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Info Letter No. 76 - November/December 2002

by Fritz Ruoss

FED1+, FED2+ Spring Database

Search time for a spring in the spring database could be reduced to 50% by means of a new filter routine.

FED1,2,3: Dimensioning, Recalculation, Pre-Dimensioning

At "File->New" or "Edit->Quick" you can select between Dimensioning, Recalculation and Pre-Dimensioning. Not-selected input fields are set invisible now.

FED1+,2+,3+,5,6,7,8,11 - Standard Wire Diameter

At wire diameter input you can select wire size from database now. Two database files offer sizes to DIN 2076 (cold-formed) and DIN 2077 (warm-formed springs). You can mark preferred sizes or stock sizes at the info field.

FED1+,2+,5,6,7 - Relaxation

Relaxation of a spring was calculated from the relaxation diagrams with the value tauk2 (dynamic load) instead of the tension tau2 (static load). This resulted in about 10% higher relaxtion value.

The newer versions also shows a warning, if operating temperature of the spring is not between Tmin and Tmax of the relaxation database.

FED2+ Calculation of Spring Length after Relaxation

The formula to calculate spring length of extension springs after relaxation was not correct in the previous infoletter, because pretension had not been considered. The correct formula is:

L0,48h = L2 - (F2,48h - F0) / R at FED2+ (tension spring)

FED2+ Life Expectation Loop

Numeric value for life cycles and lifetime in hours has been added to the Goodman Diagram for loop bending stress.

WST1 - Material Type Selection

After selecting material type, only material records of this type are displayed on the next window now.

TOL1 - True-scale Drawing

Drawing was optimized, so that description of elements is no longer written into one line.

WL1+ Notch Effect to DIN 743

According to DIN 743, notch effects do result in a reduction of permissible stress instead of higher stresses at the notch zone. WL1+ did not consider reduced permissible stress at notch zones of shaft shoulders in some cases.

A table with notch coefficients, stresses and safety coefficients at each shoulder has been added now to printout of WL1+.

WL1+ Shear Stress by Radial Load

For very short shafts, you should set option "shear stress from radial forces considered".

WL1+ adds shear stress tau=F/A at +/- d/2 (d=shaft diameter) in this case. For path loads, shear stress zone is from begin to end of path load, or +/- d/2 from load center. The calulated value for shear stress from path load q was too high at earlier versions. Shear stress from the bearing forces also has been added into the newest version of WL1+.

WL1+ Safety in Logarithmic Scale

Safety line for calculations according to DIN 743 is displayed in logarithmic scale now.

WL1+ Axial Pressure

Axial pressure (Fax < 0) is now considered for calculation of the reference stress.

Sort Database

Click into the title field with the right mouse button to sort the database. (new in all programs since Dec. 2002).

Database - New Functions

At menu "File->Save as Delimited" you can save dbf files as delimited text files. "Export HTML" generates a HTML table. "Append delimited" appends txt files in delimited format to the current database.

Help - History: Update History

Doc file with chronological description of changes can be listed and printed at "Help->History".

Line thickness for Diagrams

In the same way as for drawings, you can now change line thickness for diagrams.

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