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Z. Liu et al.
for the fatigue analysis of structures, the deterministic method is used in the current
nuclear equipment design [2, 3]. It is considered that the material properties, structural dimensions and bearing loads are all specific values, regardless of the random
fluctuations of the input, thus not taking into account the calculation error caused by
the uncertainty of the design parameters.
In order to reflect the fatigue performance of the analyzed object more realistically,
it is necessary to consider the uncertainty of the input parameters [4]. The uncertainty
quantification study of input parameters of fatigue analysis can not only analyze the
failure probability, which can guide the structural design according to the allowable
failure probability value, but also fully consider the sensitivity of each parameter to
further optimize the structural design [5–7].
In this paper, the nuclear power equipment pressurizer spray nozzle is taken as
the research object, and the uncertainty analysis of the input parameters of fatigue
analysis is carried out. The randomness is introduced into the transient fluctuation,
and the sensitivity of the transient parameters is analyzed, thus proposing advice for
structural optimization. The research results show that the uncertainty analysis of the
parameters can obtain the influence degree of each parameter on the analysis results,
which can greatly guide the structure design and optimization.
8.2 Method
8.2.1 Nuclear Power Equipment Fatigue Analysis Method
Since the structure of nuclear power equipment is mostly designed by the finite life
design method (safe life design method), the amplitude of the alternating stress is
generally higher than the yield limit of the material. Therefore, in the fatigue analysis
of nuclear power equipment, the maximum stress may not be considered only, but the
total fatigue damage should be estimated according to a certain cumulative damage
theory. The alternating load amplitude of the nuclear power equipment structure is
sometimes non-constant. If the amplitude of the alternating stress is always calculated according to the maximum amplitude, it is too conservative. An approximate
engineering treatment method is to use the linear fatigue cumulative damage theory.
The fatigue damage of the material is independent under various stresses and the
total damage can be linearly accumulated. The most representative method of these
is the PalmgrenMiner theory, and Eq. (8.1) defines Miner damage rule:
U =
n i
N i
(8.1)
Among them, n i is the cycle under the alternating stress; N i is the allowable cycle
under the alternating stress, which is determined by the S–N curve, U is the fatigue
usage. Figure 8.1 is a schematic diagram of linear accumulation of fatigue damage.
Z. Liu et al.
for the fatigue analysis of structures, the deterministic method is used in the current
nuclear equipment design [2, 3]. It is considered that the material properties, structural dimensions and bearing loads are all specific values, regardless of the random
fluctuations of the input, thus not taking into account the calculation error caused by
the uncertainty of the design parameters.
In order to reflect the fatigue performance of the analyzed object more realistically,
it is necessary to consider the uncertainty of the input parameters [4]. The uncertainty
quantification study of input parameters of fatigue analysis can not only analyze the
failure probability, which can guide the structural design according to the allowable
failure probability value, but also fully consider the sensitivity of each parameter to
further optimize the structural design [5–7].
In this paper, the nuclear power equipment pressurizer spray nozzle is taken as
the research object, and the uncertainty analysis of the input parameters of fatigue
analysis is carried out. The randomness is introduced into the transient fluctuation,
and the sensitivity of the transient parameters is analyzed, thus proposing advice for
structural optimization. The research results show that the uncertainty analysis of the
parameters can obtain the influence degree of each parameter on the analysis results,
which can greatly guide the structure design and optimization.
8.2 Method
8.2.1 Nuclear Power Equipment Fatigue Analysis Method
Since the structure of nuclear power equipment is mostly designed by the finite life
design method (safe life design method), the amplitude of the alternating stress is
generally higher than the yield limit of the material. Therefore, in the fatigue analysis
of nuclear power equipment, the maximum stress may not be considered only, but the
total fatigue damage should be estimated according to a certain cumulative damage
theory. The alternating load amplitude of the nuclear power equipment structure is
sometimes non-constant. If the amplitude of the alternating stress is always calculated according to the maximum amplitude, it is too conservative. An approximate
engineering treatment method is to use the linear fatigue cumulative damage theory.
The fatigue damage of the material is independent under various stresses and the
total damage can be linearly accumulated. The most representative method of these
is the PalmgrenMiner theory, and Eq. (8.1) defines Miner damage rule:
U =
n i
N i
(8.1)
Among them, n i is the cycle under the alternating stress; N i is the allowable cycle
under the alternating stress, which is determined by the S–N curve, U is the fatigue
usage. Figure 8.1 is a schematic diagram of linear accumulation of fatigue damage.