GB2585272A - Comparable stress for rolling bearings - Google Patents

Abstract

A computer implemented method for simulating the operating resistance for the formation of cracks in a rolling bearing 100 with respect to the damage mode WEC (White Etching Crack) is provided. WEC is noticeable by various phenomena such as breakouts or axial cracks on the rolling bearing 100. The damage is caused by cracks and/or a network of cracks which are initiated under a load at a distance yM below the bearing raceway 110 on an inner ring 101, on the bearing rollers 102 or below the bearing raceway 111 on the outer ring 103. An occurring stress σoccurring is formed out of the occurring load and compared with a permissible stress σpermissible in the defined material depth yM, taking account of the time-dependent stress levels of the occurring and permissible stresses. The simulation permits the user to judge whether this damage occurs due to the given operating conditions and the chosen material properties.

Description

Comparable Stress for Rolling Bearings

Description

The invention relates to a method according to the preamble of claim 1 and a method according to the claims 6,7 and 8.

Rolling bearings are used in all areas of technology, for example in transmissions, as axle bearings or electric motors and engines.

Figures 1, 2 and 5 show an example of rolling bearings in the embodiment as radial bearings and thrust bearings. A good overview of the existing bearing designs that can be considered in the method shows the Chapter C6 in Appendix C of IEC 61400-4 [11].

Bearings are usually made from bearing steel. The steel is mostly through hardened and has a material microscopic structure martensite or bainite, there are also case-hardened bearings and bearings with ceramic components.

The invention relates to rolling bearings made of steel. The most common steel is 100Cr6. In [12] various bearing steels are described with their properties. These can be taken into account in the method.

Bearings can be calculated according to ISO 281, part 1 and part 4 [3,4]. Here the nominal life and the modified reference service life is calculated for universally loaded bearings. The approaches used in these standards go back to the book Acta Polytechnica Scandinavica Mechanical Engineering Series No. 137 entitled "An Analytical Formulation for Life of Rolling Bearings" by E. loanides, G. Berg Ling and A. Gabelli. [5] From basic dynamic load ratings and loads, fatigue lives are calculated, taking into account operating conditions and lubricant properties.

An overview of the currently existing calculation options is shown in Figure 5 of IEC 61400-4 [11]. Here also a clear position is made to the calculation options for pitting in Section 7.3.4.2.

For about 30 years a failure mode can be observed which is formed by undirected cracks below the contact surface and which leads for example to the failure mode pitting, flaking or cracks on the bearing raceway.

This type of damage is called WEC White Etching Crack. The simulation by the method according to the preamble of claim 1 allows the user to judge whether that damage occurs under the given operating conditions and the chosen material properties.

Special awareness of this form of failure mode was caused by damages on rolling bearings in wind turbine gearboxes. The damage is significant and the failure mode is also reported by Johan Luyckx, "WEC failure mode on roller bearings", VD, Wissensforum, Tagung Gleit-and Walzlager Schweinfurt, Dusseldorf 2011. [8] The damage WEC (White Etching crack) occurs far before the calculated fatigue life according to ISO 281-1 and 4 [3.4] and the specifications for the design of rolling bearings in accordance with IEC 61400-4 [11] for wind turbine gearboxes and is also known from publications as White Structure flaking, flaking early at stage, subsurface Initiated flaking or white flaking structure.

Even with contact stresses far below the recommended contact stresses in IEC 61400-4 [11] Table 7, this damage is observed.

Till today in literature, there is no calculation method known for this form of damage. The cracks and crack networks have been and are observed to a depth of about 20 microns up to about 1.5 mm, There are many possible influences that can favour this form of damage. In [13] it is reported to these.

In the laboratory and on experimental devices [10, 13] this damage may be generated for example when hydrogen is present, a so-called "low reference" oil is used or eddy current is passed through the bearing location.

Reproducibility with common industrial gear oils and oil viscosities and under real operating conditions, that means below the stresses indicated as maximum contact stresses in IEC 61400-4 [11] Table 7 is not known.

Since about 2012, the Power Transmission Research Association FVA does research with respect to this failure mode under the titel " Geffigeveranderungen in Walzlagerringen mit Rissen als Folgeschaden, Vorhaben FVA 702 I, Heft 1121" [10] The damage leads to failure of the bearing. When a rolling bearing is at risk for this form of damage, a failure occurs for example in wind power transmissions within the first 3 to 24 months after commissioning very likely although the calculated bearing life according to IEC 61400-4 [11] is far greater than 20 years.

Also with gears early failures were observed in transmissions called flank fracture or TFF (Tooth Flank Fracture) and as the damage WEC these damages occur far before the calculated life.

In DE 10 2017 209 512 Al " Vergleichsspannung fur Zahnflanken " [1] a method is described by which the damage flank breakage can be reliably prevented. This process is explained in detail with clear example calculations in the publication "Calculation of Tooth Flank Fracture Load Capacity acc. to the method of Leimann "CWD Congress, in March 2019, Aachen. [6] The examples are dealing with both, sets of gears used in wind power, as well as gearing from laboratory tests. Till today, no case is known where the procedure gives an incorrect assessment and more than 100 in load and sort gears different were calculated.

This method describes the calculation of a possible crack formation below the contact surface of two mating tooth flanks in a given material depth.

The invention is based on the object to develop also method for rolling bearings, which takes into account the defined load and defined factors and transfer them so, that for the failure mode WEC a proposal can be made whether the damage may occur in the examined bearings under the given operating conditions and if a safe and reliable operation for the intended service life is possible.

Also the power density can exploited for use or be increased without increasing the risk of damage.

This task is inventively achieved by a method according to claim 1 and a method according to claims 6,7 and 8.

In the method according to claim 1 and claims 6, 7 and 8 is a computer implemented method that simulates the operating resistance of a bearing.

The technical and physical conditions are described in the following steps: - Determination of the load P which has to be used for the calculation of the occurring and the permissible stress for the strength comparison - determination of the material depth ym where the occurring and the permissible stress is calculated for the strength comparison - calculation of the occurring stress aocet,,,,8 in the material depth ym - calculation of the permissible stress Opermissable in the material depth Ym - calculation of the time-dependent correction factors f p for the occurring and allowable stress - Special consideration of sliding conditions in the bearing for contact stresses below 800 MPa - determination of the factors described in the following for the notch effect, materials and surfaces The invention makes use of the knowledge that, as described in DE 10 2017 209 512 Al [1] " Vergleichsspannung fur Zahnflanken ", a occurring compressive stress increases the strength. Furthermore, the invention makes use of the knowledge that an occurring stress after loading not immediately relax after unloading, there is instead a temporal profile of the stress and relaxation which increases or reduces the medium stress, and can even lead to a higher or lower maximum stress. This is important since this experience gives for roller bearings particularly by the number of rolling elements and the associated rollovers per revolution and a corresponding speed different stresses compared to today's computing models.

Without considering the temporal profile of the occurring stress and temporal profile of the permissible stress, taking into account the occurring compressive stress and the permissible stress and the depth y M in which the comparison takes place, is not possible to make a statement for the risk to get WEC.

According to the invention this knowledge is taken into account in the steps of calculating the occurring stress voltage ao.ong and the calculation of the permissible stress apermissable and in the in advance explicitly determined depth of examination ym and the stresses are according to the invention multiplied by the correction factors f time c,p.

The steps of the process are described in detail: (Note: All stresses are regarded as Sigma stresses and are scalar.) 1 Determining the load from which the equivalent load Papplication is calculated according to the invention: * Pcalculation = Papplication KA* KV * YWEC with PapparatIon = equivalent load from the application KA= application factor for the application Kv = Dynamic factor YtArtc = special factor for the failure mode WEC taking into account the special operating conditions and material properties Preferably under normal operating conditions and with conventional bearing materials the factor YwEc should be set to 1.

2. The determination of the occurring and permissible voltage is according to the invention: 2.1 calculation of the permissible stress Opermissible ym apermissible yM = (ap-HVNMYF ap-liertz(yM)*fcHertz Cp-residual(yM) ) X f3m X Pc X f time_p Here part of the stresses may become 0.

2.2 Calculation of the occurring stress °occurring yM CroccurrIng yM= (Co-comp Hertz (yM) + Co-friction (yM)+ Cro-hoop (yM) ) X 2k (yM) X f time_o Here part of the stresses may become 0.

2.3 Value of the Hertzian contact stress pH, which is used in the method: With the equivalent bearing load Pcalculation the Hertzian contact stress of the loaded highest rolling element is calculated taking into account the operating bearing clearance and the associated load distribution of the rolling elements which can be done by a skilled person with corresponding bearing programs. [2,9] The Hertzian contact stress pH could also be calculated with the simplified equations mentioned in the amendment C of the IEC 61400-4 [11].

2.4 Calculation of the half width contact of the Hertzian contact stress for roller bearings This is calculated differently from the literature [2] by X x Peak:Luau.. X (1 -v2) 7EXEXiX 1) E-did-T2 With: v = 0,3 E= 2,1 x 105 Nimm2 I = length mm The value X can take on values from 1to 4 Preferably, according to the invention: X = 2.

2.5 Calculation of the half width contact of the Hertzian contact stress for ball bearings Is calculated according to literature and is known to a skilled person. [2] 2.6 Occurring stresses 2.6.1 Occurring stress from Hertzian stress Cro-comp Hertz (yM) az = \1 + { 1 + 2 * (*)2 yM ay = pH * 2 * 1 2 vm \ ax = pH * -2 *v * 1 + (b 2-) -(b1 The occurring stress from Hertzian stress flio comp Hert2 UM)iSt: Cro-comp hertz (yM) = *((ex -502 + ((Ty -602 + ff-02) 2.6.2 Determination of the friction stress in the considered method on ThcHanym: The friction stress is determined in this method from the frictional torque of the rolling bearing: Friction moment M according to [2] M=Mo+Mi Friction moment no load Mo: MO = f0 X 10-7 X(vX n.)3 x T3 b V1+(b)2

I with

fe factor bearing type v oil viscosity at operating temperature mm2/s n speed rpm T Bearing pitch diameter mm Friction moment under load M1: = x x P x-2 with fi factor load direction pi friction coefficient Friction force FfrictIon = : 1:friction = M x2/42 Since WEC is observed even at a low bearing loads in the field, higher shear stress values are taken into account in this method, when the Hertzian contact stress is <800 MPa.

For this purpose, a correction factor is defined in the invention with X x 106 fHertz<800MPa pi] The values for X are between 1 and 5 and are dependent on the bearing type and design. In practice, values are between 2 to 4 In another embodiment of the invention, the value is 3,2.

The friction stress Cro-Friction (yM) is calculated according to the invention for instance for roller bearings as: Ffriction * H(yM) ao-Friction(yM)- X f Hertz< 800 MPa /y * 1 2.6.3 Hoop stress a. hoop y(M) The hoop stress is a result of the shaft and bearing tolerances, and is determined in accordance with the customary calculation methods [2]and is known by a skilled person. In the English language, this stress is also called the Hoop Stress.

2.7 Permissible stresses 2.7.1 Permissible stress from the hardness of the material ap.Hv(ym) The permissible stress from the hardness of the material ap_implynis calculated as: Op-HViyM)= Kper * Kmaterlal * HV yM) with HV = Vickers hardness For hardened roller bearing steel, the following values are set according to the invention: Krim' = 0,4 for martensite hardened Kper = 0,5 for bainite hardened Kmate al = 0,9 for martensite hardened Kmaterial = 0,95 for bainite hardened The K values for case-hardened bearings can be found in the literature [7] and known to a skilled person.

2.7.2 Correction factor for Hertz FcHertz According to DE 10 2017 209 512 Al [1] is fcHertz(az(yM)) = m 6z (y M) + 1 -m 60 with Tit = -Gro For rolling bearings is set: Go= 1000-1300 MPa for cylindrical and spherical bearings, preferable 1100 MPa Go= 1100-1400 MPa for taper roller bearings, preferable 1200 MPa Go= 1000-1500 MPa for ball bearings, preferable 1300 MPa 2.7.3 Compressive stress out of the Hertzian contact stress ap-Hertz(yM) This is calculated according to: 0-Hertz(yM) = az(yM) =- 2.7.4 Residual stress For case hardened bearings the residual stress is calculated according to literature and is known to a skilled person. [7] For martensitic hardened or bainitic hardened bearing steels is ap-residual(yM) -= 2.7.5 Material Factor gm The material properties of various bearing steels and external influences that weaken it are considered in the material factor Rm.

According to the invention is: 13m can have values between 0,8 and 1,2.

Preferable is: Rm = 1 for standard bearing steels rim = < 0,95 if influences are present that weaken it => 1.1 for extreme good material properties, as for instance Cronidur30, [12] 2.7.6 Surface factor Re The surface factor Re considered surface refinements such as black oxidizing.

Black oxidizing has in practice proved to be positive to reduce damage for WEC.

According to the invention is: Re can have values between 0,8 and 1,2.

Preferable is: Re -1 for standard surfaces Re =>_ 1.1 for black oxidized surfaces f3c = < 1 for damaged surfaces by for example grinding influences such as grinding burn 2.7.7 Notch factor for material inclusions k (yM) in the depth of evaluation yM The notch factor can be calculated according to DE 10 2017 209 512 Al [1] (1+ w + h)3 flic (3/11/) = 1 ± 540 mins Material inclusions can be for example of Aluminum oxide.

Preferably, the values for the length L = 0.2 mm, width w = 0.2 mm and height h = 0.2 mm for today's conventional bearing steels or to use the values which is specified for the corresponding material quality.

For the calculation of certain damage, the measured values must be used.

3 Depth of evaluation for the stresses yM The depth of evaluation yM for the stresses is defined according to the inventions a as a multiple of the elastic deformation 5K caused by the equivalent bearing load P application.

According to [2] a the skilled person can calculate the elastic deformation 6K for example for line contact with: 4,05 PRerechnung "25

SIC X

weff 0,85 For point of contact the equations are for instance to be used as mentioned in [2].

According to the invention the depth for the comparison of the occurring stress and the permissible stress yM should be: For line contact is set: Cylindrical and spherical roller bearings ym = 2... 10 x 6)( dependant of the design, Preferable ym = 4... 6 X OR In another embodiment of the invention the value is5.

Taper roller bearing yM = Z x (tan(ao) x 8k)x with values for X = 0,2 0,8, dependant on the design, preferable X= 0,4..0,6 In another embodiment of the invention the value X= 0,5.

With values for Z = 1... 3, dependant on the design, preferable Z= 1,2...1,8 In another embodiment of the invention the value is Z= 1,5.

For point contact is set: Ball bearings: ym = Z x (tan(ao) x 810x with values for X = 0,2 0,8, dependant on the design, preferable X= 0,4..0,6 In another embodiment of the invention the value is X= 0,7.

With values for Z = 1... 3, dependant on the design, preferable Z= 1,2...1,8 In another embodiment of the invention the value is Z= 1,2.

4 Time factor ftime_o,p The time factor takes into account the increase or reduction of the occurring °occurring and permissible stresses °permissible: The factor depends on the number of number of contacts N c and the cage speed nit of the bearing.

This can be calculated by an expert according to the literature. [2] In the case of full complement bearings, the virtual cage speed has to be determined. According to the invention the correction of the permissible stress opermissibleiS: fZeit p 1 Nc k.10000y x 1,2 And for cage speeds lower than 300 rpm is set: 1 300 flit k10000 ( A r)6 X 1,2 fZelt p = According to the invention the correction of the occurring stress °-occurring is: fZeit o = Np51i And for cage speeds lower than 150 rpm is set: 1 nk fzettfi = Neso x 5. safety factor SWEC Upermissible The safety factor SWEC is calculated as follows: SWEC = 0-occurring In a preferred embodiment a bearing is classified as safe in operation if the condition is met: 0-permissible yM SWEC yM = 1,05 CroccurrIng yM

In addition, the following statement can be made:

safety factor SwEc ni <0,95 0,95... 1,05 > 1,05 unsafe action required safe Failure likely could fail Failure unlikely under the known operating conditions 6 Summery and result Figures 3 and 4 show two results from the use of the method. Figure 3 shows a WEC endangered rolling bearing and figure 4 shows a WEC safe bearing. From the figures, it is clear how critical the assessment of a WEC damage is when the depth is chosen wrong.

The correct definition of the assessment depth is therefore very important and is achieved according to the invention as shown in point 3.

For the comparison of the occurring and permissible stress carried out in the chosen depth y M, it is essential to consider the influence of the reduction or increase of the temporal stress curve as stated in point 4.

Due to manufacturing tolerances, manufacturing variations, material tolerances, hardness tolerances and variations in the load P * application the output the expected network of cracks is not necessarily always equal to the calculated output of the crack formation in the depth yM.

Figures: Figure 1 shows the side view of a rolling bearing as a radial bearing Figure 2 shows a sectional view A_A through the roller bearing and the considered depth of material ym Figure 3 shows the result of applying the method for a bearing with risk of WEC Figure 4 shows the result of applying the method for a bearing with no risk of WEC Figure 5 shows a sectional view through a roller bearing as a thrust bearing Used nomenclature Rolling bearing 101 bearing inner ring 102 rolling element 103 Bearing outer ring 104 bearing disk 1 bearing disk 2 raceway bearing inner ring 111 raceway bearing outer ring 112 raceway of bearing disk 1 113 raceway of bearing disk 2 Literature: Patent literature: [1] Leimann, Dirk-Olaf, Vergleichsspannung fur Zahnflanken, DE102017209512.1, 06 Juni 2017 Nicht Patentliteratur [2] Die Walzlagerpraxis, Eschmann, Hasbergen, Weigand, Brandlein, zweite Auflage, Oldenburg Verlag Munchen Wien, 1978 [3] ISO 281 Beiblatt 1 dynamische Tragzahlen und nominelle Lebensdauer, 2003 [4] ISO 281 Beiblatt 4 dynamische Tragzahlen und nominelle Lebensdauer, 2003 [5] Acta Polytechnica Scandinavica Mechanical Engineering Series No. 137 "An Analytical Formulation for Life of Rolling Bearings" von E. loanides, G. Bergling und A. Gabelli, Espoo 1999 [6] Leimann, Dirk-Olaf, Calculation of Tooth Flank Fracture Load Capacity acc. to the method of Leimann, CWD, Aachen, Marz 2019 [7] FVA Forschungsvorhaben Flankentragfahigkeit -Werkstofftiefe, Vorhaben Nr. 556 I, Forschungsvereinigung Antriebstechnik E.V., Frankfurt, Heft 1000, 2012 [8] Johan Luyckx, "WFC failure mode on roller bearings", VDI Wissensforum, Tagung Gleit-und Walzlager Schweinfurt, Dusseldorf 2011 [9] Technisches Taschenbuch, Paland et all, INA Walzlager Schaeffler oHG, Herzogenaurach, 1998 [10] Risse auf Lageringen, Geffigeveranderungen in Walzlagerringen mit Rissen als Folgeschaden, Vorhaben FVA 702 I, Heft 1121 [11] IEC 61400-4, design requirements for wind turbine gearboxes, 2012 [12] Brochure "Materials for Rolling Bearing Technology", Schaeffler, Herzogenaurach, 08-2015 [13] Influences on Generation of White Etching Crack Networks in Rolling Bearings, Jtirg Loos et al, Journal of Mechanics Engineering and Automation 6, 2016 Terms, symbols, units

Symbols description unit

Pi Friction coefficient b half width contact Hertz mm d, raceway bearing inner ring mm d2 raceway bearing outer ring mm E modulus of elasticity N/mm' f HoploaDOMPa correction for low contsct stress r frictinn friction force N fa factor bearing type f, factor load direction frIlertz correction factor for cyofermym) fon, cycle related correction factor for strength values fd,,t, cycle related correction factor for strength values h height of a material Inclusion mm H lymi moment of resistance mm' HV (.0,) Vickers hardness In the depth yM HV ly moment of Inertia mm" kA application factor Kmatenai material factor Ki," material factor dynamic factor length of the roller with cylindrical roller bearings mm length of a materia inclusion mm Wet real contact length of a roller mm M friction moment Nm m slope of a straight line -Mn friction moment no load Nm My friction moment under load Nm n speed rpm N, Number of contacts n, cage speed rpm P.PPlIcation equivilant bearing load N Pra.amanon bearing load from application N Pa contact stress Hertz MPa T bearing pitch diameter mm w width of a material inclusion mm X correction factor for calculation half width X correction factor for bearing type and execution -yM material depth for the calculation of Sv", mm YWEC special WEC Factor an contact angle for taper roller bearings and ball bearings a 0, surface factor 131( &Nil notch factor - (3M material factor 5,, elastic deformation under load mm v poisson number v oil viscosity at operating temperature mm'/s ao comparable stress N/mm2 oc""a" Occuring stress number N/mma °emelt% yl./1 Occuring stress number In material depth NNW lio-comp Hertz yM Occuring stress from Hertzian stress at depth yM Nimma op.,.*;eeeliyMl Permissable stress from residual stress at depth yM N/mma 0P-Hert2(0() Permissable stress from Hertzian stress at depth yM N/mm' 0mhiv(vm) Permissable stress from material strenght at depth yM N/mm' lie-hoop(yM) Occuring stress from hoop stress at depth yM N/mm'

Symbols description unit

tie Friction coefficient b half width contact Hertz mm di raceway bearing inner ring mm d, raceway bearing outer ring mm E modulus of elasticity N/mm' f Hertz<800MPa correction for low contact stress F friction friction force N f, factor bearing type -fi factor load direction fctiortz correction factor for apiiery)(m) ftimeo cycle related correction factor for strength values fumeep cycle related correction factor for strength values h height of a material inclusion mm H (ym) moment of resistance me HV me} Vickers hardness in the depth ym ITV I, moment of inertia mm4 kA application factor Kmaterial material factor Ice, material factor k, dynamic factor I length of the roller with cylindrical roller bearings mm I length of a materia inclusion mm lweff real contact length of a roller mm M friction moment Nm m slope of a straight line M0 friction moment no load Nm MI friction moment under load Nm n speed rpm N, Number of contacts nk cage speed rpm PapplIcation equivilant bearing load N Pcalculation bearing load from application N PH contact stress Hertz MPa T bearing pitch diameter mm w width of a material Inclusion mm X correction factor for calculation half width X correction factor for bearing type and execution Ym material depth for the calculation of SwEr mm YWEC special WEC Factor aff contact angle for taper roller bearings and ball bearings i.

Pc surface factor Pk (yM) notch factor Pm material factor Ss elastic deformation under load mm v poisson number v oil viscosity at operating temperature mm'/s a, comparable stress N/mm' Ffsmirring Occuring stress number N/mm' creeeeri",m Occuring stress number in material depth N/mm' ao-comp Hertz yM Occuring stress from Hertzian stress at depth ym N/mm' op-resiclual(yM) Permissable stress from residual stress at depth ym Ware araerigymi Permissable stress from Hertzian stress at depth ym N/mm'

Claims (8)

1. Comparable Stress for Rolling Bearings Claims 1. A computer implemented method for simulating the operating resistance of a rolling bearing (100) disposed on a shaft or axis, to evaluate the formation of cracks below the material surface in contact between the raceway of a roller bearing (110, 111, 112, 113) and the rolling bodies ( 102) comprising the steps of Calculating an occurring stress ("occurring as a measure of a occurring stress between the rolling element (102) and the raceway (110, 111, 112, 113) of the bearing (100); Calculating a stress -permissible as a measure of a permissible stress of the bearing rings and rolling bodies; Comparison of ap ermissible and -occurring; Comprising that: °occurring yM=(0-0-comp Hertz (yM) + Co-friction (yM) -o-hoop(yM) ) X Rk (yM) X f time_a and apermIssible yM (6p-HV(yM) + ap-Hertz(yM)*f cHertz Crp-residual(yM) ) X RM X Pc x f time_p and the occurring stress -occurring is multiplied with the time factor f um" and a notch factor (yM) and by this way corrected is with the time factor: fume_. N A If the cage speed is lower than 150 rpm the factor becomes: 1 nk f time = N Cso x And with the notch factor: + w + h)3 Ric (ym) -=-1 + 540 mni3 and the permissible stress o-p"mj"ible is multiplied with the time factor f tim", a material factor ENA and a surface factor 13, and by this way corrected is with the time factor: N itime_p = (10000/ 10000 X 1,2 And when the cage speed is lower than 300 rpm the factor becomes: ( 1 300 ftime p = i Nc \ 6 nk \1000 0) x 1,2 With the material factor Em with values between 0,8 and 1,2 And the surface factor E, with values between 0,8 and 1,2.
2. 2. Method according to claim 1; comprising that the depth ym where the occurring stress ooccurring and the permissible stress apermissible are judged multiple of the elastic deformation ok between the rolling elements (102) and the raceway (110, 111, 112, 113) is and is calculated from the equivalent bearing load P * calculation.
3. 3. method according to claim 1 and 2; comprising that, the equivalent bearing load Pcalculation is calculated from the nominal load of the application taking into account the application factor KA and the dynamic factor K.
4. 4. method according to claim 3; comprising that, the equivalent bearing load Pcalculation is additional multiplied with a WEC specific factor ywEc taking into account special operating conditions and material properties.
5. 5. Method according to one of the preceding claims; comprising that Operating resistance is critical if this condition is fulfilled: > aoccurring X SwEc permissable with a safety factor SwEc, where is set: SWEC > 1,05
6. 6. Method for operating a gear box; wherein the gear box comprises at least one bearing (100); wherein for the bearing a method according to any one of the preceding claims is carried out; wherein the bearing is loaded with a bearing load P * calculation; and the occurring stress Goccurring and the permissible stress 0-permissible is chosen in that way; that a sufficient safety S 1,05 is achieved.
7. 7. Method for operating a machine; wherein the machine comprises at least one bearing (100); wherein for the bearing a method according to any one of the preceding claims is carried out; wherein the bearing is loaded with a bearing load P calculation; and the occurring stress Goccurring and the permissible stress °permissible is chosen in that way; that a sufficient safety
8. 8. Method for operating a wheel axis; wherein the wheel axis comprises at least one bearing (100); wherein for the bearing a method according to any one of the preceding claims is carried out; wherein the bearing is loaded with a bearing load Pcalculation; and the occurring stress °occurring and the permissible stress apermissible is chosen in that way; that a sufficient safety S 1,05 is achieved.S 1,05 is achieved.