Synergistically Toughening Effect of SiC Whiskers and Nanoparticles in Al_2O_3-based Composite Ceramic Cutting Tool Material

In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

COATED CARBIDE TOOL'S CUTTING PERFORMANCE AND ITS DATA BASE

The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.

Market-based control strategy for long-span structures considering the multi-time delay issue

To solve the different time delays that exist in the control device installed on spatial structures, in this study, discrete analysis using a 2N precise algorithm was selected to solve the multi-time-delay issue for long-span structures based on the market-based control （MBC） method. The concept of interval mixed energy was introduced from computational structural mechanics and optimal control research areas, and it translates the design of the MBC multi-time-delay controller into a solution for the segment matrix. This approach transforms the serial algorithm in time to parallel computing in space, greatly improving the solving efficiency and numerical stability. The designed controller is able to consider the issue of time delay with a linear controlling force combination and is especially effective for large time-delay conditions. A numerical example of a long-span structure was selected to demonstrate the effectiveness of the presented controller, and the time delay was found to have a significant impact on the results.

An improved cut-based recursive decomposition algorithm for reliability analysis of networks

In this paper, an improved cut-based recursive decomposition algorithm is proposed for lifeline networks. First, a complementary structural function is established and three theorems are presented as a premise of the proposed algorithm. Taking the minimal cut of a network as decomposition policy, the proposed algorithm constructs a recursive decomposition process. During the decomposition, both the disjoint minimal cut set and the disjoint minimal path set are simultaneously enumerated. Therefore, in addition to obtaining an accurate value after decomposing all disjoint minimal cuts and disjoint minimal paths, the algorithm provides approximate results which satisfy a prescribed error bound using a probabilistic inequality. Two example networks, including a large urban gas system, are analyzed using the proposed algorithm. Meanwhile, a part of the results are compared with the results obtained by a path-based recursive decomposition algorithm. These results show that the proposed algorithm provides a useful probabilistic analysis method for the reliability evaluation of lifeline networks and may be more suitable for networks where the edges have low reliabilities.

Depth Based View Synthesis Using Graph Cuts for 3DTV

In three-dimensional television (3DTV), an interactive free viewpoint selection application has received more attention so far. This paper presents a novel method that synthesizes a free-viewpoint based on multiple textures and depth maps in multi-view camera configuration. This method solves the cracks and holes problem due to sampling rate by performing an inverse warping to retrieve texture images. This step allows a simple and accurate re-sampling of synthetic pixels. To enforce the spatial consistency of color and remove the pixels wrapped incorrectly because of inaccuracy depth maps, we propose some processing steps. The warped depth and warped texture images are used to classify pixels as stable, unstable and disoccluded pixels. The stable pixels are used to create an initial new view by weighted interpolation. To refine the new view, Graph cuts are used to select the best candidates for each unstable pixel. Finally, the remaining disoccluded regions are filled by our inpainting method based on depth information and texture neighboring pixel values. Our experiment on several multi-view data sets is encouraging in both subjective and objective results. Furthermore, our proposal can flexibly use more than two views in multi-view system to create a new view with higher quality.

Modeling of Transient Thermal Conditions in Cutting

The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green＇s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.

基于油基钻屑制备压裂支撑剂的室内研究

针对热解析后脱油钻屑处理难和处理方式单一的问题,开展了将油基钻屑残渣制备成免烧压裂支撑剂的研究,研究了钻屑与水泥比、CMC添加量、石膏添加量和养护天数共4个因素对免烧压裂支撑剂性能影响。结果表明,在原料配比较优的情况下,制备工艺为钻屑水泥比0.67(质量比),石膏添加量为6%(质量分数),CMC添加量为4%(质量分数),养护时间28 d。该条件下制得的压裂支撑剂颗粒体积密度为1.47 g/cm^(3),视密度为2.52 g/cm^(3),35 MPa下颗粒破碎率为1.57%。经扫描电子显微镜与X射线衍射仪分析发现,此时压裂支撑剂内部结构致密,孔隙封闭,水化产物CaO·SiO_(2)·nH_(2)O凝胶和钙长石类物质有利于提高压裂支撑剂的综合物理性能。为脱油钻屑残渣利用提供新的方向。

石墨烯纸基传感器在人体运动中的实验研究

随着可穿戴技术的飞速发展,柔性传感器因在定制医疗和人机互动中有应用前景而备受瞩目。受剪纸艺术启发,开发了一种新型剪纸结构的柔性纸基传感器。该传感器采用剪纸技术构建的石墨烯纸基材料,能够紧密贴合人体多个部位,旨在探索其在监测生理及运动信号方面的有效性。剪纸结构的设计不仅提高了传感器的敏感度和伸展性,还实现了其与皮肤的高度集成,为人体动态监测开辟了新途径。

负压振动筛原理及在油基钻井液钻屑减量中的应用

经过几十年的发展,振动筛性能有很大提高,但其对钻屑的脱液能力已达极限。40年来,应用于钻井固控,效果不明显。十多年前,经过尝试与高频低幅振动相结合的真空过滤技术应用于钻井固控时,钻屑的脱液能力显著提高,排放钻屑体积大幅减小。近年来,多种负压振动筛在国内钻井中开展了应用试验。经过对常规振动筛复合负压过滤的负压振动筛的原理、主要技术参数、现场应用与国内外类似技术的对比分析及现场应用表明,所使用的负压振动筛的处理量、钻屑含液率、钻屑排放减少量、筛网寿命、能效、设备成本、使用经济效益等都均有明显优势。负压振动筛的应用对节能减排和实现“碳中和”具有重要作用,其逐渐替代常规振动筛,将是钻井固控技术发展的必然趋势。

基于知识图谱的整硬合金铣刀产品知识库构建与应用

由于整体硬质合金铣刀产品数据的内容繁杂、多源异构、表现形式多样,因此需要对其进行知识的组织管理,实现知识集成、共享与重用。首先,对该类刀具产品所含的知识即结构分类信息、切削参数信息、产品全生命周期信息及信息间内在关联进行分析。其次,引入知识图谱构建技术与本体建模理论,通过建立知识本体模型,构建知识图谱。最后,设计并实现整体硬质合金铣刀产品知识库,进行实例验证。便于企业需求用户快速了解及获取刀具产品的切削用量、工艺环境等信息;工艺设计人员选用合理刀具以制定最优加工方案,提升加工效率和保障加工质量。

科研反哺教学在林木育种学教学中的探索与实践

林木育种学是高等农林院校林学专业的一门骨干课程,是以遗传进化理论为指导,研究林木优良品种选育、繁殖原理和技术的学科。其最高目标是选育林木优良品种,为林业生产提供最基本、最优质、最高效的生产资料,是林业的命脉和促进林业产业发展的原动力,在生态文明和美丽中国建设中发挥着越来越重要的作用。为了使学生更容易理解和掌握林木育种学的理论知识,深化科教融合,推进创新型人才培养,完善协同育人机制,在林木育种学授课过程中,通过将理论知识与生产实践相联系,将科技前沿贯穿于课堂教学,并以科研平台辅助实验教学的方式进行教学改革,不仅丰富了教学内容,激发了学生的学习热情,加深了对理论知识的理解,而且还利于学生良好科研素养的培养及创新能力的提高。

急倾斜薄矿体采场围岩及假底应力分布规律研究

急倾斜极薄矿脉是有色、黄金矿山常见的矿体形态,多采用人工假底的留矿法或削壁充填法回采,研究采动过程中围岩和人工假底的受力分布对于设计假底参数和安全开采具有重要意义。以某金矿削壁充填采场为工程背景,模拟研究了人工假底及围岩采动过程中应力变化规律。上、下盘围岩采动后最大主应力和最小主应力减小,回采区域顶板应力集中。假底中心处垂直压力最小,越靠近上、下盘边壁垂直压力增加,随着采高增加,假底各部位的垂直压力增加,最后呈收敛趋势。人工假底主要是剪应力破坏,假底破坏主要是上、下盘高水平应力未作用在同一轴线而产生的剪应力造成的。根据散体侧压力和采动应力变化规律,提出在采场内每隔10m利用混凝土铺底,增加人工假底中混凝土强度及垂直方向的配筋,提高假底抗剪强度,从而提高深部采场回采的安全性和人工假底的稳固性。

CMQL和UEV下Incone1690镍基合金切削力和温度分析

低温微量润滑(CMQL)可以使切削阶段达到更优的切削摩擦性能,提升刀具耐磨性能并获得更优减磨效果;超声椭圆振动(UEV)能够提高难加工合金的切削性能。在超声椭圆振动基础上设置低温微量润滑条件,并通过实验分析其切削效果。研究结果表明:采用UEV和CCMQL模式时,切削力与进给力降低比例依次为62.3%与75.0%,在低温微量润滑过程能够实现更低温度控制效果,有效防止工件的热软化问题。普通切削时温度都接近445℃。UEV可以获得更低温度,同时运用UEV和CMQL处理方式,温度下降了16.1%,采用UEV和CCMQL方式时,温度下降19.5%。通过降低喷嘴角度的方式,获得更低切削雾滴温度,刀尖应力出现降低实现刀具保护,促进刀具寿命延长。该研究有助于改善合金切削工艺,对提高切削质量提供了一个思路。

大理多花山矾扦插繁育技术研究

[目的]研究提高多花山矾(Symplocos ramosissima)插穗生根率和生根质量的方法。[方法]以大理多花山矾枝条为材料,探讨不同生长调节剂、育苗基质对扦插苗生根和移植生长的影响,并筛选出扦插苗苗期适宜基肥施用量,以提高扦插苗移植的成活率。[结果]扦插前将穗条在ABT 400 mg/L+IAA 200 mg/L的混合溶液中浸蘸30 s,可以获得较好的成活率和生根效果。选取66.7%园土+33.3%椰糠混合基质进行移植,可促进多花山矾扦插苗的成活以及生长。适合多花山矾扦插苗的基肥施用最佳方案为复合肥2 g/株+复合生物菌剂1 g/株。[结论]研究得出适宜多花山矾扦插苗成活及生长的生长调节剂、育苗基质及基肥,可为多花山矾苗木生产提供良好的技术支撑。

响应面分析法优化减压热脱附技术处理油基钻屑

采用减压热脱附技术处理油基钻屑,考察了热脱附温度、热脱附时间和系统真空压力对脱油率的影响,在此基础上,采用响应面分析法建立了各因素与脱油率之间关系的数学模型,优化了工艺参数。实验结果表明,在热脱附温度350~450℃、系统真空压力-0.07~-0.09 MPa、热脱附时间60~90 min的条件下,脱油率可达98%以上。各因素对脱油率的影响依次为热脱附温度>系统真空压力>热脱附时间;在热脱附温度420℃、系统真空压力-0.08 MPa、热脱附时间80 min的最佳工艺条件下,平均脱油率为98.67%,与模型计算值(100%)仅相差1.33%,剩余固体的平均含油率为0.37%。回收油的组分与0号柴油基本一致,可用于配制钻井液。剩余固体中未发现重金属元素和放射性元素,能够满足《页岩气勘探开发油基岩屑处理方法及控制指标》(GB/T 41518—2022)中“可用于油气田建设基础材料”的要求。

高速铣削GH4169镍基高温合金切削温度的研究

为了研究GH4169镍基高温合金在高速铣削过程中不同切削用量对切削温度的影响,采用正交试验法对其进行切削仿真,并对铣削加工仿真结果进行分析,得到切削用量与切削温度的关系。为验证仿真结果的合理性和准确性,进行了GH4169镍基高温合金高速铣削加工试验,对比分析高速铣削试验和高速铣削加工仿真的结果,验证GH4169镍基高温合金高速铣削仿真模型的准确合理。在已确定的加工仿真模型基础上进行单因素试验,研究不同切削用量对切削温度的影响。结果表明:在切削速度、每齿进给量和背吃刀量均增大的条件下,铣削温度都逐渐上升,但增长速率呈下降趋势。

Inconel 718镍基高温合金高速切削仿真与刀具磨损机理研究

Inconel 718高温合金因强度高和导热系数低导致其切削加工性较差,采用陶瓷刀具高速切削Inconel 718时存在磨损快、寿命短等问题。通过仿真和试验对比分析,研究切削用量对切削力、切削温度和刀具磨损的影响规律,并获取高速切削过程中刀具前、后刀面温度场和应力场的动态分布规律,为镍基高温合金的高速切削及刀具设计制备提供指导依据。结果表明,切削速度对切削力和切削温度的影响程度小于背吃刀量和进给量;在选择切削参数时,优先选取较高的切削速度;沟槽磨损是抑制陶瓷刀具耐用度的关键因素,主要失效机理是黏结磨损。

车削参数对锆基合金断屑的影响

锆基合金对温度敏感,硬度不高,在粗车过程中存在温度过高、切屑易缠绕的问题。为此搭建车削平台研究锆基合金断屑机理,探究切削速度、进给量对锆基合金断屑情况、切削温度的影响。实验结果表明:提高切削速度对锆基合金断屑的影响较小,但是切削温度会随着切削速度的增加而升高;增大进给量可以显著提高断屑能力并降低切削温度。选用合适的切削参数可以有效改善锆基合金的断屑情况以及控制切削温度。

生物碳化固化水基钻屑作用机理及力学性能研究

钻屑作为油气勘探开发中形成的固废,主要通过水泥进行固化,但水泥生产过程中会形成大量的二氧化碳。因此,需要研究高效、环保的钻屑固化处理方法。生物碳化作为新型松散颗粒加固方法,为钻屑固化处理提供了新思路。生物碳化固化水基钻屑试验表明:固化体强度随含水率、尿素浓度的增加而减小,随活性氧化镁浓度、养护时间的增加而增加。利用相关表征方法分析了水基钻屑固化体中产物种类为玫瑰花状水菱镁石和针状水碳镁石。分析水基钻屑固化体的微观结构,发现产物以连续的碳酸盐网络将水基钻屑固化成连续的固化体,证实了生物碳化固化钻屑的可行性。

表面等离子渗氮对TiAlN涂层TiCN基金属陶瓷性能的影响

针对TiCN基金属陶瓷,调节不同N_(2)/Ar流量比对其进行等离子渗氮,并在渗氮样品表面沉积TiAlN涂层。采用GIXRD、EDS、SEM、HR-TEM、划痕测试、纳米压痕测试和光学图像测试仪等研究了渗氮过程N_(2)/Ar流量比对涂层组织结构、膜基界面状态、力学性能和涂层金属陶瓷刀片切削性能的影响。结果表明,随着N_(2)/Ar流量比的提高,TiAlN涂层晶粒逐渐细化,涂层厚度不断降低,基体表面仍有黏结相残留,进而影响表面涂层的生长和性能。当N_(2)/Ar流量比为1时,膜基界面处存在硬质相生长区和富黏结相生长区两种涂层生长区域,涂层在硬质相表面为共格外延生长,富黏结相区域存在原子排列紊乱的过渡区,涂层为半共格外延生长;涂层(200)晶面取向最强,织构系数为1.91;涂层硬模比(H/E)最高,为0.094。当N_(2)/Ar流量比为2时,TiAlN涂层的硬度和弹性模量均最高,分别为34.15GPa和416.64GPa。在切削加工过程中,切削接触区域主要发生磨粒磨损和粘着磨损。当N_(2)/Ar流量比为1时,涂层TiCN基金属陶瓷刀片切削性能最佳。