Evaluation Of Dynamic Stresses Research Articles

A global-local approach for dynamic stress evaluation of lazy wave flexible risers subjected to random wave and vessel motion

ABSTRACT With the increasingly severe marine environment, the safety reliability of unbonded flexible risers under service conditions is closely related to its dynamic stress response. In this paper, a systematic approach for riser dynamic stress evaluation subjected to random wave and vessel motion is developed to explore the influencing factors. This methodology proposes a global model to acquire the riser global dynamic response under random wave and vessel motion, considering the effects of nonlinear bend stiffener (BS) constraint and nonlinear bending behaviour of flexible pipes. Then, an axisymmetric load model and bending load model are employed to convert the forces and curvatures obtained from the global model into the dynamic stresses of the tensile armour layers. The findings show that BS and riser top angle can affect the dynamic curvature for the riser top-end region, however, has little influence on the effective tension and bending curvature for the other regions.

Innovative numerical fatigue methodology for piping systems: qualifying Acoustic Induced Vibration in the Oil&Gas industry

Acoustic Induced Vibration (AIV) refers to the high acoustic energy generated by pressure-reducing devices that excite pipe shell vibration modes, producing excessive dynamic stress. Analysis of this risk is an important part of Asset Integrity Management systems as AIV can cause catastrophic piping failure. Existing guidelines address this risk through an analytical assessment. However, these methodologies are not fully known and input parameters are limited. Some limits to the guidelines are pointed out with recommendations to improve them.The approach presented for identifying AIV damage is based on a dynamic stress evaluation at pipe discontinuities (welded connections and supports). This evaluation is performed through a fluid-structure coupling Finite Element Analysis. Pressure fluctuations inside the pipe are predicted and coupled with a pipe structural analysis. This methodology is provided with its validation through measurement on an actual AIV field case, corresponding to a crack initiation due to AIV on an FPSO flare network tail pipe.To conclude the paper, the method is then applied to quantitatively assess the mitigation actions’ efficiency on an actual case. Different solutions have been individually tested to end up with a final solution that reduces the damage to acceptable levels in the most cost-effective manner.

Efficient Approach to the Evaluation of Dynamic Stresses in Layered Circular Plates Based on the Prudnikov Formula for the Inverse Laplace Transformation

We propose an algorithm for the solution of axisymmetric dynamic problem of the theory of elasticity for a piecewise homogeneous ring, loaded by normal forces variable as functions of time. We perform the numerical analysis of stresses in plates with arbitrary numbers of layers on the basis of finding the Laplace transform by the modified Prudnikov formula for its inversion. We also establish the characteristic features of the distribution of dynamic stresses in homogeneous and piecewise homogeneous plates.

A Technique for Evaluation of Dynamic Stresses from field Measurements for Vibrating Piping

A Technique for Evaluation of Dynamic Stresses from field Measurements for Vibrating Piping

Photoelastic Analysis of Dynamic Stresses in Anisotropic Plates

The formulas for the correct evaluation of dynamic stresses in structurally anisotropic plates are deduced by using the polarization-optical method and the basic relations of photoelasticity. We study the wave field of stresses formed in an anisotropic plate loaded on its free boundary by pulses from a point source and the influence of anisotropy on the character of the analyzed field. The distribution of dynamic stresses induced by a concentrated source is investigated and the dependences of the maximum stresses in quasilongitudinal -waves and Rayleigh waves on the distance from the source are established.

SYMBOLIC-NUMERIC ANALYSIS OF FLEXIBLE MULTIBODY SYSTEMS14760001*

ABSTRACT The paper presents the vibration analysis and the evaluation of dynamic stresses in flexible multibody systems, and their parameter optimization using symbolic-numeric methods. Based on the fundamentals of multibody system modeling the force method and the deformation method are described and the latter one is extended to include the static and dynamic responses of the structure. Performance criteria are defined for optimization. The overall design process is supported by appropriate software for all steps of analysis and optimization. The application of the approach is devoted to railcar dynamics. For the analysis of the dynamic stresses in a railcar wheelset the extended deformation approach is used. The simulation results indicate that the durability of the design of the wheelset under consideration is satisfactory. The vertical vibrations of the passenger coach with rigid wheelsets and a flexible bogie frame results in acceleration amplitudes of the carbody which may cause a brumming or droning noise. The substitution of the rigid wheelsets by radialelastic ones reduces these amplitudes considerably. An optimization of spring and damper coefficients of the model with radialelastic wheels results in reduced droning noise of such a passenger coach and lower force level between wheel and rail. The symbolic approach is especially highlighted for the simulation at different vehicle speeds and the optimization of the suspension parameters. *Communicated by J. McPhee

Dynamic Stresses in Structurally Anisotropic Bodies

We obtain practical expressions for the correct evaluation of dynamic stresses by using the polarization-optical method in structurally anisotropic media. It is shown that the influence of anisotropy on the character of wave fields of stresses in the subsurface zone manifests itself as a 1.28-fold increase (as compared with the isotropic case) in the stresses σ k formed on the contour in the case where a plane P-wave falls on the free boundary of the plate which coincides with the principal axis of orthotropy Emax. If the P-wave falls on the free boundary in the direction of orthotropy Emin, then the values of the contour stresses σ k in the anisotropic plate are close to the corresponding values obtained for the isotropic plate.

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Frequency Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a harmonically loaded pipeline structure is used to establish the validity of the technique in the frequency domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Time Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a randomly loaded pipeline structure is used to establish the validity of the technique in the time domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.