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TITANIUM, in common with the other industrial structural metals, can be alloyed to improve property levels to match the design requirements of a variety of chosen applications. Unlike copper and iron and other traditional metals however the alloys of titanium are less the discoveries of chance than products of deliberate development based on alloy theory. Commercially pure titanium, 99% plus Ti, at room temperature has a hexagonal (CPH) crystal lattice alpha phase. This transforms to beta phase centred cubic (BCC) lattice at approx 900°C. Titanium alloys are based on stabilisation of one or other of the two phases or the precipitation of compounds within either lattice. Alloys built around the CPH phase are denoted alpha alloys those around the BCC as beta alloys and those which feature both phases in equilibrium at room temperature are alpha‐beta alloys. Interestingly, relatively few of the formulations first developed have survived the test of time. Alloys which in the laboratory looked extremely promising proved too difficult to melt or process in volume, intractable in forging or machining and fell short of their expectations in final application. The one alloy which has so far withstood all challenges to its supremacy in the widest range of applications within the aerospace industry is the alpha‐beta formulation Ti‐6A1–4V. This alloy frequently described as the “work horse” of the titanium industry is available in all semi finished forms and has carried for some 30 years the burden of introducing titanium as a light strong reliable competitive structural metal in aerospace applications.

This is the collection of papers read at the 1967 Melbourne symposium which had, as the main theme, design, economic and operational aspects. These are further summarised in two categories, the design and operational aspects of the fatigue problem in general aviation and transport aircraft and, of unusual interest, the economic aspects of the fatigue problem as it affects both operators and manufacturers. Altogether this covers the structural load measurement and analysis, design and certification programmes of a wide range of aircraft. At one extreme are the several papers on helicopters such as “The application of Ti‐6A1‐4V to fatigue loaded components”, “The fatigue and fail‐safe programme for the Lockheed 286” and also among light aircraft, “The design and certification for executive type aircraft”, “Agricultural aircraft flight loads”, “Typical spectra and some observations on airworthiness” and “The New Zealand light aircraft fatigue meter programme”. At the other extreme, there are papers on “Design and philosophy and fatigue testing of the Concorde” and “Fatigue design and test programme for the American SST”.

This paper focuses on recent advances in direct freeform fabrication of high performance components via selective laser sintering (SLS). The application, known as SLS/HIP, is a low cost manufacturing technique that combines the strengths of selective laser sintering and hot isostatic pressing (HIP) to rapidly produce low volume or “one of a kind” high performance metal components. Direct selective laser sintering is a rapid manufacturing technique that can produce high density metal parts of complex geometry with an integral, gas impermeable skin. These parts can then be directly post‐processed by containerless HIP. The advantages of in situ encapsulation include elimination of a secondary container material and associated container‐powder interaction, reduced pre‐processing time, a short HIP cycle and reduction in post‐processing steps compared to HIP of canned parts. SLS/HIP is currently being developed under a DARPA/ONR program for INCONEL® 625 superalloy and Ti‐6Al‐4V, the demonstration components being the F‐14 turbine engine vane and the AIM‐9 missile guidance section housing base respectively.

Selective laser sintering (SLS) is a solid freeform fabrication process whereby a part is built layerwise by scanning a powder bed. The processability of metal powder varies depending on the state of the powder prior to SLS. A powder thermal pre‐treatment was developed which involved degassing the powder at an elevated temperature in a vacuum. Without powder thermal pre‐treatment, the powder may flow poorly and may “ball” or form molten clumps during the laser exposure rather than wetting into the present and previous layer. These effects result in SLS parts with poor surface finish, mechanical properties and density. The purpose of this study was to identify for titanium alloy powder the mechanisms responsible for the improvements obtained after powder thermal pre‐treatment and to optimize the thermal excursion.

PRODUCTION of titanium in the USA during 1974 has been estimated at 15 000 tons, with the aerospace industry taking 75 per cent of the output. This is a considerable increase in the amount used during the preceding twelve months, and indicates that the trend towards titanium products for strength to weight ratio benefits has been accelerated by companies finding that cost reduction can be achieved by extensive use of titanium alloys. It is of interest to note that commercial aviation in the USA has represented the largest single user of this metal, but that this has recently changed with a marked trend towards military applications and in particular, the Grumman F‐14 and McDonnell Douglas F‐15 aircraft.

HOWMET Turbine Components Corporation announced the successful completion of production qualification of the first investment cast dynamic structural rotorcraft component. The cast component is produced at lower cost than the currently forged part, while being physically and functionally interchangeable with the forging.

A numerical model for solving either elastic‐plastic, elastic‐viscoplastic or purely viscoplastic deformation of thin sheets is presented, using a membrane mechanical approach. The finite element method is used associated with an incremental procedure. The mechanical equations are the principle of virtual work written in terms of plane stress, which is solved at the end of each increment, and an incremental semi‐implicit flow rule obtained by the time integration of the constitutive equations over the increment. These equations are written using curvilinear coordinates, and membrane elements are used to discretize them. The resolution method is the Newton‐Raphson algorithm. The contact algorithm is presented and allows for applications to cold stretching and deep‐drawing problems and to the superplastic forming of thin sheets.

This bibliography is offered as a practical guide to published papers, conference proceedings papers and theses/dissertations on the finite element (FE) and boundary element (BE) applications in different fields of biomechanics between 1976 and 1991. The aim of this paper is to help the users of FE and BE techniques to get better value from a large collection of papers on the subjects. Categories in biomechanics included in this survey are: orthopaedic mechanics, dental mechanics, cardiovascular mechanics, soft tissue mechanics, biological flow, impact injury, and other fields of applications. More than 900 references are listed.

Surface roughness is an important evaluation index for industrial components, and it strongly depends on the processing parameters for selective laser molten Ti6Al4V parts. This paper aims to obtain an optimum selective laser melting (SLM) parameter set to improve the surface roughness of Ti6Al4V samples.

A response surface methodology (RSM)-based approach is proposed to improve the surface quality of selective laser molten Ti6Al4V parts and understand the relationship between the SLM process parameters and the surface roughness. The main SLM parameters (i.e. laser power, scan speed and hatch spacing) are optimized, and Ti6Al4V parts are manufactured by the SLM technology with no post processes.

Optimum process parameters were obtained using the RSM method to minimise the roughness of the top and vertical side surfaces. Obtained parameter sets were evaluated based on their productivity and surface quality performance. The validation tests have been performed, and the results verified the effectivity of the proposed technique. It was also shown that the top and vertical sides must be handled together to obtain better top surface quality.

The obtained optimum SLM parameter set can be used in the manufacturing of Ti6Al4V components with high surface roughness requirement.

RSM is used to analyse and determine the optimal combination of SLM parameters with the aim of improving the surface roughness quality of Ti6Al4V components, for the first time in the literature. Also, this is the first study which aims to simultaneously optimise the surface quality of top and vertical sides of titanium alloys.