Assessment of maximum crack size a

(1) This will usually be determined on the basis of net section ductile tearing under the maximum applied tensile load with the appropriate partial factor (see Part 1 of this Prestandard). For further information on fracture toughness see References B.8.1 and B.8.2. b) mk value for weld toe stress concentration Figure B.4.1. Use of typical standard geometry solutions for y

Crack growth data A and m

(1) A and m are obtained from crack growth measurements on standard notched specimens orientated in the LT, TL or ST direction (e.g. see Figure B.3.1) using standardised test methods (e.g. see Reference B.8.3). The specimen design must be one for which an accurate stress intensity factor (K) solution (i.e. the relationship between applied load and crack size 'af) is available. Recommended thickness w 20 < b< w 4 Recommended thickness w 20 < b< w 4 Fig.B.3.1. Typical crack growth...

References

B.8.1 AW guidance on assessment of the fitness for purpose of welded structures. IIW Draft for Development doc. SST-1157-90. B.8.2 Guidance on some methods for the derivation of acceptance levels for detects in fusion welded joints. British Standard Published Document 6493 1991. B.8.3 Standard test method for measurement of fatigue crac k growth rates, ASTM E647-93. B.8.4 Fatigue crack propagation in aluminium, IIW Document XIII-B77-90. B.8.5 Stress intensity factor equations for cracks in...

Background to the Eurocode Programme

The Commission of the European Communities (CEC) initiated the work of establishing a set of harmonized technical rules for the design of building and civil engineering works which would initially serve as an alternative to the different rules in force in the various Member States and would ultimately replace them. These technical rules became known as the Structural Eurocodes. In 1990, after consulting their respective Member States, the CEC transferred the work of further development, issue...

Basis of design General

(1)P The aim of designing a structure against the limit state of fatigue shall be to ensure, with an acceptable level of probability, that its performance is satisfactory during its entire design life, such that the structure will not fail by fatigue during the design life nor will it be likely to require premature repair of damage caused by fatigue. 2.1.2 Influence of fatigue on design (1)P Structures subjected to frequently fluctuating service loads may be susceptible to failure by fatigue...

Enhancement Cases G Case

(1) This applies to initiation sites in base material and wrought products in structural elements remote from connections. It may also be applied to structures which have been effectively stress relieved. (2) Allowance shall be made for any pre-load or lack of fit in addition to the applied stresses. (3) The values of f(R) are given in table G.2.1. and fig. G.2.1. Table G.2.1. Values of f(R) for Case 1 Table G.2.1. Values of f(R) for Case 1 Figure G.2.1. Strength enhancement factor f(R) at 2...

Global Stress Analysis

(1)P The method of analysis shall be selected so as to provide an accurate prediction of the elastic stress response of the structure to the specified fatigue loading. NOTE An elastic model used for static assessment (ultimate or serviceability limit state) in accordance with Part 1.1 of this Prestandard may not necessarily be adequate for fatigue assessment. (2)P Dynamic effects shall be included in the calculation of the stress history, except where an equivalent loading is being applied...

Guidance on Assessment by fracture mechanics B Scope

(1) The objective of the annex is to provide information on the use of fracture mechanics for assessing the growth of fatigue cracks from sharp planar discontinuities. Main uses are in the assessment of - known flaws (including fatigue cracks found in service). - assumed flaws (including consideration of the original joint or NDT detection limits). - tolerance to flaws (including fitness for purpose assessment of fabrication flaws for particular service requirements). (2) The method covers...

Scope of Eurocode Part

(1) This Part 2 gives the basis for the design of aluminium alloy structures with respect to the limit state of fatigue induced fracture. Design for other limit states is covered in Part 1. (2) This Part 2 gives rules for design by the following methods (3) This Part 2 contains the manufacturing quality requirements necessary to ensure that the design assumptions are met in practice. - Beams and braced and unbraced framed structures - Stiffened plate structures of flat or shell construction (2)...

Fatigue Strength Data Classified details

1 P The generalised form of the Aa-N relationship is shown in figure 1.5.2, plotted on logarithmic scales. The design curve represents a mean minus 2 standard deviation level below the mean line through experimental data. 2 P The basic fatigue design relationship for endurances less than 5 x 106 cycles is defined by the equation Nj is the predicted number of cycles to failure of a stress range Acjj Aac is the reference value of fatigue strength at 2 x 106 cycles, depending on the category of...

Stress range parameters for specific Initiation Sites

4.4.1 Parent material, full penetration butt welds and mechanically fastened joints see Tables 5.1.5, 5.1.2, 5.1.3 and initiation sites 1,2,3,7 and 9 in Table 5.1.3 . 1 P Cracks initiating from weld toes, fastener holes, fraying surfaces, etc. and propagating through parent material or fully penetrated weld metal shall be assessed using the nominal principal stress range in the member at that point see Fig.4.2.1 . 2 P The local stress concentration effects of weld profile, bolt and rivet holes,...

Principles B Flaw dimensions

Planar Flaws Fatigue

1 Fatigue propagation is assumed to start from a pre-existing planar flaw with a sharp crack front orientated normal to the direction of principle tensile stress fluctuation Act at that point. 2 The dimensions of the pre-existing flaws are shown in Figure B.2.1 depending on whether they are surface breaking or fully embedded within the material. Figure B.2.1 Pre-existing planar flaws

Stress Spectra

Cycle Counting

1 Cycle counting is a procedure for breaking down a complex stress history into a convenient spectrum of cycles in terms of stress range A a, number of cycles n and, if necessaiy, R ratio see figure 2.2.1 and 5.3 . There are various methods in use. 2 For short stress histories where simple loading events are repeated a number of times, the Reservoir method is recommended. It is easy to visualise and simple to use see figure 4.5.1 . Where long stress histories have to be used, such as those...

Definitions

Miner Modified Fatigue Curve

1.5.1 Terms common to all Eurocodes 1 P Unless otherwise stated in Part 1 of Eurocode 9 the terminology used in International Standard ISO 8930 applies. 1.5.2 Special terms used in this Part 2 of Eurocode 9 1 P The following terms are used in Part 2 of Eurocode 9 w ith the following meanings - Fatigue Weakening of a structural part, through gradual crack propagation caused by repeated stress fluctuations. - Fatigue loading A set of typical load events described by the positions or movements of...

Hot spot stresses

1 The hot spot stress approach is used mainly for joints in which the weld toe orientation is transverse to the fluctuating stress component, and the crack is assumed to grow from the weld toe. The approach is not suitable for joints in which the crack would grow from embedded defects or from the root of a fillet weld. Compared with the nominal stress approach, this approach is more suitable for use in the following cases a there is no clearly defined nominal stress due to complicated...

Applicability of Nominal Modified Nominal and Hot Spot Stresses Nominal stresses

Elastic Stress

1 P Nominal stresses shall be used directly for the assessment of initiation sites in simple members and joints where the following conditions apply a The details associated with the site are in reasonable agreement with the appropriate detail category requirements in Tables 5.1.1 to 5.1.5. b The detail category has been established by test in accordance with Annex C and where the results have been expressed in terms of the nominal stresses. c Gross geometrical effects such as those listed in...

Full scale testing

1 Full scale testing may be carried out under actual operating conditions, or in a testing facility with the test load components applied by hydraulic or other methods of control. 2 The conditions for manufacturing the structure should be as for component testing in C.3.1. 3 The loads applied should not exceed the nominal loads. 4 Where the service loads vary in a random manner between limits they should be represented by an equivalent series of loads agreed between the supplier and the...

Annex C Informative

C.1.1 Fixed structures subject to mechanical loading 1 This includes structures such as bridges, crane girders and machinery supports. Existing similar structures subject to the same loading sources may be used to obtain the amplitude, phasing and frequency of the applied loads. 2 Strain, deflection or acceleration transducers fixed to selected components which have been calibrated under known applied loads can record the force pattern over a typical working period of the structure, using...

Use of finite elements for fatigue analysis A Element types A Beam elements

1 Beam elements are mainly used for analysis of nominal stresses in frames and similar structures. A conventional beam element for analysis of three dimensional frames has 6 degrees of freedom at each end node three displacements and three rotations. This element can describe the torsional behaviour correctly only in cases in which the cross section is not prone to warp, or warping can occur freely. Analysis of warping stresses is impossible, when open thin-walled structures are analysed. 2...

Partial Safety Factors for Fatigue Loading

1 Where the fatigue loading has been derived in accordance with the requirements of 3.2 a partial safety factor on load intensity yFf i gjmay be assumed to provide an acceptable level of safety. 2 Where a fatigue loading has been based on other confidence limits than those in 3.2 4 , an acceptable level of safety may be assumed to be provided by applying the partial safety factors on loading in Table 3.4.1. Table 3.4.1 Partial safety factors for fatigue load intensity yFf Table 3.4.1 Partial...

Control of welding quality

Welding Discontinuity Image

1 The manufacturer shall conform with the quality requirements of EN 729-2. D.1.2.2 Welding co-ordination 1 The welding co-ordination personnel shall have comprehensive technical knowledge in accordance with EN 719. 1 Welding procedures shall be approved in accordance with EN 288-4. D.1.2.4 Welder approval 1 Welders shall be approved in accordance with EN 287-2. D.1.2.5 Welding processes 1 Control of welding shall be in accordance with EN 1011-1 and 4. D.1.3 Methods and extent of Inspection 1...

National foreword

This Draft for Development is the official English version of ENV 1999-2 1998. This publication is not to be regarded as a British Standard. It is being issued in the Draft for Development series of publications and is of a provisional nature. It should be applied on this provisional basis, so that information and experience of its practical application may be obtained. Comments arising from the use of this Draft for Development are requested so that UK experience can be reported to the...