Fatigue Assessment of Threaded Segment Specimens Based on the Weakest Link Theory

2013 ◽  
Author(s):  
Arne Fjeldstad ◽  
Anders Wormsen ◽  
Finn Kirkemo
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
High Stress ◽  
Local Stress ◽  
Von Mises Stress ◽  
Good Correspondence ◽  
High Stress Concentration ◽  
Weakest Link ◽  
Stress Concentration Factors ◽  
Von Mises

In this paper, the weakest link approach has been used to estimate the fatigue life of threaded segment specimens based on fatigue test data of smooth specimens of the same material. The segment specimens are cut outs from an ACME threaded component with a thread geometry typically used in subsea connectors. Fatigue life estimates of the threaded specimens were also made by means of the local stress approach which is often the prescribed method in standards and recommended practices, such as DNV-RP-C203. This method uses the von Mises stress range at the most severe location of the specimen when estimating the fatigue life. The estimated S–N curve based on the weakest link approach shows good correspondence with fatigue test results of the threaded segment specimens. The estimated S–N curve based on the local stress approach is well below the S–N curve for the threaded segment specimen. A factor between two and three on stress is observed. Hence, the inherent level of conservatism related to the local stress approach when assessing the fatigue strength of components with very high stress concentration factors is considered to be high.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

2020 ◽  
Vol 1 (1) ◽  
pp. 93-102
Author(s):  
Carsten Strzalka ◽  
◽  
Manfred Zehn ◽  
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
A Priori ◽  
High Stress ◽  
Von Mises Stress ◽  
Detailed Knowledge ◽  
Variable Loading ◽  
Numerical Effort ◽  
Von Mises

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

The Influence of Switch Temperature on Coke Drum Fatigue Life

2010 ◽  
Author(s):  
Fa´bio de Castro Marangone ◽  
Ediberto Bastos Tinoco ◽  
Carlos Eduardo Simo˜es Gomes
Keyword(s):  
Fatigue Life ◽  
Structural Model ◽  
High Stress ◽  
Axial Direction ◽  
Pressure Vessels ◽  
High Stress Concentration ◽  
Short Period ◽  
Bending Stresses ◽  
Switch Temperature ◽  
Lower Temperature

Coke drums are thin-walled pressure vessels that experience severe thermal cycling condition which consists of heating, filling and rapidly cooling the drum in a short period of time. After some years under operation, cracks at the vessel may occur, especially at high stress concentration areas such as the skirt support to shell attachment. During the filling phase of the cycle, when the empty and cooled coke drum is filled with hot oil, the shell and cone temperatures increase rapidly compared to the skirt temperature and the last is pushed outward, since its bottom is at lower temperature and fixed at a concrete base. During quenching (sudden cooling) phase, the coke drum is filled with water at about 80°C and tends to cool faster than the skirt, which is pulled inward until equilibrium is obtained. The skirt expansion and contraction movement results in bending stresses in axial direction on the top of skirt. As lower the switch temperature is, more severe is the bending effect. One of PETROBRAS delayed coke unit presented some operational problems at pre-heating phase, resulting in lower switch temperatures. This paper presents an analysis showing the influence of the switch temperature on coke drum fatigue life. At first, the transient loading conditions were established from thermocouple measurements at skirt attachment weld (hot box region). Later, a transient thermal analysis was performed with FEA and the temperature gradient at the skirt attachment during entire thermal cycle was obtained. The thermal results were then converted to a structural model which was solved for linear elastic stress including other loads such as pressure. Finally, the maximum stress components for both filling and quenching phases were determined and a complete stress range was calculated as per ASME Section VIII, Div 2. The procedure described above was applied for different switch temperatures scenarios in order to show its influence on the fatigue life of the coke drum.

scholarly journals Design and Fatigue Optimization of Drive Shaft

2021 ◽  
Vol 9 (VIII) ◽  
pp. 194-203
Author(s):  
Ashish Bawkar
Keyword(s):  
Fatigue Life ◽  
Natural Frequency ◽  
Drive Shaft ◽  
Von Mises Stress ◽  
Hollow Shaft ◽  
Design And Optimization ◽  
The Road ◽  
Increasing Demand ◽  
Von Mises ◽  
Fea Analysis

This work aims towards the design and optimization of the drive shaft as there is increasing demand for weight reduction in an automobile vehicle. The drive shaft is basically a torque transmitting element which transmit the torque from the differential gearbox to the respective wheels. In general, the drive shafts are subjected to fluctuating loads as the torque requirement changes according to the road conditions. Due to this, the drive shaft should be designed considering fatigue failure. The Maruti Suzuki Ertiga model is chosen for design and optimization of the drive shaft. For the fatigue life predicting of the drive shaft, the S-N curve approach is used. Furthermore, the inner diameter of the shaft is varied to obtain the optimized diameter of a hollow shaft which can withstand these fluctuating loads without failure. Along with fatigue life prediction, the natural frequency of the hollow shaft is also calculated. Furthermore, the parametric analysis is carried out of fatigue FOS, Von mises stress, weight and natural frequency of the shaft by varying the diameter ratio of the hollow shaft, and the nature of variation of these parameters are plotted in their respective graphs. The design is validated by performing FEA analysis for each case of a hollow shaft using Ansys software. Finally, from the FEA analysis we conclude that the optimized dimensions of the hollow drive shaft are safe.

Finite Element Simulation of Tensile Behaviors in the Elastic Region for PP/Nano-TiO2 Composites

2010 ◽  
Vol 150-151 ◽  
pp. 1819-1823
Author(s):  
Yu Jiao Wu ◽  
Ming Rui Gao ◽  
Yu Ling Chen ◽  
Juan Li ◽  
Shao Lin Ju
Keyword(s):  
Finite Element ◽  
Stress Field ◽  
Volume Fraction ◽  
Local Stress ◽  
Von Mises Stress ◽  
Analysis Model ◽  
Nano Tio2 ◽  
Two Phase ◽  
Element Analysis ◽  
Von Mises

Polypropylene(PP)/nano-TiO2 composites were prepared by the melt intercalation molding. Based on the assumption of continuum mechanics model for materials, a finite element analysis model for the composites was constructed using ANSYS 11.0 software. In the stage of deformation (pre-yield regime) the response mechanism of the stress and the strain for composites was investigated, and the von mises stress field of PP/nano-TiO2 composites has also been simulated. It was found that the simulation results are Consistent with the testing results at low volume strain level. The results simulated using the 2D model are accurate with the experimental results. If the volume fraction of particles is less, other particles have little influence on the local stress field of a certain particle, no obvious overlap or cross of the stress field could be found between two neighboring particles. While applying different loads, the stress jumps to maximum stress value in the interaction region of the two phase firstly, and then it occurs that the particles debond with the matrix.

Development of Design Curve for Sweepolet Subjected to Acoustic Induced Vibration

2016 ◽  
Author(s):  
Yuqing Liu ◽  
Philip Diwakar ◽  
Dan Lin ◽  
Ismat Eljaouhari ◽  
Ajay Prakash
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Fatigue Failure ◽  
High Stress ◽  
Peak Stress ◽  
Acoustic Energy ◽  
Piping System ◽  
Element Analysis ◽  
Design Curve ◽  
High Stress Concentration

High acoustic energy has the potential to cause severe Acoustic Induced Vibration (AIV) that leads to fatigue failure at high stress concentration regions such as fittings in a piping system. Sweepolet fittings have been extensively used as mitigation to counteract the risk of fatigue failure caused by AIV. The advantages of a sweepolet are its integrally reinforced contoured body and low stress concentration. However, there are inconsistencies in published standards and regarding the design limits for sweepolet subjected to AIV. In this paper, Finite Element Analysis is conducted to simulate high frequency pipe shell wall vibration caused by acoustic energy inside the pipe. Peak stress and the associated minimum fatigue life are calculated for sweepolet and sockolet under the same acoustic excitation. By comparing the stress level to that of a sockolet whose design limit to AIV had been published, the design curve and fatigue life equation for sweepolet are developed.

Optimization of a Bend-Twist-and-Sweep Compliant Mechanism

2014 ◽  
Author(s):  
Joseph Calogero ◽  
Mary Frecker ◽  
Aimy Wissa ◽  
James E. Hubbard
Keyword(s):  
Compliant Mechanism ◽  
Twist Angle ◽  
High Stress ◽  
Peak Stress ◽  
The Other ◽  
Optimal Designs ◽  
Von Mises Stress ◽  
Loading Conditions ◽  
Objective Functions ◽  
Von Mises

The overall goal of this research is to develop design optimization methodologies for compliant mechanisms that will provide passive shape change. Our previous work has focused on designing two separate contact-aided compliant elements (CCE): one for bend-and-sweep deflections, called the bend-and-sweep compliant element (BSCE), and another for twist deflection, called the twist compliant element (TCE). In the current paper, all three degrees of freedom, namely bending, twist, and sweep, are achieved simultaneously using a single passive contact-aided compliant mechanism. A new objective function for a contact-aided compliant mechanism is introduced and the results of the optimization procedure are presented. A bend-twist-and-sweep compliant element (BTSCE) can be inserted into the leading edge spar of an ornithopter, which is an avian-scale flapping wing un-manned air vehicle. The multiple objective functions of the optimization problem presented in this paper are: for upstroke, maximize tip bending and sweep deflections, maximize twist angle, and minimize the mass and peak von Mises stress in the BTSCE, and for downstroke, minimize tip bending and sweep deflections, minimize twist angle, and minimize the mass and peak von Mises stress in the BTSCE. This allows a designer to select a CCE from a set of optimal designs to accomplish all three displacement goals. The BTSCE was modeled using a commercial finite element program and optimized using NSGA-II, a genetic algorithm. The results for a single angled compliant joint (ACJ) for quasi-static upstroke loading conditions are presented. Two optimal designs are discussed and compared, one with a moderate peak stress and moderate deflections, the other with a high peak stress and large deflections. The optimization results are then compared to the previous results for the two independent CCEs. A design study showed that the angle of the ACJ needs to be obtuse to achieve a positive twist angle during upstroke, and an acute contact angle reduces peak stress. The deflection objective functions were relatively insensitive to eccentricity for upstroke and downstroke compared to the other parameters, and a high stress penalty was paid for any gains in deflection. The downstroke objective functions were relatively insensitive to all parameters compared to the upstroke objective functions, and were much smaller in magnitude. The optimization showed that under simplified upstroke loading conditions, the BTSCE with a single ACJ allowed bending deflection near 30% of the length of the BTSCE, twist angle near 0.14 radians, and sweep deflection near 5% of the length of the BTSCE.

Fatigue Life Analysis of the Stabilizer Anti-Roll Bar Using ANSYS

2011 ◽  
Vol 383-390 ◽  
pp. 5894-5898 ◽  
Author(s):  
Su Hong Liu ◽  
Fang Li
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Fatigue Life ◽  
Parametric Model ◽  
Von Mises Stress ◽  
Endurance Test ◽  
Finite Element Technology ◽  
Life Analysis ◽  
Fatigue Life Analysis ◽  
Von Mises

The stabilizer anti-roll bar can prevent the vehicle from rollover, so it is important to get the mechanical properties of it. To achieve it, the finite element technology is chosen and the parametric model was built in the first place. The von Mises stress distribution, reliability and the sensitivity were obtained after being analyzed respectively. Based on these, the fatigue life was estimated finally. The fatigue analysis results were contrasted with the life requirements of stabilizer bar’s endurance test.

Fatigue Test and Stress Analysis of Threaded Connection of Arch Bridge Stainless Steel Suspender

2010 ◽  
Vol 452-453 ◽  
pp. 541-544 ◽  
Author(s):  
Yu Pu Song ◽  
Han Yong Liu
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Stress Analysis ◽  
Fatigue Test ◽  
Von Mises Stress ◽  
External Loading ◽  
Arch Bridge ◽  
Finite Element Software ◽  
Threaded Connection ◽  
Von Mises

This work presents a study of a fatigue test and a finite element analysis on an arch bridge stainless steel suspender with threaded connections. A suspender which had a diameter of 70mm was tested under axial tensile loads range from 430kN to 700kN. The suspender was sudden failure from the thread root of the first loaded tooth in the pin after 1546609 cycles. Then, a two-dimensional axisymmetric modeling ignoring the helix angle of the thread was established with finite element software ANSYS to perform a stress analysis of the threaded connection. The stress concentration factors (SCFs) at the root of the teeth of pin were investigated under the applied external loading. The conclusive results had been drawn from the analysis including the location and the value of maximum SCF in the pin. Finally, the location and the value of the maximum von Mises stress were given. The results showed that the location of the fracture surface was consistent with the location of the maximum von Mises stress.

scholarly journals STUDI NUMERIK UMUR KELELAHAN (FATIGUE LIFE) PADA PROPELLER KAPAL PENANGKAP IKAN DENGAN KAPASITAS MESIN 24 HP

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Rizqi Ilmal Yaqin ◽  
Angger Bagus Prasetiyo ◽  
Pritiansyah Pritiansyah ◽  
Muhammad Haritsah Amrullah ◽  
Binsar Maruli Tua Pakpahan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Rapid Development ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Fishing Boat ◽  
Finite Element Analysis Simulation ◽  
Von Mises ◽  
Model Affect

Propeller is part of a key component in fishing boat propulsion. Propeller can provide momentum to the fluid which can be a thrust on the ship. However, The failure of the propeller found prematurely. The failure of the propeller maybe because of overload on the propeller model so the fatigue life of the propeller becomes low. On the other hand, the rapid development of technology can simulate a design model to look for failures that occur. Finite Element Analysis is one of the designer solutions to determine the age of failure of a model and failure-prone areas in a model. This study uses propeller model data from fishing boat with engine 24HP in Dumai City TPI that always fail prematurely. The material used is copper alloy. While the drawing model uses Autodesk Inventor and Finite Element Analysis simulation using ANSYS R17.2 software with the number of model nodes is 51108 and the number of elements of the model is 26268. The results obtained from this study are Von Mises stress on the simulation model that is equal to 613.33 MPa to 0.01164 MPa. While the deformation value due to the effect of loading on the model is 5,3657 mm to 0 mm. These results affect the age of fatigue (fatigue life) on the model with the highest value 109 and the lowest 0. The results of the fatigue life value on the model affect the results of the level of damage and the safety number of the model with successive values of 1032 to 1 and 15 to 0.32446. The conclusion of the result is the propeller will fail prematurely.

scholarly journals Influence of the Realistic Artery Geometry Parameters on a Coronary Stent Fatigue Life

2019 ◽  
Vol 16 (03) ◽  
pp. 1842006 ◽  
Author(s):  
Xinyang Cui ◽  
Qingshuai Ren ◽  
Gaoyang Li ◽  
Zihao Li ◽  
Aike Qiao
Keyword(s):  
Fatigue Life ◽  
Fatigue Resistance ◽  
Safety Factor ◽  
Geometric Model ◽  
Von Mises Stress ◽  
Stress Distributions ◽  
Goodman Diagram ◽  
Von Mises ◽  
Geometry Parameter ◽  
Artery Geometry

The stents’ adaptability and safety in realistic and idealized stenotic coronary model were compared to investigate the influence of artery geometry parameter on stent fatigue life. The stents’ fatigue resistance ability was calculated using Goodman diagram, and the cycle to failure, the fatigue life, and the fatigue safety factor (FSF) were analyzed. Although the peak top of the von Mises stress was located at the bending area of crowns, the stress distributions were different in the two models. Considering the safety and accuracy, it is necessary to use a realistic geometric model to calculate the stent fatigue performance.

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