Zhong Yi Cai

FE simulation of shape accuracy using the Multi-Point Stretch-Forming process

Multi-Point Stretch Forming (MPSF) is a new technique to form aircraft outer skin parts. In MPSF, the sheet metal is formed over a discontinuous surface of discrete stretching die. The size of punch element of multi-point die, the thickness of sheet metal and the thickness of elastic cushion are the important factors to affect the accuracy of MPSF part. In this paper, a series of numerical simulations on MPSF processes were carried out, and the shape error and the non-uniformity in thickness distribution of MPSF part were analysed. The results show the influences of the punch element size, the sheet metal thickness and the elastic cushion on forming results.

Numerical Simulation of Different Clamping Modes on Stretch Forming Parts

Three clamping devices of stretch forming machine were introduced, and the corresponding finite element models of the spherical parts were built by finite element software, the strain and thickness distribution of the forming parts were comparatively analyzed. The simulation results show that strain and thickness distribution of the forming parts with the multiple discrete gripper clamping mode are well-proportioned, its forming quality gets better than that with the whole flat gripper and adjustable curved gripper clamping modes. The experiment was performed and a typical spherical parts was formed with the multiple discrete gripper clamping mode. The experimental results are in good agreement with simulation results, which proves feasibility and practicability of the multiple discrete gripper clamping device of stretch forming machine.

Numerical Investigation on the Process of Stretch-Forming Based on Discretely Loading for Spherical Sheet Metal Parts

Stretch-forming based on discretely loading is a new process for manufacturing three-dimensional sheet metal part, the stretching load is applied at discrete points on the two ends of sheet metal, by controlling the loading trajectory at each discrete point, an optimal stretch-forming process can be realized, and the formed surface with the strains and stresses more uniformly distributed are obtained so that the forming defect can be avoided. The numerically investigated results on the stretch-forming process of spherical sheet metal part show that, comparing with the traditional stretch-forming, the equivalent strain in the new process is reduced by approximately 30% and equivalent stress reduced by 10%, the range of the strain and stress distributions are reduced by approximately 30%.

Analytical Analysis of Three-Roll Bending of Thin-Plate

In this paper, an analytical solution for the three-roll bending process of thin-plate was presented. Based on the theoretical analysis on continuously loading and unloading deformation of the plate during roll-bending, the curvature equations governing the bending behavior of thin-plate were set up and then solved by integration. Combing the solutions with the geometrical relationships in three-roll bender, the deflection and bending angles occurring during the steady continuous bending period were obtained by an iterative scheme. Numerical examples were given to illustrate the application of the solutions. The variation of the top roll’s position with the intended bend radius, the curvature and deflection distributions on bent plate were shown in graphically and discussed.

Research on Continuous Multi-Point Forming technology for three-dimensional sheet metal

Continuous Multi-Point Forming (CMPF) is an advanced sheet metal forming technology. It can manufacture three-dimensional surfaces of different shapes by adjusting the curvatures of flexible rollers and displacement of upper flexible roller. CMPF experimental equipment was designed. Finite Element Analysis (FEA) model was established. To show the characteristics of CMPF, conventional roll bending was compared with it. Process of CMPF and action force between flexible rollers and sheet metal were researched by numerical simulation method; simulation results can offer assistance to optimise the design of CMPF equipment. Spherical, saddle and twisty surfaces were simulated and their experimental results were presented.

Numerical Analysis of the Multi-Point Stretch Forming Process of Aircraft Outer Skin Part

As a flexible manufacturing technique, Multi-point stretch forming (MPSF) is a suitable method for forming aircraft outer skin part. The traditional solid stretching die is replaced by the discrete multi-point die (MPSD), and the sheet metal is stretch-formed over the MPSD generated by serial adjusting mode or parallel adjusting mode. The MPSF can be used to form the parts of different shape and reduce the cost and leading time of stretching die fabrication for aircraft outer skin part. A series of numerical simulations on typical MPSF processes of aircraft outer skin part were carried out. The thickness of elastic cushion and free length are important factors to influence on the stretch forming results of stretch-formed parts. The numerical simulation results show that the thicker the elastic cushion is, the more valid the dimple will be suppressed .The longer the free length is, the easier the wrinkle will be brought.

Studies on Curing Kinetics of Epoxy Resin / Modified Amine System

In this paper, E51 epoxy resin with 1050B modified polyamine and 1055B Modified polyamide was studied by non-isothermal DSC, and then we use Kissinger and Ozawa methods to calculate the activation energy and reaction order n, obtained its curing reaction kinetic model, and the reaction is a complicated reaction, at last we determine the E51 epoxy resin and 1050B modified polyamine / 1055B Modified polyamide curing conditions.

Research on Transition Zones of Spherical Surface Parts in 3D Rolling Process

3D rolling is a novel technology for three-dimensional surface parts. In this process, by controlling the gap between the upper and lower forming rolls, the sheet metal is non-uniformly thinned in thickness direction, and the longitudinal elongation of the sheet metal is different along the transverse direction, which makes the sheet metal generate three-dimensional deformation. In this paper, the transition zones of spherical surface parts in 3D rolling process are investigated. Spherical surface parts with the same widths but different lengths are simulated in condition of the same roll gap, and their experimental results are presented. The forming precision of forming parts and the causes of transition zones in the head and tail regions are analyzed through simulated results. The simulated and experimental results show that the lengths of transition zones of spherical surfaces in the head and tail regions are fixed values in condition of the same sheet width and roll gap.

Study on Anti-Freezing Performance of Organic Fluorine Siloxane Nano Coating

a low surface energy coating with a long chain fluorine siloxane is prepared, and the performance in anti-freezing adhesive is studied. It is determined that the optimum proportion of (Heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane (FAS) and SiO2 nanopowder are 1.1% and 1.6%,respectively. the times of coating bear pendulum impact is least in this proportion. the conclusion is that bionic superhydrophobic coating plays a certain guiding role on solving material surface frozen sticky problem.

Modeling and Simulation of Continuous Flexible Roll Forming Process

The continuous flexible roll forming process is a novel sheet metal forming technique for effectively manufacture of three-dimensional surface parts. In this study, two types of finite element (FE) models were developed under the ABAQUS/Explicit environment. The difference of the two models is that the rolls are defined as discrete rigid bodies in model No.1 and are deformable in model No.2. An experiment was carried out using the continuous sheet metal forming setup. The comparison of the numerical computation results with the experimental results shows that the model No.2 can be used for the shape prediction of continuous flexible roll forming process well.