Chapter 15
Approximate shaft dimensioning according to Niemann 2001, 3. edition, page 742

For the design engineering of shafts and axes with full circle profile, the required dimensions will be estimated with an approximate calculation assuming that the main load is well-known. The permissible nominal stress (torsion) will be set so low that the bending stress, which is disregarded, can be taken into consideration, as well as the increasing stress by forces of impact (external forces), notches, cross sections, etc. For the design of the axes with bending load, the nominal bending stress is assumed (from Niemann 2001, 3.edition p.741).

The material can be selected for the calculation from the database. It is also possible to use individual material by the default of the maximum permissible torsion and bending tension.

15.1 The material selection

For the calculation the material can be selected from the following listbox.

In case you cannot find the material you are looking for in our extensive material database, you can define also your individual material. You will find the entry ‘User-defined’ in the listbox. If you select this entry, the input fields will be enabled, so that you can specify your own input values.

15.2 The material number

For every material there is an appropriate material number which is displayed automatically with the selection of the material. Alternatively to the material description, you can also select the material via the listbox ‘Material number’. If you have defined an user-defined material, then the value ‘0.0000’ is entered into the listbox ‘Material number’.

15.3 The load types

For the calculation four different load types are available:

• Idle axle (bending)
• Circulating axle (bending)
• Shaft (torsion)
• Shaft (torsion and bending)

• Idle axle: Usually repeated load and impact load are superimposed to the static base load, therefore a fluctuating stress is assumed for the dimensioning and the permissible bending stress is derived dependent upon the alternate strength.
• Circulating axle: For the determination of the permissible reversed bending stress, superimposed repeated and impact load have to be considered as well.
• Shaft: Bending and torsional moments are the main factors influencing shaft design. For the dimensioning you have to differentiate between shafts where only a torsion acts on the shaft or shafts that transmit also bending stresses. Accordingly, the permissible nominal tension has to be estimated differently.

After the input of the load - bending and torsion load or both - as well as the desired safety factor the required minimum diameter of the axle or shaft is determined.

15.4 Further possibilities

Click on the link ‘More calculation modules...’ and you will get to our web site. Here you find the free calculation modules as well as the possibility to register for a free test account to use also the other modules (e.g., the shaft calculation, the spur gear calculation, spring calculation) (find more information in section 2 ‘The registration’).

Please note: With the registration for a free test account, you will get a password. You will need this password to login to the eAssistant. You get to the project manager. The windows ‘Calculation type’ enables you to start the free of charge modules. If you use these modules, no time will be subtract from you time account (find more information in section 3.7 ‘The time account’).

Our manual is improved continually. Of course we are always interested in your opinion, so we would like to know what you think. We appreciate your feedback and we are looking for ideas, suggestions or criticism. If you have anything to say or if you have any questions, please let us know via telephone +49 (0) 531 129 399-0 or email eAssistant@gwj.de.