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Finite-element simulation of ultrasound brain surgery: effects of frequency, focal pressure, and scanning path in bone-heating reduction

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Behnia S., Jafari A., Ghalichi F., Bonabi A.
Open Physics
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2008
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vol. 6
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issue 2
211-222
EN
In this paper, the finite-element method (FEM) simulation of ultrasound brain surgery is presented. The overheating problem of the post-target bone, which is one of the limiting factors for a successful ultrasound brain surgery, is considered. In order to decrease bone heating, precise choices of frequency, focal pressure, and scanning path are needed. The effect of variations in the mentioned scanning parameters is studied by means of the FEM. The resulting pressure and temperature distributions of a transdural ultrasound brain surgery are simulated by employing the FEM for solving the Helmholtz and bioheat equations in the context of a two-dimensional MRI-based brain model. Our results show that for a suitable value of the frequency, an increase in focal pressure leads to a decrease in the required duration of the treatment and is associated with less heating of the surrounding normal tissue. In addition, it is shown that at a threshold focal pressure, the target temperature reaches toxic levels whereas the temperature rise in the bone is minimal. Wave reflections from sinus cavities, which result in constructive interference with the incoming waves, are one of the reasons for overheating of the bone and can be avoided by choosing a suitable scanning path.
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Investigation of the Crash Boxes Light Weighting with Syntactic Foams by the Finite Element Analysis

100%
Özer H., Can Y., Yazıcı M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
734-737
EN
Light-weighting is a new scope in the automotive industry to accommodate new emission regulations. The parts produced with conventional metallic materials are replaced with parts produced by using light weight or high strength materials, to obtain light weighted equivalents of the same strength. Foam core sandwich structures, high strength steels, composite materials are the most used alternative materials. Syntactic foams that show outstanding performance in case of high-speed collisions have an excellent utility as energy absorbers in vehicle crash boxes. Syntactic foams are modeled in crash boxes at various filling rates and filling patterns in the context of this study. As results of the FEM analyses, it is observed that syntactic foams have excellent crash performance, as well as weight-reducing effect in vehicle crash boxes.
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Influence of Press Ram Pulsation on Deep Drawability of Dual Phase Steel Sheet

100%
Olguner S., Tolga Bozdana A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
742-745
EN
A study of the influences of press ram pulsation on deep drawability of dual phase steel sheet is presented. General characteristics of deep drawing process, press ram pulsation technique and dual phase steels are briefly discussed. A finite element model is used to evaluate the influence of pulse motion profile of press ram on the thickness reduction of steel sheet and forming load. Commercial finite element software package DEFORM-3D is used for modelling and simulation of cylindrical cup drawing. The effects of superimposed low frequency vibrations of the press ram are investigated. Pulsation amplitudes of 0.5, 0.25, and 0.125 mm are created on the die with the corresponding pulsation frequencies of 5, 10, and 20 Hz. Finite element simulations are carried out using material model of dual phase (DP600) steel, that is one of the most widely used materials in automobile industry, in order to improve crash safety and fuel economy. Results obtained with press ram pulsation are compared with results for the conventional press ram motion and significant effect of proposed method is demonstrated.
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