Effects of process parameters on the depth-to-width ratio of flux-cored wire underwater wet welding

The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.

Neuron self-learning PSD control for backside width of weld pool in pulsed GTAW with wire filler

In this paper, the weld pool shape control by intelligent strategy was studied. A neuron self-learning PSD controller for backside width of weld pool in pulsed GTAW with wire filler was designed. The PSD control arithmetic was analyzed, simulating experiment by MATLAB software was done, and the validating experiments on varied heat sink workpiece and varied gap workpiece were successfully implemented. The study results show that the neuron self-learning PSD control method can attain a perfect control effect under different set values and conditions, and is suitable for the welding process with the varied structure and coefficients of control model.

Self-learning fuzzy neural network control for backside width of weld pool in pulsed GTAW with wire filler

The weld pool shape control by intelligent strategy was studied. In order to improve the ability of self-learning and self-adaptation of the ordinary fuzzy control, a self-learning fuzzy neural network controller (FNNC) for backside width of weld pool in pulsed gas tungsten arc welding (GTAW) with wire filler was designed. In FNNC, the fuzzy system was expressed by an equivalence neural network, the membership functions and inference rulers were decided through the learning of the neural network. Then, the FNNC control arithmetic was analyzed, simulating experiment was done, and the validating experiments on varied heat sink workpiece and varied gap workpiece were implemented. The maximum error between the real value and the given one was 0.39mm, the mean error was 0.014mm, and the root-mean-square was 0.14mm. The real backside width was maintained around the given value. The results show that the self-learning fuzzy neural network control strategy can achieve a perfect control effect under different set values and conditions, and is suitable for the welding process with the varied structure and coefficients of control model.

熔融沉积成形中扁平椭圆截面挤压宽度模型的分析与实验

目的在熔融沉积成形工艺中,挤压宽度是一个被忽视的核心参数,它不仅直接影响层高、进料速率、扫描速率等工艺参数,还间接影响打印制件的表面粗糙度、力学性能、尺寸精度和构建时间。因此,必须严格控制挤压宽度。方法首先在3D打印挤出原理、黏弹性理论和聚合物流变学理论的基础上,提出了扁平椭圆截面模型。然后将该模型的理论计算结果与实验测量数据进行比较,验证了扁平椭圆模型的准确性,并分析了误差的来源。同时在该模型的基础上,研究了料丝直径公差对挤压宽度的影响、扫描速率与进料速率的匹配范围和最大扫描速率。结果提出了挤压长丝截面的扁平椭圆模型,得到了理论挤压宽度的表达式,并通过实验验证了该截面模型的误差在6%以内,并研究了料丝直径公差对挤压宽度的影响、扫描速率与进料速率的匹配关系,以及PLA材料在不同层高下的最大扫描速率。结论为提高打印制件品质和效率提供了重要参考。

FDM熔融沉积打印外轮廓收缩率试验研究

基于进一步提高FDM熔融沉积成型精度的问题,采用试验研究的方法,使用直径1.75mm的PLA丝材,利用50mm×50mm×2mm的薄板模型分析并建立了熔融沉积3D打印外轮廓的移动路径与丝材收缩模型,计算出了在分层厚度0.2mm、打印温度210℃、填充料25%的工艺参数下,该材料熔融沉积成型的平均收缩率为0.5047%。最后,通过验证试验,验证了平均收缩率的可行性,为进一步提高复杂零件熔融沉积成型精度提供了数据参考。

Modeling and finite element analysis of rod and wire steel rolling process

Two thermomechanical coupled elastic-plastic finite element （FE） models were developed for predicting the 12-pass continuous rolling process of GCrl 5 rod and wire steel. The distances between stands in the proposed models were set according to the actual values, and the billets were shortened in the models to reduce the calculation time. To keep the continuity of simulation, a technique was developed to transfer temperature data between the meshes of different models in terms of nodal parameters by interpolation functions. The different process variables related to the rolling process, such as temperature, total equivalent plastic strain, equivalent plastic strain rate, and contact friction force, were analyzed. Also, the proposed models were applied to analyze the reason for the occurrence of an excessive spread in width. Meanwhile, it was also utilized to assess the influence of the roll diameter change on the simulated results such as temperature and rolling force. The simulated results of temperature are found to agree well with the measured results.

Magnetization study of ITER-type internal-Sn Nb3Sn superconducting wire

Through magnetization measurement with a SQUID magnetometer the heat treatment optimization of an international thermonuclear experimental reactor （ITER）-type internal-Sn Nb3Sn superconducting wire has been investigated. The irreversibility temperature T^＊ （H）, which is mainly dependent on A15 phase composition, was obtained by a warming and cooling cycle at a fixed field. The hysteresis width △M（H） which reflects the flux pinning situation of the A15 phase is determined by the sweeping of magnetic field at a constant temperature. The results obtained from differently heat-treated samples show that the combination of T^＊ （H） with AM（H） measurement is very effective for optimizing the heat reaction process. The heat treatment condition of the ITER-type wire is optimized at 675℃/128 h, which results in a composition closer to stoichiometric Nb3Sn and a state with best flux pinning.

Effect of wire tension on different output responses during wire electric discharge machining on AISI 304 stainless steel

WEDM is used in machining conductive materials where it is required to obtained complicated and intricate shapes with high accuracy.Various applications are in the field of automobile,medical industries,aerospace etc.WEDM is an economical machining option with short product development cycle.Surface roughness,kerf width,Material removal rate,Recast layer hardness and surface microhardness in WEDM are most important responses.In this paper,effect of varied Wire tension on SR,KW,MRR,RCL hardness and surface microhardness on AISI 304 have been investigated.Pulse on time,pulse off time,current and dielectric fluid are taken as fixed parameter.Results show that Wire tension influences the SR,MRR and Surface microhardness and has no effect on kerf width in case of Stainless steel304.

碳钢在模拟油田采出液中的缝隙腐蚀行为及机理研究

为研究Q235碳钢在不同缝隙宽度和环境温度下的缝隙腐蚀行为和机理,采用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术分别研究了丝束电极的电流密度、极化电阻和腐蚀形貌的差异。结果表明:当缝隙宽度大于0.1 mm时,缝隙腐蚀特征不明显。当缝隙宽度为0.1 mm时,碳钢在25,40,60℃环境下浸泡初期的最大电流密度差值分别为1.24,19.90,7.20μA/cm^(2),浸泡72 h后最大电流密度差值分别仅为浸泡初期的41.9%、4.2%、11.9%。此外缝隙内外均发生电流的极性转换现象,说明Q235碳钢随浸泡时间的延长,逐渐由局部腐蚀向均匀腐蚀转变。升高温度增大了发生缝隙腐蚀的趋势,缝隙外的腐蚀最严重的原因是浸泡时间不够以及溶液电阻降的增加。FeOOH参与阴极反应导致电极由阳极转变为阴极,而金属的溶解反应导致电极阴极向阳极的转换。

PtIr高温合金电火花线切割工艺参数优化研究

为了提高PtIr高温合金电火花线切割加工的表面质量及减少切割边缘毛刺,研究电流、脉宽、脉间距对PtIr合金电火花线切割加工效果的影响。结果表明:加工过程的参数对材料的表面粗糙度及边缘毛刺有重要影响。对电火花线切割加工工艺参数进行了优化,电流为5 A、脉宽5μs、脉距5μs时、加工速度150步/S、钼丝直径0.1 mm时加工效果最佳,表面粗糙度Ra值为0.14μm,切割精度公差可控制在±0.006 mm内。

基于有限元法的大型电力变压器抗短路能力分析

为验证基于有限元法的变压器抗短路能力计算方法的有效性,通过开展变压器基于磁场有限元方法的计算分析,并进行了突发短路试验的220 kV变压器的试验结果和计算结果对比,以及因输电线路短路导致故障的500 kV变压器实际受损部位与计算分析结果对比.由通过了突发短路试验的新变压器与在运变压器的数据对比,分析了变压器低压线圈辐向宽度、所用电磁线尺寸、撑条以及电磁线Rp0 2对变压器抗短路能力的影响.结果表明：通过变压器短路试验的产品在低压线圈辐向宽度增加了10％～22％,其电磁线的子导线尺寸增加了35％～50％.通过此项研究,验证了该分析方法关于绕组机械强度分析的有效性,为新采购变压器的抗短路能力分析评估提供了手段.

气压熔融挤压快速成形材料及成形工艺研究

为了拓宽气压熔融挤压快速成形工艺的应用领域,开发了可应用于气压熔融挤压快速成形的改性石蜡材料,并对成形工艺进行了研究.研究结果表明,改性石蜡熔融挤丝的黏度随硬脂酸镁含量的增加而增大,当挤丝直径增加时,丝径的均匀程度降低,使成丝性能也降低.当硬脂酸镁的质量分数降低至1/10时,材料黏度降低,丝材之间表现出脱黏现象,从而影响了成形性能.实验表明,石蜡与硬脂酸镁的质量比为8∶1,通过建立的熔融挤丝宽度与熔融挤出丝速率、扫描速度和分层厚度之间的数学模型,得到了挤出丝速率、扫描速度和分层厚度相匹配的工艺参数,并验证了挤丝宽度和扫描间距对制件质量的影响.

20钢光纤激光填丝焊工艺与焊缝组织的研究

采用配置送丝系统的数控光纤激光焊接机,对4 mm厚20钢进行激光填丝焊接试验,研究了离焦量、激光功率、焊接与填丝速度等工艺参数对缝宽、熔深的影响,结果表明:合理的工艺参数可以获得深而窄、均匀美观的焊缝;焊后对焊接接头进行金相分析和拉伸试验,研究发现:热影响区组织细小、性能优良,焊缝冷却后出现树枝状魏氏体组织,提高了焊缝的抗拉强度,拉伸断裂位置位于母材,说明获得了力学性能好于母材的焊接接头。

插板式PCB Rogowski线圈的计算与仿真

插板式Rogowski线圈克服了传统Rogowski线圈难以保证绕制密度的缺点,提高了测量精度。鉴于此,提出了一种基于PCB板结构的Rogowski线圈,其二次绕组采用一块基板及若干辅助插板构成。通过理论计算推导及仿真研究,给出了该插板式Rogowski线圈互感、自感、电容等参数的计算方法,并给出了其位置误差、干扰误差、温度误差的计算方法。同时,对该插板式Rogowski线圈的导线宽度、导线间距等物理尺寸对自感、互感各种误差的影响进行了研究。实验结果表明,该Rogowski线圈测量精度能够达到0.5级,具备很强的抗干扰能力和稳定性,且生产工艺简化,对Rogowski线圈在计量及保护领域的推广具有重要意义。

扁钢丝轧制过程中的应变分析

采用304奥氏体不锈钢盘条,研究了将圆截面盘条轧制成扁钢丝的过程中,不同压下量对轧后宽展的影响,分析了材料内部的组织和硬度变化,探讨了轧制中的应变分布。结果表明:本实验条件下,当压下率小于58.9%时,宽展明显并随压下率的变化呈线性关系,变形比较大时,宽展的变化减小;随着压下量的增加,轧后扁钢丝的组织及硬度的变化逐渐均匀,意味着变形逐渐趋于均匀。

配置500MPa钢筋的混凝土梁受弯性能试验

为了研究配置500 MPa钢筋的混凝土梁的受弯性能,对9根矩形截面混凝土梁进行了试验研究.分析了采用500 MPa钢筋的混凝土构件的正截面受弯承载力及使用阶段的裂缝宽度,同时对其中两组配有蒙皮钢筋的梁进行受弯承载力、变形及裂缝宽度的对比分析.试验结果表明,此类构件的受力性能与普通钢筋混凝土受弯构件相同,可按照《混凝土结构设计规范》计算受弯承载力及裂缝宽度,但应对裂缝宽度计算值进行适当修正.同时,蒙皮钢筋的配置能够有效地限制裂缝的发展,使得试验梁在正常使用阶段能够满足裂缝宽度限值要求.

电火花线切割加工中放电间隙大小在线识别

为实现对线切割加工中放电间隙大小的在线识别 ,开发了电火花线切割加工间隙放电状态检测系统。在试验的基础上 ,运用时序分析法研究了放电间隙大小与间隙放电状态之间的关系 ;构造了一个反映放电间隙大小的样本空间 ,并以此训练一个神经网络模型来在线识别放电间隙大小。试验表明 ,该模型能较好地识别放电间隙大小。

集中荷载下高强箍筋混凝土梁的抗剪性能

通过8根集中荷载下高强箍筋混凝土梁的受剪破坏试验,分析了500 MPa箍筋混凝土构件斜截面的剪切承载力及使用阶段的斜裂缝宽度,同时对两组配有蒙皮钢筋的混凝土梁的受剪承载力及斜裂缝宽度进行了对比分析。试验结果表明,此类构件的受力性能与普通钢筋混凝土受剪构件相同,其斜截面受剪承载力仍可按现行《混凝土结构设计规范》有关公式进行计算,并且具有足够的安全储备。同时蒙皮钢筋的配置能够有效地限制裂缝的开展,改善受剪破坏的脆性性能。

高强钢筋混凝土梁裂缝控制试验研究

为研究配置HRB500级钢筋混凝土梁的受弯性能,对12根矩形截面混凝土梁进行了受弯破坏试验。考虑到应用HRB500级钢筋作为受力主筋,可能会导致构件在高应力状态下出现过宽裂缝而不能满足结构适用性和耐久性的要求,提出采用配置蒙皮钢筋以及掺入聚丙烯纤维的方法对裂缝宽度进行控制。分两组对高强钢筋混凝土梁进行受弯承载力、变形及裂缝宽度的对比研究。结果表明:两种配置情况下的混凝土受弯梁的受力特征与普通钢筋混凝土梁相同,聚丙烯纤维的掺入能够提高构件的抗裂能力,而蒙皮钢筋的配置能够有效地减小受弯构件的整体变形。两种方法均能够有效地限制裂缝的开展宽度,使得梁在正常使用阶段能够满足裂缝宽度限值要求,可作为控制构件裂缝宽度的有效措施。

基于漏磁检测的桥梁拉索钢丝损伤评估

为准确评估桥梁拉索中钢丝的损伤面积和断口宽度,提出基于漏磁检测进行损伤定量评估的方法。该方法通过对轴向漏磁信号沿周向积分进行非线性拟合,根据拟合得到的磁荷量、磁荷间距评估钢丝的损伤面积与断口宽度。以?7-61平行钢丝拉索为例,采用ANSYS软件建立三维电磁有限元模型,对钢丝断丝与坑蚀产生的漏磁场进行模拟,分别采用本文方法和传统方法识别损伤特征量,并识别含噪声的漏磁信号以检验该方法的稳定性。结果表明:根据提出的损伤评估方法得到的磁荷量与损伤面积成正比、磁荷间距随断口宽度等量变化,磁荷量和磁荷间距可用来定量识别钢丝的局部损伤;该方法在钢丝损伤定量评估中具有较高的精度和计算效率,且具有较强的抗噪声干扰能力。