Research And Development Of Powder Conveying System For Crack Laser Repair Experimental Device

Metal components will generate cracks due to fatigue and other reasons in the process ofusing,which will seriously affect the performance,life and safety of mechanical products.In order to avoid mechanical problems and process problems caused by further crack propagation,Developing a device for repairing initial cracks has significant application value.According to the surface micro-crack repair problem of 304 metal component,reference to the existing technical methods of crack repair and the requirements of practical applications,the basic functions required for the micro-crack repair experiment device are determined,a framework of experimental device for repairing surface micro cracks based on laser heating and synchronous powder feeding is formed.The factors that affect the repair results are mainly derived from two aspects,the one is related to laser,the other important factor is related to powder conveying,such as the stability and convergence of metal powder flow,conveying capacity,etc.First,according to the processing requirements of detecting crack,heating crack area and repairing crack.the basic structure of the experimental device is determined.By comparing the advantages and disadvantages of various methods,a reasonable crack detection method is chosen,and the laser part is briefly designed referencing to the related factors,and the overall structure layout is determined.Then the powder feeding system was designed in detail.Different from the common powder feeding structure,in order to convenient to operation and flexible in processing,the powder feeding system needs small powder storage,stable powder conveying without the influence of the change of the system position,and combines with other parts of the device cordinately.According to the design and use requirements of the powder feeding system,because of the distance between the device and the workpiece in the process of repairing,the powder is transported to the surface of the workpiece by gas solid two phase flow transmission method.In order to make the powder conveying capacity stable and controllable,the powder is removed from the powder casing by screw transportation mode,and accurately transfered to the heating area by the coaxial transportation method.So the powder feeding system is made up of power supply,powder feeder,flow detection and conveying nozzle.Based on the theoryof two phase flow,designing and calculating the diameter of the conveying pipeline and airflow speed,as the basic parameters of the system design.According to the processing conditions,the structure of the two channel coaxial powder feeding nozzle is designed,including the introduction section and the convergence section,the fluid channel structure and dimension parameters are optimized by Fluent,which makes the nozzle have a good fluid convergence effect and achieve the design requirements,providing a reference for the design of the related nozzle.In addition,a deadweight screw transportation conical powder feeder is designed,its casing screw transportion pole are designed and calculated based on the empirical formula,the feasibility of the structure is verified by Fluent.By comparing various solid powder flow detection methods,the flow acquisiton system is designed based on the photoelectric method,and the Lab VIEW program is written to acquire and display signal.The feasibility of the acquisiton system is verified through simulation.Finally,Taking the above design and calculation into account,the transportion system is checked by using Creo to draw the three-dimensional assembly models.and is printed by 3D.After debugging,the nozzle conveying effect is basically consistent with the simulation design result,the feasibility of the system and powder feeder design are verified at the same time.