Application of higher-order theories on the propagation of bulk waves in bio-composite plates lying on Kerr substrate.

Because of the critical usage of biomedical applications, their constitutive materials must possess specific properties to satisfy the environmental conditions. Consequently, the selection of the best materials is one of the most important subjects in the manufacturing industry. Bio-composites are outstanding alternatives to customary biomaterials in biomedical applications owing to their supreme material properties. On the other hand, mechanical analyses including static and dynamic analyses of bio-systems should be carried out to optimize the designed biomedical applications like medical implants. Thus, wave dispersion analysis of functionally graded (FG) bio-composite plate could serve for design goals of biomedical structures. In this investigation, the influence of various higher-order shear deformation theories of the plate on the dispersion of bulk waves in FG bio-composite plate lying on Kerr foundation has been explored for the first time. The constituent materials of FG structure are gold alloy as metal phase and hydroxyapatite as ceramic phase. In order to compute the effective properties of the studied structure, the upper Hashin-Shtrikman homogenization scheme has been implemented. Higher-order theories and Hamilton's principle have been applied to derive the governing equations and the obtained equations are analytically solved via a harmonic function. Eventually, the sensitivity of various important parameters has been surveyed and discussed comprehensively. The obtained outcomes have been indicated in detail.

Application of Hashin-Shtrikman bounds homogenization model for frequency analysis of imperfect FG bio-composite plates.

Despite abundant theoretical investigations on the dynamic behavior of functionally graded (FG) structures, the study on frequency analysis of FG bio-composite structures is limited. FG bio-composite materials due to their biocompatibility potentials and good material properties can be applied in biomedical applications, especially dental implants. In this investigation, a natural frequency response of the FG bio-composite plate is analyzed within the framework of the newly developed refined higher-order shear deformation plate theory. Additionally, the imperfection impact on frequency behavior is evaluated while three imperfection distribution patterns are taken into account. The constitutive materials of FG bio-composite plate are Hydroxyapatite and Titanium. The effective material properties of the structure are determined with the help of the upper Hashin-Shtrikman bounds homogenization model. In continuation, to solve the derived governing equations of imperfect FG bio-composite plate, Galerkin's analytical method is employed. Also, the precision of the used theory is validated, the obtained outcomes are compared and an acceptable matching is found. Later, the sensitivity of different considerable variables is comprehensively assessed and discussed.

Entropy generation optimization for the electroosmotic MHD fluid flow over the curved stenosis artery in the presence of thrombosis.

The present study deals with the entropy generation analysis on the flow of an electrically conductive fluid (Blood) with [Formula: see text]-suspended nanoparticles through the irregular stenosed artery with thrombosis on the catheter. The fluid flow can be actuated by the interactions of different physical phenomena like electroosmosis, radiation, Joule heating and a uniform radial magnetic field. The analysis of different shapes and sizes of the nanoparticle is considered by taking the Crocine model. The velocity, temperature, and concentration distributions are computed using the Crank-Nicholson method within the framework of the Debye-Huckel linearization approximation. In order to see how blood flow changes in response to different parameters, the velocity contour is calculated. The aluminium oxide nanoparticles employed in this research have several potential uses in biomedicine and biosensing. The surface's stability, biocompatibility, and reactivity may be enhanced by surface engineering, making the material effective for deoxyribonucleic acid sensing. It may be deduced that the velocity profile reduces as the nanoparticle's size grows while depicts the reverse trend for the shape size. In a region close to the walls, the entropy profile decreases, while in the region in the middle, it rises as the magnetic field parameter rises. The present endeavour can be beneficial in biomedical sciences in designing better biomedical devices and gaining insight into the hemodynamic flow for treatment modalities.

Effect of Si Content on the Thermal Expansion of Ti15Mo(0-2 Si) Biomaterial Alloys during Different Heating Rates.

Thermal expansion measurements were used to characterize phase transformations in metastable ß-Ti alloys (Ti15MoxSi) without and with various Si additions (where x = 0, 0.5, 1.0, 1.5, and 2 in wt.%) during linear heating at two heating rates of 5 and 10 °C/min up to 850 °C. For this study, five alloys were developed and examined in terms of their presence phases, microstructures, and starting and final transformation temperatures. According to the results, all of the as-cast samples primarily include an equiaxed ß-Ti phase. The influence of phase transformation on the material dimensions was discussed and compared with the variations in Si contents. The transformation was investigated using a dilatometric technique for the developed alloys during continuous heating and cooling. The dilatometric curve of heating revealed two distinct reflection points as the heating temperature increased. The starting transformation temperature (Ts) to obtain the ω-phase was reported at 359 °C without Si addition; whereas the final transformation temperature (Tf) of the dissolution of α-phase was obtained at 572 °C at a heating rate of 10 °C/min. At 2 wt.% Si, the first derivative curves reported Ts and Tf transforming temperatures of 314-565 °C (at a 5 °C/min heating rate) and 270-540 °C (at a 10 °C/min heating rate), respectively. The Ts and Tf transforming temperatures were significantly decreased with Si additions, which decreased the ß-transus temperature. Moreover, the thermal expansion coefficient curves of the investigated alloys without and with 2 wt.% Si were studied. The transformation heating curves have an S-shaped pattern, according to the results.

Microstructure, Texture, and Mechanical Properties of Friction Stir Spot-Welded AA5052-H32: Influence of Tool Rotation Rate.

Friction stir spot welding (FSSW) of similar AA5052-H32 joints has numerous benefits in shipbuilding, aerospace, and automotive structural applications. In addition, studying the role of tool rotation speed on the microstructure features, achieved textures, and joint performance of the friction stir spot-welded (FSSWed) joint still needs more systematic research. Different FSSWed AA5052-H32 lap joints of 4 mm thickness were produced at different heat inputs using three tool rotation speeds of 1500, 1000, and 500 rpm at a constant dwell time of 2 s. The applied thermal heat inputs for achieving the FSSW processes were calculated. The produced joints were characterized by their appearance, macrostructures, microstructures, and mechanical properties (hardness contour maps and maximum tensile-shear load) at room temperature. The grain structure and texture developed for all the FSSWed joints were deeply investigated using an advanced electron backscattering diffraction (EBSD) technique and compared with the base material (BM). The main results showed that the average hardness value of the stir zone (SZ) in the welded joints is higher than that in the AA5052-H32 BM for all applied rotation speeds, and it decreases as the rotation speed increases from 500 to 1000 rpm. This SZ enhancement in hardness compared to the BM cold-rolled grain structure is caused by the high grain refining due to the dynamic recrystallization associated with the FSSW. The average grain size values of the stir zones are 11, 9, and 4 µm for the FSSWed joints processed at 1500, 1000, and 500 rpm, respectively, while the BM average grain size is 40 µm. The simple shear texture with B/-B components mainly dominates the texture. Compared to the welded joints, the joint processed at 500 rpm and a 2 s duration time attains the highest tensile-shear load value of 4330 N. This value decreases with increasing rotation speed to reach 2569 N at a rotation speed of 1500. After tensile testing of the FSSWed joints, the fracture surface was also examined and discussed.

Friction Stir-Spot Welding of AA5052-H32 Alloy Sheets: Effects of Dwell Time on Mechanical Properties and Microstructural Evolution.

Friction stir-spot welding (FSSW) as a solid-state joining process for local welding offers a number of benefits for applications in the automotive, aerospace, and marine industries. In these industries, and from an economic point of view, producing spot welds at a low rotating speed and in a short time is critical for saving energy and enhancing productivity. This investigation helped fill a knowledge gap in the literature about FSSW of 4 mm similar lap joints of AA5052-H32 sheet materials, in which welding takes place over a short time period with a slow tool rotation speed. Consequently, the purpose of this work was to investigate the feasibility of FSSW 2 mm thick AA5052-H32 aluminum alloy sheets to produce 4 mm thick similar spot lap joints at various low dwell times of 1, 2, and 3 s and a constant relatively low tool rotation speed of 500 rpm. The introduced heat input for the friction stir-spot welded (FSSWed) lap joints was calculated based on the applied processing parameters. Joint appearance, cross-section macrostructures, and microstructure features of all the spot welds were evaluated. The mechanical properties (hardness contour maps and maximum tensile shear loads) were also examined. The results show that joining 2 mm sheet thickness AA5052-H32 at a low heat input in defect-free similar lap joints could be successfully achieved. The stir zone (SZ) region became wider as the dwell time increased from 1 to 3 s. The hardness value of the SZ was higher than that attained by the AA5052-H32 base material (BM) for all applied dwell times. Especially at 2 s, the hardness of the SZ was approximately 48% higher than that of the BM. This increase in hardness may be attributed to the high grain refinement of the new dynamically recrystallized grain (4 µm) in the SZ compared to the cold-rolled BM grain size (40 µm). Among the tried FSSW process variables, the dwell time of 2 s at a rotation rate of 500 rpm also produced the maximum tensile shear load of 4330 N. Finally, the locations and features of the fracture surfaces of the FSSWed joints were examined using a scanning electron microscope (SEM) and the obtained results were discussed.

A Novel Friction Stir Deposition Technique to Refill Keyhole of Friction Stir Spot Welded AA6082-T6 Dissimilar Joints of Different Sheet Thicknesses.

Joining dissimilar sheet thicknesses of AA6082-T6 alloys by friction stir spot welding (FSSW) provides many advantages in automotive and aerospace applications. The formed keyhole at the end of the FSSW process is one of the typical features after the welding process, which owns the same size as the rotating pin that remains at the joint center. This keyhole destroys the joint continuity and can stimulate serious stress concentration when the FSSW joint bears an external force. To solve this issue, a novel refilling technique was developed for the FSSW keyholes using a friction stir deposition (FSD) technique. The FSSW joints of AA6082-T6 sheets were welded at various rotation speeds from 400 to 1000 rpm and a constant dwell time of 3 s, where a 2 mm sheet thickness was an upper sheet, and a 1 mm sheet thickness was a lower sheet. All the keyhole refilling processes were achieved using a specially designed AA2011-T6 consumable rod to be used for friction stir deposition of continuous layers at a constant deposition parameter of 400 rpm consumable rod rotation speed and a 1 mm/min feed rate. The heat input energy for both the FSSW and refilled FSSW lap joints was calculated. In addition, the FSSW and the FSD temperatures were measured. Macrostructure, microstructure, and mechanical properties in terms of hardness and tensile shear maximum load were evaluated for both the friction stir spot welded (FSSWed) and the refilled FSSW lap joints. The obtained results showed that the keyhole could be successfully refilled with defect-free continuous multilayers after the refill friction stir spot welding (RFSSW) process. All the RFSSW lap joints showed higher tensile shear loads than that given by the FSSW (before refill) lap joints. The RFSSW joint (welded at 600 rpm/3 s and refilled at 400 rpm/1 mm/min) showed a higher tensile shear load of 5400 N ± 100 compared with that recorded by the unrefilled joint (4300 N ± 80). The fracture location and fracture surface of the FSSW and RFSSW were examined and discussed.

Optimization of Bobbin Tool Friction Stir Processing Parameters of AA1050 Using Response Surface Methodology.

The current research designed a statistical model for the bobbin tool friction stir processing (BT-FSP) of AA1050 aluminum alloy using the Response Surface Method (RSM). The analysis studied the influence of tool travel speeds of 100, 200, and 300 mm/min and different pin geometries (triangle, square, and cylindrical) at a constant tool rotation speed (RS) of 600 rpm on processing 8 mm thickness AA1050. The developed mathematical model optimizes the effect of the applied BT-FSP parameters on machine torque, processing zone (PZ) temperature, surface roughness, hardness values, and ultimate tensile strength (UTS). The experimental design is based on the Face Central Composite Design (FCCD), using linear and quadratic polynomial equations to develop the mathematical models. The results show that the proposed model adequately predicts the responses within the processing parameters, and the pin geometry is the most influential parameter during the BT-FSP of AA1050. The analysis of variance exhibit that the developed mathematical models can effectively predict the values of the machine torque, PZ temperature, surface roughness, hardness, and UTS with a confidence level of over 95% for the AA1050 BT-FSP. The optimization process shows that the optimum parameters to attain the highest mechanical properties in terms of hardness and tensile strength at the lowest surface roughness and machine torque are travel speed (TS) of 200 mm/min using cylindrical (Cy) pin geometry at the constant RS of 600 rpm. The PZ temperature of the processed specimens decreased with increasing TS at different pin geometries. Meanwhile, the surface roughness of the processed passes and machine torque increased with increasing the TS at different pin geometries. Increasing TS from 100 to 300 mm/min increases the hardness values of the processed materials using different pin geometries. The highest UTS of 79 MPa for the processed specimens was attained at the TS of 200 mm/min and RS of 600 rpm using the Cy pin geometry.

The Influence of Tool Pin Geometry and Speed on the Mechanical Properties of the Bobbin Tool Friction Stir Processed AA1050.

AA1050 plates of 8 mm thickness were processed via bobbin-tool friction stir processing technique at a constant rotation speed of 600 rpm and different travel speeds ranging from 50 to 300 mm/min using three-pin geometries of triangle, square, and cylindrical. The temperatures of the processed zone, the advancing side, and the retreating side were measured; the machine torque during processing was also recorded. The processed materials were evaluated in terms of surface roughness, macrostructure, tensile properties, and hardness measurements. The fracture surfaces of the tensile fractured specimens were investigated using SEM. The results indicated that the pin geometry and processing speed significantly affect the generated heat input and the morphology of the processed zone. The peak temperature in the center of the processed zone decreases with increasing the travel speed from 50 to 300 mm/min at all applied pin geometries. The maximum temperature of ~400 °C was reached using the cylindrical pin geometry. The machine torque increases with increasing the travel speed at all applied pin geometries, and the highest torque value of 73 N.m is recorded using the square pin geometry at 300 mm/min travel speed. The top surface roughness of the processed area using the cylindrical pin is lower than that given by the other pin geometries. Under all applied conditions, the hardness of the processed area increases with increasing travel speed, and the cylindrical pin shows a higher hardness than the other pin geometries with 19% enhancement over the BM. The AA1050 processed using a cylindrical pin at 200 mm/min travel speed and a rotation speed of 600 rpm produces a sound processing zone with the highest ultimate tensile strength of 79 MPa.

Friction Stir Spot Welding of Different Thickness Sheets of Aluminum Alloy AA6082-T6.

Friction stir spot welding (FSSW) is one of the important variants of the friction stir welding (FSW) process. FSSW has been developed mainly for automotive applications where the different thickness sheets spot welding is essential. In the present work, different thin thickness sheets (1 mm and 2 mm) of AA6082-T6 were welded using FSSW at a constant dwell time of 3 s and different rotation speeds of 400, 600, 800, and 1000 rpm. The FSSW heat input was calculated, and the temperature cycle experience during the FSSW process was recorded. Both starting materials and produced FSSW joints were investigated by macro- and microstructural investigation, a hardness test, and a tensile shear test, and the fractured surfaces were examined using a scanning electron microscope (SEM). The macro examination showed that defect-free spot joints were produced at a wide range of rotation speeds (400-1000 rpm). The microstructural results in terms of grain refining of the stir zone (SZ) of the joints show good support for the mechanical properties of FSSW joints. It was found that the best welding condition was 600 rpm for achieving different thin sheet thicknesses spot joints with the SZ hardness of 95 ± 2 HV0.5 and a tensile shear load of 4300 ± 30 N.

Bobbin Tool Friction Stir Welding of Aluminum: Parameters Optimization Using Taguchi Experimental Design.

This work aims to optimize the performance evaluation characteristics such as the temperature at the weld center of the lap joint (Tw), the tensile shear load (TSL), and the hardness using an experimental design experiment for bobbin tool friction stir welding (BT-FSW) of AA1050 lap joints. BT-FSW is characterized by a fully penetrated pin and double-sided shoulder that promote symmetrical solid-state welds. This study contributes to improving the quality of 10 mm thick lap joints and addressing challenges to obtaining a sound weld deprived of any defects. Taguchi L9 orthogonal array (OA) experimental design was performed. Three different pin shapes (cylindrical, triangular, and square) and three levels of welding travel speeds of 200, 400, and 600 mm/min were selected as input controllable process parameters at a constant tool rotation speed of 600 rpm. A travel speed of 200 mm/min with square pin geometry significantly improves the TSL of the joint up to 6491 N. However, the hardness characteristic is optimized by using 600 mm/min travel speed and a cylindrical tool pin. The minimum temperature in the weld joint can be obtained using 600 mm/min or more with triangular pin geometry. From ANOVA results, it was seen that the BT-FSW of AA 1050 thick lap joints performance in terms of TLS and Tw were greatly influenced by travel speed; however, the tool shape influences the hardness more. For the validation of the models, BT-FSW experiments have been carried out for AA1050 using the applied processing parameters. Furthermore, regression models were developed to predict the Tw, TSL, and hardness. The calculated performance properties from the mathematical models were in an acceptable range compared to the measured experimental values.

Microstructure, Crystallographic Texture, and Mechanical Properties of Friction Stir Welded Mild Steel for Shipbuilding Applications.

In the current work, mild steel used in shipbuilding applications was friction-stir-welded (FSWed) with the aim of investigating the microstructure and mechanical properties of the FSWed joints. Mild steel of 5 mm thickness was friction-stir-welded at a constant tool rotation rate of 500 rpm and two different welding speeds of 20 mm/min and 50 mm/min and 3° tool tilt angle. The microstructure of the joints was investigated using optical and scanning electron microscopes. Additionally, the grain structure and crystallographic texture of the nugget (NG) zone of the FSWed joints was investigated using electron backscattering diffraction (EBSD). Furthermore, the mechanical properties were investigated using both tensile testing and hardness testing. The microstructure of the low-welding-speed joint was found to consist of fine-grain ferrite and bainite (acicular ferrite) with an average grain size of 3 µm, which indicates that the temperature experienced above A1, where a ferrite and austenite mixture is formed, and upon cooling, the austenite transformed into bainite. The joint produced using high welding speed resulted in a microstructure consisting mainly of polygonal ferrite and pearlite. This could be due to the temperature far below A1 experienced during FSW. In terms of joint efficiency expressed in terms of relative ultimate tensile, the stress of the joint to the base material was found to be around 92% for the low-speed joint and 83% for the high-welding-speed joint. A reduction in welding was attributed to the microstructure, as well as the microtunnel defect formed near the advancing side of the joint. The tensile strain was preserved at 18% for low welding speed and increased to 24% for the high welding speed. This can be attributed to the NG zone microstructural constituents. In terms of crystallographic texture, it is dominated by a simple shear texture, with increased intensity achieved by increasing the welding speed. In both joints, the hardness was found to be significantly increased in the NG zone of the joints, with a greater increase in the case of the low-welding-speed joint. This hardness increase is mainly attributed to the fine-grained structure formed after FSW.

The Effect of Salinized Nano ZrO2 Particles on the Microstructure, Hardness, and Wear Behavior of Acrylic Denture Tooth Nanocomposite.

The wear of acrylic denture teeth is a serious problem that can change the vertical dimensions of dentures. This study evaluates the effect of adding salinized nano ZrO2 particles on the microstructure, hardness, and wear resistance of acrylic denture teeth. Heat polymerizing polymethyl methacrylate resin was mixed with salinized ZrO2 at concentrations of 5 wt.% and 10 wt.%. Acrylic resin specimens without filler addition were used as a control group. SEM/EDS analyses were performed and the Vickers' hardness was evaluated. Two-body wear testing was performed using a chewing simulator with a human enamel antagonist. After subjecting the samples to 37,500 cycles, both height loss and weight loss were used to evaluate the wear behavior. The microstructural investigation of the reinforced-denture teeth indicates sound nanocomposite preparation using the applied regime without porosity or macro defects. The addition of zirconium oxide nanofillers to PMMA at both 5% and 10% increased the microhardness, with values of up to 49.7 HV. The wear mechanism in the acrylic base material without nanoparticle addition was found to be fatigue wear; a high density of microcracks were found. The addition of 5 wt.% ZrO2 improved the wear resistance. Increasing the nanoparticles to 10 wt.% ZrO2 further improved the wear resistance, with no microcracks found.

Probing phospholipid microbubbles by atomic force microscopy to quantify bubble mechanics and nanostructural shell properties.

Microbubbles (MBs), which are used as ultrasonic contrast agents, have distinct acoustic signatures which enable them to significantly enhance visualisation of the vasculature. Research is progressing to develop MBs which act as drug/gene delivery vehicles for site-specific therapeutics. In order to manufacture effective theranostic vehicles, it is imperative to understand the mechanical and nanostructural properties of these agents; this will enrich the understanding of how the structural, biophysical and chemical properties of these bubbles impact their functionality. We produced microfluidic phospholipid-based MBs due to their favourable properties, such as biocompatibility and echogenicity, as well as the ability to modify the shell for targeting applications. We have drawn upon atomic force microscopy to conduct force spectroscopy and tapping-mode imaging investigations. We have, for the first time to our knowledge, been able to accurately quantify the thickness and lipid configuration of phospholipid-shelled MBs - showing a trilayer as opposed to the conventional monolayer structure. Furthermore, we have measured MB stiffness and employed different mechanical theories to quantify the Young's modulus. We show that the Reissner theory is inappropriate for mechanical characterisation of phospholipid MBs, however, the Hertz model does offer biologically relevant comparisons. Analysis using the Alexander-de Gennes polymer brush theory has allowed us to provide new information regarding how the thickness of the polyethylene glycol brushes, end-grafted to our phospholipid microbubbles, changes with diameter.