One objective of the program is to gain a better understanding of the effect of welding on high strength cold formed steel members and hence to develop welding procedures which will ensure ductile behaviour and reduce the risk of failure.

A second objective is to conduct research aimed at ensuring the continued serviceability of offshore platforms when they near the end of their design life.

A third objective is the development of intelligent technology for ensuring quality welding in sheet metal components for the automotive industry.

A fourth objective is to develop an understanding of cumulative fatigue damage of railway bridges in order to contribute to the development of strategies for the repair and restoration of existing bridges, which is a vital part of preserving Australia's rail network.

These objectives will be achieved through the completion of the following projects:

The effect of welding on the properties of cold rolled steels
The structural and property changes in the weld zone of arc welded cold rolled, zinc alloy coated, structural steels are being evaluated in order to quantify the loss of strength associated with the welding process, and to elucidate the mechanism of softening. The effect of the zinc alloy coating on the macro- and microstructures of the weld bead and the mechanical properties of the weldment is also being investigated. The project will enable the optimisation of the welding procedure to minimise softening and is intended to lead to more realistic and cost-effective use of high strength cold rolled steels, such as G550 grade recovery annealed steels, in the design and fabrication of structural members for building construction and other applications.

Welding of zinc coated steel sections
This project commenced in the latter part of 1998 with a thorough literature search. In addition an experimental assessment of process stability was undertaken using a computer based objective stability measurement system. From the literature it was confirmed that the zinc coating caused a deterioration in arc stability and an increase in fume. Although the deterioration can be ameliorated to some extent by optimising the normal welding parameters (torch angle, welding speed and current) it was concluded that a more fundamental study of the mechanisms involved was required. From the initial investigation it was also postulated that the adverse effect of the zinc could be a result of:

On the basis of this analysis a series of trials was made in pure argon (to avoid ZnO formation) using flux cored wires to control arc stability. Additional secondary shielding was also attempted and this improved bead appearance and reduced fume. The initial results of these trials were encouraging and will be extended to include alternative shielding gases. A more fundamental study of the proposed mechanisms will be conducted in parallel in an attempt to highlight other opportunities for process modification.

Strength of welded sheet steel connections
An experimental program will be conducted to provide the data necessary for design engineers to allow for welded connection of high strength steels to AS1397 when designing cold formed structures to AS/NZS 4600. Design models and design rules will be prepared based on the testing program.

Local fabrication and installation of offshore structure jackets
The objective of this project is to modify the conventional fabrication methods for large jackets and tailor them to the capacity of Australian yards. This will be achieved by taking advantage of modular construction.

Offshore structure damage mechanisms
The damage of thin walled structures due to blunt indentation will be assessed experimentally and a simplified model will be developed for material failure and verified by small scale tests. This will be applied to the damage inflicted by the impact loading of ships on offshore structures.

Platform reliability
The failure of offshore platforms under storm overload will be studied and guidance developed for load factors required to achieve a specified level of reliability.

High productivity welding of X80 steel for offshore and ship construction
X80 steel has been developed to improve economics in pipeline construction through increased structural strength and toughness. This new Australian steel grade could also prove advantageous over conventional C-Mn structural grades in ship and offshore construction. However the performance in high productivity welding applications has not been demonstrated. This project aims to develop a welding technology package to demonstrate weld zone integrity and at least equivalent productivity to conventional steels.

Improved productivity from high quality titanium steels
With the increasing demands for steel structures, there is a need to use more efficient and user friendly steels that can easily be welded and fabricated. This project has investigated the effect of titanium as a micro-alloying element on the microstructure and mechanical properties of the heat affected zone and in particular the coarse grain heat affected zone (CGHAZ) on oxy, plasma and laser cut samples and weldments. The research has been based on a study of two different grades of steels, 250 and 350 made by BHP and those imported from overseas manufacturers.

Steels containing titanium were shown to have better base material impact properties than titanium free steels. Also, the impact properties of the CGHAZ of the welds are lower compared with those of the base material. For the thermally cut samples a generally narrower CGHAZ and smaller grains in the CGHAZ have been observed in steels that contain titanium compared to other steels without titanium. The properties of the CGHAZ have been influenced by the presence of TiN in the microstructure. It is known that the presence of these particles in the microstructure restricts the austenite grain growth during the weld cycle.

Establishing the beneficial effect on the heat affected zone of titanium additions in structural steels will be of direct benefit to both the supplier and the users of these steels.

Friction welding of similar and dissimilar materials
A major facility is being developed at the University of Adelaide for friction stir welding of similar and dissimilar metals and high strength thin walled tubes in steel and aluminium based metal/metal composites. There was some delay during the course of 1998/99 due to the departure of Professor Ian Henderson but the project has been taken over with enthusiasm by Dr Denny Graham and a group of some six postgraduate students are working in the area of friction stir welding.

Flash butt welding quality
Flash butt welding defects reduce steel processing throughput and yield in the manufacture of critical products such as wheel rims. Monitoring of the weld quality on line would enable costly production delays to be minimised.

Flash butt welding involves a complex array of both electrical and mechanical parameters as well as material characteristics to ensure a sound consistent joint. The weld monitor developed and built by CSIRO under this project, which involves both hardware and software is nearly completed. The monitor is a significant step forward in evaluation of the welding operation. It is currently undergoing industrial trials to assess some of the process parameters during the welding operation.

Weldability of magnesium alloys
The weldability of some widely used wrought and cast alloys will be studied and quantified. The data obtained will aid the selection of material and weld procedure for specific structural applications.

Structural integrity of railway bridges
The importance of structural reliability and integrity to the safety of railways operations is clear. This project addresses issues of inspection and analysis of welded structures in the Australian Railway System, in terms of the objectives of the Total Asset Management and Risk Management philosophies of State and Federal Public Works Agencies and Departments.

The basic approach to structural integrity assessment is patterned after the three-stage methodology presented by the Advanced Materials Section at ANSTO. This incorporates structural design, loading history, component stresses, and material properties and conditions. This general framework is accepted in the Electric Power Industry and in aerospace and military programs.

The technical activities required for the project cover structural inspections, including visual inspection, NDT, strain gauging, accelerometry and materials inspections, materials analyses including microscopy, and structural analyses including finite element analysis.

In the past year the three stage methodology has been adopted to the assessment of welded railway structures in collaboration with Railway Operations and Engineering in New South Wales and decision procedures have been developed for inspection and analysis. These will provide designers, fabricators, and operators of welded railway structures with: a formal assessment methodology; methods to overcome conservatism in design codes; confidence in structural safety for continued service and sufficient lead times to plan for maintenance or replacement.