Influence of the press ram motion on the joining characteristics during indentation plastic joining using a servo press

A plastic joining method for fixing bars and hot plates, called “indentation plastic joining”, was carried out using a servo press with press ram speed control. The influence of the press ram motion control on the indentation joining characteristics of an aluminum alloy bar and plate was examined. The accelerated ram motion was effective in reducing the bar indentation pressure by approximately 15% and the bonding strength of the indented bar–plate was improved by approximately 7%. The bonding mechanism underlying the indention joining method under press ram motion control is discussed in terms of the seizure of the plate and the mechanical clamping associated with the process. It is found that the accelerated ram motion produces heavier seizure at the indented bar–plate interface, whereas the decelerated ram motion reduces the degree of the seizure.     

Hybrid joining process for carbon fiber reinforced thermosetting plastic and metallic thin sheets by chemical bonding and plastic deformation

A new joining process for thin metallic and continuous carbon fiber reinforced thermosetting plastic (CFRP) sheets is proposed. This joining process is a hybrid of chemical bonding and plastic deformation, usable for ultra-lightweight structures. In contrast to conventional joining methods, such as rivet joining with an adhesive, the proposed method does not require any additional components and can eliminate holes that would cut the continuous carbon fibers and cause stress concentration. Hence, a smaller weight and a higher joining quality can be attained, especially for thin sheets. Aiming at making comparison and demonstrating the applicability of the proposed hybrid joining method, two thermosetting CFRP sheets with different laminates were used as lap adherends in the experiment. The effects of the deformation temperature, the use of a dummy sheet and the relative positions of the sample and dummy sheet on the joining quality were systematically investigated and optimized. The optimal hybrid joint shows high-quality bonding without delamination or adhesive failure. The tensile shear test of single-lap A2017P-CFRP hybrid joints manufactured under optimal experimental conditions indicates that, compared with adhesive bonding and conventional rivet joining with an adhesive, the proposed joining method has obvious superiority in terms of tensile shear load, slip displacement and absorption energy.     

Laser direct joining between stainless steel and polyethylene terephthalate plastic and reliability evaluation of joints

Metals and plastics have been widely used in industrial applications, and joining of a metal to a plastic is necessary and important from a manufacturing viewpoint. Therefore, we have developed laser-assisted metal and plastic (LAMP) joining as an innovative rapid laser direct joining without adhesives or glues. In this research, the joining between a Type 304 stainless steel plate of 3 mm thickness and a polyethylene terephthalate (PET) plastic sheet of 2 mm thickness was exploited at several travelling speeds with a diode laser beam of line profile at 170 W power. The joints of 30 mm in width possessed extremely strong tensile shear loads of approximately 3000 N at the maximum. Transmission electron microscope photographs of the joints demonstrated that Type 304 and PET were bonded together on the atomic or molecular level through a Cr oxide film of stainless steel. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analysis indicated the possibility of chemical bonding between hydrocarbon and metal through oxygen. Concerning reliability evaluation for the LAMP joints, some joints could have high shear tensile loads of approximately 3000 N even after heat cycle test and show superior air-tightness in helium leak test. Consequently, it was confirmed that the LAMP joining of SUS304 and PET plates could produce a sound joint of high strength, nanostructural binding through the oxide film and fundamental reliability for practical use.     

Modelling of deformation and failure of crash toughened adhesive bonded lap shear joints

Abstract

With an increase in the use of advanced high strength steels in vehicle architectures, materials joining issues have become increasingly important. Among the various joining methods, adhesive bonding is increasingly used in automobile manufacturing. Successful implementation of adhesive bonding to improve structural crashworthiness and reduce vehicle weight requires the knowledge of issues related not only to processing but also to joint performance. In this study, a new anisotropic yield criterion which is determined from tensile and shear tests, is developed and incorporated into a finite element model to predict the static load displacement curves of various adhesive bonded steel joints. In the developed model, when the calculated plastic strain of bonded steel joint reaches the equivalent plastic strain of the adhesive the joint is regarded as failed. Modelling results have been validated by the experimental data. Since the model covers different steel grades, gages, and overlap distances, the model can be used to predict the static strengths of adhesive bonded assemblies. Finally, the model is employed to evaluate the effect dissimilar steel grades and sheet gages on the joint strength of lap shear bonded steel joints. The results show that for the joints made of dissimilar steel grade and sheet gage, the stiffness (i.e. strength and thickness) of the two adherends should be balanced to obtain the optimum joint strength.     

Mechanical relationship in steel-aluminum solid to liquid bonding

1　INTRODUCTIONThecurrentproductsofsolidsteelplatetoliquidaluminumincludehot dipaluminizingsteelplate[1,2 ]andsteel aluminumsolidtoliquidbondingplatemain ly[3,4 ] .Theyarewidelyusedinornament ,machin ery ,automobileandnavigationfield .Fortheseprod ucts ,theinterfacialmechanicalpropertyiscrucial;itdeterminesthequalityandapplicationoftheseprod ucts .Thelargertheinterfacialmechanicalproperty ,thewidertheapplicationoftheproduct .Theinterfacialmechanicalpropertyisdeter minedbyinterfacialstruct…     

钢—半固态铝熔体压力复合板的界面力学性能与结构

采用压力复合方法实现了钢半固态铝熔体复合, 对复合板的界面剪切力学性能和界面结构进行了研究, 确定了半固态铝熔体固相率与复合板界面剪切强度之间的关系以及钢半固态铝熔体复合板的界面结构。结果表明： 铝熔体固相率为３２ ．２ ％ 时, 复合板界面剪切强度最大, 为６９ ．７ ＭＰａ , 其界面是由铁铝化合物和铁铝固溶体交替构成的新型结构。     

The preparation and property research of the stainless steel/iron scrap clad plate

As an attempt to recycle iron scraps, a new method is proposed to produce stainless steel clad plate by hot rolling. Iron scraps (Q195) were cold pressed into stainless steel pipe (304), and were subsequently hot rolled to produce composite clad plates at 1250 °C. Experiments showed that the iron scraps could be compressed into solid steel and joined well with the outer stainless steel surface using the proposed method. The shear strength of the bimetallic interface formed is about 273 MPa after seven pass rolling. The clad plates produced show good bending ductility. Element diffusion occurred at the interface during the hot rolling processes. The peak hardness appears in the vicinity of the interface due to the severe plastic deformation under high temperature and pressure during the rolling processes.     

Dynamic characteristics of adhesive bonded high strength steel joints

Abstract

With an increase in the use of advanced high strength steels in vehicle architectures, materials joining issues have become increasingly important. Among the various joining methods, adhesive bonding is increasingly used in automobile manufacturing. Successful implementation of adhesive bonding to improve structural crashworthiness and reduce vehicle weight requires the knowledge of issues related not only to processing but also to joint performance. In this study, the impact strength of adhesive bonded high strength steel joints is evaluated with the split Hopkinson tension bar (SHTB) technique. The influences of loading speed and thickness of the steels on the shear strength of the joints were examined. Comparative quasi-static lap shear tests were also conducted on a tensile testing machine. Test results showed that strength and energy absorption of bonded steel joints increase with loading speed, and is greatly affected by the thickness of the steels. As the loading rates are increased to 1100 s^–1 (i.e. 20 m s^–1), bonded 0·75 mm thick DP600 steel shows a 152% increase in strength and an 83% increase in energy absorption when compared to its quasi-static values. Examination of the impact tested specimens showed the failure mode changes from coarse cohesive mode to fine cohesive mode with increasing loading speed. The results from this study will provide the information for a better understanding of impact failure mechanisms of adhesive bonded high strength steels.     

Laser brazing of a dissimilar joint of austenitic stainless steel and pure copper

In many industries, there are applications that require the joining of stainless steel and copper components; therefore, the welding of dissimilar stainless steel/copper joints is a common process. For this investigation, the optimal brazing conditions and suitable filler metals for laser brazing of stainless steel/copper lap joints were studied. Tensile shear force increases with increases in the laser spot diameter or in the laser irradiation angle, which is associated with increased bonding width; however, as bonding width approaches 2 mm, tensile shear force reaches a saturated value due to fracturing at the HAZ of the Cu base plate. In order to obtain joints with high tensile shear strength, laser brazing was optimized by using Cu–Si-based filler metal under the following conditions: laser power, 4 kW; spot diameter, 3 mm; laser irradiation angle, 80°; irradiation position shift, 0.6 mm; brazing speed, 0.30 m/min; and filler metal feed speed, 0.30 min. Concerning filler metals, it was found that the Ni–Cu type showed relatively large tensile shear force even at high welding speeds in comparison with those of the Cu–Si, Cu, Cu–Ni, Ni–Cu and Ni types, respectively.     

爆炸焊接法制备铟/铁复合板的实验与数值模拟

提出了一种通过在炸药与复合板之间增加一层速度调整板，以获得理想焊接条件的用于制备铟/铁复合板的新型爆炸焊接方法。通过理论方法计算了爆炸焊接参数，通过实验对炸药载荷的影响进行了研究。应用光滑粒子流体动力学（SPH）方法进行数值模拟以验证参数有效性，探究了结合界面的成型机理，并研究了压力和塑性应变的分布。结果表明，当炸药厚度增加时，界面波形结构更明显。界面剪切试验结果表明铟/铁复合板结合面抗剪切强度为16 MPa，比纯铟材料的抗剪切强度高，且三点弯曲试验之后复合板结合界面无裂纹。采用改进的爆炸焊接方法可以有效制备高质量铟/铁复合板。     

Effect of solid fraction on steel-mushy Cu-graphite pressing bonding

The pressing bonding of steel plate to QTi3.5-3.5graphite slurry was studied. The bonding conditions were 620℃ for preheating temperature of steel plate, 530℃ for preheating temperature of dies, 50 MPa for pressure and 2 min for pressing time. The relationship between the solid fraction of QTi3.5-3.5graphite slurry and the interracial mechanical property of bonding plate was obtained. The results show that when the solid fraction of QTi3.5-3.5graphite slurry is smaller than 45.8%, the interracial shear strength of bonding plate increases with the increasing of solid fraction. When the solid fraction is larger than 45.8%, the interracial shear strength decreases with the increasing of solid fraction. When the solid fraction is 45.8%, the largest interracial shear strength of bonding plate 127 MPa can be got, and the interface is made up of Fe-Cu solid solution.     

Bonding Mechanisms and Shear Properties of Alumina Ceramic/Stainless Steel Brazed Joint

Al₂O₃ ceramic/stainless steel joints were fabricated by activated molybdenum-manganese (Mo-Mn) sintering metallization plus vacuum brazing using Ag-28 wt.% Cu alloy. The bonding mechanisms including metallization and interfacial bonding were analyzed and discussed by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). Tests were also carried out to examine the influence of brazing on joint shear strength. The metallization mechanisms of glassy phase migration and chemical reaction were confirmed experimentally, while Ni coating was found to play a key role in the joining of metallized ceramic to metal via the Ag-Cu filler layer. As a result of the joining, the average shear strength of the joints exceeds 95 MPa, with the maximum reaching 110 MPa.     

Effect of rolling on interfacial property of steel/mushy Al-20Sn bonding plate

1　INTRODUCTIONSteel/Al 2 0Snbondingplateisidealmaterialforneotypebearing[1] .Itiswidelyusedinthefieldssuchasmachinery ,automobile ,etc[2 5] .Forthisbondingplate ,twothingsareveryimportant.Oneisthedis tributionofSnparticlesinAl 2 0Snlayer ,theotheristheinterfacialshearstrength .Theformerdeterminesthelifeofbonding plate .Thelatterdeterminesthesafetyofbondingplate .TheevenerthedistributionofSnparticlesinAl 2 0Snlayer ,thelongertheusagelifeofbondingplate .Thelargertheinterfacialshearstr…     

Effect of Interlayers on Microstructure and Properties of 2205/Q235B Duplex Stainless Steel Clad Plate

In this research,2205/Q235 B clad plates were prepared by a vacuum hot rolling composite process.The effects of adding Fe,Ni,and Nb interlayers on the bonding interface structures and the shear strengths of the clad steel plates were studied.The results showed that 2205 duplex stainless steel and the three interlayers produced a large amount of plastic deformation and low-angle boundaries,and the main structures were the recrystallized and deformed grains.There were many recrystallized grains in the microstructure of the Q235 B low-carbon steel due to the low deformation in the rolling process.The Fe interlayer had better wettability with the two kinds of steel,but the lower strength led to the reduction of shear strength by about14 MPa compared with the original clad steel plate.The C element in the Q235 B low-carbon steel easily diffused into the Fe interlayer,and the clad steel plate attained a poor corrosion resistance because a large decarburization area was formed.The Nb interlayer reacted with the Mo element in the 2205 duplex stainless steel to form an Nb-Mo binary alloy,which generated long-banded ferrite.The decarburization area was also produced because the Nb reacted with the C element in the Q235 B to form hard and brittle NbCx.As a result,the shear strength was significantly reduced by about 282 MPa,and the corrosion resistance of the bonding surface was deteriorated.The Ni interlayer did not react with the alloy elements in both sides,and therefore effectively prevented element diffusion and improved the corrosion resistance of the bonding surface.Due to the low strength of the Ni interlayer and the increased number of bonding surfaces of the clad steel plates,the shear strength was reduced to some extent(about 40 MPa),but it still met the engineering application standards.     

铝合金与钢的点连接技术

介绍了铝合金与钢的点连接技术的研究现状,主要分析了工艺垫片法电阻点焊、搅拌摩擦点焊和超声波点焊技术等点连接工艺方法,其中工艺垫片法电阻点焊能在相对低的焊接电流务件下获得具有高强度的点焊接头;搅拌摩擦点焊和超声波点焊属于固相连接,在异种金属焊接领域优势明显.可根据技术条件和具体要求选择点连接方法.     

Mechanical Behavior of Reinforcement Stirrups BSt 500<Subscript>s</Subscript> at Corrosive Environment

To date, there is no widely accepted regulation on the minimum required diameter of the bending drums, which shape the stirrups of the main concrete reinforcing bars, varying between 4 and 12 times the diameter of the bent bar, and thus resulting in various plastic strains. In the present work, the influence of the degree of plastic strain on the mechanical properties of steel bar of Class BSt 500_s for concrete reinforcement stirrups is investigated, under the additional implication of laboratory corrosive conditions. The increase of the degree of the plastic strain of the stirrup bar had as a result a significant decrease in the ductility properties of the steel. Moreover, it is shown that the combination of plastic strain and corrosion causes additional damages, as strain fractures were recorded lower than that defined by the current specifications for concrete reinforcement, indicating the need for a new review of the relative specifications.     

Zn-Al-Cu基合金无钎剂钎焊泡沫铝的界面结构及力学性能

以Zn--Al--Cu基合金为钎料, 对74.7%---91.6%不同孔隙率的泡沫铝采用无钎剂钎焊方法进行连接实验. 采用OM和SEM观察钎缝组织及界面结构, EDS测定界面元素分布, XRD分析界面物相, 通过热力学分析验证钎料中Cu和Zn与母材中Al元素的相互作用和除膜机理, 对钎焊接头试样进行拉伸和剪切性能实验, 分析孔隙率与接头试样强度之间的关系.结果表明, 该无钎剂钎焊方法在泡沫铝端 面之间形成密实结构的连续钎料层,未改变母材结构特征; 钎缝组织由Al(Zn) 固溶体、Zn(Al) 固溶体、Cu₄Zn及MgMnO₃组成; 连接界面主要由Al(Zn)固溶体组成, Zn,Al和Cu在界面上相互扩散而形成一定扩散梯度, 熔合良好, 钎焊接头抗拉强度与母材相当, 剪切强度略高于相同孔隙率母材的剪切强度,抗拉强度和剪切强度均随孔隙率增加而明显降低.     

基于自约束结构炸药的T2/Q345爆炸焊接及数值模拟

为提高炸药能量利用效率、降低能量耗散,利用自约束结构炸药进行爆炸焊接研究.以T2铜和Q345钢分别作为复层与基层,自约束结构炸药作为焊接炸药,借助ANSYS/AUTODYN软件模拟爆炸焊接过程,并进行T2/Q345爆炸焊接试验,对复合板试件进行拉剪性能检测和微观形貌观察分析其焊接质量.结果表明,T2/Q345爆炸焊接的碰撞速度距起爆端100 mm后均大于临界碰撞速度345 m/s,距起爆端150 mm处碰撞速度达到最大值567 m/s.T2/Q345复合板起爆端呈直线结合,并随着传爆距离增加变为波形结合.T2/Q345复合板远离起爆端的平均剪切强度为237.0 MPa,断裂位置位于铜一侧.试件被拉剪破坏后的铜层出现加工硬化现象,远离结合界面的显微硬度和塑性变形程度呈增强趋势.自约束结构炸药可降低自身爆炸产物飞散,使炸药能量更多地转化为复层动能,提高能量利用率.     

Extracting dimensional information from steel reinforcing bars in concrete using neural networks trained on data from an inductive sensor

A new method is presented for extracting dimensional information from steel bars using images generated by an inductive sensor. The technique is based on the application of two feedforward backpropagation neural networks; one to estimate bar depth and the other to estimate bar diameter. Both of the networks have been trained on a set of data that consists of the peak parameters of six different bars scanned at 41 different bar depths. These input and target data must be pre-processed to obtain a good network generalisation. By testing the two networks with a completely different set of data, accurate performance has been obtained. Real, two-dimensional scan data have then been applied to both of the networks and the bar dimensional parameters have been extracted successfully. The advantage of the neural network method for extracting information is that it continues to operate reliably for very deep bars, for which the signal strength is severely attenuated and manifests a poor signal-to-noise ratio. Depth and diameter measurements have been obtained for bars located down to 58 mm, with errors that satisfy the requirements of the BS 1881 standard. At a depth of 40 mm, these measurements yield an error of ±4%, and this decreases as the depth reduces; in other words, the extracted bar diameter is within the requirements of the DIN 488 standard.     

The bonding properties and interfacial morphologies of clad plate prepared by multiple passes hot rolling in a protective atmosphere

SUS304 stainless steel and plain carbon steel were first bonded by hot rolling in an argon atmosphere and were subsequently hot-rolled by multiple passes in air. Shearing and peeling tests were performed according to appropriate standards to evaluate the bonding results. The interfacial microstructures, composition diffusion and peeling fractographies of the clad plate samples were used to examine the bond quality. The effects of bond parameters on the bond properties of clad plate were studied. The experimental results indicate that the shear strength reaches 266 MPa, and the peel strength is up to 322 N/mm at 1323 K in the first pass, representing a reduction of 24.3%. Both the shear strength and the peel strength increase with increases in bonding temperature and total reduction ratio. The maximum shear strength reaches 361 MPa, and the peel strength is up to 510 N/mm at 1323 K after six passes with a total reduction ratio of 74.8%. Both the dimension and number of interfacial pores decrease rapidly with increasing rolling passes. Multipass hot rolling generates a number of local embedments at the interface and improves the interfacial bonding strength.