×
The submission system is temporarily under maintenance. Please send your manuscripts to
Go to Editorial ManagerBiodegradable polymers are very useful polymers in biomedical applications. In this research, several hydrogels were fabricated by using two polymers, Polyvinyl alcohol (PVA) and Chitosan (Chs) by the solvent casting method in order to use them for skin applications. Several tests were carried out on these membranes such as Agar diffusion method to examine their antimicrobial activities, Fourier transform infrared microscopy (FTIR) test to study the differences in their chemical structures. Uniaxial tensile test was performed to examine the mechanical characteristics of these membranes. In addition, the wettability test was used to investigate the hydrophobicity or hydrophilicity of the surfaces. The results showed that all membranes are hydrophilic, of which the contact angles are less than 90°. The membrane manufactured from 75:25 Chs-PVA is more hydrophobic (contact angle is 74°) than other membranes made of 50:50 Chs-PVA and 25:75 Chs-PVA as the contact angles were 59° and 61°, respectively. The tensile test results indicate that the membrane fabricated of the PVA and the membrane that was fabricated by 75% Chs and 25% PVA has the highest tensile strength of 17.9 MPa, 16.2 MPa and Young^’ s Modulus of 181.2 MPa and 7.18 MPa, respectively. The highest strain at break was observed by the membrane of 25:75 Chs-PVA which equals to 24.67%. Chitosan membranes showed inhibition zones of about 2.99 cm and 2.75 cm in length, and 75:25 Chs-PVA membranes showed 5.1 and 5.91 cm in length for E.coli. To sum up, this copolymer is considered as promising hydrogel for skin applications such as wound dressing.
A theoretical and experimental investigation pertaining to the buckling behavior of slender fiber reinforced polymer columns subjected to axial loading under varying temperatures (from room temperature to 50?). Two groups of composite materials were used for manufacturing of test specimens, the first consist of perlon fiber as a reinforcement and acrylic resin as a bonding matrix, while the second consists of a combination of perlon and carbon fibers as reinforcement. The composite specimens were fabricated by vacuum molding technique and cut according to ASTM D-638 for conducting tensile test. The data from tensile test were used to calculate the effective slenderness ratio and defining the column as Euler buckling column. An experimental rig was designed, manufactured and calibrated to study the effect of thermal and buckling load subjected to columns.Numerical analyses pertaining the buckling behavior for both groups were conducted. The results show that the temperature has a considerable effect on properties of fiberreinforced polymer composites where the value ofcritical load and Young's Modules decrease withthe increase of temperature for both groups.Perlon & Carbon reinforcement composites gavebest mechanical properties, which make them thebest candidate to improve the buckling resistancecharacteristics of composite materials.
Friction stir welding (FSW), a solid-state welding process, it’s involve a welding by friction between two metals or alloys, and also using for the joining of dissimilar materials due to the lower processing temperature over conventional fusion welding, it's include only one pass of welding. Friction Stir Processing (FSP) is a recent outgrowth of the Friction Stir Welding (FSW) process and relies on solid-state deformation to modify the structure of the workpiece, it's involve two pass or more of welding and applied either on the base metal(BM) or to join the two alloys/metals. In this paper the new method used, namely reverse rotation friction stir processing (RFSP), this research aims to study the effect of (RFSP) technique on the mechanical properties of welded alloys. (FSW) includes a single pass of the welding line but the second method (RFSP) involves two pass of welding (forth and back) but the 1st pass with a rotation speed in clockwise and the 2nd pass in counter-clockwise. The alloys used of dissimilar AA 2024 and AA6061 aluminum alloys of (3mm) thickness, the parameters used in this research include different rotational speed (1600, 1800, 2000 and 2200) RPM and one feed speed (25) mm/min. In the tensile test the results of reverse rotation friction stir processing (RFSP) was higher than friction stir welding (FSW) for all rotation speeds of welding except (1800 RPM). In the microhardness measurement the values of hardness for all samples at the nugget zone is higher than the basemetal of 6061-T6 and lower than the basemetal of 2024-T3. The efficiency of ultimate tensile strength reaches to about (72 %) for (RFSP) as compare with value of (FSW) and it’s about (44%) at rotation speed (1600 RPM).The only exception of welding was when the rotational speed of (1800 RPM), where the (FSW) is better than (RFSP), efficiency was approximately (77%) for the (FSW) compared with the results of (71%) (RFSP).
The effects of the repeated solution heat treatment on hardness, tensile strength and microstructure of aluminum were investigated. For this purpose, an alloy of AA6061-T6 was undergo to cyclic solution heat treatment process which is composed of repeated period (10 min) held at 520 °C for 1, 4, 8 and 12 cycles. The hardness was tested for five aging times (as quenching, one week, three weeks, one month and five months) to all cycles (1, 4, 8 and 12) firstly and it is found that the hardness of five months as aging time for all cycles has the best results (90Hv) as compared with others (as quenching, one week, three weeks, and one month), so it was adopted for all cycles to implement the tensile test and the microstructure. Hardness results were improved to Vickers hardness of (90Hv) with increasing of cycles up to 8 cycles then decreasing after that to (45Hv). Tensile results were showed an increment (34%) also for the same group of 8 cycles compared with (17%) and (9%) for 4 and 12 cycles, respectively. Microstructure is revealed that whenever cycles are increased, the precipitate phase in alloy is increased also, thus, it is improved the hardness and tensile strength.
The effects of the ultrasonic peening treatment (UPT) on the rotating bending fatigue behavior and the behavior of the vibrations of alloy steel DIN 41Cr4 were studied. Hardness test, Tensile test, Constant amplitude fatigue tests, and the vibrations measurements have been carried out on the specimens. Also, the fracture surface was examined and analyzed by a Scanning Electron Microscope (SEM). The results of the investigations, e.g. stress to number of cycles to failure (S-N) curves, fatigue strength improvement factor was 7%. The decreasing percentage of maximum Fast Fourier Transform (FFT) acceleration of the ultrasonic peened condition compared to the untreated conditions was 45%.
Orthoses and prostheses were Chosen and laminated based on their high Yield, ultimate stresses, bending stresses, and fatigue limit. Response Surface Methodology (RSM) was utilized to find the best values for two parameters reinforcement perlon fiber and percent of Titanium Nanoparticle coupled with the matrix resin during optimization. The response surface methodology combined the expertise of mathematicians and statisticians to construct and analyze experimental models. Using this method, we identified 13 different lamination samples comprising a wide range of perlon number and Ti nano Wt% in their Perlon layer composition. All lamination materials defined by RSM methods and produced by a vacuum system were subjected to a battery of tests, with fatigue tests performed on the ideal laminating material in contrast to laminations created in the first study (Tensile test, Bending test, and Fatigue tests according to the ASTM D638 and D790 respectively). In comparison to the other 12 laminations tested using Design Expert version 10.0.2, the lamination with ten perlon layers and 0.75 percent Ti nano proved to be the strongest overall in terms of Yield, ultimate, and bending loads. This study used composite materials and titanium nanoparticles to characterize and fabricate ankle foot orthoses. Strength in bending should amount to about 70 MPa, around 85 MPa in tensile tension. Two empirical quadratic equations for the models of peak bending strength and maximum tensile stress with 95% confidence were created using the response surface approach and analysis of variance within the design of experiments software.
Friction Stir Welding is one of the most practical welding process at the solid state. Friction Stir Processing is used to enhance the microstructure of FSW welded zone. The present study investigates the effect of welding parameters on the tensile properties of FSW and FSP joining 3 mm AA 5083 - H111 aluminum alloy by means of stress – strain curve with a uniaxial tensile test and by comparing the efficiency between FSW , FSP and base metal .The experiments were conducted with 1000,1500 and 2000 rpm rotation speeds ,and 20,40 and 60 mm/min travel speed. The best result of the welding joint was shown at the 20 mm/min feed speed and 1500 rpm rotational speed for FSW, and 40 mm/min feed speed and 1500 rpm rotation speed for FSP. The efficiency of ultimate tensile strength reaches to 92% for FSW and 94% for FSP.
In this work, constant and increasing temperature fatigue interaction effect on fatigue behavior of 2017-T4 aluminum alloy was investigated. Fatigue tests at constant load constant temperature and constant load increasing temperature were performed for five applied stresses which are (350,275,200,175 and 150 MPa) that based on the tensile test behavior .The constant temperatures were room temperature (RT) (25 ?C) and 100 ?C. While the increasing temperatures were RT, 50 ?C, 100 ?C and 150 ?C for one test program. The constant fatigue property of the increasing temperatures was observed the worst case compared to the others constant fatigue properties. A new variable temperature fatigue damage model was proposed. It is based on the S-N curve and taking into account the effects of constant loads and variable temperature. A comparison between prediction of the proposed model and crack growth rate due to Miner rule was made. The results proved that this model is satisfactory and gave safe results than Miner rule compared to experimental data.