•Multiaxial random experimental fatigue tests realized with a new specimen geometry are presented.•The proposed specimens' modal approach was numerically and experimentally validated.•The ...experimental results data are compared with that came from the proposed BVM method.•Fractography analyses of the tested specimens were performed.
Multiaxial random experimental fatigue tests realized with a new specimen geometry are presented. Setting the circular specimen, it was possible to test ASTM A-105 material with a frequency resonance system. The proposed specimens' modal approach was numerically and experimentally validated. The goal of this work was to demonstrate to be able to define the Wöhler curve of the component made, using forecasts data came from the proposed BVM method. To complete the investigation, fractography analyses of the tested specimens were performed.
Abstract
The health monitoring of mechanical components and systems is a technique known and applied for decades in almost all fields of engineering since it allows a drastic reduction of the risks ...associated with any unexpected failure of components and at the same time allows reducing the plant maintenance and management costs. Several monitoring techniques exists and all of them are based on the acquisition and processing on-field measurements aimed to evaluate possible changes in the behavior of the component. Among these, in recent years a method able to monitor in real-time the fatigue damage or the potential damage of a structure with few information has been developed. In this paper, this method, implemented and tested only numerically, has been implemented in an acquisition board, expressly developed, and its ability to operate in real-time by monitoring the failure of a real component subjected to random vibrations has been tested.
The Italian Association for Stress Analysis (AIAS) was founded in 1971 by researchers from academia, research centers and industry. AIAS was intended as a community where to discuss, to share and to ...develop scientific knowledge related to all technical aspects of stress analysis. In the years, from an initial focus on experimental techniques, AIAS contributed considerably to the development of modern numerical methods and computational techniques for the mechanical engineering design. In 2015, AIAS turned in the Italian Scientific Society of Mechanical Engineering Design.Today, AIAS is an institutional partner that supports the instances from academia in subject area of the mechanical engineering design. Every year, AIAS organizes a technical conference offering the possibility to present research updates, share new ideas and foster collaborations. The AIAS conference has become a fundamental event for all those interested in current developments in mechanical engineering design and stress analysis, where to meet researchers, testing equipment and software developers.The 50th AIAS Conference edition was initially re-scheduled to be held in Genoa, Italy after it was switched as virtual conference in 2020 due to COVID-19 emergency. Unfortunately, due to the continuing pandemic emergency, it was decided to go virtual again to keep continuity with the tradition, confident that, despite the difficulties of the moment, united we stand.As for the previous year, the response of researchers and students has been outstanding: over 180 oral contribution have been presented in synchronous, during the three days of the conference, with three simultaneous parallel sessions. In addition to the thematic sessions on AIAS traditional subjects, special sessions on additive manufacturing, energetic methods for structural analysis and smart materials and MEMS have been successfully organized with the contribution of the AIAS technical committees.Among all contributions presented at the conference, 54 have been selected to be published after peer review, in this volume. This was made possible thanks to the active participation of all AIAS members, to the work of the AIAS Scientific Committee and Conference Papers Review panel (Profs Giovanni Meneghetti, AIAS Scientific Coordinator, Luciano Afferrante, Francesco Bucchi, Filippo Cianetti, Enrico Armentani, Marco Sasso). Their outstanding contribution is gratefully acknowledged.List of Disclaimer, Editors, Scientific Committee are available in this pdf.
The Italian Association for Stress Analysis (AIAS) was founded in 1971 by researchers from academia, research centers and industry. AIAS was intended as a community where to discuss, to share and to ...develop scientific knowledge related to all technical aspects of stress analysis. In the years, from an initial focus on experimental techniques, AIAS contributed considerably to the development of modern numerical methods and computational techniques for the mechanical engineering design. In 2015, AIAS turned in the Italian Scientific Society of Mechanical Engineering Design.
Today, AIAS is an institutional partner that supports the instances from academia in subject area of the mechanical engineering design. Every year, AIAS organizes a technical conference offering the possibility to present research updates, share new ideas and foster collaborations. The AIAS conference has become a fundamental event for all those interested in current developments in mechanical engineering design and stress analysis, where to meet researchers, testing equipment and software developers.
The 50th AIAS Conference edition was initially re-scheduled to be held in Genoa, Italy after it was switched as virtual conference in 2020 due to COVID-19 emergency. Unfortunately, due to the continuing pandemic emergency, it was decided to go virtual again to keep continuity with the tradition, confident that, despite the difficulties of the moment, united we stand.
As for the previous year, the response of researchers and students has been outstanding: over 180 oral contribution have been presented in synchronous, during the three days of the conference, with three simultaneous parallel sessions. In addition to the thematic sessions on AIAS traditional subjects, special sessions on
additive manufacturing, energetic methods for structural analysis
and
smart materials and MEMS
have been successfully organized with the contribution of the AIAS technical committees.
Among all contributions presented at the conference, 54 have been selected to be published after peer review, in this volume. This was made possible thanks to the active participation of all AIAS members, to the work of the AIAS Scientific Committee and Conference Papers Review panel (Profs Giovanni Meneghetti, AIAS Scientific Coordinator, Luciano Afferrante, Francesco Bucchi, Filippo Cianetti, Enrico Armentani, Marco Sasso). Their outstanding contribution is gratefully acknowledged.
List of Disclaimer, Editors, Scientific Committee are available in this pdf.
Abstract
Composite sandwich panels have a vast heritage and are commonly employed in various fields. The space industry is not an exception and often space structures and experiments use this type of ...panels. This paper represents an effort toward the development of a design procedure for space-born sandwich panels. The here-presented work has been performed on a real test case: the structural sandwich panel of a scientific space mission. In this preliminary phase, classical methodologies were used to ensure the satisfaction of the mechanical requirements and for the minimization of the panel mass and dimensions. Tools such as Finite Element (FE) were employed to help with the design. Increasingly detailed models were developed and used to design the space panels. In addition, this work describes the future roadmap of the project.
An obstacle to the diffusion of additive technology is the difficulty of predicting the residual stresses introduced during the fabrication process. This problem has a considerable practical interest ...as evidenced by the abundant literature on residual stresses and distortion induced by the SLM (Selective Laser Melting) and EBAM (Electron Beam Additive Manufacturing).
The purpose of this paper is to evaluate the effect of different process parameters on the heat distribution and residual stresses in components made with SLM technique. Three aspects are developed and illustrated: a) thermomechanical modeling of the growth process, based on Finite Elements (FE), which considers changes in the behavior of the material (powder→liquid→solid) through the finite element “birth” and “death” technique that enables the progressive activation of the elements as the component grows; b) sensitivity analysis of the model to the physical characteristics of the material (conductivity, specific heat capacity, Young’s modulus). This is an important aspect allowing to focus on the most significant parameters to be determined experimentally with high reliability; c) evaluation of the effects of different process parameters (laser power, scan speed, overlap between adjacent paths) on the process.
The article illustrates the theoretical thermal model and the detail of the strategy used in the FE analysis. The most influential characteristics of the material are highlighted and, finally, general criteria for choosing the optimal combination of process parameters to limit the residual stresses are provided.
Spectral decomposition of a PSD into narrow frequency bands has been suggested as a promising way for estimating the fatigue damage of uniaxial wide-band random loadings. The basic idea has been ...formulated in some recent publications, which also proposed different combination rules to sum up the damage of each narrow frequency band. The purpose of this technical note is to clarify the analogies, relationships and differences among the approaches developed in such publications.
In the present paper the authors define an original analytical expression of a corrective coefficient to evaluate fatigue damage induced by a non-Gaussian stress state affected by high Kurtosis ...(values higher than 5) and by zero Skewness.
This approach starts from a previous activity in which the authors solved an analogous problem but for light non-Gaussian stress states (Kurtosis value less than 5).
The proposed procedure assumes to know the fatigue damage induced by Gaussian equivalent stress state time domain process. This characteristic allows the proposed procedure to be easily adopted inside the so-called Frequency Domain Fatigue Methods but in parallel with the statistical analysis of the system time domain response (Kurtosis and Skewness evaluation).
Interesting considerations about its applicability will be proposed as concerns the non-Gaussianity and non-Stationarity of the inputs when the system is a flexible component excited in its frequency range.
The use of the frequency domain approach in the virtual estimation of mechanical component fatigue life under random loads is related to two conditions regarding the dynamic behaviour of components ...and the state of stress. The mechanical system must have linear behaviour and the probability density function of stress must be Gaussian, respectively. Obviously, these conditions are not independent, because there is a close tie between the transformations induced by the system to the random inputs and stress distribution.
The rigorous procedure for the extension of these hypotheses is not available and only approximated approaches can be used: normally these are based on a corrective coefficient to the narrow-band formula.
The main goal of this report is to suggest a separation of the effects on the corrective coefficient. In this manner, the global coefficient can be seen as the product between a partial coefficient related only to the wide-band effects of stress power spectral density function and another one dependent on non-normality indices of stress probability density function. A meaningful application has been investigated to validate the practical employment of this approach. By this example the authors also defined an original analytical expression of a corrective coefficient for Gaussian damage; however, the formulation has to be improved by other applications, because its validity is tested only on a too much limited domain of Kurtosis values. Moreover, the authors suggest that a modal approach to the stress recovery procedure of a flexible body might be an interesting way to the rapid identification of non-Gaussianity indices in the analysis of frequency and time domain dynamics. For this reason, they believe that the investigation of tying the stress non-Gaussianity to the non-Gaussianity of the component modal coordinates to be useful.
PDF
