Numerical and Experimental Study on Nugget Formation Process in Resistance Spot Welding of Aluminum Alloy

The weld nugget formation in the resistance spot welding(RSW) of aluminum alloy was investigated in the present study. The nugget formation process was directly observed by using a digital high-speed camera. Numerical simulation was also employed to investigate the nugget formation process. The results showed that for the RSW of two aluminum alloy sheets, a nugget was first formed in the workpiece/workpiece(W/W) interface and grew along the radial direction and axial direction of the sheets, and then it became a large elliptical nugget. For the RSW of three aluminum alloy sheets, two small nuggets were firstly formed in two W/W interfaces and grew along the axial direction and radial direction; finally they fused into one nugget. Besides, there existed a critical welding time, after which the nugget size remained nearly unchanged. This indicates that a long welding time is unnecessary for the RSW of aluminum alloy. In addition, the calculated nugget radius was compared with the experimental results, which showed that the simulation results agreed well with the experimental results.

Effects of nugget alloying on microstructures and properties of resistance spot welded joints of aluminum and steel

The resistance spot welding of 6063-T6 aluminum alloy and 16Mn steel was studied by nugget alloying. The results indicated that the Al-steel joint had characteristics of welding-brazing. The nugget zone consisted mainly of α-Al solid solution with dislocations and fine Mg2Si particles. The interface zone had a double-layer structure： Fe2Al5 layer at steel side and Fe4Al13 layer at Al nugget side. The nugget alloying has a significant effect on the joint properties by changing phase composition and refinement of grains. When alloy elements Cu, Zn, Ti and Ni were added, the tensile shear load of Al-steel joints reached 2 780 N, 2 910 N, 2 915 N and 2 929 N respectively, which increased by 24. 1%, 29.9%, 30. 1% and 30. 7% respectively compared with that （2 241 N） of joint without nugget alloying. Therefore, it is an effective way for improving mechanical properties of resistance spot welded Al-steel joints.

Effect of retained austenite and nonmetallic inclusions on the thermal/electrical properties and resistance spot welding nuggets of Si-containing TRIP steels

Five advanced high-strength transformation-induced plasticity(TRIP) steels with different chemical compositions were studied to correlate the retained austenite and nonmetallic inclusion content with their physical properties and the characteristics of the resistance spot welding nuggets. Electrical and thermal properties and equilibrium phases of TRIP steels were predicted using the JMatPro? software. Retained austenite and nonmetallic inclusions were quantified by X-ray diffraction and saturation magnetization techniques. The nonmetallic inclusions were characterized by scanning electron microscopy. The results show that the contents of Si, C, Al, and Mn in TRIP steels increase both the retained austenite and the nonmetallic inclusion contents. We found that nonmetallic inclusions affect the thermal and electrical properties of the TRIP steels and that the differences between these properties tend to result in different cooling rates during the welding process. The results are discussed in terms of the electrical and thermal properties determined from the chemical composition and their impact on the resistance spot welding nuggets.

FEATURE ANALYSIS AND EXTRACTION OF INNER DEFECTS FOR SPOT WELD NUGGET OF ALUMINUM ALLOY

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A New Characterization Approach of Weld Nugget Growth by Real-Time Input Electrical Impedance

The in-process changes of weld nugget growth during the Resistance Spot Welding were investigated based on the resistance of input electrical impedance. To compute the time varying resistance of input electrical impedance, the welding voltage and current signals are measured simultaneously and then converted into complex-valued signals by using Hilbert transform. Comparing with the dynamic contact resistance as reported in literature, it showed that the time varying resistance of input electrical impedance can be accurately correlated with the physical changes of weld nugget growth. Therefore, it can be used to characterize the in-process changes of weld nugget growth. Several new findings were reported based on the investigation of spot welds under no weld, with and without weld expulsion conditions.

An Artificial Neural Network for Estimating Sizes of Spot Welding Nuggets

Sizes of nuggets are often used to evaluate spot weld quality in production. This paper presents a neural estimator used to carry out non-destructive on-line analysis of spot weld quality in which trained ANN functions to map dynamic resistance characteristics into sizes of spot weld nuggets and results confirm the validity of neural network for this type of application.

Evaluation of Nutritional Value and Acceptability of Chicken Nuggets Produced by Chicken Wings and Dehydrated Shellfish

Our study investigated the effect of utilizing chicken wings and dehydrated shellfish to produce chicken nuggets rich in protein, minerals and vitamins. The proximate composition, nutritional value, physical and sensorial properties were evaluated. The differently prepared chicken nuggets were supplemented with dehydrated shellfish CN 0%, CN 2%, CN 4% and CN 6%. There was a significantly reduction in moisture and an increasing in protein content (P < 0.05) in all Chicken Nuggets (CN) in comparison to the control. Fat content was significantly higher in CN 0% than CN 2%, CN 4% and CN 6%. Ash content was increasing with added dehydrated shellfish, while the reduction in carbohydrates and total calories of the different chicken nuggets were noticed with the significant gradual rise in pH values, TBA values showed no significant difference (P < 0.05) between chicken nuggets. Results showed that using dehydrated shellfish in preparing chicken nuggets caused a marked rise in its content of Ca, Fe, Na, K, Zn, Mg and Mn levels, CN 0% had the lowest concentration of all minerals, and had lower values of vitamins A, E and D but CN 6% had higher values of vitamins A, E and D. Control Nuggets (CN 0%) had the lowest value of yellowness and highest value of lightness but CN 6% had the highest value of yellowness and, the lowest value of lightness. The redness had a slightly reduction. All samples showed slight changes in hardness, cohesiveness, springiness, gumminess and chewiness were noticed. An increase in WHC, pick-up, and cooking loss of chicken nuggets with dehydrated shellfish was noticed. Panelists accepted all prepared chicken nuggets and the chicken nuggets CN 4% had the highest score compared with other chicken nuggets prepared.

Small glitches: the role of strange nuggets?

Pulsar glitches, i.e. the sudden spin-ups of pulsars, have been detected for most known pulsars.The mechanism giving rise to this kind of phenomenon is uncertain, although a large data set has been built.In the framework of the starquake model, based on Baym ＆ Pines, the glitch sizes（the relative increases of spin-frequencies during glitches） △Ω/Ω depend on the released energies during glitches, with less released energies corresponding to smaller glitch sizes. On the other hand, as one of the dark matter candidates,our Galaxy might be filled with so called strange nuggets（SNs） which are relics from the early Universe.In this case collisions between pulsars and SNs are inevitable, and these collisions would lead to glitches when enough elastic energy has been accumulated during the spin-down process. The SN-triggered glitches could release less energy, because the accumulated elastic energy would be less than that in the scenario of glitches without SNs. Therefore, if a pulsar is hit frequently by SNs, it would tend to have more small glitches, whose values of ？？/？ are smaller than those in the standard starquake model（with larger amounts of released energy）. Based on the assumption that in our Galaxy the distribution of SNs is similar to that of dark matter, as well as on the glitch data in the ATNF Pulsar Catalogue and Jodrell Bank glitch table, we find that in our Galaxy the incidences of small glitches exhibit tendencies consistent with the collision rates between pulsars and SNs. Further testing of this scenario is expected by detecting more small glitches（e.g.,by the Square Kilometre Array）.

NIKE AIR FORCE III DENVER NUGGETS科罗拉多的彩虹

时光仿佛回到了Alex English带领Denver Nuggets叱诧NBA的年代，Nike将采用当年球衣的配色复刻这双AirForceIII，这也是继夏洛特黄蜂队的AIR FORCE III之后的又一双对昔日经典的献礼之作。这双鞋在色彩方面下足了功夫，鞋面以白色为主，鞋舌上的5彩airforce logo非常醒目，后跟上运用了当时Denver Nuggets队徽上的彩条图案。

Mesabi Nugget成功结束中试着手建设工业厂

Mesabi Nugget项目中试设备测试阶段结束，标志长达20个月的包括工程设计、建设和为期14个月的生产在内的全部活动取得了成功。为了继续推进Itmk3技术的工业化进程，现已开始为霍特伊湖北岸的设计年产能50万t的大型工业演示厂办理环境许可手续，预计建设工作可于2005年4月份开始，2006年后半年就能开始生产，大部分的产能将被动力钢公司消化。另外，

Nuggets用区块链技术 打造无缝安全的电商支付体验

俗话说：凡事都具有两面性.这话在大数据时代讲,一点也不为过.篮球队的教练可以通过采集并分析运动员的身体指标数据来制定更合理的训练计划,以提高团队成绩.另一方面,数据的泄露却给人们的日常生活造成了一些困扰.比如,你今天买了房子,明天可能就有装修公司和家具公司给你打电话进行轰炸式的推销,这样的事例屡见不鲜.

电商支付和身份验证平台Nuggets推出Alpha版本

电商支付和身份验证平台Nuggets,近日向iOS用户开放了其移动应用的Alpha版本。通过使用区块链技术,Nuggets对消费者的个人数据和支付数据进行存储,让消费者完成服务登陆、身份验证和电商支付,且无需再与任何人（包括Nuggets平台）分享个人数据。截至目前,Nuggets已收到了数千名消费者对Alpha版本的试用申请。

Influence of tool pin profile on microstructure and corrosion behaviour of AA2219 Al-Cu alloy friction stir weld nuggets

To overcome the problems of fusion welding of aluminium alloys, the friction stir welding(FSW) is recognized as an alternative joining method to improve the mechanical and corrosion properties. Tool profile is one of the important variables which affect the performance of the FS weld. In the present work, the effect of tool profile on the weld nugget microstructure and pitting corrosion of AA2219 aluminium-copper alloy was studied. FSW of AA2219 alloy was carried out using five profiles, namely conical, square, triangle, pentagon and hexagon. The temperature measurements were made in the region adjacent to the rotating pin. It was observed that the peak temperature is more in hexagonal tool pin compared to the welds produced with other tool pin profiles. It is observed that the extensive deformation experienced at the nugget zone and the evolved microstructure strongly influences the hardness and corrosion properties of the joint during FSW. It was found that the microstructure changes like grain size, misorientation and precipitate dissolution during FSW influence the hardness and corrosion behaviour. Pitting corrosion resistance of friction stir welds of AA2219 was found to be better for hexagon profile tool compared to other profiles, which was attributed to material flow and strengthening precipitate morphology in nugget zone. Higher amount of heat generation in FS welds made with hexagonal profile tool may be the reason for greater dissolution of strengthening precipitates in nugget zone.

Numerical Simulation on Nugget Formation and Evolution in Spot Welding of Aluminum Alloy

With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical simulation.

Comprehensive Utilization of Paigeite Ore Using Iron Nugget Making Process

The feasibility of paigeite ore treatment with iron nugget making process is proved. The isothermal reduc- tion experiments at laboratory scale were carried out, using carbon bearing pellets which were made of boron contai- ning iron concentrate and pulverized coal mainly, from 1 623 to 1 723 K with different heating time. The results indi- cated that iron nugget making process depends mainly on heating time and temperature. And the iron nugget and slag can separate in a clean manner at 1 673 K for 15 min. For the iron nugget, the C content is 3.57% （mass percent） and B is 0. 065~ （mass percent）. The B203 content of slag is 20.01~/00, and the boron was concentrated into one phase which is identified as suanite （Mg2BaOs） during the solidification. With an extraction ratio of 80~ under the atmospheric conditions, the activity of boron in slag is good. The boron-rich slag can be used to extract boric or boric acid and alleviate the shortage of boron resource. Through series of calculation and analysis related, it can be conclu- ded that the recovery ratio of Fe and boron are about 98% and 97% respectively. The results show that this method is feasible and effective on the utilization of paigeite ore.

预干燥对油炸外裹糊鱼块油脂渗透和质构特性的影响

本研究将外裹糊鱼块置于鼓风干燥箱中,40℃干燥3~9 h(3、4.5、6、7.5、9 h)后180℃油炸60 s,分析油炸前后外裹糊鱼块的水分状态、油炸外裹糊鱼块的油脂含量与分布、微观结构及质构特性,模拟油炸过程中油脂的吸收,探讨预干燥对油炸外裹糊鱼块油脂渗透和质构特性的影响。结果显示,油炸后外壳的深层结合水(T21)、弱结合水(T22)和自由水(T23)以及鱼块的结合水(T21)、肌纤维中(T22)和外部(T23)的水分含量均减小。随着干燥时间的延长,油炸后外壳T22峰的起始时间逐渐减小,水分的自由度降低,且T21和T22峰的信号强度减小,结合水向自由水转化;鱼块的T22峰只有干燥9h的发生明显左移;油炸外裹糊鱼块的表面油脂含量和总油脂含量呈减小趋势,表面渗透油脂含量逐渐增加;外壳结构先紧密后粗糙,鱼块表面先光滑后出现裂缝和孔洞;外壳中荧光强度逐渐减弱,苏丹红染色幅度逐渐减小,外壳与鱼块交界处的染色幅度逐渐增大;外壳的硬度和酥性先减小后增大,而鱼块的弹性和咀嚼性呈现相反趋势。这些结果表明,预干燥降低了外裹糊鱼块水分的自由度,改变了油炸外裹糊鱼块的微观结构,从而影响了油脂的渗透和质构特性。本研究可为低脂油炸外裹糊鱼制品的规模化生产提供科学指导和技术支撑。

基于相关性分析和SSA-BP神经网络的铝合金电阻点焊质量预测

基于电阻点焊过程中工艺信号特征,在不同间距、不同间隙和不同间距与间隙3种条件下,引入相关性分析方法分析工艺信号与熔核直径之间的相关性,并建立基于麻雀搜索算法-BP神经网络(sparrow search algorithmback propagation neural network,SSA-BP)的电阻点焊质量预测模型,将功率、焊接电流、焊接电压和动态电阻作为预测模型输入特征.结果表明,经麻雀搜索算法优化后的BP神经网络在测试集上的决定系数R2、均方误差(meansquare error,MSE)、均方根误差(root mean square error,RMSE)和平均绝对误差(mean absolute error,MAE)分别为0.95,1.55,1.24和0.90,均优于BP模型.获得了功率、焊接电流、焊接电压和动态电阻与熔核直径的映射关系,可为焊接的工艺参数设计提供依据.

Inhomogeneity of microstructure and mechanical properties in the nugget of friction stir welded thick 7075 aluminum alloy joints

In this study, 20 mm thick AA7075-T6 alloy plates were joined by friction stir welding. The microstructure and mechanical properties of the nugget zone along the thickness direction from the top to the bottom was investigated. The results showed that the microstructure including the grain size, the degree of dynamic recrystallization, the misorientation angle distribution and the precipitation phase containing its size, type and content exhibited a gradient distribution along the thickness direction. The testing results of mechanical properties of the slices showed that the nugget was gradually weakened along the depth from the top to the bottom. The maximum ultimate tensile strength, yield strength and elongation of the slice in the nugget top-middle are obtained, which are 415 MPa, 255 MPa and 8.1%, respectively.

Nuggets Production by Direct Reduction of High Iron Red Mud

In order to utilize the iron resource effectively in red mud, a laboratory experiment based on the orthogonal method was carried out. Nuggets were gotten by directly reducing the carbon-bearing pellets of red mud and coal. The results showed that the strongest influencing factor is temperature, and the separation between liquid iron and slag is thoroughly. The nuggets can be gotten when the pellets, in which xC/xO is 1.6 and the basicity is 1.0, were maintained in 30 min at 1 400 ℃. The nuggets have a high TFe content which is higher than that in the hot metal produced in BF. It also has a low content of Si and Mn, but a high content of S and P. The main compositions of the slag are amorphous phase mainly containing SiO;and unreduced Fe;SiO;. Of course, a little reduced iron retains in it.

Ca-,Al-rich refractory inclusions and Pt-metal nuggets in the Ningqiang carbonaceous chondrite

Petrography and mineral chemistry of Ca, Al-rich inclusions of Ningqiang carbonaceous chondrite are studied and the highly Re-Os fractionated Pt-metal nuggets in it is discovered. The refractory inclusions are classified into melilite-spinel-rich, and spinel-pyroxene-rich types. The former probably crystallized from melts, while the latter could be aggregates of the nebular condensates. The strong f ractionation between Re and Os suggests a pre-solar origin of the Pt-metal nuggets, which probably experienced various processes of formation and evolution before being captured by the refractory inclusions as indicated by the depletions of W and Mo.