Experimental and numerical analysis of the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles

In this work, an experimental and numerical analysis of the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is conducted. Experiments are performed using a pneumatic gas gun for with the impact velocities in the range of 35 m/s < V-0 < 200 m/s. Two target thicknesses are examined, t(1) = 0.5 mm and t(2) = 1.0 mm. The experimental setup enabled the determination of the impact velocity, the residual velocity and the failure mode of the steel sheets. The effect of the projectile nose shape on the target's capacity for energy absorption is evaluated. Moreover, martensite is detected in all the impacted samples, and the role played by the projectile nose shape on the transformation is highlighted. A three-dimensional model is developed in ABAQUS/Explicit to simulate the perforation tests. The material is defined via the constitutive model developed by Zaera et al. (2012) to describe the strain-induced martensitic transformation occurring in metastable austenitic steels at high strain rates. The finite element results are compared with the experimental evidence, and satisfactory matching is observed over the entire range of impact velocities tested and for both projectile configurations and target thicknesses considered. The numerical model succeeds in describing the perforation mechanisms associated with each projectile-target configuration analyzed. The roles played by impact velocity, target thickness and projectile nose shape on the martensitic transformation are properly captured.The researchers of the University Carlos III of Madrid are in debted to the Comunidad Autónoma de Madrid (Project CCG10 UC3M/DPI 5596) and to the Ministerio de Ciencia e Innovación de España (DPI2011 24068) for the financial support received which allowed conducting part of this work

Resonator-based detection in nanorods

In this paper the axial vibrational behaviour of nanorods with an attached point-mass is studied, using the modified strain energy theory. The natural frequencies of the nanorod with the concentrated mass are obtained for different boundary conditions. The effects of the concentrated mass intensity, mass location, as well as the value of scale parameters have been analysed. For the case of small intensity of the concentrated mass, the natural frequencies of the nanorod can be estimated using a first order perturbative solution. These approximate results are compared with those corresponding to the exact solution. For this case, from the properties of the eigenvalue perturbative theory, the identification of single point mass in uniform nanorods (mass intensity and position) is addressed. The results obtained encourage the use of axial vibrations of nanorods as a very precise sensing technique

ZnO growth by MOCVD: numerical study

EnIII&#8722;V compound device fabrication is facing today challenging issues typically related to high volume manufacturing such as process reliability, process consistency, cost&#8722;reduction. Each step of the overall device manufacturing process must be carefully analysed and replicated to obtain reproducible device structures. Purifiers are commonly used in MOVPE processes and are becoming standard equipment in both research and production environments. In most cases implementation of gas purification strategies is enabling to achieve ultimate product purity and process reproducibility by defect and contamination control. In addition, an appropriate gas purification strategy is effective in high value component/chemicals protection (e.g. high purity MO sources), and as an assurance against line contamination due to human error or component failure. Purifier operating conditions can vary noticeably and a knowledge of which parameters can affect ultimate gas purity should be of interest to MOVPE operators to master gas distribution line contamination issues. Expertise on such parameters and their effect is essential to obtain a reliable product and sub&#8722;ppb contamination control throughout the purifier's lifetime and not only in spot demonstrations

Environmental development of the Spanish ceramic tile manufacturing sector over the period 1992–2007

The Spanish tile manufacturing sector has grown steadily over the years covered by the three benchmark studies, carried out in 1992, 2001, and 2007, from which data are compared in this paper. In that period, production output doubled, although since the last study was published, the situation has undergone a radical change and current production output stands at a level similar to that of 1995. Nevertheless, despite the world economic crisis, which has also severely impacted the ceramic wall and floor tile sector, it is worth noting that the sector’s environmental parameters have demonstrated a constant and positive trend, both in companies’ individual environmental performance and in the actual manufacturing processes itself. To a large extent, this situation was forced upon the sector as it had to adapt to numerous environmental regulations, which in general terms call for harsher and more stringent conditions than before. In this sense, the adoption of IPPC regulations, which affect practically the entire ceramic tile sector, and the approval of EU Directive 2003/87 establishing a scheme for greenhouse gas emission allowance trading were significant factor

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous sem inal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austen itic steels submitted to impact conditions. Regarding most of the works reported in the lit erature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10 UC3M/DPI 5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008 06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates.Publicad

Development and status of protection functions for the normal conducting LINAC at ESS

The European Spallation Source faces a great challenge in succeeding with its ambitious availability goals. The aim is to construct a machine that allows for 95% availability for neutron beam production. This goal requires a robust protection system that allows for high availability by continuously monitoring and acting on the machine states, in order to avoid long facility downtimes and optimize the operation at any stage. The normal conducting section consists of the first 48 meters of the machine, and performs the initial acceleration, bunching, steering, and focusing of the beam, which sets it up for optimal transition into the superconducting section. Through a fit-for-purpose risk management process, a set of protection functions has been identified. The risk identification, analysis, and treatment were done in compliance with modern safety and ISO standards. This ensures that the risks, in this case downtime and equipment damage, are properly prevented and mitigated. This paper describes this process of defining the protection functions for the normal conducting LINAC at ESS