ESDU 74027-1974 零平均应力下表面粗糙度对钢材疲劳极限的影响

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THE EFFECT OF SURFACE ROUGHNESS ON THE FATIGUE LIMIT OF STEELS AT

ZERO MEAN STRESS

1. NOTATION

Both SI and British units are quoted.

2. NOTES

This Item provides data on the zero mean stress fatigue limit of steels having rough surfaces. There is a

variety of methods in use for the description of surface roughness; however, the peak-to-valley height

measure is the most pertinent to fatigue situations and is used throughout this Item. Other methods and

conversion to peak-to-valley height are discussed in Appendix A.

All steels contain minute flaws, the critical size of which decreases as the material tensile strength increases;

consequently, reduction of surface roughness, rt , to less than this flaw size produces no further improvement

in fatigue limit. This cut-off value of surface roughness is denoted by . At roughness levels below

failure will occur from these inherent flaws.

The data are presented in Figure 1 in terms of ksf plotted against rt for a range of values of tensile strength.

The form of the curves was decided not only by the data shown but also by the trends indicated by the

available qualitative data. There will be scatter about these lines for which, in critical situations, an

allowance should be made. Figure 2 is derived from Figure 1 and presents the curves alone up to a roughness

of rt equal to 500 µm (2 × 10–2 in). Also in Figure 2 are presented lines of constant ksf ft/2 for design

purposes. Figure 3 shows a curve of ft against , the surface roughness cut-off value, to enable the user

to check quickly to see whether or not surface roughness effects are significant. This curve was obtained

from Figure 1 by cross-plotting values at ksf = 1.0 . A line obtained by cross-plotting for values of ksf = 0.95

tensile strength N/m2lbf/in2

surface finish factor due to surface roughness defined by

surface roughness sampling length m in

centre-line-average height of surface roughness m in

peak-to-valley height of surface roughness m in

peak-to-valley height of surface roughness below which no

improvement in fatigue strength can be made min

fatigue limit alternating stress at zero mean stress with surface

roughness depth less than N/m2lbf/in2

fatigue limit alternating stress at zero mean stress with surface

roughness depth greater than N/m2lbf/in2

ksf

Ksf

Sp0∞()

∞()

------------------

rt0

Sa0∞()

∞()

t0r

Issued November 1974

ESDU product release: 2006-01. For current status, contact ESDU. Observe Copyright.

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is also given on Figure 3. Figure 4 is a cross-plot of Figure 1 with ksf plotted against ft for a series of values

of rt .

3. PEAK-TO-VALLEY HEIGHT OF SURFACE ROUGHNESS rt

3.1 Measurement of rt

Sketch 3.1 illustrates a section through a typical machined surface magnified many times. It appears as a

rough terrain of peaks and valleys. The surface undulations can be broken down into two textures

superimposed upon an error of form. The primary texture, or surface roughness, is produced, for example,

by the effect of the tool, by abrasions or by metallurgical structure factors. Secondary texture, or waviness,

results from eccentricity or misalignment of the production apparatus used.

Choice of sampling length (the length of surface examined by, for example, a stylus) is important. If a

sampling length L3 is chosen, as shown in Sketch 3.1, the effects of error of form will be seen as well as

those of waviness and surface roughness. If a sampling length of L2 is chosen, only waviness and surface

roughness will be recorded. If a sampling length of L1 is taken, then the effects of error of form and waviness

will be negligible and a reasonably accurate surface roughness trace will be found. A series of traces of

sampling length L1 must be taken to ensure representative results. Taking L1 equal to 0.8 mm will give

satisfactory results for most practical engineering surfaces (see Derivation 13).

Sketch 3.1 Characteristics of a machined surface

The peak-to-valley height of surface roughness is determined as shown in Sketch 3.2. The distance rt is the

maximum vertical deviation of the actual profile from the reference profile. The reference profile is a line

that touches the highest peaks within the sampling length. This line is straight for short sampling lengths

but may have the form of the geometrically ideal profile or may follow periodicity in the surface. The datum

profile is a line parallel to the reference profile that just touches the lowest valley within the sampling length.

ESDU product release: 2006-01. For current status, contact ESDU. Observe Copyright.

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The value of surface roughness that is of interest is that normal to the direction of applied stress. In combined

stress situations it may be necessary to take traces in several directions to ensure that the value of rt used

is the maximum.

Sketch 3.2 Measurement of peak-to-valley height of surface roughness

3.2 Interpretation of Surface Roughness Measurements

Table 6.1 shows several sections through machined and polished surfaces. Cases a, b, c and d show profiles

of turned surfaces and e, f, g and h show profiles of ground, lapped, hand polished and scored surfaces

respectively. These surfaces assume improvement of surface texture by the use of progressively finer

techniques. From these profiles it can be seen that different topographies may produce similar rt values. A

local scratch in an otherwise flat surface may give the same rt value as an overall rough surface. Cases b

and c, although nominally produced by the same method, show different surface roughnesses. This

emphasises the danger of classification of surfaces by production method and illustrates one reason for

scatter observed in surface roughness effects. The production process may induce residual stresses in the

material which can have a pronounced effect on the fatigue limit. These stresses are, however, usually

compressive and improve the fatigue properties of the material.

Defects that have been smeared over or surface cracks produced by careless grinding will not show up on

profile traces. Such defects may lead to premature fatigue failure especially in the higher strength steels.

4. DERIVATION

1. NIEMAN, G.

GLAUBITZ, H. Einfluss der Oberflächenrauheit auf die Biege-Wechselfestigkeit von

ungehärtetem und vergütetem Stahl. Z. ver. dt. Ing., Vol. 94, No. 25,

pp. 855-857, September, 1952.

2. SIEBEL, E.

GAIER, M. Untersuchung uber den Einfluss der Oberflächenbeschaffenheit auf die

Dauerschwingfestigkeit metallischer Bauteile. Z. ver. dt. Ing., Vol. 98,

No. 30, pp. 1715-1723, October, 1956.

Translation available as “The influence of surface roughness on the

fatigue strength of steels and non-ferrous alloys”, Engrs Dig., Vol. 18,

No. 3, pp. 109-112, March 1957.

3. FROST, N.E. A relation between critical alternating propagation stress and the crack

length for mild steel. Proc. Instn Mech. Engrs, Vol. 173, No. 35,

pp. 811-836, 1959.

ESDU product release: 2006-01. For current status, contact ESDU. Observe Copyright.

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摘要：

该标准规范 ESDU 74027-1974 系统研究了在零平均应力条件下，表面粗糙度对钢材疲劳极限的影响规律与量化关系。文档基于实验数据，提供了不同加工工艺（如抛光、磨削、车削、粗加工等）所对应的表面粗糙度参数与疲劳强度衰减系数的对应图表，旨在帮助工程师在设计阶段合理评估表面状态对构件疲劳寿命的削弱效应。该标准适用于承受交变载荷的机械结构件，尤其是在高周疲劳场景中，能够指导表面质量要求的制定与工艺选择，从而避免因粗糙度过高导致过早疲劳失效。对于从事疲劳强度分析、材料选择及表面工程的专业人员而言，

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ESDU 74027-1974 零平均应力下表面粗糙度对钢材疲劳极限的影响

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