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The purpose of this numerical research is to study a derrick crane under repeated loads. The numerical analyses were carried out considering two different geometrical crane configurations, and two different rope lengths. After a preliminary analysis in order to evaluate both static and dynamic (modal) crane performance, many different analyses were carried out applying different load sequences. These actions were characterized by several impulse loads, which can be applied during the crane active use. Two parameters characterize the impulse load, i.e. the impulse duration and the delay between two successive actions. This load condition, which is not present in the crane design standards, was experimentally checked during the machine use in the marble quarry where it was installed. The results show that in specific crane configurations, characterized by the main arm position and the rope length and with a specific load sequences, both the vibration and the displacement magnitude increase in time, inducing high stress value in the crane components that can collapse the crane itself.

The aim of this research is to study the dynamic behaviour of a real gantry crane subjected to the actions induced by the trolley and payload movement. A specific numerical procedure was developed and implemented in the finite element method in order to simulate different trolley movement modes on the crane's main beam. From the results, it is clear that the crane displacement, especially the longitudinal one, is strongly dependent on the acceleration both in the starting phase and in the stopping phase to which the trolley is subjected during its movement on the crane main beam. The last part of this research simulates the sudden stop of the trolley movement and subsequent payload swinging; in this case, the length of the rope that suspend the payload to the trolley has a fundamental role in the trend and maximum longitudinal crane displacement value.

Strain gauge is a basic tool used to measure the stress of the material. In industry, it has been in use for more than seventy years. The area of application of the strain gauges is very wide. They are used to measure the stress of mechanical and building constructions, individual machine parts, devices and aids in medicine, etc. Straing gauges are made of different materials, in different shapes and dimensions. In spite of the wide presence, the aplication of the straing gauges can be difficult in certain weather conditions. Low temperature and high humidity significantly negativly affect the materials used for placing the gagues on the surface of the part to be tested. In order to overcome these problems, deformeters are used. This study examines the possibility of using a specially designed deformeters in the form of a letter omega (Ω). Tests were carried out in laboratory conditions, on a freebeam, under the action of dynamic loads. The main objective of the test was to determine the degree of correlation between the results obtained by direct reading from the strain gauge and the results read by the deformeter. The analysis of the results of comparative tests showed a high degree of correlation, which confirmed the possibility of using 'Omega' deformeter on the structures that are exposed to dynamic load.

Piezoelectric materials are widely utilized in electronic device applications such as sensors. This paper investigates the dynamic response of a central crack in a finite piezoelectric layered composite plate under impact load. This novel project studies the crack effect on the finite geometries of a piezoelectric layered composite plate. A finite element method for transient dynamic crack analysis in two-dimensional, homogeneous, anisotropic and linear elastic composites was used for this investigation. Initially, the simulation method was verified and calibrated using a simple case study of a piezoelectric material (BaTiO3) with a pre-crack. The results were in good agreement with previous studies in this field. Later, the verified model was used to simulate the piezoelectric layered composite plate. The results showed that the maximum dynamic stress intensity factor depends on the thickness and material properties of the piezoelectric layer and these are crucial parameters in the design and evaluation of a piezoelectric.

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