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FATIGUE LIFE PREDICTION OF STRUCTURAL COMPONENTS UNDER COMPLEX SERVICE LOADING

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The results of this study can be divided into the 3 areas of new data, lifetime prediction algorithms and software and improved understanding of damage processes in mechanical components.

Deformation behaviour and fatigue properties have been examined for a range of materials including mild steel, alloy steels, quench and tempered steels, microalloyed steels, pearlitic SG iron and aluminium alloy. Some information is also available on the fatigue effects of surface conditions, loading modes and anisotropy.

A range of new algorithms have been proposed or validated for durability assessment of structural components including:
modelling of deformation behaviour around notches;
modelling of deformation behaviour and endurance under biaxial loading;
verification of damage accumulation rules under variable amplitude and mean stresses;
modelling effect of shotpeening and induction hardening;
formulation of rules for the elimination of minor cycles from variable amplitude loading histories.
The software generated was largely of an experimental nature to verify some of the algorithms.

The better understanding of damage processes in structural components, which has been achieved, can be exploited for:
in house training for design and development staff;
formalising company methodology for failure prevention;
highlighting shortcomings in the existing technology for durability and reliability assessment.

It is anticipated that the development and improvement of Fatigue Life Prediction methods achieved in this work will bring the following benefits:
Optimized designs with better utilization of materials and manufacturing processes. Weight reductions of the order of 10 percent are considered attainable.
Shorter lead times. It is envisaged that integration of more rigorous liftime assessment methods in the existing design methodology should translate into a reduction in the design lead times of the order of 20 to 50 times.
Sharing of skills between experts in material, design, test and manufacturing areas, thereby eliminating errors resulting from oversights and poor communication. Typically a design change to an already tooled part can be as much as 30 to 50 times more expensive to implement than changes at early stages of design.

A range of new algorithms has been proposed or validated as part of an overall methodology for durability assessment of automotive structural components. The range includes modelling of deformation behaviour around notches, under biaxial loading; damage accumulation rules under variable amplitude and mean stresses; modelling the effects of shotpeening and induction hardening and formulation of rules for the elimination of minor cycles from amplitude loading.

The principle objective of the project was to develop, improve and validate Fatigue Life Prediction methods suitable for design applications for automotive structural components. The procedure adopted was the local strain or critical location approach, which models the cyclic, elastic/plastic material behaviour in a given potential site of failure. This provides a criterion for calculating local fatigue damage under variable complitude stresses.

The expected economic benefits of using a common approach are a weight reduction of 10 percent due to optimized design, and a reduction in design lead times of 20 to 50 percent.
THE MAIN OBJECTIVE OF THE PRESENT COLLABORATIVE PROJECT IS TO IMPROVE COMPUTER BASED FATIGUE LIFE PREDICTION (F.L.P.) METHODS, CONSIDERING IN PARTICULAR APPLICATIONS TO STRUCTURAL COMPONENTS TYPICAL OF THE AUTOMOTIVE FIELD.
THE BASIC PROCEDURE ADOPTED IN THE RESEARCH PROGRAMME IS THE SO CALLED "LOCAL STRAIN APPROACH", WHICH MODELS THE CYCLIC ELASTIC-PLASTIC MATERIAL BEHAVIOUR AT AN IDENTIFIED POTENTIAL SITE OF FAILURE AND PROVIDES A CRITERION FOR CALCULATING THE LOCAL FATIGUE DAMAGE ACCUMULATED UNDER RANDOM SERVICE LOADING.
THE ADDITIONAL AIM IS TO EXTEND THE LIFE PREDICTION METHODS TO STRUCTURAL CONDITIONS INVOLVING SURFACE HARDENED MATERIALS-COMPONENTS AND MULTIAXIAL STRESS CONDITIONS.

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CSC - Cost-sharing contracts

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CENTRO RICERCHE FIAT S.C.P.A
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Letzte Aktualisierung: 4 September 2022

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Permalink: https://cordis.europa.eu/project/id/RI1B0089/de

European Union, 2024