• Steel and Composite Structures
• /
• 제39권1호
• /
• pp.1-20
• /
• 2021

An exact solution based on refined third-order theory (TOT) has been presented for functionally graded porous curved beams having deep curvature. The displacement field of the refined TOT is derived by imposing the shear free conditions at the outer and inner surfaces of curved beams. The properties of the two phase composite are tailored according the power law rule and the effective properties are computed using Mori-Tanaka homogenization scheme. The equations of motion as well as consistent boundary conditions are derived using the Hamilton's principle. The curved beam stiffness coefficients (A, B, D) are obtained numerically using six-point Gauss integration scheme without compromising the accuracy due to deepness (1 + z/R) terms. The porosity has been modeled assuming symmetric (even) as well as asymmetric (uneven) distributions across the cross section of curved beam. The programming has been performed in MATLAB and is validated with the results available in the literature as well as 2D finite element model developed in ABAQUS. The effect of inclusion of 1 + z/R terms is studied for deflection, stresses and natural frequencies for FG curved beams of different radii of curvature. Results presented in this work will be useful for comparison of future studies.

• 한국해양공학회지
• /
• 제36권2호
• /
• pp.115-124
• /
• 2022

There are many different types of tanks on ships that meet various requirements. Each tank is required to undergo hydrostatic testing according to the Ship Safety Act after being installed onboard. In some hydrostatic tests, excessive deformation may occur. The overpressure of the air in the tank generated during testing is one of the possible causes of deformation. Based on the dimensions of the tank, nozzle, and pipes installed, it was confirmed that the overpressure of the air can cause problems with the structure, according to the Bernoulli equation. Additionally, finite element analysis (FEA) was performed on the tank structure to confirm the deformation and the stress occurring in the structure. From the perspective of deformation, the maximum deflection limit was set based on the criteria provided by the Eurocode and DNV. From the perspective of stress, the structural safety assessment was performed by comparing the allowable stress and equivalent stress generated in the structure. To determine whether the behavior of the actual structure was well implemented via FEA, beam theory was applied to the tank structure and compared with the FEA results. As a result of the analysis, severe deformation was found in some cases. This means that the overpressure of the air may be the cause of actual deformation. It was also confirmed that permanent deformation may occur.

• 소성∙가공
• /
• 제31권5호
• /
• pp.261-266
• /
• 2022

To reduce the weight of the vehicle, the application of the high strength steel sheets to chassis parts is increased. High forming load is induced during the shearing process of steel chassis parts made of high strength steel, and the possibility of an eccentric load is increased depending on the product seating condition on the die, which decreases the stability and lifespan of the die. In this paper, a three-dimensional finite element analysis with the continuum element was conducted using the damage theory for the cam-trimming process of the front lower arm. The structural analysis of the trimming die was performed with the forming load result obtained from the analysis, and the amount of deflection and the stress distribution of the die during the shearing process were evaluated for the confirmation of the tool stability. The shape of the weak region of the die was modified according to structural analysis and then the stability was confirmed with the finite element analysis. The analysis result showed that the possibility of tool failure during cam-trimming process was remarkably reduced, and the reliability of the proposed modified design was validated.

• Steel and Composite Structures
• /
• 제45권2호
• /
• pp.219-230
• /
• 2022

The aim of this paper is to study the mechanical behaviors of the cold-formed thin-walled steel and reinforced concrete sandwich composite slab (CTS&RC-SCS) under vertical loads and to develop the calculation methods of its flexural bearing capacity and section stiffness. Two CTS&RC-SCS specimens were designed and manufactured to carry out the static loading test, and meanwhile, the numerical simulation analyses based on finite element method were implemented. The comparison between experimental results and numerical analysis results shows that the CTS&RC-SCS has good flexural capacity and ductility, and the accuracy and rationality of the numerical simulation analysis are verified. Further, the variable parameter analysis results indicate that neither increasing the concrete strength grade nor increasing the thickness of C-sections can significantly improve the flexural capacity of CTS&RC-SCS. With the increase of the ratio of longitudinal bars and the thickness of the composite slab, the flexural capacity of CTS&RC-SCS will be significantly increased. On the basis of experimental research and numerical analysis above, the calculation formula of the flexural capacity of CTS&RC-SCS was deduced according to the plastic section design theory, and section stiffness calculation formula was proposed according to the theory of transformed section. In terms of the ultimate flexural capacity and mid-span deflection, the calculated values based on the formulas and the experimental values are in good agreement.

• 한국정밀공학회지
• /
• 제12권7호
• /
• pp.82-91
• /
• 1995

Many kind of springs are used in the suspension of automotive vehicles and among these the leaf spring and the air spring are included. These two springs have not been generally used together in one suspension, but recently the automotive models which use these two springs together increase. This reason is due to the merit of the combination of two type springs. The merits are two. One is the character of air spring, that is, the natural frequen- cy of system is constant in spite of variable weight. The other is the character of leaf spring, that is, the suspension mechanism is simple. The combination spring is used in medium size and special purpose bus. In this paper, we formulate the condition which the leaf spring must satisfy to be optimal design in the combination spring. And experiment is performed to prove the theory. The results are that the combination spring is better than leaf spring in the ride, and that the purposed theory is good for the combination spring design.

• Steel and Composite Structures
• /
• 제50권1호
• /
• pp.63-75
• /
• 2024

In this paper, the modified couple stress theory (MCST) and first order shear deformation theory (FSDT) are employed to investigate the free vibration and bending analyses of a three-layered micro-shell sandwiched by piezoelectric layers subjected to an applied voltage and reinforced graphene nanoplatelets (GPLs) under external and internal pressure. The micro-shell is resting on an elastic foundation modeled as Pasternak model. The mixture's rule and Halpin-Tsai model are utilized to compute the effective mechanical properties. By applying Hamilton's principle, the motion equations and associated boundary conditions are derived. Static/ dynamic results are obtained using Navier's method. The results are validated with the previously published works. The numerical results are presented to study and discuss the influences of various parameters on the natural frequencies and deflection of the micro-shell, such as applied voltage, thickness of the piezoelectric layer to radius, length to radius ratio, volume fraction and various distribution pattern of the GPLs, thickness-to-length scale parameter, and foundation coefficients for the both external and internal pressure. The main novelty of this work is simultaneous effect of graphene nanoplatelets as reinforcement and piezoelectric layers on the bending and vibration characteristics of the sandwich micro shell.

• Advances in concrete construction
• /
• 제16권4호
• /
• pp.189-203
• /
• 2023

This study investigates the bending and stability properties of cylindrical constructions, with a focus on their use in the design and implementation of sporting equipment. The work focuses on a cylindrical construction resembling nanomotors, similar to components seen in sports equipment, using mathematical modeling based on high-order beam theory and nonlocal strain gradient theory. The analysis provides important insights into the dynamic behavior of these systems, revealing light on the impact of numerous factors such as rotational velocity, section change rate, and structural dimensions. The results show a relationship between angular velocity growth and section change rate, which leads to an increase in fundamental frequency values. Furthermore, the research emphasizes the effect of structural factors on dynamic deflection, giving critical information for increasing the stability and performance of sporting equipment. This study adds to the area of sports engineering by providing a more nuanced understanding of how cylindrical constructions react under diverse settings. The results will help to guide the design and manufacturing processes of sports equipment, assuring improved stability and performance for players across a wide range of sports.

• Journal of Mechanical Science and Technology
• /
• 제17권3호
• /
• pp.321-328
• /
• 2003

The elongation of contact length on the line of action is considered with particular reference for roll forming of gears, and for dynamic behavior of the tooth in meshing. However there is no paper that discuss the elongation of contact length in the load meshing of gears. Based on our investigation, the contact length on the line of action elongates more than the kinematically calculated value. In rolling, as the tool approaches the workpiece, the center distance of the gears decreases by a small amount. But, the elongation of contact length is sensitive. Therefore, the contact point on the line of action is difficult to be determined, which complicates the tooth analysis. In this study, the exact relation between the elongation of contact length and the tooth space over the recess or before the approach are revealed by experiments and kinematic theory. This analytical result applies not only for rolling, but also for the single flank meshing which is done under constant center distance.

• International Journal of Precision Engineering and Manufacturing
• /
• 제7권1호
• /
• pp.24-29
• /
• 2006

In this paper, the effect of open crack on the dynamic behavior of simply supported Timoshenko beam with a moving mass was studied. The influences of the depth and the position of the crack on the beam were studied on the dynamic behavior of the simply supported beam system by numerical methods. The equation of motion is derived by using Lagrange's equation. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is modeled as a rotational spring. This flexibility matrix defines the relationship between the displacements and forces on the crack section and is derived by applying fundamental fracture mechanics theory. As the depth of the crack increases, the mid-span deflection of the Timoshenko beam with a moving mass is increased.

• 동력기계공학회지
• /
• 제12권2호
• /
• pp.41-47
• /
• 2008

This article deals with the stress analysis of the friction drive, which transmits the power via the rolling resistance on the contract area between the two rotating bodies. On the contact area, friction drives are normally involved with shear stress due to the transmitted force, as well as normal stress. Thus the stress analysis including the shear stress is necessary for the design of the friction drive. Hertzian results can be used to estimate the normal stress distribution and elastic deflection of the contact area, although the shear stress distribution is not well defined. In order to investigate the shear stress distribution and its effects in a friction drive, we have performed the stress analysis of the spherical continuously variable transmission(CVT) using finite element method. The spherical CVT is one of friction drives, which is used in small power applications. The numerical results show that the normal stress distribution is not affected by the transmitted shear force, and the maximal shear stress is increased in small amount along with the shear force.