Fundamental studies of materials behaviour for future cold climate applications

The Norwegian oil and gas (O&G) industry, whose operation and activity is founded on the NORSOK standard (covering temperatures down to -14 °C), have 40 years of experience from operations the North Sea. Compared to NORSOK, operations in Arctic regions pose a number of additional material challenges e.g. low temperature embrittlement of materials, relatively large deformations or loads may be encountered merely due to large temperature variations and components and structures may be subject to tough loads by icing or moving ice.Thus, the present project has been built to answer the above stated knowledge needs concerning materials behaviour under Arctic conditions. A broad consortium of key players in the industry is now ready to participate with leading research actors to make this happen. The SMACC project has given the following results: - Education: 5 PhD students are fully financed and 1 is partly funded. In total, 20 MSc students have been involved in the project, and 14 students have had summer jobs in the project. - Science: In total, 33 papers have been published in international journals; and 36 papers have been published in international conference proceedings. - Material database: A comprehensive database management system has been worked out containing all test results, including post processing options. More than 2000 datasets are included. - Design guidelines: The research results have been quickly implemented in the industry by the establishment of knowledge-based design guidelines for both steel and polymers. These will be extensively used in future design and fabrication of structures for Arctic areas. - Multiscale numerical-experimental approach: Numerous models have been developed to predict the effect of temperature on yield and tensile strength, effect of temperature and strength on fatigue crack growth and the effect of residual stresses on ductile-to-brittle transition. In addition, the impact of geometry constraint, material mismatch, microstructure and temperature on fracture toughness level and scatter has been addressed for the steel activities as important basis for the design guidelines. - Steels and welds: A total of 13 steels and 19 welds have been evaluated, which represent unique and invaluable assets. The results achieved have been used in the development of design guidelines for steel. - - Polymers: Here, rubbers with good low temperature properties were developed, and mechanical properties at -60°C were comparable to those at room temperature. The effects of strain rate and low temperature on mechanical behaviour in tension and compression of both rubber-modified polypropylene copolymer (PP) and cross-linked low-density polyethylene (XLPE) have been studied. The results show a strong increase in both the Young's modulus and the flow stress for decreasing temperatures within the experimental range. - Aluminium alloys: The test results support the hypothesis that Eurocode 9 is overly conservative when it comes to HAZ strength reduction for "thick walls", additional 20% strength reduction for wall thicknesses above 15mm. Thus, this requirement should be removed from the standard. The strength in the HAZ increases relatively to the strength in the base material as the plate thickness increases. The room temperature strength is maintained at-60°C. Det konkluderes med at alle faglige delmål er oppnådd. Det konkluderes også med at robuste materialer og løsninger for utbygging i arktiske strø er tilgjengelig, i alle fall ned til -30°C, og at dette kan gjøres basert på de design retningslinjene som er etablert i prosjektet.

The Norwegian oil and gas industry have 40 years of experience from exploration in the North Sea. This experience has also lead to development of national standard such as NORSOK. Unfortunately, NORSOK covers the temperature down to -14°C, which does not account for cold climates such as those typical for arctic regions, where the temperature may fall well below -40°C. In the Arctic, there will be no long time frame to arrive at safe and robust criteria based on empirical input from experience, and one mu st strive for knowledge-based criteria to be applied from "day one". The challenge is twofold; (i) a knowledge basis must be built concerning actual materials and their response to low temperature, and (ii) specifications must be developed for robust design and use of materials and structures. In order to meet these challenges, a new project is proposed to build an arctic materials technology platform due to the need for: (i) Realistic risk assessment and management, (ii) Development of design tools and d esign codes, (iii) Tailoring of new materials for structural or functional (e.g. ice phobic) properties, and (iv) Innovation and design of cost-effective, safe, lightweight, multi-material, structural solutions. Through establishing such platform, the pre sent SMACC project will be essential contributor in the development of special arctic exploration technology. SMACC will educate 6 PhDs, where 5 are fully financed. In addition, 20 MSc students have been involved in the project, tother with 2 foreign students for internships. 10 MSc students have has summer jobs in the project. So far, SMACC has resulted in 21 papers in international journals with perr review, and 34 papers in international conferences with proceedings. A material database has been established with post-processing options (e.g., calculate the characteristic fracture toughness and scatter). Numerous testing of industrially produced welds of different steels have been performed and integrated in the database. Modelling has been focused to achieve prediction options for temperature effects on strength, fatigue properties in terms of crack growth and fracture toughness. candidate polypropylene materials for thermal insulation coatings have very good mechanical properties at low temperatures. For the aluminium part, preliminary results from advances in welding of aluminium alloys may imply that the strength loss in the heat affected zone may be reduced from say 50 to 30%. This is a huge benefit and makes aluminium alloys interesting candidate for many structural applications. Moreover, rubber materials intended for fire protection and thermal insulation have been tested at temperatures below the glass transition, and mechanical properties remained sufficient. A material for soft seals (HNBR) has been demonstrated to maintain properties after repeated cycling through the glass transition temperature. Finally, long-term cold-crystallization has proven to influence mechanical properties in a negative way. However, the stiff crystalline structure melts quickly at temperatures above 10 degrees Celsius. Heating before handling can therefore restore properties. Thus, cold-crystallization remains a concern only for storage and transportation. Design guidelines have been developed for both steel and polymers. These documents contain specifications on how to test the materials in the temperature range from -10 to -60 degC, as well as the associated requirements, covering the most actual temperatures in the Norwegain part of the Arctic areas. These documents are based on the research outcome in the projects, and represents therefore current knowledge, and are therefore not based upon simple extrapolations using existing standard like NORSOK or similar. All initial primary goals and sub-goals will be accomplished, but few PhDs need prolongation to finish their thesis.