Improving Global Quality of Life
Improving Global Quality of Life
Improving Global Quality of Life
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4 Needs and challenges in welding and joining technologies<br />
aspects <strong>of</strong> products fully integrate themselves with processes <strong>of</strong> fabrication excellence. Therefore, one <strong>of</strong><br />
the major scientific challenges is to integrate welding & joining processes with the knowledge <strong>of</strong> welding<br />
mechanics into the design process to ensure high performance welded structures.<br />
Complex and ever increasing requirements <strong>of</strong> welded products include energy saving both in material use<br />
and fabrication while providing long and safe service life with almost no inspection and repair. This situation<br />
will require to use significantly more dissimilar materials (in combination with a multi-material design<br />
approach) to make innovative products. Breakthroughs in the technology for joining dissimilar materials<br />
could lead to new manufacturing strategies that could reduce costs, improve productivity, and open up new<br />
markets for welded structures and components.<br />
The use <strong>of</strong> high energy density welding processes, such as laser beam with advanced materials and design<br />
considerations can tackle various future challenges. Scientific analysis <strong>of</strong> joint features, properties and<br />
predictions <strong>of</strong> performance will remain, however, as one <strong>of</strong> the long-term challenges.<br />
Development <strong>of</strong> methods to expand capabilities <strong>of</strong> laser beam technology for surface modifications, create<br />
“barriers” against crack initiation and growth, property gradient (e.g. to improve fatigue performance via<br />
crack growth retardation) and for forming with better understanding <strong>of</strong> local metallurgical and mechanical<br />
evolutions with predictions <strong>of</strong> weld lifetime and performance.<br />
Tailoring the local properties <strong>of</strong> the weld joints to meet the quality and performance requirements <strong>of</strong> the<br />
product should integrate design guidelines (including local engineering), materials science and mechanics<br />
based modelling and automated testing. Engineers should possess the ability to design a high performance<br />
product and its manufacturing process on the computer before production even begins.<br />
Development <strong>of</strong> intelligent weldments containing embedded sensors combined with real-time defect<br />
sensing techniques and laser based seam-tracking systems will provide new opportunities and challenges<br />
which need to be tackled within fundamental research activities. Here, real-time defect sensing techniques<br />
with their new developments are expected to validate joining processing while determining the fitness-forservice.<br />
This requires strong team work and interaction <strong>of</strong> designer, fabricator and end-user.<br />
Fitness-for-service analysis <strong>of</strong> welded structures is highly developed; however, they mostly use stress-based<br />
approaches. There is a need to develop “strain-based” fitness-for-service analysis procedures particularly<br />
for welded pipelines where welded pipe undergoes high plastic straining during the fabrication or service.<br />
A strategy for this challenge is to establish a task force <strong>of</strong> the IIW Working Units <strong>of</strong> X and XI to generate a Best<br />
Practice Document and/or guidelines for better assessment <strong>of</strong> weld fitness-for-service and life expectancy.<br />
Basic research is needed to develop alloys (base metal and filler wire) for the laser beam welding process<br />
to enable high strength aluminum alloys to be welded with minimal material property degradation. This<br />
will have a major impact on the quality and performance <strong>of</strong> welds <strong>of</strong> aircraft structures while promoting<br />
welding as a key engineering process for metallic airframes. Joining <strong>of</strong> metal to carbon reinforced composite<br />
materials <strong>of</strong> the critical components <strong>of</strong> aerospace structures with durable and damage tolerant design<br />
should also be considered as one <strong>of</strong> the major challenges <strong>of</strong> the future. Furthermore, rethinking <strong>of</strong> the<br />
aerospace design and manufacturing processes to incorporate advanced welding processes will depend on<br />
the comprehensive scientific understanding <strong>of</strong> the welding processes and structural performance predictions<br />
<strong>of</strong> welded components.<br />
A better understanding <strong>of</strong> post-weld heat treatment (PWHT) is needed in terms <strong>of</strong> property (microstructures,<br />
residual stresses etc.) evolution <strong>of</strong> the weld metal and HAZ <strong>of</strong> original and repair welds. For this, the<br />
development <strong>of</strong> a capability to simulate thermal, mechanical and metallurgical changes caused by PWHT<br />
and the integration <strong>of</strong> information with overall system models should be considered as a challenge.<br />
Through Optimum Use and Innovation <strong>of</strong> Welding and Joining Technologies <strong>Improving</strong> <strong>Global</strong> <strong>Quality</strong> <strong>of</strong> <strong>Life</strong> 33