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The study deals with an experimental campaign to analyze the effects on an automatic machine for plastic cap assembly of the increased vibrations occurring when speeding up its operation. The new velocity specifications are required by the machine manufacturer for raising the production capacity. The analysis successfully identified the functional units critically affected by elastodynamic issues related to the speed increment. Hence it permitted to focus the redesign process on the critical groups in order to implement the desired machine upgrade by means of limited modifications to the current machine version. The most relevant experimental results are presented and discussed. The paper also reports data provided by further tests carried out on a machine variant (obtained after the implementation of the first design modifications), which prove the effectiveness of the proposed solutions to improve the machine performance.

Following a small-scale wedge failure at Yukon Zinc's Wolverine Mine in Yukon, Canada, a vibration monitoring program was added to the existing rockbolt pull testing regime. The failure in the 1150 drift occurred after numerous successive blasts in an adjacent tunnel had loosened friction bolts passing through an unmapped fault. Analysis of blasting vibration revealed that support integrity is not compromised unless there is a geological structure to act as a failure plane. The peak particle velocity (PPV) rarely exceeded 250 mm/s with a frequency larger than 50 Hz. As expected, blasting more competent rock resulted in higher PPVs. In such cases, reducing the round length from 3.5 m to 2.0 m was an effective means of limiting potential rock mass and support damage.

Summarization: In this article an overall procedure is proposed, for the numerical investigation of the structural response of ancient monuments made of megalithic stones. The procedure is implemented on the middle temple of the Mnajdra Megalithic structure, listed as UNESCO World Heritage and regarded as one of the oldest structures from early civilization dating back to about the 4th millennium BC. First, the geometry of the structure is obtained from a point cloud using terrestrial laser scanning. To investigate and estimate the material properties of the structural system, parametric eigenvalue analysis is conducted using the finite element method and results are compared with experimental data from ambient vibration sensors applied to the same structure. The structural response of the system is then evaluated, using nonlinear finite element analysis. Variation of unilateral, frictional contact conditions between megaliths in a preceding analysis step may influence the eigenvalue analysis which follows, indicating the importance of the proper consideration of contact conditions, on the response of the structure. An old collapse in a part of the structure is also reproduced by the numerical model. The proposed scheme, which combines numerical analysis and experimental vibration output to derive structural properties of the monument, can be used in similar structural systems, consisting of multi-body megalithic stones. Presented on: Journal of Cultural Heritage

In this paper, an on-line detection, correction and identification system for vibration forces on the rotor of a rotating active magnetic bearing is proposed. The on-line detection system performs current analysis by comparing ideal no fault currents with fault currents. Pattern recognition was performed by using an input feature obtained from the Wigner-Ville distribution and by comparing fault current patterns with historical fault database patterns obtained from a fully suspended 250 kW water cooling active magnetic bearing pump. A fuzzy logic system used the output of the pattern recognition process to perform error correction on the active magnetic bearing system. A fault identification system provides the type of fault, where the fault occurred in the active magnetic bearing system, the current state of the rotor and the parameters of the fault. Experiments were performed on a double radial active magnetic bearing test rack to demonstrate the effectiveness of the proposed system in the detection, correction and identification of vibration forces on the rotor of an active magnetic bearing system. The detection, diagnosis and correction system corrected and minimised vibration forces to a stable working condition

A capacitive-based soft elastomeric strain sensor was recently developed by the authors for structural health monitoring applications. Arranged in a network configuration, the sensor becomes a sensing skin, where local deformations can be monitored over a global area. The sensor transduces a change in geometry into a measurable change in capacitance, which can be converted into strain using a previously developed electromechanical model. Prior studies have demonstrated limitations of this electromechanical model for dynamic excitations beyond 15 Hz, because of a loss in linearity in the sensor's response. In this paper, the dynamic behavior beyond 15 Hz is further studied, and a new version of the electromechanical model is proposed to accommodate dynamic strain measurements up to 40 Hz. This behavior is characterized by subjecting the sensor to a frequency sweep and identifying possible sources of nonlinearities beyond 15 Hz. Results show possible frequency dependence of the materials' Poisson's ratios, which are successfully modeled and integrated into the electromechanical model. This demonstrates that the proposed sensor can be used for monitoring and evaluation of structural responses up to 40 Hz, a range covering the vast majority of the dominating frequency responses of civil infrastructures.