• Structural Engineering and Mechanics
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• 제86권1호
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• pp.119-137
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• 2023

The purpose of this research is to assess the performance of CBN and ceramic tools during the dry turning of gray cast iron EN GJL-350. During the turning operation, the variable machining parameters are cutting speed, feed rate, depth of cut and type of the cutting material. This contribution consists of two sections, the first one deals with the performance evaluation of four materials in terms of evolution of flank wear, surface roughness (2D and 3D) and cutting forces. The focus of the second section is on statistical analysis, followed by modeling and optimization. The experiments are conducted according to the Taguchi design L₃₂ and based on ANOVA approach to quantify the impact of input factors on the output parameters, namely, the surface roughness (Ra), the cutting force (Fz), the cutting power (Pc), specific cutting energy (Ecs). The RSM method was used to create prediction models of several technical factors (Ra, Fz, Pc, Ecs and MRR). Subsequently, the desirability function approach was used to achieve a multi-objective optimization that encompasses the output parameters simultaneously. The aim is to obtain optimal cutting regimes, following several cases of optimization often encountered in industry. The results found show that the CBN tool is the most efficient cutting material compared to the three ceramics. The optimal combination for the first case where the importance is the same for the different outputs is Vc=660 m/min, f=0.116 mm/rev, ap=0.232 mm and the material CBN. The optimization results have been verified by carrying out confirmation tests.

• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.165-174
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• 2002

In the present study, interfacial cracks between an isotropic and orthotropic material, subjected to static far field tensile loading are analyzed using the technique of photoelasticity. The fracture parameters are extracted from the full-field isochromatic data and the same are compared with that obtained using boundary collocation method. Dynamic photoelasticity combined with high-speed digital photography is employed for capturing the isochromatics in the case of propagating interfacial cracks. The normalized stress intensity factors for static cracks are greate. when ${\alpha}$: 90$^{\circ}$(fibers perpendicular to the interface) than when ${\alpha}$=0$^{\circ}$(fibers parallel to the interface), and those when ${\alpha}$=90$^{\circ}$are similar to ones of isotropic material. The dynamic stress intensity factors for interfacial propagating cracks are greater when ${\alpha}$=0$^{\circ}$ than ${\alpha}$=90$^{\circ}$. For the velocity ranges (0.1 < C/C$\sub$s1/<0.7) observed in this study, the complex dynamic stress intensity factor │K$\sub$D/│increases with crack speed c, however, the rate of increase of │K$\sub$D/│with crack speed is not as drastic as that reported for homogeneous materials.

• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.33-37
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• 2009

Fiber Bragg grating (FBG) sensors already have been the focus for structural health monitoring (SHM) due to their distinguishing advantages. However, as bare optical fiber is very fragile, bare FBG strain sensor without encapsulation can not properly be applied in practical infrastructures. Therefore encapsulation techniques for making encapsulated FBG strain sensor show very important in pushing forward the application of FBG strain sensors in SHM. In this paper, a simplified approximate method to analyze the stress transferring rules for embedded FBG strain sensors in concrete monitoring is put forward according to mechanics of composite materials. Shear lag theory is applied to analyze the stress transferring rule of embedded FBG strain sensor in measured host material at the first time. The measured host objects (concrete) and the encapsulated FBG strain sensor are regarded as a composite, and then the stress transfer formula and stress transfer coefficient of encapsulated FBG strain sensor are obtained.

• 한국안전학회지
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• 제11권1호
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• pp.11-15
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• 1996

For the assessment of fracture behaviors of structural components, various fracture mechanics parameters have been applied to date. New approaches to analyze structural fracture performance under elastic-plastic condition have been proposed by the development of testing methods for characterization of material behavior which is defying to the analysis by conventional fracture parameters. In this study, on the assumption that, initiation of crack propagation of a piping materials occurs when the crack tip strain field reaches "the local fracture strain", following two major issues are discussed ; 1) The relationship between the critical value of J-integral($J_{IC}$) and the local fracture strain (${\varepsilon}_c$) in uniaxial tensile test in the region of maximum reduction area was described. 2) To proved the validity of above relations a series of tests were performed under various temperature and on the different piping materials.materials.

• Structural Engineering and Mechanics
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• 제7권6호
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• pp.575-588
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• 1999

A boundary element method is applied to the analysis of crack trajectory in materials with complex microstructure, such as discontinuously reinforced composite materials, and systems subjected to complex loading, such as indentation. The path followed by the crack(s) has non-trivial geometry. A study of the stress intensity factors and fracture toughness of such systems must therefore be accompanied by an analysis of crack trajectory. The simulation is achieved using a dual boundary integral method in planar problems, and a single boundary integral method coupled with substructuring in axisymmetric problems. The direction of crack propagation is determined using the maximum mechanical energy release rate criterion. The method is demonstrated by application to (i) a composite material composed of components having the elastic properties of aluminium (matrix) and silicon carbide (reinforcement), and (ii) analysis of contact damage induced by the action of an indenter on brittle materials. The chief advantage of the method is the ease with which problems having complex geometry or loading (giving rise to complex crack trajectories) can be treated.

• Structural Engineering and Mechanics
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• 제30권4호
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• pp.501-512
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• 2008

The axisymmetric problem of a functionally graded annular plate is considered by extending the theory of functionally graded materials plates suggested by Mian and Spencer (1998). In particular, their expansion formula for displacements is adopted and the hypothesis that the material parameters can vary along the thickness direction in an arbitrary continuous fashion is retained. However, their analysis is extended here in two aspects. First, the material is assumed to be transversely isotropic, rather than isotropic. Second, the plate is no longer tractions-free on the top and bottom surfaces, but subject to uniform loads applied on the surfaces. The elasticity solutions are given for a uniformly loaded annular plate of functionally graded materials for a total of six different boundary conditions. Numerical results are given for a simply supported functionally graded annular plate, and good agreement with those by the classical plate theory is obtained.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.257-269
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• 2019

This paper develops a nonlocal strain gradient plate model for damping vibration analysis of smart magneto-electro-viscoelastic nanoplates resting on visco-Pasternak medium. For more accurate analysis of nanoplate, the proposed theory contains two scale parameters related to the nonlocal and strain gradient effects. Viscoelastic effect which is neglected in all previous papers on magneto-electro-viscoelastic nanoplates is considered based on Kelvin-Voigt model. Governing equations of a nonlocal strain gradient smart nanoplate on viscoelastic substrate are derived via Hamilton's principle. Galerkin's method is implemented to solve the governing equations. Effects of different factors such as viscoelasticity, nonlocal parameter, length scale parameter, applied voltage and magnetic potential on damping vibration characteristics of a nanoplate are studied.

• Advances in materials Research
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• 제5권4호
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• pp.263-277
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• 2016

Mechanical properties of $Al/Al_2O_3$ and $Al/B_4C$ composites prepared through powder metallurgy are estimated up to 50% $Al_2O_3$ and 35% $B_4C$ weight fractions using micromechanics models and experiments. The experimental Young's modulus up to 0.40 weight fraction of ceramic is found to lie closely between Ravichandran's/Hashin-Shtrikman lower/upper bounds, and close to self consistent method/Miller and Lannutti method/modified rule of mixture/fuzzy logic method single value predictions. Measured Poisson's ratio lies between rule of mixture/Ravichandran lower and upper bound/modified Ravichandran upper bounds. Experimental Charpy energy lies between Hopkin-chamis method/equivalent charpy energy/Ravichandran lower limit up to 20%, and close to the reciprocal rule of mixture for higher $Al_2O_3$ content. Rockwell hardness (RB) and Micro-hardness of $Al/Al_2O_3$ are closer to modified rule of mixture predictions.

• 한국해양공학회지
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• 제14권2호
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• pp.76-83
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• 2000

this paper was concentrated on the finite element formulation to solve boundary value problems by using the isotropic elasto-plastic damage constitutive model proposed previously(Noh, 2000) The plastic damage of ductile materials is generally accompanied by large plasticdeformation and strain. So nonlinearity problems induced by large deformation large rotation and large strain behaviors were dealt with using the nonlinear kinematics of elasto-plastic deformations based on the continuum mechanics. The elasto-plastic damage constitutive model was applied to the nonlinear finite element formulation process of Shin et al(1997) and an improved analysis model considering the all nonlinearities of structural behaviors is proposed. Finally to investigate the applicability and validity of the numerical model some numerial examples were considered.

• Earthquakes and Structures
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• 제9권5호
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• pp.999-1028
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• 2015

Despite the fact that the fundamental period appears to be one of the most critical parameters for the seismic design of structures according to the modal superposition method, the so far available in the literature proposals for its estimation are often conflicting with each other making their use uncertain. Furthermore, the majority of these proposals do not take into account the presence of infills walls into the structure despite the fact that infill walls increase the stiffness and mass of structure leading to significant changes in the fundamental period numerical value. Toward this end, this paper presents a detailed and indepth analytical investigation on the parameters that affect the fundamental period of reinforce concrete structure. The calculated values of the fundamental period are compared against those obtained from the seismic code and equations proposed by various researchers in the literature. From the analysis of the results it has been found that the number of storeys, the span length, the stiffness of the infill wall panels, the location of the soft storeys and the soil type are crucial parameters that influence the fundamental period of RC buildings.