Effect of process parameters and talc ratio on hot plate welding of polypropylene

This study analyzes the influence of different talc ratios on weld strength of polypropylene joined with hot plate welding process. It further determines the optimum welding parameter settings to achieve the optimum weld strength and observes the effect of process parameters, namely plate temperature and heating time on the joint quality. Process parameters were considered as variables and their effect, interactions and relative significance were investigated by utilizing design of experiment. Simultaneously, a mathematical predictive model of the weld strength was developed in terms of welding parameters. The model can predict effectively weld strength with a 95% confidence level.     

碳纤维/聚苯硫醚热塑性复合材料电阻焊接工艺

本文针对航空器结构用碳纤维/聚苯硫醚(CF/PPS)复合材料为研究对象，开展电阻焊接工艺研究；利用CF/PPS复合材料混编织物作为电阻元件，成功制备了CF/PPS复合材料层板电阻焊接接头；重点利用Taguchi方法和方差分析获取CF/PPS复合材料层板电阻焊接最佳工艺参数(电流为12 A，压力为1.5 MPa，时间为30 min)及各参数对焊接接头剪切强度的贡献(电流为83.37%，压力为9.55%，时间为6.02%)。最佳焊接工艺参数焊接的接头单搭接剪切强度约为17.88 MPa；同时，对最佳参数焊接试样(H-LSS)和较低剪切强度试样(L-LSS)的焊接接头截面和剪切失效断口形貌进行了观察和分析。结果表明:H-LSS试样的焊缝区域树脂填充和浸润良好，且主要剪切失效形式为层间剪切失效，即为纤维与树脂基体脱黏及CF/PPS织物复合材料断裂混合失效；L-LSS试样的焊缝区域树脂填充和浸润较差，存在较多空隙，且剪切失效形式为焊缝界面脱黏失效。      

Vibration welding of polypropylene-based nanocomposites – The crucial stage for the weld quality

Thermoplastic nanocomposites used for vibration welding are compounded on a twin-screw extruder by dilution of a concentrate masterbatch containing 14 vol% of filler. They are butt welded under different weld pressures by a linear vibration welding machine. By means of a quick ramp-down technology, this machine enables a very short vibration damping time of about 40 ms. The influence of different damping time on the weld strength of various materials is investigated. The experimental results are compared also with the results of simulation. In the case of nano-silica filled polypropylene, no impact of the damping time on the weld quality is detected and the possible reasons for this observation are explained.     

Application of Taguchi approach to optimize friction stir spot welding parameters of polypropylene

This paper shows experimental and numerical results of friction stir spot welding of high density polypropylene. The determination of the welding parameters plays an important role for the weld strength. The experimental tests, conducted according to combinations of process factors such as tool rotation speed, plunge depth and dwell time at beginning welding, were carried out according the Taguchi orthogonal table L9 in randomized way. The Taguchi approach was used as a statistical design of experiment technique to set the optimal welding parameters. The results show coherence between the numerical predictions and experimental observations in different cases of weld strength. The signal-to-noise ratio and the analysis of variance were utilized to obtain the influence of the friction stir spot welding parameters on the weld strength. Finally, the improvement in the weld strength from the initial welding parameters to the optimal welding parameters was about 47.7%.     

Numerical simulation of tensile strength of upset welded joints with experimental verification

Resistance upset welding (UW) is a widely used process for joining metal parts. In this process current, time and upsetting force are three parameters that affect the quality of welded products. This paper considers numerical simulation and experimental investigation of UW process parameters. The investigated parameters include heating and post-weld heating current and their corresponding duration as well as interference of the part features that form the joint. In this study, evaluation of tensile strength of the welded joint with variation of the process parameters is also reported. For numerical analysis, a two-dimensional axisymmetric model using a coupled electro-thermal finite element method is developed to study the thermal behavior of the welded joints. The results of this numerical simulation are used to determine the status of the weldment and therefore evaluate the quality of the weld at the joint. Both numerical and experimental results suggest an optimum set of welding parameters, i.e. time and electrical current that yields a maximum value for the tensile strength of the joint. Also the effects of post-weld heating time and current on the tensile strength are evaluated and show that these parameters have a remarkable effect on improving tensile strength of the weldment.     

Combined effect of the nature of the filler and the compatibilizer on the weld line properties of filled blends

The mutual effect of the nature of the filler and the compatibilizer on the properties of a ternary blend based on polypropylene (PP) polyamide-6 (PA) and an inorganic phase is investigated. Low aspect ratio irregular shaped CaCO₃ and high aspect ratio plate-like talc are selected as inorganic phases. The effect of different filler levels on the morphology of the weld line region and the region far from the weld line are studied while special attention is paid to both uncompatibilized and compatibilized PPPA blends with maleic anhydride grafted polypropylene (MA-g-PP). It is observed from scanning electron microscopy (SEM) studies that plate-like talc reduces the elongated domain size in the weld line region much more effectively than low aspect ratio CaCO₃ for uncompatibilized filled blends. Although both filler are selectively wetted by the dispersed PA phase, the morphology homogenization in the weld line region is found to be related to the ability of the filler to reduce the elongated domain size by increasing the viscosity of dispersed phase rather than the shape of the filler. The selective wetting of talc particles by the PA phase seems to be beneficial in increasing weld line strength by increasing the viscosity of the PA dispersed phase with respect to filler content much faster than CaCO₃. However, the additional compatibilization effect causes much finer, homogeneous spherical PA/ CaCO₃ domains dispersed within the PP matrix compared to plate-like PA/talc domains, which are highly oriented at the weld line. For that reason, the shape of the filler is of predominant importance to achieve homogeneous morphology in the weld line region. Compared to uncompatibilized filled blends, low aspect ratio irregular shaped CaCO₃ yields better weld line strength with respect to all filler levels. For compatibilized PPPA filled blends, the shape of the filler is of supreme significance in order to achieve better mechanical properties especially where weld line properties are concerned.     

基于导热板的碳纤维增强聚醚醚酮复合材料感应焊接温度调控

研究了碳纤维增强聚醚醚酮(CF/PEEK)复合材料感应焊接中厚度方向及焊接面内的温度分布及调控。基于对温度分布结果的分析,使用导热板结合真空袋压的方式对CF/PEEK进行感应焊接,结合使用合适的功率及加热时间,测试了焊接件的单搭接强度,观测分析了焊接件的断裂形貌。结果表明,导热板对层合板表层和边缘均有良好的散热效果;焊接功率越低,焊接面的加热均匀性增加,但是会延长加热时间。在真空袋中对层合板上表面和两侧添加导热板,在输出功率示数为600时感应焊接300 s,焊接件的单搭接剪切强度达到41.57 MPa。      

Shear strength and meltdown behavior of reinforced polypropylene assemblies made by resistance welding

Resistance welding (RW) involves placing an electrically conductive implant between two parts that are mated under pressure. Heat is dissipated in the implant and causes melting, diffusion, flow and ultimately welding to occur. This research examines the RW of long-glass-fiber-reinforced polypropylene (LGF-PP) to continuous-glass-fiber-reinforced polypropylene (CGF-PP) using a stainless steel mesh-implant. The effects of welding time, applied current, and weld pressure on the temperature near the mesh, meltdown and the compression-shear strength of the welds were assessed. The results show that it is possible to attain shear strengths of the order of 20 MPa under optimized welding conditions. The meltdown and strength correlate well with a semi-empirical lumped parameter dependent on weld time, current squared and pressure. This parameter can be used to estimate appropriate welding conditions without the use of complex finite element modeling or extensive experimental work.     

Development of response surface model for tensile shear strength of weld-bonds of aluminium alloy 6061 T651

The development of a response surface model to study the influence of process parameters of weld-bonding on tensile shear strength of the weld-bond of 2 mm thick aluminium alloy 6061 T651 sheets has been reported. Significant and controllable process parameters of the weld-bonding (surface roughness, curing time, welding current, welding time and electrode pressure) and their ranges were identified by conducting pilot experiments. Welding current, welding time and welding pressure were identified as significant and controllable parameters. Influence of the significant process parameters and their interaction on the tensile shear strength of the weld-bonds was studied using response surface methodology (RSM). Using model, the optimal combination of weld bonding process parameters for maximum tensile shear strength of the weld bond was obtained. The validity of the model was evaluated on weld bonds developed using different levels of process parameters and testing their tensile shear strength. The model error was found to be in a range of 3–7%.     

FRACTURE BEHAVIOUR OF UNTREATED AND SILANE-TREATED TALC-FILLED POLYPROPYLENE COMPOSITES

Abstract— Fracture behaviour of injection-moulded polypropylene filled with silane-treated talc was studied as a function of filler volume fraction (0–20%) and compared to that of polypropylene filled with untreated talc. High-rate tests (0.57 m/s) on SENB specimens were carried out using an instrumented Charpy impact pendulum, and linear elastic fracture mechanics (LEFM) was applied to calculate the fracture parameters, K _C and G _C. It was found that moderate fractions of talc which were added to the polypropylene matrix increased the fracture toughness of the composite independent of the talc surface treatment. This general improvement seems to be due to the peculiar orientation of the talc platelets in the injection-moulded specimens. The fracture behaviour of the composites was also studied at low strain rate (1 mm/min) by tests on J -integral type specimens with the same SENB geometry. In this case, the composites with silane-treated talc presented poor J -integral values compared to those of the samples with untreated talc. This was attributed to a reduction of the plastic zone at the crack tip, since the improved coupling between the talc platelets and matrix increased the yield strength of the composite. All the results are explained on a basis of morphological and microstructural details.     

V型坡口多层多道焊焊道几何参数预测

中厚板V型坡口多层多道焊焊接过程中,每一条焊道的几何参数都会影响最终焊缝成形质量。为了评估V型坡口多层多道焊缝成形质量,提出了基于麻雀搜索算法(SSA)优化的BP神经网络模型预测焊道几何参数。文中通过实验分析各焊接工艺参数对焊道成形几何尺寸的影响,确定了以焊接电流、焊接速度、熔池宽度作为模型的输入,将能表征焊道质量的焊道高度和焊道计算高度作为模型的输出。对优化前后BP神经网络预测模型的性能进行对比,结果表明,优化后模型预测结果的相对误差分别保持在±4%、±8%以内,模型的稳定性、准确率都有较大提升,证明了该方法可有效预测V型坡口焊接时的焊道几何参数。     

Effect of Welding Parameters on GTA Weld Shape for Pure Iron Plate under Ar-O2 Mixed Shielding

Weld shape variation for different welding parameters is investigated on pure iron plate under gas tungsten arc (GTA) welding with argon-oxygen mixed shielding. Results showed that small addition of oxygen to the argon base shielding gas can effectively adjust the oxygen adsorption to the molten pool. An inward Marangoni convection occurs on the pool surface when the oxygen content in the weld pool is over the critical value, 80×10-6, for pure iron plate under Ar-0.3%O2 mixed shielding. Low oxygen content in the weld pool changes the inward Marangoni to an outward direction under the Ar-0.1%O2 shielding. The GTA weld shape depends to a large extent on the pattern and strength of the Marangoni convection on the pool surface, which is determined by the content of surface active element, oxygen, in the weld pool and the welding parameters. The strength of the Marangoni convection on the liquid pool is a product of the temperature coefficient of the surface tension (dσ/dT) and the temperature gradient (dT/dr) on the pool surface. Different welding parameters will change the temperature distribution and gradient on the pool surface, and therefore, affect the strength of Marangoni convection and the weld shape.     

Application of Taguchi approach to optimize of FSSW parameters on joint properties of dissimilar AA2024-T3 and AA5754-H22 aluminum alloys

In this study, the effect of plate positioning on mechanical properties of dissimilar lap joints was investigated by friction stir spot welding (FSSW) process. The determination of the welding parameters plays an important role for the weld strength. For the effective use of the dissimilar aluminum joints, the FSSW must have an adequate strength. The quality of the joint was evaluated by examining the characteristics of the joining efficiency as a result of the lap-shear tensile test. Four process parameters were selected: the tool rotation speed, dwell time, tool plunge depth, and tilt angle.The process parameters were optimized by Taguchi technique based on Taguchi’s L9 orthogonal array. The optimum welding process parameters were predicted, and their percentage of contribution was estimated by applying the signal-to-noise ratio and analysis of variance. The experimental results showed that the positioning of the plates played an important role on the strength of the joints. Finally, the results were confirmed by further experiments.     

Numerical and experiment analysis of residual stress on magnesium alloy and steel butt joint by hybrid laser-TIG welding

Hybrid welding technology has received significant attention in the welding of dissimilar materials recently. While, great welding residual stress and deformation often result by the difference of coefficient of thermal expansion This study describes the thermal elastic–plastic analysis using finite element techniques to analyze the thermo mechanical behavior and evaluate the residual stresses and welding distortion on the AZ31B magnesium alloy and 304L steel butt joint in laser-TIG hybrid welding. A new coupled heat source model was developed which combined by double-elliptic planar distribution, double-ellipsoid body distribution and Rotary–Gauss body distribution model. From the results, it can be concluded that the temperature distribution at the hybrid weld region is exposed to faster rate of heating and cooling in hybrid welding than TIG. Furthermore, compared to the welding stress distribution on the TIG weld, residual stress σ_y is found about 20% higher on hybrid weld joints, and the residual stress on the 304L steel plate is lower than that on the AZ31B magnesium plate.     

Ta/Ni/Mo异种薄板激光熔钎焊正交试验探究

目的探究Ta/Mo异种薄板激光熔钎焊的最佳焊接工艺参数。方法设计正交试验方案,得出理论最优工艺参数。采用SL-08型Nd:YAG脉冲激光焊机对薄板完成焊接得到焊接接头;通过微机控制电子万能试验机测试焊接接头的抗拉强度;通过显微硬度计测量焊接接头显微硬度;通过OM测试方法观察焊缝组织。并通过焊接接头的性能对得出的最优工艺参数进行验证。结果在最佳焊接工艺参数下,接头的最大平均抗拉强度为230 MPa,接近Ta母材的抗拉强度,拉伸试样断裂发生在近Ta热影响区;焊缝表面连续,可看到清晰的鱼鳞纹,焊缝背面宽度均匀,焊缝成形良好;焊缝中心区域出现了针状共晶组织,热影响区的晶粒都呈现不同程度的长大现象;形成接头的焊缝区硬度最高,钼母材次之,钽母材最小。结论通过正交试验得出的最优工艺参数是准确的,Ta/Mo异种薄板最佳焊接工艺参数为:激光功率P为20.8 W(激光功率百分比为26%),脉宽T为5.5 ms,脉冲频率f为4.0 Hz。     

Effect of heat-input and cooling-time on bead characteristics in SAW

Load-carrying capacity of weld joints could be identified by its shape and size where weld bead geometry and shape relationship parameters are of utmost importance. Heat input and preheating temperature together can control the cooling time of weld, which in turn determines the weld microstructure and its mechanical properties. To control the shape and geometry of weld bead, it is necessary to understand its relationship with cooling time. In present work, preheating temperature is used as process variable along with heat input varying parameters for understanding their effects on weld bead geometry and shape relationship parameters using submerged arc welding process on high-strength low alloy pipeline steel. The experimental investigation was then analyzed by using the mathematical modeling in context with response surface methodology. The mathematical model predicts the influential dependency of cooling time on the preheating temperature than the other weld process parameters. The associated effects in relation to the process parameters have been discussed and analyzed in the present study.     

The use of tensile tests to determine the optimum conditions for butt fusion welding certain grades of polyethylene,polybutene-1 and polypropylene pipes

The optimum conditions for butt fusion welding certain grades of polyethylene, polybutene-1 and polypropylene pipes have been determined on the basis of tensile test results. The effect of the welding bead has been discussed and the conclusion reached that removal of the welding beads enables a clearer picture to be obtained of weld performance when this is judged from a tensile test. An examination of the microstructures of each weld has shown the presence of different zones. The importance of these zones is discussed in relation to the short- and long-term strength of the welds.     

焊缝匹配影响焊接残余应力的研究

采用有限元法对相同温度场的焊缝与母材强度和线膨胀系数匹配影响焊接残余和的规律进行了数值模拟,计算结果表明：等强度等匹配的焊缝区纵向残余应力水平高达母材的屈服强度,     

6061-T6铝合金中厚板-节点套多层多道焊数值模拟

为研究铝合金中厚板-节点套接头在多层多道焊后的残余应力和变形分布,本文基于ABAQUS软件建立了该接头三维有限元模型,采用双椭球热源、生死单元法以及顺序耦合法,对6061-T6铝合金中厚板-节点套多层多道焊进行数值模拟,并分析了接头的温度场,以及在夹具约束下的焊接残余应力及变形的分布情况。研究结果表明:数值模拟与实际接头的熔池形状吻合度较高;摆动焊接过程中温度曲线呈多峰结构;焊件的升温速率明显大于冷却速率,且冷却速率随时间逐渐减小;焊接残余应力主要集中在焊缝及夹具区域,且小于6061-T6铝合金在室温下的屈服强度;接头的最大横向残余应力为129.9 MPa,中厚板上的横向残余应力大于节点套上的横向残余应力;接头的最大纵向残余应力为132.9 MPa,沿焊接方向,焊缝处的纵向残余应力呈山峰状分布;该接头在Y轴方向上的变形最大,为1.494 mm,该接头的最终变形结果为上凸变形。     

Effect of process parameters on electromagnetic impact welding of aluminum sheets

Electromagnetic forming of aluminum sheets has been studied in detail by many researchers due to its advantages of increased formability and reduced springback. The feasibility of electromagnetic impact welding of aluminum sheets has been established, but the effect of process parameters on the weld strength has not been reported. The present study investigates the effect of parameters such as energy, standoff distance and coil geometry on the shearing strength and the width of the weld achieved by electromagnetic impact welding of aluminum sheets. A study has been carried out to characterize the effectiveness of the process of welding two aluminum sheets of same chemical composition and of 1 mm thickness. The results of the microstructure and shearing strength tests are reported in this paper. The shearing strength and the width of the weld are found to increase with an increase in discharge energy. Further, when the geometry of the coil is changed from rectangular shape to tapered shape, it gives higher shearing strength. The standoff distance has an optimum value that gives maximum shearing strength and width of the weld. If the standoff distance is varied on either side of its optimum value the shearing strength and the width of the weld reduce.