Welding current prediction in GMAW and UGMAW processes using response surface methodology

Abstract

Among all process variables in gas metal arc welding (GMAW) process, welding current is the most influential variable affecting heat input and weld quality. Its dependence on other process variables in GMAW and universal gas metal arc welding (UGMAW) processes (which makes use of a specially designed torch to preheat the filler wire independently, before its emergence from the torch) has been investigated using four factor five level central composite rotatable design to develop relationship for predicting welding current, which enables to quantify the direct and interactive effects of four numeric factors, namely wire feedrate, open circuit voltage, welding speed and electrode stickout and one categorical factor preheat current. Mathematical models developed show that welding current increased linearly with increaseing wire feedrate and open circuit voltage, whereas it decreased with increasing electrode stickout and preheat current. Numerical optimisation was carried out, and the optimal solutions generated indicate that under the same input conditions higher deposition rates are achievable in UGMAW process.     

Surface coatings in tribological and wearresistant applications

Abstract

Surface engineering has become a key technology in advanced applications in recent decades, offering materials surfaces with special physical, chemical or mechanical properties. Several new processing techniques have been developed, some of which are successfully applied industrially, for example to allow surface design and manufacture of wear-resistant mechanical parts. To illuminate understanding of surface engineering in tribological applications, a detailed review of surface coating technologies in tribological and wear-resistant applications is presented.     

Trends of composite casting technology and joining technology for castings in Japan

Abstract

State of technologies in Japan related to composite casting was reviewed based on the three year survey of Composite Casting Process Sub-Committee in Committee on Foundry Technology (24th) of JSPS. Other than making metal matrix composite, cast-in insertion, bonding and joining of cast materials and other technologies combining different materials by casting process were included. Basic theories and the key technologies are explained, and a number of typical examples of products, on production or on experimental bases, were reported. Overseas literatures were also surveyed.     

Improved FE model for simulation of friction stir welding of different materials

Abstract

One of the most relevant aspects of friction stir welding is the possibility to weld different materials. In the present paper, the authors present an improved continuum finite element model for the simulation of friction stir welding processes aimed to obtain T joints, made of a stringer in AA7175-T73511 and of a skin in AA2024-T4. The model, taking into account the thermomechanical behaviours of the two different materials, is utilised to study the occurring material flow and residual stress state. Numerical results are compared with experimental observations: the model is able to predict the material flow, obtaining important information on the joint failure mode.     

Guest Editorial: Personal perspective on microstructure of steels: 25th anniversary of MST and collection of papers in honour of Sir Robert Honeycombe

Abstract

The shape memory properties and microstructure associated with γ(fcc) → ?(hcp) martensitic transformation in an Fe–14Ru alloy have been investigated. The degree of shape recovery was measured via a bending test, and the microstructure was examined using X-ray diffractometry, optical microscopy, and transmission electron microscopy. The Fe–14Ru alloy showed shape recovery to some extent, but to a lower degree than in Fe–Mn–Si based shape memory alloys. The lower strength of the matrix, the presence of ? and α′ martensites at room temperature, and the higher stacking fault energy in the Fe–14Ru alloy are thought to be responsible for the weaker shape memory effect.     

Evaluation of airliner cabin textile materials after vapour phase hydrogen peroxide decontamination

Abstract

Decontamination of airliner cabins may be required, for example, in the event of an epidemic or pandemic. To be performed safely, decontamination must be compatible with aircraft materials and systems. This paper examines the suitability, with respect to cabin textiles, of vapour phase hydrogen peroxide for airliner decontamination applications. The effect of vapour phase and liquid hydrogen peroxide on common airliner interior textile materials, namely wool, nylon, polyester, and Nomex, has been studied by examining the physical and chemical changes and the resulting effect on mechanical properties caused by decontamination. The physical changes induced by the sorption of moisture had an effect on the mechanical properties of all of the materials examined. However, only wool attacked chemically by hydrogen peroxide experience a significant effect on its mechanical properties.     

Tensile stress–strain and work hardening behaviour of 316LN austenitic stainless steel

Abstract

The true stress (σ)–true plastic strain (?) data of a type 316LN austenitic stainless steel tested at nominal strain rates in the range 3×10^-5–3×10^-3 s^-1 and temperatures of 300–1123 K were analysed in terms of flow relationships proposed by Hollomon, Ludwik, Swift, Voce, and Ludwigson. The applicability of the particular flow relationship is discussed in terms of ‘complete’ and ‘applicable’ range fits of the experimental σ–? data. At all strain rates, in the case of the complete range fit, the Ludwigson equation followed the stress–strain data most closely at 300 K, while in the temperature range 523–773 K, the flow behaviour was described equally well by both the Ludwigson and Voce equations. In the temperature range 823–1023 K, the Voce equation described the flow behaviour most accurately in the case of the complete range fit of σ–? data at all strain rates. The analysis of σ–? data employing the Ludwigson equation in the applicable range fit covering low and intermediate strains, and the Hollomon equation at high strains provided close simulation of the observed flow behaviour in the temperature range 823–1023 K. At high temperatures of 1073 and 1123 K, the Ludwigson equation reduces to the Hollomon equation. The variations in different flow parameters of the Ludwigson and Voce equations with temperature and strain rate exhibited anomalous behaviour at intermediate temperatures because of dynamic strain aging.     

Performance of neural networks in materials science

Abstract

Neural networks are now a prominent feature of materials science with rapid progress in all sectors of the subject. It is premature, however, to claim that the method is established. There are genuine difficulties caused by the often incomplete exploration and publication of models. The assessment presented here is an attempt to compile a loose set of guidelines for maximising the impact of any models that are created, in order to encourage thoroughness in publication to a point where the work can be independently verified.     

Preparation of nanostructured CeO2 coated TiO2

Abstract

The synthesis of nanostructured TiO₂ and nanostructured CeO₂ coated TiO₂ has been investigated. On the basis of the synthesis of nano-TiO₂, nano-CeO₂ coated TiO₂ was prepared by use of sol- gel technology. X-ray diffraction, TEM, and high resolution electron microscopy were employed to analyse the characteristics and microstructures of the synthesised materials. The TEM analysis indicated that nano-CeO₂ coated TiO₂ is formed of agglomerated particles with an average size of 70 nm with the TiO₂ located at the centre surrounded by nanostructured CeO₂ polycrystals. Owing to the catalytic effect of nano-CeO₂, the oxygen sensitivity of nano-CeO₂ coated TiO₂ was better than that of pure nano-TiO₂.     

Processing parameters for the mechanical working of 9 Cr–1 Mo steel: processing maps approach

Abstract

Processing and instability maps using a dynamic materials model have been developed for 9Cr–1Mo steel in the temperature range 850 to 1200°C and strain rate range 0.001–100 s^–1 with a view to optimising its hot workability. The efficiency of power dissipation increased with increase in temperature and decrease in strain rate. The 9Cr–1Mo material exhibited two dynamic recrystallisation domains, one with a peak efficiency of 37% occurring at 950°C and 0.001 s^–1 and the other with a peak efficiency of 35% occurring at 1200°C and 0.1 s^–1. These results are in good agreement with those found in industry.