为了在工科类"工程制图"大班教学中激发学生学习的主动性,培养形象思维能力和分析问题能力,探讨在课内外的教学中采用问题教学法和小组合作学习法,详细介绍教学法实施过程、应注意的问题和实施的具体事例,并进行了跟踪调查,显示教学效果良好.

为检验水下密封结构的可靠性,利用Ansys Workbench集成平台对有无挡圈配合的O形密封圈的变形和受力情况进行比较分析,并对深水环境中有挡圈配合的O形圈的密封性能进行数值模拟分析.结果 表明:在介质压力较大时,有挡圈配合的O形圈可有效防止挤入咬伤,在同样保证密封可靠的条件下最大Von Mises应力可减小20％以上;当介质压力为10 MPa左右时,有挡圈配合的O形圈的最大Von Mises应力有明显的拐点,介质压力大于10 MPa后,O形圈的应力变化趋于平缓,可避免O形圈被破坏导致的密封失效;有挡圈配合的O形圈结构中,起密封作用的是O形圈而非挡圈,挡圈的作用主要是改善O形圈的受力,提高整个密封结构的可靠性.模拟的结果可以说明O形圈配合挡圈提高密封可靠性的原理,为水下密封结构的可靠性检验和密封结构的优化提供了有效的方法.

为降低入水冲击中机翼所承受的水动力,提出利用水溶性材料使水下滑翔机的机翼在入水前收紧、入水后展开.针对选定的水溶性材料,进行干燥状态和浸水状态的拉伸试验.在干燥状态下,分析材料带宽度及层数对材料带力学特性的影响.在浸水状态下,测试不同宽度和层数水溶性材料带在给定负载作用下的溶水断裂时间.试验结果表明:材料的拉伸极限载荷随材料厚度的增大而增大,变化规律为线性;当采用相同的材料带宽度和层数时,水溶膜的抗拉能力最强,无纺布的抗拉能力最弱;在给定负载作用下,无纺布的溶水断裂最快.综合考虑材料的力学性能和水溶性能,选定无纺布作为机翼的绑扎材料;展翼模型试验验证了提出的展翼方法的可行性.

利用Workbench软件模拟不同压缩率下静水压力对O形圈变形、范·米塞斯应力和接触压力的影响,得到其间的对应关系.计算表明,静水压力对密封圈变形的影响随着压缩率的增大而减小;压缩率较小时,静水压力的增加会引发挤入现象,从而使范·米塞斯应力急剧增大,导致密封圈破坏,故水深较大时,需较大的压缩率或添加挡圈;在不同的压缩率下,接触压力随静水压力的增加而增大,最大接触压力始终大于静水压力,可保证其正常的密封性能.计算结果可为完善水下滑翔器密封结构的设计提供参考.

零件图的教学难点集中表现在视图表达方法选择、尺寸标注等方面.本文以从动轴零件图的教学为例,从结构设计、视图选择、径向和轴向尺寸标注等环节,结合加工过程讲解从动轴零件图的绘制过程,将生产实践与理论知识有效结合,有助于学生更好地理解课本内容,提高学习效率.

碟形水下滑翔器作为一种优点众多的新型水下滑翔器,近年来得到广泛应用.其液压浮力调节系统、姿态控制系统以及转向控制系统必须安装在耐压壳体内部,因此,对于耐压壳体的设计来说,尽量小的重量和尽量大的有效容积是其设计时的重要技术指标.为了得到最优结构,采用尺寸优化方法,以壳体厚度、两道环肋的高度作为设计变量对耐压壳进行优化设计,以期达到强度足够高、最大变形值小于容许变形值和质量最小的轻量化目标.优化后,质量较初始设计减少了30％,轻量化效果明显,并对最终选择的结构进行屈曲分析,其临界压力远大于许用压力.

In order to study the influence of supply pressure on the carrying capacity of texture surface, a single two-dimensional (2D)calculation model of micro groove texture is established.Using the method of CFD numerical simulation,as the change of supply pressure,the changing rules of the cavitation effect, gas volume rate,pressure distribution and carrying capacity of top were obtained. The results show that when inlet pressure is small enough,cavitations will be generated in the divergence zone of texture inlet,the max-imum gas volume rate decreases with the increase of supply pressure.In terms of the regional distribution of cavitation, with the in-crease of pressure,the cavitation area gradually spreads, until completely dissipated, the cavitations disappeared.No matter whether generated cavitations,the carrying capacity of texture will linear proportional increase with the supply pressure.

工程制图是工科类学生的专业基础课,为了激发学生学习的主动性和积极性,加强学生对课程知识的掌握及相关能力的培养,在教学中可采用多种教学方法.本文结合多年的教学经验,分析了问题探究教学法、案例教学法、竞赛激励法和小组式学习法的教学特点、教学实施中的关键问题及在课程学习中的具体应用.本文提出的这些教学方法在制图课程的教学中具有可操作和实用性.

图学与美学同属于形象思维范畴,他们在形式与内容上互相渗透,创造者的设计意图需要通过工程图样来表达,美的产品设计只有与工程图样相结合才能在产品中显示它的艺术魅力;而图样只有融入美学才能使设计变得完美,在工程图学教学中融入美学因素是十分必要的.将美学思想融入到工程图学教学的各个环节,用美学原理解释工程制图课程的学习内容,辅以按照美的规律而进行的教学活动,引导学生发现、感受图样中的美,并在此基础上去创造美和表达美,改变枯燥、乏味的课堂教学,让学生在美的情境中不断培养学习兴趣,激发学习动力,使教和学真正成为一个愉快的过程,对于提高教学质量、深化素质教育都有着积极而深远的意义.

分析"以赛带教"培养方式的作用和目的,借鉴国际和国家级的制图相关竞赛内容与形式,提出"以赛带教"的实施方式和两种适合班级开展的竞赛形式,并对竞赛内容及实施中应当注意的问题进行深入阐述.

In order to study the influence of slip velocity on the cavitation effect of texture surface,a single two-dimensional calculation model of micro convex body texture was established.Using the method of CFD simulation,as the change of sliding velocity,the changing rules of the cavitation effect in gas volume rate,pressure distribution and wall shear stress were obtained.The results show that when sliding speed is not more than 5 m/s,any cavitations can not be produced on the texture surface of the fluid;when the slip velocity gradually increases from 5 m/s to 20 m/s,cavitations will be generated in the convergence area of texture fluid outlet,and the size of the cavitations will be decreased with the increase of the slip velocity,and the gas volume rate of the cavitations will be increased with the increase of the slip velocity;when the slip velocity continues to increase from 20 m/s to 30 m/s and reaches a certain value,the size of the cavitations will be decreased no longer,and the gas volume rate of the cavitations still increases with the increase of the slip velocity;when the slip velocity is between 5 m/s to 30 m/s,the greater slip velocity will be corresponding to the greater extra capacity and the greater wall shear stress.In addition,the existence of cavitations will contribute to reduce the wall shear stress.

Purpose– The purpose of this study is to solve this problem. Different lubrication states play a huge role in friction, wear and service life of parts. To ensure the reliability and power of the internal combustion engine, it is necessary to ensure that the friction pair has been in the best lubrication state. One of the key problems of lubrication state and transformation characteristics is to achieve real-time measurement of lubrication state.Design/methodology/approach– Previous studies show that the contact resistance method is very effective in the qualitative analysis of lubrication state test. The circuit is simple and does not require expensive test equipment. But this method could not accurately reflect the film thickness ratio. Through a combination of experimental and theoretical analysis methods, the limitation of the contact resistance method could be overcome.Findings– The relationship between the point contact film-thickness ratio and contact resistance was established, then the film-thickness ratio could be obtained through the contact resistance, thus providing the basis for determining the point contact lubrication state.Research limitations/implications– According to existing research, the lubrication state of the friction pair mainly was determined through two methods, the friction coefficient and film-thickness ratio. But there are limitations on either using Stribeck curves or optical interference methods. The method used in this paper not only provides a verified way of design theory and model, but is also beneficial to the formation of a new design theory.Originality/value– A new real-time measurement method of lubrication state based on contact resistance is established and its practicability and veracity are verified by series experiments.

摩擦表面的表面织构具有改善摩擦副表面接触方式和润滑状态的作用.采用格子Boltzmann方法对表面织构进行数值模拟分析,采用D2Q9二维速度模型,非平衡外推边界处理格式,编写了模拟的计算程序,模拟出二维方槽、三角形槽及梯形槽织构表面的流动.针对上述流动,计算出雷诺数不同时的流线图,并分析了不同形状凹槽流动的变化,计算了不同形状、深度条件下阻力系数的变化并概括了影响规律.通过对表面阻力的比较发现:梯形凹槽是最优的表面织构;由方形槽的模拟可知,织构形状的深径比也存在最优值,从而证明了Bohzmann方法是模拟复杂流体运动的有效方法.

Cam mechanism is widely used as a common mechanism in automated or semi-automated machinery. To improve the cam mechanism design, efficiency and quality of machining process, a direct-acting roller follower disk cam mechanism was designed and simulated based on PRO/E. Computer-aided design and simulation methods of Cam mechanism were introduced, the movement of mechanism was very intuitive and the curve of each power parameter was available. The simulation allows designers to grasp and control the movement of mechanism and accuracy, increases design safety factor. The validity and reliability of the design were tested by comparing the results of the design and simulation analysis.

Purpose – The purpose of this paper is to establish a rapid and effective numerical model of thin film lubrication with clear physical conception, in which viscosity variation along the direction of film thickness was used instead of average viscosity, and continuous Reynolds equation was used in the calculation of thin film lubrication. Design/methodology/approach – Based on rheology and thin film lubrication with point contact and considering features of shear thinning and like-solidification of lubricant oil in the thin film lubrication state, a modified formula with overall average equivalent viscosity was proposed by combining numerical calculation and experiment data. Findings – It is a fast and efficient method for film lubrication state simulation. Research limitations/implications – Thin film lubrication research on a nanoscale is very popular, and a variety of thin film lubrication models are proposed. Due to the complexity of thin film lubrication, it is still in the stage of revealing law and establishing calculation model. Originality/value – The key issue is how to obtain the viscosity correction formula derived from engineering practice, also considered the lubricating oil class solidification and shear-thinning properties on thin film lubrication, while based on the system experiment, the viscosity modified formula for the gap, speed changes are proposed to obtain the overall average equivalent viscosity which makes the thin film lubrication micro to macro, so that a clear physical meaning for thin-film lubrication numerical calculation model is established.

For the friction pair of cylinder liner and piston ring ,the effects of surface roughness ,variable viscosity effect and circumferential deformation on lubrication condition were researched .A three‐dimensional transient hydrodynamic lubrication model of cylinder liner‐piston ring was built based on the three‐dimensional transient average Reynolds equation and asperity contact model and the calculation program of lubrication condition was written with FORTRAN language .The minimum film thickness ,pressure distribution and friction curve were acquired with the program .By comparing the simulation results with those achieved under the actual working conditions ,the oil film pressure and thickness distribution in the circumferential direc‐tion of piston rings was found to be uneven .On the top end of compression stroke ,the asperity friction force was much larger than the fluid friction force ,which was the main cause for friction and wear .

Acoustic fault diagnosis system of diesel engine is based on the analysis of the measured sound signals and try to extract the fault information contained in the signals which can be able to characterize the fault, and the contents of the research relates to the separation and feature extraction of the sound signal. In this paper, the research object is the diesel engine air valve abnormal sound signal. In order to identify the fault type, some digtal signal analysis methods such as digital filtering, wavelet transform and power spectral analysis method are adopted to extract and separate the abnormal sound signal. The results show that the methods owning some good analysis effects expressed as small amount of calculation and easy-to-real-time processing, which will contribute to the development of online sound fault detection device.

结合轮机专业工程制图的课程特点，通过活动教学与传递教学的比较，形成两者在工程制图课堂的和谐统一，建立活动教学与传递教学融合的教学模式，既保证基础理论的深度和广度，又兼顾实践能力、创新能力的培养。

针对工程制图课程传统教学模式无法适应新形势下人才培养要求的问题，采用多媒体和网络技术等现代教学手段规划构建立体、高效的现代教学模式，该网络教学系统通过图形、图像、动画、模拟装配、视频等多种方式交叉转换，化静为动，全面生动展示教学内容，既可为教师备课提供丰富的教学资源，又可以帮助学生自学，实现了教学效果的优化。

This paper constructs a three-dimensional transient hydrodynamic lubrication model for cylinder liner-piston ring based on the three-dimensional transient average Reynolds equation and asperity contact model. A computer program was written with FORTRAN to calculate hydrodynamic lubrication, in which the surface roughness, the variable viscosity effect and the deformation of the circumferential direction of the cylinder liner are taken into account. The film pressure distribution in different crank angle during the stroke, minimum film thickness and friction are computed and analyzed with this program. This three-dimensional transient hydrodynamic lubrication model provides a design basis for the friction analysis of cylinder liner-piston ring.