Previous research project II

Thermal Fatigue of Coated Superalloys

Modelling of Physical Properties of  Steels

Thermodynamic Calculation and Phase Transformations in TiNi and Cu-based Shape Memory Alloys

Low cycle fatigue testing of aluminium alloys at elevated temperatures

High temperature mechanical properties of Al-alloys

Models for Creep Cavity Development and Rupture

The development of a property data bank for stainless steels with corrosion data

Use of shape memory alloys

Design of high temperature plants with respect to creep

Welded joints in aluminium structures.

Usage of aluminium matrix composites

System for the design of aluminium alloy components

Physical properties of aluminium alloys

Thermal Fatigue of Coated Superalloys Steels

Research leader: Rolf Sandström 

PhD student: Mats Lennartsson 

Project period: 2002-2006

Keywords: Thermal Fatigue, Small punch testing, Coating, Creep Resistant Steel

Project description: The purpose of the project was to understand the crack initiation and crack propagation during thermal fatigue of coated superalloys. The small punch testing technique was used, a technique suitable to the evaluation of local mechanical properties in materials. Through modelling of the distribution of thermal strains and stresses the crack initiation could be predicted related to the characteristic strength and ductility of the substrate material, coating, and interface. The crack propagation was modelled with fracture mechanics approaches.

Publications:

• M Eskner, R Sandström, Measurements of the ductile-to-brittle transition temperature in a nickel aluminide coating by miniaturized disc bending technique, Surface and Coating Technology 165 (2003) 71-80
• H Brodin, M Eskner, The Influence of Oxidation on Mechanical and Fracture Behaviour of an Air Plasma-Sprayed NiCoCrAlY Bondcoat, Surface & Coating Technology 187 (2004) 113-121
• M Eskner, R Sandström, Measurement of the elastic modulus of a plasma-sprayed thermal barrier coating using spherical identation, Surface and Coating Technology 177-178 (2004) 165-171
• M Eskner, R Sandström, Mechanical properties and temperature dependence of an air plasma-sprayed NiCoCrAlY bondcoat, Surface and Coatings Technology 200 (2006) 2695-2703

Source of funding: TFR

Modelling of Physical Properties of  Steels

Research leader: Rolf Sandström
PhD student: Ulrich Bohnenkamp
Project period: 1999 - 2002
Keywords: Stainless steels, physical properties, strength, creep, ductility, materials design, databases, composition

Objectives: To find relationships between physical properties and composition and heat treatment, which can be used in the design of advanced steels.

Results: Experimental data on density, elastic modulus, Poissons ratio, integral and differential thermal expansion, specific heat capacity, specific electrical resistivity, and thermal conductivity of 200 steels under different conditions were collected into a database. Models for the influence of composition on the density and the elastic properties of theese steels were developed. Models for calculation of the properties from composition, microstructure, and heat treatment for the remaining properties were established. The relationships were used to make grade optimisation.

Publications:

• U Bohnenkamp, R Sandström, Evaluation of the electrical resistivity of steels, steel research, vol 71, No.10 (2000) 410-416
• U Bohnenkamp, R Sandström, Evaluation of the density of steels, steel research 71 , No.3 (2000) 88-93
• U Bohnenkamp, R Sandström, Evaluation of the elastic modulus of steels, steel research 71 , No.3 (2000) 94-99
• U Bohnenkamp, R Sandström, G Grimvall, Electrical resistivity of steels and face-centered-cubic iron, J. Appl. Phys. 92, 4402-7 (2002)

Source of funding: TFR

Thermodynamic Calculation and Phase Transformations in TiNi and Cu-based Shape Memory Alloys

Research leader: Rolf Sandström
Scientist(s): Weijia Tang, Zhongguo Wei
Project period: 1997 - 2001
Keywords: TiNi, CuZnAl, CuAlNi, Shape Memory, Thermodynamic Evaluation, Phase Equilibrium, Martensitic Transformation.

Objectives: To investigate the influence of the third element additions on the martensitic transformation, order/disorder transition and kinetic evolution of LRO and SRO, thermodynamic properties, and phase stability in TiNi, Cu-based and other beta-phase shape memory alloys (SMA),employing both thermodynamic approach and experimental characterization.

Results:
(1) Thermodynamic descriptions for binary TiNi SMA were established. The parent B2 phase described with (Ni,Ti,Va)0.5(Ni,Ti,Va)0.5 two-sublattice model was treated as the ordered-phase of BCC in line with the treatment of the beta phase in the Al-Ni system and was re-assessed based on more pricise experimental data from the martensitic transformation. The Ti-Ni phase diagram was calculated including the low temperature B19' phase. The predicted thermodynamic properties as well as the Ms temperature and the stress rate were in good agreement with experimental data. All these researches layed a foundation for further study of ternary TiNi SMA. As the first step, ternary TiNiCu system was been studied. The thermodynamic properties of the pseudo-binary TiNi-TiCu system were analyzed using different models for the Gibbs energy of individual phases in the system. Following the modeling of the binary B2 phase, the ternary B2 phase was treated with the two-sublattice model (Cu,Ni,Ti,Va)0.5(Cu,Ni,Ti,Va)0.5 and thus the disordered BCC and ordered B2 were described with one single Gibbs expression, which indicates more physical meaning. The solubility of Ni in the compound TiCu with B11 structure was described with a similar model without vacancy. The thermodynamic description of the TiNi-TiCu system have been obtained from the optimization based on experimental information from literature. The effect of Cu on the stability of the TiNi B2 phase is examined at various temperatures. Martensitic transformation were experimentally studied by DSC method for the pseudo-binary TiNi-TiCu system.

(2) The order-disorder transitions in Cu-based SMAs were calculated using modified Bragg-Williams approximation. Universal relationships between LRO parameters and the martensitic transformation temperatures were established within a mean field approximation. Experimentally, we have successfully applied a recently-developed advanced calorimetry technique(MDSC)to shape memory alloys. Some unexpected results, such as two kinds of relaxation peaks, were identified and separated from the reverse martensitic transformation.

Publications:

• Weijia Tang and Rolf Sandström, "Evaluation of Phase Transformation Tensor and Limitations of the Constitutive Relations for TiNi Alloys", to be published in J. of Intelligent Material Systems and Structures, 1997.
• Weijia Tang, "Thermodynamic study of the low-temperature phase B19' and the martensitic transformation in the near-equiatomic Ti-Ni shape memory alloys", Metall Trans 28A (1997) 537-544.
• Weijia Tang and Rolf Sandström, "Some Aspects on TiNi SMA Properties Based on the Calculation of Ti-Ni Phase Diagram", Symposium on Shape Memory and Superelasticity: Engineering and Biomedical Applications, Pacific Grove, CA (USA), 1997.
• Z G Wei, C Y Tang, W B Lee, Design and fabrication of intelligent composites based on shape memory alloys, Journal of Materials Processing Technology 69, Issues 1-3, (1997) 68-74
• Z.G.Wei and R.Sandström: Role of short range disorder in long range ordered matrix: comments on "effect of quenched-in vacancies on the martensitic transformation", Scripta Mater. 37, 1997, pp.1727-1732.
• Z G Wei, H Y Peng, W H Zou, D Z Yang, Aging Effects in a Cu-12Al-5Ni-2Mn-1Ti Shape Memory Alloy, Metallurgical and Materials Transactions 28A, Issue 4 (1997) 955-967
• Weijia Tang and Rolf Sandström, "Thermodynamic Modeling of the Pseudo-Binary TiNi-TiCu System", To be presented in CALPHAD, Beijing, May, 1998.
• Z G Wei, R Sandström, S Miyazaki, Shape memory materials and hybrid composites for smart systems, part I: Shape memory materials, J of Materials Science 33 (1998) 3743-3762
• Z G Wei, R Sandström, S Miyazaki, Shape memory materials and hybrid composites for smart systems, part II: Shape memory composites, J of Materials Science 33 (1998) 3763-3783
• Z G Wei, Transformation relaxation and aging in a CuZnAl shape semory alloy Studied by Modulated Differential Scanning Calorimetry, Metallurgical & Materials Transactions 29A (1998) 2697-2705
• Z.G.Wei and R.Sandström: Characterization of Phase Transformations in CuZnAl Shape Memory Alloy by Modulated Differential Scanning Calorimetry, Materials Science & Engineering A273-275 (1999) 352-356.
• W Tang, B Sundman, R Sandström, C Qui, "New modelling of the B2 phase and its associated martensitic transformation in the Ti-Ni system", Acta mater. 47, No. 12 (1999) 3457-3468
• Weijia Tang, Rolf Sandström, and M. Miyazaki, "Phase equilibria in the pseudo-binary Ti0.5Ni0.5-Ti0.5Cu0.5 system", Journal of Phase Equilibria 21 No.3 (2000) 227-234.
• W Tang, R Sandström, Z G Wei, Experimental investigation and thermodynamic calculation of the Ti-Ni-Cu shape memory alloys, Metall & Met Trans 31A (2000) 2423-2430

Source of funding: KTH

Low cycle fatigue testing of aluminium alloys at elevated temperatures

Research leader: Xuexing Yao
Project period: 1997-2000
Keywords: Aluminium Alloys, Low Cycle Fatigue, Cladding, Elevated Temperature

Project description: Aluminium-manganese alloys clad with an aluminium-silicon alloy are frequently used in the manufacturing of car radiators. The assembled heat exchangers are heated to the temperature which will just melt the cladding while allowing the core to remain solid, this causes the molten cladding alloys to flow by capillary action to the joins which become structural on cooling. Thermal fatigue are important failure mechanisms in the heat exchangers. To assess the risk for thermal fatigue, low cycle fatigue testing of braze - clad aluminium was performed at ambient and at elevated temperatures.

Publications

• H Engström, R Sandström, Strain controlled fatigue testing of braze clad AA3005 at 20 and 200 C, Aluminium 74 (1998) 676-671
• X X Yao, R Sandström, Strain-controlled fatigue of a braze-clad Al-Mn-Mg alloy, Fatigue’99: Proceedings of the Seventh International Fatigue Conference, Beijing, China, Higher Education Press, China and Engineering Materials Advisory Services Ltd, UK (1999) 297-302
• X X Yao, R Sandström, T Stenqvist, Strain-controlled fatigue of a braze clad Al-Mn-Mg alloy at room temperature and at 75 and 180 C, Materials Science and Engineering A267 (1999) 1-6
• X X Yao, S Zajac, B Hutchinson, Estimation of Compressin Flow Stress from Post-Deformation Hardness in Al-Mg Alloys, Scripta Metallurgica et Materialia 41, No 3 (1999) 253-258
• X X Yao, R Sandström, Applicability of life prediction methods to the low cycle fatigue of braze clad AlMn1.0Mg0.5 alloys, International Journal of Fatigue 21 (1999) 1003-1006
• X X Yao, S Zajac, The strain-rate dependence of flow stress and work-hardening rate in three Al-Mg alloys, Scand Journal of Metallurgy vol. 29:3 (2000) 101-107
• X X Yao, S Zajac, The strain-rate Sensitivity of flow stress and work-hardening rate in a hot deformed Al-1.0Mg alloy, J of Materials Science Letters 19:9 (2000) 743-744

Source of funding: Sapa Technology; Valeo

Welded joints in aluminium structures

The project was included in the COST-506 programme: Industrial Applications of Light Alloys

Research leader: Rolf Sandström
Scientist: Joacim Hagström
Keywords: aluminium, AlMgSi, MIG, TIG, welding, thin wall, extruded, profiles, mechanical properties, fatigue, finite element
Objectives: To determine the static and dynamic strength properties of thin walled welded structures of extruded aluminium alloys.
Results: Fatigue properties of parent metal and cross weld specimens of AA6082 and AA6063were determined. The specimens were taken from MIG, TIG and friction stir welded thin walled extruded structures. Static and dynamic strengths of these structures were also measured. Guidelines for dimensioning of thin walled Al-structures were developed.

Publications:

• J Hagström, R Sandström, Fatigue properties of welded T-joints in thin-walled aluminium profiles, Materials Science Forum, Vols 217-222 (1996) 1727-1732
• J Hagström, R Sandström, Mechanical properties of welded joints in thin-walled aluminium extrusions, Science and Technology of Welding and Joining 2 (1997) 199-208
• J Hagström, R Sandström, Static and dynamic properties of joints in thin-walled aluminium extrusions, welded with different methods, Japan Institute of Light Metals, Aluminium Alloys: Their physical and mechanical properties (1998) pp. 1447-1452
• M Ericsson, R Sandström, J Hagström, Fatigue of friction stir welded AlMgSi-alloy 6082, 2nd Int Symp on Friction stir welding, Gothenburg (2000)

Source of funding: NUTEK

High temperature mechanical properties of Al-alloys

Research leader: Rolf Sandström
PhD student: Håkan Engström
Project period: 1991-1996
Keywords: Aluminium, database, creep, yield strength, standardisation
Objectives: To assess and generate creep and high temperature yield strength values for Al-alloys to be used in European standards.
Results: In collaborative project between the department and the European aluminium industry high temperature strength data were collected from the participating industries and from the open literature. The experimental data points were input in a database called HIGHTEMP.

• To take into account the time dependence of the high temperature yield strength values of Al-alloys an established evaluation method was generalised to take this dependence into account. The new method was then used to derive values at elevated temperature in relation to those at room temperature.
• Creep data were extrapolated to 30 000 h using time-temperature parameters like Larson-Miller. The proposed characteristic strength values was taken as the average of the results of four extrapolation methods. The strength values were only considered valid if the four methods gave similar results

Both the yield strength and the creep rupture strength values were used in the development of a new standard for high temperature properties of Al-alloys.

Publications:

• R Sandström, P Widestig, High Temperature Yield and Tensile Strengths of Aluminium Alloys, Aluminium, 68 (1992), pp 330-333
• H Engström, R Sandström, Evaluation of High Temperature Strength Values of Aluminium Alloys, 3rd Int. Conf. on Aluminium Alloys: Their Physical and Mechanical Properties, Trondheim I (1992) pp 249-253.
• H Engström, R Sandström, Evaluation of High Temperature Strength Values of Aluminium Alloys, Aluminium 69 (1993) 11, pp. 1007-1013
• R Sandström, Creep Rupture Data for Aluminium Alloys I, Aluminium 3 (1993) 263-268.
• R Sandström, Creep Rupture Data for Aluminium Alloys II, Aluminium 4 (1993) 361-363.
• R Sandström, Creep Rupture Data for Aluminium Alloys III, Aluminium 5 (1993) 458-461.
• R Sandström, Creep rupture strength up to 100 000 h for Aluminium Alloys, Aluminium 72 (1996) 910-917

Source of funding: NUTEK, KTH

Models for Creep Cavity Development and Rupture

Research leader: Rolf Sandström
Scientists: Rui Wu

Project period: 1993 - 1996
Keywords: Low alloy steels, 12% Cr steel, creep, cavitation, nucleation, growth, modelling, rupture

Objectives: To analyse the applicability and limits of the present models for creep cavity initiation and growth for engineering materials, to modify or develop new models, if necessary and possible, to provide a sufficiently accurate description fitting to the experimental observations, to facilitate the lifetime prediction.

Results: Experimental investigations of cavity initiation and development performed on a 12% Cr steel showed that cavities initiate at an early stage of tests. The number of cavities, the cavity size and the cavitated area fraction exhibited a continued increase with increasing strain and time. At rupture, the number of cavities took values up to about 30,000 / mm2 and the mean cavity size had a maximum value of about 2.5 µm. The cavitated area fraction was approximately 0.1% at 1% strain, 0.5% at 2% strain and 10% at rupture, respectively. The estimations of creep cavity initiation, cavity formation kinetics and growth by using modified and developed models agreed well with the experimental observations.

Publications:

• R Wu, R Sandström, J Storesund, Creep Strain Behaviour in a 12% CrMoV Steel, Materials at High Temperatures 12 (1994) 277-283
• R Wu, R Sandström, Creep Cavity Growth in Low Alloy and 12% Cr Steels, Mater. Science Techn. 11 (1995) 579-588.
• R Wu, R Sandström, Strain Dependence of Creep Cavity Nucleation in Low Alloy and 12% Cr Steels, Mater. Science Techn. 12 (1996) 405-415

Source of funding: TFR

The development of a property data bank for stainless steels with corrosion data

Research leader: Rolf Sandström
Scientists: Lai-Zhe Jin
Project period: 1991- 1996
Keywords: uniform corrosion, pitting, stress corrosion, stainless steels, evaluation, database

Objectives: To provide data in the process of systematic materials selection, and promote the application of stainless steels in mechanical design.

Results: As a part of the development of a data bank for stainless steels, data for uniform corrosion, pitting, and chloride stress corrosion were assessed. Principles of evaluation of uniform corrosion data were formulated. Assessment of uniform corrosion data was performed for 17 groups of stainless steels in about 500 corrosive media. The relative resistance to pitting corrosion for newly developed super-austenitic and duplex stainless steels, such as 654SMO, S31254, N08028 and duplex grades S32750, S31803, was identified. It was found that in the chloride solutions the Cu-rich precipitates will weaken the film. Thus the pitting resistance of copper alloyed grade was not as good as that expected. The controversial effect of titanium on pitting resistance was clarified. In dilute NaCl solution and the temperature is high, titanium seems to be beneficial; on the contrary, titanium shows its detrimental effect when testing in a high concentration of NaCl solution and the temperature is low. To clarify the responses under different test methods, SCC data collected from CaCl2 tests, autoclave tests and drop evaporation tests were evaluated. The SCC resistance of alloys for each method increased with increasing molybdenum equivalent Mo + 0.25 Cr + 0.1 Ni. For a given alloy the testing result depended on the stress state and environment. The performance of duplex stainless steels in chloride-containing environment at higher temperatures was not as good as expected if dynamic loading was involved.

Publications:

• L. Z. Jin, R. Sandström: SSSelect - An Engineering Database for Stainless Steels, Proc. Applications of Stainless Steel '92, Kista, Stockholm, (1992), H. Nordberg, J. Björklund, Eds., Jernkontoret, The Institute of Metals, ASM International, p. 822-831.
• L. Z. Jin: SSSelect - A Database Designed for Materials Selection in Corrosive Environments, Proc. Progress in the Understanding and Prevention of Corrosion, Barcelona, Spain, (1993), J. M. Costa, A. D. Mercer, Eds., The Institute of Materials, p. 387-399.
• L. Z. Jin: Assessment of Pitting and Uniform Corrosion Data for the Development of An Engineering Database, Corrosion Reviews (1995).
• L-Z Jin, The Chloride Stress Corrosion Cracking Behaviour of Stainless Steels under Different Test Methods, ASM J. Materials Engineering and Performance 3 (1994) 734-739
• L-Z Jin, Minimum Crevice Corrosion Temperature of CrNiMoN Alloys in Natural Seawater, (1994)
• L-Z Jin, SS-SELECT - A Database Designed for Materials Selection in Corrosive Environments, Roestvast Staal No 10 (1994) 15-22 (in Dutch)
• L-Z Jin, R Sandström, Evaluation of Machinability Data, Journal of Testing & Evaluation 22 (1994) 204-211
• L-Z Jin, R Sandström, Machinability Data for the Purpose of Materials Selection, Proc Materials Behaviour in Machining, Warwick, The Institute of Materials (1994) 251-271
• L-Z Jin, R Sandström, Machinability Data for Materials Selection Purpose, Materials & Design 15 (1995) 339-346

Source of funding: Scandinavian Stainless Steel Industry, NUTEK

Use of shape memory alloys

Research leader: Rolf Sandström
Scientists: Weijia Tang
Project period: 1991 - 1996
Keywords: shape memory, superelasticity, TiNi alloy, database

Objectives: To develop a property database for shape memory alloys' applications and to evaluate important SMA properties under various conditions critical to engineering design.

Results: A property database on TiNi SMAs wasdeveloped and a user interface was built with pop-up menus which allowed easy access to the database. Published data on TiNi alloys were assessed with the emphasis on transformation temperatures, stress rate, recovery stress, recovery strain and superelastic behaviour as well as their changes with thermal and stress cycling. It was found that TiNi alloys with lower initial Ms and the R-phase transition were more stable against cycling. Furthermore constitutive equations for TiNi alloys were studied by relating material parameters in the equations to experimental information. Thermodynamic analysis was performed for the martensitic transformation in Ni-Ti system.

Publications:

• Weijia Tang, Jan Cederström, and Rolf Sandström, Property database for the development of shape memory alloy applications, J. de physique IV, C4, 1, Nov. (1991) 129-134.
• Weijia Tang, and Rolf Sandström, Integration and analysis of Property data on shape memory alloys for engineering design, Fourth International Symposium on Computerisation and Use of Materials Property Data, Oct. 6-8, 1993, Gaithersburg, Maryland, the United States.
• W Tang, R Sandström, On the Material Parameters in the Constitutive Relation for Shape Memory Alloys, Symp on Why, When and How to Use Shape Memory Alloys, Saltsjöbaden (1993)
• W Tang, R Sandström, Analysis of the Influence of Cycling on TiNi Shape Memory Alloy Properties, Materials and Design 14 (1993), pp 103-113
• V A Likhachev, R Sandström, W Tang, J Cederström, Shape Memory Alloy Database Systems, Int. Conf. Shape Memory and Superelasticity: Engineering and Biomedical Applications, Pacific Grove, USA (1994) 121-132
• W Tang, B Bergman, On the Formation of Al2O3-Al composite by directed oxidation of molten metals, Mat. Science Eng. A177 (1994) 135-142
• W Tang, R Sandström, Selection of the Material Parameters in the Constitutive Relations for Shape Memory Alloys, Int. Symp. Shape Memory Materials, Beijing (1994) pp 535-540
• W Tang, R Sandström, Materials parameters in constitutive relations for TiNi alloys, J of Applied Biomechanics (1995)
• W Tang, R Sandström, The transformation tensor and the constitutive relations for TiNi shape memory alloys, subm, for publ.
• W Tang, R Sandström, Limitations of constitutive relations for TiNi shape memory alloys, Int Conf Matrensitic Transformations, Lausanne (1995)
• W Tang, R Sandström, Property Database on Shape Memory Alloys for Engineering Design, Computerization and Networking of Materials Databases 4, ASTM STP 1257, Eds. C P Sturrock and E F Beagley (1995) 85-95

Source of funding: STU, NUTEK

Design of high temperature plants with respect to creep

Research leader: Åke Samuelson
Scientists: Åke Samuelson, Rolf Sandström, Peter Segle, Jan Storesund and Rui Wu
Project period: 1991 - 1995
Keywords: design, weldments, creep, creep damage, cavities

Project description: To improve the creep design code for pressure vessel and piping components, the influence on creep life due to mismatch in creep properties between parent and weld metal was investigated and it was shown that it has to be considered in an improved creep design code. Reduction factors due to weldments was been suggested. The understanding of creep damage evolution in weldments was studied and further understood. The size effect of creep tested cross-weld specimens was verified by numerical simulations. Design diagrams for bends working in the creep regime was suggested.

Publications:

• Storesund, J., Tu, S.-T. and Wu, R.: A study of the stress distribution in uniaxial cross weld creep test specimens, Contribution to the Int. Symposium on Life and Performance of High Temperature Materials and Structures, Tallinn, Estonia, (1992)
• Segle, P.: Development of design diagrams for bends working in the creep regime using rigorous creep analysis, ASME-Conf., PVP-Vol. 264 (1993) pp 45-50
• S-T Tu, Some Aspects of the Evaluation of Irregularly Oriented Crack-Like Defects, Int. J. Pres. Ves. & Piping, 52 (1991), pp 11-24.
• S-T Tu, R Sandström, The Evaluation of Weldment Creep Reduction Factors by Experimental and Numerical Simulation, Workshop on Modelling High Temperature Structure Performance of Engineering Materials, Basingstoke, England, November 1991.
• L Å Samuelson, P Segle, J Storesund, S-T Tu, Design of Pipes with Circumferential Welds in the Creep Range, Conf. Assessment of Residual Service Life, Mannheim (1992).
• L Å Samuelson, P Segle, S-T Tu, Design of Weldments in Structures Subjected to Creep, Proc. IUTAM Symp. on Mechanical Effects of Welding, Eds L. Karlsson, L.E. Lindgren, M. Jönsson, Springer (1992), pp 223-230.
• L Å Samuelson, P Segle, S-T Tu, Design of Welded Joints Subjected to High Temperature Creep; Stress Classification, Robust Methods and Elevated Temperature Design, ASME, PVP Vol 230 (1992), pp 1-6.
• L Å Samuelson, S-T Tu, J Storesund, Life Reduction in High Temperature Structures due to Mis- Match of Weld and Parent Material Creep Properties, Int. Symp on Mis-Matching of Welds, Lüneburg (1993)
• S-T Tu, P Segle, L Å Samuelson, Some Aspects of the Design of Welded Structures Subjected to High Temperature Creep , High Temp. Service & Time Dependent Failure ASME (1993) PVP-Vol 262
• S-T Tu, R Sandström, Numerical Simulation of Creep Exhaustion of Weldments and Some Design Considerations, 5th Int. Conf on Creep and Fracture of Engineering Materials and Structures, Swansea, Institute of Materials, (1993) pp 695-704
• S-T Tu, S-H Dai, Engineering Assessment of Fatigue Growth of Irregularly Oriented Multiple Cracks, submitted for publication in Int J Fatigue and Fracture of Engineering Materials and Structures (1993)
• Y-L Wang, F-Z Shen, S-T Tu, A Study of Creep Crack Propagation of HK40 Furnace Tubes with C- shaped Specimens, submitted for publication in Engineering Fracture Mechanics (1993)
• R Sandström, S-T Tu, The Effect of Multiaxility on the Evaluation of Weldment Strength Reduction Factors in High Temperature Creep, Accepted for publ. in Trans ASME J Pres. Ves. Techn. 76 (1994) pp 76-80
• S-T Tu, R Sandström, The Evaluation of Weldment Creep Strength Reduction Factors by Experimental and Numerical Simulations, Int. J Pres. Ves. & Pip. 57 (1994) pp 335-344
• S-T Tu, R Wu, R Sandström, Design Against Creep Failure for Weldments in 0.5Cr0.5Mo0.25V Pipe, Int. J Pres. Ves. & Pip. 58 (1994) 345-354
• L Å Samuelson, P Segle, J Storesund, Life Assessment of Repaired Welds in High Temperature Applications, EPRI Int. Conf Weld and Repair Technology for Fossil Power Plants, Williamsburg, March 1994
• S-T Tu, S-H Dai, An Engineering Assessment of Fatigue Growth of Irregularly Oriented Multiple Cracks, Fatigue and Fracture of Engineering Materials and Structures 17 (1994) 1235-1246
• J Storesund, S-T Tu, Geomtrical effects on creep in cross weld specimens, Int. J. Press. Ves. & Piping 62 (1995) 179-193
• R Wu, R Sandström, J Storesund, Creep damage development in weldments in a main steam pipe system made of 0.5Cr0.5Mo0.25V and 2.25Cr1Mo steel, Baltica III, Proc Int Conf Plant condition and life management I, Helsinki-Stockholm (1995) 119-134

Source of funding: NUTEK, AMFO, SA, MKV, ABB-Carbon, Vattenfall, Stockholm Energi

Physical properties of aluminium alloys

Research Leader: Rolf Sandström
PhD-student: Páll Ólafsson
Scientist: Åke Karlsson
Project period: 1992- 1995
Keywords: Material databases, Electrical conductivity, Thermal conductivity

Objectives: Collection and evaluation of experimental data on physical properties of Aluminium and comparison to values in the database ALUSELECT.

Results: Experimental data on electrical and thermal conductivity of 200, respectively 300 alloys and conditions were collected into a database. A calculation model for calculating the electrical resistivity from composition and temper condition was proposed using Mathiesen's rule and phase diagrams. The model proved to be useful for comparing the resistivity of different alloys and for calculating the electrical resistivity for most alloy groups within 3 n*m. Suggestion were made for minor changes in resistivity of several alloys in ALUSELECT.

Publications:

• P Ólafsson, R Sandström, Å Karlsson, Electrical conductivity of aluminium alloys, Materials Science Forum, Vols 217-222 (1996) 981-986
• P Ólafsson, R Sandström, Å Karlsson,, Comparison of experimental, calculated and observed values for electrical and thermal conductivity of aluminiums alloys, J of Materials Science 32 (1997) 4383-90
• P Ólafsson, R Sandström, Calculations of the electrical resistivity of AlCu- and AlMgSi-alloys, Materials Science and Technology, Vol. 17 (2001) 655-662

Source of funding: NUTEK

Usage of aluminium matrix composites

Research leader: Rolf Sandström

PhD-students: Johan Eliasson, Anna Årmann
Project period: 1990-1995
Keywords: Metal matrix composite, aluminium, material optimisation, merit parameter, application

Objectives: To collect published property data and put in to a database, to analyse applications of metal composites, to develop a methodology for the selection of metal composites and to perform materials optimisation for components made by Al-composites.

Results: Mechanical property data was collected and put in to a database called Al-select MMC. A methodology for the selection of Al- composites was developed. It was concluded that saving weight was of importance for the selection of these materials. The model contains a parameter that takes the value of weight saving into consideration. Primarily particulate reinforced Al- composites was analysed. They will be competitive with conventional materials in mainly aeroplanes and aerospace, but may also be interesting in the automotive industry. Another important application field is sport equipment. The model was applied to a driveshaft. However, during the collection of data it was discovered that a lot of data was not fully characterised. This makes the use of existing data less valuable to the designer, and there will be difficulties in introducing the materials to a larger scale in the industry.

Publications:

• A Årmann, R Sandström: Property database on aluminium matrix composites, 12th Risö International Symposium on Materials Science (1991), 637-642
• J Eliasson, R Sandström: Analysis of the coherence of published data on aluminium matrix composites, Conference on the intelligent selection of materials problems and solutions, Nov. 1993, The Institute of Materials, London, UK
• J Eliasson, R Sandström, The role of the value of weight savings in the use of aluminium matrix composites , Proc 4th Int conf Aluminium alloys. Their physical and mechanical properties II, Atlanta (1994) 535-542
• J Eliasson, R Sandström, Application of Aluminium Matrix Composites, Key engineering materials 104-107 (1995) 3-36
• J Eliasson, R Sandström, Analysis of the coherence of published data on aluminium matrix composites, J Testing Evaluation 23 (1995) 288-294
• J Eliasson, R Sandström, Materials selection and grade optimization applied to aluminium matrix composites, J Mat Eng Performance 4 (1995) 358-367

Source of funding: STU, NUTEK

System for the design of aluminium alloy components

Research Leader: Rolf Sandström
PhD-student: Joacim Hagström
Project period: 1990 1994
Keywords: Aluminium, database, materials properties materials selection, materials optimisation, education

Objectives: Develop theories for materials selection and systematise information for the implementation into a materials properties database. Create data structures and logical schema for the database system

Results: A materials property database system for the systematise selection of materials (aluminium alloys)was developed successfully. The system also contained conventional methods for materials selection, mainly for educational reasons and to enable the comparison of the methods. It was determined that the conventional methods, mainly based on weighting of properties, were not incrementally stabile and could give erroneous results. Theories for the pre-selection of materials groups has been studied and plans for a computerised system has been proposed. The effect of non-existing or non-available information on materials selectionwas studied.

Publications:

• Hagström, J., and Sandström, R., MATEDS - MAterials Technology EDucation System. A System for Materials Science Education and Materials Selection Computerisation and Networking of Materials Databases: Third Volume, ASTM STP 1140, Thomas I. Barry and Keith W Reynard, Eds., American Society for Testing and Materials, Philadelphia, (1992), pp. 472-486.
• Hagström, J., and Sandström, R., Pre-Selection of Material Groups Using a Material Property Database System, The third International Symposium on Aluminium Alloys, Trondheim, Norway, (1992).
• Hagström, J., and Sandström, R., Use of Incomplete Sets of Materials Property Data for Materials Selection Purposes, (1994).

Source of funding: SkanAluminium