Temperature effect

The thermal load effect can be switched on for the LESA method. See first, which temperatures are expected to be normal according to the FKM [FKM03]:

Definition of normal temperatures for different kinds of materials
class of material	minimum temperature [°C]	maximum temperature [°C]
fine grain structural steel	-40	60
other kinds of steel	-40	100
cast iron materials	-25	100
age-hardening aluminum alloys	-25	50
non-age-hardening aluminum alloys	-25	100

The thermal load has to be defined so that it could influence the fatigue calculation.

The solution is described in [FKM03], here only its transcription is done. The thermal influence factor FT modifies the actual fatigue strength:

Different formulas are used for the determination of the factor FT:. Their overview together with the necessary thermal influence coefficient can be found in the following table. The symbol T corresponds to the temperature in degree of Celsius there.

Definition of normal temperatures for different kinds of materials
class of material	formula type	thermal influence coefficient aT	maximum temperature [°C]
fine grain structural steel		1	500
cast steels		1.2	500
other kinds of steel		1.4	500
nodular cast iron		1.6	500
malleable cast iron		1.3	500
gray cast iron		1.0	500
aluminum alloys		1.2	200

The solution adopted here utilizes the proposal defined in [SMB03]. The FT coefficient is related there to a decrease/increase of static tensile strength due increased temperature. Mischke proposes use of a conversion formula in the same book for derivation of the rotating bending fatigue limit br from tensile strength Su:

Because of Mischke expects this dependency to be true, he does not hesitate to convert also the fatigue limit by the same coefficient FT. The values of the coefficient are given in the table below for two kinds of degree scales. Mischke proposes a fourth-order polynom for definition over the whole space, but he uses the dependency on the degree of Fahrenheit. The second formula below was thus derived by me (Jan Papuga, author) in order to allow the use of the Celsius degree scale:

The second formula is used in PragTic, the temperature input related to thermal loads thus should correspond to Celsius scale temperature.

Temperature [°F]	FT	Temperature [°C]	FT
70	1.000	20	1.000
100	1.008	50	1.010
200	1.020	100	1.020
300	1.024	150	1.025
400	1.018	200	1.020
500	0.995	250	1.000
600	0.963	300	0.975
700	0.927	350	0.943
800	0.872	400	0.900
900	0.797	450	0.843
1000	0.698	500	0.768
1100	0.567	550	0.672
		600	0.549