Standards related to:

GB/T 17855-2017GB/T 17855-2017

GB

NATIONAL STANDARD OF THE

PEOPLE’S REPUBLIC OF CHINA

ICS 21.120.30

J 18

Replacing GB/T 17855-1999

Calculation of load capacity of spline

ISSUED ON: SEPTEMBER 07, 2017

IMPLEMENTED ON: APRIL 01, 2018

Issued by: General Administration of Quality Supervision, Inspection and

Quarantine of PRC;

Standardization Administration of PRC.

Table of Contents

Foreword ... 3

1 Scope ... 4

2 Normative references ... 4

3 Terms and codes ... 4

4 Load analysis and calculation ... 7

5 Factor ... 13

6 Calculation of load-bearing capacity ... 15

7 Examples ... 19

Calculation of load capacity of spline

1 Scope

This standard specifies the calculation method for the load capacity of

cylindrical straight tooth involute splines and cylindrical rectangular tooth

splines (hereinafter referred to as splines).

This standard applies to splines manufactured in accordance with GB/T 1144

and GB/T 3478.1. Other types of splines may refer to this standard.

2 Normative references

The following documents are essential to the application of this document. For

the dated documents, only the versions with the dates indicated are applicable

to this document; for the undated documents, only the latest version (including

all the amendments) are applicable to this standard.

GB/T 1144 Straight-sided spline - Dimensions, tolerances and verification

GB/T 3478.1-2008 Straight cylindrical involute splines - Metric module side

fit - Part 1: Generalities

3 Terms and codes

Terms and codes are as shown in Table 1.

Rectangular spline:

4.2.4 Calculation of shaft load F and bending moment Mb:

The shaft load F and bending moment Mb of the spline pair shall be calculated

after force analysis according to the specific transmission structure.

5 Factor

5.1 Use factor K1

The use factor K1 is mainly a factor that considers the influence of power

overload caused by external factors of the transmission system. The impact of

this overload depends on factors such as the characteristics of the prime mover

(input) and the working machine (output), the mass ratio, the mating nature and

accuracy of the spline pair, the operating status, etc.

The coefficient can be obtained by precise measurement, or it can be

determined after analyzing the whole system. When the above method cannot

be realized, it can refer to Table 2 for values.

Table 2 -- Use factor K1

5.2 Tooth side clearance factor K2

When the stressing state of the spline pair is as shown in Figure 4, the load on

the teeth of the involute spline or rectangular spline depends on the elastic

deformation of the key teeth; it also depends on the size of the side clearance

of spline pair. Under the action of the shaft load, as the backlash changes (half

of the circumferential gap increases, the other half of the circumferential gap

decreases), there will be a relative displacement e0 between the two axes of

the inner spline and the outer spline, as shown in Figures 4 and 9. The

magnitude of the displacement e0 is related to factors such as the size of the

backlash (clearance) of the spline and the level of manufacturing accuracy.

After the displacement occurs, the load is distributed on fewer key teeth (the

self-centering effect is lost for the involute spline), which affects the load-

bearing capacity of the spline. The side clearance factor K2 considers of this

impact, usually K2 = 1.1 ~ 3.0.

When the shaft load is small and the accuracy of the spline pair is high, it may

take K2 = 1.1 ~ 1.5; when the shaft load is large and the accuracy of the spline

pair is low, it may take K2 = 2.0 ~ 3.0; when the shaft load is zero and only

bearing the rotational moment (see Figure 2), K2 = 1.0.

5.3 Distribution factor K3

When the two axes of the inner spline and the outer spline of the spline pair are

coaxial, the theoretical backlash (single tooth backlash) of the spline pair is

different due to the influence of cumulative error of the tooth pitch (indexing

error); the load on each key tooth is also different.

The distribution factor K3 considers this influence. For the spline pair before

running-in, when the accuracy is high (the precision rectangular spline

according to the GB/T 1144 standard or the accuracy level according to the

GB/T 3478.1-2008 standard is level 5 or higher), K3 = 1.1 ~ 1.2. When the

accuracy is low (the general use rectangular splines according to the GB/T 1144

standard or the accuracy level according to the GB/T 3478.1-2008 standard is

lower than level 5), K3 = 1.3 ~ 1.6. For the spline pair after running-in, when

each key tooth is involved in the work, and the load is basically the same, take

K3 = 1.0.

5.4 Axial eccentric load factor K4

Due to the tooth orientation error produced during the manufacture of the spline

pair and the concentricity error after installation, as well as the torsional

deformation after being loaded, the load on each key tooth along the axial

direction is uneven. The axial eccentric load factor K4 is used to consider this.

Its value can be selected from Table 3.

For the spline pair after running-in, when the axial load distribution of each key

tooth is basically the same, it takes K4 = 1.0.

When the accuracy of the spline is high and the indexing circle diameter D or

the average circle diameter dm is small, the axial eccentric load factor K4 in

Table 3 shall be the smaller value, and vice versa.

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