Plastic instability in complex strain paths predicted by advanced constitutive equations

The present paper aims at predicting plastic instabilities under complex loading histories using an advanced sheet metal forming limit model. The onset of localized necking is computed using the Marciniak-Kuczinslcy (MK) analysis [I] with a physically-based hardening model and the phenomenological anisotropic yield criterion Yld2000-2d [2]. The hardening model accounts for anisotropic work-hardening induced by the microstructural evolution at large strains, which was proposed by Teodosiu and Hu [3]. Simulations are carried out for linear and complex strain paths. Experimentally, two deep-drawing quality sheet metals are selected: a bake-hardening steel (BH) and a DC06 steel sheet. The validity of the model is assessed by comparing the predicted and experimental forming limits. The remarkable accuracy of the developed software to predict the forming limits under linear and non-linear strain path is obviously due to the performance of the advanced constitutive equations to describe with great detail the material behavior. The effect of strain-induced anisotropy on formability evolution under strain path changes, as predicted by the microstructural hardening model, is particularly well captured by the model.open1134Nsciescopu

Development and analysis of train brake curve calculation methods with complex simulation

This paper describes an efficient method using simulation for developing and analyzing train brake curve calculation methods for the on-board computer of the ETCS system. An application example with actual measurements is also presented

Onsagerian Quantum Mechanics

We describe the basic quantum-mechanical categories and properties of the thermodynamical basis of Onsagers theorem. 3 basic principles are used: 1. energy dissipation; 2. Hamiltonian formalism; 3. Onsagers linearity. We obtain the 2 characteristic values of the observables, their main-value and the deviation, the first and second momentums of the probability distribution function, which we also derived also from the same principles

The performance of Marciniak–Kuczinsky approach on prediction of plastic instability of metals subjected to complex loadings

The objective of the present paper is to analyse the performance of Marciniak-Kuczinsky (MK) theory on the prediction of formability of sheet metals subjected to complex loadings. Advanced constitutive equations taking into account isotropic and anisotropic hardening are applied to describe the material mechanical behaviour under linear and complex loadings. A comparative study on their accuracy on predicting the forming limits for the studied material is performed. Two deep-drawing quality sheet metals are selected. Several strain path changes are taken into account. A good agreement between the theoretical and experimental results was obtained. MK theory is an efficient and valuable tool on the prediction of plastic flow localization of sheet metals under complex loadings when proper constitutive equations are used.publishe

The formability prediction of twinning-induced plasticity steels

The proposal of this work is to predict and analyse the formability of twinning-induced plasticity steels through the Marciniak-Kuczinsky approach with emphasis on the solutions for improving the prediction results. The selected constitutive equations involve the Yld2000-2d plane stress yield function and the Swift strain-hardening power law. To understand the formability of the TWIP steel and the factors influencing it, a sensitive study on the effect of the mechanical properties of the TWIP steel on the Marciniak-Kuczinsky (MK) theory concept and the predicted forming limits is performed.publishe

Mechanical behaviour of TWIP steel under shear loading

Twinning induced plasticity steels (TWIP) are very good candidate for automotive industry applications because they potentially offer large energy absorption before failure due to their exceptional strain hardening capability and high strength. However, their behaviour is drastically influenced by the loading conditions. In this work, the mechanical behaviour of a TWIP steel sheet sample was investigated at room temperature under monotonic and reverse simple shear loading. It was shown that all the expected features of load reversal such as Bauschinger effect, transient strain hardening with high rate and permanent softening, depend on the prestrain level. This is in agreement with the fact that these effects, which occur during reloading, are related to the rearrangement of the dislocation structure induced during the pre-deformation. The homogeneous anisotropic hardening (HAH) approach proposed by Barlat et al. (2011) [1] was successfully employed to predict the experimental results.110Ysciescopu

A study and experiment plan for digital mobile communication via satellite

The viability of mobile communications is examined within the context of a frequency division multiple access, single channel per carrier satellite system emphasizing digital techniques to serve a large population of users. The intent is to provide the mobile users with a grade of service consistant with the requirements for remote, rural (perhaps emergency) voice communications, but which approaches toll quality speech. A traffic model is derived on which to base the determination of the required maximum number of satellite channels to provide the anticipated level of service. Various voice digitalization and digital modulation schemes are reviewed along with a general link analysis of the mobile system. Demand assignment multiple access considerations and analysis tradeoffs are presented. Finally, a completed configuration is described

The third transitional Identity of migrant adolescents. The case of Hotel House an Italian multi-ethnic skyscraper-ghetto

The adolescent\u2019s identity achievement is a complex task, even more so if they are migrants living in a particular context of ethnic ghettoization. Hotel House is an enormous, isolated condominium situated on the outskirts of Porto Recanati, a small Italian town. It is a unique reality poorly studied from a social psychological perspective. The present paper aims to measure the perceived levels of self-concept clarity, self-determination, ethnic group identification, relationship with parents, depression and life satisfaction in a group of 91 adolescents (11\u201319 years; 30% females; 1.5 immigrant\u2019s generation) living in this context. The analysis shows low levels of self-concept clarity and self-determination, especially in female adolescents, quite satisfactory relationships with their parents and medium levels of group identification and life satisfaction. The identification with their ethnic subgroups seems to provide a third transitional identity which works as a temporary link between native country values and host country values. The regression analysis shows significant associations: self-determination is negatively associated with depression and positively associated with the perception of life satisfaction; the father\u2019s closeness is a negative predictor for depression and a positive predictor for life satisfaction; mother\u2019s closeness is negatively associated with depression