Dissertation > Excellent graduate degree dissertation topics show

Research on Evolution of Void Defects in Heavy Forgings during Upsetting Process

Author: LiZuo
Tutor: CuiZhenShan
School: Shanghai Jiaotong University
Course: Materials Processing Engineering
Keywords: void closure Gurson model orthogonal experimental design heavy forging
CLC: TG316
Type: Master's thesis
Year: 2009
Downloads: 360
Quote: 7
Read: Download Dissertation

Abstract


As key parts of large complete sets of equipment, heavy forgings have played important roles in national economic constructions and defense development. In addition to producing dimensional satisfactory forgings, the research on upsetting process pays greater attention on modification of inner defects, improvement of material tissue as well as creating favorable mechanical conditions which is able to prevent new fractures or inclusion-induced cracks. As basic forging techniques, upsetting can eliminate void defects so that the mechanical performance, inner quality and carrying ability of materials will be greatly improved. The law of void evolution, criterion of void closure and factors which affect void closure are revealed in this paper. The main work is as follows:1) The law of void evolution and factors which affect void closure were investigated based on Gurson model which comes from Meso-mechanics. The criterion of void closure was also put forward. 2) The constitutive relationship of Gurson model and the update algorithm were studied and implemented through subroutine Hypela which defines the material property of porous material and facilitates the numerical simulation.3) The simulation results of artificial model and Gurson model were compared. It is found that infinite hydraulic stress or equivalent strain is required when Gurson Model is employed to realize void closure of materials. However, such condition does not conform to reality. This paper obtained modified parameters of Gurson Model by Orthogonal experimental design and simulation under different sampling parameters through embedded subroutine. The modified Gurson model can be applied to simulate void volume variation in heavy forgings. The results demonstrate that the void volume change ratios are quite close to those obtained by artificial models, which implies that the predictions of void closure are greatly improved. It is also found that void closure in the center is the easiest one to achieve while the difficulty increases as it approaches the surface. The harder the matrix material, the worse the void closure degree will be.4) By setting tiny artificial voids inside lead samples whose recrystallization temperature equates to room temperature, the criterion of void closure is verified by upsetting experiment. The void volume change ratios obtained from physical experiments are in agreement with those from numerical simulations.

Related Dissertations

  1. Overloaded forging manipulator gripping contact force and dynamic characteristics of,O342
  2. Study on Characteristics of Heavy Forging Material 30Cr2Ni4MoV Steel in Hot Deformation,TG142.15
  3. Critical Techniques of Image Processing for Dimensional Measurement of Hot Forgings,TP391.41
  4. 316LN stainless steel forging Crack analysis and process control,TG316.192
  5. Simulate the Clinching Process and Predict the Strength of Clinching Joint Based on Gurson Model,U465
  6. Heavy forging manipulator clamping device clamping contact force Modeling and Optimization,TP242
  7. Study on the Bonding Process of Inner Void Defects in Heavy Forging at High Temperature,TG316
  8. Research on Closure of Void Defects in the Forgings,TG316
  9. Study on Concave Anvil Cogging,TG316
  10. Cast magnesium alloy plasticity - creep interaction damage constitutive model and its application,TG136.1
  11. A Research on Calculation and Optimization Method for Noise Control in an Axial Fan of CPU Cooler of PC,TP332
  12. Study on Friction Wear Propertiies of Alloy Materials under the Low Stress Scratch Abrasion,TG115.58
  13. Section Optimum Analysis of Thin-Walled Compressive Bar Based on Orthogonal Experimental Method,TU311
  14. Dynamic Simulation of Shear’s Conical Pick Cutting Process,TD421.6
  15. Preparation Technology and Quality Standards Establishment of the Compound Radix Arnebiae Oil,R286
  16. Injection Molding Simulation Analysis and Optimization of Process Parameters Orthogonal,TQ320.662
  17. Varied Depth Metering Channel Screw Research,TQ320.5
  18. Structure Design and Mixing Performance of Gas Pre-Distributors for Flue Gas Denitrification Reactors,X701
  19. Research and Application of Web-Testing,TP311.52
  20. Inverstigation of Abstraction Technology and Gastroenteritis Urativeeffect of Flos Chrysanthemi Indici,R284

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal pressure processing > Forging, forging and blacksmith > Forging process
© 2012 www.DissertationTopic.Net  Mobile