Francisco Q. Melo

A hybrid formulation in the stress analysis of curved pipes

Describes a hybrid formulation solution based on variational techniques, where unknown functions are combined with a set of Fourier trigonometric expansions. The unknown functions refer to the toroidal shell distortion in the longitudinal direction when the shell is submitted to generalised in‐plane forces in the linear‐elastic stress field. This set of functions is solved from a system of differential equations, having calculated the eigenvalues and corresponding eigenvectors in the complex field from the system equations matrix. For this purpose the MAPLE® mathematical solver was used. This module led to an analytical solution, which is exact for each Fourier term used in the global solution. The final results agree very well with finite element method or other solutions obtained using a total expansion of trigonometric functions in the longitudinal and meridional directions.

Use of interferometric techniques for measuring the displacement field in the plane of a part-through crack existing in a plate

An experimental procedure based on holographic interferometry coupled with computer-aided image processing techniques was used to estimate the stress intensity factor (SIF) of a part-through crack in a plate. The loading consisted of a uniform remote tensile stress, leading to an opening and edge rotation displacement field along the crack plane. The evaluation of the crack opening displacements and edge rotations, carried out after the numerical interpretation of the fringe pattern, made possible an estimation of the SIF along the crack line, following the theoretical basis of the Line-Spring Model developed by Rice and Levy.

The propagation of axisymmetric transverse waves along a thin-walled cylindrical pipe

This work involves the numerical and experimental study of the propagation of axisymmetric waves along a pipe submitted to a sudden and uniformly applied radial force. In an experimental procedure, this kind of loading may result from the detonation of an explosive inside the pipe. Both ends were left open, so that only radial loads could be achieved in the experiment. A value for the axial propagation of the generated transverse wave train was determined and compared with the numerical analysis.

Stress and deformation in tubular metallic parts of auto seats

In order to assess the structural and material behaviour in particular the deformation and failure in lightweight metallic tubular structural parts of auto seats a pseudo-dynamic procedure was devised. The deformation of circular section tubes subjected to centred transversal force is assessed by rugometric and microtopographic optical inspection.

Optical assessment of stress and deformation in tubular parts of autoseats

In this study, an optical noncontact roughness measurement for the assessment of stress and deformation in lightweight metallic tubular structural parts of autoseats is presented. The deformation of circular section tubes subjected to centered transversal force can be assessed by measuring strain or bending of the tubes. Most frequently contact gauges are used in this process. We employ optical noncontact microtopographic inspection using the MICROTOP.06.MFC microtopographer developed at the Microtopography Laboratory of the Department of Physics at the University of Minho. Bending radius can be directly measured. However, for stronger deformations, bending radius measures become unreliable and full topographic inspection must be performed. If the surface of the tubes in the area where maximum deformation is expected to occur (located by finite element simulation models) is textured to a certain level of roughness, changes in the roughness values after deformation are expected to be measurable. A direct correlation between the deformation state/tension, strain and stress, and surface roughness, in particular average roughness, is found.

Numerical and Experimental Analysis of the Dynamic Behavior of Aluminum‐Composition Cork Sandwich Beams

This work is devoted to the analysis of the static and dynamic properties of composition corks used as damping cores in sandwich structures. A mixed displacement‐stress beam finite element is formulated, implemented and used as a valuable numerical tool in an inverse identification methodology, where the core material is characterized from the free vibration response of the sandwich beam. The obtained values for the storage modulus and loss factor are compared to the static Young’s modulus identified from an experimental characterization analysis using compression and tensile tests.