Modelling Strategy and Parametric Study of Metal Gaskets for Automotive Applications

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.

THE BOUNDEDNESS OF BILINEAR SINGULAR INTEGRAL OPERATORS ON SIERPINSKI GASKETS

In the paper we give the boundedness estimate of bilinear singular integral operators on Sierpinski gasket inspired from [ 1 ].

Prediction of Leakage Rates Through Sealing Connections with Nonmetallic Gaskets

In this work, a model of gas leakage through nonmetallic gaskets was developed in order to predict leakage rate of gasket sealing connections. The model was verified by the leakage experiments on two types of gaskets： compressed non-asbestos fiber gasket and flexible graphite gasket reinforced with tanged metal sheet. The coefficients in the leakage rate formula were obtained by regression of experimental data for each type of gasket, The model was also validated against the experimental leakage data by other researchers and shown to produce accurate predications. Furthermore, the model was applied to a bolted flanged connection in service in order to assess the tightness of the connection.

Analytical and Experimental Studies of Liquid and Gas Leaks through Micro and Nano-Porous Gaskets

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.

The ”Hot Spots” Conjecture on Homogeneous Hierarchical Gaskets

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.

Asbestos Exposure during Gasket Removal from Aircraft Engine

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].

The Non-Degeneracy of Harmonic Structures on Planar Sierpinski Gaskets

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.

Experimental investigation on waterproofing performance of segmental joint with double gaskets for shield tunnel

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.

考虑蠕变特性的航空发动机阀门用非金属垫片的密封性能研究

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.

基于Abaqus垫片密封接触有限元分析

以一个端盖密封为例,借助Abaqus有限元分析软件,使用Gasket单元,分析了材料非线性垫片在不同螺栓扭矩螺栓预紧情况下的的受压与剪切的应力分布,并结合理论分析对垫片进行校核。

Sierpiński Gasket图的星着色

研究了Sierpiński gasket图Sn的星着色,证明了在同构意义下S3是唯一的4-星可着色的,且给出了Sierpiński gasket图Sn的星色数的精确值为χs(Sn)=5(n≥4).

Sierpiński Gasket图的2-距离着色

运用群论中置换的思想,通过置换顶点的着色法,研究Sierpiński gasket图Sn的2-距离着色,且给出了Sierpiński gasket图Sn的2-距离色数的精确值为χ(Sn)=6,其中n≥2.

考虑非线性因素的燃烧室密封特性分析

以某V型高强化柴油机为研究对象，考虑气缸垫中基材的弹塑性变形特性、密封橡胶的超弹性特性及燃烧室各部件间的接触非线性因素，建立了燃烧室气缸垫密封特性有限元分析模型。借助有限元非线性求解方法，计算气缸垫密封凸纹和橡胶密封圈表面的接触压力，以此评价发动机动力强化后燃烧室的密封效果，同时探讨了气缸盖螺栓顸紧力与燃烧室密封特性的关联性，确定发动机动力强化后缸盖螺栓预紧力的优选范围。分析结果表明：强化后热一机耦合工况下，气缸垫密封凸纹上最小接触压力比强化前下降了13％，燃烧室密封效果降低；将缸盖螺栓预紧力控制在88～92kN范围内，可使燃烧室的密封性能达到强化前状态。

SPECTRAL CALCULATIONS OF HAMILTONIAN FOR A QUANTUM FRACTAL NETWORK

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.

基于OpenGL的Sierpinski镂垫程序探讨

介绍了OpenGL的基本概念、功能和工作方式,并在OpenGL基础上实现一个有趣的Sierpinski gasket镂垫图案。在镂垫实现过程中阐述了两种方式,一种生成点,另一种生成多边形。通过镂垫的实现进一步体现OpenGL强大的功能。

Sierpiński图与Sierpińskigasket图的条件着色

对Sierpiński图与Sierpiński gasket图的条件着色进行研究,分别给出其条件色数.对于Sierpiński gasket图,当n≥2时,χ1(Sn)=χ2(Sn)=3,χ3(Sn)=4,若r≥4,则χr(Sn)=6.对于Sierpiński图,当n≥2时,若1≤r≤k-1,则χr(S(n,k))=k;若r≥k,则χr(S(n,k))=k+1.

Frictional heat analysis of mine hoist and numerical simulation on temperature field of gasket

The frictional performance of gaskets is greatly affected by frictional heat in operational mine hoists. Based on frictional mechanism and heat transfer theory, the mathematical model of the temperature field of the PVC gasket in an operational mine hoist was investigated, a numerical simulation using ANSYS is presented and the distribution of the temperature and heat flux were studied under basic assumptions. The results show that the temperature gradually decreases as the radius of the model increases and the isotherms are arcs of concentric semi-circle. The heat flux is of bilateral symmetry in the model and decreases radially. The theoretical values correspond with the measured values for a short time (τ≤ 100 s) when the steel wire rope slides.

Stress relaxation behavior and life prediction of gasket materials used in proton exchange membrane fuel cells

Silicone rubber gaskets are employed to keep fuel gases and oxidation in their own zones. Due to the viscosity and elasticity, the assembly force could relax when the silicone rubber is compressed in a proton exchange membrane fuel cell. In this work, the stress relaxation behavior of silicone rubber samples is studied under different temperatures and simulated operating conditions. The results show that the stress relaxes exponentially with time at 25% strain level, especially at higher temperature or with higher acid concentration solution. The three-term Prony series can simulate the viscoelastic behavior well, and the Master curves are established by applying a time–temperature superposition method to estimate the life of the samples. It can save approximately 50% and 78% of the test time when an operating temperature and acid solution are chosen appropriately.

AN APPROXIMATION METHOD TO ESTIMATE THE HAUSDORFF MEASURE OF THE SIERPINSKI GASKET

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.

无石棉垫片压缩回弹性能分析及密封设计改进

首先介绍了GASKET单元的模型属性,然后测试了无石棉垫片的压缩回弹曲线,模拟了垫片的加载和卸载过程,最后分析压缩回弹特性曲线参数对密封性能的影响规律。结合垫片密封性能仿真和面压试验,分析了发动机液压泵盖板密封漏油问题,通过更换Q235-A材料、密封面厚度增加至13 mm来提高法兰面刚度,最终解决了漏油问题。