High Stir Research Articles

MRI of knee: high signals in STIR sequences and its relation with anterior knee pain our population.

Objective: To evaluate the significance of high signals in STIR sequences in MRI in patients presenting with non-traumatic knee pain. Study Design: Cross-sectional study. Setting: Department of Radiology, Liaquat National Hospital, Karachi, Pakistan. Period: March 2023 to August 2023. Methods: The patients presented for MRI of knee joint for knee pain unrelated to trauma were analyzed. Data were collected through a proforma based on 9 questions that included demographic data and questions related to the cause of pain. The total calculated sample size was 86 patients Data was analyzed through SPSS. Descriptive statistics were calculated. Association was determined using chi-square test considering p-value ≤0.05 as significant. Results: Our study showed no statistical correlation between knee pain and high STIR signals seen in pre-patellar bursa with 90.9% showing high signals with pain, while 85.3% showed high signals without pain. In our study this signal was found in about 20-30% that were mostly female household help and carpet layers. Conclusion: There is no statistical correlation between knee pain and high STIR signals seen in pre-patellar bursa.

Two-Dimensional Customer Segmentation for Digital Custom Coupon Issuance Approach

With the improvement of large information and profound learning innovation, enormous information and profound learning innovation have likewise been applied to the showcasing field, which was a piece of business organization. Client agitate the board is one of the main areas of promoting. In this paper, we proposed a technique to forestall client beat and increment buy transformation rate by giving tweaked rebate coupons to clients with high stir rate in light of huge information continuously. In the wake of sectioning client portions with two-layered fragment examination, a continuous beat rate assessment model in light of clickstream information was created for each portion. From that point onward, we gave tweaked coupons to our clients. At last, we tried the transformation rate and deals development. A two-layered group investigation based stir rate assessment joined with a proposal framework was viewed as essentially more helpful than the particular straightforward models. Utilizing this proposed model, it is feasible to increment deals via consequently assessing the client's stir likelihood and shopping penchant without the weight of showcasing costs in the web based shopping center

Long term hydrogen storage properties of ZK60 Mg-alloy as processed by different methods of SPD

Hydrogen storage characteristics is studied in the Mg-alloy ZK60 after processing by different SPD (Severe Plastic Deformation) methods such as High Pressure Torsion (HPT) and Friction Stir Processing (FSP), applying various deformation extents and rates. The capacity and kinetics of hydrogen storage was investigated and analysed, up to 100 storage cycles. While the degree of SPD deformation is less important for the storage capacity, the SPD processing method itself matters, yielding about ~ 30% more capacity in FSP than in HPT. As shown by DSC and XRD analyses, it is the density of SPD-induced vacancy agglomerates which is significantly higher in FSP than in HPT (~ 10–3 instead of ~ 10–4) because of the enhanced dislocation slip activity. Thanks to their stabilization through Mg(Zn,Zr) precipitates, the vacancy agglomerates survive numerous cycles of hydrogen storage in spite of the high storage temperature of 350 °C, and can act as thermally stable heterogeneous nuclei for the hydrogenation. This latter mechanism was found in all SPD methods applied irrespective of the deformation extent, on the basis of Johnson–Mehl–Avrami-Kolmogorov analysis providing the Avrami exponent n = 1, already from the second up to the highest hydrogen storage cycles.

Fatigue life, distortion behavior of AA 8011- nano B4C composite using simulated acoustic emission technique – An experimental and statistical appraisal

The high quality AA8011 aluminium alloy dispersed with different percentages of nano-sized B4C (0, 0.5,1 and 1.5 wt%) was fabricated by electromagnetic frequency high energy stir casting technique. The characterization study on metal matrix nanocomposites (MMNC) using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive Spectrum (EDS), and X-ray Diffraction (XRD) confirmed the morphology and distribution of AA8011 with nano B4C. The microhardness analysis and strength using Vickers hardness testing and Electromechanical Universal Testing Machine, respectively, show significant mechanical properties improvement. The ductility study on Scanning Electron Microscope (SEM) images of the fractured samples reveal the transition from ductile to brittle nature in MMNCs. The online monitoring using Acoustic Emission (AE) during a tensile test indicates the mitigation in crack generation and its propagation. The substantial enhancement in fatigue life by the addition of nano B4C was evidenced by testing at a stress ratio (R = 0.1) and statistically significant (at p < 0.05) by one way Analysis of Variance (ANOVA). The SEM Fractography of fractured fatigue samples discloses the influence of dispersal of nano-sized reinforcements which resist fatigue crack growth. The result demonstrates that AA8011-1.5 % nano B4C composite has improved hardness, higher tensile strength and fatigue strength than the pure matrix due to the addition of the B4C.

Thermal cycles, microstructures and mechanical properties of AA7075-T6 ultrathin sheet joints produced by high speed friction stir welding

0.5 mm thick AA 7075-T6 ultrathin sheets were butt jointed by conventional friction stir welding (C-FSW) and high speed friction stir welding (HS-FSW) under a constant rotational speed ( ω )/welding speed ( v ) ratio of 6.67 rad/mm using a pinless tool. In this study, the conventional ω of 2000 rpm and conventional v of 300 mm/min were adopted by C-FSW, and the high ω of 8000 rpm and high v of 1200 mm/min were adopted by HS-FSW. Compared with C-FSW, HS-FSW presented a fast heating and cooling rate thermal characteristic with a slightly higher peak temperature and significantly shorter elevated-temperature exposure time. Kissing bond defect was appeared in the weld bottom for C-FSW. While, no obvious defect was found in the weld obtained by HS-FSW. Compared with C-FSW, the proportion of deformed grains in the center of nugget zone (NZ) fabricated by HS-FSW was increased. For the joint fabricated by HS-FSW, the upper NZ was dominated by recrystallized grains, and the lower NZ was dominated by deformed grains. The ultimate tensile strength of the joint fabricated by HS-FSW can reach 87% of base metal (BM), and its elongation, yield strength and ultimate tensile strength were increased by 58.8%, 23.3% and 22.8% respectively compared with C-FSW. Both the joints fractured in the center of the NZ. The joint fabricated by C-FSW broke due to the kissing bond defect. While the joint fabricated by HS-FSW may be broken due to the weld thickness reduction. • The thermal cycle characteristics of HS-FSW were revealed. • The effect of the thermal cycle on microstructure was revealed. • The microstructures of the joint produced by HS-FSW were investigated by EBSD. • The tensile properties of the joint produced by HS-FSW were superior to by C-FSW.

High speed friction stir welding of AA6063-T6 alloy in lightweight battery trays for EV industry: Influence of tool rotation speeds

Present work demonstrates high speed friction stir welding (HSFSW) of light weight battery trays assembly in electric vehicle (EV). Despite of solid-state and green nature of FSW, it suffers from the relatively low welding speed. With the help of suitable tool design and machine tool parameters, we successfully achieved defect-free welds at high welding speed of 4.0 and 4.5 m/min. Good quality welds are produced in 3 mm thick AA6063-T6 extruded aluminium alloy at such a high welding speeds by implementing violent material mixing i.e., higher tool rotation speeds (3500–4500 rpm) and plunge force (8.5–10.5 kN). The HSFSW cross-section registered curious hardness profile of ‘U’ shape. HSFSW resulted softening of weld stir zone (∼60 HV) along with HAZ (∼50 HV). The highest joint efficiency of 72 % was found for the weld produced at 4.0 m/min and 3500 rpm.

Tensile property response of AZ91 Mg alloy subjected to pre-aging and high-force friction stir processing

Pre-aging and high force friction stir processing were applied to Mg–9Al–1Zn alloy. The stir zone exhibited an enhanced yield strength due to grain refinement, dislocation strengthening, precipitate strengthening, and texture randomization. The activation of {101‾2} twins contributed to coordinating plastic deformation for improving the work hardening ability and ductility.

Microstructure and corrosion behavior of Al-Ti-TiC-CNTs/AZ31 magnesium matrix composites prepared using laser cladding and high speed friction stir processing

Al-Ti-TiC-CNTs/AZ31 magnesium matrix composites (MMCs) were prepared using laser cladding (LC) and high speed friction stir processing (HS-FSP). The surface microstructure, phase composition, microhardness distribution and corrosion resistance of the MMCs were studied using scanning electron microscope (SEM), X-ray diffraction (XRD), microhardness tester and electrochemical workstation. The composite layers were composed of phases with different geometric morphology and distribution characteristics identified as α-Mg, Al12Mg17 and TiC phases. A defect-free LC composite layer with refined microstructure and a sound metallurgical bonding interface between the LC composite layer and the matrix were observed. In addition to maintaining the sound metallurgical bonding interface, the microstructure of the LC composite layer was significantly refined and densified after being subjected to HS-FSP. The surface microhardness and self-corrosion potential of the MMCs prepared using LC was obviously enhanced due to the formation of a large number of Al12Mg17 and TiC phases, but they show a decreasing trend with decreasing the Al12Mg17 and TiC phases. The MMCs produced using HS-FSP exhibited higher surface microhardness and better corrosion properties than those of the LC due to the formation of finer and denser microstructure and higher numbers of Al12Mg17 and TiC phases in the composite layers.

Effect of friction stir welding tool hardness on wear behaviour in friction stir welding of AA-6060 T66

Friction stir welding is a solid-state joining process with a wide range of industrial applications in the e-mobility, automotive, aerospace and energy industries. However, friction stir welding is subjected to process-specific challenges, including comparatively high process forces and friction stir welding tool wear resulting from tribological interaction between the tool and workpiece. The geometric-related friction stir welding tool wear can cause varying material flow conditions, lateral path deviations and premature tool failure, with detrimental economic and technological consequences. This study systematically analyses the wear behaviour of friction stir welding tools as a function of tool hardness. To compare and differentiate the geometric-related tool wear as a function of tool hardness, experiments were carried out with a hardness of 240 HV, 410 HV and 580 HV. Whereas 240 HV is non-hardened, 410 HV is 50% of the secondary hardness maximum and 580 HV is the secondary hardness maximum of the tools made of H13 tool steel (hot-working steel, X40CrMoV5-1). During the experimental tests, the shoulder and probe exhibited varying wear and geometrical deviations. The investigations were carried out with a force-controlled robotized welding setup in which AA-6060 T66 sheets with a thickness of 8 mm were joined by weld seams up to a total length of 80 m.

Analysis of Mechanical and Sliding Wear Performance of Hybrid AA7075-SiC/Gr/Cu Alloy Composites Fabricated by High Vacuum Stir Casting Process

Analysis of Mechanical and Sliding Wear Performance of Hybrid AA7075-SiC/Gr/Cu Alloy Composites Fabricated by High Vacuum Stir Casting Process

Microstructure, Tensile Properties, and Wear Resistance of In Situ TiB2/6061 Composites Prepared by High Energy Ball Milling and Stir Casting

Microstructure, Tensile Properties, and Wear Resistance of In Situ TiB2/6061 Composites Prepared by High Energy Ball Milling and Stir Casting

Tribological, Thermal and Corrosive Behaviour of Aluminium Alloy 2219 Reinforced by Si3N4 Nanosized Powder

The Metal Matrix Composite (MMC) technique is the most effective contrast method when compared with other techniques. By using the method of high energy stir casting, Aluminium alloy Al2219 is reinforced with various percentages of Si3N4 (0, 3, 6, and 9 %) particles. X-ray diffraction along with Scanning electron microscope was performed to characterize the composite. The mechanical and thermal behaviours such as differential thermal analysis thermo gravimetric analysis/, tensile, wear and hardness behaviours were investigated. By using electro chemical potentiodynamic polarization test, the consequence of heat treatment on the corrosion behaviour of the composites when compared to its matrix in 3.5 % NaCl when at 600 rpm was also investigated. In this experimental study, the wear of the aluminium composites was significantly decreased on addition of Si3N4 particles. The study also revealed that, since the inclusion of Si3N4 in the samples and compared to the base aluminium alloy, the mechanical properties of the composites, such as wear resistance, hardness and tensile strength increased by percentage. The surface morphology and Scanning electron microscope analysis of worn surfaces in the test pieces unfold that with the increase in reinforcement content, wear rate decreases.

Investigating the Effect of Si3N4 Reinforcement on the Morphological and Mechanical Behavior of AA2219 Alloy

The present investigation aims to investigate the mechanical, metallurgical and morphological study of Aluminium Alloy AA2219 reinforced with various percentage of Si3N4 (0,3,6 and 9) particles by high energy stir casting method. The structural characterization was carried out by XRD, EDAX, Radiography and SEM tests. Hardness, tensile and compression test reveals the mechanical behaviour of this material. Microstructure test reveals the uniform distribution of the reinforced material. Wear behaviour of the developed aluminium matrix composite (AMC) was investigated under different conditions of applied load, operation time and speed. The analysis carried out at room temperature for two different loads (20 N and 40 N) with varying two different operation times (30 mins, 60 min). The results showed that the mechanical properties, like tensile strength, compression strength and hardness exaggerated by the proportion of Si3N4 gift within the samples compared with base metal AL alloy. The surface morphology analysed through small structural analysis discovered that the reinforcement was uniformly distributed within the matrix. Worn surface of the test pieces was analysed by SEM and the surface morphology reveals that the wear rate reduced with the increase in reinforcement content.

Standardized Stirring for Small Scale Surveys**

AbstractStirring rates in heterogeneous catalytic reactions have an effect on reaction rates. When conducting small‐scale surveys using a single central stir plate, reaction vessels in different positions experience slightly different levels and patterns of agitation. We probed this effect by running the same reaction 40 times, varying the stir rate (fast/slow) and the vial position using two 3D‐printed vial holders. We found variability of conversion (measured mass spectrometrically) to be approximately two times higher for vials placed somewhat randomly in comparison to when vials are consistently placed at a fixed distance from the centre of the stir plate, but the effect was relatively small and could be minimized by using a high stir rate. For those experimenters wishing to completely eliminate differential stirring as a cause for variation in results, the 3D‐printed circular array we designed is recommended over a conventional rectangular array.

Optimization of sliding and mechanical performance Ti/NI metal powder particulate reinforced Al 6061 alloy composite using preference selection index method

Abstract In this study, Ti/ Ni reinforced in AA6061 composites were prepared via a high vacuum stir casting method. The fabricated composite specimens are prepared for experimental studies as per ASTM standard and then physical, mechanical, and sliding wear characterization was conducted on different equipment. The higher confidence level (95%) obtained via experimental studies. The experimental results of the specimen have been used for optimization, and the ranking order of composite are computed via using the preference selection index method. Many researchers’ results have been reported and easily computed to rank of composite composition using optimization properties such as void contents,density flexural strength, tensile strength, impact strength, wear resistance etc. The resultsreveal that the base matrix included with the equal presence of both particulates exhibits most excellent properties hence to obtained best ranked of composition using the PSI method. Therefore, the PSI method could be helpful for decision making triumphantly in the material selection.

Understanding the effect of tool geometrical aspects on intensity of mixing and void formation in friction stir process

The reduction of agglomeration of particulate reinforcement in friction stir processing and elimination of joint line remnant in friction stir welding depends on stirring ability of friction stir tool. The magnitude of stirring is indicated by the intensity of material inter-mixing in tool interacted region. Present investigations analyse the influence of geometrical aspects of classical friction stir tool on the intensity of material intermixing, location of high stir regions and void formation during the steady-state phase of friction stir welding. The classical tool was chosen as its geometrical features undergo minimal wear in the harsher processing environment. Investigating material mixing using metallic inserts have their shortcomings due to different flow properties of insert/marker and parent material. Therefore, bi-colour plasticine configuration possessing primary colours was adopted to understand the level of intermixing. The hue attribute of the generated secondary colour was utilised to identify and quantify material mixing. Experimental results revealed that the pin diameter positively influenced mixing and negatively affected void formation. Shoulder size and pin taper angle aided in the closure of void with inferior mixing. The intensity of mixing enhances on selection of tools possessing a shoulder to pin diameter ratio of 2.5. Finite element simulation studies were conducted to understand the reasons for mixing under certain tooling conditions. Since material subjected to stirring is concentrated primarily on a portion of advancing side, components of shear strain, shear strain rates, shear stress and velocity were tracked for this portion of processed material during its interaction with tool pin for one complete rotation.

Surface area expansion by flower-like nanoscale layered double hydroxides for high efficient stir bar sorptive extraction

Enhancing the surface area of stationary phase is essential in chromatographic science. In this work, nanoscale NiAl-layered double hydroxides (NiAl-LDHs) with flower-like structure was used as a platform for supporting the stationary phase. Then strong hydrophobic p-naphtholbenzein molecule was immobilized onto the LDHs layer as sorbent for stir bar sorptive extraction (SBSE). The flower-like LDHs layer significantly increased the extraction efficiency through increasing the specific surface area and immobilized amounts of stationary phase. In addition, the LDHs can also provide anion exchange ability, which expanded the application of this stir bar for analysis of not only hydrophobic but also anionic analytes. For improving the workability, a poly(ether ether ketone) (PEEK) jacket stir bar with detachable dumbbell-shaped structure was employed. The PEEK jacket with high mechanical strength and dumbbell-shaped structure improved the durability of stir bar and the detectable design allowed elution to be realized with less solvent that enhanced the enrichment factor. The proposed stir bar showed good performance for the extraction of multiple analytes including flavonoids, non-steroid anti-inflammatory drugs and chlorophenoxy acids. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), the SBSE-HPLC-UV method was applied for the extraction of three active components including bavachin, isobavachalcone and bavachinin in Psoralea corylifolia L. herb with low limit detection of 0.01–0.02 ng/mL.

High Speed Friction Stir Welding of 5182-H111 Alloy: Temperature and Microstructural Insights into Deformation Mechanisms

This paper reports the results of an investigation of thermal cycles and microstructural development in 5182-H111 aluminium alloy during low speed (0.2 m/min) and high speed (1.5 m/min) friction stir welding (FSW), using quenched pin-break specimens. The results show that welds made at both speeds have excellent mechanical properties, although these derive from different thermomechanical mechanisms. For the low speed weld thermal conductivity plays the most significant role in the development of microstructure, while in the case of high speed welding it is the high strain rate plastic deformation that is the dominant mechanism. The yield strength in the stir zone of both the 0.2 m/min and 1.5 m/min welds could be explained through the Hall–Petch relationship, leading to an observable increase in the case of the 1.5 m/min weld. By contrast, an increase in yield strength beneath the shoulder of the 1.5 m/min weld was driven by strain hardening.

Characterization, corrosion and failure strength analysis of Al7075 influenced with B4C and Nano-Al2O3 composite using online acoustic emission

This paper aims to establish the mechanical, corrosion and failure analysis using online acoustic emission of Al7075 alloy, Al7075-B4C composite and Al7075- B4C-Al2O3 hybrid composite with different Boron Carbide (B4C) content of 5, 10, 15 & 20% and Nano Aluminium Oxide (Al2O3) content of 2% on a weight basis with the high energy stir casting method. The casted samples have been characterized by x-ray Diffraction (XRD), Thermo gravimetric analysis (TGA/DSC), Energy Dispersive Spectrum (EDS), and Scanning Electron Microscope (SEM). In case of hybrid composite, the hardness and the tensile strength decrease when the content of Al2O3 increases. However, in the present research, the addition of B4C with nano Al2O3 particles in certain proportions has increased the hardness and tensile strength. In addition, the tensile fractographs of the specimens were analysed using SEM. Acoustic Emission (AE) method was used for monitoring the acoustic energy that are released at the time of deformation process and early crack detection. The influence of the volume fraction of the B4C particulates on the microstructural and corrosion characteristics of Al7075- B4C with nano Al2O3 metal matrix composites (MMCs) was also studied. It has been observed from the literature that the direct strengthening of composites occurs due to the presence of hard ceramic phase, while the indirect strengthening arises from the thermal mismatch between the matrix alloy and reinforcing phase during solidification. Based on the database for material properties, the application area of HAMCs has been proposed in the present review. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel Nano composites.

Room Temperature Superplaticity in Fine/Ultrafine Grained Materials Subjected to Severe Plastic Deformation

Achieving superplasticity at high temperatures and at very low strain rates is considered to be the most important disadvange of superplastic forming processes. Therefore, it is crucial to achieve superplastic behavior at low temperatures and high strain rates. To do so, it is well known that, high amount of grain refinement in the superplastic material is required. Very recent advances in severe plastic deformation (SPD) techniques based on imposing very high strains to the material provide abnormal grain refinement, and ultrafine-grained (UFG) microstructures can be achived in metallic materials by this manner. Formation of UFG microstructures via SPD methods like equal channel angular pressing (ECAP), high pressure torsion (HPT) and friction stir processing (FSP) bring about superplastic behavior in some classes of alloys even at room temperature (RT) as an extreme example of low temperature superplasticity. This paper overviews the studies aiming to investigate the RT superplasticity in some specific metals and alloys after UFG formation by SPD methods. UFG formation or nanostructuring of the materials by SPD to attain RT superplasticity were analyzed in detail. Also, the parameters affecting the RT superplasticity in different classes of materials and superplastic deformation mechanisms operated at RT superplasticity were explained.