Advances in Experimental Mechanics IV

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Authors: R.M. Cripps
Abstract: The RNLI has been using composites for the construction of some of its lifeboats since the early 1970s and in the late 1980s a decision was taken to adopt a newer advanced form of composite construction with a view to saving overall structural weight whilst maintaining the requisite structural strength. This paper presents a broad discussion of the history of the use of composites in the RNLI, the structural design and development of lifeboats and the challenges currently faced in the identification of damage and repair methods for fibre-reinforced plastic sandwich structures, operating in the marine environment.
Authors: M. Grédiac
Abstract: The wealth of information provided by full-field measurement techniques is very useful in experimental mechanics. Among different possible applications, full-field measurements can be used to identify parameters governing constitutive equations from heterogeneous strain fields. This keynote lecture first describes the different possible uses of such measurements. It then focuses on the virtual fields method which has been proposed to extract constitutive parameters from full-field measurements. Finally, the method is compared with the finite element model updating technique which is usually used for solving such a problem.
Authors: Roderick A. Smith
Abstract: This paper emphasises the importance of the knowledge of service loads to both the initial design process and the maintenance of structural integrity during the lifetime of engineering components and structures. Three case studies are presented. All involve accidents which caused major loss of life: the Hillsborough Stadium disaster in Britain, the German ICE train crash at Eschede and the China Airlines disaster off Taiwan.
Authors: N. Matsumoto, S. Ohtaki, M. Ohira, H. Kasayama
Abstract: An application of the elastic-plastic problem by the photoelastic coating method is presented in this paper. A general procedure of this experiment, such as image processing and separation of the difference of principal strain to obtaine stresses from isochromatic fringes is referred. The methodology to extract centre lines of coloured isochromatic fringes is explained. Experiments are conducted with cross-shaped aluminum specimens with a circular hole subjected to uniaxial tension and equi-biaxial tension. Results of image processing are shown, and the distribution of difference of principal strains and separated principal strain are shown in the case of equi-biaxial tension.
Authors: Yannick Pannier, René Rotinat, Stephane Avril, Fabrice Pierron
Authors: Kenji Machida
Abstract: In previous studies, the elastic stress field near the crack tip was investigated by digital image correlation and the 2-D intelligent hybrid method. In this study, the 2-D nonlinear hybrid method was developed to analyze the elastic-plastic singular stress field near the crack tip from the displacement data obtained by digital image correlation. Then, the 2-D nonlinear hybrid method was carried out to evaluate stress, strain and J integral. The 3-D elastic-plastic finite element method was conducted on the same specimen as the experiment, and the validity of this approach was discussed from the comparison of the experiment and 3-D finite element method.
Authors: James Eaton-Evans, Janice M. Dulieu-Barton, Edward G. Little, Ian A. Brown
Abstract: Self-expanding stents are small medical devices used to treat vascular disease and are typically fabricated from a super-elastic, shape memory alloy known as Nitinol and have a fine mesh structure. This paper describes preliminary work on the application of Thermoelastic Stress Analysis (TSA) to Nitinol stents. Uniaxial tensile tests were conducted on thin tubes of Nitinol to characterise the material mechanical properties. TSA calibration exercises were conducted, which showed that Nitinol exhibits a non-uniform thermoelastic response through its elastic region that corresponded to the superelastic behaviour. Initial TSA demonstrated that a viable thermoelastic signal could be obtained from the stents. In high resolution tests the effect of motion and noise were considerable but it was still possible to obtain a readable thermoelastic signal.
Authors: Atsumi Ohtsuki
Abstract: This paper describes a development of a new method (: Cantilever Method) to measure Young’s modulus of flexible materials. The method is based on a nonlinear deformation theory that takes into account large deformation behaviors. A set of testing devices was designed and machined. Measurements were carried out on two kinds of flexible materials (PVC: a high-polymer material and SWPA: a steel material). The modulus measured by this method is “Secant modulus”. The results of my evaluation confirm that the new method is suitable for flexible thin plates or rods. Based on the assessments made the method can be further applied to thin sheet and fiber materials (e.g., steel belt, glass fiber, carbon fiber, optical fiber, etc.).
Authors: William N. Sharpe
Abstract: This paper presents three kinds of high-temperature test methods for three different materials along with the results. Resistively heated polysilicon film 3.5 micron thick shows ductile behavior at 500°C. Resistively heated nickel 200 microns thick shows decreasing strength at 400°C. Furnace heated silicon carbide 200 microns thick maintains its strength at 1000°C. Strain is measured by laser-based interferometry in the first two cases to obtain complete stress-strain curves, while force-displacement is measured in the third case.
Authors: S. Kakunai, H. Hayashihara, T. Sakamoto, H. Matsuda
Abstract: Electroless plating can uniformly plate a material on irregular and non-conducting surfaces. Consequently, it has been utilized widely for printed circuit boards in the electronics industry. During the plating process, internal stress is frequently incorporated into the film and this often results in detachment from the substrate. In order to investigate the origins of stress in the films, measurements of film stress are required during the early stages of growth. In this study, TV holography, which can capture holographic images at TV frame rates, was used to sensitively measure the deflection of the cantilever beam during deposition. By substituting the deformation data in Stoney’s equation, it is possible to calculate internal stresses in-situ. The internal stress created by electroless plating from a Cu plating solution on a Be-Cu substrate is discussed. It is assumed that the internal stress is generated in the initial stage in which the plating grains with a thickness of about 0.01µm deposit. This paper shows that the present method can be very useful for in-situ measurement of initial internal stress.

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