环缠绕钢内胆复合气瓶轴向破裂原因分析

为了研究环缠绕钢内胆复合气瓶(CNG-Ⅱ)轴向破裂原因,对实际CNG-Ⅱ气瓶水压爆破试验中出现轴向破裂的气瓶进行有限元分析。对比水压爆破试验结果和有限元分析结果,验证有限元建模的准确性。在此基础上,对受试气瓶进行应力分析,研究气瓶内胆和缠绕层的应力分布,得出气瓶在爆破压力下,内胆筒体段轴向应力大于环向应力,产生超压破坏,发生轴向破裂。     

复合材料缠绕层缺陷深度对CNG-2气瓶强度影响的研究

通过创建一种特殊的模型路径叠加分析方法,利用有限元技术,研究和探讨了具有给定缺陷长度和不同缺陷深度的CNG-2气瓶的应力状态改变及状态叠加方法.通过重点研究不同缺陷深度对CNG-2气瓶内胆强度的影响,发现缠绕层缺陷深度变化对于缺陷局部附近的气瓶内胆强度和使用安全性有重要影响,而远离缺陷部位的内胆简体的性能几乎不受缠绕层缺陷深度的影响.     

环缠绕钢内胆气瓶爆破失效分析

为了研究环缠绕钢内胆气瓶(CNG-Ⅱ气瓶)爆破失效原因,对制造过程中爆破失效的钢内胆气瓶断口、材料化学成分、力学性能、内外表面无损检测和金相组织进行试验研究和分析,对钢管热轧、热扩和冷拔工艺进行分析。结果表明,环缠绕钢内胆气瓶爆破失效的原因为:钢管终轧温度高、冷却速度慢导致化学成分偏析的钢管出现网状碳化物;热扩推挤速度快造成钢管加热时间不足,使钢管在低于工艺要求温度下热扩,导致存在网状碳化物的钢管开裂,形成孔洞和裂纹,冷拔加速材料内部孔洞和裂纹扩展;气瓶在水压试验或水压爆破试验中因材料中的孔洞或裂纹快速扩展出现爆破失效。     

缠绕层表面缺陷对CNG-2复合气瓶爆破压力的影响

为了研究复合材料层表面缺陷对于CNG-2复合气瓶爆破压力的影响,通过考察实际的表面缺陷形状,将复合层表面缺陷简化为一定尺寸的矩形槽。对带有2 mm深度矩形槽型缺陷的复合气瓶进行爆破试验,并利用有限元数值计算软件ANSYS计算其爆破压力,以分析2 mm深矩形槽型缺陷对气瓶爆破压力产生的影响及其原因。结果表明,矩形槽型表面缺陷对于气瓶内衬应力的影响并不明显,而对缠绕层应力影响较大,缠绕层矩形槽型缺陷底面的应力超过复合材料抗拉强度保证值,使得复合气瓶爆破压力减小。     

缠绕张力对环缠绕复合材料气瓶应力的影响

提出了一种等效降温法,将缠绕张力产生的预应力等效模拟为复合材料层降温产生的预应力,通过理论推导得到了缠绕预应力与复合材料层降温量之间的计算公式,基于等效降温法并利用通用有限元软件研究了缠绕张力对环缠绕复合材料气瓶应力的影响。结果表明：随着缠绕预应力的增大,环缠绕复合材料气瓶内胆工作应力减小、复合材料层工作应力增大;缠绕张力预应力较大时会抵消自紧工艺效果,气瓶工作应力和纤维应力比主要受缠绕张力影响,在进行有限元应力分析和纤维应力比计算时应考虑缠绕张力作用。     

含缠绕层缺陷大容积缠绕气瓶安全性能与评定研究

为研究缠绕层体积性缺陷及线性缺陷对大容积缠绕气瓶安全性能影响,通过对带有不同尺寸缠绕缺陷的大容积缠绕气瓶进行疲劳试验、爆破试验,并采用有限元分析等方法研究了不同尺寸的缠绕层缺陷对内胆应力状态、缠绕层应力状态影响。通过有限元分析,对于面积为250 mm×250 mm,深度为3 mm的体积性缺陷,内胆应力几乎未变,缠绕层应力增加38.9%,经历11 000次疲劳试验,未发生变化。在爆破试验中,对于含面积为250 mm×250 mm缠绕层缺陷的大容积缠绕气瓶,当缺陷深度分别为3 mm时,爆破压力下降9.9%,略低于设计爆破压力,仍满足安全使用要求,当缺陷深度为6 mm时,爆破压力大幅下降20.9%。研究结果表明,对于轴向长度不超过250 mm,深度不超过3 mm的缠绕层缺陷,大容积气瓶安全性能仍满足使用要求,如缺陷深度超过3 mm,可评定为Ⅲ级。     

基于ABAQUS含分层缺陷塑料内胆纤维缠绕气瓶红外检测研究

将ABAQUS有限元分析方法的计算结果和含分层缺陷塑料内胆纤维缠绕气瓶红外检测试验的实测结果进行对比。结果表明,基于ABAQUS的有限元计算结果与试验结果最大误差为16.36%,网格独立性检验表明,网格数量对有限元计算结果影响很小,最大误差为0.25%,在实际工程允许误差范围内,证明了有限元计算结果的准确性,为后续基于有限元方法研究含缺陷塑料内胆纤维缠绕气瓶红外检测提供借鉴。     

气瓶内衬屈服强度对环缠绕复合气瓶疲劳性能影响的研究

为考察气瓶内衬材料的屈服强度对环缠绕复合材料气瓶(CNG-Ⅱ)性能影响,利用有限元数值模拟的方法,在气瓶的结构参数、纤维缠绕层参数、内衬材料的抗拉强度、自紧压力一定的情况下,研究内衬屈服强度变化对气瓶疲劳寿命的影响。有限元分析结果表明,随着内衬材料屈服强度的增加,CNG-Ⅱ复合气瓶的自紧效果变差,工作压力下所受环向平均应力增大,疲劳寿命降低。同时,对三种不同规格尺寸的环缠绕气瓶在不同屈服强度下的疲劳试验数据进行分析,进一步验证了复合气瓶的寿命随着内衬屈服强度的增加而减小。因此,在CNG-Ⅱ复合气瓶的生产过程中,有必要在一定程度上降低内衬的屈服强度,以改善复合气瓶的性能。     

缠绕层表面2 mm 深椭圆损伤对 CNG -Ⅱ复合气瓶应力的影响

为了研究缠绕层外表面损伤对于CNG-Ⅱ复合气瓶安全性能的影响，通过考察实际气瓶表面损伤形状，将复合气瓶表面损伤简化为一定尺寸的椭圆形凹坑。对缠绕层表面带有2 mm深度椭圆形凹坑损伤的复合气瓶进行爆破试验，利用有限元软件ANSYS计算其爆破压力。比较试验爆破压力和数值分析结果，验证数值分析方法的正确性。在此基础上，对带椭圆形凹坑损伤的CNG-Ⅱ复合气瓶进行应力分析，得出缠绕层外表面椭圆形凹坑损伤对气瓶安全性能造成不良影响。     

非金属内胆全缠绕气瓶关键技术分析及研究

主要介绍了非金属内胆全缠绕气瓶在制备过程中的内胆成形关键技术以及复合材料层成形关键技术,提出了在产品开发阶段应注意的问题,为后续企业的研发提供一定的指导意义.     

Frictional evaluation of thermally sprayed coatings applied on the cylinder liner of a heavy duty diesel engine: Pilot tribometer analysis and full scale engine test

The piston system accounts for roughly half of the mechanical friction of an internal combustion engine, thus it is important to optimize. Different thermally sprayed cylinder liners were investigated in order to optimize the frictional impact of the contact between cylinder liner and piston ring/piston. A novel tribometer test setup was used to scan through different materials at different running conditions. Two cylinder liner materials showed significantly lower friction than the other tested materials, CrC–NiCr and MMC. All the thermally sprayed cylinder liners were worn significantly less than the reference material. Based on these results a full-scale single cylinder test was performed to validate the results from the rig. Comparing the thermally sprayed cylinder liner MMC with reference cylinder liner the test showed higher friction torque for the MMC cylinder liner except in one case; at low speed and high pressure. An analysis of the results between the tribometer and the engine points at the importance of the ratio between viscous and mechanical friction losses. The most probable cause of higher friction torque for the thermally sprayed coating (MMC) is that the functional surface of the cylinder liner promotes an increase in viscous friction.     

车用铝内胆碳纤维全缠绕氢气瓶设计要点

国家“十一五”863计划将铝内胆碳纤维全缠绕气瓶做为未来车载储氢容器的研究方向;适当增加内胆壁厚,增长裂纹扩展“路程”,提高疲劳寿命;铝内胆设计承载比例不宜小于12％;根据内胆材料应力一应变曲线、内胆和纤维的力学性能确定内胆设计应力取值为σa=σbσsa／σsb并可计算出内胆设计壁厚;内胆封头型式以矢高为1．25R／2左右的椭球为宜;螺旋缠绕角从与瓶颈相切的最小缠绕角开始逐渐增大,避免纤维严重堆积、架空,有效利用极孔处堆积纤维的过剩强度,提高成层质量和强度利用率;碳纤维首层张力不宜超过65N／mm^2,首次递减量不宜超过上一层纤维张力的4．0％;纤维排列状态设计应充分考虑工艺的可行性,确保稳定、高质量地实现设计;通过自紧,内胆应至少获得不小于1．3％的应变,最小理论自紧压力可近似计算为PZ=kPba／A。     

考虑贫油和高边界压力的发动机顶环-缸套润滑与承载性能分析

为降低发动机润滑油消耗以及由此带来的排放,活塞环缸套系统一般处于贫油润滑状态,特别是顶环与缸套间的贫油状况更严重。贫油状态下,活塞环-缸套间润滑油膜在出口区破裂后很难再形成,同时在燃烧上止点附近的高边界压力下气体承载也难以忽略。因此,以某柴油机顶环-缸套系统为分析对象,基于平均雷诺方程和无再形成边界条件,分析贫油和高边界压力下顶环-缸套界面间的润滑、接触和气体承载问题。研究结果表明,贫油工况下,由于油膜破裂后没有再形成,高边界压力的影响显著,对高爆压强化机型来说顶环-缸套间的气体承载力甚至会大于油膜承载力和接触承载力。     

重整预加氢氢气压缩机缸套磨损原因分析及解决措施

针对重整装置预加氢氢气压缩机缸套磨损的现象,通过对该压缩机十字头中心与滑道中心数据偏差校核,及对该压缩机活塞环、支撑环及气缸缸套材质分析,确定气缸缸套磨损的原因,提出对应的解决措施,使用液氮安装气缸缸套,为同类型压缩机检修提供经验共享.     

Running-in wear of a compression ignition engine: Factors influencing the conformance between cylinder liner and piston rings

The conformance between the liner and rings of an internal combustion engine depends mainly on their linear wear (dimensional loss) during running-in. Running-in wear studies, using the factorial design of experiments, on a compression ignition engine show that at certain dead centre locations of piston rings the linear wear of the cylinder liner increases with increase in the initial surface roughness of the liner. Rough surfaces wear rapidly without seizure during running-in to promote quick conformance, so an initial surface finish of the liner of 0.8 μm c.l.a. is recommended. The linear wear of the cast iron liner and rings decreases with increasing load but the mass wear increases with increasing load. This discrepancy is due to phase changes in the cast iron accompanied by dimensional growth at higher thermal loads. During running-in the growth of cast iron should be minimised by running the engine at an initial load for which the exhaust gas temperature is approximately 180 °C.     

Temperature—friction characteristics of cylinder lubrication in large,slow, cross‐head marine diesel engines under boundary lubrication conditions

In large, slow, cross‐head marine diesel engines research has increasingly shown that the lubrication regime between piston rings and cylinder liner at top dead centre is of the boundary lubrication type due to the high gas pressure, low sliding speed, and high temperature. This means that the tribological properties of piston ring, cylinder liner, and cylinder lubricant in these types of engine under boundary lubrication conditions should be considered simultaneously when friction and wear between the piston ring and cylinder liner are studied. Until now there has been no standard method to evaluate boundary lubrication performance. There are a few traditional methods used in lubricant research, but their results are not correlated with service conditions. It is important to find a suitable method to evaluate the boundary lubrication performance of lubricants at the laboratory testing stage or before the engine testing stage. The important parameters, such as sliding speed, normal load, materials of the contacting pairs, and lubricant, need all to be controlled. In this paper a systematic experimental procedure, the ‘five times heating and cooling test’, is introduced to assess lubricant properties under boundary lubrication conditions. Most of the parameters mentioned above are controlled. The model contact, of pin‐on‐plate form, is made from the actual piston and liner materials used in a large‐bore, slow, cross‐head marine diesel engine. The temperature characteristics of different blends of lubricants are investigated under boundary lubrication conditions using a pin‐on‐plate reciprocating test rig. These blends of lubricants have the same additives but different base fluids; they nevertheless fulfil the physical and chemical requirements of a real marine diesel engine. The test temperature range is from room temperature to the working temperature of the top piston ring. The experiments show that there are different temperature—friction characteristics for lubricants with different bases and the same additive package and there are also different temperature—friction characteristics during heating up and cooling down for each blend. Single‐base lubricants have more promising temperature—friction characteristics than those of a blend of a high‐viscosity base and a low‐viscosity base at high temperature.     

Hydrogen damage in 34CrMo4 pressure vessel steel with high tensile strength

Various efforts have been made to improve the safety of high-pressure gas cylinders for hydrogen or natural gas with high strength steel liners. Metal liners with high tensile strength have a safety concern, particularly with hydrogen gas or hydrogen generating environments. The hydrogen can permeate into the liner material, and make the material brittle, causing hydrogen damage. This study investigated resistance to hydrogen damage for two kinds of 34CrMo4 steel with different strength levels. Hydrogen was charged with the electrochemical method, and the material strength was measured by the small punch testing technique. Hydrogen concentration of the specimen was also measured for every testing condition, with various charging periods. The specimens with high tensile strength absorbed more hydrogen than the regular tensile strength specimens. The absorbed hydrogen caused internal damage of intergranular cracking and blistering. Material ductility at failure decreased, as the hydrogen concentration of the specimen increased. But the hydrogen concentration had virtually no effect on the strength of the materials with hydrogen. These results confirm that the susceptibility to hydrogen damage of the high tensile strength materials is much higher than that of the materials with regular strength. If the metal liner of a hoop-wrapped cylinder vessel of type II has high tensile strength, general corrosion at the liner surface can cause a hydrogen rich environment, and the cylinder can suffer hydrogen damage and embrittlement. Therefore, controlling the strength level under an optimal level is critical for the safety of a cylinder made with 34CrMo4 steel.     

钢丝缠绕予应力高压容器和冷挤压凹模在内压作用下内壁不出现拉应力的设计原理

钢丝或钢带缠绕予以应力高压容器或模具由芯筒和缠绕层两部分组成。缠绕层采用等剪应力方法充分利用了钢丝的强度,比采用等张或等切应力方法能承载更大的工作内压。芯筒多采用高强材料。为使芯筒不易开裂并提高疲劳寿命,要求在工作内压载荷下内壁不出现拉应力。本文提出满足这一要求的最佳设计方法和计算公式。     

钻井泵活塞缸套密封系统密封性能流-固耦合分析*

现有的关于钻井泵活塞皮碗受力情况的相关研究,大多忽略了钻井泵工作过程中活塞缸套与钻井液的流-固耦合作用,得出的结论与实际的受力特性有一定的差别。为研究活塞皮碗的受力情况,通过建立活塞缸套的有限元模型,采用流-固耦合方法来模拟活塞缸套受力特性,同时探讨皮碗过盈量以及唇角尺寸对其密封性能的影响。仿真结果表明：缸套与皮碗接触面之间受力变化规律与缸套内压力变化规律相似;在最大工作压力作用下,缸套内表面和垫圈表面与皮碗接触部位等效应力都较大,但相较于缸套和垫圈,皮碗是活塞密封中最易失效的部件;皮碗的应力主要集中在活塞皮碗的唇部及根部与垫圈接触处,而这也是皮碗易发生失效的2个部位;当皮碗过盈量大于1.0 mm,唇角大于15°时,皮碗唇部会产生向心效应,进而影响皮碗的密封性能。