Mechanical properties and supporting effect of CRLD bolts under static pull test conditions

A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation（CRLD） bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt（rebar） using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson＇s ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson＇s ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.

Microstructure and mechanical properties of friction pull plug welding for2219-T87 aluminum alloy with tungsten inert gas weld

The friction pull plug welding(FPPW)of the 2219-T87 tungsten inert gas(TIG)welded joint was investigated,and the microstructures,precipitate evolution,mechanical properties,and fracture morphologies of this joint were analyzed and discussed.In this study,defectfree joints were obtained using a rotational speed of 7000 r/min,an axial feeding displacement of 12 mm,and an axial force of 20-22 kN.The results indicated that within these welding parameters,metallurgical bonding between the plug and plate is achieved by the formation of recrystallized grains.The microstructural features of the FPPW joint can be divided into different regions,including the heat-affected zone(HAZ),thermomechanically affected zone(TMAZ),recrystallization zone(RZ),heat-affected zone in the TIG weld(TIG-HAZ),and the thermomechanically affected zone in the TIG weld(TIG-TMAZ).In the TIG-TMAZ,the grains were highly deformed and elongated due to the shear and the extrusion that produces the plug during the FPPW process.The main reason for the softening in the TMAZ is determined to be the dissolution ofθ’and coarsening ofθprecipitate particles.In a tensile test,the FPPW joint welded with an axial force of 22 kN showed the highest ultimate tensile strength of 237 MPa.The locations of cracks and factures in the TIG-TMAZ were identified.The fracture morphology of the tensile sample showed good plasticity and toughness of the joints.

prAMD:一种GitHub pull-request协作机制自动设计方法

社会协作编码的开放性使得软件在开发过程中可以汇聚集体智慧。pull-request作为GitHub中开发人员贡献代码的主要方式,若开发人员之间不能有效地沟通协作,整个开发过程就会变得迟缓低效。因此为了提高协作效率,将pull开发模型下开发人员之间的协作过程建模为一种Agent协作模型。结合实际开发过程中开发人员扮演的不同角色,以及各个角色具有的相关特征,基于自动机制设计方法计算得到满足优化目标的协作机制,一定程度上可以更好地促进开发人员协作,提高开发效率。

Motivation Mechanism of Kucong People in Economic Transition

Based on introduction of economic transition of Kucong people, this paper presents two motivation mechanisms, namely, political pulling and economic promotion. For political pulling, it is required to build grass-roots government service system in Zhemi Town and promote economic transition from external side; strengthen leadership of Party Committee of Zhemi Town in grass-roots government; enhance construction of grass-roots government in Zhemi Town; and regulate relationship between grass-roots government and village committee of Zhemi Town. For economic promotion, it is proposed to set up collective producers' cooperatives and promote economic transition of Kucong people from internal side. By taking pilot of Liuliu xinzhai Village production cooperative as an example, it puts forward that new production working cooperatives should be established to solve Kucong people's problem of not good at working separately. It is proposed to cultivate their agricultural activities through collectivization, promote development of its backward productivity, and strive for permanent residence and sustainable development of agriculture on the basis of economic development, finally to realize social development of Kucong people.

空气阻尼对扭臂式静电驱动结构pull-in电压的影响

基于扭臂式静电驱动结构的基本模型,在忽略和考虑空气阻尼作用的两种情况下,分别采用能量法和力电耦合分析方法得到扭臂式静电驱动器的pull-in电压。通过对比两种情况下的pull-in电压,得出了驱动结构参数变化时空气阻尼作用对pull-in电压的影响。结果表明,在一定范围内,随着上电极长度、上电极宽度的增加以及上下电极之间间距的减小,空气阻尼作用对pull-in电压的影响逐步增大;并且当上电极宽度增大或者上下电极之间间距减小到一定程度时,空气阻尼作用力甚至可以与驱动的静电力达到同一数量级,此时必须考虑空气阻尼作用的影响。

带载流导体微机电系统动态Pull-in阈值研究

利用动力系统和微分方程定性理论研究了带载流导体微机电系统动态pull-in阈值。通过对系统轨线的分析,得到该系统集总参数存在唯一的阈值;分析该阈值与系统周期解、pull-in解和趋于平衡态解之间的关系,进一步得到当集总参数超过该阈值时,系统发生动态pull-in。

Sensitivity analysis of pull-in voltage for RF MEMS switch based on modified couple stress theory

An approximate analytical model for calculating the pull-in voltage of a stepped cantilever-type radio frequency （RF） micro electro-mechanical system （MEMS） switch is developed based on the Euler-Bernoulli beam and a modified couple stress theory, and is validated by comparison with the finite element results. The sensitivity functions of the pull-in voltage to the designed parameters are derived based on the proposed model. The sensitivity investigation shows that the pull-in voltage sensitivities increase/decrease nonlinearly with the increases in the designed parameters. For the stepped cantilever beam, there exists a nonzero optimal dimensionless length ratio, where the pull-in voltage is insensitive. The optimal value of the dimensionless length ratio only depends on the dimensionless width ratio, and can be obtained by solving a nonlinear equation. The determination of the designed parameters is discussed, and some recommendations are made for the RF MEMS switch optimization.

新能源汽车PC灯罩的注塑模具设计

针对某款新能源汽车聚碳酸酯(PC)灯罩的结构特点,模具采用一模两腔“L+R”形式的型腔布局。通过对产品成型的CAE分析,模具采用两组针阀式的热流道结构。根据产品外表面局部多处内凹的特征,对定模设计了结构紧凑的“弹块+斜导柱”的脱模结构,并通过机械拉钩机构保证弹块工作的可靠性。由于产品为透明塑件,因此对产品内表面的质量要求也高,又由于其结构较为复杂,产品有多处安装定位特征,对动模采用“斜导柱+滑块+成型块”的联动抽芯结构。在顶出系统方面采用了“方直顶杆+导向块+大顶块”的方式,成功解决产品顶出困难的问题。在冷却系统方面,各个大弹块及大顶块中都设有直径8 mm的独立水路,其余部位设计为直径11.5 mm的水路,将产品包在中间,组成“随形水路”。模具投产后,各抽芯及顶出机构运行平稳,产品各项参数均符合要求,证明各机构设计合理,安全有效。

内牙水管接头的注塑模具设计及CAE仿真

针对一端带有内螺纹和另一端为光孔的水管接头,设计了一套带有齿轮传动+抽芯液压缸的自动脱螺纹机构和斜导柱侧抽芯机构的三板式注塑模具。首先,结合塑件的结构特点,确定了点浇口进胶以及浇口位置和直流循环式的冷却回路,利用模流仿真分析软件moldflow对确定的模流分析模型进行注塑成型工艺过程模拟分析。结果表明,塑料熔体的充填时间、缩痕指数、气穴分布以及翘曲变形量等成型工艺参数都在合理范围之内,验证了浇注系统和冷却系统设计的合理性。其次,对模具结构进行设计,将主分型面取在塑件的轴心面上,其余两个分型面顺序分型实现浇注系统凝料的自动脱落。由于塑件为带内螺纹的管状零件,针对内螺纹脱模难的问题,设计了齿轮传动机构驱动螺纹侧型芯旋转和抽芯液压缸的直线移动的两套运动机构实施自动脱螺纹,塑件光孔部分的成型和抽芯采用斜导柱侧抽芯机构来实现。通过模流分析,验证了模具结构的合理性,并且缩短了模具设计的开发周期,有效地提高了塑件的成型质量。

Nature of the Pull-out System of Carbon Nanorope/Polyethylene Composite and Twisting Effect on Interfacial Behavior

The nature of the pull-out system of carbon nanorope/polyethylene（CNRP/PE） composite is studied by using molecular dynamics approach. The deformation of the CNRP/PE composites in pull-out process is exhibited. The influence of twisting deformation on the interfacial interaction of the composites is investigated. The results show that the energy of the pull-out system is conserved; and the interfacial bonding is weak resulting in a sliding failure of the CNRP inside PE matrix.

Mechanical intestinal obstruction due to isolated diffuse venous malformations in the gastrointestinal tract: A case report and review of literature

BACKGROUND Isolated gastrointestinal venous malformations(GIVMs)are extremely rare congenital developmental abnormalities of the venous vasculature.Because of their asymptomatic nature,the diagnosis is often quite challenging.However,as symptomatic GIVMs have nonspecific clinical manifestations,misdiagnosis is very common.Here,we report a case of isolated diffuse GIVMs inducing mechanical intestinal obstruction.A literature review was also conducted to summarize clinical features,diagnostic points,treatment selections and differential diagnosis in order that doctors may have a comprehensive understanding of this disease.CASE SUMMARY A 50-year-old man presented with recurrent painless gastrointestinal bleeding for two months and failure to pass flatus and defecate with nausea and vomiting for ten days.Digital rectal examination found bright red blood and soft nodular masses 3 cm above the anal verge.Computed tomography showed that part of the descending colon and rectosigmoid colon was thickened with phleboliths in the intestinal wall.Colonoscopy exhibited bluish and reddish multinodular submucosal masses and flat submucosal serpentine vessels.Endoscopic ultrasonography showed anechoic cystic spaces within intestinal wall.The lesions were initially thought to be isolated VMs involving part of the descending colon and rectosigmoid colon.Laparoscopic subtotal proctocolectomy,pullthrough transection and coloanal anastomosis and ileostomy were performed.Histopathology revealed intact mucosa and dilated,thin-walled blood vessels in the submucosa,muscularis,and serosa involving the entire colorectum.The patient recovered with complete symptomatic relief during the 52-mo follow-up period.CONCLUSION The diagnosis of isolated GIVMs is challenging.The information presented here is significant for the diagnosis and management of symptoms.

Analysis of Pull-Out Behaviour of Straight and Hooked End Steel Fibres

The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study presents an empirical description of the axial force required to pull out a hooked end steel fibre from a cementitious matrix. It is based upon consistent experimental tests that show the force versus displacement plot is formed from a sequence of events in which partial and full debonding at the interface is followed by bending of the hook knee to raise the force to its maximum. A loss of peak force occurs with the reversed plasticity involved in a full straightening of the fibre that precedes the rapid sliding to its full removal under a falling force. The stages are assembled in the said order with a piecewise connection between linear segments and a curve of exponential decay. A power law can be introduced to describe the knee bending stage if preferred. The normalised co-ordinates were adopted for the simple mathematical discontinuous function of the full pull-out process. Normalising force and displacement for hooked fibre is based upon the maximum values found for straight fibre pull out. This would apply to an overall embedded length of unity and a unit peak force for a full debonding of straight fibre in similar materials. For hooked fibre the normalised co-ordinates given refer to the initiation and duration of each event to be tabulated at fractions of the embedded length with multiples of that force. Such predictions are seen to be in good agreement with average pull-out response curves.

水下连接器灌胶用保持架冷却水路分析及模具设计

对中空保持架进行了结构分析,获得了模具设计难点。针对设计难点并结合生产实际初步设计了模具水路,将冷却水路设计成正交结构,并进行了模流分析。模流分析结果表明定模水路能较好传导热量;动模区域,热量没有很好的传导至水路区域,冷却水路需进一步优化。将制品最大投影面垂直于Z轴放置,沿制品突变处抽取分型线,得定模成型区及动模成型区。为了降低定模仁制造难度,将部分曲面特征用定模滑块、斜导柱机构成型,同时也有利于定模部分排气;对制品的部分倒扣特征,设计定模斜抽-动模斜顶抽芯机构,有效缩小了模具外形结构,使模具结构更加紧凑。针对中空制品内部所有方向都不能设置自动抽芯的难点,设置整体镶拼抽芯机构;对口部倒扣特征,设置斜顶抽芯机构,倒扣成型件选用铍铜材质,保证了动定模的冷却均衡;设计导热铍铜及法向导热片将集聚在制品内部的热量传导至整个动模,提高了动模冷却水路的冷却效果,并通过结构设计增加了模具的排气性能,避免了制品的局部烧焦。

窄腔内倒扣产品多次顺序抽芯注塑模设计

针对塑件正面窄腔内5个倒扣、背面2个窄腔内环形倒扣、四周侧17个倒扣,背面7个倒扣的结构难点,创新提出了隧道楔紧块、滑块运动方向与侧型芯垂直的吊挂侧型芯式抽芯方法,实现窄腔内倒扣抽芯。设计了4类抽芯机构,通过4次顺序抽芯成功实现窄腔内复杂倒扣产品的脱模。第一次抽芯解决正面窄腔内5个倒扣抽芯难题,由顺序定距分型机构控制抽芯顺序;第二次抽芯解决四周侧17个倒扣抽芯难题;第三次抽芯解决背面7个倒扣抽芯难题;第四次抽芯解决背面2个窄腔内环形倒扣抽芯难题,创新设计了弹簧式快速二次推出机构控制抽芯顺序。经试模验证,该模具结构合理、工作可靠。

汽车左前门板热流道大型薄壁注塑模设计

针对汽车左前门板的尺寸大小、结构特点和工艺要求,设计了一副大型薄壁顺序阀控制的热流道注塑模具。模具喇叭网孔成型零件采用粉末冶金透气钢,有效消除了喇叭网孔中填充不良和熔接痕等成型缺陷。模具采用倾斜式导滑槽,有效解决了倾斜式内侧倒扣脱模难题。模具采用由顺序阀智能技术控制的热流道浇注系统,有效解决了汽车左前门板尺寸大壁厚小熔体填充难题。模具采用快速且均衡温度控制系统,注射周期缩短了约8%,尺寸精度达到了MT3(GB/T 14486—2008)。

倾斜偏心对同步发电机转子力学特性的影响

气隙偏心是一种常见的发电机机械故障。已有研究主要关注正常和轴向气隙均匀偏心对转子受载和振动特性的影响,较少关注轴向气隙非均匀偏心,即转子倾斜偏心。作为补充,全面分析转子倾斜偏心状态下故障程度差异对同步发电机转子力学特性的影响。其中,转子力学特性包括转子不平衡磁拉力激励特性和振动特性。以一台5kVA的两极故障模拟发电机为研究对象,分别进行理论分析、有限元仿真计算和实验验证。结果表明:正常情况下转子不平衡磁拉力为零,转子振动频率以常规基频和定子传递的各偶次谐波为主。在转子发生倾斜偏心故障后,转子不平衡磁拉力/振动以二次谐波为主。随着偏心程度增加,转子不平衡磁拉力/振动的二次谐波幅值将增大。此外,转子不平衡磁拉力沿轴向非均匀分布,在气隙越小的位置不平衡磁拉力越大。

碎纸机收纳桶塑件的注塑模具设计

根据碎纸机收纳桶产品的外形特征与成型要求,设计了一副包括定模隧道滑块油缸抽芯机构、推板带斜顶抽芯机构、斜顶内带司筒和弹针顶出结构的复杂注塑模具。其中,推板带斜顶抽芯机构用于脱出塑件内观面上的两个倒扣,斜顶内带司筒和弹针顶出结构成功解决塑件内部的4个柱子倒扣的脱模问题,设置的定模隧道滑块油缸抽芯机构用于脱出塑件外观面上的倒扣。推板带动斜顶抽芯的同时完成塑件的顶出,在模具结构上省去了顶针板结构。模具在制作调试过程中,各项顶出抽芯机构无干涉,针对塑件成型时易出现的问题,通过进一步的模具结构优化设计加以解决。在模具投入使用后,已生产塑件产品达3万件,塑件尺寸精度及外观质量要求符合预期。

小型电动汽车信号器外壳注射模设计

介绍了电动汽车信号器外壳的注射模设计。塑件成型材料选用科思创PC 2456,采用两板模进行成型。浇注系统中,使用2个扇形冷浇口对模腔进行浇注。塑件注塑工艺参数选定为,喷嘴出口料温为230~250℃;注射速度为200 mm/s;模具温度为80℃;注射时间为1~5 s,注射压力为80~100 MPa;保压时间为5~10 s,保压压力为40~60 MPa;背压为2~4 MPa;冷却时间为10~15 s。模具中,针对塑件外壁、内壁的脱模困难,设置了5个斜导柱滑块机构、1个3次抽芯复合机构、1个中抽式内收先抽芯滑块机构、3个斜顶机构、6个推管机构及多根顶针用于塑件的脱模。其中,3次抽芯复合滑块机构中,3个抽芯滑块组合在一起,先通过第一次开模驱动2个滑块联动抽芯,再通过第二次开模驱动3个滑块同步抽芯和移动,较为妥善地解决了塑件侧槽需二次抽芯脱模难题。模具机构选用恰当,紧凑合理,动作达标;与其它设计方案相比,制造成本约降低减少13%,工作效率约提高5%。

汽车后大灯镜壳大型薄壁精密注塑模设计

根据汽车后大灯镜壳的结构特点,设计了一副大型薄壁精密注塑模具。模具采用定模成型内表面、动模成型外表面及动模侧向抽芯机构,有效地解决了成型塑件脱模困难问题;模具采用三级定位机构,显著提高了模具刚度和寿命;模具采用随形水路温度控制系统,成型周期降低了10%,成型塑件最大变形量下降了20%,成型塑件的尺寸精度达到了设计要求的MT3;模具采用推杆先复位机构,有效地消除了滑块和推杆汽相撞的风险,保证了侧向抽芯机构安全可靠。模具投产后运行平稳,成型塑件尺寸稳定。

矿用无线采集仪外壳双色注塑模具设计

在分析某矿用无线采集仪外壳工艺性能的基础上,采用分体式结构和一模两腔布局,设计了一副定模滑块抽芯的三板式双色模具。为实现此产品的先后两次注射成型,设计了两组不同结构的型腔和两组相同结构的型芯;针对该产品部分外表面位于动模型腔的设计难题,采用定模抽芯的方法将前壳类圆锥外表面的下半部分转为定模型腔成型,设计了定模“弯销+滑块”抽芯结构;针对前壳的型芯较高且根部存在窄缝的情况,将此型芯设计成镶件,节省了高价材料且便于加工。两次注射成型的浇注系统均采用单一点浇口进料的点浇口浇注系统,并利用软件Moldflow2021分析确定了合适浇口的位置,验证了浇注系统设计的合理性,进而可减少修模次数。针对该产品内螺纹倒扣的设计难点,将螺纹型芯设计成活动镶件,即在定模滑块和螺纹型芯内部加工带凸起的六方通孔,用销钉将带凹槽的六方轴固定于滑块,螺纹型芯可通过六方孔套入或抽出六方轴,由此简化了模具结构。该模具已投入生产,其运行顺畅、平稳,生产的双色产品质量良好。