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Information technologies and their influence on joining and construction

   
John Weston (2) CEng, BE - Principal Consultant, TWI 

(1) Information technologies and their influence on joining and construction.
(2) Eur Ing John Weston, CEng, BE - Principal consultant TWI Ltd, Granta Park, Great Abington, Cambridge, CB1 6AL, UK.

IV International Seminar on The Use of Steel Structures in Civil Construction and I International Conference on Steel Construction - I CICOM, Sao Paulo, Brazil, 6 - 9 Nov. 2001.

Abstract

Good and appropriate information underpins the production of quality and safe product and is a key to the automation of Steel Construction. Many engineering failures could have been avoided by the proper use of knowledge.

To automate it is necessary to understand, collect and manage information at a level of detail that has not proved necessary with manual activities. A technique for achieving this understanding is outlined.

Key-words:

Information, Automation, TWI.

1 - Introduction

The question, 'Is there a place for robots?' was addressed at an earlier conference [1] . This presentation considers the importance of information in the production of quality and safe product and as a key to the integration of automated Steel Construction processes.

Without good financial information a business will fail. There will also be problems if there is not good technical information. In this context I would make reference to two failures.

Liberty ships were built in large numbers during the World War II. High building speeds, averaging 15 days became possible by changing from riveting to welding. However, losses were high (1 to 2%) in the initial builds because of poor understanding of steel toughness, the use of notch like design details leading to fatigue cracks and poor quality welds causing brittle failure [1] . Much new knowledge was gained from these failures.

In September 1994, at Ramsgate, UK, a walkway collapsed killing 6 and seriously injuring a further 7 after only 4 months service [2] . As a structure the walkway is not unlike many bridges or building elements, figure 1. It comprised a covered ramp running from a fixed trestle on shore to a floating pontoon, a situation which results in onerous operating conditions because of tidal movement and ship impact. The failure resulted from an accumulation of knowledge gaps:

  1. Service conditions (movements in all directions) were not properly considered.
  2. Design calculations were incorrect.
  3. Third party assessment had missed design flaws.
  4. The high carbon steel axles not welded with appropriate procedure and skill.
  5. Weld quality in the critical joints was 'wretchedly poor'
  6. Maintenance was not adequate 
Fig. 1. IDEF0 diagrams give a pictorial representation of the data flow within an integrated fabrication business. The key to reading the diagrams is as shown below:
Fig. 1. IDEF0 diagrams give a pictorial representation of the data flow within an integrated fabrication business. The key to reading the diagrams is as shown below:
Fig. 2. Diagram key
Fig. 2. Diagram key

This failure would have been avoided by the proper use (and training to use) of knowledge which was generally available.

These two examples suggest that timely and relevant information enables safe structures to be fabricated. Timely and relevant information is also the key to efficient manufacture.

2 - What is information?

Any knowledge, or fact, that is needed to enable a fabrication to be put into service safely, quickly and economically.

Traditionally individuals, the designer, the foreman and the welder, have gained knowledge through on the job training and through seeing the results of their activities. Skill knowledge is often poorly documented.

It is also important to recognize that simple facts, the length and sectional dimensions of a beam or plate, can be as important in the manufacturing process as the complicated stress patterns are at the design level. Often these pieces of data have a close relationship. Information changes during processing. For example, dimensions change as sheet is cut, drilled and welded, and material properties alter during forming and heat treatment.

Standards, design rules and codes also contain a lot of important information, which both supports and constrains the construction process.

Information changes as we move through the construction process. For example, the cutting operation changes the dimensional description of a steel plate.

During fabrication the movement of information is akin to the movement of steel elements through the factory. It is important that both these parallel activities are managed efficiently.

Collecting and managing information, Information Technology (IT), is key in any attempt to avoid failures, to increase productivity and to automate the fabrication process.

3 - Planning for integration

The profit of a business is determined by studying the way that money and time is used. Measures are put in place and data gathered so that for example cash flow can be understood and controlled.

The technologist works in a similar way. Traditionally, however, we rely heavily on the skill of the human operator and structures are often produced with little detailed input. For example, the welder is simply asked to make a joint and, by drawing on his skill base, he will often make a satisfactory connection. To get a robotic machine to do the same task we must provide a large amount of detailed data, e.g. Table 1.

Table 1 Typical data required by Robot welding cell

OperationProcessMaterial
Has component arrived? Process Type, e.g. GMAW Material type
Can welding start Power type (AC/DC) Thickness
Trajectory (to work) Current (pulse type?) Joint type
Weld path and speed Voltage (pulse type?) Quality requirements
Weld torch attitudes Consumable type Preheat
Rules for corners Consumable dia. and feed rate Interpass temperature
Rules for weld starts and stops Welding torch type  
Manipulation instructions Shield gas type and flow  
Rules for error recovery Sensor information  
Outputs on cell status Joint filling rules  

If the fabrication operation is to be automated in an integrated way then it becomes important to consider information at a similar level of detail in all areas (e.g. design, purchasing, manufacture, quality) and how the data moves from one to another. Understanding such a complicated information matrix can be difficult. The technique, which was used in several European projects (including CIMsteel), was the IDEF methodology (other methodology include, Campstool). In this pictorially based technique an information change is represented by a box, Figure 2, which describes how Input and Constraint information is Changed, by a Mechanism, to give an Output.

The approach is to commence from an overview, the top, of the process and to gradually work down to the bottom. To ensure the data flows can be understood no more than seven information changes should be developed at each level, Figure 3. Detailed examples are given in figure 4.

Fig. 3. Summary outline of IDEF0 data movement diagrams
Fig. 3. Summary outline of IDEF0 data movement diagrams
Fig. 4.
Fig. 4.
spjwnov2001f4b.gif
spjwnov2001f4c.gif
spjwnov2001f4d.gif
spjwnov2001f4e.gif

Analysis made in this way, of both present and ideal data flows, has allowed leading companies to efficiently integrate automation (refs 3 Odense) [3] . The analysis gave these companies the understanding to choose the appropriate mechanisms. For example, in figure 4 the activity Join Components (in A433 ASSEMBLE COMPONENTS) the process might be welding and the mechanism, Man or Robot. Also, detailed will be the data instruction set that is needed by that mechanism so that the optimum machine, or computer system, can be purchased.

It is suggested that without a good understanding of the information movement, transformation and interactions that an analysis procedure gives, then it will be difficult and expensive to achieve the objective of fully integrated automation.

Even with the understanding of information needs, there will be the challenge of gathering the necessary detailed data, which will also benefit present manual operations.

4 - Sources of data

With the understanding of information needs another challenge will be to gather detailed data (that will also benefit present manual operations). Sources include:

Standards: The National, United States (ASME and AWS) and British documents are good sources of information with relevance to all aspects of Fabrication. They are not just constraints on working practice, but usually also provide valuable design and operational guidance, e.g. Annex C EN1011-2:2001 on avoidance of hydrogen cracking.
Professional Institutions: These bodies are important in promoting standards of both individuals and the documents with which they work (e.g. Institutes of Civil, Mechanical and Welding Engineers). TWI is closely associated with the Welding Institute and the Welding & Joining Society.
Consultants: The individuals and partnerships have developed skills, which support fabricators in specific areas of their work, e.g. design, procedures, health and safety, welding technology.
Universities: Universities can provide consultancy, research facilities and new staff. Their prime function is education and their priority clients should be their students.
Suppliers and Trade Organizations: This is an important source of specialist but sometimes biased information. Welding and Steel companies can be excellent sources of data and advice, particularly related to their own products.
Research and Technology Organizations: These bodies, such as SCI and TWI, provide industrial, client focused, services that lie somewhere between those of the Universities (research) and the Trade bodies (sales).

5 - TWI and the provision of information

5.1 - The Organization - TWI

TWI Ltd has, for over 50 years, provided specialist advice to the fabrication sector. It was formed, as the British Welding Research Association, when arc welding was a new process and the behavior of the joints not well understood. Now, as then, TWI activity is split roughly 50/50 between the engineering performance of, and the making of, a joint. While fusion welding of steel was the initial focus of attention, today, most joining processes and materials get attention. TWI works for subscribing member organizations that are to be found worldwide.

Contract work is carried out for members to support them in the whole range of activity from, new concept designs, through development of products and the investigation of failure to Life Cycle performance. The work may answer simple questions of how to join A to B but may require fundamental research such as that underpinning the new Friction Stir welding technique. Engineering work, relevant to fabricators include:

  • Fitness-for-purpose analysis/review
  • Finite Element Assessment
  • Material property and fracture mechanics analysis
  • Fatigue performance
  • Quality assurance/Non Destructive Testing

In the process area, experts give advice on the application and use of most fusion and forge welding and cutting processes (e.g. c, laser, Electron Beam, Friction and Resistance) and on adhesive bonding techniques. Feasibility studies, prototype product trials and procedure development work are all typical activities.

Also important are those services which are available generally available:

  • Technical knowledge - an Internet database of knowledge
  • Participation in Standards Committees - to improve and develop standards
  • The help desk - a technical enquiry service
  • Training - ranging from theoretical design issues to practical skills
  • Conferences and workshops - helping to transfer knowledge
  • Weldasearch - a computer abstract database of the worlds welding literature

Through these services TWI provides an important service in addressing the knowledge acquisition issues raised by the failures mentioned earlier.

5.2 - Technical knowledge

Our website is an electronic database containing information and expertise on joining, materials and manufacture. It has been developed with several objectives; the first being to give TWI members fast access to basic knowledge at any time to all levels of the data. In this way the staff resource can be available for the more difficult questions. A second objective has been to provide answers to some of the common joining related questions to the public at large and so advertise TWI capability.

Users must register and are given an individual user name and password that are required at log on. Our technical knowledge is accessed via the corporate web site, www.twi.co.uk, which gives data on:

5.3 Consultancy, Training and Qualification

Buyers guide
Job vacancies
Joint Technical Information
Links to other sites
Member services
News and events
Products and software
Training and Qualification

Member companies can call on TWI's 450 staff for specific advice on joining technology. Assistance given ranges from the conceptual, related to product design, to the highly practical, 'How to join A to B?' The experts also support training staff in the delivery of courses, often on site, which range from; 'the design of welded joints' to 'Skill training to the level of BSEN 287'.

TWI through its association with the Institute of Welding provides training and leading to the certification of NDT inspectors and Chartered and European Welding Engineers. Such qualifications are important in ensuring that our industries have staff with the relevant knowledge.

6 - Summary

Knowledge and skill, appropriately applied, is vital to the safe and efficient use and manufacture of structures. Universities, Suppliers, Institutions and Research and Technology Organisations play vital roles in generating data and providing the training, skills and qualifications.

7 - References

  1. Lancaster J, Handbook of structural welding, Abington Publishing 1997 ISBN 1 85573 343 9
  2. Chapman J C, Collapse of the Ramsgate Walkway, The Structural Engineer, Vol. 76, No. 1, 7 January 1998
  3. Skjelstrup C E, Welding Robots in Shipbuilding, Automation and Robotisation in Welding and Allied Processes, Int. Conf. Proc. Strasbourg 2-3 September 1985

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