08-17-2017, 12:45 AM
THEORETICAL ANALYSIS FOR STUDYING THE
FRETTING WEAR PROBLEM OF STEAM GENERATOR
TUBES IN A NUCLEAR POWER PLANT
FRETTING WEAR PROBLEM OF STEAM GENERATOR
TUBES IN A NUCLEAR POWER PLANT
ABSTRACT
Fretting, which is a special type of wear, is defined as small amplitude relative motion along the contacting interface between two materials. The structural integrity of steam generators in nuclear power plants is very much dependent upon the fretting wear characteristics of Inconel 690 U-tubes. In this study, a finite element model that can simulate fretting wear on the secondary side of the steam generator was developed and used for a quantitative investigation of the fretting wear phenomenon. Finite element modeling of elastic contact wear problems was performed to demonstrate the feasibility of applying the finite element method to fretting wear problems. The elastic beam problem, with existing solutions, is treated as a numerical example. By introducing a control parameter s, which scaled up the wear constant and scaled down the cycle numbers, the algorithm was shown to greatly reduce the time required for the analysis. The work rate model was adopted in the wear model. In the three-dimensional finite element analysis, a quarterly symmetric model was used to simulate cross tubes contacting at right angles. The wear constant of Inconel 690 in the work rate model was taken as K=26.7 10-15 Pa-1 from experimental data obtained using a fretting wear test rig with a piezoelectric actuator. The analyses revealed donut-shaped wear along the contacting boundary, which is a typical feature of fretting wear.
INTRODUCTION
It is generally believed that failure accidents in industrial facilities and structures are caused by wear and/or fatigue of the loaded elements. In contrast with the numerous active, long-term studies on failures due to high-temperature fatigue, corrosive fatigue, and fretting fatigue, only a relatively small number of studies on fretting wear have been performed. Fretting, which is a special type of wear, is characterized as small amplitude oscillation along the contacting interface between two materials. Since Eden et al. first reported on this phenomenon, which was termed fretting by Tomlinson , considerable effort has been directed towards elucidating this type of behavior. Waterhouse classified the fretting phenomenon into three categories: fretting wear, fretting fatigue, and fretting corrosion. Other works - have provided some important general fretting theories or experimental results for fretting wear and/or fretting fatigue. Recently, Vingsbo and Soderberg classified fretting wear into four types: stick, mixed stick/slip, gross slip, and sliding. Ko and Fisher et al. , investigated the wear constant experimentally by studying fretting wear of tube materials for a steam generator in a nuclear power plant. In Korea, most fretting wear studies have concentrated on experimentally determining the wear constants for materials in nuclear power plants, such as Inconel or Zircalloy tubes -. Although most fretting wear studies have been carried out experimentally, some theoretical approaches have also been attempted. Mackin et al. Studied the effects of surface roughness on the wear properties of the interface between fiber and titanium-aluminum matrix composite materials. Stromberg studied a two-dimensional contact wear problem between a punch and a plate to obtain wear depth and normal contact pressure distributions using a theoretical wear formulation via an augmented Lagrangian method.
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It is generally believed that failure accidents in industrial facilities and structures are caused by wear and/or fatigue of the loaded elements. In contrast with the numerous active, long-term studies on failures due to high-temperature fatigue, corrosive fatigue, and fretting fatigue, only a relatively small number of studies on fretting wear have been performed. Fretting, which is a special type of wear, is characterized as small amplitude oscillation along the contacting interface between two materials. Since Eden et al. first reported on this phenomenon, which was termed fretting by Tomlinson , considerable effort has been directed towards elucidating this type of behavior. Waterhouse classified the fretting phenomenon into three categories: fretting wear, fretting fatigue, and fretting corrosion. Other works - have provided some important general fretting theories or experimental results for fretting wear and/or fretting fatigue. Recently, Vingsbo and Soderberg classified fretting wear into four types: stick, mixed stick/slip, gross slip, and sliding. Ko and Fisher et al. , investigated the wear constant experimentally by studying fretting wear of tube materials for a steam generator in a nuclear power plant. In Korea, most fretting wear studies have concentrated on experimentally determining the wear constants for materials in nuclear power plants, such as Inconel or Zircalloy tubes -. Although most fretting wear studies have been carried out experimentally, some theoretical approaches have also been attempted. Mackin et al. Studied the effects of surface roughness on the wear properties of the interface between fiber and titanium-aluminum matrix composite materials. Stromberg studied a two-dimensional contact wear problem between a punch and a plate to obtain wear depth and normal contact pressure distributions using a theoretical wear formulation via an augmented Lagrangian method.
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