ESDU 92017-1992 铝合金十字形及其他角焊接头的疲劳强度

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FATIGUE STRENGTH OF CRUCIFORM AND OTHER FILLET WELDED JOINTS IN

ALUMINIUM ALLOYS

1. INTRODUCTION

This Item provides data on the fatigue strength of metal-inert-gas (MIG) cruciform and other fillet welded

joints in aluminium alloys, which are extensively used in welded structures and beams. The joints covered

by this Item are shown in Table 5.1 together with a full description.

A general description and analysis of the welding of aluminium alloys, including metallurgical and thermal

effects, is given in Data Item No. 91039*, which also includes an appendix which gives details of chemical

composition, typical filler alloys and the standard aluminium alloy and temper designation system.

2. NOTATION

Both SI and British units are quoted.

3. FATIGUE STRENGTH

3.1 Interpretation of Data

Fatigue strength test data are presented for cruciform and other fillet welded joints in the as-welded state

and with some post-weld treatments. Design codes such as BS 8118† (Reference 8) provide fatigue design

curves that should be conservative. A presentation of the available data, including the various factors

affecting fatigue strength, allows a better understanding of the fatigue behaviour of welded joints and may

be used in the analysis of failures. Such data are presented in this Data Item with a mean curve drawn

through each set, not as a design curve, but simply to indicate the trend. However, the available data are

*Data Item No. 91039 “Static and fatigue strength of butt welded joints in aluminium alloys”.

tensile strength N/m2lbf/in2

endurance

stress ratio,

nominal applied stress in absence of crack N/m2lbf/in2

alternating applied stress (half range) in loaded plate N/m2lbf/in2

mean applied stress in loaded plate N/m2lbf/in2

maximum value of S in loaded plate N/m2lbf/in2

minimum value of S in loaded plate N/m2lbf/in2

yield stress (0.2 per cent proof unless otherwise stated) N/m2lbf/in2

nominal thickness of loaded plate m in

†BS 8118 has recently replaced BS CP118 (Reference 7).

min/Smax

Sm1R

()

max/2

Smax

Smin

Issued August 1992

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limited and can therefore only give a guide to the factors that influence the fatigue strength. Most of the

factors that influence the fatigue strength of fillet welds in steel, such as the joint geometry and size, will

also be relevant to aluminium welds. These influences are described for steel welds in Data Item No. 75016*.

3.2 Fatigue Data

The fatigue data are presented in Figures 1 to 31 with mean S–N curves drawn through each set of data

points. All joints are illustrated in Table 5.1. The mean curves take the form of straight lines where possible.

The lower ends of these terminate at the value of for the lowest data point signifying a break or the

highest non-break data point if it appears higher. In this way, emphasis is given to actual failures. Table 5.2

details alloy composition and mechanical properties for each test material. All test details such as joint type,

stress ratio, dimensions and test conditions are given for each curve in Table 5.3, together with a summary

of mean fatigue strengths from the curves at endurances of 106 and 107 cycles. It must be stressed that these

values give only an indication of the mean fatigue strength and that confidence limits cannot be given due

to the nature and quantity of the test data.

The fatigue tests were carried out on test coupons, all of which were plate or sections less than 15 mm

(0.6 in) in thickness. Figures 1 to 20 cover load-carrying and non-load-carrying transverse and longitudinal

fillet welded joints, including cover-plate and cruciform joints (labelled A to M). Figures 21 to 31 give data

for single and double lap and tee fillet welded joints (labelled N1, N2, P1, P2 and P3). The fatigue strengths

of each joint type are shown collectively in summary Figures 32 and 33 for alloy 5083 and stress ratios of

0 and –1 respectively. Summaries of the fatigue strength mean curve values from these figures are given

in Tables 5.4 and 5.5. Scatter bands are also given in Figures 34 and 35 for each joint in all materials at a

stress ratio of 0.

The stresses quoted for each joint are the nominal stresses at the section where failure occurred, except for

joints C, D, N1, P1 and P2. In those cases, failure occurred in the weld throat; however the weld sizes were

not reported. The stresses quoted are therefore the cover-plate stress for joints C and D, the leg stress for

joints P1 and P2, and the stress in the main plates for joint N1, or in the 6061 alloy plate for N1 joints

between dissimilar alloys. The plate in which the quoted stress was acting is indicated for each joint in

Table 5.1 by a dashed line.

3.3 Factors Influencing the Fatigue Strength

There are many factors that will influence the fatigue strength of welded joints. Most result from the fatigue

strength of the plate in the region of the weld toe which is in turn influenced by the depth of weld penetration,

weld bead size or excessive porosity. In consequence of the many factors, there will always be a large scatter

in welded joint fatigue strength data. For the joints and materials in this Data Item, parent material tensile

strength was not a significant factor in determining welded joint fatigue strength. This can be seen in

Figures 36a and 36b which show the variation in fatigue strength with parent material tensile strength at

105 and 107 cycles respectively. However, parent material tensile strength may be significant in fatigue at

high stress levels and short lives, for example 103 cycles, and will influence the static strength of welded

joints.

The following sections discuss the main factors that affect the fatigue strength of cruciform and other fillet

welded joints.

3.3.1 Joint configuration and loading

The most significant factor affecting fatigue behaviour is the geometry of the joint configuration which

will give rise to stress concentrations. The higher the magnitude of stress concentration, the lower the

*Data Item No. 75016 “Fatigue strength of transverse fillet and cruciform butt welds in steels”.

2Sa

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resulting fatigue strength will be. The effect of joint configuration is shown clearly in Figures 34 and 35

where fatigue strength scatter bands are given for each joint type in all materials at a stress ratio of 0. The

data presented are mainly for specimens under axial load; however, Figure 31 presents data for tee fillet

welded joints under bending load. No data are reported for the case of reinforcing cover-plates on beams

loaded in bending.

The welds in cruciform and other fillet welded joints can be either load-carrying or non-load-carrying. The

summary Figure 33 gives mean fatigue strength curves from the data for 5083 alloy (extracted from

Figures 1 to 31) for load-carrying joints A and F and non-load-carrying joints B, J, K, L and M at a stress

ratio of –1. Leaving aside weld failures, it can be seen from Tables 5.4 and 5.5, and from the general data,

that joints with transverse welds had a higher fatigue strength than joints with longitudinal welds (due

mainly to stress concentrations at the ends of longitudinal welds). Also, within each group, joints with

non-load-carrying welds tended to have a higher fatigue strength than joints with load-carrying welds.

The effect of offset between plates is shown in Figures 1 to 3 for joint A. Due to the bending stresses

induced, the offset joints generally had a lower fatigue strength than those in which the plates were properly

aligned.

A description of the fatigue behaviour of each joint type follows.

3.3.1.1 Cruciform (A and B)

All cruciform joints reported have four transverse welds which can either be load-carrying (joint A) or

non-load-carrying (joint B). Joints of types A and B lie in the high strength band of fillet welded joints

reported here owing to the geometry and direct load path through the joint.

3.3.1.2 Cover-plate (C to H)

Welds in the cover-plate joints reported are load-carrying and can be transverse or longitudinal. In general,

joints with transverse welds have a higher fatigue strength as longitudinal welds usually introduce high

stress concentrations at the weld ends, and so lead to lower fatigue strengths.

3.3.1.3 Fillet attachment (J to M)

Any attachment to a stressed plate causes stress concentrations and the effect of this should not be

under-estimated. Non-load-carrying joints, J, K, L and M, give rise to more severe stress concentrations

than the load-carrying cruciform joint, A, so giving them a lower fatigue strength (see Figure 33).

3.3.1.4 Lap (N1 and N2)

Lap joints contain transverse, load-carrying welds but generally have a low fatigue strength due partly to

the additional bending stresses induced by the geometry of the joint.

3.3.1.5 Tee (P1 to P3)

The tee fillet welded joints for which data are presented in this Data Item have load-carrying transverse

welds except for joint P3 in which the leg is a non-load-carrying attachment to a plate subject to out-of-plane

bending. Double fillet welded tee joints generally have a high fatigue strength owing to the direct load path,

and have similar fatigue strengths and geometry to the cruciform joints. However, single fillet welded tee

joints have a poor fatigue strength owing to the asymmetry introduced which results in bending stresses.

One set of data is given for tee joint P3 under bending load. This joint has a higher fatigue strength than

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标签： #铝合金 #接头 #合金

摘要：

本文详细介绍ESDU 92017-1992标准中针对铝合金十字形及其他角焊接头疲劳强度的评估方法与技术数据。该标准为航空航天与结构工程领域提供关键的设计参考，涵盖焊接接头几何参数、应力集中效应、材料特性及疲劳寿命预测模型。通过系统分析铝合金角焊接头在不同载荷条件下的疲劳性能，本内容帮助工程师优化焊接结构设计，避免过早疲劳失效，适用于飞机结构、车辆框架及船舶建造等严苛疲劳环境。结合ESDU系列规范的权威性，本摘要为科研人员与设计师提供可直接用于选材、接头构造选择及耐久性校核的实用指南，确保焊接构件

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ESDU 92017-1992 铝合金十字形及其他角焊接头的疲劳强度

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