TWI Support for the construction industry

There are many driving forces behind technological progress in the construction industry. These trends are summarised in the following table.

Reduced dead weights	Steel framed houses
Earthquake resistance	Modular structures
Flexible structures	Temporary structures
Span large areas (cladding)	Tunnel repair
Environmentally friendly	Column wrapping
Human interaction	Bridge repair and improved payload
New materials (plastics, composites, adhesives, alloys)	Fuel economy and noise reduction
Increased recycling	Quicker construction on site
Increased longevity	Fast track construction and automation
Reclamation of old structures	Improved modes of analysis
Repair of concrete structures	Aesthetics
Low cost housing	Development and joining of fire retardant materials

All of these have relevance across the world and are thus considered vital to the progress of construction technologies. TWI provides support for the construction industry in many varied areas, and our staff possess wide experience and expertise in these areas. Some of the subjects that have particular relevance are given below.

Joining technologies

TWI has spent many years building up its reputation as one of the largest and best research and technology organisations focusing on materials joining technologies, and hence the experience of TWI staff covers a wide range of processes. Work is done on improving existing processes and developing new techniques.

Arc welding

All common, and most not so common arc welding processes have been studied by TWI at some time, and staff can provide advice on all aspects of the subject, from design of joints, through welding procedures and training to inspection of welded joints. Staff are available to advise on process variants, welding consumables, including filler wires & fluxes, procedures for industrial applications, repair procedures, techniques for welding advanced materials, high productivity processes, shielding gases, wet underwater welding and mechanised processes.

Power beam technology

TWI has long been known as experts in laser and electron beam processes, and has a proven track record of this expertise. In the field of electron beam welding TWI staff are actively involved in consultancy and project work for industry in the areas of welding, cutting and surface treatment, feasibility studies and process development, and the development, manufacture and supply of prototype equipment. The development of pulsed electron beam welding is a good example of where TWI is leading the way in process development. The facilities available include numerous electron beam installations with powers ranging from 5 to 150kW, and high vacuum, reduced pressure and non-vacuum processing facilities, with many specialist staff available to provide advice and assistance.

TWI's involvement with laser welding stretches over four decades, and still the frontiers of the technology are being broken. Services are provided to many industry sectors including shipbuilding, automotive and aerospace. Facilities include a large range of CO₂ and Nd:YAG lasers and work handling facilities with the back up of trained staff. A significant amount of work has been done on the development of laser welding procedures for C-Mn steels as well as the studying the efficacy of process gases and improving the quality of laser cut edges.

Friction processes

Friction based processes have advantages that include low distortion and thermal disruption, and the ability to join dissimilar materials. A number of techniques, which are of interest to the construction sector, are part of TWI's core business.

Friction stir welding

Aluminium plate and sections can be welded without distortion by the friction stir welding technique invented and developed by TWI. The low associated distortion is attributed to the low heat input and aluminium section thicknesses range from 1 to 50mm for single pass welding.

Friction hydro pillar processing is used for the repair of cracks and other defects in thick sections using a consumable tool. This technique is available for a wide range of materials and consumable rods vary in diameter from 10 to 50mm.

Friction surfacing can be used to deposit corrosion resistant surfaces on materials for use in marine and other environments, and layers can be applied to new or worn components.

TWI's experience of friction welding is extensive and covers all ramifications of the technique - linear, rotary, radial and orbital. The techniques have been proved to produce high quality welds.

Surface engineering

TWI's surface engineering team provides technical support to industry through a wide range of technologies, producing coatings from 1µm up to 10mm thick. Project work and consultancy has provided staff with expertise in coatings for wear & corrosion resistance & thermal barriers, coatings for biomedical & electronic applications, repair & maintenance by surface engineering, troubleshooting, applications development, process selection, and coatings analysis & testing. The facilities at TWI include thermal spraying including HVOF, arc & flame, arc weld surfacing (plasma transferred arc, submerged arc strip cladding, MMA, MIG, TIG), friction surfacing, resistance surfacing, sol-gel coatings, and Nd:YAG and CO₂ laser surfacing & transformation hardening.

Adhesives

The UK's Centre for Adhesive Technology is based at TWI. Adhesives are playing an increasing role in an ever widening range of manufacturing industries. TWI advises companies on -

applications where adhesives can be used in place of traditional joining methods
selection of adhesives for specific materials
joint design for optimum quality and productivity
bonding procedures and quality assurance.

Composite structures

To reduce the overall dead weight of a building, there has been much interest in the use of composite structures, and TWI has been heavily involved in the development of this technology. The benefits of using composite structures range from the ability to produce building modules in a factory to the use of cladding materials to make up outer walls of buildings. Both of these lead to a reduction in on-site construction time and thus reduce costs significantly. A technique known as pulltrusion (similar to extrusion, with the product being pulled through a die rather that pushed) also offers the advantage of weight reduction, along with products being corrosion resistant and custom shapes easily produced. Components produced by this method are typically I-beams and are used for bridge construction.

Barrikade® is an innovative technology developed by TWI. This heat resistant composite structure can be used for fire partitions and fire doors, often in areas of high occupancy such as hospitals, theatres and shopping malls. For more information on Barrikade® click here .

Mechanical fastening

In addition to physical joining, TWI has studied methods of mechanical fastening, such as bolting and riveting, and have been active in the development of novel methods of materials joining, for example self piercing rivets. The expertise in mechanical fastening spans sheet joining, plastics & composites and structural engineering. TWI can provide advice on process selection, research into effects of process parameters in clinching & riveting of sheet metals and the mechanical properties of fastened joints.

Materials technologies

The work of TWI covers a wide range of materials including ferrous and non-ferrous metals, plastics, ceramics, composite and polymer coated materials. TWI offers its members a wide range of services including weldability of materials, materials selection, failure analysis, microstructural properties of welded joints, materials analysis, hydrogen measurement, fume assessments, on-site materials evaluation, corrosion testing, corrosion performance of welded components, corrosion failure mechanisms, standards verification & evaluation. The extensive experimental facilities allow these services to be provided effectively and efficiently. These facilities include H₂S laboratory with full-ring & constant load testing of tensile & beam specimens, autoclaves, slow strain rate & corrosion fatigue testing in H₂S, hydrogen autoclave, extensive metallographic & analysis facilities.

Innovation

TWI has performed a lot of work in the development of novel materials and joining technologies, and is actively involved in producing innovative ideas and developing these ideas into actual products. The products and processes that are of relevance to the construction industry are: