soaking period of 60 min was used. Thereafter quenching was carried out in three media, viz., Step water, oil and polymer (polyethylene glycol) separately. The quenched samples were step tempered at 575°C and at 220°C sequentially for 60 min each. Hardness, tensile strength, Charpy impact strength and metallographic were carried out on the untreated and heat treated specimens. The heat treated specimens showed higher hardness (10-30%), higher strength (20-100%) and higher impact energy (20-160%). The specimens quenched in poly ethylene glycol exhibited the best mechanical properties. The heat treated specimens had a structure of fine tempered martensite with small amount of bainite.

The current study aims to find the optimum cutting parameters in turning process without using cutting fluids (dry cutting condition) towards sustainable manufacturing. Where the power consumption and environmental pollution increase due to increase of the machining operations in manufacturing field, so to save energy and environment and reduce cost it is important to adopt sustainability in machining processes. The experimental work in this study involves the preparation to a number of experiments on AISI 1045 carbon steel to collect the necessary data for implementing optimization process. The experiments were conducted by changing levels of cutting parameters (spindle speed, feed rate and cutting depth) in CNC turning machine. Surface roughness of the workpiece has been depended as a quality indicator. In addition, the temperature of cutting tool has been recorded during machining the work pieces in order to control the temperature of cutting process. Theoretically, empirical equations for temperature of cutting tool and surface roughness of the work piece have been discovered. By using Genetic Algorithm technique these equations have been used to find the optimum of cutting parameters spindle speed, feed rate and depth of cut. The optimum values that obtained by using Genetic Algorithm which achieve sustainable cutting were spindle speed 588.96 rpm, depth of cut 0.50 mm and feed rate 64.55 mm/min in order to have the optimum of surface roughness in low cutting temperature.

Composite steel-concrete beams are used widely in bridges and buildings construction as the main structural elements in flexure. These structures have a design life and this may be reduced if loads are increased or environmental degradation could happen. These changes may reduce the design life and strength of such members and thus replacement or retrofitting may need to be considered. The present study focuses on evaluating the effect of partial shear connection on strengthen composite beams with externally post-tension tendons. Using three dimensional F.E. modeling it’s able to simulate the overall flexural behavior of composite beams which are strengthen with many shapes of tendons profiles. A fundamental point for the structural behavior and design of composite beams is the level of connection and interaction between the steel section and the concrete slab. The use of partial connection provides the opportunity to achieve a better match of applied and resisting moment and some economy in the provision of connectors, taking into account the demonstrated advantages of externally post tension system like: Increase in ultimate moment capacity of structure, Enlarge the range of elastic behavior before yielding for the structure with the introduction of internal stresses.