Research activities

Structural integrity

The area covers conditions affecting strength and wear life of mechanical constructions. This includes calculation of mechanical, thermical and chemical stress which affect structures, and dimentioning for all kinds of constructional failure (fracture, wear, fatigue, corrosion, etc.)

Sub-areas of structural integrity:

Fracture and damage mechanics
By materials testing and numerical calculations we aim to identify mechanisms of damage, fracture and collapse in materials components and joined structures. In particular, we study welded joints. Use of FEM coupled with mechanical and micromechanical models form the basis for more accurate and cost-effective procedures for evaluation of design, performance characteristics and the safety level of load-carrying structures.

SMASH project - learning environment for materials technology in the new millennium: In 5 years, the Materials Technology Educational Programme shall become as popular as Product Design. This is to be achieved by making the programme so exciting that the students themselves make sure "everybody" gets the word. Focus: Materials technology has a substantial image problem. The name is considered a thing of the past. The plan is to create a completely new learning environment for materials technology, where moths and mould and all that resembles the post-war era is washed away (like a white tornado) and replaced with new content, new attitudes, new environment. Materials technology is a national strategic area. Industry and society expect of NTNU good and excellent candidates who are motivated for making an effort to create the society of the future. This applies to both the established and the non-established industry, and unites existing methodology with all the new knowledge to come. » Participants Christian Thaulow

LINKftr project: The founding idea of the firm LINKftr is a result of a long-standing integrated collaboration between SINTEF and NTNU on the area of Fracture Mechanics and Materials Testing. The goal of establishing this firm is to create a new actor in the borderland between materials technology expertise and the engineers/designers of the industry. With the new firm, we have established a more precise definition of roles between commercialisation/software development (LINKftr), connected research tasks (SINTEF), and Master/PhD education (NTNU). This will enable an increased attention to complete solutions, which the parties can contribute to and benefit from. » Participants Christian Thaulow

Mechanical Integrity
The subject area covers methods for the analysis of stress and strain in mechanical components and their assessment with regard to the strength and lifetime of the components, in particular under fatigue loading. Structural and material mechanics and mechanical metallurgy form the scientific basis. Mechanical integrity offers methods of analysis and design rules for the development and design of machinery and other mechanical equipment. The area focuses on the development of methods and rules for the finite element analysis of mechanical components and the associated prediction of the strength and lifetime of these. Such methods and rules are prerequisites for the optimisation of components, i.e. their reliable and economical operation during the intended lifetime using the right quality and amount of materials.

Mechanical integrity of hydraulic turbines: The project deals with the fatigue design of hydraulic turbines, especially Francis turbine runners. The stress distribution at the transition between blade and boss is computed and optimised by means of the finite element method. This method is also used to characterise a semi-elliptical surface crack in an arbitrary stress field. By combining the results from both analyses, the growth of a fatigue crack at the transition between blade and boss can be simulated. Predictions are compared with results from fatigue testing of realistic specimens. Thus, a full-scale model of the trailing edge of a Francis blade has been investigated in a 100-tonne fatigue test rig.
»Participants: Hans-Jörg Huth , Gunnar Härkegård

Life assessment and design criteria for welded light-alloy components
The project is part of the NUTS program and deals with the fatigue design of welded light alloy automotive components. Besides conventional methods (nominal stress, structural stress) and standards (Eurocode 9), probabilistic methods (Weibull analysis) and crack growth analysis are being used for the lifetime prediction of representative welded joints between (extruded) box beams. Participants: Torsten Mann , Gunnar Härkegård

Probabilistic fatigue design This project deals with the prediction of the probability of fatigue failure of a machine component based on the probability of failure of a small volume element described by the Weibull distribution function (“weakest-link theory”). An existing computer code for the post-processing of a finite element stress field has been used for this purpose. Predictions for fatigue test specimens are compared with experimental data. Participants: Arne Fjeldstad , Gunnar Härkegård

Non-linear analysis of crack in notched component This work is aimed at the computation of the path-independent integral J for a crack in a notched component. This is of importance to the analysis of the growth of a fatigue crack under elastic-plastic conditions. While earlier work has been focused on components under force control, the present work specifically deals with components under displacement control, a situation representative of thermally loaded components, e.g. thermal power plant or process plant. Participants: Anders Wormsen , Gunnar Härkegård