Umberto Meneghetti

Crack Localization in Stepped Beams

A method for crack localization, based on so-called Local Modal Crack Sensitivity (LMCS), has recently been proposed by one of the Authors. As a major feature, the method only involves measuring eigenfrequencies. The method has already been used for beams of uniform cross section and homogeneous boundary conditions. In this paper, the method is extended to stepped beams, with both homogeneous and non-homogeneous boundary conditions. Experimental results confirm its usefulness for crack localization. Satisfactory localization of a second crack was also possible, so confirming the effectiveness of the method.

Crack localization in non‐rotating shafts coupled to elastic foundation using sensitivity analysis techniques

The problem of damage and crack detection in structural components has acquired an important role in recent years. Since the presence of cracks in a structure may alter its vibrational characteristics, the estimation of such variations can be used to detect cracks and damage, and to monitor the integrity of structures. The use of fast, easy and inexpensive non‐destructive testing is thus a major task. In this paper, sensitivity analysis by measurement of the reduction of eigenfrequencies was utilized to localize a crack in a non‐rotating shaft coupled to an elastic foundation. The shaft was modeled by the finite element method and coupled to an experimentally identified foundation model. The detection of a crack with different depths and orientations was verified experimentally and a good agreement between actual and detected crack positions was achieved. Finally easiness, effectiveness, applicability of the method and its extensions are also shown.

Undicesima giornata di studio Ettore Funaioli – 21 luglio 2017

In questo volume sono raccolte le memorie presentate in occasione della “Undicesima Giornata di Studio Ettore Funaioli”, che si e svolta il 21 luglio 2017 presso la Scuola di Ingegneria e Architettura dell’Alma Mater Studiorum – Universita di Bologna. La Giornata e stata organizzata dagli ex allievi del Prof. Ettore Funaioli con la collaborazione del DIN – Dipartimento di Ingegneria Industriale e della Scuola di Ingegneria e Architettura dell’Alma Mater Studiorum – Universita di Bologna, e con il patrocinio dell’Accademia delle Scienze dell’Istituto di Bologna e del GMA – Gruppo di Meccanica Applicata.

Dynamic Analysis of an Ancient Tilt-Hammer

In the first centuries of the second Millennium A. D., a sort of industrial revolution took place in Western Europe and many new machines were introduced. After this phase, there was stagnation in new machine appearance for a long time. Progresses in technology, however, did not cease but continued till the 18th century, when the Industrial Revolution exploded and the great growth in technology took place. Before this last event, the evolution of technology consisted more of updating of existing solutions than of introducing basic innovations. Nonetheless, from the early Middle Ages onwards engineers were able to advance many machines to a notable level of complexity and technological sophistication, showing considerable skill and power of observation. As an example, this paper describes a tilt hammer. The evolution of this machine is briefly depicted, and a particular hammer is then looked at, which presents non straightforward dynamical problems. A simple elastodynamic analysis is carried out and the operation of the machine is thoroughly explained.

Trompes or Water Bellows. A Way of Producing Wind Through the Fall of Water

Compressed air is nowadays widely used in various industrial applications. In ancient times, it was used both for feeding fires and for wind instruments. Bellows were the usual means, such as piston bellows and leather bellows. In the European Middle Ages and the Renaissance, the progress of metallurgy required the use of large and expensive leather bellows. Some centuries ago, an ingenious and cheaper way of producing compressed air also came into use, namely water bellows or trompes. In Italy, France, Spain and other countries, these were employed for blowing forges, blast furnaces, pipe organs and recreational wind instruments. A trompe works through the action of a column of water falling through a vertical tube. The water enters the pipe mixed with air, which is carried along with the stream through the tube. In an appropriate recipient, the water runs on a hard stone to free the air it carries. From the receiver, the air is conveyed to the utilizing device in a continuous blast. This technology became obsolete with the advent of steam engines. However, for a number of centuries, water bellows represented an important means for producing compressed air and a useful aid for industrial development.

Nona giornata di studio Ettore Funaioli, 17 luglio 2015

In questo volume e raccolta la maggior parte delle memorie presentate in occasione della “Nona Giornata di Studio Ettore Funaioli”, che si e svolta il 17 luglio 2015 presso la Scuola di Ingegneria e Architettura dell’Alma Mater Studiorum – Universita di Bologna. La Giornata e stata organizzata dagli ex allievi del Prof. Ettore Funaioli con la collaborazione del DIN – Dipartimento di Ingegneria Industriale e della Scuola di Ingegneria e Architettura dell’Alma Mater Studiorum – Universita di Bologna, e con il patrocinio dell’Accademia delle Scienze dell’Istituto di Bologna e del GMA – Gruppo di Meccanica Applicata.

Stress and strain fields produced by a heat source in a plane with an elliptic hole

SommarioVengono determinate le tensioni e le deformazioni che nascono in un corpo cilindrico indefinito, con un foro ellittico, per effetto di una sorgente lineare di calore di intensità costante. Si esamina il caso del foro con parete termicamente non conduttrice e si danno alcuni risultati numerici sia per tale caso, sia per il caso del foro con parete a temperatura uniforme.SummaryA report on the steady-state stress and displacement fields arising in an indefinite, elliptically-holed cilindrical body containing a line heat source. The case of an adiabatically-walled hole is examined and some numerical results are given for this as well as for the case of hole with a constant-temperature surface.