The Manufacturing Research Center at Georgia Tech is addressing both fundamental and practical issues related to the handling of polycrystalline silicon wafers used in the manufacture of photovoltaic ...(PV) cells and modules. As Bernoulli grippers are widely used in the PV industry for handling silicon wafers, this paper focuses on the study of such grippers. The objective of this work is to develop an understanding of the influence of gripper variables and silicon wafer characteristics on wafer deformation and stresses in order to prevent wafer breakage and thereby improve yield. A finite element model has been developed to predict handling stresses based on measured wafer deformation profiles
In recent years, the finite element method (FEM) has become the main tool for simulating the metal cutting process because research based on trial and error is time consuming and requires high ...investment. Early studies were done by different investigators. In this research AISI 52100, hardened steel (62 HRC) was selected for an orthogonal machining process as well as metal cutting simulation using the software DEFORM-2D. This software is based on a forging process and has been adapted to an orthogonal machining process. The results of simulated cutting forces were compared with experimental cutting force data to validate the orthogonal cut simulation. Also, the surface roughness was measured, and the influence of the stress, strain, and temperature on the surface roughness was studied.PUBLICATION ABSTRACT
In recent years, the finite element method (FEM) has become the main tool for simulating the metal cutting process because research based on trial and error is time consuming and requires high ...investment. Early studies were done by different investigators. In this research AISI 52100, hardened steel (62 HRC) was selected for an orthogonal machining process as well as metal cutting simulation using the software DEFORM-2D. This software is based on a forging process and has been adapted to an orthogonal machining process. The results of simulated cutting forces were compared with experimental cutting force data to validate the orthogonal cut simulation. Also, the surface roughness was measured, and the influence of the stress, strain, and temperature on the surface roughness was studied.
The stress test of the COVID-19 pandemic uncovered vulnerabilities in the global supply chain, and subsequent shortages indicate they may not be displaying the robustness needed to cope with the ...increased level of economic activity. But restocking the nation’s shelves for the decades to come will require more than reestablishing logistics—it needs people. It demands renewed investment in the manufacturing and technical workforce and the training of millions of skilled workers required for high-tech manufacturing.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
An experimental study was conducted to examine the material properties and machinability of a silicon carbide (SiC)-filled epoxy conductive tooling system (RP4037 CAST-IT
TM
). Specifically, the ...effects of SiC filler concentration and machining process parameters (cutting speed and feed) on the physical and material properties, resultant cutting force, surface integrity, and tool wear were studied. Machinability evaluation was carried out using the end milling process. The study showed that an increase in filler concentration significantly increased the density, thermal conductivity, resultant machining forces, surface roughness of the machined surface, and tool wear. However, it had insignificant impact on the glass transition temperature, strength, or hardness. A decrease in material strength was observed with increasing cutting speed and feed. Increasing filler concentration was also found to degrade the machined surface morphology. Possible explanations for the observed effects are discussed.
Resonance Ultrasonic Vibration (RUV) metrology offers a sensitive non-destructive real-time solution to silicon wafer crack detection. The stresses generated in the wafers by the handling device used ...in the RUV method may have a significant influence on the effectiveness of this method, particularly for thinner wafers. The handling stresses produced by different designs of the vacuum wafer holders and their effects on the resonance properties of the ultrasonically excited wafer are studied using Finite Element Analysis (FEA) and confirmed by RUV tests. FEA results and RUV experiments show that optimization of the wafer handling stress obtained by redesigning the wafer holder does not alter the resonance frequencies and mode shapes of the wafer significantly compared to the free vibration case. Therefore, it is possible to use RUV approach for crack detection in thin silicon wafers without significant modification.
Differences in microstructures of lead-free solder joints, Sn-Ag-Cu (96.5 wt./3.0 wt./0.5 wt.% SAC-305), made by two different semiconductor packaging processes such as reflow and TCB are discussed. ...Despite the enormous potential for TCB solder bonding process in microelectronic packaging, there has been few studies regarding the comparative analysis on electro-migration (EM) failure mechanism for the reflow process. We have systematically examined the EM-derived failures of the reflow and TCB-processed solder joints and demonstrated a process-structure-property linkage. This study also includes the analysis performed using generalized spherical harmonics (GSH) representation, a statistical and quantitative measure of material crystallographic informatics, which is novel in this field as to analyzing solder joint microstructures.
Dynamic instability in the form of chatter is a highly undesirable phenomenon that occurs during machining, resulting in poor surface finish and reduced tool life. Though analytical models exist for ...identifying conditions that avoid chatter, they do not account for process uncertainties or they require extensive cutting tests. Therefore, an on-line chatter detection algorithm is required to detect chatter before irreversible damage to the cutting tool or workpiece occurs. This paper evaluates the performance of three chatter detection algorithms in detecting chatter in the turning process with the eventual goal of developing embedded sensor-based process monitoring automation. Cutting force data are gathered from a number of turning scenarios with varying workpiece geometries. Of the chatter detection algorithms evaluated, spectral analysis is found to be the most robust and capable of detecting dynamic instability before tool or workpiece damage occurs.
Workpiece fixturing for machining operations often relies on friction to prevent workpiece motion. Since most machining operations involve dynamic loads, a better understanding of the influence of ...such loading on workpiece–fixture contact friction is desirable. This paper presents the results of an experimental investigation of the effects of normal preload force, vibration amplitude and excitation frequency on the static friction between cast aluminum 357 workpiece material and oxide coated AISI 1144 steel fixture material. A friction tester capable of simulating normal and in-plane dynamic loads was designed and built for the study. Response surface analysis of the experimental data reveals that dynamic loading significantly influences workpiece–fixture static friction. Possible explanations for the observed effects are given.
