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51.
Thermal autofrettage is a potential process to generate beneficial compressive residual stresses at and around the inner wall of a thickwalled cylinder for increasing its pressure carrying capacity. Due to its simplicity and inexpensive arrangement, it can compete with the conventional hydraulic autofrettage process. In this work, a comparative study of the thermal autofrettage and the hydraulic autofrettage is carried out. As the thermal autofrettage does not require hydraulic power pack, the process is more economical than the hydraulic autofrettage. The thermal autofrettage process is also studied for the thick-walled cylindrical vessels subjected to high thermal gradient with or without pressure and is compared with the hydraulic autofrettage. Comparison shows that for cylinders subjected to high thermal gradient without pressure, the thermal autofrettage is superior to the hydraulic autofrettage. 相似文献
52.
K. Kamal Babu K. Panneerselvam P. Sathiya A. Noorul Haq S. Sundarrajan P. Mastanaiah C. V. Srinivasa Murthy 《The International Journal of Advanced Manufacturing Technology》2018,94(9-12):3117-3129
In this paper, parameter optimization of FSW of cryorolled AA2219 alloy was carried out to obtain defect free weld joint with maximum weld strength. To achieve this, artificial neural network (ANN) was used to model the relationship between the input parameters and the mechanical and corrosion properties (output) of the weld joints. The optimal FSW parameters were determined by genetic algorithm (GA). The feasible solution of the GA was tool rotational speed of 1005 rpm, tool travel speed of 20 mm/min and tool tilt angle of 3°. The feasible parameter was used to weld and check the ability of the parameter to produce better weld joint than the L9 orthogonal array parameters. The weld, subjected to the confirmation test, was investigated by means of metallurgical, mechanical, and corrosion testing. This process reduces the costs associated with trial runs to obtain optimal parameters and also the production cost of the cryorolled (CR) plate which is high. 相似文献
53.
Astrid Ahlinder Tiziana Fuoco Álvaro Morales-López Mohammed A. Yassin Kamal Mustafa Anna Finne-Wistrand 《应用聚合物科学杂志》2020,137(15):48550
Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(ε-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48550. 相似文献
54.
The spray-freeze drying (SFD) technique was applied to sonicated aqueous suspensions of spray-dried montmorillonite clay (MMT) to produce highly porous agglomerates (SFD-MMT). Both MMT (used as a reference) and SFD-MMT were subsequently incorporated in polypropylene (PP) via melt compounding to produce 2 wt % nanocomposites with and without maleic anhydride grafted polypropylene (PP-g-MA). Polypropylene nanocomposites containing SFD-MMT exhibited thinner silicate flake layers compared to large agglomerates in PP/MMT nanocomposites. SFD-MMT particles became even more finer in the presence of PP-g-MA (i.e., in PP/PP-g-MA /SFD-MMT) where it hindered PP crystallization instead of serving as nucleation sites for the PP crystallization during rapid cooling. SFD-MMT improved the thermal stability of PP/PP-g-MA by 30°C compared to only 5–8°C for MMT/nanocomposites. MMT acts as a heterogeneous nucleating agent in the nucleation-controlled PP nanocomposites, but the hindrance effect was observed for the PP/PP-g-MA with SFD-MMT. PP/PP-g-MA/SFD-MMT exhibited twice the edge surface energy as compared to PP/PP-g-MA/MMT. The incorporation of both types of MMT raised the tensile moduli of PP and PP/PP-g-MA, with no improvement in their tensile strength and a decrease in the elongation at break. The PP/PP-g-MA/SFD-MMT showed brittle failure. POLYM. ENG. SCI., 60:168–179, 2020. © 2019 Society of Plastics Engineers 相似文献
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57.
Phase change materials (PCMs) play a leading role in overcoming the growing need of advanced thermal management for the storage and release of thermal energy which is to be used for different solar applications. However, the effectiveness of PCMs is greatly affected by their poor thermal conductivity. Therefore, in the present review the progress made in deploying the graphene (Gr) in PCMs in the last decade for providing the solution to the aforementioned inadequacy is presented and discussed in detail. Gr and its derivatives ((Gr oxide (GO), Gr aerogel (GA) and Gr nanoplatelets (GNPs)) based PCMs can improve the thermal conductivity and shape stability, which may be attributed to the extra ordinary thermo-physical properties of Gr. Moreover, it is expected from this review that the advantages and disadvantages of using Gr nanoparticles provide a deep insight and help the researchers in finding out the exact basic properties and finally the applications of Gr can be enhanced.In this work, Gr and its derivatives based PCMs was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM) by which crystal structure was known, phase was identified along with the knowledge of surface structure respectively. The increase in the mass fraction (%) of the filler (Gr and its derivatives) led to even better thermo-physical properties and thermal stability. The thermal characterization was also done by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and thermal conductivity tests. The enthalpy of freezing and melting showed that Gr and its derivatives based PCMs had a very high energy storage capability as reflected in its various applications. 相似文献
58.
Folahan O. Ayorinde Eisa Elhilo Caswell Hlongwane Kamal A. Saeed 《Journal of the American Oil Chemists' Society》1999,76(10):1217-1221
Matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) has been used to identify
eight triacylglycerols (TAG) in Vernonia galamensis oil (VO). The TAG include trivernolin, divernoloylstearoylglycerol, divernoloyloleoylglycerol, vernoloyllinoleoylstearoylglycerol,
vernoloyllinoleoyloleoylglycerol, and vernoloyldilinoleoylglycerol. Samples for the MALDI/TOF/MS analysis were prepared with
alpha-cyano-4-hydroxycinnamic acid (matrix) in an acetonitrile/tetrahydrofuran solvent system. A mol ratio of matrix/VO (44:1)
gave reproducible composite spectra, resulting in resolutions greater than 8,000 and signal-to-noise ratios of above 1000
for the most abundant molecular species. 1,3-Dioleoyl-2-stearoylglycerol and 1,2-dioleoyl-3-palmitoylglycerol were used as
calibration standards. 相似文献
59.
Mohammad Maududul Huq Md. Robiur Rahman Masnun Naher Mohammad Mizanur Rahman Khan Mostafa Kamal Masud Golam Mohammad Golzar Hossain Nianyong Zhu Yih Hsing Lo Muhammad Younus Wai-Yeung Wong 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(6):1243-1252
Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (1H, 13C and 31P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh3, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S1 → S0) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts. 相似文献
60.
Effects of Rheological Behavior of Viscoelastic Surfactants on Formation Damage in Carbonate Rocks
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Muhammad Shahzad Kamal Mohamed Mahmoud Mohammed Hanfi 《Journal of surfactants and detergents》2018,21(5):677-685
Viscoelastic surfactants (VES) are used in various oilfield applications such as matrix stimulation and enhanced oil recovery. The loss of surfactants during the propagation of VES could result in a significant reduction in the permeability of the rock (formation damage). The objective of the current work was to identify the effect of rheological behavior of the VES on the formation damage using core‐flooding experiments, nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM) analysis. A combination of core‐flooding, NMR, and SEM techniques was used to quantify and identify the location of formation damage in carbonate core samples. The viscosity and storage modulus strongly depend on the nature and concentration of salts. The viscosity increased by increasing the salt concentration up to a specific point (15 wt% CaCl2) and then starts decreasing. The VES formulations that displayed the maximum and minimum viscosities were used to identify the impact of rheological behavior on formation damage. Core‐flooding experiments were performed to assess the formation damage due to high‐viscosity and low‐viscosity VES formulations. The reduction in the permeability of carbonate rocks reaches more than 90% of the initial permeability. It was found that low‐viscosity VES caused more damage compared with high‐viscosity VES when they were used at constant concentrations. NMR and core‐flooding results revealed that the damage took place both in pore body and pore throat. However, most of the surfactant was retained at the pore throat. 相似文献