Modal Velocity-Based Multiaxial Fatigue Damage Evaluation Using Simplified Finite Element Models

2020 ◽  
Vol 87 (11) ◽  
Author(s):  
Kurthan Kersch ◽  
Elmar Woschke
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Cross Section ◽  
Multiaxial Fatigue ◽  
Finite Element Models ◽  
Damage Evaluation ◽  
Geometric Factors ◽  
The Relationship ◽  
General Method

Abstract This work proposes a new method for the fatigue damage evaluation of vibrational loads, based on preceding investigations on the relationship between stresses and modal velocities. As a first step, the influence of the geometry on the particular relationship is studied. Therefore, an analytic expression for Euler Bernoulli beams with a non-constant cross section is derived. Afterward, a general method for obtaining geometric factors from finite element (FE) models is proposed. In order to ensure a fast fatigue damage evaluation, strongly simplified FE-models are used for the determination of both factors and measurement locations. The entire method is demonstrated on three mechanical structures and indicates a better compromise between effort and accuracy than existing methods. For all examples, the usage of velocities and geometric factors obtained from simplified FE models enables a sufficient fatigue damage calculation.

Fatigue damage in bending of reinforced concrete frames using non-destructive tests for dynamic strength of the cylinder

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dragan D. Milašinović ◽  
Aleksandar Landović ◽  
Danica Goleš
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Damage ◽  
Cross Section ◽  
Modal Parameters ◽  
The Finite Element Method ◽  
Concrete Frames ◽  
Content Type ◽  
Non Destructive

PurposeThe purpose of this paper is to contribute to the solution of the fatigue damage problem of reinforced concrete frames in bending.Design/methodology/approachThe problem of fatigue damage is formulated based on the rheological–dynamical analogy, including a scalar damage variable to address the reduction of stiffness in strain softening. The modal analysis is used by the finite element method for the determination of modal parameters and resonance stability of the selected frame cross-section. The objectivity of the presented method is verified by numerical examples, predicting the ductility in bending of the frame whose basic mechanical properties were obtained by non-destructive testing systems.FindingsThe modal analysis in the frame of the finite element method is suitable for the determination of modal parameters and resonance stability of the selected frame cross-section. It is recommended that the modulus of elasticity be determined by non-destructive methods, e.g. from the acoustic response.Originality/valueThe paper presents a novel method of solving the ductility in bending taking into account both the creep coefficient and the aging coefficient. The rheological-dynamical analogy (RDA) method uses the resonant method to find material properties. The characterization of the structural damping via the damping ratio is original and effective.

Determination of collapse moment of different angled pipe bends with initial geometric imperfection subjected to in-plane bending moments

2021 ◽  
pp. 095440622199640
Author(s):  
Manish Kumar ◽  
Pronab Roy ◽  
Kallol Khan
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Circular Cross Section ◽  
Initial Imperfection ◽  
Bend Angle ◽  
Bending Moments ◽  
Element Analysis ◽  
Geometric Imperfection ◽  
Initial Geometric Imperfection

From the recent literature, it is revealed that pipe bend geometry deviates from the circular cross-section due to pipe bending process for any bend angle, and this deviation in the cross-section is defined as the initial geometric imperfection. This paper focuses on the determination of collapse moment of different angled pipe bends incorporated with initial geometric imperfection subjected to in-plane closing and opening bending moments. The three-dimensional finite element analysis is accounted for geometric as well as material nonlinearities. Python scripting is implemented for modeling the pipe bends with initial geometry imperfection. The twice-elastic-slope method is adopted to determine the collapse moments. From the results, it is observed that initial imperfection has significant impact on the collapse moment of pipe bends. It can be concluded that the effect of initial imperfection decreases with the decrease in bend angle from 150∘ to 45∘. Based on the finite element results, a simple collapse moment equation is proposed to predict the collapse moment for more accurate cross-section of the different angled pipe bends.

scholarly journals High-Fidelity Sensitivity Analysis of Modal Properties of Mistuned Bladed Disks Regarding Material Anisotropy

2018 ◽  
Author(s):  
Adam Koscso ◽  
Guido Dhondt ◽  
E. P. Petrov
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Finite Element Models ◽  
Coordinate Systems ◽  
Bladed Disks ◽  
Bladed Disk ◽  
Material Orientation

A new method has been developed for sensitivity calculations of modal characteristics of bladed disks made of anisotropic materials. The method allows the determination of the sensitivity of the natural frequencies and mode shapes of mistuned bladed disks with respect to anisotropy angles that define the crystal orientation of the monocrystalline blades using full-scale finite element models. An enhanced method is proposed to provide high accuracy for the sensitivity analysis of mode shapes. An approach has also been developed for transforming the modal sensitivities to coordinate systems used in industry for description of the blade anisotropy orientations. The capabilities of the developed methods are demonstrated on examples of a single blade and a mistuned realistic bladed disk finite element models. The modal sensitivity of mistuned bladed disks to anisotropic material orientation is thoroughly studied.

Random Loads Fatigue: The Use of Spectral Methods Within Multibody Simulation

2005 ◽  
Author(s):  
Claudio Braccesi ◽  
Filippo Cianetti ◽  
Luca Landi
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Dynamic Simulation ◽  
Fatigue Damage ◽  
Spectral Methods ◽  
Mechanical Systems ◽  
Frequency Domain Method ◽  
Stress And Strain ◽  
Damage Evaluation ◽  
Multibody Dynamic

The evaluation of the fatigue damage performed by using the Power Spectral Density function (PSD) of stress and strain state is proving to be extremely accurate for a family of random processes characterized by the property of being stationary. The present work’s original contribution is the definition of a methodology which extracts stress and strain PSD matrices from components modelled using a modal approach (starting from a finite element modelling and analysis) within mechanical systems modelled using multibody dynamic simulation and subject to a generic random load (i.e. multiple-input, with partially correlated inputs). This capability extends the actual stress evaluation scenario (principally characterised by the use of finite element analysis approach) to the multibody dynamic simulation environment, more powerful and useful to simulate complex mechanical systems (i.e. railway, automotive, aircraft and aerospace systems). As regards the fatigue damage evaluation, a synthesis approach to evaluate an equivalent stress state expressed in terms of the PSD function of Preumont’s “equivalent von Mises stress (EVMS)”, starting from the complete stress state representation expressed in terms of PSD stress matrix and easily usable in the consolidated spectral methods, is proposed. This approach allows and has allowed the use of the above methods such as the Dirlik formula as a damage evaluation method. An additional result is the conception and implementation of a frequency domain method for the component’s most probable state of stress, allowing quickly identification of the most stressed and damageble locations. The described methodologies were developed and embedded into commercial simulation codes and verified by using as a test case a simple reference multibody model with a simple flexible component.

Finite element simulation on the relationship between pressure and displacement for the waist of elastic pantyhose

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Rui Dan ◽  
Zhen Shi
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Research Work ◽  
Lumbar Vertebrae ◽  
Objective Evaluation ◽  
Quadratic Equation ◽  
New Method ◽  
Content Type ◽  
Displacement Distribution ◽  
The Relationship

PurposeObjective appraisal of pressure comfort is the key point of optimal designing of clothing. The purpose of this paper is to study a new method to provide pressure comfort for the waist of elastic pantyhose through the relationship between pressure and displacement using the finite element method (FEM).Design/methodology/approachThis paper presented a simulation model of the waist cross section consisting of three parts, namely skin, soft tissue and lumbar vertebrae, respectively, according to CT scan. The finite element the model of waist cross-section was established using Mimics software. The pressure–displacement quadratic equation can be obtained using ANSYS software and fitting curves. Meanwhile, we divide the waist cross-section into 12 equal regions according to angle, and then the area shrinkage mass of the waist cross-section can be calculated, respectively.FindingsIn this research work, we got the displacement distribution trend of elastic pantyhose at the waist cross section according to the area shrinkage mass of 12 regions, and this displacement could be used as an objective evaluation index for pressure comfort. All these solutions supply a theoretical reference for optimal design of the women's elastic pantyhose.Originality/valueThe paper analyzed the relationship between pressure and displacement for the waist of elastic pantyhose using FEM, and then got the displacement distribution trend of elastic pantyhose at the waist cross section according to the area shrinkage mass of different regions. It can supply a new method to appraise pressure comfort.

Euler Buckling of Idealised Horizontal Pipeline Imperfections

2010 ◽  
Author(s):  
Gary Cumming ◽  
Andrew Rathbone
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Friction Factor ◽  
Finite Element Models ◽  
Bend Radius ◽  
Element Analysis ◽  
Euler Buckling ◽  
Critical Buckling Force ◽  
The Relationship

Imperfections introduced by pipelay can not be known until installation is complete; therefore a common approach is to perform finite element analysis of idealised horizontal imperfections to determine critical buckling forces. Rundsag et al 2008 [1], showed that the critical buckling force for a snake lay geometry is directly proportional to the pipeline bend radius. Rathbone et al 2008 [2] showed that, with decreasing arch lengths, the pipeline critical buckling force is proportional to the change in the offset angle. This paper looks at the relationship between the minimum critical buckling force and the horizontal offset angle of the pipeline, considering an Euler buckling approach. The resulting relationship that estimates the critical buckle load based on pipeline stiffness and weight, offset angle and friction factor is then compared against idealised finite element models.

Modification for Fatigue Curves Based on Component Reliability

2012 ◽  
Vol 590 ◽  
pp. 116-121
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Yi Jin Shangguan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Safety Evaluation ◽  
Evaluation Procedure ◽  
Element Analysis ◽  
Component Reliability ◽  
The Relationship

Based on component reliability and scatter factors of material, a new procedure is proposed to modify fatigue curves. The scatter characteristics of fatigue life and strength are investigated. The relationship between modified S-N curves and scatter factors of material is presented. The safety evaluation procedure for fatigue damage based on finite element analysis is performed.

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