Effect of Environment
1 P The detail category Aac given in Tables 5.1.1 to 5.1.5 and 5.2.2 shall be reduced in accordance with Table 5.4.1 for certain combinations of alloy and environment where the average ambient temperature during the life does not exceed 65 C. NOTE For marine environment the average ambient temperature during the life should not exceed 30 C. Table 5.4.1 Number of detail categories by which Acc shall be reduced according to Table 5.4.1 Number of detail categories by which Acc shall be reduced...
E Peening
1 The largest benefits are normally obtained with methods where compressive residual stresses are introduced. The most common methods are hammer peening, needle peening, and shot peening. Peening is a cold working process where the impact of a tool deforms the surface plastically. The surrounding elastic mterial will compress the deformed volume. High compressive service loading can decrease the level of residual stress and must be taken into account when applying random loading spectra. 2...
G Enhancement of fatigue strength
1 For applied stress ratio values less than R 0,5 the reference fatigue strength Aac may be enhanced by an R ratio factor f R where the enhanced reference fatigue strength Aa at 2 x 106 cycles is given by 2 The value of f R depends on the value of R and the type of component and detail see G.2 . 3 The fatigue strength at 104 cycles should not be enhanced. 4 The basic slope mi R of the enhanced Aa-N curves shall be adjusted in accordance with the values of Ac at 104 and 2 x 106 cycles see fig....
Normative References
1 This European PreStandard incorporates by dated or undated reference, provisions from other standards. These normative references are cited at the appropriate places in the text. EN 287-2 Approval testing of welders - Fusion welding - Part 2 Aluminium and its alloys EN 288-4 Specification and approval of welding procedures for metallic materials - Part 4 Welding procedure tests for the arc welding of aluminium and its alloys. EN 485 Aluminium and aluminium alloys - Sheet, strip and plate EN...
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,...
Fatigue strength Detail Categories
5.1.1 Factors affecting detail category 1 P The fatigue strength of a detail shall take into account the following factors a the direction of the fluctuating stress relative to the detail b the location of the initiating crack in the detail c the geometrical arrangement and relative proportion of the detail. 2 The fatigue strength may also depend on the following e the material unless welded g the degree of inspection after fabrication h the quality level in the case of welds and castings . 1...
Inspection and Workmanship Acceptance Levels D Welded Joints D General
1 These requirements are essential to ensure safe application of the design rules see 1.4 2 P 2 The required quality level for each welded joint shall be obtained from the detail drawings see 6.2 . 3 Quality levels above Normal are indicated by a 'Fat' number and an arrow. 4 Where no 'Fat' number exists at a joint it shall be assumed that Normal quality level only is needed. 5 Where a 'Fat1 number exists at a joint, but with an arrow in one direction only, it shall be assumed that Normal...
Design Assisted by Testing
1 P Verification of the fatigue resistance of a design by appropriate testing shall be accepted as an alternative method to those given in 2.2 and 2.3. 2 P Where there are insufficient data for complete verification of a design by calculation alone in accordance with 2.1 or 2.2, supplementary evidence shall be provided by a specific testing programme. In which case test data may be required for one or more of the following reasons a The applied loading history or spectrum, for either single or...
B Principles B Flaw dimensions
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
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...
National Applications Documents
In view of the responsibilities of authorities in member countries for the safety, health and other matters covered by the essential requirements of the CPD, certain safety elements in this ENV have been assigned indicative values which are identified by . The authorities in each member country are expected to assign definitive values to these safety elements. Some of the harmonised supporting prestandards, including the Eurocodes giving values of actions to be taken into account and measures...
Definitions
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...
Design Documents
1 P The drawings shall contain full details of all connections which are susceptible to fatigue, including component dimensions and fit-up tolerances, sizes and types of fastener, and weld throat, leg and penetration dimensions. 2 P The required fatigue class shall be indicated for the relevant welded joints in accordance with 6.2. 1.7.2 Manufacturing specification 1 P The manufacturing specification shall include all special requirements for material preparation, assembly, joining, post...
Prenorme Europeenne Europische Vornorm
Descriptors civil engineering, steel construction, aluminium, design, building codes, computation, mechanical strength This European Prestandard ENV was approved by CEN on 26 October 1997 as a prospective standard for provisional application. The period of validity of this ENV is limited initially to three years. After two years the members of CEN will be requested to submit their comments, particularly on the question whether the ENV can be converted into a European Standard. CEN members are...
A 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
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...
C Derivation of endurance data C Component testing
1 Whenever force spectra or stress history data are known component testing can be done to verify the design of critical parts of the structure. The component to be tested should be manufactured to exactly the same dimensions and procedures as are intended to be used in the final design. All these aspects should be fully documented before manufacture of the test component is carried out. In addition any method of non-destructive testing and the acceptance criteria should be documented,...
C 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...
Derivation of Fatigue Loading
1 P Loading for fatigue shall normally be described in terms of a design load spectrum, which defines a range of intensities of a specific live load event and the number of times that each intensity level is applied during the structure's design life. If two or more independent live load events are likely to occur then it will be necessary to specify the phasing between them. 2 P Realistic assessment of the fatigue loading is crucial to the calculation of the life of the structure. Where no...
Equivalent Fatigue Loading
1 P A simplified equivalent loading shall only be used in place of a more realistic fatigue loading if the following conditions are satisfied a The aluminium alloy structure shall fall within the range of basic structural forms and size for which the equivalent fatigue loading was originally derived. b The real loading shall be of similar intensity and frequency and be applied in a similar way to that assumed in the derivation of the equivalent fatigue loading. c The values of mi, m2, ND and...
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...
A 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...
D Control of welding quality
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...
A References
A.4.1 Peterson, R. E 'Stress concentration factors1 John Wiley and Sons Inc., 1974. A.4.2 Roark, J. R. and Young, W. C 'Formulas for stress and strain1, McGraw Hill, 1973. A.43 Niemi, E. 'Stress determination for fatigue analysis of welded components1, International Institute of Welding document 1221-93 , Abington Publishing, Cambridge, 1995. A.4.4 BS7608 'Code of practice for fatigue design and assessment of steel structures',British Standards Institute 1993. A.4.5 Hobbacher, A...
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...
E Dressing by TIG or plasma
1 While TIG welding is only a practical process for structures made of plates 4mm thick or less, it can be used for improving the fatigue strength in cases where the weld toe is the critical site. When re-melting the existing toe region inclusions and undercuts can be removed and the toe radius can be increased which reduces the local stress concentration factor. 2 Standard TIG dressing equipment can be used, without the addition of any filler material. TIG dressing is sensitive to operator...