• International Journal of Railway
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• v.5 no.2
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• pp.89-92
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• 2012

Effective notch stress, as an approach to evaluate the local stress at a notch (weld toe or root), is defined as the total stress assuming linear-elastic material behavior. This method can be effectively used to evaluate the fatigue performance of welded joints. In this study, finite element analysis results using the effective notch stress method were correlated with fatigue test results of rib-to-deck welded joints in a steel orthotropic bridge deck. Effective notch stress approach provided a good correlation with the crack pattern observed in the full-scale fatigue test. A higher effective notch stress at the critical weld toe than at the weld root was consistent with the dominant crack pattern observed at the weld toe during testing. The effective notch stress at the toe on the deck plate was about 80% higher than that on the rib; no cracks at the weld toe on the rib in the testing were observed. Maximum effective notch stress at the weld root occurred on the upper side of the root notch, which indicates that cracks are more likely to propagate into the deck plate, not into the weld metal. This is also consistent with the observed crack pattern in which the crack from the root propagated upward into the deck plate. No such crack pattern, propagating into the weld metal, was observed in the testing.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.573-579
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• 2010

The notch effects on the fatigue strength of welded joints are both stress concentration and fatigue strength reduction. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. In this paper, well-known notch stress approaches - critical distance method, area method and fictitious rounding method are presented for the fatigue strength of cruciform joints. The estimated results of the present methods are applied to the experiments performed in this study and reported in the references. The results of the application show that the fatigue-life scatterness of the experimental data expressed in the nominal stress is significantly reduced by introducing the effective fatigue stress of the present study.

• Journal of Ocean Engineering and Technology
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• v.25 no.5
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• pp.47-51
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• 2011

This paper analyzes the fatigue-life of welded joints using the notch stress approach. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. The actual bead shape is complex and 3-dimensional. It may also greatly influence the fatigue strength. In this study, the welded shape was modeled using a 3D-scanner. The critical distance method was adopted in the evaluation of the fatigue effective notch stress for the weldments. Fatigue life tests were performed to verify the present method of fatigue life estimation for two types of welded plates with longitudinal attachments. The estimated results of the present methods were applied to the results of the experiment. The results of the analysis showed that the scatter of fatigue-life for the experimental data expressed in the nominal stress was significantly reduced by applying the effective fatigue stress of the present study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1358-1361
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• 2003

In this study, intrinsic static/dynamic fracture toughness of Al 7175-T74 are evaluated from the apparent static/dynamic toughness of notched specimen. The notch/crack critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The notch/crack critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, critical notch root radius can be predicted by notch/crack critical average stress fracture model.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1-6
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• 2004

In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structure with notch.

• Structural Engineering and Mechanics
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• v.26 no.1
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• pp.87-97
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• 2007

Some mixed mode fracture criterion may be converted in to elliptical or ellipsoidal formula with the aid of mathematical translation. Hence, the crack initiation in mixed mode fracture I+II emanating from notches, has been studied using notched circular ring specimens. On the basis of Irwin (1957) theory, a new criteria in mixed mode fracture I+II, based fracture elliptic criterion and notch stress intensity factors has been developed.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.56-61
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• 2011

In this study, a series of fatigue tests was conducted to evaluate fatigue strength for the root gap difference with high strength steel with butt welded joints. A finite element analysis using effective notch stress method was also performed to compare effective notch factors each other with butt welded specimens made by copper backing. The results of fatigue tests were classified according to the root gap difference. Fatigue life of butt welded specimens is presented for determining the root gap of high strength steel with butt welded joints in terms of fatigue strength. Then effective notch stress was applied to interpret fatigue strength of butt welded specimen model which is reflected actual measured dimensions. As a result, fatigue strength of high strength steel with butt welded specimens is increased by root gap gets longer in length.

• Journal of Welding and Joining
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• v.27 no.1
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• pp.90-94
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• 2009

In this study, a series of fatigue test was performed to evaluate the fatigue strength of butt welded specimens. Effective notch stress through finite element analysis was conducted to analyze the fatigue results. As a results, no significant decrease in fatigue strength was observed when backplates were present. The S-N curve that based on effective notch stress appeared a similar fatigue lift to FAT 225 curve without reference to existence of backplates.

• Structural Engineering and Mechanics
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• v.38 no.5
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• pp.619-631
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• 2011

This paper provides a complex variable BIE for solving the periodic notch problems in plane plasticity. There is no limitation for the configuration of notches. For the periodic notch problem, the remainder estimation technique is suggested. In the technique, the influences on the central notch from many neighboring notches are evaluated exactly. The influences on the central notch from many remote notches are approximated by one term with a multiplying factor. This technique provides an effective way to solve the problems of periodic structures. Several numerical examples are presented, and most of them have not been reported previously.

• Proceedings of the KWS Conference
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• v.43
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• pp.275-277
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• 2004

Fictitious notch radius approach is based on the Neuter's microstructural support hypothesis which assumes that fatigue crack is governed by highly stressed volume of the material right on the weld toe area rather than the surface stress at a pin point of weld toe area. Variety of successes have been achieved in applying this methodology to the fatigue of welded joint, hence, it became one of recommended design procedure in IIW's recommendation as well as many ship classification societies. 1mm fictitious notch radius approach was applied to the various fatigue problems of welded joints in this study covering the effect of weld size, notch stress calculation for 3D geometry and low cycle fatigue problem. It was found that fictitious notch radius approach fumed out to be very effective and accurate in dealing with fatigue strength of welded joint.