Abstract
Shape memory alloy corrugated gaskets (SMA-CGs) can adapt to fluctuating working conditions due to their pseudoelasticity (PE) and shape memory effect (SME), which make them excellent sealing components. In this study, the deformation mechanism of SMA-CGs was examined according to their structural properties under installation and operating conditions to establish an SMA-CG thermal-mechanical coupling model with the finite element analysis (FEA) method, which has been verified through experimentation. Based on this, a thermal-mechanical coupling FEA model was built for a bolted flange joint with SMA-CG. The influence of the SMA-CG structure parameters on compression-rebound mechanical properties was also studied under installation and operating conditions. The conclusions are as follows: a thermal-mechanical coupling finite element analysis method was established for NiTi alloy corrugated structures. Through comparison with the experimental results, the maximum error of the maximum compression load was 5.78%, the maximum error of the rebound rate was 8.85%, and the maximum error of the maximum compaction force in the heat recovery stage was 12.2%, all of which were within the <15% acceptable error range of engineering fields. According to the related experiments and finite element results, the maximum compressive force of gasket thermal recovery after unloading was not less than 40% of the initial maximum compressive load. The application of shape memory alloy to corrugated gasket significantly improved its ability in coping with fluctuating load temperatures. The contact pressure of corrugation increased with the increase of sheet thickness (T) and corrugated gasket height (H) under installation and operating conditions, showing a decreasing trend with the increase of pitch (P), of which the order of factors influencing the average contact pressure of corrugated gasket was sheet T > H > P, and when structural parameters of SMA-CG were T = 0.6 mm, H = 4 mm, and P = 2.5 mm, the contact pressure of corrugated gasket was the highest under operating conditions.
Highlights
As an important detachable connection method for processing industries, bolted flange connections have been widely used in the fields of chemical industry, nuclear energy, aerospace, and so on
E main errors in this study were experimental errors caused by mechanical performance testing machine and errors between material parameters of finite element simulation and real material parameters of experimental corrugated samples. ese particular variations are acceptable in both engineering fields and theoretical models. erefore, the constitutive model and finite element analysis (FEA) method proposed in this paper are reasonable, which can be applied in the analysis of mechanical properties of bolted flange Shape memory alloy (SMA)-CGs
In the bolted flange connection system, the upper and lower flanges and bolts are made of a linear elastic material. 42CrMo was used. e gasket material was SMA, and its material parameters are shown in Table 2. e penalty function contact attributes were adopted between each contact surface, with the friction coefficient of 0.15. e lower end of lower flange nozzle was set as a fixed support, the two sides of flange were set as axisymmetric restraints, and the upper end of upper flange was ø190 ø149.2 ø76.1
Summary
As an important detachable connection method for processing industries, bolted flange connections have been widely used in the fields of chemical industry, nuclear energy, aerospace, and so on. Advances in Materials Science and Engineering gaskets at room and variable temperatures through experimentation and finite element methods, with the results showing that the SMA flat gasket possesses good sealing performance under both installation and operation conditions. Combining its SME and PE with corrugated gaskets can effectively reduce the pretightening force of advanced equipment connection joints and improve the reliability of joint sealing under fluctuating conditions. Scholars used the thermalmechanical coupling finite element method to study the contact stress distribution of shape memory alloy flat gaskets in a bolted flange connection system under a uniform temperature field, only referring to the general metal gasket modeling method [4]. The phase change behavior of SMA-CGs is nonuniform compared with flat gaskets In this case, the gasket element is not suitable for the simulation of shape memory alloys. It is hoped that the findings of this study can lay a foundation for further engineering applications of SMA-CGs
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