等温淬火时间对铁道机车用SAE8620轴承钢接触疲劳性能的影响

将表面渗碳处理的SAE8620轴承钢在855℃奥氏体化后,在225℃盐浴中进行等温淬火处理,再在225℃下进行回火处理,研究了等温淬火时间(7,21 h)对试验钢显微组织、物相组成、硬度和接触疲劳性能的影响。结果表明：等温淬火7 h时试验钢表层组织为贝氏体铁素体、残余奥氏体、马氏体和碳化物,等温淬火21 h后表层组织中的马氏体消失,贝氏体板条平均宽度增加,针状贝氏体铁素体含量增加,残余奥氏体含量减少;与等温淬火21 h相比等温淬火7 h试验钢的表层硬度更大,接触疲劳寿命也更长,这主要与其表层残余奥氏体含量更高、贝氏体板条平均宽度更小、表层硬度更大,可以更好地抵抗塑性变形有关。     

奥氏体化时间对I&Q&P工艺处理低碳硅锰钢组织和拉伸性能的影响

在不同奥氏体化时间下对低碳硅锰钢进行IQP处理,研究了奥氏体化时间对试验钢组织与拉伸性能的影响。结果表明:短时间奥氏体化不能完全消除之前锰元素在双相区的配分结果;奥氏体化时间达到300s后,试验钢的室温组织为板条状马氏体和残余奥氏体;随奥氏体化时间延长,试验钢的抗拉强度先升高后降低,最高可达1 267 MPa,但试验钢的伸长率则不断降低;刚完成完全奥氏体化时,晶粒尺寸较小,且碳、锰的聚集程度最佳,此时残余奥氏体的含量最高,形变过程中TRIP效应明显,使得伸长率的降低得以补偿;奥氏体化时间为300s时,试验钢的强塑积最高,可达30 345 MPa·%。     

亚温淬火工艺对45钢组织性能的影响

将具有平衡态的或者是非平衡态原始组织的亚共析钢进行加热,加热到铁素体与奥氏体共存的两相区即临界区温度区间,保温一定时间后再进行淬火,这种淬火方式被称为亚温淬火。本次试验研究在亚温淬火条件下,淬火温度和回火温度对45钢强度和硬度的影响规律,分析该钢亚温淬火后的组织与性能,同时研究了亚温淬火条件下奥氏体晶粒细化的特点和马氏体转变的特点。研究结果表明,在800~840℃,随淬火温度升高,45钢的强度升高,硬度降低。     

缸简亚温淬火

液压零件中油缸的缸筒设计要求采用35、45钢调质处理,薄壁的筒状零件采用常规的调质处理易变形或者开裂。在生产实践中,我们经多次验试采用了亚温淬火新工艺,新工艺实施后取得了显著效果。一、亚温淬火基本原理亚温淬火亦称两相区加热淬火,或称临界区淬火,是将亚共析钢加热至奥氏体和铁素体两相区后进行淬火,随后回火。这种工艺方法可以提高钢的韧性,降低脆性转变温度以及抑制可逆回火脆性。目前有这样的解释:由于亚温淬火加     

锰配分温度对I&Q&P处理后低碳硅锰钢组织与力学性能的影响

对低碳硅锰钢进行了不同锰配分温度下的双相区保温+奥氏体化+淬火碳配分(IQP)热处理,研究了锰配分温度对该钢显微组织和力学性能的影响。结果表明:随着锰配分温度的升高,IQP热处理后试验钢中马氏体晶粒变大,板条变粗,板条间距变宽;试验钢的伸长率和残余奥氏体含量均呈先增加后减小的变化趋势,抗拉强度则呈线性下降;当锰配分温度为800℃时,试验钢的综合性能最佳,强塑积可达29 046.65 MPa·%。     

超级贝氏体组织中残余奥氏体的TRIP效应研究

针对超级贝氏体组织中残余奥氏体的应力诱发相变及对钢的力学性能影响,设计试验钢60Mn2SiCr,经900 ℃完全奥氏体化保温30 min,在260 ℃盐浴炉中等温处理12 h后,将试样在疲劳试验机上进行加载试验;利用扫描电镜(Scanning electron microscope, SEM)、透射电镜(Transmission electron microscope, TEM)、X射线衍射仪(X-ray diffracmeter, XRD)和拉伸试验机等仪器设备对加载前后的样品,分别进行显微组织形貌观察和相组成的定性定量检测分析以及力学性能测试;结果显示,等温处理后样品的显微组织为超级贝氏体(贝氏体铁素体BF+残余奥氏体AR),残余奥氏体体积分数为9.4%,其含碳量为1.296%;经加载后试样显微组织中残余奥氏体体积分数下降至6.1%,含碳量达1.439%;钢的强塑积提高近20%。这说明等温处理获得超级贝氏体组织的钢,经施加载荷给予应力作用,显微组织中残余奥氏体发生转变,即超级贝氏体组织中的残余奥氏体能够通过相变诱发塑性(Transformation induced plasticity, TRIP)效应的产生,提高钢的力学性能。     

超高强度钢40CrNi2Si2MoVA贝氏体等温淬火工艺

对超高强度钢40CrNi2Si2MoVA进行贝氏体区短时间等温淬火,得到马氏体加下贝氏体和少量残余奥氏体的复合组织,考察了等温时间的变化对材料显微组织和力学性能的影响,并进一步得出了此条件下该钢的最佳热处理工艺.结果表明:当等温时间在100～150 s时,得到以马氏体为主,含20%左右下贝氏体和少量稳定残余奥氏体的组织.     

（F＋M）双相15钢的组织与性能

研究了15钢在不同热处理条件下的显微组织和拉伸性能。结果表明，发展岛状（F M）双相组织和纤维（F M）双相组织是提高15钢强塑性的有效途径。探讨了亚温淬火与亚温形变淬火的最佳工艺，并讨论了双相钢的加工硬化行为。     

热处理工艺对高硅铸钢组织与性能的影响

试验结果表明：高硅铸钢在280～360℃等温淬火,可以获得强度、韧性、硬度配合良好的双相组织;试样中残余奥氏体的含碳量及其含量随等温淬火温度的升高先增大后减小,均在360℃时出现最大值;奥氏体化温度和时间为900℃×120min、等温淬火温度和时间为320℃×120min时,可以获得较佳的综合力学性能,是替代高锰钢、低合金钢、奥-贝球铁等耐磨材料的新一代耐冲击磨损材料,应用前景广阔。     

硅对等温淬火高硅铸钢组织和性能的影响

研究了硅对高硅铸钢等温淬火后的显微组织和力学性能的影响。结果表明,硅含量为２．６４％左右时,可以得到完全由贝氏体铁素体和富碳残余奥氏体组成的无碳化物奥－贝组织。硅量过低,组织中会出现马氏体;硅量过高,组织中会出现残留的未转变奥氏体组织。随着硅含量的增加,抗拉强随之降低,硬度值几乎不变,而冲击韧度先逐渐提高,而后又有所下降。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.