Dynamic strain measurement of propeller shaft vibrations

The paper proposes an approach to the registration of vibrations parameters to increase the reliability and predict the durability of technical systems with a continuously rotating shaft. For systems with stochastic loads, such as a ship’s shaft line, the actual measurement of shaft stresses and deformations is an actual way to prevent failures and non-destructive testing under operating conditions. The adaptation of the dynamic strain measurement method made it possible to develop a software and hardware complex for recording and analysing transverse, torsional and longitudinal vibrations of shafts. The design of a hardware complex consisting of a measuring mobile and stator modules connected by a wireless network that allows dynamic strain measurement is proposed. The connection diagram and the main metrological and technical characteristics of the modules are given. To test the operability of the hardware complex, an experimental installation was built that allows carrying out investigation of the shaft line vibrations in real operation conditions. Experimental data are presented, the analysis of which allows us to predict the durability of the system.

Estimation of the Mechanical Parameters for a Reduced Coupled Flexural–Torsional Beam Model of a Tall Building by a Sub-Structure Approach

The use of equivalent beam models to estimate the dynamical characteristics of complex tall buildings has been investigated by several authors. The main reason is the structural response estimation to stochastic loads, such as wind and earthquake, using a reduced number of degrees of freedom, which reduces the computational costs and therefore gives the designer an effective tool to explore a number of possible structural solutions. In this paper, a novel approach to calibrate the mechanical and dynamical features of a complete 3D Timoshenko beam, i.e., describing bending, shear and torsional behavior, is proposed. This approach is based on explicitly considering the sub-structures of the tall building. In particular, the frames, shear walls and lattice sub-systems are modeled as equivalent beams, constrained by means of rigid diaphragms at different floors. The overall dynamic features of the tall building are obtained by equating the deformation energy of an equivalent sandwich beam with that of the selected sub-structures. Finally, the 3D Timoshenko equivalent beam parameters are calibrated by minimizing a suitable function of modal natural frequencies and static displacements. The closed form modal solution of the equivalent beam model is used to obtain the response to stochastic loads.

Assessing Material Fragility using Nanoscale Incremental Dynamic Analysis

A new methodology to assess material failure subjected to stochastic loads is proposed, titled Nanoscale Incremental Dynamic Analysis (NIDA), which is adopted from performance-based assessment in structural engineering. Using full atomistic molecular dynamics, proof-of-concept simulations produce the material fragility curve of a simple carbon nanotube.

Assessing Material Fragility using Nanoscale Incremental Dynamic Analysis

A new methodology to assess material failure subjected to stochastic loads is proposed, titled Nanoscale Incremental Dynamic Analysis (NIDA), which is adopted from performance-based assessment in structural engineering. Using full atomistic molecular dynamics, proof-of-concept simulations produce the material fragility curve of a simple carbon nanotube.