Self-assessment module 4

1. Answer the following questions:

1. What kinds of corrosion do you know?

2. What is the meaning of the word “corrosion”?

3. How many types of corrosion do you know?

4. What is the most dangerous type of corrosion destruction?

5. Why is the joining of soft tissues based on heating called welding?

6. Why is not the laser welding suitable for surgery?

7. What allows fastening surgery performance and reducing blood loss?

8. Will the fields of rational application of welding expand in the future?

9. What is thermit welding?

10. What can aluminium be used for in thermit welding?

2. Give the English equivalents of the following words and word-combinations:

Газове середовище, гетерофазний сплав, оксидна плівка, кількісний коефіціент, недолік, гальмувати, високочастотний струм, специфічні вимоги, самонастройка, клейові засоби, плотність, тигель, розкислювач, взаємовамінення.

3. Are the following statements true or false?

1. Corrosion is a spontaneous destruction of plastic.

2. The structural corrosion is the most dangerous type of the corrosion destruction.

3. The structural corrosion is observed in welded joints of aluminium alloys.

4. Oxide film develops at the boundaries of grains and propagates into the bulk of metal.

5. Operation with application of electric welding tools on man ( joining a stomach wound) for the first time in the clinical practice was made in the Central Clinical Hospital in June, 2000.

6. Although widely used in the railroad industry, welding is probably one of the least understood pro the balance of manufacture.

7. The portability, cost-effectiveness and convenience of thermit welding results in its continued extensive use.

8. Thermit welding is actually as much a casting as it is a weld, and consistency may be difficult to achieve.

9. Aluminium doesn’t play a key role in thermit welding.

10. The higher hardness also improves fatigue and deformation resistance and more closely matches the hardness of new head-hardened rails.

4. Read the text. Comment on the advantages and disadvantages of the floating welded mega-structures.

The idea of creating floating offshore structures of super-large dimensions, so-called floating mega-structures (FMS) originated and found its practical application in Japan. This is exactly where the greatest experience of construction of large floating structures has been accumulated, namely: ocean ships, offshore platforms, piers etc. Some of the largest floating structures are “Sea Giant” tanker - 440 m long, 58.8 m wide with 28.8 m draft and sea oil storage facility “Hiroshima” - 397 m long, 82 m wide with 25.5 m draft. Such huge facilities were mainly manufactured in shipbuilding yards in the docks or berths. Their dimensions were limited just by the capabilities of a specific fabrication. The idea of FMS was based on developing a structure of a much larger scale– up to several kilometer length. Such a task had no precedent in the world practice. In order to implement it (build the FMS and conduct full-scale testing of the proposed engineering and design solutions) 17 steel-making and ship-building companies of Japan formed in April, 1995 a Technological Research Association MEGA-FLOAT (TRAMF) that carries out the entire package of scientific, design, engineering and production developments.

Over the period of three years an experimental sample of FMS of 2x60x300m size was designed and built, which was followed by making in 1998 a three-year program, including investigations of various aspects of the problem of FMS development, in particular the possibility of their practical use. Investigation led to construction of a full-scale model of a floating airport. It was 1 km long, 120 m wide and 3 m high. The full-scale model was fitted with systems of instrument landing, landing beacons, glide-path system and other modern equipment.

A designed and manufactured full-scale model of 9500t weight and area of 8.4x10⁴ m² in the form of a box-shaped pontoon consisted of six modules, the largest of which was 383m long and 60m wide. The modules were primarily made of blocks, having longitudinal and transverse partitions, as well as a set of stiffeners covered with steel plates on all sides.

When modules were joined on the water surface, specific problems arose: ability to apply welding is limited by the level of modules; structures afloat develop higher deformation than on the ground; need to perform underwater welding; inability to provide setting in open sea. Therefore, the monitoring of the dimensions of a structure continuously is very important.

Computer application allowed determination of the optimal welding modes providing minimal linear error when extended welds are made, namely 30mm per 1000m of the weld. In addition, welding was performed at night to lower the level of deformations induced by temperature difference between the module underbody and upperworks heated by the sun. Depending on the depth the portable semi-automatic machines (“dry” welding near the waterline) or automatic machines (welding with local drying) of a special design were used.

As the anticipated life of FMS should not be less than 100 years, it was necessary to envisage all the measures to provide its reliability in service. Therefore, these following problems were addressed during the project: development of a system of optimal protection from corrosion; studying the ability to apply advanced materials; development of the technology of long-term monitoring; development of the technology for underbody repair.