Projects / Programmes
Numerical and Experimental Analysis Mechanical Systems
January 1, 2017
- December 31, 2021
| Code |
Science |
Field |
Subfield |
| 2.05.00 |
Engineering sciences and technologies |
Mechanics |
|
| 2.04.00 |
Engineering sciences and technologies |
Materials science and technology |
|
| Code |
Science |
Field |
| T150 |
Technological sciences |
Material technology |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
| 2.05 |
Engineering and Technology |
Materials engineering |
High fatigue and fracture resistance of heterogeneous materials, optimization of structure topology, monitoring of surface degradation process by using optical fiber senzors
Researchers (15)
Organisations (1)
Abstract
The complexity of the fatigue failure process is related to changes in materials and its sensitivity to many factors, including the loading type, microstructure, material heterogeneity and environmental conditions among other factors. The investigation carried out within the frame of the programme group shows that fatigue lifetime is possible to extent more than 10 times. Higher fracture resistance is also possible to achieve by appropriate use of heterogeneous materials and efficient combining of their properties. Mechanical systems, as engineering structures, mechanisms and engines, are exposed to dynamical loads. This loads caused change on material’s surface and under surface of materials. It has been proved that process of fatigue crack initiation and crack growth follows changes on surface. The mechanisms of material’s surface degradation are going to analysed in cooperation with Laboratory for optical sensors (Faculty of Electricity Engineering and Computer Science at University of Maribor). The fibre Bragg gating (FBG) as optical sensor with more than 2000 reflected mirrors in length of 1 mm. It makes possible to measure strain on micro level of metal grain size. On the base of change in reflected spectre is possible to use sensors for monitoring the mechanical performance of the material’s surface vs. number of loading cycles. The performed pilot investigations show that change in optical spectre of FBG sensors is consequence of change of surface strain redistribution and roughness induced by surface micro crack closure. The change of FBG sensors spectre can be also consequence of creep process as interaction of different modulus of elasticity and thermal extension, as system of elastic heterogeneous behaviour materials. It is found from the pilot monitoring study that significant surface roughness changes occurred at the beginning fatigue process and at the end of life time, but during most of fatigue life the roughness is statistically determined as linear regarding to mean values and standard deviation. In the next programme’s investigation cycle the more attention is going to attempt to change of FBG sensors spectre vs. surface roughness change. Structural components will be optimized regarding to minimum mass, Eigen frequencies, reduction of stress concentration and determine suitable place for FBG sensor mounting. It makes possible to monitoring strain on only one single critical place of structure. Monitoring of behaviour during service and damage process ensure safe service and efficient use of structure. Research programme consist development of system for measurement of cyclic strain on microscopic level in order to determine and monitoring of material’s surface conditions change. Result of project is going to be methods and system for on-line monitoring of critical components in transport techniques, aerospace and aircraft systems to prevent failure.
Significance for science
Research objectives are the development and the analysis of the numerical model for the transfer of deformation between different stress systems and experimentally validate obtained reflection spectre by using FBG sensor. Original contribution is represented by the study of material surface conditions and influence of the residual stresses to the response of the measured FBG sensor signal throughout highly cyclical loading. The development of the stress-deformation model and model for distribution of deformation energy through heterogeneous multilayer structures presents important contribution to understanding of behaviour of heterogeneous structures with the aim to provide higher resistance to the crack’s initialization and to increase fatigue resistance of the material. This topic opens new research horizons in technology and production of multilayer heterogeneous structures as well as in development and application of FBG sensors on the components in aerospace technology. Research on the optical FBG sensor usage is also actively performed on other technologically highly developed institutions and universities in the world. It is evident from the published contributions that considerable effort is invested on the aerospace technology applications. However, the influence of the surface conditions, especially metallic ones, on the change of FBG sensor response has not been analysed. The deformation energy transition through different heterogeneous multilayers were numerically modelled and analysed but not exactly measured yet, as well. For optimised components a critical stress region, essential for integrity and lifespan, is determined. Established Application of on-line system for health monitoring of optimized structure gives additional impact to immediately industrial application. Previous research activities were performed only on the conventional non-optimised components, which makes proposed research even more appropriate for aerospace technology. Processing of FBG signal on critical parts of optimised component enables direct monitoring of the degradation process and therefore lifespan of the component. With optimisation of the component not only geometry but also number of FBG sensors can be optimised, and therefore quantity of data to be analysed and response time can be optimised too. With the use of FBG sensors in multilayer materials, tracking the transfer of the deformation energy between individual layers of heterogeneous materials will be possible. Thus, condition and identified mechanisms of the deformation transfer between heterogeneous layers of material during high cyclical fatigue will be determined.
Significance for the country
Proposed research program is unique in Slovenia and internationally comparable. It is based on comparative advantages that are comparable and stand out from the already used application on the field of the structural component optimisation. The founded results will contribute to the increase of the loading bearing capacity and higher fatigue limit of the structures with the use of the heterogeneous multi-layered materials.. With sensor technique FBG application one obtains new dimension in quantitative and qualitative continuous monitoring of the optimised construction components and consequently direct verification of the existing results. Research program is based on 3D numerical models that can be easily and quickly adopted to modern manufacturing processes of larger production systems. Even intermediate results of the research program can be transplanted into the high loaded components, such are carriers in the general machine building or transport industry (crane, cars, aircraft). The transfer of the research program results in the industry should be supported with additional specialist training, which will be performed by members of the program group. Thereby, new internationally comparable knowledge via workshop or seminars will be transferred into industry, contributing to larger added value of the products in the national metal and automotive industry.
Most important scientific results
Interim report
Most important socioeconomically and culturally relevant results
Interim report
