An overview of welding in solid state

The importance of the Solid State Processes (SSP) has increased in the last decade due to the industry demands of improved properties of joined/surfaced materials, combined with cost reduction and energy saving. New and/or micro-scale solid state processed materials are used by aerospace, automotive and electrotechnics industry. Nowadays, classic SSP are mainly applied to light materials, but progresses were also reported in steels. In this field, the tools design, the technology and practical techniques surpassed the fundamental approach of the materials solid state processing. The SSP parameters evaluation is based on different experiments, approaching the material flow in the large plastic deformation domain. The paper approaches the solid state welding/joining and surface processing. The envisaged SSP are solid state joining processes as Cold Welding (butt and spot welding), Friction Stir Welding – FSW, and surface processing, Friction Stir Processing - FSP. Therefore, the investigation targeted the deformation and flow pattern of the parent metal in case of cold welding and FSW/FSP, processes parameters evaluation and correlation, local analysis of the material structural transformations, and material hardening

Welding in solid state

The importance of the Solid State Processes (SSP) has increased in the last decade due to the industry demands of improved properties of joined/surfaced materials, combined with cost reduction and energy saving. New and/or micro-scale solid state processed materials are used by aerospace, automotive and electrotechnics industry. Nowadays, classic SSP are mainly applied to light materials, but progresses were also reported in steels. In this field, the tools design, the technology and practical techniques surpassed the fundamental approach of the materials solid state processing. The SSP parameters evaluation is based on different experiments, approaching the material flow in the large plastic deformation domain. The paper approaches the solid state welding/joining and surface processing. The envisaged SSP are solid state joining processes as Cold Welding (butt and spot welding), Friction Stir Welding – FSW, and surface processing, Friction Stir Processing - FSP. Therefore, the investigation targeted the deformation and flow pattern of the parent metal in case of cold welding and FSW/FSP, processes parameters evaluation and correlation, local analysis of the material structural transformations, and material hardening

Analytical models for temperature prediction on welding

Temperature field has an important influence on the phase changes and, finally, on the microstructure and mechanical properties, residual stresses and strains development in the welded joints. During the welding, temperature field shape and its profile depend on many factors but, assuming some assumptions regarding homogeneity and materials isotropy, the mathematical relations for different practical cases can be obtained. Besides, welded bodies can be infinite or semi-infinite as the plates, bars and massive bodies are considered. The instantaneous or permanent thermal sources, fixed or mobile have an important influence on the temperatures distribution. Therefore, the paper presents some analytical solutions for the temperatures prediction in the welded joints in case of the mobile sources with 2D and 3D Gauss distribution

Modification of Materials Local Properties by Friction Stir Processing

Friction stir processing (FSP) is a new solid state processing technique that can eliminate casting defects and refine microstructures, enhancing formability and improving other properties. FSP can also produce fine-grained microstructures through thickness. Essentially, FSP is a local thermo-mechanical metal working process that changes the local properties without influencing the properties of the bulk material. Firstly, the paper introduces FSP fundamental parameters, as advancing and rotating tool speed, approaching their influence on the processed surface roughness of Al6061. Single and overlapped friction stir processed layers were considered for the roughness analysis. Roughness mapping revealed existence of transitory and quasi-stationary phases of FSP. A process monitoring method obtaining through roughness control is envisaged. The paper also presents the material flow, microstructure and hardness in case of aluminium processed by FSP

Quality Of The Vocational Training For Construction Inspectors

The paper addresses the quality of the continuing training and vocational education for the construction inspector job and the harmonized European recognition of this qualification. It is the result of a survey realized in 5 EU countries (Greece, Hungary, Poland, Portugal and Romania) within the fame of the project entitled “Analysis and Comparative Study on construction inspection job performance regulations. European comparative study – KNOWLEDGE”. The general objective was to give recommendations for improving the qualification of civil construction inspectors by identifying the gap between the existing vocational education / training systems, and people/companies’ expectations and needs, as resulted from current literature, in-depth interviews and questionnaire surveys. The conclusions are related to the necessity of developing a training/certification program for the construction inspector, the magnitude and European dimension of such training and certification program, and the thematic areas that the program will cover to meet the construction industry requirements. Courses approaching New Construction Materials, Quality Control Procedures, Legislation on Town Planning, Private Constructions and Public Works, Legislation on Safety Issues in the Construction Industry, and the EU directives were identified as being necessary for updating the knowledge of the construction inspectors. Relevant graphs presenting the continuing training needs of the construction inspectors resulted from the in-depth interviews are presented. It results as a LLL European policy requisite the development of a European Certification for construction inspector

Arc welding of Dissimilar Metals:FEA and Experiments

Assuming an elliptical disk heat source, several results of theoretical and experimental investigations on heat transfer in copper - low carbon steel welded joints are presented in the first part of the paper. Using thin sheets, temperature variation in the thickness direction is negligible and heat flow is considered two-dimensional. Convection and radiation influence, and thermo-physical properties depending on the temperature are considered in the model. Measurements and visualization of the temperatures distribution have been made during welding using infrared thermography. The proposed theoretical method using finite element analysis was validated for the temperatures prediction in the welded joint. In the second part of the paper, the influence of the welding process on the structural modifications and grains’ size in the heat affected zone (HAZ) of both base materials (BM) is described. Discussion on the graphs of temperatures variation vs. microstructural analysis enables conclusions on the potential undesired structural changes and related preventing measures. The asymmetric position of the heat source closer to the material having a higher thermal conductivity is an effective method for controlling the temperature field

Naval propellers reconditioning by Friction stir welding ¿ FSW

The naval propeller is subjected to high cycling fatigue loadings and shocks. Besides, working in corrosive medium, cracks and, finally, fractures could be developed in different regions of the propeller. Because the zones of the propeller don’t work in similar conditions, the damage is not the same in all regions. The paper presents considerations about alloys for naval propellers, working conditions, wear and failure, reconditioning and testing of the naval propellers

Residual stress analysis of friction stir processed AA6061

Currently, after appropriate heat treatments, the 6xxx aluminium alloys are used in a variety of applications including aircraft fuselage skins and automobile body panels and bumpers, instead of more expensive 2xxx or 7xxx alloys. The paper presents the results of the residual stress analysis in case of Friction Stir Processing - FSP of AA6061-T4 plates, 10 mm thickness, demonstrating the process ability to locally modify the base metal properties. The residual stresses, DRX depicted, are correlated with the microstructure and hardness results

Evaluation of carbon monoxide and microparticles concentrations generated during MAG-C welding process

Tijekom zavarivanja, dodatna žica za zavarivanje i zaštitni plin dovode do stvaranja zagađivača opasnih po zdravlje zavarivača. Istraživanje je usmjereno na kvantitativnu procjenu koncentracije ugljičnog monoksida (CO) i mikročestica kao posljedica MAG-C (Metal Active Gas-CO2) zavarivanja u različitim uvjetima postupka. Sedam dodatnih žica za zavarivanje – ouobičajena puna žica, osnovna, bazična žica s praškom za zavarivanje u jezgri, tri žice od rutila s praškom za zavarivanje u jezgri i dvije žice od rutila s praškom za zavarivanje u jezgri niskog isparavanja – izabrane su za istraživanje i komparativnu analizu zagađivača razvijenih otapanjem tih žica položenih zavarivanjem na EH36 čelične limove za brodogradilišta. Primjenjujući uzastopno tri vrijednosti brzine posmaka dobivena su dvadeset i jedan šavna zavara pri horizontalnom položaju zavarivanja unutar specijalne hermetički nepropusne komore. Koncentracije CO i mikročestica dobivene su posebnim uređajima - Multilyzer NG za plinove i MicroDust Pro za mikročestice – koje su se zatim obrađivale i o njima vodile komparativne rasprave. Mjerenje veličine čestica i detaljna rasprava provedeni su primjenom SEM analize. Slike dobivene pomoću SEMa pokazale su tvorbu amorfnih struktura i čestica nano i mikroveličina s promjerom od 641,1 nm do 8,92 μm. Istraživanja su pokazala da su najniže koncentracije CO i mikročestica dobivene kad su se koristile pune i žice od rutila s praškom za zavarivanje u jezgri niskog isparavanja.During the welding process, the filler wire - shielding gas couple generates the formation of pollutants which are dangerous for the welder\u27s health. The research focussed on the quantitative evaluation of carbon monoxide (CO) and microparticles concentrations produced in MAG-C (Metal Active Gas-CO2) welding in various process conditions. Seven welding filler wires - one common solid wire, one basic flux-cored wire, three rutile flux-cored wires and two low fume rutile flux-cored wires- were selected for the investigation and comparative analysis of the pollutants developed by melting of these wires which were deposited by welding on EH36 shipbuilding steel sheets. Applying consecutively three feed rate values, twenty-one seam welds were performed in welding horizontal position within a special hermetically air-tight chamber. Concentrations of CO and microparticles were acquired through special devices - Multilyzer NG of gases and MicroDust Pro for microparticles - and then were processed and comparatively discussed. Using SEM analysis, measurement of particles\u27 size was made and discussed in detail. The images obtained by SEM illustrated the formation of amorphous structures and also nano and micro-sized particles with diameters from 641,1 nm to 8,92 μm. The investigations revealed that the lowest concentrations of CO and microparticles were produced when solid and low fume rutile flux-cored wires were used in the deposition welding

CoRoLa Starts Blooming – An update on the Reference Corpus of Contemporary Romanian Language

This article reports on the on-going CoRoLa project, aiming at creating a reference corpus of contemporary Romanian (from 1945 onwards), opened for online free exploitation by researchers in linguistics and language processing, teachers of Romanian, students. We invest serious efforts in persuading large publishing houses and other owners of IPR on relevant language data to join us and contribute the project with selections of their text and speech repositories. The CoRoLa project is coordinated by two Computer Science institutes of the Romanian Academy, but enjoys cooperation of and consulting from professional linguists from other institutes of the Romanian Academy. We foresee a written component of the corpus of more than 500 million word forms, and a speech component of about 300 hours of recordings. The entire collection of texts (covering all functional styles of the language) will be pre-processed and annotated at several levels, and also documented with standardized metadata. The pre-processing includes cleaning the data and harmonising the diacritics, sentence splitting and tokenization. Annotation will include morpho-lexical tagging and lemmatization in the first stage, followed by syntactic, semantic and discourse annotation in a later stage