.Technology effect
The technology effect can be switched on for the LESA method. There are 2 basic options how to cope with the temperature effect in the Calculation Methods menu:
* No - the technology effect is not applied at all
* FemFat
The FemFat method is based on data given in [FKM03], where proposals on the technology influence factor are summed. A similar table is also provided in the Theory manual of FemFat [ECS4.4]. The user has the 3rd option how to input this factor - it can be set in the Properties of Structure dialogue. If it is stated there with a designation, to which technology operation it is related, than this value replaces any result of the FemFat formulas given in the text below.
Note, please, that whenever the FemFat option is chosen in the Influence of Technology list, a set of several new options is created in the Solution options of the method. These are:
* shot-peen
* rolling
* case-hardening
* nitration
* induction-hardening
* flame-hardening
Only after the chosen technology is set to be active, the technology influence is applied to the fatigue calculation.
Example:
You want to define the component as being nitrated on some part of the surface. Then:
1) Create an adequate property in the Properties of Structure dialogue. Choose the nitration as the Chosen technology there. If you have a more relevant data concerning its impact on the fatigue limit, add the technology factor FC in its numerical value to the edit box on the right (below User defined influence factors).
2) Apply the created property to an appropriate element/isolated point set.
3) Set the Influence of Technology parameter in the Calculation Methods menu to the option FemFat.
4) Switch the option Apply influence factor of nitration <1~yes, 0~no> to 1.
The recommended values of the technology factor FC according to [FKM03] are summed in the table below with a dependency on the diameter D of the specimens.
|
Surface treatment |
unnotched components |
notched components |
||
|
D = 8-15 mm |
D = 30-40 mm |
D = 8-15 mm |
D = 30-40 mm |
|
|
Steels |
||||
|
Nitriding (depth of case 0.1-0.4mm, 700-1000 HV10 on the surface) |
1.15-1.25 |
1.10-1.15 |
1.90-3.00 |
1.30-2.00 |
|
Case-hardening (depth of case 0.2-0.8mm, 670-750 HV10 on the surface) |
1.20-2.00 |
1.10-1.50 |
1.50-2.50 |
1.20-2.00 |
|
Carbo-nitriding (depth of case 0.2-0.8mm, 670-750 HV10 on the surface) |
1.80 |
|||
|
Cold-rolling |
1.20-1.40* |
1.10-1.25 |
1.50-2.20* |
1.30-1.80 |
|
Shot-peening |
1.10-1.30* |
1.10-1.20 |
1.40-2.50* |
1.10-1.50 |
|
Inductive hardening, flame hardening (depth of case 0.9-1.5mm, 51-64 HRC on the surface) |
1.30-1.60* |
1.20-1.50 |
1.60-2.80* |
1.50-2.50 |
|
Cast irons (not reprinted in [ECS4.4]) |
||||
|
Nitriding |
1.15 |
1.10 |
1.90 |
1.30 |
|
Case-hardening |
1.20 |
1.10 |
1.50 |
1.20 |
|
Cold-rolling |
1.20 |
1.10 |
1.50 |
1.30 |
|
Shot-peening |
1.10 |
1.10 |
1.40 |
1.10 |
|
Inductive hardening, flame-hardening |
1.30 |
1.20 |
1.60 |
1.50 |
* [ECS4.4] cites the same values as being related to specimens with diameter D = 7-20 mm.
The solution is described in [FKM03], here only its transcription is done. If no other influence is active, the technology factor FC modifies the actual fatigue limit:
.
The general formula common to the most of the technologies is:
,
where the z parameter is dependant on the characteristic dimension deq [mm] in the examined place:
.
The last missing variable is the relative stress gradient 
. The resting five parameters are related to the technology applied and are defined in the table below.
|
Surface treatment |
a1 |
b1 |
a2 |
b2 |
c |
|
nitriding (on normal state) |
1.16 |
0.0525 |
0.89 |
0.4725 |
1.2 |
|
nitriding (on hardened and tempered state) |
1.16 |
0.0525 |
0.89 |
0.4725 |
1.0 |
|
rolling |
1.24 |
0.0788 |
0.46 |
0.1182 |
1.0 |
|
shot-peening |
1.17 |
0.0263 |
0.43 |
0.3677 |
1.0 |
No other relation is reported in [FKM03]. The lower (conservative) bounds are therefore used for the other technologies:
* case-hardening FC = 1.1;
* inductive hardening or flame-hardening FC = 1.2.
© PragTic, 2007
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