Xueyu Ruan

A feasible approach to the integration of CAD and CAPP

Although current CAD systems are declared to be feature-based, in fact, the so-called feature is just a modeling macro or menu name such as Protrusion, Revolution, Cutout, Block, etc., instead of a design feature or manufacturing feature in accordance with engineering practice. Consequently, product model data insufficiency and incompatibility between varieties of application systems are still the major barriers to system integration, especially the integration of design and process planning. This paper proposes a practical solution for a bi-directional integration of CAD and CAPP on the platform of commercial CAD systems. The key techniques such as feature recognition and conversion, feature parameter and constraint extraction, feature tree reconstruction, technical information processing, process planning, automatic process drawing marking and 3D material stock CAD model generating are discussed. And the extracted features and their related technical information and knowledge are encapsulated together with the geometry-oriented CAD model to form an integrated product information model to facilitate effective integration with the downstream activities. The integrated CAD/CAPP system is implemented on a commercial CAD package, UGS/SolidEdge. A case study and industry implementation illustrate the feasibility of the approach proposed.

Study of workability limits of porous materials under different upsetting conditions by compressible rigid plastic finite element method

Workability limits must be considered when designing powder metallurgy (PM) forging processes. This research successfully applied the general upsetting experiment method to the deformation of porous materials. Based on the plastic theory of porous materials, the compressible rigid plastic finite element method is used to simulate the deformation processes of cold upsetting of disks and rings for porous metal materials with a full account of contact friction boundary conditions, the height-to-diameter ratio, the initial relative density, and the die and workpiece geometry. Furthermore, a successful analysis of the cold forging process results in the prediction of the stress, the strain, and the density field. By coupling with the ductile fracture criterion, which is a strain-based criterion obtained by Lee and Kuhn, possible defects leading to material failure have been checked. This research reveals that larger height to diameter and a lesser friction factor can delay the local strain locus to intersect with the Lee and Kuhn’s fracture line and restrain formation of the surface crack. Meanwhile, it reveals that the initial relative density has only a very small influence on the strain to fracture in compression, and it shows the forming behavior of the ring and disk with the curved die. According to Lee and Kuhn’s results, the calculated results agree well with the experimental results.

Application of Six Sigma Robust Optimization in Sheet Metal Forming

Numerical simulation technology and optimization method have been applied in sheet metal forming process to improve design quality and shorten design cycle. While the existence of fluctuation in design variables or operation condition has great influence on the quality. In addition to that, iterative solution in numerical simulation and optimization usually take huge computational time or endure expensive experiment cost In order to eliminate effect of perturbations in design and improve design efficiency, a CAE‐based six sigma robust design method is developed in this paper. In the six sigma procedure for sheet metal forming, statistical technology and dual response surface approximate model as well as algorithm of “Design for Six Sigma (DFSS)” are integrated together to perform reliability optimization and robust improvement. A deep drawing process of a rectangular cup is taken as an example to illustrate the method. The optimization solutions show that the proposed optimization procedure not only impro...

Dynamic Recrystallization Behavior of Microalloyed Forged Steel

The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223–1 473 K and a strain rate of 0.01–5 sΩ1. Activation energy was calculated to be 305.9 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the Zener-Hollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.

Applying case-based reasoning to cold forging process planning

Abstract On the basis of the practical situation of cold forging process planning, the disadvantages of a rule-based solution are discussed, and a case-based reasoning-based cold forging process planning (CFPP) system model is proposed. Several key problems involved are analyzed, among which a feature-based part representation scheme and a two-level retrieval mechanism are introduced to solve the problems of case representation and case retrieval. It is established in this paper that case-based reasoning-based CFPP is a promising technology for both long-term research and the promotion of efficiency for current cold process planning systems.

Simulation of sheet metal forming by a one-step approach: choice of element

Abstract Based on a one-step simulation algorithm and the program developed, a new finite element approach is introduced for the direct prediction of blank shapes and strain distributions for desired final shapes in sheet metal forming. In the numerical simulation, the choice of optimal element plays an important role and is related to the accuracy and effectiveness of solving the problems. Since a one-step approach needs to predict the initial blank shape and the thickness distribution in a deformed part rapidly, the application of the DKT shell element including bending effects is preferable because of its simplicity and effectiveness. As a result, new and compact formulations of this element are given in this paper. Formulations of a one-step simulation are also revised. Results from the deep drawing of square and cylindrical cups using the DKT shell and membrane element are compared with the available experimental data.

Simulation and fracture prediction for sintered materials in upsetting by FEM

Abstract Experiments dealing with the upsetting of sintered materials have resulted in the determination of a forming limit in terms of the local compressive and tensile strains. As the specimen is compressed, a plot of tensile strain versus compressive strain can be made. Fracture occurs when the strain path intersects the forming limit. Once the fracture locus is defined by an experimental method, it is possible to use the Finite Element Method to determine if some upsetting operation will exhibit a free surface crack during a deformation process. In this study, a finite element program has been developed to analyze the deformation processes of sintered metals in upsetting. At the same time, the effects of lubrication, height to diameter ratio, initial relative density, die shaping and preform shape on the forming limit of PM products are investigated. The locus strains are then calculated and possible defects leading to material failure are checked. The calculated results agree well with the experimental results.

MODELING OF MICROSTRUCTURAL EVOLUTION IN MICROALLOYED STEEL DURING HOT FORGING PROCESS

The microstructural evolution of microalloyed steel during hot forging process was investigated using physical simulation experiments. The dynamic recrystallized fraction was described by modifying Avramis equation, the parameters of which were determined by single hit compression tests. Double hit compression tests were performed to model the equation describing the static recrystallized fraction, and the obtained predicted values were in good agreement with the measured values. Austenitic grain growth was modeled as: D i n c 5 = D 0 5 + 1.6 × 10 32 t ⋅ exp ( - 716870 RT ) using isothermal tests. Furthermore, an equation describing the dynamic recrystallized grain size was given as D dyn = 3771·Z −0.2 . The models of microstructural evolution could be applied to the numerical simulation of hot forging.

Defect prediction during conform process by FEM

Abstract On the basis of the rigid viscoplastic FEM theories, a surface defect prediction method for plastic forming process by FEM numerical simulation has been deeply studied in this paper. Some technical treatments and algorithms of defect prediction are proposed. Using this method, the processes of defect initiation and development during CONFORM process are predicted successfully, and some critical technological parameters are obtained. Therefore, it is also an extension for application fields of rigid viscoplastic FEM to predict technology defect.

A web-based cold forging process generation system

Abstract The process plan is one of the most important stages of cold forging design. Web-based and knowledge-integrated engineering design is now springing up and widely used in engineering fields. This research proposes a web-based intelligent cold forging process plan and conducts research on related key technologies which lead to develop a prototype system. The technologies used in the system are discussed in detail. Through the use of web and intelligent approach, the cold forging knowledge can be effectively incorporated into the process generation system and a web-based cold forging process generation system can be implemented.