Papers by Keyword: Metal Foil

Abstract: Metal foil strain gauges are most widely used for the stress analysis in engineering structures. Typical strain gauge system includes strain sensitive grid, carrier material, and adhesive layer. Strain measurement from the strain gauge is partially affected by carrier and adhesive materials and their thickness. In the present work, a Finite Element Model is developed in order to study the effect of both adhesive layer and carrier thickness on strain measurements while using strain gauges. To understand the behavior of the adhesive material, mechanical characterization is done on bulk adhesive specimen. Finite Element Analysis (FEA) is carried out with different materials namely epoxy and polyurethane. Initially a single element foil loop is considered for the analysis and further this is extended to metal foil strain gauge with nine end-loops. Finally, the strain variation through thickness of adhesive layer, carrier and strain sensitive grid is obtained from FEA. The results thus obtained are compared with analytical results from Basic Strength of Materials approach.

Abstract: Strain measurement from the strain gauge is partially affected by carrier and adhesive materials and their thickness. Effect of adhesive layer thickness has been addressed in this paper. Well characterized tensile experiments have been conducted using Al 6061-T6 specimens attached with strain gauges at mid length of the specimen and strain gauges are attached with different materials namely epoxy and polyurethane to understand the effect of adhesive layer thickness in strain measurement. The strain at a location has been noted for one particular adhesive layer thickness value (0.13 mm) and similar experiments have been carried out with different adhesive thickness values (0.16 mm, 0.18 mm and 0.26 mm). The results obtained from experiments have been compared with analytical results from Basic Strength of Materials approach. Good agreement is seen between the experimental and analytical results. It has been observed that the thickness of the adhesive layer plays significant role for getting accurate strain.

Abstract: Micro metal forming with metal foils is one of the promising approaches to fabricate micro parts. In this study, a finite element (FE) model for metal foil considering material inhomogeneity due to different flow stresses for each crystal grain to predict free surface roughening and necking behavior is suggested. Material used is pure copper C1020-O, pure aluminum 1N30-O and pure titanium TR270C-O with thickness of 0.05mm. Material inhomogeniety parameter of variation in α value is determined by parameter fitting between uni-axial tensile test and FE analysis considering material inhomogeneity under uni-axial tensile state. Standard deviation σ_sd of variation in α value of 0.28 for C1020-O is obtained by parameter fitting process. In addition, free surface roughening behavior is observed by FE analysis considering material inhomogeneity and confocal laser microsope. As a result, the increase in surface roughness with uni-axial tensile deformation can be observed for both FE analysis and experiment. In addition, it is considered that the generation of concave parts in free surface roughening is due to grains with low flow stress by quantitative measurement of FE analysis and confocal laser microscope. Surface roughening behavior of FE analysis considering material inhomogeneity is in good agreement with that of experimental results. Thus, the validation of FE model considering material inhomogeniety for metal foils can be verified. Furthermore, the effect of material properties for metal foils such as grain size, material inhomogeneity parameters and strain hardening sensitivity on necking behavior is investigated. As a results, it is found that the ratio of surface roughening to thickness strongly affects necking behavior for metal foil. In particular, in case of large n-value, the concave part generated by surface roughening during plastic deformation would cause the onset of necking for metal foils. Therefore, it is found that the factor of surface roughening is very strong in micro metal forming with metal foils.

Abstract: Characteristics of slide-bend forming were investigated. In this process, foil specimens can be bent to various shaped products by indenting and sliding a tool. The effects of the tool indentation load, the foil thickness and the number of slide repetition on the bending angle were examined experimentally for three kinds of foil materials. In addition, the deformation of bent region was examined using a rigid-plastic finite element analysis. Bending angle increased with increasing the indentation load or decreasing the foil thickness. When the number of slide repetition increased, the bending angle increased slightly. The slide repetition can be effective for adjusting bending angle slightly. By sliding a thin edge-shaped tool relative to the foil specimen, bending angle and radius of curvature of specimens can be controlled freely.

Abstract: This study focuses on the surface deformation of thin metal foils caused by friction. To clarify the effect of the relative ratio of surface plastic region to the foil thickness on global deformation behavior, strip drawing tests for ultra thin metal foil with 20μm and 100μm thickness were conducted As a result, different surface deformation and elongation behavior under the same friction condition were observed in different thicknesses. Aided by finite element analysis of the friction test, the contribution of the deformation caused by friction to the foil elongation was investigated and the importance of the friction on material deformation in metal foil forming was demonstrated.