SUMMARYUsing the finite element method a numerical procedure is developed for the solution of the two-dimensional frictional contact problems with Coulomb's law of friction. The formulation for this procedure is reduced to a complementarity problem. The contact region is separated into stick and slip regions and the contact stress can be solved systematically by applying the solution technique of the complementarity problem. Several examples are given to demonstrate the validity of the present formulation.
A variational formulation for a Timoshenko beam element is derived by the separation of the deformation mode into the bending deflection and shear deflection. Shear deflection is projected into bending deflection and the projection matrix is constructed by using the equilibrium equation and the relation of force and displacement. The exact stiffness matrix of the Timoshenko beam element can be obtained by the present method. Examples are solved in order to show the effectiveness of the beam element in comparison with other elements.
Two‐noded curved beam elements, CMLC and IMLC, are developed on the basis of Timoshenko’s beam theory and curvilinear co‐ordinates. These elements are developed by the separation of the radial displacement into the bending and the shear deflection and the projection of the shear deflection into bending deflection. In the CMLC element, field‐consistent membrane strain interpolation is adapted for removing the membrane locking. The CMLC element shows the rapid and stable convergence on the wide range of radius, thickness and length of the curved beam. The field‐consistent membrane strain and the separation of radial displacement produce the most efficient linear element possible.
Induction welding is a fast, clean, noncontact process that often uses a metal-mesh susceptor to facilitate localized controlled heating; however, the metal mesh presents various problems. In this study, the induction heating behavior of a 450 μ m thick thin-film susceptor, fabricated by mixing magnetite (Fe 3 O 4 ) nanoparticles (NPs) and PA6/carbon fiber (CF) (30%) thermoplastic resin, was examined with respect to the weight ratio of Fe 3 O 4 (50, 67, 75, and 80 wt%). The useful induction heating behavior of the 75 wt% Fe 3 O 4 susceptor suggested its suitability for additional heat treatment experiments, carried out at 3.4 kW at a frequency of 100 kHz. This susceptor attained the same maximum temperature during 10 cycles of repeated induction heating and cooling. It was then used to weld two thermoplastic composites, with 60 s of induction heating followed by 120 s of simultaneous cooling and pressing. The resulting welded joints had lap shear strength values of 36.8, 34.0, and 36.4 MPa under tensile test loads of 884, 817, and 874 N, respectively. Scanning electron microscopy images confirmed a uniform weld quality. Thus, the proposed manufacturing method, involving the incorporation of Fe 3 O 4 NPs into thermoplastic resin, should help expand the range of applications for thermoplastic composites.
The main treatments for cancer recorded to date include chemotherapy, radiotherapy, and surgery. Although we have achieved great success in treating certain types of tumors, there are still many incurable even with the help of modern treatments. Currently, the principles of magnetic-induction hyperthermia in magnetic nanoparticle hyperthermia are considered an effective treatment for cancer cells. As reported in previous articles, these nanoparticles generate a lot of heat that raises the temperatures of tumors, hence treating the cancer cells. The other significant potential of magnetic nanoparticles is the ability to combine heat and drug release for cancer treatment. However, within the biologically safe range of AC magnetic fields, the lack of induction heating power and the high criteria for biocompatibility in superparamagnetic-nanoparticle hyperthermia agents still make up the key challenges for the successful clinical application of magnetic hyperthermia. In this study, two different types of iron oxide nanoparticles (γ-Fe2O3, Fe3O4) were modified with whey protein isolate (WPI) to form bio-modified superparamagnetic nanoparticles with spherical or diamond-shaped structures and diameters between 20 and 100 nm, which demonstrate excellent stability under different conditions. Adriamycin (ADM) has also been successfully loaded onto these nanoparticles and used in this experiment. In vitro and in vivo experimental studies were performed using these WPI-modified nanoparticles on HepG2 tumor models and mice to assess their bioavailability and biological feasibility. The results prove that these WPI-modified nanoparticles perform satisfactorily in conjunction with hyperthermia to cure tumors completely.
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