Development of Multi Field Software Solutions and their Application for the Optimization of Electromagnetic High Speed Forming processes

The simulation of complex processes in engineering solids involving coupled mechanical and non-mechanical fields represents a challenge to physicists, mathematicians, and engineers. Both, the formulation of such models and their numerical implementation involve a great number of difficulties. Electromagnetic forming is one example of such a process, whose modelling and simulation requires a coupled electromagnetic-thermomechanical model. The purpose of this contribution is to discuss some key issues associated with the modelling and simulation of electromagnetic metal forming (EF) and the corresponding development of a finite-element-based simulation tool for EF. In particular, the modelling is based on a thermodynamically-consistent electromagnetic-thermoelastoviscoplastic material and field model in which the energy and momentum balance are coupled to the quasi-static form of Maxwell s equations via the electromotive intensity and Lorentz force, respectively. On the algorithmic side, questions like the choice of meshes, the element formulation, the numerical treatment of nonlinearities, possible model simplifications, different discretisation strategies, realisation of the non-linear coupling etc. are discussed for the presented software solution. Such issues are investigated with the help of benchmark simulations that have been developed for this purpose. Finally, as an example of an application of the developed software tool, a computer aided manufacturing (CAM) problem is considered. Here, the size of the tool coil and the peak value of the current in the tool coil circuit are optimised in order to achieve the prescribed work-piece form within the given tolerance

Validation of Different Approaches to Coupled Electrodynamic-Structural Mechanical Simulation of Electromagnetic Forming

Electromagnetic forming (EF) is a high speed forming process in which strain rates of over 103 s^(-1) are achieved. The workpiece is deformed by the Lorentz force resulting from the interaction of a fast varying electro magnetic field with the eddy currents induced by the field in the workpiece. Within a research group (FOR 443) funded by the German Research Foundation (DFG) an object oriented simulation tool for this multi physical process has been developed (SOFAR), that can handle the fully coupled simulation in a single software environment. In this contribution, details of the algorithmic implementation of the electromagnetic side of the coupled model are discussed and validated. Basis of this validation are benchmark simulations developed for this purpose. In particular, the implementation of transient field computation for coupled problems within SOFAR is compared with an experienced FD-code (FELMEC) developed at the Institute of Electrical Machines, Drives and Power Electronics

Choriocarcinoma in a 73-year-old woman: a case report and review of the literature

<p>Abstract</p> <p>Introduction</p> <p>Choriocarcinoma is a highly malignant tumor of trophoblastic origin. Most cases present within one year of the antecedent pregnancy (molar or non-molar). However, very rarely, choriocarcinoma can develop from germ cells or from dedifferentiation of endometrial carcinoma into choriocarcinoma. This article concerns a case of choriocarcinoma developing 38 years after the patient's last pregnancy and 23 years after menopause.</p> <p>Case presentation</p> <p>A 73-year-old African-American woman presented with a three-week history of vaginal bleeding. A vaginal mass was seen on pelvic examination. Ultrasonography showed a thickened complex endometrial echo. Her β-human chorionic gonadotrophin level was found to be elevated (2,704,040 mIU/mL). Vaginal and uterine biopsies were suggestive of choriocarcinoma. Immunohistochemistry tests were positive for β-human chorionic gonadotrophin as well as cytokeratin and negative for octamer binding transcription factor 3/4 and α-fetoprotein, supporting the diagnosis of choriocarcinoma. A combination of etoposide, methotrexate, and dactinomycin, followed by cyclophosphamide and vincristine (the so-called EMA/CO regimen) was initiated. After seven cycles of chemotherapy, her β-human chorionic gonadotrophin level dropped below 5 mIU/mL. Our patient is being followed up at our oncology institute.</p> <p>Conclusions</p> <p>We report an extremely rare case of choriocarcinoma arising 23 years after menopause. A postmenopausal woman presenting with vaginal bleed from a mass and β-human chorionic gonadotrophin elevation should be evaluated by immunohistochemical analysis to rule out the possibilities of a germ cell origin of the tumor or dedifferentiation of an epithelial tumor. Absence of octamer binding transcription factor 3/4, α-fetoprotein and CD-30 staining helps in exclusion of most germ cell tumors. DNA polymorphism studies can be used to differentiate between gestational and non-gestational tumor origin. These require fresh tissue samples and are time consuming. Finally, the effective first-line therapy for β-human chorionic gonadotrophin-producing high-risk gestational as well as non-gestational trophoblastic tumors is combination chemotherapy (the EMA/CO regimen). Therefore, treatment should be commenced when a potential diagnosis of metastatic trophoblastic tumor is being considered.</p