Search

Ships and other ocean structures have components, which are thin planar or curvilinear viscoelastic solid layers surrounded by air or water. The present work deals with the identification of material parameters of these layers to extend the scope of the real-time structural health monitoring. The work proposes the approach to the parameter identification from passive sensing of acoustic signals resulting from the operational load. The identification is based on the partial integro-differential equation (PIDE) for the non-equilibrium part of the average normal stress. The PIDE is derived in the work. It includes the Boltzmann superposition integral associated with the stress-relaxation function. It is shown that, in the exponential approximation for this function, the PIDE expresses the steady-state solution (with respect to a certain variable) of the corresponding third-order partial differential equation (PDE) of the Zener type. The operat- ors of both the equations are identical. The equations are applicable at all values of the stress-re- laxation time. The roots of the characteristic equation of this operator are consistently analyzed, and the acoustic attenuation coefficient for arbitrary high frequencies is indicated. The approach is exemplified with the identification of the layer-material stress-relaxation time and ratio of the bulk-wave speed to the layer thickness. This identification can be carried out from the acoustic acceleration normal to the layer measured by an acoustic accelerometer attached to the layer surface and is applicable to both planar and curvilinear layers. The identification method presumes the finite-difference calculation of the time derivatives of the measured acoustic acceleration up to the third order and can be computationally efficient.

The transmission system is one of the main parts that determines the behavior, power and fuel economy of a vehicle. Transmission performance is usually related to gear e ciency, gear noise and gear shift comfort during gear change. Synchronizer mechanisms allow gear changing in a smooth way, noiseless and without vibrations, both for the durability of the transmission and the comfort for the users. As a consequence, it is aimed an improvement of the dynamic shift quality, by reducing shifting time and e ort, especially in heavy truck applications. This Master's Thesis project deals with a study of the synchronization processes in manual transmission gearboxes with focus on commercial vehicles. A description of the di erent types of synchronizers is given, followed by its components and how they interact with each other in order to complete the gear changing process namely the synchronization process. Then, quality factors are indenti ed and their e ect on the performance and thus synchronizer e ciency. In this project a model of the manual transmission synchronizer is developed. It is divided into eight di erent phases corresponding to di erent events in the process. Only the rst three phases have been implemented in Matlab and simulated with di erent values of some design parameters in order to analyze the reponse. The results show a good qualitative agreement with the literature., Outgoing

Nowadays, prosthetic manufacturers have developed new designs of below-knee prosthesis which are anthropomorphic and safe. But more research should be done. This project tries to find out optimized parameters of below-knee prosthesis to walk with as low energy as possible. A biomechanical optimal problem is formulated to find out suitable stiffness and damping properties of below-knee prosthesis. These properties mean the relation between the torque on the ankle joint of the prosthetic leg with ankle angle and its velocity. The criterion used has been minimizing energy of both on the healthy part of the body as well as external energy with which the prosthesis battery is supplied. In order to state the optimal problem, firstly an anthropomorphic human gait has been looked for by using computer simulations. It has been chosen a mechanical human model that consist of two legs (with thigh and shank), the trunk and with joints: at ankle, knee and hip. Foot has been modeled as footprint. The system has 7 degrees of freedom. The motion has been parameterized by using polynomial and Fourier series and their parameters have been chosen so that the motion was anthropomorphic. Control torques at joints and ground reaction forces have been determined by using Lagrange equations. After that, the optimization problem has been considered using energy of the healthy part of the body as cost function, while energy consumed by the prosthesis has been calculated in each variance. Algorithm of solution of optimization problem has been implemented in MATLAB so that optimized kinematic parameters of the gait as well as stiffness and damping parameters of the below-knee prosthesis are determined automatically. fmincon function is used to solve the optimal problem and ode45 function to solve the differential equation to find out kinematics of the trunk. The analyses of the obtained optimized values of stiffness and damping parameters of a below-knee prosthesis as well as kinematics of the, Outgoing