Quality Control on Crimping of Large Diameter Welding Pipe

Crimping is used in production of large diameter submerged-arc welding pipes. Many researches are focused on crimping in certain manufacturing mode of welding pipe. The application scopes of research achievements become limited due to lack of uniformity in theoretical analysis. In order to propose a crimping prediction method in order to control forming quality, the theory model of crimping based on elastic-plastic mechanics is established. The main technical parameters are determined by theoretical analysis, including length of crimping, base radius of punch, terminal angle of punch, base radius of die, terminal angle of die and horizontal distance between punch and die. In addition, a method used to evaluate the forming quality is presented, which investigates the bending angle after springback, forming force, straight edge length and equivalent radius of curvature. In order to investigate the effects of technical parameters on forming quality, a two-dimensional finite element model is established by finite element software ABAQUS. The finite element model is verified in that its shapes error is less than 5% by comparable experiments, which shows that their geometric precision meets demand. The crimping characteristics is obtained, such as the distribution of stress and strain and the changes of forming force, and the relation curves of technical parameters on forming quality are given by simulation analysis. The sensitivity analysis indicates that the effects of length of crimping, technical parameters of punch on forming quality are significant. In particular, the data from simulation analysis are regressed by response surface method （RSM） to establish prediction model. The feasible technical parameters are obtained from the prediction model. This method presented provides a new thought used to design technical parameters of crimping forming and makes a basis for improving crimping forming quality.

STUDIES ON THE CRIMP BEHAVIOR OF SIDE-BY-SIDE BICOMPONENT POLYAMIDE FIBERS

The supermolecular structure and mechanical properties as well as the crimp behavior of theside-by-side polyamide (PA 66-C710) fibers are studied by means of density gradient method,sonic measurement,X-ray,diffractometry,differential scanning calorimetry,crimp tester etc.fortheir as-spun fibers,drawn fibers,and boiling-water treated fibers.The effects of the processingand treatment conditions on the formation of the supermolecular structure and the crimp behaviorof the fibers are investigated and discussed in detail,also the crimp mechanism of the side-by-sidebicomponent fibers is proposed.From these results,it is shown that by adopting suitable spinningfinish,reasonable processing technology and optimal heat treatment conditions the side-by-sidebicomponent polyamide fibers with excellent crimp property,close to that of nylon texturizedstretch yarns,can be obtained.

Effect of Processing Conditions on the Compression Elasticity of Three Dimensional Crimp Staple

The multi-hollow three dimensional(3-D)crimp sta-ple were prepared by the non-symmetrical cooling spin-ning technology.The material properties,spinneret shape,drawing conditions,heat-setting conditions and silicon finishing conditions that influence the compression elasticity of the staple have been investigated.It is found that the compression elasticity of 3-D crimp PET staple is larger than that of 3-D crimp PP staple.The com-pression elasticity of the 5-hollow staple is much

Study on Shrinkage of PEIT Fiber and Latent-crimp of PEIT/PET Conjugate Fiber

The shrinkage behavior of copoiyester fibers (PEIT) and the ’ latent - crimp behavior of side - by - side PET/ PEIT composite fibers have been studied. It is shown that the shrinkage rate, the crimp ratio and the crimp rigidity of these fibers increase with the increasing isoph-thalate content of PEIT and the treatment temperature. The shrinkage in boiling water of the cold - drawn PEIT - A2 fiber appears to be higher than that of PEIT - A3. The shrinkage in dry air of the cold - drawn PEIT - A2 fiber is also higher than that of PEIT at temperature of 393 K or 413K, but lower at 453K. The crimp rigidity of the PET/PEIT - A: conjugate fiber appears to be obviously higher than that of the PET/PEIT - A, conjugate fiber. The mechanism of the shrinkage behavior related these fibers are discussed in detail.

Multi-objective optimization of crimping of large-diameter welding pipe

Crimping is widely adopted in the production of large-diameter submerged-arc welding pipes. Traditionally, designers obtain the technical parameters for crimping from experience or by trial and error through experiments and the finite element(FE) method. However, it is difficult to achieve ideal crimping quality by these approaches. To resolve this issue, crimping parameter design was investigated by multi-objective optimization. Crimping was simulated using the FE code ABAQUS and the FE model was validated experimentally. A welding pipe made of X80 high-strength pipeline steel was considered as a target object and the optimization problem for its crimping was formulated as a mathematical model and crimping was optimized. A response surface method based on the radial basis function was used to construct a surrogate model; the genetic algorithm NSGA-II was adopted to search for Pareto solutions; grey relational analysis was used to determine the most satisfactory solution from the Pareto solutions. The obtained optimal design of parameters shows good agreement with the initial design and remarkably improves the crimping quality. Thus, the results provide an effective approach for improving crimping quality and reducing design times.

Draping Behavior of Carbon Non-Crimp Fabrics and Its Effects on Mechanical Performance of the Hemispherical Composites

In order to investigate the draping behavior of non-crimp fabrics（NCFs）, two types of carbon NCFs with tricot-chain stitches or chain stitches were formed on a hemispherical mould via a stretch forming process. The shear angle and forming defects of the fabrics were measured on the hemisphere, under different blank holder forces（BHFs）. The results showed that increasing BHF could enhance the shear angle slightly, reduce the asymmetry for the deformation of the fabrics, and change the main type of the process-induced defects. Besides, compression tests were performed on the corresponding composite components. By analyzing the change of fiber volume fraction and structural parameters of the textile reinforcements, the effects of draping behavior of NCFs on the mechanical performance of the composites were studied. The results reveal that draping process has distinguishable impacts on the mechanical properties of the final components, which is closely related to the stitching pattern of the NCFs.

Studies on the Structures and Properties of Latent-crimp Copolyester Fibers

The internal causes of latent-crimp were analyzed bystudying the supermolecular structures of the standardpolyester fibers(PET),copolyester fibers(IPET)andtheir side-by-side composite fibers(PET/IPET)inthis paper.It is concluded that IPET and PET/IPEThave better latent-crimp ability because of their asym-metric supermolecular structures.At the same time,they have good dyeability and mechanical properties.Soit is a simple and low cost process to manufacture latent-crimp continuous fibers by melt-spinning of the co-polyester IPET.

冷弯薄壁卷边C形不锈钢梁的力学性能试验

为了研究冷弯壁薄卷边C形钢受弯构件的力学性能,以冷弯薄壁不锈钢梁为研究对象,重点研究加载条件、跨度对构件屈曲模式和受弯承载力的影响。结果发现:试件的加载条件和跨度对冷弯薄壁卷边C形钢受弯构件屈曲模式和极限承载力的影响显著,纯弯加载下的短梁极限承载力高达169.1 kN,破坏模式为畸变屈曲,其余试件破坏模式也为畸变屈曲;腹板V型加劲能够有效抑制腹板鼓曲的产生,提高试件的极限承载力。利用现有直接强度法修正公式的计算结果与试验结果进行对比,以验证公式的准确性。

输电线路压缩型耐张线夹工程失效研究进展

输电线路中耐张线夹需求量巨大,但线夹失效事故发生频繁,这不仅带来了经济损失,还严重威胁到电网的可靠运行。为解释压缩型耐张线夹的失效机理,提高输电线路的安全性,国内外学者展开了大量的研究。从失效事故方面综述了压缩型耐张线夹的过热和断裂两类工程失效类型,从工程分析和机理研究方面综述了两类工程失效类型的失效机理,从压接工艺研究方面综述了压接工艺参数对失效形式的影响,并从常规检测以及无损检测两个角度综述耐张线夹的质量检测研究现状。最后,基于目前偏于定性分析的耐张线夹工程失效研究,对耐张线夹失效机理的进一步研究提出了展望。

一种基于Unity3D技术的电力线路施工仿真系统

为研究电力线路施工耐张线夹压接仿真系统,首先,介绍了耐张线夹压接的基本原理,并讨论了电力线路施工耐张线夹压接仿真项目的实施过程;其次,详细分析了仿真项目的设计过程,包括仿真系统的硬件结构、仿真软件系统的设计和仿真结果的分析;最后,总结了仿真项目的优缺点,并指出仿真项目在电力线路施工中的应用价值。

坑压式压接连接器在航天产品中的应用

概述了坑压式电连接器结构与分类,全面总结了此类电连接的产品检验、工艺装备验收检验、装配工艺流程以及检验手段,并对装配过程中的常见质量问题及预防措施进行了论述。

架空导线压接对边距的图像测量方法

压接导线主要应用于架空线路建设,其对边距对线路安全运行及服役期限起到重要作用。针对传统人工测量存在的可靠性差、效率低的缺点,提出了一种基于图像处理的压接对边距测量方法。首先根据图像的累计灰度突变点自动裁剪被测区域并进行中值滤波,然后基于改进Otsu阈值法获得边缘连续的二值图像;再分别使用形态学处理和高斯曲线拟合法对边缘进行二次定位,得到亚像素级边缘点;最后采用基于随机抽样一致性(random sample consensus, RANSAC)的最小二乘拟合方法完成上下边缘点的曲线拟合,实现压接对边距的测量。通过模拟试验表明了RANSAC拟合经过10次迭代后测量算法的效果较好,测量误差小于0.1 pixels;而实际导线测量试验结果表明,改进Otsu算法对光照强度具有适应性,同时与人工测量相比,图像测量方法的最大相对偏差为1.82%,重复标准差提高60%,平均耗时仅为人工测量的1/10,能够实现压接对边距高效可靠的测量。

面向高速集成VPX架构的航天产品工艺技术验证及应用

针对高速集成VPX架构的航天产品研制需求,开展了VPX压接连接器的选用必要性分析、特点介绍、鱼眼端子结构设计和合理的PCB工艺方案设计,完成了高速集成VPX架构的工艺控制流程,开展了PCB孔径尺寸验证、连接器接触阻抗验证、连接器试验样品补充50次插拔试验、结构样机的试验验证和在轨应用验证等工作,结果表明:采用文章所述的PCB工艺方案和VPX架构的工艺控制流程,成功研制并在轨应用了某星载高速集成VPX架构数传智能处理器,充分验证了VPX压接连接器可以满足星载高可靠要求。未来,采用更高速率的VPX压接连接器,通过合理的航天产品工艺方案,研制更高速度和更高集成度的航天产品,进一步提升产品的功能性能。

电机刷架组件的电流线端接工艺改进

刷架组件电流线端采用焊接-压接工艺进行连接,受到原料及工艺参数的影响,合格率不稳定,且操作流程繁冗。采用模压式压接工艺,对工艺过程中的压接参数进行分析及改进,优化参数,有效缩短加工时间,提升压接后的产品质量及效率。

基于磁膜包覆技术的碳纤维复合芯压接缺陷漏磁检测方法研究

双碳背景下,碳纤维复合芯导线具有环保、节能特性,有着良好的应用前景,但其芯棒较脆且不耐弯折,针对钢锚处压接部位质量检测暂无行之有效的方法,严重制约着该技术在输变电工程中的推广。为此,以横截面积为40 mm 2的碳纤维复合芯导线及耐张段压接金具为研究对象,通过磁性薄膜包覆的方式,提出了一种基于漏磁法的碳纤维芯棒压接缺陷检测方案。首先,构建了磁膜包覆后压接金具漏磁场分析模型,探究了漏磁装置的磁极间距L、径向气隙λ、探测靴深度h和宽度d在断裂和少压两种缺陷工况下对信噪比的影响,得出L=55 mm、λ=3.5 mm、h=7 mm、d=12 mm时,信噪比效果较好。在此基础上,通过增大断裂尺寸和少压程度,得出断裂漏磁场轴向分量呈现单峰值,径向分量呈现双峰值,而少压轴向和径向分量与之相反。最后,结合试验结果验证了所提出方案的可行性。结果表明:磁性薄膜具备反映碳纤维芯缺陷状态的能力;试验中发现,缺陷信号形态学特征体现为倒“V”形,与理论分析相符。研究成果可为碳纤维复合芯棒钢锚处压接质量检测提供一种新思路。

铝合金电缆压接有限元分析及压蠕变试验研究

采用ABAQUS软件,通过有限元法模拟了常用标称截面为240 mm^(2)铝合金电力电缆导线压接接头处导线表面的应力和应变。模拟结果表明:在连接管与电缆导体间隙为1.0 mm~1.7 mm范围内,压接电缆导线表面的残留应力在压接范围内呈非均匀分布,以中间截面为中心,距离中心约20 mm处残留应力较大,最大值约50 MPa;距离中心20 mm~42 mm处残留应力较小,连接管端部5 mm范围内残留应力又变大。随着间隙由1.0 mm增大至1.7 mm,压接导线的轴向延展应变量由12.62%降至3.12%。以模拟获得的最大应力50 MPa和运行温度90℃为蠕变实验参数,将与铝合金绞线相同退火状态的压缩蠕变试样按模拟应变量进行预压缩后进行压缩蠕变实验,实验结果表明:退火导线经压接变形后,蠕变变形量减小,第二阶段蠕变速率降低,且预变形量越大,第二阶段蠕变速率越低。

Influence of feeding crimped kernel maize silage on the course of subclinical necrotic enteritis in a broiler disease model

This experiment was carried out with 375 male broilers(Ross 308) from days 1 to 28 to evaluate the influence of crimped kernel maize silage(CKMS) on the manifestation of subclinical necrotic enteritis,microbiota counts, organic acid production and relative weights of gastrointestinal segments. A necrotic enteritis disease model was applied. Birds were allocated into 3 different dietary treatments: a maizebased feed(MBF, control diet), and 2 diets supplemented with 15%(CKMS15) or 30%(CKMS30) of crimped ensiled kernel maize. The disease model involved a 10-time overdose of an attenuated live vaccine against coccidiosis given orally on day 17, followed by oral inoculation of Clostridium perfringens Type A(S48,10~8 to 10~9 bacteria/bird) twice daily on days 18,19, 20 and 21. Scoring of intestinal lesions was performed on days 22, 23, 25 and 28. Ileal and caecal digesta samples were collected for the quantification of selected bacterial groups and organic acids. The results showed that there was no effect of dietary treatments on small intestinal lesion scores(P> 0.05). Lesions scores peaked on days 23 and 25 and decreased again on day 28(P = 0.001). No effect of age on microbiota counts was observed, but feeding of CKMS30 reduced the number of coliforms in ileal contents(P = 0.01). Dietary treatments did not affect organic acid concentrations in ileum and caeca, but there was an effect of age; butyric acid was higher on days 22, 23 and 25 than on day 28(P = 0.04). Acetic acid and propionic acid concentrations in caeca were the highest on days 22 and 28 but the lowest on days 23 and 25. Relative gizzard and caeca weights were increased, and relative ileum weights were decreased when birds were fed CKMS30(P < 0.05). In conclusion, the inclusion of CKMS in broiler diets had no effects on the course of necrotic enteritis but had potential benefits in terms of inhibition of potentially harmful microorganisms.

Crimped nanofiber scaffold mimicking tendon-to-bone interface for fatty-infiltrated massive rotator cuff repair

Electrospun fibers,with proven ability to promote tissue regeneration,are widely being explored for rotator cuff repairing.However,without post treatment,the microstructure of the electrospun scaffold is vastly different from that of natural extracellular matrix(ECM).Moreover,during mechanical loading,the nanofibers slip that hampers the proliferation and differentiation of migrating stem cells.Here,electrospun nanofiber scaffolds,with crimped nanofibers and welded joints to biomimic the intricate natural microstructure of tendon-to-bone insertion,were prepared using poly(ester-urethane)urea and gelatin via electrospinning and double crosslinking by a multi-bonding network densification strategy.The crimped nanofiber scaffold(CNS)features bionic tensile stress and induces chondrogenic differentiation,laying credible basis for in vivo experimentation.After repairing a rabbit massive rotator cuff tear using a CNS for 3 months,the continuous translational tendon-to-bone interface was fully regenerated,and fatty infiltration was simultaneously inhibited.Instead of micro-CT,μCT was employed to visualize the integrity and intricateness of the three-dimensional microstructure of the CNS-induced-healed tendon-to-bone interface at an ultra-high resolution of less than 1μm.This study sheds light on the correlation between nanofiber post treatment and massive rotator cuff repair and provides a general strategy for crimped nanofiber preparation and tendon-to-bone interface imaging characterization.

背对式槽钢组合梁均布荷载下的弯曲应力研究

研究了均布荷载作用下的冷弯薄壁背对式组合梁的弯曲应力分布,基于梁的经典弯曲理论和约束扭转理论,在考虑翘曲作用的影响下推导了构件在均布荷载作用下的弯曲应力理论公式。并通过有限元软件ABAQUS分析算例,将算例的仿真值和理论解析值进行对比,验证了该理论公式的合理性。结果表明,弯曲应力在横截面上呈现线性梯度分布,以构件OT1.2-86-S75为例,当旋转约束k_(φ)取值分别为10、100、1000 N时,翼缘处的应力梯度分别为3.225、2.465、1.732 MPa/mm,即翼缘处的应力梯度随着旋转约束的减小而增大;沿纵向在相邻螺钉之间呈现连续抛物线式分布;若螺钉间距相等,弯曲应力最大值出现在跨中,弯曲应力极大值随着与支座距离减小逐渐递减。

基于3σ准则与图像识别技术的压接测试方案应用探究

压接高速连接器使用越来越多且引脚朝着细、短、软、薄方向发展,对压接工艺要求越来越高,但缺乏有效的管控方法,导致故障泄露到整机甚至外场,影响恶劣。文章提出一种基于3σ准则与图像识别技术结合的智能管控方案,该方案通过对行程曲线工艺特征,利用图像相似度像素方差特征方法检测异常压接问题,并利用3σ准则对过程参数进行识别管控,解决压接质量管控依赖人员判定,跪针、压接不到位无法识别等问题。