MEASURING DISPLACEMENT FIELDS OF CURVED SURFACE BY MOIRE INTERFEROMETRY OF PARTIAL COHERENT LIGHT

This paper presents a method to measure the in-plane displacement fields of curved surface by moire interferometry of partial coherent light.The method has the following advantages:simple optical system,no requirement on vibration isolation,high sensitivity,large measuring range,high contrast of inter ference fringes and availability to in-situ structural testing.The present paper also gives theoretical analysis of the method and the formulas of light intensity and displacement field,and introduces a replication technique to form a high frequency reflectance grating on the curved surface.The experiments achieved the measurement of the surface displacement field of a cylindrical shell—the simultaneous circumferential,axial and 45° displacement fields.The torsional test data for surface displacement of a circular bar agree well with the theoretical result.

Elastic solutions for partially embedded single piles subjected to simultaneous axial and lateral loading

In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogeneous, semi-infinite isotropic medium. A comparison was made between model test results and the obtained solutions to show their validity. The calculation results indicate that the horizontal displacement and bending moment of the pile increase with increases of the axial and lateral loads. The maximum horizontal displacement and bending moment decrease by 37.9% and 13.9%, respectively, when the elastic modulus of soil increases from 4 MPa to 20 MPa. The Poisson ratio of soil plays a marginal role in pile responses. There is a critical pile length under the ground, beyond which the pile behaves as though it was infinitely long. The presented solutions can make allowance for the continuous nature of soil, and if condition permits, they can approach exact ones.

Nosing process of empty and foam-filled circular metal tubes on semispherical die by theoretical and experimental investigations

Nosing process of circular metal tubes in empty and polyurethane foam-filled conditions on a semispherical rigid die was analyzed by theoretical and experimental methods.A new theoretical model of plastic deformation of circular metal tubes was demonstrated during the nosing process on a rigid semispherical die.Based on the analytical model,some theoretical relations were calculated to estimate instantaneous forming load and dissipated energy of empty and foam-filled circular metal tubes versus axial displacement.Some circular brazen and aluminum tubes were prepared and shaped into semispherical nosed nozzles to verify the present theory.Comparison of theoretical predictions and the corresponding experimental measurements reveals that predicted load?displacement and dissipated energy?displacement diagrams by theoretical formulas have a good correlation with the corresponding experimental curves and it proves verity of the theory.Also,the present theory shows that dissipated energy and axial load of empty tubes depend on material type,wall thickness and diameter of the tubes and they are independent of tube initial length.Furthermore,the experimental results show that the presence of polyethylene Teflon-constraints increases ultimate axial displacement of the forming process.