The measurement data obtained by experiment contains some measurement errors so that the stress analysis cannot be conducted using raw experimental data. Therefore, the stress analysis method based on the intelligent hybrid method was discussed using experimental data obtained by speckle photography and infrared thermography. The speckle photography was conducted on the compact normal and shear (CNS) specimens made of homogeneous and dissimilar materials subjected to mixed-mode loading. The experiment by infrared thermography was carried out using three kinds of materials and four kinds of the thickness of the specimen. The new method of stress separation was proposed in order to evaluate individual stress components from the sum of the principal stresses obtained from an infrared stress image. This method is based on the inverse problem analysis which uses the least squares method. The intelligent hybrid method can evaluate the stress field from experimental data with high accuracy.
In this paper, intelligent hybrid methods that automatically detect and eliminate errors and noises in full-fields experimental measurement fields are summarized. Each intelligent hybrid method is constructed by the corresponding variational principle minimizing the experimental measurement errors. In this paper, for elastic-plastic problems, the incremental variational principle is explained. The intelligent hybrid method makes it possible to estimate stresses, fracture mechanics parameters and other higher order parameters. The intelligent hybrid methods demonstrate the applicability for elastic-plastic crack, interfacial crack and three-dimensional crack problems.
The slip line field method is applied in CAD system. This system can estimate the optimal blank shapes for deep-drawn containers of arbitrary convex shapes by using some CAD functions. This system is the Windows application, and the operativity is improved by the GUI. In this system, the special knowledges for plasticity are not required to the operators. And the operators easily obtain the optical blank shapes for their deep-drawn problems. Some optimal blank shapes are measured by using this system.
Electronic Speckle Pattern Interferometry (ESPI) is an optical method to obtain displacement and strain distribution of structures. In this study, fatigue tests for notched specimens were carried out, and displacement and strain distributions of the specimens were measured by ESPI method using a specially prepared fixture that follows movement of the specimens. From the displacement distribution, fatigue crack tip was apparently determined. From the strain distribution of notched specimens, strain concentration around notch root was successfully observed, and strain distribution in front of notch agreed with the results of Finite Element Method (FEM). The fatigue experiments were performed under rotating bending and tension-compression loadings for notched specimens with a wide range of stress concentration factors and the fatigue limits were determined. The effects of notch geometry on the fatigue limits were discussed in conjunction with the strain distributions measured by ESPI method.
In an earthquake occurring directly underneath city such as Hanshin-Awaji great earthquake the first axial longitudinal impact induced from the source may give fatal damage to the columns of architectures. This phenomenon is able to be confirmed by a theoretical analysis based on elastic wave propagation in columns fixed at both ends. In this paper the stress intensification behavior in the columns under axial impact is verified by high-speed photoelastic experiments in combination with semi-conductor gage and by the theoretical analysis based upon the longitudinal stress wave analysis method.
In the present paper, firstly, systematization of change of unique performance due to combination of materials (fiber volume fraction and Young's modulus of matrix) is analytically tried for shape memory alloy composite (SMAC). Secondary, for some SMACs having a combination of materials, composite strain (deformation ability) under thermo-loading is experimentally measured using digital image correlation method. Also, internal stress in matrix is qualitatively observed using photoelastic method. Temperature distribution on surface of composite is measured by infrared radiation thermometry method. The results obtained in the present investigation are as follows; (1) The unique performances (deformation ability and creating of compressive residual stress in matrix) of SMAC changed with changing combination of fiber volume fraction and Young's modulus of matrix. Systematizing this trend is useful for designing SMAC desired. (2) By heating composite containing pre-strained NiTi fiber in a polyester, SMACs exhibited large shrinkage and change of internal stress due to shape memory effect of fiber. Also, there existed temperature distribution on the surface of composite. The result of deformation ability was different with analytical result. Therefore, more phenomena must be considered for analytical model such as temperature distribution, change of Young's modulus due to temperature and so on.
A viscoelastic split Hopkinson bar (SHB) technique is successfully applied to study dynamic behavior of a two-piece golf ball. Strain histories of the incident, reflected and transmitted waves on the input and output bars, resulting from SHB tests on cylindrical specimens of cover and core materials of the two-piece golf ball, are resolved into frequency components by Fourier transformation. Then, in frequency domain waveforms at measurement points are corrected to those at the interfaces between a specimen and bars. The complex compliance of each material is determined by calculating strain-stress ratio in the frequency domain, and 3-element viscoelastic models are subsequently identified based on variations of the complex compliances. Using the determined viscoelastic models for the two-piece golf ball, the shape optimization of a club head is investigated by simulating the collision problem of the viscoelastic golf ball with the elastic golf club head. The basis vector method, which is an approximate method for the optimization problems, is employed to find the optimal thickness distribution of the club face so that release velocity of the ball is maximized under the constraint of a constant weight of the club head. An approach to create the basis vectors using eigenmodes of vibration is also presented. An optimal thickness distribution is obtained which raises release velocity of the ball about 5%, and it is found that this approach is effective to optimal design of club heads.