Modelling the influence of the process inputs on the removal of surface contaminants from Ti-6Al-4V linear friction welds

The linear friction welding (LFW) process is finding increasing interest from industry for the fabrication of near-net-shape, titanium alloy Ti–6Al–4V, aerospace components. Currently, the removal of surface contaminants, such as oxides and foreign particles, from the weld interface into the flash is not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. The key findings showed that the welds made with higher applied forces required less burn-off to completely remove the surface contaminants from the interface into the flash; the interface temperature increased as the applied force was decreased or the rubbing velocity increased; and the boundary temperature between the rapid flash formation and negligible material flow was approximately 970 °C. An understanding of these phenomena is of particular interest for the industrialisation of near-net-shape titanium alloy aerospace components.EPSRC, Boeing Company, Welding Institut

Modelling of the workpiece geometry effects on Ti–6Al–4V linear friction welds

Linear friction welding (LFW) is a solid-state joining process that is finding increasing interest from industry for the fabrication of titanium alloy (Ti–6Al–4V) preforms. Currently, the effects of the workpiece geometry on the thermal fields, material flow and interface contaminant removal during processing are not fully understood. To address this problem, two-dimensional (2D) computational models were developed using the finite element analysis (FEA) software DEFORM and validated with experiments. A key finding was that the width of the workpieces in the direction of oscillation (in-plane width) had a much greater effect on the experimental weld outputs than the cross-sectional area. According to the validated models, a decrease of the in-plane width increased the burn-off rate whilst decreasing the interface temperature, TMAZ thickness and the burn-off required to remove the interface contaminants from the weld into the flash. Furthermore, the experimental weld interface consisted of a Widmanstätten microstructure, which became finer as the in-plane width was reduced. These findings have significant, practical benefits and may aid industrialisation of the LFW process.The authors would like to thank the Engineering and Physical Sciences Research Council (EPSRC), The Boeing Company and The Welding Institute (TWI) for funding the research presented in this paper

Wire + Arc Additive Manufacturing

Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed

Alex Wiseman: reluctant architect?

The Auckland Ferry Building, completed in 1912, is still a significant landmark in downtown Auckland today. However, its architect, Alex Wiseman, remains less well-known and more enigmatic. Born in Auckland in 1865 into a prominent Methodist family, Wiseman was apprenticed at 16 years of age to noted architect Edward Bartley for a term of four years. Wiseman then practised as a draughtsman for a period, before moving to Victoria, Australia, to follow his first love, music, making his living as a music teacher and organist. After marrying and starting a family, the lot of an impecunious musician may have held less appeal, and in 1903 Wiseman returned to Auckland. He established his own architectural practice and, over the next 12 years until his death at the age of just 50, he received, often with the aid of familial and church connections, several high-profile commissions, including the ferry building, the YMCA building and Auckland Training College (both in Wellesley Street), and "Greenacres," the home of James Gunson, later mayor of Auckland

Energy and force analysis of Ti-6Al-4V linear friction welds for computational modeling input and validation data

The linear friction welding (LFW) process is finding increasing use as a manufacturing technology for the production of titanium alloy Ti-6Al-4V aerospace components. Computational models give an insight into the process, however, there is limited experimental data that can be used for either modeling inputs or validation. To address this problem, a design of experiments approach was used to investigate the influence of the LFW process inputs on various outputs for experimental Ti-6Al-4V welds. The finite element analysis software DEFORM was also used in conjunction with the experimental findings to investigate the heating of the workpieces. Key findings showed that the average interface force and coefficient of friction during each phase of the process were insensitive to the rubbing velocity; the coefficient of friction was not coulombic and varied between 0.3 and 1.3 depending on the process conditions; and the interface of the workpieces reached a temperature of approximately approximately 1273 K (1000 °C) at the end of phase 1. This work has enabled a greater insight into the underlying process physics and will aid future modeling investigations.EPSRC, Boeing Company, Welding Institut

Provincial architect with a competitive edge: Arthur Griffin, the early years

Arthur Reynolds Griffin was born in Nelson in 1883, and began architectural practice on his own account in that city in 1906. He quickly earned two important commissions by winning competitions for the design of the new Carnegie Library in Hokitika in 1906 and the relocated Nelson Girls' School the following year, kickstarting his career. The latter project led to his appointment as architect to the Nelson Education Board and further school jobs. By 1910, he had completed several prominent commissions in Nelson, including the replacement Trafalgar Hotel in the central city, the new Home for Old People in Waimea Road, and the imposing new premises for the Nelson Evening Mail. He went on to design numerous notable Nelson landmarks, such as: the Cawthron Steps in front of the cathedral (1913); Nelson Hospital (1925), since demolished; and the Trathen's Building in Trafalgar Street (1922), demolished in 2016. This paper will, however, focus on his early works, from the first decade of the twentieth century

Foreign capital in a growth model

Within an endogenous growth framework, this paper empirically investigates the impact of financial capital on economic growth for a panel of 60 developing countries, through the channel of domestic capital formation. By estimating the model for different income groups, it is found that while private FDI flows exert beneficial complementarity effects on the domestic capital formation across all income-group countries, the official financial flows contribute to increasing investment in the middle income economies, but not in the low income countries. The latter appears to demonstrate that the aid-growth nexus is supported in the middle income countries, whereas the misallocation of official inflows is more likely to exist in the low income countries, suggesting that aid effectiveness remains conditional on the domestic policy environment

St James and the Good Shepherd: windows on the landscape

Two New Zealand churches completed in the 1930s, St James' Church at Franz Josef/Waiau (James Stuart Turnbull and Percy Watts Rule, 1931) and the Church of the Good Shepherd on the shores of Lake Tekapo (Richard Strachan De Renzy Harman, 1935), feature large plate glass windows behind the altar, affording expansive views of the natural landscape beyond. This represented a significant departure from prevailing ecclesiastical design ideas of the time, with the interior of the churches being intimately connected to the landscape outside, rather than the usual largely internalized atmosphere with any sense of the surroundings limited to light coming through strategically placed decorative or stained-glass windows. It is, however, a design aesthetic that has seldom been utilized in New Zealand since. This paper traverses the history and design of the two churches and their relationships with the landscapes in which they are situated, and concludes that St James' Church provides a heightened religious experience and is a more successful metaphor for the Christian journey

A Scotsman abroad: the architecture of John Scotland in colonial Nelson

John Scotland was one of a small number of architects practising in Nelson during the 1870s. Born in Stirlingshire in 1812, he was the son of a master mason and followed that same calling. However, only scant details of his life are known until he emigrated to New Zealand aged in his mid-50s. As with a number of his contemporaries in the building trades, Scotland turned to architecture, and established a practice in Nelson in 1866. He designed some of that city's grandest homes, including Melrose and Fellworth, both now listed by Heritage New Zealand, as well as various commercial premises and a synagogue. Scotland returned to his native land in 1885, and died in Glasgow two years later

Haunting the Body: An Exploration of Scars as Ghosts

In this paper, I examine Gillian Flynn’s novel “Sharp Objects,” along with the HBO miniseries adaptation, and how they raise important questions about representations of trauma and portrayals of self harm in entertainment. I argue that the protagonist’s self harm scars act as ghosts, because both scars and hauntings are physical manifestations of psychological trauma, and both are messengers from the past. Historically and socioculturally, women are associated with self violence and the supernatural, both of which are prevalent themes in the “Sharp Objects” novel and television show. This paper also examines the important distinction between read and watched trauma, as well as the validity of these creative interpretations of self harm in terms of psychological research and personal testimonies. Applying psychological theories and horror constructs to the narratives, I assert that Flynn and director Jean-Marc Vallée present self harm as a haunting to exploit the association of scars and ghosts with the uncanny, and to attract readers and viewers with dramatic content. Ultimately, I prompt readers to consider their own reactions to and emotions surrounding self harm, and ask that consumers of entertainment practice empathy when considering self harm