Advanced Materials Research Vols. 538-541

Abstract: Thrust force is the most important element which will cause delamination in the drilling of CFRP. This paper developed a dynamic thrust force prediction model for CFRP drilling, by firstly, representing the drilling process into a three-step model. Secondly, the dynamic thrust force is decomposed into two parts. Thirdly, the thrust force components on both tool major cutting edge and chisel edge is developed according to the analysis on infinitesimal cutting unit. Lastly, several experiments are performed to compare the result of thrust force analyzed, which proves that the purposed model can analyze the dynamic thrust force in drilling of CFRP well.

Abstract: An automatic welding system based on playback robot is introduced. The composition and characteristics of the system, together with the application results of prototype, are provided. Compared with manual welding, its product quality is better and more consistent, production efficiency is about 4 times higher.

Abstract: To simulate the welding and heat treatment process of the Q345 plate with V-groove, Finite element software ANSYS was employed. A reasonable three-dimensional solid model was set up by using element birth and death technology to simulate the formation of the weld. Constraint was applied on both sides of the base metal in the welding and cooling process. Then constraint was removed when the specimen was cooled to room temperature, the angular distortion of welding increases by 75.03% after the constraint is removed. Then heat treatment was conducted on the plate of which the constraint was removed. The deformation results show that after heat treatment the angular distortion is reduced to 30.37% of the value before heat treatment.

Abstract: A 3D finite-elements model of 45# carbon steel of linear friction welding is built with the dynamic explicit code ABAQUS/explicit. The temperature field of workpiece, and the temperature change of center point of welding interface are showed in results. The center temperature of welding interface soars to 800°C, but the temperature of both ends of the welding interface are only 400°C or so at 0.75s. Then, the interface temperature rises slowly to about 920°C and maintains until welding ends.

Abstract: Aiming at the welding arc can act with the magnetic field, has electrical quasi-neutral and electrical conductivity. This paper introduced an adscititious longitudinal magnetic field to control the CO2 welding process and used the Hanover Welding Quality Analyzer to acquire the real-time welding signal. Meanwhile, the short circuit behavior of CO2 welding under the adscititious longitudinal magnetic field, was monitored with the High-speed Photography System. The results show that when the excitation current in an optimal range, the welding current decay and the frequency of short circuit transition is uniform and faster, smaller droplet size and the welding process is more stability than welding without adscititious magnetic field.

Abstract: Friction Stir Welding (FSW) is a new and developing technology that has been used succefully in the joining of aluminum and aluminum alloys.To demonstrate the feasibility of the auxiliary power of Q235 steel friction stir welding, we used orthogonal test method to design auxiliary power FSW parameter,then welded 200mm×80mm×4mm of Q235 with the parameter. The result shows that the rotating 1200 r/min, the stay time 10s and the heating temperature 700 °C,the welding joint tensile strength can reach 332.19 MPa. Analysing the parameter fracture morphology,we found that the fracture is divided into three levels: the upper part is the ductile fracture; the middle part is the combination of the ductile fracture and the brittle fracture;the lower part is the majority of the brittle fracture, and exists the local ductile fracture. Analysing the microstructure,we found that welding joint is divided into the base zone, the heat affected zone,the thermo-mechanically affected zone and the stir zone,and the microscopic organization of every area is influenced by the heat and the force on the area. The microhardness of stir area improves 12% on average than the base’s.The microhardness of the heat affected zone and the thermo-mechanically affected zone decreases , comparing to the base’s.

Abstract: Resistance spot welding (RSW) has been extensively used as a sheet metal joining process, and the welding process identification is the essential issue for the design of high performance control strategy and set-up of a new welding schedule. However the RSW is a nonlinear time-varying uncertain process which couples the thermal, electrical, mechanical and metallurgical dynamics. To understand this complicated physical phenomenon an M-series pseudo-random electrical pattern is adopted to excite the RSW electrical-thermal dynamics and the thermal response is recorded according to the welding power outputs. Based on the experimental information the transfer function of an RSW electrical-thermal mechanism is identified, and the optimum model order and parameters are determined. Subsequently a control-oriented RSW model is established to explore the welding power control algorithm. The simulated results from the control model show their agreement with the experimental data, which validates its feasibility for corresponding welding control.

Abstract: Molecular dynamics simulations are used to investigate the junction formation of two crossed single-walled carbon nanotubes (SWCNTs) with or without preexisting structural defects by heat welding. The junction formation of the chiral SWCNTs by heat welding is discussed. Furthermore, both the single vacancy defects and double vacancy defects are introduced in SWCNTs to explore the effect on junction formation by heat welding. We found the single vacancy defects and double vacancy defects pairs distributed on both crossed SWCNTs will accelerate the heat welding process and make the junction easier, and the required temperature for junction formation will be significantly reduced.

Abstract: Plasma arc welding was applied to join AISI 304 and AISI 201 stainless steel sheets. Nitrogen was mixed in argon shielding gas to help control microstructure and improve corrosion property of the weld. It was found that increasing nitrogen in shielding gas from 0 to 12 %v/v reduced the amount of delta ferrite in austenite matrix of the weld from 20 to 16 %v/v. This indicated the role of nitrogen as an austenite stabiliser. From polarisation test in 3.5wt% NaCl solution at 25 °C, increasing nitrogen in shielding gas nobly shifted a pitting corrosion potential from 401 to 472 mV vs Ag/AgCl. This corresponded to the increase of nitrogen content in the weld from 0.11 to 0.19 wt%.

Abstract: Ultra-thin Titanium foil, which is widely used in manufacture of thin-walled titanium tubes, automobile parts, medical and other industrial fields, is an excellent structural material. Micro-plasma arc welding system which was developed independently by Shanghai University of Engineering Science was used in the experiments of welding Titanium foil 0.05mm thick. Welding experiments were carried out with matching parameters including welding current type, welding current value, pulse frequency, ratio of peak value and base value of pulse current, amount of lap and the other welding process parameters set constant, achieved one side welding both sides formation and got good welding formation. Based on these experiments, influences on welding quality induced by those factors are analyzed.