Search results for "STIR"

Influence of material characteristics on plastomechanics of the fsw process for T-joints

2009

Abstract The potential of friction stir welding (FSW) has thoroughly been investigated by several authors, however their focus has primarily been on butt joints. T-joints are of paramount interest for transportation industries especially due to their capacity to straighten panels. Welding of T-joints is very challenging due to thin walls, poor location of the rib–web interface and the requirements for corner-fillets. This paper investigates FSW of T-joints of two popular aluminum alloys, i.e. 2024-T4 and 6082-T6, and the role played by the material characteristics on joining. First, an experimental study is carried out with specially designed fixture to determine the effect of process condi…

Modeling of the Plastic Characteristics of AA6082 for the Friction Stir Welding Process

2015

Focus of this paper is to model the plastic forming behavior of AA6082, in order to develop the numerical FE analysis of the friction stir welding processes and the simulation of subsequent forming processes. During the friction stir welding process, the temperatures reached are until 500 °C and have a fundamental role for the correct performance of the process so the material data has to show a temperature dependency. Because of the tool rotation a strain rate sensitivity of the material has to be respected as well. In this context, the general material characteristics of AA6082 were first identified for different stress states. For the uniaxial state the standard PuD-Al used in the automo…

FEM based prediction of phase transformations during Friction Stir Welding of Ti6Al4V titanium alloy

2013

Abstract Friction Stir Welding (FSW) is a solid state welding process patented in 1991 by TWI; initially adopted to weld aluminum alloys, it is now being successfully used also for high resistant materials. Welding of titanium alloys by traditional fusion welding techniques presents several difficulties due to high material reactivity with oxygen, hydrogen, and nitrogen with consequent embrittlement of the joint. In this way FSW represents a cost effective and high quality solution. The final mechanical properties of the joints are strictly connected to the microstructural evolutions, in terms of phase change, occurring during the process. In the paper a 3D FEM model of the FSW welding proc…

Sul Miglioramento della Processabilità del Nanocomposito a base di Polistirene Sindiotattico e Argille Modificate

2004

Sul Miglioramento della Processabilità del Nanocomposito a base di Polistirene Sindiotattico e Argille Modificate

Influence of activated carbon on performance and microbial communities in the treatment of solvent pollutant mixtures in a continuous stirred tank re…

2020

The influence of the addition of granular activated carbon (GAC) on the anaerobic treatment of wastewater with a mixture of ethanol and 1-ethoxy-2-propanol (E2P), which are typical pollutants from the flexographic/printing industry, was evaluated. For this purpose, the reactor performance and microbial community in two continuous stirred tank reactors (CSTRs), i.e. control and GAC supplemented, were assessed. Both reactors, seeded with anaerobic granular biomass, showed similar global performance (RE > 93%), except after organic load shocks and after E2P addition. GAC supplementation substantially enhanced the response of the biological system to organic load shocks and reduced the acclimat…

On the Reduction of Power Consumption in Vortexing Unbaffled Bioslurry Reactors

2020

Bioremediation of polluted soils via bioslurry reactors is an interesting option among those available nowadays, especially when recalcitrant pollutants are present. Vortexing unbaffled stirred tanks may be a valuable choice to this purpose as they were recently found to be more efficient than baffled vessels for solid suspension processes where mixing time is not a controlling factor. When operated at sufficiently high agitation speeds, the central vortex bottom reaches the impeller and air bubbles start to be distributed throughout the system, thus avoiding any sparger and related clogging issues. In the present work, a vortexing unbaffled stirred tank with solid loadings ranging from 2.5…

Matrix algebras with degenerate traces and trace identities

2022

In this paper we study matrix algebras with a degenerate trace in the framework of the theory of polynomial identities. The first part is devoted to the study of the algebra $D_n$ of $n \times n$ diagonal matrices. We prove that, in case of a degenerate trace, all its trace identities follow by the commutativity law and by pure trace identities. Moreover we relate the trace identities of $D_{n+1}$ endowed with a degenerate trace, to those of $D_n$ with the corresponding trace. This allows us to determine the generators of the trace T-ideal of $D_3$. In the second part we study commutative subalgebras of $M_k(F)$, denoted by $C_k$ of the type $F + J$ that can be endowed with the so-called st…

An Innovative Friction Stir Welding Based Technique to Produce Dissimilar Light Alloys to Thermoplastic Matrix Composite Joints

2016

Abstract Aluminum sheets can be joined to composite materials with different techniques. Each of them has advantages and weak points over the others. In literature, new techniques and patents are continuously developed to overcome these difficulties. In the paper a new Friction Stir Welding based approach is proposed to mechanically join AA6082-T6 to self-reinforced polypropylene. The aluminum sheet is pre-holed along both the sides of the weld line. A pinless tool generates the heat and pressure needed to activate back-extrusion of the composite. Joints have been produced with varying hole diameter and pitch. The mechanical resistance of the joint has been evaluated and the different failu…

Työelämän ristiriitainen kuva ja työelämän tutkimus

2003

On the thermo-mechanical loads and the resultant residual stresses in friction stir processing operations

2008

In friction stir welding and processing both a thermal flux and a mechanical action are exerted on the material determining metallurgical evolutions, changes in the mechanical behaviour and a complex residual stress state. In the paper, the metallurgical changes are examined through numerical simulation and experiments to highlight and distinguish the effects of thermal and mechanical loadings. A particular focus is made on the residual stresses generated during the stir processing of AA7075-T6 aluminium blanks. The predictions of FE model are validated by experimental measurements. Lastly, this paper presents an in-process quenching of the processed blanks for improved mechanical propertie…