Arc additive manufacturing of gradient hot forging die with shaped waterways

Under the working environment of high temperature and strong load impact,hot forging die is prone to failure which reduces the service life of die.Using arc additive manufacturing in the die cavity,a gradient material hot forging die with high precision,superior per-formance,and conformal cooling channels is developed.This improves the toughness of the die cavity and reduces the working temperature,thereby forming an isothermal field,which is an effective method to enhance the lifespan of the hot forging die.Three kinds of gradient flux-cored wires are designed for the surface of 5CrNiMo steel,and the microstructure and mechanical properties between gradient interfaces were studied.Based on the spatial curved structure of shaped waterways in the hot forging die cavity,a study was conducted on the strategy of partitioned forming for the manufacturing of the die with shaped waterways.In order to avoid interference with the arc gun,the hot for-ging die is divided into four regions,namely the transition region,upper,middle,and lower region,based on a combination of cavity depth and internal U-shaped and quadrilateral structures.The results show that the developed flux-cored wires have good moldability with straight sides of deposited metal under different process parameters and flat surface without cracks,pores and other defects.Under the same working conditions,the life of hot forging die formed by the gradient materials is more than multiple times that of the single material hot forging die,and the temperature gradient field of the shaped waterway die is 7℃/cm smaller than that of traditional straight waterway.

The Origins of the Arc-Shaped Langshan Uplift and Linhe Trench

In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained. This article comprehensively analyzes the research achievements over the past 40 years of geology, geomorphology, seismic exploration, paleogeography, and oil and gas exploration in the Ordos Basin and Langshan. It recognizes that the northern part of the Ordos Basin experienced a meteorite impact in the Late Cretaceous period. The impact pushed the block northwest ward, subducting after colliding with igneous rocks in the north. This sudden event formed a clear arc-shaped mountain zone in the north and a wedge-shaped trench in front of the mountain. The chaotic layers, prolonged and continuous faults, and numerous thrust layers in the Langshan, a negative anomaly area in the center of the northern Ordos, abnormal orientation of crystalline basement structures in the north of Ordos, Moho uplift, and distribution of meteorite fragments in the northwest of Langshan, all of these geological phenomena support the occurrence of the meteorite impact event, forming the arc-shaped Langshan and the Trench.

Tri-Arc双丝焊“Γ”形电弧及其促进方法

Tri-Arc双丝三电弧焊通过中间第3弧的M弧重新分配焊接热输入,实现高熔覆率低热输入焊接.M弧与主电弧耦合,在整个动态周期表现为“Γ”形和“μ”形及其镜像形态.该文研究“Γ”形电弧的形成机理和热输入调控机制,结果表明,“Γ”形态由“μ”形态转变而来,熔滴振荡引起焊丝末端间距的变化,从而促进耦合电弧“Γ”形态的形成,此时M弧不作用于母材,比“μ”形电弧焊接热输入更低.为提高Tri-Arc双丝焊接低热输入效果,在维持导电嘴末端到工件距离不变的前提下,提高焊枪枪体抬升距离从而改变焊丝末端间距.当导电嘴长度由30 mm增加至35 mm时,随着焊枪抬升,“Γ”形电弧作用时间逐渐增加,能更好地促进电弧热分配,降低Tri-Arc双丝焊接热输入,从而降低熔池最高温度,获得更小宽高比和更小熔深的焊缝.

Wave Diffraction on Arc-Shaped Floating Perforated Breakwaters

An analytical method is developed to study the sheltering effects on arc-shaped floating perforated breakwaters. In the process of analysis, the tloating breakwater is assumed to be rigid, thin, vertical, and immovable and located in water with constant depth. The fluid domain is divided into two regions by imaginary interface. The velocity potential in each region is expanded by eigenfunction in the context of linear theory. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations can be obtained to determine the unknown coefficients for eigenfunction expansions. The accuracy of the present model was verified by a comparison with existing results for the case of arc-shaped floating breakwater. Numerical results, in the form of contour maps of the non-dimensional wave amplitude around the breakwater and diffracted wave amplitude at typical sections, are presented for a range of wave and breakwater parameters. Results show that the sheltering effects on the arc-shaped floating perforated breakwater are closely related to the incident wavelength, the draft and the porosity of the breakwater.

Numerical simulations of rip currents off arc-shaped coastlines

The rip currents induced by waves off arc-shaped coastlines are seriously harmful to humans, but understanding of their characteristics is lacking. In this study, the FUNWAVE model was used to calculate the wave-induced currents in the Haller experiment and the ideal arc-shaped coast similar to Sanya Dadonghai, Hainan Province,China. The results showed that the FUNWAVE model has considerable ability to simulate the rip currents, and it was used to further simulate rip currents off arc-shaped coastlines to investigate their characteristics. The rip currents were found to be stronger as the curvature of arc-shaped coastline increased. Coastal beach slope exerts a significant influence on rip currents; in particular, an overly steep or overly mild slope is not conducive to creating rip currents. Furthermore, the rip currents were found to become weaker as the size of arc-shaped coast decreased. When the height and period of waves increase, the strength of rip currents also increases, and, in some cases, wave heights of 0.4 m may produce dangerous rip currents.

Plastic Mechanism of Multi-pass Double-roller Clamping Spinning for Arc-shaped Surface Flange

Compared with the conventional single-roller spinning process, the double-roller clamping spinning（DRCS） process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.

Study on Submerged Upper Arc-Shaped Plate Type Breakwater

Based on the wave radiation and diffraction theory, this paper investigates a new type breakwater with upper arcshaped plate by using the boundary element method(BEM). By comparing with other three designs of plate type breakwater(lower arc-shaped plate, single horizontal plate and double horizontal plate), this new type breakwater has been proved more effective. The wave exiting force, transmission and reflection coefficients are analyzed and discussed. In order to reveal the wave elimination mechanism of this type of breakwater, the velocity field around the breakwater is obtained. It is shown that:(1) The sway exciting force is minimal.(2) When the ratio of the submergence and wave amplitude is 0.05, the wave elimination effect will increase by 50% compared with other three types of breakwater.(3) The obvious backflow is found above the plate in the velocity field analysis.

Numerical simulations of stress wave propagation and attenuation at arc-shaped interface inlayered SiC/Al composite

The effects of interface shape on stress wave distribution and attenuation were investiga- ted using finite element method （ FEM ）. The simulation results indicate that when the stress wave propagates from SiC ceramic to A1 alloy, the tensile stress decreases and the attenuation coefficient of the stress wave increases with increasing central angle of the concave interface between SiC and A1. But for the convex interface, the tensile stress increases and attenuation coefficient decreases with increasing central angle. As the stress wave propagates from A1 alloy to SiC ceramic, the atten- uation coefficient of stress wave decreases with increasing the central angle of the concave interface. For the convex interface, the attenuation coefficient increases with increasing central angle.

Hydrodynamic Performance of the Arc-Shaped Bottom-Mounted Breakwater

The problem of the hydrodynamic interaction with the arc-shaped bottom-mounted breakwaters is investigated theoretically. The breakwater is assumed to be rigid, thin, impermeable and vertically located in a finite water depth. The fluid domain is divided into two sub-regions of inner and outer by an auxiliary circular interface. Linear theory is assumed and the eigenfunction expansion approach is used to determine the wave field. In order to examine the validity of the theoretical model, the analytical solutions are compared to agree well with published results with the same parameters. Numerical results including wave amplitude, surge pressure, and wave force are presented with different model parameters. The major factors including wave parameters, structure configuration, and water depth that affect the surge pressure, wave forces, and wave amplitudes are discussed and illustrated by some graphs and cloud maps.

A DECAGONAL QUASICRYSTAL WITH AN ARC-SHAPED CRACK

A decagonal quasicrystal, which is weakened by an arc-shaped crackpenetrating through the solid in the period direction, and which is subjected to remote uniformphonon stresses, is investigated by applying the complex variable method which is just developed bythe authors. It is found that the phonon and phason stresses near the crack tips exhibit inversesquare root singularities. The four complex stress functions characterizing the phonon and phasonfields are derived. Explicit expressions for the phonon and phason stress intensity factors, crackopening displacements and energy release rate are also presented.

CONTRACTED EFFECT OF BELL-SHADE SHAPE WELDING ARC AND ACCOMPANIED MAGNETIC FIELD WITH SPIRAL PIPE SHAPE

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Modeling the keyhole shape and dimension in plasma arc welding

It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated.

Effect of activating flux on arc shape and arc voltage in tungsten inert gas welding

The effects of activating fluxes on welding arc were investigated. A special set of water-cooling system and stainless steel were used as parent material. During welding process, high-speed camera system and oscillograph were used for capturing instantaneous arc shape and arc voltage respectively. The experimental results indicate that the SiO2 flux can increase the arc voltage, while TiO2 has no this effect on arc voltage. Compared with conventional tungsten inert gas welding (C-TIG), it is found that the arc shape of A-TIG welding used with the SiO2 flux has changed obviously.

Magnetoelectric effect in layered composites with arc shape

Magnetoelectric （ME） layered Ni/PZT/Ni composites with arc shape have been prepared by using electroless deposition. The ME effect is measured by applying both constant and alternating magnetic fields in longitudinal and transverse directions. The longitudinal ME voltage coefficient is much larger than the transverse one. With the increase of arc length or decrease of curvature, the resonance frequency of layered arc Ni/PZT/Ni composites gradually decreases, while the maximum of the ME voltage coefficient of the composites increases monotonously. The influence of the arc length and the curvature on ME coupling is discussed. The flat interface between the ferromagnetic and the piezoelectric phases in layered ME composites is believed to provide large ME voltage coefficient.

Effect of arc force on shape of the welding pool

Based on the three-dimensional model of TIG weld pool established,the effect of the arc force on liquid surface was investigated.The simulation was carried out with finite elements software Surface Evolver.The influence of the arc force on the weld pool shape was also studied.According to the results,the variation of the weld shape and the parameters with different arc force strength was obtained.Compared with the back weld pool,the top weld pool was influenced more strongly by the arc force.These results provide an effective basis for further study of the TIG weld pool.

Effect of Gravity on Arc Shape in GTA Welding-for Low Electric Arc Current

Gas tungsten arc (GTA) welding was performed both in a microgravity environment and in a terrestrial environment,and the arc shapes in both environments were compared. A microgravity condition was obtained using the free fallsystem at the Japan Microgravity Center. The system can maintain a 10 s microgravity of less than 10-5 g. Awater-cooled Cu plate was used to simplify the arc phenomenon. The electric arc current was between 15 and 80 A,and the shielding and atmospheric gas was 99.9995% Ar and its flowing rate was 10 l/min. The polarity was a directcurrent electrode negative (DCEN). The arc gap was 3 mm and careful attention was also paid to the arc gap in boththe terrestrial and microgravity environments being the same. As a result, it was found that no effect of gravity onthe arc shape is observed under general welding conditions (over 60 A). When the electric arc current is lower than25 A, the arc shape is determined by the initial position of the arc root and is constant with time. Accordingly, itcan not be judged whether or not the arc shape is affected by gravity for this range. When the electric arc current isbetween 25 A and 60 A, it is estimated that the arc shape is not affected by gravity though it is occasionally affectedby other minor effects.

Fe-SMA主动加固钢桥面横隔板弧形切口疲劳裂纹实桥应用研究

为确定铁基形状记忆合金(Fe-SMA)主动加固正交异性钢桥面板横隔板弧形切口疲劳裂纹的可行性,以某在役钢箱梁斜拉桥为背景进行实桥加固研究。根据现场横隔板弧形切口的开裂特征,在对裂纹钻孔止裂的基础上,提出利用Fe-SMA材料对横隔板弧形切口裂纹进行粘贴加固的方案,并进行加固施工。通过现场测试得到Fe-SMA板条热激活过程的应变和温度变化,分析Fe-SMA板条和钢板之间的相互作用及加固机理。结果表明:粘贴Fe-SMA板利用Fe-SMA热驱动形状记忆效应可有效便捷地为结构施加预压应力,实现对受损部位的主动加固;经过Fe-SMA联合止裂孔修复后,热驱动作用下的Fe-SMA可以产生200~240 MPa的预拉应力,并在钢板止裂孔边缘施加43~90 MPa的压应力,可有效阻止裂纹进一步扩展;加固体系在加热激活过程完好可靠,当控制一侧加热区域中部温度为200℃时,热传导作用下非加热区域中部的温度为60℃以下,而背面总体温度基本在90℃以下。

CeO_(2)添加量对电弧增材制造铁基形状记忆合金组织和性能的影响

采用粉芯丝材+电弧增材制造技术制备了含不同质量分数(0,1%,2%,3%)CeO_(2)的Fe-14Mn-6Si-9Cr-5Ni铁基形状记忆合金,研究了CeO_(2)添加量对试验合金显微组织和形状记忆性能的影响。结果表明:添加质量分数1%的CeO_(2)后,合金晶内析出相减少,晶界处析出较大尺寸的稀土化合物,组织均匀,弯曲变形后未出现ε马氏体跨晶生长现象,且马氏体交叉状态较少;当CeO_(2)质量分数增加至2%和3%时,晶内析出相增多,分布均匀性变差,且在弯曲变形后ε马氏体跨晶生长和交叉特征增多;随着CeO_(2)添加量增加,试验合金的晶粒尺寸减小,层错概率增大,形状回复率先增大后减小,当CeO_(2)质量分数为1%时晶粒尺寸较小,层错概率较大,形状回复率最大,形状记忆性能最好。

等速节沟道磨削用椭球砂轮设计及优化

为提高等速万向节中星形套椭圆形弧沟道的加工精度,在分析了万向节沟道结构的基础上,提出了一种椭球砂轮磨削星形套沟道的方案,针对此方案,对砂轮尺寸进行了设计计算,初步得到了椭球砂轮的基本尺寸;根据砂轮的实际磨削状态,对砂轮形状进行了结构优化,为验证优化后砂轮形状的正确性,利用UG和VERICUT软件分别对球笼沟道磨床磨削沟道的加工过程和用新型椭球砂轮磨削沟道过程进行了模拟仿真,对比仿真结果,后者误差有所减小,从理论上验证了方案的可行性。

大马鞍形空间曲面自动堆焊技术研究及应用

本文主要研究大马鞍形接管的马鞍面堆焊方法,开展常规堆焊方法的对比分析,利用公司现有设备、装置,将马鞍形焊机、变位机、二氧化碳气体保护焊机等设备进行组合,实现马鞍形接管空间曲面自动气保堆焊,解决了生产中的实际问题,该套装置自动化程度高、堆焊成型良好,在锅炉、石化、核电等普遍存在马鞍面堆焊需求的行业中具有很高的实用价值。