• Structural Engineering and Mechanics
• /
• 제26권1호
• /
• pp.15-30
• /
• 2007

In the paper, one focuses on the problem of duality in non-linear programming, applied to the solution of no-tension problems by means of Limit Analysis (LA) theorems for Not Resisting Tension (NRT) models. In details, one demonstrates that, starting from the application of the duality theory to the non-linear program defined by the static theorem approach for a discrete NRT model, this procedure results in the definition of a dual problem that has a significant physical meaning: the formulation of the kinematic theorem.

• Journal of Mechanical Science and Technology
• /
• 제20권2호
• /
• pp.205-211
• /
• 2006

Among other critical conditions in rotor systems the large non-linear vibration excited by bearing non-linearity causes the rotor failure. For reducing this catastrophic failure and predictive detection of this phenomenon the analysis of orthotropic bearing non-linearity in rotor system using higher order frequency response functions (HFRFs) is conducted and is shown to be theoretically feasible as that of non-rotating structures. The complex HFRFs based on the Volterra series are newly developed for the process and investigated their features by using the simple forms of the FRFs associated with the forward and the backward modes.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.87-90
• /
• 2004

In this paper, geometrically non-linear finite element analyses were performed to study the mechanical behavior of the material system of the envelope of stratospheric airships. The microstructure of the load­bearing plain weave layer was identified and modeled. The Updated Lagrangian formulation was employed to consider the geometric non-linearity as well as the induced structural non-linearity for the fiber tows. The stress-strain behavior was predicted and the effective elastic modulus was calculated by numerical experiments. It was found the non-linear stress-strain curves were largely different from those by linear analysis with much higher non-linear elastic moduli. The difference was more distinguishable when the tow waviness was smaller.

• Geomechanics and Engineering
• /
• 제32권4호
• /
• pp.397-409
• /
• 2023

This study examines two traditional approaches (non-linear elastic and elasto-plastic) in association with 2D and 3D FEM analyses of a box-section pile embedded in sand. A particular emphasis is placed on stress singularities concerning both reentrant corners of the pile section and the resulting tension zones. From the experience gained in this study, non-linear elastic soil models are less restrictive when one considers stress singularities and their possible effects on convergence of the solution. At least for monotonic loading, when compared with field tests, non-linear elastic models yield better results than the plasticity ones. On the other hand, although elasto-plastic models are not limited to monotonic loading, they are much more sensitive to stress singularities. For this reason, a spherical elastic region is necessary at the pile tip to ensure convergence. Without this region, one must artificially impose an apparent cohesion to limit the tension stresses within a sand medium.

• 한국운동역학회지
• /
• 제24권4호
• /
• pp.359-365
• /
• 2014

A study was conducted to investigate the possible effects of fatigue which was resulted from increased running time on the stability during a prolonged run. The purposes of this study were twofold: first, to determine the discrete and non-linear variability of GRF (ground reaction force) components between running times to know the body stability, and second, to determine the pattern between discrete and non-linear variability. Nineteens healthy young adult males served in this study as subjects who ran at their preferred running speed. GRF data for twenty strides were collected at 5, 65, and 125 minutes during run. Variance coefficient and Lyapunov Exponent techniques on the GRF data were used to calculate variability index for each of the running time conditions. There were no difference between discrete variabilities of three components of GRF, but non-linear variability of the Fz component of GRF was decreased by increasing running time (p<.01). No relationship was found between discrete and non-linear variability.

• 신재생에너지
• /
• 제7권3호
• /
• pp.74-82
• /
• 2011

Because concern on the problem of the limited energy is growing and the wind energy is considered as one of the biggest solutions, the researches on the wind energy and turbine are accomplished vigorously. The simulation tools on the non-linear characteristics of wind turbine system are various and it could describe the non-linear characteristics well but, the tool and methodology to apply non-linear control theory rarely exist. In this paper, the application procedure of sliding mode control theory to 2-DOF non-linear wind turbine system is suggested and the application results of it are also shown as compared with a torque loop control theory.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.289-294
• /
• 2001

Three kinds of viscoelastic damper model, which has a non-linear spring as an element is studied analytically and numerically. The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by a non-linear constitutive equation and an additional equation of motion. Harmonic balance method is applied to get analytic solutions of the system. The frequency-response curves show that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurrences of such non-linear phenomena.

• 한국소음진동공학회논문집
• /
• 제12권1호
• /
• pp.57-64
• /
• 2002

Three kinds of viscoelastic damper model, which has a non-linear spring as an element is studied analytically and numerically The behavior of the damper model shows non-linear hysteresis curves which is qualitatively similar to those of real viscoelastic materials. The motion is governed by a non-linear constitutive equation and an additional equation of motion. Harmonic balance method is applied to get analytical solutions of the system. The frequency-response curves sallow that multiple solutions co-exist and that the jump phenomena can occur. In addition, it is shown that separate solution branch exists and that it can merge with the primary response curve. Saddle-node bifurcation sets explain the occurrences of such non-linear Phenomena.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1996년도 추계학술대회논문집; 한국과학기술회관, 8 Nov. 1996
• /
• pp.282-287
• /
• 1996

The non-linear torsional vibrations of the propulsion shafting system with viscous damper are considered. The motion is modeled by non-linear differential equations of second order. the equivalent system is modeled by two mass softening system with Duffing's oscillator. The steady state response of a equivalent system is analyzed for primary resonance only. Harmonic balance method as a non-linear vibration analysis technique is used. Jump phenomena are explained. The primary unstable region obtained by the Mathieu equation is investigated. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisons with both data, it was confirmed that Duffing's oscillator can be used as a analysis method in the modeling of the propulsion shafting system attached viscous damper with non-linear stiffness.

• Journal of the Korean Data and Information Science Society
• /
• 제15권4호
• /
• pp.899-910
• /
• 2004

In this paper we have proposed a new loss function, namely, non-linear exponential(NLINEX) loss function, which is quite asymmetric in nature. We obtained the Bayes estimator under exponential(LINEX) and squared error(SE) loss functions. Moreover, a numerical comparison among the Bayes estimators of power function distribution under SE, LINEX, and NLINEX loss function have been made.