Info Letter No. 56 - July/August 1999

Shearing stress calculation:

Tau max = MG/Wp

With

MG = FMmax*d2/2(P/(pi*d2)+1.155*µg)

WP = pi/16 * d0³ for elastic deformation

bis WP = pi/12 * d0³ for full plastic deformation

A bit strange about the VDI 2230 draft is that the polar surface inertia moment with WP=pi/12*d³ is used for full plastic deformation when the shearing stress is calculated with MG, as the friction moment surely results in full plastic transformation only in few cases. Therefore, SR1 calculates the higher shearing stress for elastic transformation, and the permissible flowing is considered by a minor shearing stress’s influence when calculating the (theoretical) comparative tension (factor 12/16=0.75).

Sigma red,B = (sigma²z + 3 (ktau*taumax*0.75)²)^0.5

Or

Sigma red,B = (sigma²z + 1.69 (ktau*taumax)²)^0.5

For a factor ktau=0.5 (suggestion VDI2230) follows

Sigma red,B = (sigma²z + 0.42 taumax²)^0.5

The shearing stress is nearly insignificant.

Unfortunately there is only one application example in the new VDI draft, this corresponds to example 3 of the old standard. Only the screw’s thread length was doubled from 10 to 20 mm. SR1 calculates a minimum screwing-in depth of 12.4 mm according to Dose’s expressions. In the new draft, the up-to-now incorrect calculation of the screwing-in depth has not been replaced by the practical Dose calculation, but by annother new theory.

The amount of setting calculation (so far dependant on the clamping length!) has been replaced, now roughly corresponding to Bauer & Schaurte’s methods used by SR1. In the calculation example, the setting force is now 4 times as large as according to the old VDI2230 !

For the screwing-in depth’s calculation at higher temperatures, the reduction of yield point and tensile stress of the nut thread has to be considered. Therefore, SR1 has been appended by a database MAT_P_RE.DBF. Similar to the screw’s yield point calculation, the yield point of the specified operating temperature is loaded from the database for the nut. Intermediate values are interpolated.

The tensile strength is diverted from the yield point, it is preconditioned that the relation of yield point and tensile strength is the same for every temperature.

Rmx = Rex * Rm20 / Re20

The amount of setting calculation according to the new VDI draft was taken over in SR1. Now, you can choose the calculation according to the old and the new VDI, and the screw’s Vademecum. The calculation according to Vademecum had to be corrected, as the number of discretionary hyphens had not been considered yet.

In the latest 32-bit version, problems appeared for 2 and more clamping plates at material changes, when the file was saved and later opened. The error was corrected, moreover, the material are now also shown in the list.

As size problems occurred with long texts and large numbers, the font height was decreased and the columns were widened.

The friction diameter is calculated according to VDI 2230 with

Dkm=(dw+dh)/2

So far, the expression Dkm = (dk+dh) / 2 with head diameter Dk has been utilized. Therefor, the tightening torque was smaller.

An extended version of SR1 is available now, which includes the calculation of the maximum load for a single bolt (FA, FQ, Fkreq) from the flange load. Thanks to Mr. Gerhard Friedrich Dose for his suggestions and help.

The price of SR1+ is 1470 DM, the upgrade price for SR1 to SR1+ is 280 DM.

A table drawing with geometry and result data for the calculated cross-section has been added to GEO1, our profile calculation software.

The database has been appended. Approximately 250 steels and alloys, respectively, and the following material groups have been added: Heat-resisting steel, High-temperature resisting steel/alloy, alloyed tool steel, non-magnetiziable steel, vavle steel, heat-resisting cast steel, stainless steel cast.

Following material's chemical compound has been corrected:

1.0402, 1.0406, 1.0501, 1.0503, 1.0511, 1.0528, 1.0535, 1.0540, 1.0601, 1.0756, 1.0757, 1.0758, 1.1133, 1.1151, 1.1158, 1.1167, 1.1170, 1.1178, 1.1181, 1.1186, 1.1191, 1.1203, 1.1206, 1.1221, 1.1231, 1.1248, 1.1269, 1.1520, 1.1525, 1.2362, 1.2731, 1.3505, 1.3520, 1.3536, 1.3543, 1.3549, 1.3551, 1.4003, 1.4109, 1.4110, 1.4112, 1.4120, 1.4122, 1.4125, 1.4306, 1.4310, 1.4311, 1.4313, 1.4404, 1.4418, 1.4439, 1.4462, 1.4465, 1.4512, 1.4521, 1.5023, 1.5024, 1.5028, 1.5142, 1.5637, 1.5662, 1.5680, 1.5752, 1.5919, 1.6511, 1.6582, 1.7001, 1.7002, 1.7003, 1.7006, 1.7020, 1.7030, 1.7033, 1.7035, 1.7108, 1.7138, 1.7149, 1.7218, 1.7220, 1.7225, 1.7228, 1.7321, 1.7323, 1.7361, 1.7362, 1.7707, 1.7735, 1.7779, 1.8159

The basis data of 1.7220 has been altered.

Instead of average stress and amplitude, min. and max. value may be entered.

Base data, chemical composition, fatigue limits, and international names may be entered in one dialogue window.

Spring angle and torque have been splitted to 2 lines, text size was increased, and dimension arrows are drawn solid filled. Thanks to Mr. Rottmann of Baumann-springs in Rüti/Switzerland for his improvement suggestions.

Because of the negative touch of the "-" sign for the light versions, it are named with extension "light" instead of "minus" in future.

If only one page shall be printed, you can configure this setting. The page shift is ignored then.

For text printout, font, style and size can be configured now.

For the text font used with drawings and diagrams, "bold" and "italic" attributes are supported now.

Font: Courier New

Style: Bold Italic

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