• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.79-82
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• 2002

A finite element method based on the two-dimensional progressive failure analysis considering material nonlinearity is presented for characterizing the strength and failure of the unidirectional-fabric hybrid laminated composite joints under pin loading. The 8-node laminated shell element is incorporated in the updated Lagrangian formulation. Failure criteria including the Maximum Stress and Tsai-Wu are used in conjunction with the complete unloading stiffness degradation method. For the verification, joint tests are conducted for the specimens with two different ply-number ratios of UD composite to fabric composite. Although there are some differences depending on ply-number ratios, the finite element model using the maximum stress criterion considering nonlinear material behavior predicts the failure strength best.

• Structural Monitoring and Maintenance
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• v.4 no.3
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• pp.269-299
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• 2017

This paper presents a Level III damage evaluation methodology, which simultaneously, identifies the location, the extent, and the severity of stiffness damage in deep beams. Deep beams are structural elements with relatively high aspect (depth-to-length) ratios whose response are no longer based on the simplified Euler-Bernoulli theory. The proposed methodology is developed on the bases of the force-displacement relations of the Timoshenko beam theory and the concept of invariant stress resultants, which states that the net internal force existing at any cross-section of the beam is not affected by the inflicted damage, provided that the external loadings in the undamaged and damaged beams are identical. Irrespective of the aspect ratios, local changes in both the flexural and the shear stiffnesses of beam-type structures may be detected using the approach presented in this paper.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.53-60
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• 1999

The bending buckling behavior of circular cylindrical shell is studied. The classical analysis by Love type solution and the package program LUSAS for the structural analysis are used to estimate the critical stresses of circular cylindrical shells under axial compression and bending loads. In this paper, the Love type of buckling equation is carefully investigated and numerical results are presented for a wide range of radius-to-thickness (R/t) ratios and length-to-radius (L/R) ratios. These results show that the maximum critical bending stress is about 30~80% greater than the critical compressive stress

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.150-156
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• 1997

Three dimensional finite element analysis was conducted to estimate the effect of shape parameters (plate width and thickness) on the stress intensity factor for crack in the integrally stiffened plate. Analysis was done for width ratios of 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, and thickness ratios of 2, 3, 4, 6. Based on these results, an empirical equation of geometry factor is formulated as a function of crack length and thickness ratio.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.3
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• pp.101-107
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• 2008

A composite mechanics for discontinuous fiber reinforced polymer matrix composites(PMC) is analysed in order to predict fiber axial stresses. In continuum approach. frictional slip which usually takes place between fibers and polymers is accounted to derive PMC equations. The interfacial friction stress is treated by the product of the coefficient of friction and the compressive stress norma1 to the fiber/matrix interface. The residual stress and the Poisson's contraction implemented by the rule of mixture(ROM) are considered for the compressive stress normal to the fiber/matrix interface. In addition. the effects of fiber aspect ratio and fiber volume fraction on fiber axial stresses are evaluated using the derived equations. Results are illustrated numerically using the present equations with reasonable materials data. It is found that the fiber axial stress in the center region shows no great discrepancy for different fiber aspect ratios and fiber volume fractions while some discrepancies are shown in the fiber end region.

• Bulletin of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.19-24
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• 2015

A reliable assessment and analysis of the condition of high pressure and temperature steam pipelines requires defining stress state, which will take into consideration not just the impact of internal pressure and temperature but all applied loads. For that, usage of modeling and numerical methods for calculation and analysis of stress state is essential. The main aim of piping stress analysis is to check the design of piping layout, which will allow simple, efficient and economical piping supports and provide flexibility to the piping system for loads and stresses. The piping stress analysis is carried out using CAESER II software. By using this software we can evaluate stresses, stress ratios, flange condition, support loads, element forces and displacements at each node and points. In this paper, only the maximum and minimum displacement results are tabulated, which is also shown in detail by an example of main steam pipelines of UST Main Engine System [1].

• Structural Engineering and Mechanics
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• v.6 no.5
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• pp.543-554
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• 1998

Space truss structures may be fabricated in any of several common grid configurations. With different configurations, the truss performance varies considerably affecting both its competitiveness and suitability for specific applications. The work presented in this paper is an assessment of the most commonly adopted truss configurations and their effect on truss characteristics such as the stiffness/weight value, member stress distribution, number of joints and members, degree of redundancy and cost. The study is parametric and covers wide variations of truss aspect ratios, boundary conditions and span/depth ratios. The results of this study could be of significant value to the design of space truss structures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.239-240
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• 2008

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.99-104
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• 2002

In this paper the influence or specimen length on flexural compressive strength and parameter or equivalent rectangular stress block of polymer concrete was evaluated. For this purpose, a series of C-shaped specimens subjected to eccentric compression were tested using four different length-to-depth ratios(from 1.0, 2.0, 3.0 and 4.0) of specimens with compressive strength of 1,020kgf/cm$^2$. Results indicate that for the region of h/c$\leq$3.0 the reduction in equivalent rectangular stress block depth and flexural compressive strength with increase of length-to-depth ratios was apparent but for the region of h/c$\geq$3.0 they were nearly constant. It means that for the region of h/c$\geq$3.0 effect of specimen length on equivalent rectangular stress block depth and flexural compressive strength was negligible. It was also founded that the effect of specimen length on v, a coefficient of strength, that was from 0.84 to 0.86 regardless of h/c was petty. Finally, predictive equation is, suggested by using modified law of effect of specimen length and results.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.15
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• pp.6243-6247
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• 2015

Background: Thyroid cancer (TC) is a more common endocrine malignancy in females and is a major cause of death in developing countries. Therefore the aim of this study was to explore possible risk factors of thyroid cancer in females of Pakistan. Materials and Methods: This study covered 232 females, including 127 (54.7%) cases and 105 (45.2%) controls, from the INMOL Hospital and Sheikh Zayed Hospital, Lahore. Different risk factors were explored by the descriptive and inferentially statistics. Odds ratios and 95% confidence intervals for different risk factors were computed using logistic regression. Results: The results showed six risk factors, marital status, family history of thyroid cancer, iodine in the diet, oxidative stress, fast food and fried food, to demonstrate positive significant links to thyroid cancer (odds ratios and 95% confidence intervals of :2.152, 1.104-4.198; 2.630, 1.416-4.887; 2.391, 1.282-4.458; 4.115, 2.185-7.750; 3.656, 1.851-7.223; 2.357, 1.268-4.382; and 2.360, 1.199-4.643, respectively). Conclusions: The Oxidative stress, marital status, family history of cancer, fast food, use of iodine diet and fried food are the risk factors of thyroid cancer in females.