Advanced Materials Research Vols. 189-193

Abstract: This paper deals with minimizing warpage and sink mark depth in injection-molded thermoplastics components. Automobile glove box housing trim assembled on the instrument panel was chosen as an experimental model. In these experiments, the Taguchi method and FE analysis were used to research minimizing the warpage and sink mark depth. The most influential factor was found out by using Taguchi method. Through interaction parameters experiments put into practice through Moldflow software, the interaction between each factors has been researched. The optimization packing condition for minimization of the warpage and sink mark depth was designed.

Abstract: Two-dimensional (2D) random cell models composed of circular cells with different sizes are developed to simulate the microstructure of silicone rubber foams. The two-parameter Mooney-Rivlin strain energy potential model is employed to characterize the hyperelasticity of the solid of which the foams are made. Finite element method is used to simulate the large deformation of the foams. Predicted uniaxial compressive stress-strain curves exhibit universally three deformation regions: an initial linear-elastic response, an extended plateau region, and a final densification stage as cell collapsing. It is also found that with the foam relative density increasing, the initial linear-elastic region is found to extended, the buckling plateau section becomes indistinctive, and final densification stage is hastened.

Abstract: For ring rolling without axial rolls, how to effectively suppress axial spread has become an important subject. In the paper, a reliable coupled thermo-mechanical three-dimensional (3D) finite element (FE) model for hot rolling of large rings is developed. Spread evolution of titanium alloy large rings with different sizes are explored and compared based the developed model. The main results show that (1) the spread in a ring takes on an axisymmetric distribution after the first revolution of the ring. (2) with the equivalent ratio of feed amount per revolution decreasing, the peak spread transfers from the outer layer to the inner layer for rings with different sizes.

Abstract: Using the method of numerical simulation and the AnyCasting software, the simulation for SDAS of Al-Mg alloy wheels for low pressure casting is studied. The simulation model is established and the effects of preheating temperature, melt pouring temperature and cooling water pipes on SDAS in the low pressure casting process was founded. The results show that, SDAS presents linear variation with the increase of preheating temperature and pouring temperature; opened cooling pipes make SDAS smaller. The practice of simulating casting is verified by experiments, and test results and simulation results were consistent.

Abstract: Viscosity takes an important role in filling simulation in injection molding. This paper presents a computational approach to estimate the 7 parameters of Cross-WLF viscosity model based on nonlinear fitting technology. The numerical strategy is line search. Line search Newton Method is employed here since the Newton direction is the most efficient one. Test case shows its results are of high accuracy and the RMS error between fitting and experimental data is less than 10^-5.

Abstract: Increasing the machining precision of machine tools has imposed higher demands for dynamic characteristics of the key components. Taking the MDH50 precision machining center as a example, this paper established the flexible body of five key components, bed, column, spindle boxes, slipway and worktable, and built the rigid-flexible coupling systems of whole machine, based on the basic theory of multi-body system dynamics. Then the cutting force reference to the actual constraints was applied to the system and the dynamics simulation was carried out. The effect of every component on machining precision was effectively identified. Dynamic stiffness testing of the machine is based of principles of testing the transmission components dynamic stiffness, and further analysis of the each component dynamic stiffness is conducted, which can verify the accuracy of flexible body analysis.

Abstract: Ultrasonic surface rolling processing (USRP) is a surface nanocrystallization method developed recently, which can bring metal surface with superior properties. In order to obtain the material response during USRP, a 3D dynamic finite element model was adopted to study the effects of parameters. This model was validated by experimental results of residual stress. Simulated results indicate that large ultrasonic vibration parameters generate high stress and strain, where static pressure plays a more important role than vibration amplitude. Yet high spindle speed leads to small stress and strain.

Abstract: The thin-walled cavity workpiece with insufficient rigid property is liable to deform during the machining process and the request of accuracy is very strict. The paper takes typical aeronautic aluminum-alloy for example, fixture is an important consideration in the operation. To reveal the influences of locating points, clamping sequence and loading ways on the distortion of thin-walled cavity part, finite element models were established to simulate the clamping operation. The result shows the preferable scheme is that the distance of the clamping locations are far each other, clamping forces are firstly applied on the surface with high rigid and all clamping forces are applied in many steps. The scheme can effectively control the deformation of clamp ,and furthermore improve the machining accuracy.

Abstract: For the large and complicated injection mold, the deformation of mold is one of the important factors to affect the plastic part quality and mold life. However, the accurate prediction of mold deformation is usually difficult because of the no-matching mesh between the part molding analysis and the mold structural analysis. Their analysis results can not be directly imported mutually, which leads to the loading of boundary condition having much obstacles in integrated analysis. To conquer the problem, this paper researches and develops an injection molding simulation system(Z-mold) based on Hele-shaw model, and establishes the data share interface between Z-mold and ANSYS by means of uniform mesh. Based on these studies, this paper carries out the integrated analysis of injection molding and mold. The deformation of mold under the load of the real molding pressure is successfully predicted, which is more accurate than the estimation by use of the empirical formula. This paper’s integrated study possesses great application value.

Abstract: Solder reliability assessments for stacked CSP module based on flexible printed circuit board (FPC) are performed in this research using a 3D global model with constraint equation and two levels submodeling technique. 3D global model with constraint equation(CE) was used to provide real boundary contiditons for 1st level submodeling,and quarter local model used as 2^nd level submodeling was used to address cirtical solder joint failure locations ,to estimate solder reliability for the module and to provide reasonable boundary contiditons for 2^nd level submodeling.slice model used as 2^nd level submodeling was used to study that the effect on the cirtical solder damage parameter under various basefilm material of FPC and geometrical parameters. It is found that thinner CSP die thickness and thinner PCB ,thicker FPC basefilm and FPC adhesive thickness and CSP thickness,and higher solder standoff height, lead to smaller averaged accumulated viscoplastic strain energy density(ΔWavg) and higher fatigue life; It is also figures out,PI and PEN basefilm material lead to smaller ΔWavg and higher fatigue life for the most critical solder than LCP material.Weibull distributions and weibull probaility density function for the module under various FPC baseflim material were obtained,and 63.2% solder joints failure life was used as solder joints reliability assessment for stacked CSP module.