A new ellipse fitting method of the minimum differential-mode noise in the atom interference gravimeter

Ellipse fitting is a useful tool to obtain the differential signal of two atom interference gravimeters. The quality standard of ellipse fitting should be the deviation between the true phase and the fitting phase of the interference fringe. In this paper, we present a new algorithm to fit the ellipse. The algorithm is to minimize the differential noise of two interference gravimeters and obtain a more accurate value of the gravity gradient. We have theoretically derived the expression of the differential-mode noise and implemented the ellipse fitting in the program. This new algorithm is also compared with the classical methods.

Experimental Study on the Reduction Effect of Pit Texture on Disassembly Damage for Interference Fit

After remanufacturing disassembly,several kinds of friction damages can be found on the mating surface of interference fit.These damages should be repaired and the cost is closely related to the severity of damages.Inspired by the excellent performance of surface texture in wear reduction,5 shapes of pit array textures are added to the specimens’surface to study their reduction effect of disassembly damage for interference fit.The results of disassembly experiments show that the order of influence of texture parameters on disassembly damage is as follows:equivalent circle diameter of single texture,texture shape and texture surface density.The influence of equivalent circle diameter of single texture and texture shape are obviously more significant than that of texture surface density.The circular texture with a surface density of 30%and a diameter of 100μm shows an excellent disassembly damage reduction effect because of its perfect ability of abrasive particle collection.And the probability of disassembly damage formation and evolution is also relatively small on this kind of textured surface.Besides,the load-carrying capacity of interference fit with the excellent texture is confirmed by load-carrying capacity experiments.The results show that the load-carrying capacity of the excellent texture surface is increased about 40%compared with that of without texture.This research provides a potential approach to reduce disassembly damage for interference fit.

Approach to Interference Riveting Process Control of Aircraft Automatic Drilling and Riveting

Interference fit riveting is an effective way to improve the fatigue life of aircraft.The accurate control of riveting interference of aircraft automatic drilling and riveting equipment is achieved by process parameters including upsetting force and upset head height.It is valuable for aircraft manufacturing engineering.An approach to interference riveting process control based on the analysis of interference riveting stress field is proposed.According to assembly structure,the upsetting force is calculated by the material property and interference fit level,and the upset head height is deduced by the upsetting force.The experimental result shows that the interference fit level can be controlled accurately by the upsetting force and upset head height,and then,the quality of aircraft automatic riveting can be improved.The proposed approach is verified by the good match between the predicted result and the experimental result.

Design principle for parameters and interferences of tungsten carbide insert interface on roller bits

The lifetime of roll-bits with inserted tooth will be obviously decreased while drilling in strata and the tungsten carbide can be integrally separated from the roll-cone,which will need more trip out time to replace the roller bit.This study provides an entire analysis on stress as well as strength for teeth and tooth holes in loaded conditions.Qualities of tooth drop from matrix within roller bit.The optimized interferences of teeth inserted into the bit can be reasonably obtained by the critical interference derived from some relevant influence factors on the tooth-fixing quality of roller bits.

Effects of Prestressing of the Ring Gear in Interference Fit on Flexural Fatigue Strength of Tooth Root

When the gearbox body interference is connected to the ring gear, prestressing occurs in the ring gear, which has a significant impact on the strength and life of the gear. Research on the prestressing of the inner ring gear is in the preliminary stage, and the distribution rule of the prestressing and the influence of each parameter on the interference prestressing have not been derived. In this paper, based on the method of calculating the prestressing of the thick cylinder in interference fit, the ring gear is found to be equivalent to a thick cylinder, and the distribution rule of prestressing of the ring gear in the interference fit is inferred. Then, by modeling and analyzing the gearbox body and ring gear in the interference fit using ABAQUS, the distribution rule of prestressing the ring gear in the interference fit is obtained through a numerical simulation. Finally, the prestressing of the ring gear in the interference fit is measured using X-ray di raction, and the distribution rule of prestressing of the ring gear in the interference fit is obtained through analysis. Compared with the distribution rule of prestressing in theory, numerical simulation, and experiment, the theoretical distribution rule of prestressing is amended through a statistical method, and a more accurate formula of prestressing is obtained. Through the calculation of the stress and bending moment in the dangerous section of the ring gear through prestressing, the formula for checking the tooth root flexural fatigue strength in the interference fit prestressing is inferred. This research proposes a tooth root bending strength conditional formula for the inner ring gear of the interference fit, which serves as a guide for the design and production of the actual interference joint inner ring gear.

Determination of interference fit value on entire roller embedded shapemeter roll

For entire roller embedded shapemeter roll, the relationship between the value of interference fit and the sensor pre-pressure, and the pressure transfer performance of shapemeter roll were analyzed by elasticity theory during the cold reversible rolling process. Considering the influence of strip temperature on the interference fit, the distributions of contact pressure of the framework's top surface and the sensor pre-pressure on different values of interference fit were analyzed by the finite element technology. The results show that the contact pressure of the framework's top surface and the sensor pre-pressure increase with the increase of the value of interference fit. When the value of interference fit is between 0.05 mm and 0.09 mm, roll body's inner hole surface, the framework and pressure magnetic sensitive component don't separate from each other, and the sensor works in the linear segment of characteristic curve, so the normal operation of shapemeter roll is guaranteed.

Simulation on Mechanical Behaviors of Oil-film Bearing Sleeve by Elastic Interference Fit

Oil film bearing,which works on thin film between sleeve and bush,is widely used in steel industry due to the characteristics of high efficiency and low noise,etc. The backup roll of 1 580PC hot strip mill invested by some steel corporation has been equipped with such bearing. During the process of setup&disassembly and usage period,the sleeve has been dramatically damaged,which results in production accidents and decreases its service life,thus heavily influencing steel production. Aimed at such puzzles,under specific loadcase,mechanical properties of bearing sleeve,as well as estimation of contact status and adhesive force of sleeve by interference fit,are quantitatively simulated by finite element method,which establishes an mechanical foundation for improving the load capacity of bearing and decreasing its wear and adhesion damages. Finally,some measures and conclusions are drawn.

The Influence of Centrifugal Force on the Interference Fit of High-Speed Electric Spindle

The letter presents an analysis of interference fit of the electric spindle at different rotor speeds due to the influence of centrifugal force and provides a theoretical formula showing the relationship of the speed, stress on the rotation speed. The letter also established a finite element model of the interference fit. The study found that as the rotation speed increases, the interference and contact stress between the spindle and the rotor gradually decrease, and the reduced speed is proportional to the square of the rotation speed.

Influence of Interference Fit and Surface Roughness on Contact Resistance of Tubing Connections

Within offshore installations, making tubing connections conduct electricity is a developing interest. Being able to use tubing structures to carry the drive power needed downhole avoids installation of cables and lines. The challenge is making the connection good enough with minimum possible power loss. At the same time, the connection has to secure the transfer of the rated power without any danger of overheating. An overheating can eventually result in a welded connection. Previous studies on contact design have mainly focused on low level contact force, while this study aims to find out the influence of surface roughness and connection strength, at macro level, on contact resistance of tubing connections so as to know the power transfer capability of the connection. First, the connection is simplified by ＂rolling out＂ the tubes to flat sheet metals and the voltage drop at rated current was measured at various loads. Then experiment was conducted on contact pairs with two different surface finish qualities and three different contact fits. The results show that smoother surfaces ease the flow of current while high interference fit increases the contact stability. The influence of surface topography becomes insignificantly low at high connection interference.

Flexible,robust,sandwich structure polyimide composite film with alternative MXene and Ag NWs layers for electromagnetic interference shielding

The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.

Design of packing cup interference fit value of hypercompressors for low density polyethylene production

The hypercompressor is one of the core facilities in low density polyethylene production,with a discharge pressure of approximately 300 MPa.A packing cup is the basic unit of cylinder packing,assembled by the interference fit between an inner cup and an outer cup.Because the shrink-fitting prestresses the packing cup,serious design is needed to gain a favorable stress state,for example,a tri-axial compressive stress state.The traditional method of designing the interference fit value for packing cups depends on the shrink-fit theory for thickwalled cylinder subject to internal and external pressure.According to the traditional method,critical points are at the inner radii of the inner and external cup.In this study,the finite element method(FEM)has been implementcd to determine a more accurate stress level of packing cups.Different critical points have been found at the edge of lapped sealing surfaces between two adjacent packing cups.The maximum Von Mises equivalent stress in a packing cup increases after a decline with the rise of the interference fit value.The maximum equivalent stress initially occurs at the bore of the inner cup,then at the edge of lapped mating surfaces,and finally at the bore of the outer cup,as the interference radius increases.The traditional method neglects the influence of axial preloading on the interference mating pressure.As a result,it predicts a lower equivalent stress at the bore of the external cup.A higher interference fit value accepted by the traditional method may not be feasible as it might already make packing cups yield at the edge of mating surfaces or the bore of the external cup.Along with fatigue analysis,the feasible range of interference fit value has been modified by utilizing FEM.The modified range tends to be narrower and safer than the one derived from the traditional method,after getting rid of shrink-fit values that could result in yielding in a real packing cup.

过盈配合工况下收缩管吸能特性分析及结构参数优化

轨道车辆收缩管在轴向冲击载荷及过盈配合下的吸能特性是吸能结构研究中的重要课题,其吸能过程依靠收缩管与锥形衬套之间的摩擦做工及收缩管的塑性变形实现,过盈配合通过影响收缩管与衬套间的接触力提高收缩管的能量耗散。为提高收缩管的吸能特性,研究过盈配合对吸能能力的影响,采用试验与有限元模型相结合的方法,基于多目标优化算法获取包括过盈量在内的收缩管最优结构参数。进行空心轴与轴套过盈静压试验,验证接触力理论公式的正确性;利用台车冲击试验研究收缩管碰撞过程中的吸能特性,构建有限元模型进行验证;推导过盈配合条件下收缩管接触表面压力的理论模型;使用全因子和Hammersley设计方法对过盈配合工况下收缩管结构参数进行研究,包括厚度(T)、过盈量(I_(ntf))、锥角长边(α_(x))和收缩比(R_(atio))。基于此,利用移动最小二乘法(MLSM)构建峰值力(PCF)、比吸能(SEA)和平均力(MCF)的近似模型。主效应分析表明,收缩比对PCF、SEA和MCF的影响最为显著。以获取最小PCF、最大SEA以及MCF最接近设计要求650 kN为优化目标,进行全局响应面(GRSM)优化,获得最优结构配置,与初始设计相比,SEA提高28.54%,PCF降低12.37%。代理模型最优解得出的MCF与有限元模型误差为2.01%,证明构建的代理模型具有较高的精度,可用于优化计算。优化后的结构有效提高了收缩管的吸能能力,降低了碰撞的初始峰值力。

数控压机伺服控制系统复合控制器I-ABC与PID优化

为了提高数控压机伺服控制系统的控制精度,针对伺服控制系统运行控制过程构建数学模型,在人工蜂群算法基础上融入了云分析模型,之后采用改进人工蜂群算法(Improved Artificial Bee Colony,I-ABC)调节比例-积分-微分(Proportional Integral Differential,PID)参数,建立了一种复合控制方法。研究结果表明:以I-ABC进行PID控制时,可以使幅度差降低到0.4%,相位差基本在-0.54°之内,系统加载精度也获得了明显提升,表现出了更优的跟踪性能。以I-ABC进行PID控制时,能够对多余力起到明显抑制作用,响应速度也获得明显提升,可以有效满足系统的准确控制要求。在系统内加入干扰信号,引入I-ABC实施PID调节可以减小系统超调量,还可以获得更短调节时间,使系统获得更强抗干扰性能。

过盈配合织构界面间渗流润滑对拆解损伤的影响

过盈配合件拆解时极易发生摩擦损伤,研究发现在过盈配合界面上添加激光凹坑织构,可显著降低拆解损伤。但由于添加织构的过盈配合界面拆解仍为干摩擦拆解状态,当过盈量过大时,织构化界面仍会形成较严重的拆解损伤。为此,基于岩石渗流原理,文章采用渗流试验将润滑剂引入配合面,实现过盈配合面的润滑拆解,并通过拆解实验分析大过盈量拆解时配合面的损伤情况。结果表明:过盈配合界面上加工出保留熔融层的凹坑织构,在一定渗流条件下可以将润滑油引入配合面中,形成边界润滑或混合润滑状态,且蜂窝织构的渗流效果较为突出;在大过盈量状态下,当接触压力为200 MPa时,有熔融层蜂窝织构干摩擦拆解相较于无织构拆解能够减小拆解损伤,但最大损伤深度仍有76.7μm;而有熔融层蜂窝织构渗流润滑拆解与有熔融层蜂窝织构干摩擦拆解相比,拆解损伤明显降低,可达到无损拆解。

基于RANSAC的圆拟合算法在螺纹孔检测中的应用

在视觉检测过程中,针对多残缺、多噪声圆周的拟合精度不佳的问题,提出了一种基于RANSAC的圆拟合算法。首先对图像进行边缘检测,使用基于Scharr算子的Canny算法可获得高质量的边缘分布图;使用霍夫梯度法在边缘分布图中对目标圆弧进行粗定位,并提取包含目标圆弧的点集;提取到的点集中含有大量无关边缘像素点,使用RANSAC算法剔除点集中的异常数据,得到有效样本数据构成的待拟合圆周点集;最后采用LIN算法对待拟合圆周点集进行拟合,得出最终的拟合结果。算法在椒盐噪声和曲线噪声抗干扰实验中表现优异,有着较强的抗干扰能力。已经成功应用到了螺纹孔圆周的拟合,精度和实时性均可满足实际生产要求。

全陶瓷球轴承最佳原始游隙的研究与分析

游隙对于滚动轴承服役过程中的振动噪声、载荷分布及温升等均有重要影响。为获得适用于全陶瓷球轴承游隙的计算方法,将轴承装配、高速离心效应及热膨胀系数等因素统一为有效过盈量并对轴承游隙进行分析、总结计算公式,同时对氮化硅及轴承钢材料进行拉伸变形计算,研究发现氮化硅材料的延展性为轴承钢的67.7%,以此对过盈量引起游隙变化公式进行优化,并进行轴承装配实验验证优化结果。以7007C氮化硅全陶瓷球轴承为例,计算最佳原始游隙,结果表明在影响轴承径向游隙的因素中,离心效应影响程度最大,其次是轴承装配,再次为热膨胀系数,影响程度最小的为温差;随着转速及载荷的增加,离心效应及热膨胀系数的影响程度在所有影响因素中所占比重也会逐渐增加。

航空插头气动压装机构设计

设计了一种航空插头压装机构,主要由气动压装台、定位装置和定位压装头组成,可实现具有压装方向性要求的航空插头快速压装到工件上,压装过程可确保航空插头不受损坏,且能准确压装到位。该机构的定位压装头设计有特殊的定位、定方向、零件保持等结构,解决了航空插头压装时易受损坏、难定位、难定方向等技术难题,确保了航空插头的顺利装配。

考虑过盈配合的抗侧滚扭杆寿命预测

抗侧滚扭杆用于提供限制车辆侧滚角度的侧滚力矩,可以提升列车运行的平稳性和安全性。文章以某型动车组用抗侧滚扭杆为研究对象,在考虑抗侧滚扭杆的扭杆轴与扭转臂过盈配合的前提下,基于FKM准则对抗侧滚扭杆进行静强度和疲劳寿命评估。结果表明,该抗侧滚扭杆在极限载荷和疲劳载荷工况下的利用度均小于1,同时满足静强度要求和疲劳寿命要求。

压缩机电机的预应力模态分析

模态分析是研究电机振动噪声问题不可或缺的一环,以一台额定功率为1.98 kW的压缩机用永磁电机为例,分析了热应力和过盈应力对电机结构径向各阶模态固有频率的影响。首先分析了绕组以及建模对电机结构模态分析的影响;然后从理论上解析了电机过盈配合量的选取范围,通过热-结构耦合的有限元仿真对压缩机电机温升最高工况时铁心与机壳的热变形大小进行了分析,结合过盈量的选择范围从振动噪声抑制角度选取最佳过盈配合量;最后建立了压缩机预应力模态仿真模型,分析了热应力和过盈应力对压缩机模态固有频率的影响。考虑热应力和过盈应力效应,能够有效地精确计算整机模态,提高空调压缩机NVH性能评估的准确性。

Combined and interactive effects of interference fit and preloads on composite joints

The combined and interactive effects of the bolt-hole fit conditions and the preloads of the fasteners on the load carrying capacity of single-lap composite-to-titanium bolted joints have been investigated both experimentally and numerically. Quasi-static tests of the hybrid joints with different fit conditions are implemented, and a three dimensional finite element progressive failure analysis model is proposed to predict the influences of the bolt-hole fit conditions and fastener＇s pre- loads on the mechanical behaviors of the joints. Based on the experimental validated simulation method, a multi-factor, mixed levels orthogonal design table and the analysis of variance method are used to arrange the simulation conditions and to further study the interactive effects of preloads and fit conditions. Through the analysis of the results, for the researched double bolt, single-lap composite-titanium joints, it is found that： the effects of both the interference fit and the preloads change from positive into negative mode with the increase of the interference fit values or preload values; appropriate bolt-hole fit conditions and preloads can improve the bolt-hole contact conditions of the loaded joints, and then retard the fiber failures around the fastener holes, and increase the load carrying capacity of the joints eventually; the interactive effect of the bolt-hole interference fit conditions and preloads cannot be ignored and the parameters need to be considered together and synthetically as the joints are being optimized.