In this paper, the authors describe the development of a mathematical model of a controllable vibration damper intended for eventual application to ground-vehicle suspension systems. The damper under investigation employs electro-rheological (ER) fluid as the working medium which enables a continuously variable damping force to be provided in response to an electrical control signal. There are some difficulties inherent in characterizing the ER damper's behaviour which the present study attempts to overcome.The paper begins by describing a novel form of non-dimensionalization which drastically reduces the number of variables required to characterize the quasi-steady behaviour of the ER fluid. The construction of the ER damper is described and, on the basis of physical reasoning, it is shown how a dynamic model can be derived by taking account of ER fluid inertia and compressibility. A recently developed iterative scheme is introduced in order to solve the resulting non-linear equations of motion. The paper concludes with a case study involving the application of the ER damper to controlling the lateral vibrations of a rail vehicle.

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A method for identification of a semi-elliptical crack on the back surface of metal plate by means of direct-current electrical potential difference method (DC-PDM) of multiple-point measurement type was proposed by the authors previously. Geometry of the crack was given by the two-dimensional location of the crack center, the surface and inward angles of the crack, and the length and depth of the crack. In this paper, experiments on the crack identification were carried out using six metal plates with different geometries of semi-elliptical cracks made on the back surface by electric discharge machining. Geometrical parameters of the crack were evaluated by the proposed method. The result of identification was successful and it was clarified that the semi-elliptical crack on the back surface can be identified nondestructively by dc-PDM of multiple-point measurement type.

A method of three-dimensional identification of a semi-elliptical crack existing on the back surface of a conductive plate by direct-current electrical potential difference method with a multiple-probe sensor was proposed. The geometrical condition of the crack was specified by six parameters, the surface and inward angles of the crack plane, θsur and θin, the length and depth of the crack, c and a, and the two-dimensional location of the crack center, (yc, zc), on the back surface, respectively. Identification was carried out based on the distribution of electrical potential difference on the surface of the plate measured with a sensor composed of grid-arranged multiple probes called the “multiple-probe sensor.” As an approximate cracked body and a quick analysis method were used, a number of repeated electrical potential field analyses necessary for the identification of the crack became possible within a practical time. The validity of the method was numerically confirmed by carrying out the identification based on the result by the finite element analysis.

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