Research On The Experimental Apparatus And Measurement Methods For Superplastic And Plastic Forming

Plastic forming process is an important foundation of machinery manufacturing industry. As a branch of advanced manufacturing technology, plastic forming process has become its development direction. With the development of science and technology, plastic forming technology has increasingly presented a trend of technology convergence. The trend puts forward new requirements for those researchers engaged in theoretical research and technological development of plastic forming, as promotes research and development of the experimental apparatus and measurement methods for superplastic and plastic forming. The thesis analyzes the status-quo of the experimental apparatus and measurement methods for superplastic and plastic forming, and then under a tutor, load and magneto-thermal coupled analysis apparatus, arbitrary volume measurement instrument, arbitrary area measurement instrument and arbitrary surface curvature measuring instrument are developed.In the field of superplastic and plastic forming, it is very important to understand mechanical properties of materials during deformation and study it through experiment. The interdisciplinary trend results in more attention to mechanical properties of materials under multi-field. The existing experimental apparatus for superplastic and plastic forming can not solve the interference problem of the temperature field with the magnetic field and the conflict problem between the seal oxidation of the furnace and the friction between the chuck bars and muffle furnace mouth. These problems induce that it is more difficult to perform load and magneto-thermal coupled analysis. So development of the load and magneto-thermal coupled analysis apparatus, which can solve the above problems, is a burning question. The load and magneto-thermal coupled analysis apparatus described in this thesis is composed of the argon purification device, the temperature control and heating device outside the furnace, the pressure-regulating device, the magneto-thermal coupled analysis apparatus, the electronic universal material testing machine and the control system. The argon purification device inputs the purified argon into the temperature control and heating device outside the furnace; the purified argon heated to the set temperature value is inputted into the pressure-regulating device; the high-temperature argon which is regulated pressure to the set pressure value is inputted into the load and magneto-thermal coupled analysis apparatus; the load and magneto-thermal coupled analysis apparatus, which may instead of the heating furnace of the conventional electronic universal material testing machine, is fixed between its movable crossbeam and frame. Using the heating device outside the furnace and dynamic sealing technologies, the load and magneto-thermal coupled analysis apparatus can perform oxidation protection for the test specimen and furthermore can make mechanical properties test under magneto-thermal coupled condition.With the rapid development of science and technology, the measuring technique plays an important role for national development. So many industrially developed countries attach great importance to the study of the various measurement techniques. Traditional measurement method is only applied to measure simple parts, and with the development of modern manufacturing and processing technologies, the shape of the workpiece becomes increasingly complex, and the measurement method can not meet the requirement. CMM is developed in recent decades, and its measuring accuracy is very high. But CMM measurement speed is too slow; its cost is high; furthermore because probe must contact with workpiece surface, it is easy to scratch the surface of the workpiece. The non-contact measurement methods have the faster measuring velocity, but Point cloud processing and surface modeling is very time-consuming. In order to meet the practical needs of research projects, arbitrary volume measurement instrument, arbitrary area measurement instrument and arbitrary surface curvature measuring instrument are developed. The arbitrary surface curvature measuring instrument is used to solve the difficult problem to measure the curvature radius of axisymmetrical surface of revolution during the superplastic free bulging; the arbitrary volume measurement instrument is used to solve the measurement problem of the overall and partial volume; the arbitrary area measurement instrument is used to solve the measurement problem of the overall and partial area.The arbitrary volume measurement instrument:plastic forming obeys the condition of constant volume. During the precision plastic forming process, the volume of workpiece is accurately determined in the first place. The volume of workpiece includes the exact volume of the workpiece added to the thermoplastic forming loss and machining allowance. The author develops the arbitrary volume measurement instrument based on the patent whose name is the arbitrary-shape workpiece volume measurement instrument. The instrument can not only measure the volume of workpiece with arbitrary form and density larger than water, but also that with density less than water, and that it can measure the local volume of workpiece. The instrument is characterized by simple structure and high accuracy. By the instrument, the whole and local volume value of an auto connecting-rod in each forming step was measured. It provides an important means to work out connecting-rod forming process.The arbitrary area measurement instrument:during sheet metal forming, the data need to be identified as follows:the area of blank and formed part, the area of formed part in each process and the area corresponding to the last process. The author develops the arbitrary area measurement instrument based on the patent whose name is the arbitrary-shape sheet metal parts area measurement instrument. The instrument can not only measure the area of sheet metal parts with arbitrary-shape and density larger than water, but also that with density less than water, and that it can measure the local area of sheet metal parts. According to the law of the constant volume in deformation and the assumption that the thickness of sheet metal parts is constant, the forming process plan is worked out. The instrument is characterized by simple structure and high accuracy.The arbitrary surface curvature measuring instrument:the measurement techniques of complex surface are widely used in industrial, medical and military fields. In recent years, the continuous development of Reverse Engineering promotes its development. The surface measurement aims not only to evaluate the quality of surface but also to obtain information on the geometry of surfaces. According to the patent named as surfaces measurement, the working principle, structure, measuring method and accuracy analysis of the arbitrary surface curvature measuring instrument are introduced. Fixed chord-width measurement method has simple structure, poor adaptability and low accuracy, so it has gone out of use. The variable chord-width measurement method has made an essential breakthrough in its principle, so it has wide adaptability and high precision. But needle-shaped probe used in variable chord-width measurement method restricts its application. The variable chord-width measurement method with spherical probe described in this thesis overcomes the shortcomings of needle-shaped probe, so it is characterized by simple structure, wide adaptability and high accuracy.