本文選題：密封圈 + 失效�。� 參考：《天津理工大學(xué)》2012年碩士論文

【摘要】：密封圈是液壓系統(tǒng)防止泄漏，提高容積效率，保證系統(tǒng)正常工作的重要元件，現(xiàn)代液壓控制技術(shù)對密封提出了更高的要求。本文分析了密封圈在工作中失效的原因及形式；采用有限元方法建立了不同截面形狀的密封圈的仿真模型，對其密封性能進行模擬，分析中考慮了幾何非線性、材料非線性、狀態(tài)非線性；研究了影響密封圈密封性能的因素，提出了結(jié)構(gòu)優(yōu)化方案；對液壓密封圈溫度場和熱應(yīng)力耦合場進行分析，探討了生熱對密封性能的影響。研究內(nèi)容和所得結(jié)論如下： 1、Yx形密封圈有限元分析。 應(yīng)用超彈性理論和非線性理論，對Yx形液壓密封圈的性能進行模擬，分析了其失效的位置和模式，研究了參數(shù)對密封性能的影響，提出了結(jié)構(gòu)優(yōu)化模型。 研究表明：最大應(yīng)力出現(xiàn)在上下唇交匯處；變形最大區(qū)域發(fā)生在Yx形開口靠近內(nèi)唇處；根部有較大的接觸壓力，根據(jù)失效準(zhǔn)則，這兩處容易發(fā)生失效。壓力增大時，剪應(yīng)力明顯增加；最大接觸壓力隨介質(zhì)壓力呈線性增長。最大變形隨初始壓縮率的增加而線性增大，最大剪應(yīng)力在壓縮率為20%時達到最大。槽口圓角半徑對Yx形密封圈密封性能的影響很小。摩擦系數(shù)增大時，最大剪切應(yīng)力明顯增加，但最大變形和最大接觸壓力都有減小的趨勢。由此提出結(jié)構(gòu)優(yōu)化方案，并對其進行分析，結(jié)果表明接觸寬度明顯減小，根部磨損得到改善，摩擦減小，可以提高密封圈的使用壽命。 2、O形密封圈仿真分析。 分析表明：O形密封圈根部、密封圈和活塞接觸部位附近變形較大，最大Mises應(yīng)力發(fā)生在根部。介質(zhì)壓力增加時，密封圈最大變形和等效應(yīng)力明顯增大，接觸應(yīng)力線性增加；初始壓縮率增大時變形、剪切應(yīng)力、Mises應(yīng)力、最大接觸應(yīng)力隨之增加；摩擦系數(shù)增大使接觸應(yīng)力和Mises應(yīng)力增大。因此應(yīng)選擇合適的壓縮率，為防止壓力增大時根部發(fā)生間隙咬傷，加入擋圈，以避免密封槽口處出現(xiàn)應(yīng)力集中，提高密封圈使用壽命。 3、對O形和Yx形密封圈溫度場進行分析。 應(yīng)用傳熱學(xué)原理，分析了橡膠密封圈摩擦生熱和機械滯后生熱的機理，對密封圈溫度場進行分析。由于橡膠材料的導(dǎo)熱性差，密封圈在工作過程中溫升的熱源有兩個：摩擦生熱和機械滯后生熱。摩擦生熱主要使密封圈與活塞桿接觸部分溫度升高，，機械滯后生熱使密封圈中心部分溫度較高，其溫升明顯高于摩擦引起的溫升；兩種熱源下，密封圈具有很高的溫度場；油壓、相對滑動速度以及油溫的增大，均使密封圈溫升明顯增加。因此限制工作壓力和相對滑動速度以及較好散熱條件，提高密封性能和使用壽命有利。 4、對密封圈的溫度-結(jié)構(gòu)進行耦合分析。溫度升高時，橡膠硬度下降，密封圈最大剪切應(yīng)力和接觸應(yīng)力相應(yīng)減小，而最大等效Mises應(yīng)力明顯減小。同時由于高溫容易發(fā)生氧化現(xiàn)象，使材料老化加速，導(dǎo)致橡膠材料的硬度、超彈特性、抵抗張力的強度明顯減弱，且容易發(fā)生永久變形。因此應(yīng)保證密封圈在一定溫度范圍內(nèi)工作。
[Abstract]:The seal ring is an important component of the hydraulic system to prevent leakage , improve the volumetric efficiency and ensure the normal operation of the system .
The simulation model of the seal ring with different cross - section shapes is established by the finite element method . The sealing performance is simulated . The geometric nonlinearity , material nonlinearity and state nonlinearity are considered in the analysis .
The factors influencing the sealing performance of sealing ring are studied , and the structure optimization scheme is put forward .
The temperature field and thermal stress coupling field of the hydraulic seal ring are analyzed , and the influence of heat generation on the sealing performance is discussed . The results are as follows :

1 . Finite element analysis of Yx - shaped sealing ring .

The performance of Yx - shaped hydraulic seal ring is simulated by using super elastic theory and nonlinear theory , the position and mode of its failure are analyzed , the influence of parameters on the sealing performance is studied , and the structural optimization model is proposed .

The results show that the maximum stress appears at the intersection of upper and lower lip ;
the deformation maximum area occurs near the inner lip of the Yx - shaped opening ;
There is a large contact pressure at the root , according to the failure criterion , the two parts are prone to failure . When the pressure increases , the shear stress increases obviously ;
The maximum shear stress increases linearly with the increase of the initial compression ratio . The maximum shear stress reaches the maximum when the compression ratio is 20 % . When the friction coefficient increases , the maximum shear stress increases obviously , but the maximum deformation and the maximum contact pressure decrease . The results show that the contact width is obviously reduced , the root wear is improved , the friction is reduced , and the service life of the sealing ring can be prolonged .

2 . Simulation analysis of O - ring seal ring .

The results show that the deformation of the root of O - ring seal ring , the sealing ring and the contact area of the piston is large , and the maximum von stress occurs at the root . When the medium pressure increases , the maximum deformation and the equal effect force of the sealing ring are obviously increased , and the contact stress increases linearly ;
When the initial compression rate is increased , the deformation , shear stress , von mises stress and the maximum contact stress are increased .
Therefore , the proper compression ratio should be selected to prevent the gap between the root and the retaining ring when the pressure is increased , so as to avoid the stress concentration at the sealing notch and prolong the service life of the sealing ring .

3 . The temperature field of O - shaped and Yx - shaped sealing rings is analyzed .

Based on the principle of heat transfer , the mechanism of friction heat generation and mechanical hysteresis heat generation of rubber seal ring is analyzed . The temperature field of sealing ring is analyzed . Due to poor thermal conductivity of rubber material , there are two heat sources of temperature rise in the sealing ring during operation : frictional heat generation and mechanical hysteresis heat generation . The friction heat generation mainly causes the temperature of the sealing ring and piston rod to rise , the temperature of the central part of the sealing ring is higher than the temperature rise caused by friction .
Under the two heat sources , the sealing ring has a very high temperature field ;
The oil pressure , relative sliding speed and the increase of oil temperature increase the temperature rise of the sealing ring , thus limiting the working pressure and relative sliding speed and better heat dissipation conditions , and improving the sealing performance and the service life .

4 . When the temperature is raised , the rubber hardness decreases , the maximum shear stress and the contact stress of the sealing ring decrease correspondingly , while the maximum equivalent von stress is obviously reduced . At the same time , because of the easy oxidation phenomenon at high temperature , the material aging is accelerated , the strength of the rubber material is obviously weakened , and the permanent deformation is easy to occur . Therefore , the sealing ring should be ensured to work within a certain temperature range .

【學(xué)位授予單位】：天津理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TH136

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