Research On The Characteristics Of Ultrasonic Assisted Laser-arc Hybrid Welding Of Aluminium Alloy

Laser-MIG hybrid welding is a welding method that has been paid more attention by industry in recent years.It combines the advantages of laser heat source and arc heat source to make up for the deficiencies of the two,and is gradually becoming a reliable and efficient welding method.In the aluminum alloy laser-MIG hybrid welding process,welding defects such as pores,hot cracks,and large numerical crystals are often generated.At the same time,the tensile stress caused by thermal expansion and contraction of the weld seam will also affect the performance and use of the welded joint.A large number of studies have shown that the application of ultrasonic waves in the traditional welding process can use the cavitation and acoustic flow effects of ultrasonic waves in the molten pool and the impact of the horn on the back of the weld seam.The stress distribution plays a role in improving.Therefore,in this subject,the use of 2000 Hz ultrasonic waves is used to assist in the laser-MIG hybrid welding process to carry out research on the relevant welding characteristics.In the research process,first of all,the method of surfacing welding was used.In the process,high-speed camera was used to collect the droplet transition and the shape of the molten pool in real time.It was found that in the short-circuit transition,the addition of ultrasound reduces the surface tension of the droplets,improves the short-circuit blasting phenomenon,makes the droplets easier to transition,and the average droplet transition period is significantly reduced.The average droplet transition period was reduced from37.6 ms when no ultrasound was applied to about 23.3 ms after ultrasound was applied.At the same time,the standard deviation of the average droplet transition period also decreased,indicating that the stability of the droplet transition is improved.On the other hand,the shape of the molten pool changes from the front narrow width to the front width when no ultrasound is applied.In order to reduce the front width and narrow width after the ultrasound is applied,the rear edge height angle also decreases significantly.To speak of the improvement of the spreading performance of molten metal by ultrasound.Then,the welding seam surface forming under three process parameters of different,different fiber spacing and different horn pressure was studied.Through single variable control,the fiber spacing was 3mm,the laser energy ratio was 0.52,and the horn pressure At 95 N,a welded joint with a well-formed weld surface was obtained,and the subsequent process parameters of this subject were determined.It should be noted that when the pressure of the horn is too large,the effect of mechanical vibration is too strong,a hump bead appears,and the molding quality is not good.The X-ray flaw detection results on the weld seam show that the light fiber spacing has little effect on the porosity.The porosity is stable at 4.8%-5.7%.When the laser energy is relatively high,the porosity can be reduced to 2.82%.After applying ultrasound,it can effectively reduce the existence of porosity and minimize the porosity.When the horn pressure is 62 N,the porosity can be reduced to 1.05%.Light microscopic observation of cross-section pores,under the influence of cavitation,the size of metallurgical pores has increasedFinally,the ANSYS finite element software is used to model the workpiece entity,and the finite element simulation calculation is performed on the ultrasonic assisted welding process.First,the force load is applied to the ideal unstressed workpiece to verify the follow-up and correctness of the force load.Then,the temperature field is simulated using the double ellipsoid heat source + Gaussian cylinder heat source,and the heat source is checked using the cross-sectional morphology.Finally,the residual stress field of ultrasonic assisted welding was simulated,and it was found that with the increase of the force load,the tensile stress at the ultrasonic input position gradually evolved into a compressive stress,and the ultrasonic force load would deform the back of the workpiece by about 0.3 mm.