An Experimental Modelling and Numerical FE Analysis of Steel-Strip Ironing Process
This paper deals with analysis of steel strip ironing using experimental modelling and numerical FE simulation. Since both approaches are complementary to each other, numerous results were obtained that enable complete analysis of the processes with in deformation zone. Device for modelling of strip ironing has been developed for experimental testing. Die cone angle, holding force, contact friction conditions on the die and the punch side were varied, due to easily replace able working elements of the device. Friction coefficient values used in numerical FE simulations were determined based on measured values of forces on die and punch, as well as forming load on machine. Experimentally obtained results were confirmed by FE analysis that provided additional information about physics of the process itself within deformation zone. Presented research results point to coherent influences of process factors on tensile wall stress values, which represents key indicator for efficiency of forming, resulting in recommendations for efficient process management.
NUMERICAL MODELING OF IRONING PROCESS
Based on comprehensive experimental research and physical modeling of ironing, and detailed study of the material characteristics of the work piece and tool, as well as investigation of the contact friction conditions and measuring temperature generated by this contact friction, we were able to conduct a set of "numerical experiments" using finite element method implemented in the software Simufact.forming. The goal of numerical modeling was to use 3D visualization of the process, especially in deformation zone, to present strain, stress, velocity, and temperature fields which will enable more detailed analysis of the physics of the process. For that purpose a non- linear FE approach is applied, using solid 3D finite elements, which are optimized for metal forming simulations. This allows obtaining accurate simulation results with the evaluation of changes in the sheet thickness, the effects of residual stress and recurrent elastic strains. Numerical modeling of the process, as well as results of FE analysis have allowed us to obtain important information about the ironing process such as the stress at the wall, strains, deformation forces, generation of temperature in the work piece as a result of plastic strains and the influence of contact friction and transfer of this temperature it to the die. All of these output parameters are evaluated depending on the angle of the die, the forces on the holder, lubrication conditions and the strain rate, analogous to the plan of experiments in physical modeling.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.