A Simple Estimation Method of the Stress Distribution Normal to Cross Section at Weld Toe in Non-Load Carrying Welded Joints

2006 ◽  
Author(s):  
Koji Gotoh ◽  
Yukinobu Nagata ◽  
Masahiro Toyosada
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Cross Section ◽  
Hot Spot ◽  
Plate Thickness ◽  
Stress Gradient ◽  
Estimation Method ◽  
Element Analysis ◽  
Weld Toe

Many fatigue damages are occurred in the welded built-up structures designed by the hot spot stress methodology, especially near a boxing fillet weld toe. These fatigue cracks usually initiate from the toe and propagate to the plate thickness direction. Although fatigue life is affected by the stress gradient working over crack propagation path, the effect of stress gradient in cross section is not considered in the hot spot stress methodology. Then, many attempts based on fracture mechanics for the improvement of fatigue life estimation are proposed. Whereas stress distributions along the fatigue crack path must be given in order to apply the methods based on fracture mechanics for the precise fatigue life prediction, no stress distribution along the path considering the stress concentration caused by weld toe shape is obtained in practical structural design stages because the shell elements are used in finite element analyses in the design stages. A simple estimation method of the stress distribution normal to cross section at weld toe in non-load carrying welded joints is proposed in this paper. Calculation results of finite element analysis with shell elements and geometrical conditions (radius and flank angle of fillet weld toe and plate thickness) are used as input data for the estimation. The validity of this method is confirmed by comparing estimation results with ones by finite element analysis with solid elements.

scholarly journals Use of 3D Scan of Weld Joint in Finite Element Analysis and Stochastic Analysis of Hot-Spot Stresses in Tubular Joint for Fatigue Life Estimation

2019 ◽  
Author(s):  
Mikkel L. Larsen ◽  
Vikas Arora ◽  
Marie Lützen ◽  
Ronnie R. Pedersen ◽  
Eric Putnam
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Welded Joints ◽  
Hot Spot ◽  
Strain Range ◽  
Fe Model ◽  
Design Codes ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Weld Toe

Abstract Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are compared to corresponding finite element models. As part of investigating the automatically welded K-joint, 3D scans of the weld surfaces have been made. These scans are included in the FE models to determine the accuracy of the FE models. The results are compared to an FE model with a simple weld geometry based on common offshore design codes and a model without any modelled weld. The results show that the FE model with 3D scanned welds is more accurate than the two simple FE models. As the weld toe location of the 3D scanned weld is difficult to locate precisely in the FE model and as misplacement of strain gauges are possible, stochastic finite element modelling is performed to analyse the resulting probabilistic hot-spot stresses. The results show large standard deviations, showing the necessity to evaluate the hot-spot stress method when using 3D scanned welds.

Numerical Investigation on the Fatigue Behavior of the Multi-Planar Tubular DX-Joint under Combined Loads

2014 ◽  
Vol 1006-1007 ◽  
pp. 11-17
Author(s):  
Gui Jie Liu ◽  
Yu Zhang ◽  
Basit Farooq
Keyword(s):  
Finite Element ◽  
Hot Spot ◽  
Fatigue Behavior ◽  
Combined Loading ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Bending Load ◽  
Weld Toe ◽  
Plane Bending ◽  
Stress Concentration Factors

The stress concentration factors (SCFs) is used in the fatigue design for calculating hot-spot stress. However a major issue can be noted that the majority of research results are focused on the SCF distribution of uni-planar tubular joints subjected to the single basic load. By aiming to find the solution of this problem, the distribution of SCFs at the weld toe of a multi-planar tubular DX-joint which is subjected to the two set of the balanced combined loading components at the end of in-plane braces is studied by the finite element method. Thus it is concluded that for the axial plus in-plane bending load case, hot-spot stress location varies between saddle and crown position; while the location is invariably at the saddle position under combined axial plus out-of-plane bending loads. At last the API RP2A equation for predicting hot-spot stress is used for comparison with the finite element analysis results. Meanwhile the distribution of SCFs is also provided, that information indicates the-hot spot location along the weld toe affects the crack initiation.

A simple analytical bending stress model of parabolic leaf spring

2017 ◽  
Vol 232 (10) ◽  
pp. 1838-1850 ◽  
Author(s):  
Akram Atig ◽  
Rabii Ben Sghaier ◽  
Raoudha Seddik ◽  
Raouf Fathallah
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Leaf Spring ◽  
Bending Stress ◽  
Uniform Load ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Parabolic Leaf Spring

The evaluation of stress distribution, produced by vertical loading along a parabolic leaf spring, presents an essential aspect during the design stage. Commonly, designers utilize the finite element analysis to simulate the stress behaviour of a parabolic leaf spring. Nevertheless, the use of such method is a time-consuming process during the deterministic and the reliability-based fatigue design optimisation. In this study, we propose three analytical models describing the bending stress distribution of a simply supported single asymmetric parabolic leaf spring: (i) an initially curved single asymmetric parabolic leaf spring, subjected to a concentrated load; (ii) a straight single asymmetric parabolic leaf spring, subjected to a uniform load and (iii) an initially curved single asymmetric parabolic leaf spring, subjected to a uniform load. Bending stress distribution results of classical, finite element and proposed models are compared for several case studies. It is observed that the third model is the most precise model compared to the finite element analysis of single asymmetric parabolic leaf spring. Therefore, the suggested model can be used to generate fatigue life diagram that predicts the required mean and alternating load values for a desired fatigue life with an acceptable accuracy and a reduced computational time.

Fatigue Life Prediction of Welded Case Shell on Aeroengine under Combined Internal Pressure and Axial Loads

2013 ◽  
Vol 652-654 ◽  
pp. 1505-1508
Author(s):  
Xiao Xue Duan ◽  
Yan Hua Zhang
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Internal Pressure ◽  
Cross Section ◽  
Life Prediction ◽  
Fatigue Life Prediction ◽  
Axial Loads ◽  
Weld Toe ◽  
Case Shell

Stress and fatigue analysis of welded case shell on aeroengine under combined internal pressure and axial loads using elastic-plastic finite element has been performed. The results show that the largest stress concentration appears on the mutational cross section of the fixture seat and fixture fringe structure some distance from the weld toe. The positions with the weakest fatigue life locate at the fixture fringe close to the weld toe of girth joint, and also appear at the ring closed weld of the case shell middle.

Fatigue Strength Evaluation of the Load-Carrying Cruciform Fillet Welded Joints Using Hot-Spot Stress

2006 ◽  
Vol 324-325 ◽  
pp. 1281-1284 ◽  
Author(s):  
Byeong Wook Noh ◽  
Jung I. Song ◽  
Sung In Bae
Keyword(s):  
Fatigue Strength ◽  
Welded Joints ◽  
Hot Spot ◽  
Plate Thickness ◽  
Structural Stress ◽  
Leg Length ◽  
Element Analysis ◽  
Hot Spot Stress ◽  
Load Carrying ◽  
Weld Toe

In this study, fatigue strength of load-carrying cruciform fillet welded joints were evaluated using a new method proposed by Yamada, for geometric or structural stress in welded joint, that is, one-millimeter stress below the surface in the direction corresponding to the expected crack path. Validity of the method is verified by analyzing fatigue test results for load-carrying cruciform welded specimens has different size of weld toe radius, leg length and plate thickness reported in literature. Structural stress concentration factor for 1mm below the surface was calculated by finite element analysis for each specimen respectively. When compared to the basic fatigue resistance curve offered by BS7608, the one-millimeter stress method shows conservative evaluation for load-carrying cruciform fillet welded joints.

Probabilistic Failure Prediction of SCS-6/Ti-15-3 MMC Ring

1998 ◽  
Vol 120 (4) ◽  
pp. 714-720 ◽  
Author(s):  
F. A. Holland ◽  
E. V. Zaretsky ◽  
M. E. Melis
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Finite Element Methods ◽  
Fracture Strength ◽  
Effective Volume ◽  
Ring Fracture ◽  
Element Analysis ◽  
Fatigue Data ◽  
Two Parameter

Two parameter Weibull analysis was used to predict the fracture strength and fatigue life of an SCS-6/Ti-15-3 metal matrix composite (MMC) ring from coupon samples. Two methods were used. One method was to calculate an effective volume for an idealized ring on the basis of a theoretical approximation of the stress distribution. Fracture strength and fatigue life of the coupon samples were then scaled to the effective volume of the ring. The other method used finite-element analysis (FEA) to determine a stress distribution in the actual, geometrically imperfect ring. The total ring reliability was then determined by multiplying the element reliabilities. Experimental fracture strengths were obtained for two MMC rings, each having an O.D. of 176.5 mm (6.95 in.) and I.D. of 146.0 mm (5.75 in.) and a 15.2 mm (0.60 in.) width. The median value of the experimental ring fracture strength data was 173.1 MPa (25.1 ksi). Fracture strength predictions by the effective-volume and finite-element methods were 5 and 17 percent lower than the experimental value, respectively. The effective-volume and finite-element methods predicted ring fatigue lives of 2700 and 4800 cycles, respectively, at a 50 percent probability of failure and 154.4 MPa (22.4 ksi) maximum ring internal pressure. No ring fatigue data were available for comparison.

scholarly journals Comparison of one versus two maxillary molars distalization with iPanda: a finite element analysis

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Kamontip Sujaritwanid ◽  
Boonsiva Suzuki ◽  
Eduardo Yugo Suzuki
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Alveolar Bone ◽  
Vertical Direction ◽  
Minimal Amount ◽  
Element Analysis ◽  
Molar Distalization ◽  
Second Molar ◽  
Maxillary Molars ◽  
Displacement Patterns

Abstract Background The purpose of this study was to compare the stress distribution and displacement patterns of the one versus two maxillary molars distalization with iPanda and to evaluate the biomechanical effect of distalization on the iPanda using the finite element method. Methods The finite element models of a maxillary arch with complete dentition, periodontal ligament, palatal and alveolar bone, and an iPanda connected to a pair of midpalatal miniscrews were created. Two models were created to simulate maxillary molar distalization. In the first model, the iPanda was connected to the second molar to simulate a single molar distalization. In the second model, the iPanda was connected to the first molar to simulate “en-masse” first and second molar distalization. A varying force from 50 to 200 g was applied. The stress distribution and displacement patterns were analyzed. Results For one molar, the stress was concentrated at the furcation and along the distal surface in all roots with a large amount of distalization and distobuccal crown tipping. For two molars, the stress in the first molar was 10 times higher than in the second molar with a great tendency for buccal tipping and a minimal amount of distalization. Moreover, the stress concentration on the distal miniscrew was six times higher than in the mesial miniscrew with an extrusive and intrusive vector, respectively. Conclusions Individual molar distalization provides the most effective stress distribution and displacement patterns with reduced force levels. In contrast, the en-masse distalization of two molars results in increased force levels with undesirable effects in the transverse and vertical direction.

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