Research On Stamping Coal Cake Process Modified Duncan-Chang Constitutive Model And Its Numerical Calculation

Stamp-Coking, which can produce high quality coke with inferior coal, is of great significant and widely recognized in coking industry as the coking coal is being depleted. Stamping process which compacts coal powder to a dense coal cake is the core of stamp coking. However, related equipments are designed through only analogy and experience but without properly theoretical support, which is the consequence of the lack of research in the original stamping process. The descrete partical method which applied to the analysis of stamping process cannot fit the particle scale. Meanwhile, constitutive model is hardly available with applying continuous medium method. Having taken as core issue the dynamic stamping process, carried out was this research, in which a theoretical system for the design and calculation concerning stamping process was established through the building of proper constitutive models, the exploration in calculation methods, and the application and analysis of field tests. The research provides not only the theoretical support for the design, analysis and improvement of the equipment, but also set a basis for the further development in Stamp-Coking industry. The following contents were drawn in the work:(1) A constitutive model for stamping coal cake was raised. The model took as basis the elastic nonlinear Duncan-Chang constitutive model from soil mechanics, and brought in Kelvin and Maxwell models from visco-elastic mechanics for dynamic purpose. Then the model was extended into three-dimensional and its partial differential equations were derived then solved numerically for the stress increment. Also given in the process was an accumulation method to distribute the initial stress between units. The model was then verified through the comparison between the results of numerical calculations and field tests.(2) A series of tests were designed and conducted and the loads of stamping were acquired, as well as the coal cake properties. First some necessary data, such as the test frequency and sensors range, were adopted through pretest, with which, then, unit force method was applied to the charging car structure for analyze to plan the test points. Also a protect frame was developed for the side wall pressure test. The coal box side wall and bed plate pressures, and some pivot stresses were acquired, along with coal cake properties through a tri-axial test. Besides providing the numerical calculation with certification and reference, the tests data itself is pioneering, and its processing results is a guideline in design.(3) The stamping process numerical calculation was divided into single compact mode and consecutive compacts mode, then, respectively, explored theoretically and methodologically. The aim of single compact is to investigate the distribution and change of coal cake stress in stamping process, while the consecutive compacts the form of the coal cake. For single mode, the constitutive model was further modified, and the initial confining pressure and initial stress balancing was investigated, to establish a calculation model for the analysis. Also the modified Duncan-Chang model was verified in it. For consecutive compacts, back-analysis was applied to fit the properties in stamping process based on density, to develop a method for the form of coal cake. Through the comparisons with field tests results, the methods is able to simulate the stamping compact and coal cake forming accurately, which means it can be utilized to analyze the origin of the charging car design, furthermore, makes available the adoption of advanced design methods in the industry.(4) Put the research achievements into application, generally indicated as the following. For design ideology, orthogonal test design was brought in to optimize the coal cake design parameters, which not only provided proper parameters for stamping related design, but also extend the application of stamping numerical calculation. For design calculation, a simplified design load model was raised, through the split of stamping pressure as impulse and coal pressure. For charging car structure, it was, according to the effect of stamping load, divided into side wall, support frame and main structure to calculate and improve respectively, then the improvements were verified in an assembled model and proven better, which has been applied to the industry manufacture.