BS ISO 19690-1:2017 pdf download.Disc springs — Part 1: Calculation
1 Scope
This document specifies design criteria and features of disc springs, whether as single disc springs or as stacks of disc springs. It includes the definition of relevant concepts, as well as design formulae, and covers the fatigue life of such springs.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 16249, Springs — Symbols
ISO 26909, Springs — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 26909 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at www.iso.org/obp
— IEC Electropedia: available at www.electropedia.org
4 Symbols and units
For the purposes of this document, the symbols and units given in ISO 16249 and Table 1 apply.
6 Design formulae for springs
6.1 General
The following formulae apply to single disc springs with or without flat bearings, where 16 < D/t < 40 and 1,8 < D/d < 2,5. In the case of other designs or materials, it is recommended that the spring manufacturer should be consulted.
6.2 Test load
The test load of single disc springs, F t , is designed for a deflection s = 0,75 h 0 . Single disc springs with flat bearings shall have the same test load for a test height, H t , as ones without, where the principal dimensions D, d and H 0 are the same. Flat bearings have the effect of reducing the length of the lever arm. The increased load which results can be compensated by reducing the thickness of the disc spring. The load/deflection curve of such springs deviates from those without flat bearings, with the exception of the point at which the curves intersect.
8 Design stresses
Since there are residual stresses in the spring as a result of the manufacturing process used, the results obtained from Formula (10) to Formula (14) do not reflect the actual values involved, but rather any nominal values. Thus, all information relating to stress in this document represents these nominal values. An estimate of the permissible free overall height of the spring, H 0 , may be based on a determination of the design stress, σ OM , which should be about equal to the tensile strength. The most important parameter for springs subjected to fatigue loading is the calculated tensile stress on the lower side of a single disc spring. The position most vulnerable to fatigue failure will be either the lower inner edge, position II, or the lower outer edge, position III (see Figure 1 and Figure 7), depending on the ratios D/d = α, h 0 /t and s/h 0 . This is illustrated in Figure 7 and applies to springs with or without flat bearings. Since the ratio s/h 0 is a factor of influence with regard to the level of tensile stress at positions II and III, it is recommended, for the area between these positions, that σ II and σ III be determined in accordance with the formulae given in 6.5.
BS ISO 19690-1:2017 pdf download
