This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influ...This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influence of the gasket geometry on its final behaviour.Such a contribution can come from the detailed modelling of the gasket or by defining a global non-linear behaviour in which material and geometry non-linearities are summarised.Two approaches were used to simulate the gasket behaviour.The first one consists in using a 2D approach,which allows to model through-thickness non-linear behaviour of gasket.The second one consists in using conventional 3D finite element modelling.The numerical methods have been discussed and compared in relation to the accordance with experimental data,amount of information supplied and computational time required.Finally,a parametric study shows how some geometric parameters influence the compressive load and the elastic recovery of a single-layer steel gasket.展开更多
The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in...The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in the gasket selection. The objective of the work presented in this paper is to develop an analytical leak rate prediction methodology used in gasketed joints. A pseudo analytical-experimental innovative approach was used to estimate the characteristics of the porous structure for the purpose of predicting accurate leak rate through gaskets with different fluids under conditions similar to those of operation. The analytical model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall to determine the porosity parameters of the gasket. The analytical model results are validated and confronted against experimental data which were conducted under various conditions of fluid media, pressure, gasket stress and temperature. Two experimental test rigs fully automate that accurately reproduces the real leakage behavior of the gasketed joint have been developed to analyze the mechanical and thermal effects on the gasket flow regime. The gas leaks were measured with multi-gas mass spectrometers while liquid leaks were measure using a sophisticated detection system based on the pressure rise method.展开更多
In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest e...In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest eigenvalue of the Neumann Laplacian(introduced by Kigami) attains its maximum and minimum on the boundary.展开更多
We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft....We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].展开更多
We present a direct and short proof of the non-degeneracy of the harmonic structures on the level-n Sierpinski gaskets for any n≥2,which was conjectured by Hino in[1,2]and confirmed to be true by Tsougkas[8]very rece...We present a direct and short proof of the non-degeneracy of the harmonic structures on the level-n Sierpinski gaskets for any n≥2,which was conjectured by Hino in[1,2]and confirmed to be true by Tsougkas[8]very recently using Tutte’s spring theorem.展开更多
The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof per...The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof performance for certain tunnels with high water pressure,especially water-conveyance tunnels.This paper presents a series of waterproofing tests on joints with different settings of double gaskets via an improved test apparatus.Four cases are investigated,including(i)double gaskets with equal high/low waterproof capacity,(ii)the outer gasket with higher waterproof capacity,and(iii)the outer gasket with lower waterproof capacity.Different joint openings are also considered.Moreover,the water pressures at two cavities are continuously monitored to highlight the waterproofing mechanism and failure pattern of double gaskets.The results demonstrate that the gasket with the higher waterproofing capacity dominates the overall waterproofing capacity of joint with double gaskets;only a little enhancement of the waterproofing capacity is found for the joint with the same double gaskets.The waterproofing capacity of joints with double gaskets decreases with the increase of the joint opening.The failure pattern depends on the arrangement of double gaskets,and four stages can be identified during the whole failure process.The advantages of double gaskets in case of joint rotation are also discussed.展开更多
The valve gasket for aero-engine is prone to creep under extreme conditions such as high temperature and high pressure.The creep failure of the gasket leads to valve leakage,which seriously threatens the safe and reli...The valve gasket for aero-engine is prone to creep under extreme conditions such as high temperature and high pressure.The creep failure of the gasket leads to valve leakage,which seriously threatens the safe and reliable operation of aero-engine.Aiming at the creep failure of FEP gasket in use,a timehardening creep model of valve gasket seal is established.The effects of time,operating pressure,material and structural parameters on the creep and sealing properties of FEP gaskets are analyzed.The results show that the compression rebound rate of gaskets decreases with the increase of time,and small compression rebound rate will decrease the sealing performance.The creep behavior of FEP gasket increases with the increase of operating pressure.Reducing the fillet radius can reduce the probability of shear failure,but also reduce the contact stress.Increasing the height of the boss can reduce the deformation behavior of the gasket,but reduce the contact stress on the sealing surface.When the gasket bevel angle is 85°,the creep property and contact stress of the gasket are higher than those of other sizes.But large bevel angle leads to the gasket unsticking.Replacing the FEP material with the polyimide material can improve the creep resistance of gaskets and the contact stress of sealing surface.Considering the service life and sealing effect of gasket,the material is replaced with polyimide plastic,the fillet radius is 0.20mm,the bevel angle is 85°and the boss height is 0.2mm.展开更多
A general formulation for the spectral calculations of the Hamiltonian operator of a Quantum Fractal Network (QFN) is presented. The QFN can be constructed by placing artificial neurons on each site of the fractal lat...A general formulation for the spectral calculations of the Hamiltonian operator of a Quantum Fractal Network (QFN) is presented. The QFN can be constructed by placing artificial neurons on each site of the fractal lattice. An artificial neuron may consist of a cell of a quantum cellular automaton or a quantum dot, which confines a single electron. The Coulomb interaction or the spin-spin interaction between neurons can be used to transmit signals and perform logic operations. The recursive formulas of the eigenvalues and eigenvectors between sub-lattices are obtained explicitly. As the application of the formulations, the eigenvalues and eigenvectors of the Hamiltonian operator for the Sierpinskii gasket are calculated.展开更多
In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpin...In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpinski gasket S can be approximated by {Pn(S)} with Pn(S)/(l + l/2n-3)s≤Hs(S)≤ Pn(S). An algorithm is presented to get Pn(S) for n ≤5. As an application, we obtain the best lower bound of Hs(S) till now: Hs(S)≥0.5631.展开更多
Abstract. In this paper, we first characterize the finiteness of fractal interpolation functions （FIFs） on post critical finite self-similar sets. Then we study the Laplacian of FIFs with uniform vertical scaling fa...Abstract. In this paper, we first characterize the finiteness of fractal interpolation functions （FIFs） on post critical finite self-similar sets. Then we study the Laplacian of FIFs with uniform vertical scaling factors on the Sierpinski gasket （SG）. As an application, we prove that the solution of the following Dirichlet problem on SG is a FIF with uniform vertical scaling factor 1/5 ：△=0 on SG ／ {q1, q2, q3}, and u（qi）=ai, i = 1, 2, 3, where qi, i=1, 2, 3, are boundary points of SG.展开更多
A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylen...A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylene terepthalate( PET) multifilament bought from market. The physical properties of the gasket were evaluated comprehensively and biocompatibility was analyzed with MTT assay.展开更多
文摘This paper is focused on finite element simulation of cylinder head gaskets.Finite element codes support several methodologies,each of which has its own strengths and weaknesses.One of the key points lies in the influence of the gasket geometry on its final behaviour.Such a contribution can come from the detailed modelling of the gasket or by defining a global non-linear behaviour in which material and geometry non-linearities are summarised.Two approaches were used to simulate the gasket behaviour.The first one consists in using a 2D approach,which allows to model through-thickness non-linear behaviour of gasket.The second one consists in using conventional 3D finite element modelling.The numerical methods have been discussed and compared in relation to the accordance with experimental data,amount of information supplied and computational time required.Finally,a parametric study shows how some geometric parameters influence the compressive load and the elastic recovery of a single-layer steel gasket.
文摘The reliability of industrial installation requires minimum leakage of pressurized sealed joints during operation. At the design stage, the leakage behavior of the gasket must be one of the most important parameter in the gasket selection. The objective of the work presented in this paper is to develop an analytical leak rate prediction methodology used in gasketed joints. A pseudo analytical-experimental innovative approach was used to estimate the characteristics of the porous structure for the purpose of predicting accurate leak rate through gaskets with different fluids under conditions similar to those of operation. The analytical model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall to determine the porosity parameters of the gasket. The analytical model results are validated and confronted against experimental data which were conducted under various conditions of fluid media, pressure, gasket stress and temperature. Two experimental test rigs fully automate that accurately reproduces the real leakage behavior of the gasketed joint have been developed to analyze the mechanical and thermal effects on the gasket flow regime. The gas leaks were measured with multi-gas mass spectrometers while liquid leaks were measure using a sophisticated detection system based on the pressure rise method.
基金supported in part by NSFC grants Nos.11271327, 11771391
文摘In this paper, using spectral decimation, we prove that the "hot spots" conjecture holds on a class of homogeneous hierarchical gaskets introduced by Hambly,i.e., every eigenfunction of the second-smallest eigenvalue of the Neumann Laplacian(introduced by Kigami) attains its maximum and minimum on the boundary.
文摘We have previously evaluated asbestos exposure associated with various maintenance procedures on light aircraft. The purpose of this study was to evaluate asbestos exposure during engine maintenance on light aircraft. This test was designed to evaluate the potential for asbestos exposure to mechanics and others who remove asbestos-containing engine gaskets from reciprocating style aircraft engines. Utilized in this test was an air cooled, horizontally opposed, aviation gasoline burning engine, assembled during 1986 and operated intermittently up into 2015, having accumulated 1680 hours run time. Nearly 75% of the asbestos-containing gaskets installed during 1986 were still in place at the time of testing. Chrysotile asbestos contents of such gaskets ranged from 55% to 60% by area, for those of sheet style and 5% by area, for the spiral wound metal/asbestos style. Despite the levels of effort required to effect gasket removals, the professional aircraft mechanic was not exposed to airborne asbestos fibers at the lower limits of sampling and analytical detection achieved;all of which were substantially less than the current Occupational Safety and Health Administration Permissible Exposure Limits for asbestos. The results of this testing indicate an absence of gasket related asbestos exposure risk to mechanics who work with light aircraft engines, including those having asbestos-containing gaskets. These results are consistent with the findings of Mlyarek and Van Orden who studied the asbestos exposure risk occasioned during overhaul of larger radial style reciprocating aircraft engines [1].
基金the Nature Science Foundation of China,Grant No.12071213.
文摘We present a direct and short proof of the non-degeneracy of the harmonic structures on the level-n Sierpinski gaskets for any n≥2,which was conjectured by Hino in[1,2]and confirmed to be true by Tsougkas[8]very recently using Tutte’s spring theorem.
基金financially supported by National Natural Science Foundation of China(52090083)Shanghai Committee of Science and Technology(20DZ1202600)China Railway Southern Investment Group Co.Ltd(Project No.ZTNF-2020-1).
文摘The waterproofing capacity of segmental joints is an essential indicator for the long-term service performance of shield tunnels.The segmental joints with double gaskets have been adopted to improve the waterproof performance for certain tunnels with high water pressure,especially water-conveyance tunnels.This paper presents a series of waterproofing tests on joints with different settings of double gaskets via an improved test apparatus.Four cases are investigated,including(i)double gaskets with equal high/low waterproof capacity,(ii)the outer gasket with higher waterproof capacity,and(iii)the outer gasket with lower waterproof capacity.Different joint openings are also considered.Moreover,the water pressures at two cavities are continuously monitored to highlight the waterproofing mechanism and failure pattern of double gaskets.The results demonstrate that the gasket with the higher waterproofing capacity dominates the overall waterproofing capacity of joint with double gaskets;only a little enhancement of the waterproofing capacity is found for the joint with the same double gaskets.The waterproofing capacity of joints with double gaskets decreases with the increase of the joint opening.The failure pattern depends on the arrangement of double gaskets,and four stages can be identified during the whole failure process.The advantages of double gaskets in case of joint rotation are also discussed.
基金National Key Research and Development Program of China(2018YFB200800)。
文摘The valve gasket for aero-engine is prone to creep under extreme conditions such as high temperature and high pressure.The creep failure of the gasket leads to valve leakage,which seriously threatens the safe and reliable operation of aero-engine.Aiming at the creep failure of FEP gasket in use,a timehardening creep model of valve gasket seal is established.The effects of time,operating pressure,material and structural parameters on the creep and sealing properties of FEP gaskets are analyzed.The results show that the compression rebound rate of gaskets decreases with the increase of time,and small compression rebound rate will decrease the sealing performance.The creep behavior of FEP gasket increases with the increase of operating pressure.Reducing the fillet radius can reduce the probability of shear failure,but also reduce the contact stress.Increasing the height of the boss can reduce the deformation behavior of the gasket,but reduce the contact stress on the sealing surface.When the gasket bevel angle is 85°,the creep property and contact stress of the gasket are higher than those of other sizes.But large bevel angle leads to the gasket unsticking.Replacing the FEP material with the polyimide material can improve the creep resistance of gaskets and the contact stress of sealing surface.Considering the service life and sealing effect of gasket,the material is replaced with polyimide plastic,the fillet radius is 0.20mm,the bevel angle is 85°and the boss height is 0.2mm.
基金Supported by the National Natural Foundation of China (79970121).
文摘A general formulation for the spectral calculations of the Hamiltonian operator of a Quantum Fractal Network (QFN) is presented. The QFN can be constructed by placing artificial neurons on each site of the fractal lattice. An artificial neuron may consist of a cell of a quantum cellular automaton or a quantum dot, which confines a single electron. The Coulomb interaction or the spin-spin interaction between neurons can be used to transmit signals and perform logic operations. The recursive formulas of the eigenvalues and eigenvectors between sub-lattices are obtained explicitly. As the application of the formulations, the eigenvalues and eigenvectors of the Hamiltonian operator for the Sierpinskii gasket are calculated.
文摘In this paper, we firstly define a decreasing sequence {Pn(S)} by the generation of the Sierpinski gasket where each Pn(S) can be obtained in finite steps. Then we prove that the Hausdorff measure Hs(S) of the Sierpinski gasket S can be approximated by {Pn(S)} with Pn(S)/(l + l/2n-3)s≤Hs(S)≤ Pn(S). An algorithm is presented to get Pn(S) for n ≤5. As an application, we obtain the best lower bound of Hs(S) till now: Hs(S)≥0.5631.
基金Supported by the National Natural Science Foundation of China(11271327)Zhejiang Provincial National Science Foundation of China(LR14A010001)
文摘Abstract. In this paper, we first characterize the finiteness of fractal interpolation functions （FIFs） on post critical finite self-similar sets. Then we study the Laplacian of FIFs with uniform vertical scaling factors on the Sierpinski gasket （SG）. As an application, we prove that the solution of the following Dirichlet problem on SG is a FIF with uniform vertical scaling factor 1/5 ：△=0 on SG ／ {q1, q2, q3}, and u（qi）=ai, i = 1, 2, 3, where qi, i=1, 2, 3, are boundary points of SG.
文摘A series of cranial nerve decompression gaskets were prepared with fibers of different fineness and high crimp which were obtained in knit-de-knit texturing process by using different specification general polyethylene terepthalate( PET) multifilament bought from market. The physical properties of the gasket were evaluated comprehensively and biocompatibility was analyzed with MTT assay.
