Investigation the effect of dissimilar laser welding parameters on temperature field, mechanical properties and fusion zone microstructure of inconel 600 and duplex 2205 stainless steel via response surface methodology.

This study focused on dissimilar welding characterization of Inconel 600 and duplex 2205 stainless steel using central composite design (CCD) of experiments the response surface methodology (RSM). This study determined the effect of laser welding parameters and the reactions of the temperature field on the melt pool, the mechanical characteristics of the weld joint, and the geometry of the melt pool. According to the ANOVA results, the power of laser and focal distance were found to be the most influential factors on the temperature of both Inconel 600 and duplex stainless steel. The weld joint's tensile strength and elongation were significantly influenced by laser power and focal distance. Increasing the laser power from 250 to 450 W raised the tensile strength from 250 to 550 MPa. The Mo rich phases formed at the inter-dendritic region according to the EDS phase analysis results in loss of ductility and the resultant tensile strength of the samples failure from the fusion zone adjacent to the duplex stainless steel. At high laser power levels, the samples fractured from fusion zone while at lower laser powers below 350 W, the samples fractured from the HAZ and the areas adjacent to the duplex steel fusion line. The micro-hardness value of the weld joint at different laser power of 525 W and 375 W was increased to the maximum values of 370 and 325 HV, respectively from the fusion line of Inconel 600 to the center of the fusion zone. Further, molten pool microstructure of the dissimilar joint zone was mainly composed of a cellular and columnar dendritic structure Variations in melt flow, temperature gradient and solidification rate from the molten scan line to the weld center clearly changed the grain growth and the resultant microstructure in different areas of the fusion zone. By transferring the laser light to the center of the Inconel 600 and duplex stainless steel joint, the molten pool depth was increased from 0.2 to 1.5 mm.

Investigation on the size and percentage effects of magnesium nanoparticles on thermophysical properties of reinforced calcium phosphate bone cement by molecular dynamic simulation.

In recent years, bone materials and cement innovation have made extraordinary strides. Calcium phosphate cement (CPC) regenerates body tissues and repairs bone and dental defects. Since the presence of nanoparticles (NPs) increased the initial cement strength in terms of the reduction of porosity, magnesium (Mg) NPs were used because of their unique properties. In this study, the effects of various Mg NP percentages and sizes on reinforced cement thermal behavior and mechanical behavior are investigated using the molecular dynamics (MD) simulation method. The changes of Young's modulus (YM), maximum temperature (MT), and ultimate strength (US) were investigated for this reason. The US, YM, and MT of the reinforced cement sample improved from 0.879 to 0.171 MPa to 1.326 and 0.255 MPa, respectively, and from 1321 to 1403 K by raising the NPs percentage to 4%. The radius increase of NPs to 16 Å enhanced the US, YM, and MT to 0.899 MPa, 0.179 MPa, and 1349 K. The MT decreased to 1275 K. The quantity and size of the Mg NPs significantly enhanced the mechanical behavior of the finished cement, according to the findings.

The effects of atomic percentage and size of Zinc nanoparticles, and atomic porosity on thermal and mechanical properties of reinforced calcium phosphate cement by molecular dynamics simulation.

This study used the molecular dynamics (MD) simulation method to assess the effects of different percentages of NPs, sizes, and percentages of porosity on reinforced cement thermal behavior (TB) and mechanical behavior (MB) of samples. The temperature and kinetic energy (KE) converged to 300 K and 35.42 eV after 10 ns, which indicated the thermodynamic equilibrium and the atomic stability in the structures. Increasing the NPs percentage from 1% to 3% increased the maximum temperature from 1364 to 1405 K. By further increasing it to 5%, it was reduced to 1361 K. As the radius of Zn NPs increased to 16 Å, the ultimate strength (US) and Young's Modulus (YM) increased from 1.07 to 0.19 MPa to 1.2 and 0.22 MPa. The increase in the NPs' radius to 16 Å caused an increase in the maximum temperature from 1405 to 1455 K, maintaining atomic stability. As the porosity increased from 1% to 5%, the US and YM reduced from 0.91 to 0.17 MPa to 0.81 and 0.15 MPa. As the porosity increased from 1% to 5%, the maximum temperature was reduced from 1400 K to 1384 K. According to the results, Zn NPs' percentage and size effectively improved the MB of the final cement.

The investigation of energy management and atomic interaction between coronavirus structure in the vicinity of aqueous environment of H2O molecules via molecular dynamics approach.

The coronavirus pandemic is caused by intense acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Identifying the atomic structure of this virus can lead to the treatment of related diseases in medical cases. In the current computational study, the atomic evolution of the coronavirus in an aqueous environment using the Molecular Dynamics (MD) approach is explained. The virus behaviors by reporting the physical attributes such as total energy, temperature, potential energy, interaction energy, volume, entropy, and radius of gyration of the modeled virus are reported. The MD results indicated the atomic stability of the simulated virus significantly reduced after 25.33 ns. Furthermore, the volume of simulated virus changes from 182397 Å3 to 372589 Å3 after t = 30 ns. This result shows the atomic interaction between various atoms in coronavirus structure decreases in the vicinity of H2O molecules. Numerically, the interaction energy between virus and aqueous environment converges to -12387 eV and -251 eV values in the initial and final time steps of the MD study procedure, respectively.

Experimental Investigation on the Shear Behaviour of Stud-Bolt Connectors of Steel-Concrete-Steel Fibre-Reinforced Recycled Aggregates Sandwich Panels.

Steel-concrete-steel (SCS) sandwich panels are manufactured with two thin high-strength steel plates and a moderately low-density and low-strength thick concrete core. In this study, 24 specimens were produced and tested. In these specimens, a new stud-bolt connector was used to regulate its shear behaviour in sandwich panels. The bolts' diameter, concrete core's thickness and bolts' spacing were the parameters under analysis. Furthermore, the concrete core was manufactured with normal-strength concrete and steel fibres concrete (SFC). Steel fibres were added at 1% by volume. In addition, the recycled coarse aggregate was used at 100% in terms of mass instead of natural coarse aggregate. Therefore, the ultimate bearing capability and slip of the sandwich panels were recorded, and the failure mode and ductility index of the specimens were evaluated. A new formula was also established to determine the shear strength of SCS panels with this kind of connectors. According to this study, increasing the diameter of the stud-bolts or using SFC in sandwich panels improve their shear strength and ductility ratio.

Simulation of blood flow into the popliteal artery to explain the effect of peripheral arterial disease: Investigation the conditions and effects of different foot states during the daily activity of the patient.

BACKGROUND AND OBJECTIVE: Peripheral artery disease, one type of atherosclerosis, is a common medical condition in the world that results from plaque build-up in the peripheral blood vessels. The symptoms of this disease are the senses of pain and weakness in outer muscles. METHODS: The artery under consideration is called the popliteal artery. In this model, the blood flow is considered as pulsating. Therefore the inlet boundary condition is taken as unsteady velocity, and the outlet boundary condition is taken the outflow. The inlet boundary condition represents the increasing systole flow and the decreasing diastole flow, which occur naturally in blood flow. Systolic flow occurs when the heart contracts and pumps blood into the arteries. The inlet blood flow is in the form of a sine-cosine parabolic profile. RESULTS: The artery bends from the middle at an angle of 45°. As the bending of the artery begins, the flow field also takes a bent form. At this point, the flow bends from the outside of the top wall and enfolds the bottom wall in its bending. For different periods, the popliteal flow is closer to the lower bend when the inlet velocity is more significant. While the top wall experiences a low-intensity region along the bend, the bottom wall experiences the same effect just before and after the bend. As the blood flows along the bend, the flow path becomes significantly curved near the bend, similar to the model. The clotted artery exhibits a large increase in flow due to a reduction in the cross-section as a result of the clotting in half of the artery. The flow before the clotting is not considerably different from the main model of the straight artery. CONCLUSIONS: Like shear stress, the pressure drop has a linear relationship with the blood HCT and, hence, the viscosity. The pressure drop decreases with the inlet velocity reaching its maximum value and then increases with the start of the acceleration reduction in the second and third-time steps. This indicates that the pressure drop has a stronger relationship with the acceleration than the inlet velocity.

The Effect of Hematocrit and Nanoparticles Diameter on Hemodynamic Parameters and Drug Delivery in Abdominal Aortic Aneurysm with Consideration of Blood Pulsatile Flow.

BACKGROUND AND OBJECTIVE: The present article has simulated to investigate the efficient hemodynamic parameters, the drug persistence, and drug distribution on an abdominal aortic aneurysm. METHODS: Blood as a non-Newtonian fluid enters the artery acting as a real pulse waveform; its behavior is dependent on hematocrit and strain rate. In this simulation of computational fluid dynamic, magnetic nanoparticles of iron oxide which were in advance coated with the drug, are injected into the artery during a cardiac cycle. A two-phase model was applied to investigate the distribution of these carriers. RESULTS: The results are presented for different hematocrits and the nanoparticle diameter. It is observed that hematocrit significantly affects drug persistence, so that lower hematocrit incites more accumulation of the drug in the dilatation part of the artery. The better drug accumulation is noticed, at the higher wall shear stress. Although no considerable impact on the flow pattern and wall shear stress was found with various nanoparticle diameters, the smaller size of the nanoparticles results in a greater amount of drug augmentation in the aneurysm wall output. CONCLUSIONS: At the higher hematocrit levels, the blood resistance to drug delivery increases throughout the artery. Also, the drug accumulates less on the aneurysm wall and stays longer on the aneurysm wall. On the contrary, the drug accumulates more by decreasing hematocrit level and stays shorter on the aneurysm wall. Moreover, the maximum drug concentration is observed at the lowest hematocrit level and nanoparticle diameter; also, the diameter of nanoparticles imposes no significant effect on the vorticity and wall shear stress. It is seen that the increment of the hematocrit level reduces the strength of vorticity and increases the amount of wall shear stress in the dilatation segment of the artery. The shear stress at three points of the dilatation wall is extreme, where the maximum density of nanoparticles occurs.

Roll of stenosis severity, artery radius and blood fluid behavior on the flow velocity in the arteries: Application in biomedical engineering.

In this work, the Sisko model is involved for blood flow simulation in the arteries with triangular shapes of stenosis, which is different in severities of 20%, 30%, and 40%, respectively. Firstly, the effects of different severity of stenosis as much as 20%, 30%, and 40% are investigated in the velocity of blood while artery radius of 0.002 m and Sisko parameters of n = 0.639 and b = 0.1735 are constant. Then, stenosis with the severity of 40% remains, and the radius of the artery is varied from 0.002 m to 0.0035 m to investigate the effects of artery radius on the blood velocity. Finally, different types of blood fluids are employed by manipulation of Sisko parameters, and influences of blood fluid behaviors are investigated in velocity profiles. It is reported that influences of increasing severity of stenosis and reducing the radius of the artery cause blood velocity to be augmented due to the role of stenosis as an obstacle against blood flow and influences of artery radius in reducing cross-section area of the vessel. Maximum velocities are roundabout 0.15 m/s, 0.185 m/s of 0.235 m/s in order of stenosis of 20%, 30% and 40% respectively. Also, investigation in the effects of the behavior of different blood showed that blood fluid types could change maximum flow velocity as much as 0.025 m/s. Despite of roll of stenosis severity, artery radius, and blood fluid behavior in exacerbation of velocity deviation, it was concluded that their consequences for the human body healthy can be ignorable in the range of studied.

Computer modeling of pulsatile blood flow in elastic artery using a software program for application in biomedical engineering.

BACKGROUND AND OBJECTIVE: Atherosclerosis-a condition in which an artery is constricted-alters blood flow in the artery, that can exacerbate the condition. Focusing on previous studies, it can be seen that the k-ε model has been used in the simulation. Therefore, the reverse flow on the back of stenosis is not well represented. In this study, the simulated results are much closer to clinical results, relying on the use of physiological pulses, and considering elasticity of the vessel wall, and the applying k-ω model. It can therefore be claimed that a much more accurate prediction will be made regarding the formation, development and progression of the disease. METHODS: Modeling biological systems usually contain many parameters, which cannot be calculated experimentally, or are too costly and time consuming. In addition, it is occasionally required to examine the influence of different physical variables, which, given the complexity of the governing equations, make analytical methods feasible (or very limited). The present study is an attempt to investigate the turbulent pulsatile blood flow in an elastic artery with single and double stenoses using a finite element software program, ADINA 8.8. RESULTS: According to the results, the k - ω turbulence model predicted a larger reverse flow in the post-stenotic region and between the two stenoses in comparison with the k - Îµ model. In other words, the k - ω model results suggest that a larger region is prone to atherosclerosis. In addition, that the k - Îµ model predicted a greater maximum shear stress at the throat and a shorter reverse flow region (Mean WSS < 0) in both stenosis scenarios. In other words, relative to the k - Îµ model, the k - ω model underestimated the damage to the plaque and the risk of its rupture though it predicted new stenosis developing behind the previous one. It was observed that the presence of a double stenosis causes the upstream pressure to reach the critical value in less time. Velocity profiles revealed that in the stenosis throat, the maximum velocity exceeds the normal biological state, which may cause disorders in the blood circulation. CONCLUSIONS: The artery wall displacement results are suggestive of the greater difference between the two turbulence models in the case with double stenosis compared with single stenosis. Moreover, the difference between the two turbulence models in double stenosis is minimized in both post-stenotic and pre-stenotic regions.

Mandatory and Self-citation; Types, Reasons, Their Benefits and Disadvantages.

This paper defines and discusses two important types of citations, self-citation and mandatory citation, in engineering journals. Citation can be classified in three categories: optional; semi-mandatory; and mandatory. There are some negative and positive impacts for the authors' paper and journals' reputation if mandatory citation of a paper or set of papers is requested. These effects can be different based on the recommended papers for citing in the new research. Mandatory citation has various types discussed in this paper. Self-citation and its reasons and impacts are also discussed in the present study.