فهرست مطالب

Stress Analysis - Volume:1 Issue: 1, Spring - Summer 2016

Journal of Stress Analysis
Volume:1 Issue: 1, Spring - Summer 2016

  • تاریخ انتشار: 1395/10/20
  • تعداد عناوین: 6
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  • R. Moharrami, M.J. Taghiloo, A. Darudi Page 1
    Digital shearography is a non-destructive and non-contact method for strainmeasurement. In this article strain analysis on defected plate has been studied by the digital shearography method along with a new technique for phase map measurement. For this purpose, an optical set-up known as modified Michelson interferometry system with two diode lasers were developed which are used as coherent optical source. To create phase shifting a piezo-electrical ceramic was used to miniature displacements of interferometry. Phase shifting technique was used to measure phases and differences between the phases.
    The strain was measured using the experimental method and compared with numerical analysis results. Behavior of two graphs of experimental measurement and numerical analysis was approximately the same.
    Keywords: Strain measurement, Phase calculation, Digital shearography, Geometric defect
  • N. Habibi, S. Samawati, O. Ahmadi Page 9
    In this paper, a semi-analytical method for creep investigation and elastic behavior of FGM rotary cylinders has been introduced. Assumed cylinder was divided to numerous finite width layers with constant thermodynamic properties in each layer. Governing equations converted to ordinary differential equations with constant coefficients by applying continuity conditions between layers and boundary conditions of disc in derived equations, then these equations could be solved by a prepared computer code. For thermo-elastic part, variation of dimensionless radial and circumferential strains versus dimensionless radius investigated for several power of FGM material. Also, verification of results was done. For creep part, variation of dimensionless radial and circumferential strain rates versus dimensionless radius was studied for different temperatures and limited timeframe. Changes of radial and circumferential strain rates versus radius were investigated and the results were validated. Finally, the effects of various parameters on creep behavior of rotary cylinder in several examples was examined.
    Keywords: Exact Solution, Rotary Cylinder, creep, Navier Equation
  • M. Shaban Page 23
    Metal sandwich panels are three-dimensional structures widely used in industries mainly due to two distinct properties: low density and high strength. Although significant efforts have been made at research into corrugated sandwich panels, analytical solutions are still very few. This work wishes to present accurate analytical results of static analysis of corrugated sandwich panels. In order to determine equivalent properties of corrugated core in the thickness direction, energy method is used in conjunction with homogenization approach. Based on three-dimensional theory of elasticity, partial differential equations are reduced to ordinary differential equations by using the Fourier series. Analytical solutions for the stress and displacement fields are derived by using the state-space method in the thickness direction.
    A detailed parametric study was conducted involving the dependency of out-of-plane properties on the corrugation geometrical parameters. Moreover, effects of these variables on the stress and displacement fields are discussed.
    Keywords: Corrugated sandwich panel, Elasticity solution, State-space, Analytical, Static
  • S. Pirmohammad, A. Bayat Page 33
    In this paper, a new disc-shaped specimen containing a tilted crack was proposed so as to conduct fracture tests under mixed mode I/III loading. This specimen was able to produce complete mode mixities, ranging from pure mode I to pure mode III. Many finite element analyses were performed to obtain crack parameters (i.e. stress intensity factors at the crack tip) and geometry factors. It was shown that the mode III was added to the mode I loading as the crack angle changed. Moreover, the crack length as well as position of the lower supports was varied to study loading type at the crack tip. Finally, applicability of the proposed specimen in experimental point of view was considered by performing fracture experiments on the asphalt concrete. The results showed that fracture strength of the asphalt concrete decreases as the proportion of mode III at the crack tip enhances.
    Keywords: Mixed mode I, III, Cracked disc specimen, Fracture strength, Asphalt concrete
  • K. Narooei, M. Arman Page 43
    In this paper, the nonlinear elastic behavior of pericardium of human, canine, calf and ostrich was studied. For this purpose, the mechanical behavior was investigated from two viewpoints of the Cauchy and Green elastic materials.
    Firstly, the experimental data were fitted by Cauchy elastic stress equation. The results showed that the response of Cauchy elastic materials was not fitted with the experimental data appropriately. Secondly, the Green elastic materials were studied by assuming strain energy functions for the mechanical response of the samples. For this purpose, the exponential-exponential, power law-power law, and exponential-power law energy functions were investigated by mathematical programming. It was observed that all energy functions were fitted with the experimental data accurately, especially the power law-power law function. Finally, it was observed that the Green elastic materials theory was more appropriate for studying the mechanical behavior of pericardium by comparing the experimental and theoretical results.
    Keywords: Pericardium, Nonlinear elastic behavior, Strain energy function, Green material, Cauchy material
  • J. Nemati, S. Sulaiman, A. Khalkhali Page 55
    In this study, annealed CP-Ti (Grade 2) was processed by Equal Channel Angular Extrusion (ECAE) up to 2 passes at a temperature of 400◦C following route A with a constant ram speed of 30 mm/min through a die angle of 90◦ between the die channels. Mechanical properties of the extruded materials were obtained at different strain rates. The results indicated that the tensile yield stress and ultimate tensile strength of the extruded specimens increased significantly after 2 passes of ECAE process. The maximum increase for yield stress was around 90% which occurred at the pulling rate of 0.5 mm/min. The bending fatigue life of the extruded specimens improved significantly so that in low cycle fatigue regime a 700% increase in fatigue life was observed after two ECAE passes. The improvement was lower in high cycle fatigue regime. The microhardness measurement of the specimens indicated that the average microhardness of the samples increased about 140% after 2 passes. The fracture mechanism of the ECAE specimens was also studied by fractography of the fracture surface of specimens. Microstructure of the extruded specimens was also examined by optical microscopy.
    Keywords: CP-Ti (Grade2), ECAE, Mechanical properties, Bending fatigue, Microhardness