机械加工强化机理与工艺技术研究进展

综述了两种机械加工强化机理：组织强化和应力强化。根据晶体位错理论分析,组织强化通过改变金属材料微观组织,提高位错密度,使材料流变应力增加,强度提高。介绍了用于解释机械加工位错强化、晶界强化、应变强化、择优取向强化的理论模型及各强化机理在机械加工强化中的作用,分析了应力强化中残余应力的产生原因。以文献研究为基础,总结了机械加工工艺强化原理和工艺设备的发展现状,讨论了机械加工强化机理和强化工艺的对应关系,指出了机械加工强化工艺的发展方向。     

轴承零件的选材及相应强化工艺

轴承是机械设备中应用最广泛的零件之一，其型号有十几万种，结构尺寸和服役条件既有相似之处，也有诸多不同。而制造轴承零件的材料也有数百种，其性能和适用范围也各有不同。同时，材料的强化工艺达上百种，每种工艺都有其优缺点和较佳的应用范围。材料及其强化工艺是影响轴承各项性能的重要因素，也是影响轴承制造成本的重要因素，选择材料是轴承设计制造的重要环节之一，合理地选择材料及其强化工艺可以使轴承获得良好的性能价格比，具有极大的经济效益和社会效益。要合理地选择材料，必须考虑轴承的服役条件和失效形式、轴承零件的结构和尺寸、材料的性能、价格及强化工艺、制造单位的加工条件和加工成本等多方面因素，具有较大的难度，本文对此进行初步探讨。     

激光热处理技术的研究现状及发展

主要阐述了激光相变硬化的特点及强化机理,激光表面相变硬化工艺,包括材料表面预处理、激光相变硬化工艺参数、扫描方式等。文中分析了钢铁材料激光相变硬化后的组织与性能,介绍了近年来激光相变硬化技术在材料科学领域的研究状况。     

金属材料喷丸强化有限元模型的演变及展望

喷丸强化工艺是将金属或非金属弹丸高速撞击金属构件,使构件表面产生弹塑性变形的过程,这些变形在材料表层产生具有一定厚度的残余压应力层和组织强化层,从而使得构件材料表面得到强化,并最终显著提高构件的疲劳强度。介绍了喷丸强化工艺的基本原理、特点和相关工艺参数,对有限元分析模型:包括弹丸数量、弹丸分布规律和靶材模型的简化程度等几个方面的演变情况进行了分类归纳和比较,总结了喷丸强化工艺参数对残余应力场的影响规律,对未来喷丸强化机理的研究工作进行了展望。     

强化应力及预强化处理对平板焊接残余应力的影响

根据06Cr19Ni10奥氏体不锈钢材料的室温拉伸试验结果,采用ANSYS有限元软件对不同屈服强度下平板焊接过程及焊后强化过程进行了数值模拟分析。结果表明,焊后强化并不能完全消除焊接残余应力,但可以显著改善焊接残余应力的分布;对不同强化工艺下平板的焊接残余应力进行比较,指出对材料进行预强化处理更有利于改善焊接残余应力。模拟分析结果可为应变强化工艺参数筛选提供一定的参考。     

硬喷丸强化对提高渗碳齿轮疲劳强度的研究

通过对渗碳齿轮试片进行多次对比硬喷丸试验，揭示了硬喷丸强化效果与材料、喷丸工艺参数及热处理间的影响关系，为硬喷丸工艺更好地应用于工业生产提供了较好的方案。     

影响结构钢喷丸强化效果的材质因素

本文论述了结构钢组织状态、机械性能、碳含量和残余应力对喷丸强化效果的影响。各种材料,不同热处理状态,不仅喷丸强化效果不同,强化规律也有所不同。本文针对结构钢材料的不同组织状态提供了适当的强化工艺.     

汽车6061铝合金材料切削加工理论及实验研究

以汽车6061铝合金材料为研究对象,采用冶金技术通过添加强化相粉煤灰制备样品,基于灰色多响应优化理论建立不同工艺参数下切削加工理论模型,同时进行不同工艺参数的实验,运用理论及实验方法研究了不同工艺参数对汽车6061铝合金材料切削加工的影响。研究表明:汽车6061铝合金材料硬度随着强化相粉煤灰增加而增加,其密度却呈现相反趋势;切削加工过程中复合汽车材料表面粗糙度随着切削速度、填充物增加而逐渐降低,表面粗糙度随着进给量增加而增加; PCD刀具切削加工的复合汽车材料表面粗糙度明显低于K10硬质合金钢刀具;理论计算值与实验值相对误差较小,验证该理论及试验方法正确性和为其在新型汽车铝合金复合材料制备及切削工艺改善等工程应用提供可行性。     

激光表面强化中的工艺问题

介绍了激光表面强化的工艺原理、特点以及提高材料表面对激光能量吸收率的措施,并讨论了激光表面强化工艺参数对硬化层深度和硬度的影响。     

锻-热联合工艺在35CrMo螺栓热处理上的应用

锻-热联合工艺即形变热处理，使压力加工和热处理密切结合，同时利用形变强化及相变强化。这种工艺可使材料获得单一强化方法所不能达到的综合性能，从而有效地发挥金属的强韧性潜力。此外，形变热处理方法又可充分利用压力加工余热，省去再加热工序，并大量节约能源、设备、材料和管理费用，减少零件再加热时的氧化脱碳、扭曲变形等缺陷。     

U70MnSi和40Cr钢电火花表面强化层的组织与性能

采用硬质合金YG-8和焊条FW-1101作电极,在电火花表面强化器上强化了U70MnSi钢和40Cr钢的表面;用X射线衍射仪分析了强化层的结构,用滚动和滚、滑磨损试验研究了强化层的耐磨性,用阳极极化和浸泡试验研究了40Cr钢表面强化后的耐腐蚀性能。结果表明：强化层是由化合物和非晶组织组成的混合层;表面强化后试样的耐磨性明显提高;40Cr强化层的混合组织对耐腐蚀性能的影响超过了层中缺陷和残余应力的影响,使其耐腐蚀性能提高。     

低载强化特性在汽车结构件设计中的应用

提出了一种汽车结构件的设计方法。该方法以材料和结构件的低载强化特性为依据，以经低应力载荷强化后的材料或结构件的疲劳极限提高的最大临界载荷为目标，以提高可承受的使用应力为核心，在保证汽车使用性能的前提下，充分发挥结构的强度潜力，实现在减轻质量的同时降低成本的汽车轻量化设计，同时也为其它车辆和机械的结构轻量化设计提供了技术参考。     

Experimental studies on performance of reinforced concrete beam strengthened with CFRP under cyclic loading using FBG array

Investigations are increasingly being carried out in the area of utilizing Fiber Reinforced Plastic (FRP) materials for retrofitting and repairing existing damaged concrete structures due to their excellent properties. Favorable mechanical and material characteristics of FRP composites make them attractive for strengthening applications, whereas relatively higher material costs, insufficient knowledge in mechanics of their behavior, long-term durability and lack of related design codes are the issues that need to be addressed for mainstream application of these materials. Although there has been growing interest and field applications of strengthening concrete structures using Carbon Fiber Reinforced Plastic (CFRP) sheet/plate, very little information exists regarding the flexural fatigue behavior of reinforced concrete beams strengthened with CFRP. A common cause of failure in such strengthened members is associated with the debonding of CFRP substrate from the concrete in an abrupt manner. In order to understand the mechanism of debonding in strengthened concrete structures, embedment of strain sensors (Fiber Bragg Grating (FBG) array) between the concrete and CFRP is proposed in this paper. Due to the compatibility with CFRP material and being small in size, fiber optic sensor is a good choice for embedding at the interface to measure interfacial strain. This paper presents the experimental studies carried out on CFRP strengthened concrete members subjected to cyclic loading. A special emphasis has been placed on understanding the failure pattern using the embedded FBG sensors. Based on the studies it is concluded that the strain at the interface of CFRP strengthened concrete members can be measured.     

陶瓷粉末种类对聚氨酯复合材料冲蚀磨损性能的影响

用聚四氢呋喃醚二醇(PTMG)、甲苯二异氰酸酯(TD I)反应,与不同种类的陶瓷粉末进行共混,制得耐磨蚀聚氨酯复合材料。评价了聚氨酯陶瓷复合材料的耐磨性,通过扫描电镜观察了聚氨酯陶瓷复合材料的磨损形貌,探讨了陶瓷粉末增强聚氨酯弹性体的磨损机制。结果表明:当—NCO含量为6.35%,Si3N4粉末、TiN粉末质量分数为10%时,耐磨性能最好,分别提高纯聚氨酯弹性体抗冲蚀磨损性能1.88倍和2.81倍。     

聚氨酯陶瓷复合材料的抗冲蚀磨损性能研究

用聚四氢呋喃醚二醇和甲苯二异氰酸酯反应后，与陶瓷粉末进行共混，制得抗冲蚀磨损的聚氨酯复合材料。用相对抗冲蚀磨损性法评价了聚氨酯陶瓷复合材料的耐磨性，通过扫描电镜观察了聚氨酯复合材料的磨损形貌，解释了微米级陶瓷粉末增强聚氨酯的抗冲蚀磨损性能机理。结果表明，Si3N4粉末质量分数在5％～10％时，复合材料抗冲蚀磨损性能是聚氨酯的1．87倍，TiN聚氨酯复合材料抗冲蚀磨损性能是聚氨酯的2．81倍。     

Wear properties of cemented carbides/Cu-based alloy composite strengthening materials for milling shoes

The microstructure and wear behavior of WC–8TiC–3TaC–8Co cemented carbide and CuZnNi alloy composite strengthening materials have been investigated by means of scanning electron microscopy (SEM), electron dispersion X-ray analysis (EDAX) and wear test. Effect of applied load and sliding distance on the wear behavior of the strengthening materials are also studied in this paper. The results show that the cemented carbide particles are surrounded by the α + β phases in the hardfacing layers. There exists an inter-diffusion zone at the interface of the cemented carbides and Cu-based matrix due to the mutual diffusion of elements. The wear volume of both the WC–8TiC–3TaC–8Co/CuZnNi and WC–8Co/CuZnNi composite strengthening layers increased with the increasing of applied load. The WC–8TiC–3TaC–8Co/CuZnNi hardfacing layers exhibited lower wear volume loss than that of WC–8Co/CuZnNi. According to the results of engineering application, the working efficiency and employing life of the milling shoes, which were strengthened by WC–8TiC–3TaC–8Co/CuZnNi composite materials, is by approximately two to three times the milling tools strengthened by WC–8Co/CuZnNi.     

Wear properties of cemented carbides/Cu-based alloy composite strengthening materials for milling shoes

The microstructure and wear behavior of WC–8TiC–3TaC–8Co cemented carbide and Cu–Zn–Ni alloy composite strengthening materials have been investigated by means of scanning electron microscopy (SEM), electron dispersion X-ray analysis (EDAX) and wear test. Effect of applied load and sliding distance on the wear behavior of the strengthening materials are also studied in this paper. The results show that the cemented carbide particles are surrounded by the α-Cu + β-Zn phases in the hardfacing layers. There exists an inter-diffusion zone at the interface of the cemented carbides and Cu-based matrix due to the mutual diffusion of elements. The wear volume of both the WC–8TiC–3TaC–8Co/CuZnNi and WC–8Co/CuZnNi composite strengthening layers increased with the increasing of applied load. The WC–8TiC–3TaC–8Co/CuZnNi hardfacing layers exhibited lower wear volume loss than that of WC–8Co/CuZnNi. According to the results of engineering application, the working efficiency and employing life of the milling shoes, which were strengthened by WC–8TiC–3TaC–8Co/CuZnNi composite materials, is by approximately two to three times the milling tools strengthened by WC–8Co/CuZnNi.     

Experimental modal analysis of masonry arches strengthened with graphene nanoplatelets reinforced prepreg composites

Strengthening of masonry structures with different engineering materials has become a challenge for civil engineers with the advancements in engineering technology. This study mainly focused on dynamic parameters of masonry arches, which were strengthened with nanoparticle reinforced prepreg composites. For this purpose, the prepreg composites were produced with carbon fiber and epoxy system which was reinforced with graphene nanoplatelets particles that was 1 wt% of the epoxy system. Afterwards, four different strengthening alternatives were performed at the extrados and intrados of the masonry arches. Finally, dynamic characteristics such as mode shapes and modal frequencies of unstrengthened and strengthened arches were determined through experimental modal analysis (EMA) and numerical analysis.     

Contribution of functionally graded material modelling on finite element simulation of rod end parts in automotive steering system

One of the most important manufacturing steps of the rod end materials is the induction process by which the both hardness of the surfaces and the toughness of the part can be adjusted at the same time. In the study, rod end materials which are inducted and non-inducted are simulated in the view of the fatigue life properties. In the simulations, the rod end parts are defined as functionally graded materials where the mechanical properties of the materials are varying with the dimensions. Additionally, the noninducted material properties or fully strengthened material properties are defined for the geometry in order to comprehend the contribution of the definitions on the congruity of the finite element simulation results with the experiments. When the materials properties of the rod end part are defined as functional graded, the simulation results are found to be much more close to the experimental results.

     

粉末球磨预处理对高硅铝合金材料组织与物理性能的影响

为制备出能满足使用要求的高硅铝合金电子封装材料,采用高能球磨对Al-Si合金粉末进行氧化预处理,结合包套热挤压制备Al2O3与SiO2增强的弥散强化型铝硅复合材料,并采用透射电镜、金相显微镜及热物性测试仪,对材料显微组织、密度、气密性、热膨胀系数及热导率进行分析测试.试验结果表明:与高温空气氧化相比,粉末高能球磨后,所制备材料的晶粒更加细小,特别是硅粒子已明显细化;粉末球磨后所制备材料密度接近于理论密度,其致密度在99%左右;材料气密性很好,在1 nPa·m3·s-1以下;材料热膨胀系数随粉末球磨时间延长而下降,当球磨时间超过24 h后,材料膨胀系数小于13 (K-1;随着球磨时间延长材料热导率增加,球磨32 h后,材料热导率高达145.5 W·m-1·K-1.