A PC-based system integrating CMM and CAD for automated inspection and reverse engineering

A personal computer (PC)-based system integrating a manual CMM and a CAD system has been developed for on-line capture of 3D point data, resulting in the automation of the inspection process. The sequence of steps taken to measure a master component using the CMM is stored in a measurement program in teach mode and replayed for repetitive measurement of a batch of identical components in the replay mode. The measurement program guides the CMM operator regarding the geometric entity to be measured, the number of points to be input and the direction to be followed for taking the points on the CMM. The operator has simply to follow the sequence displayed on the computer screen. The program automatically computes the dimensions and the deviations from the corresponding dimensions of the master component. The 3D measurement data from the CMM are transferred to a CAD system in real time. Programs have been developed to create 3D cubic splines and surfaces from the 3D point data taken on the CMM. The full features of the CAD software can be used to manipulate the 3D point data for CAD applications.     

Fabrication and testing of Al-SiCp composite valve seat inserts

In the present work Al-SiC_p composite valve seat inserts with 10, 15, 20, and 25 wt?% of SiC_p were fabricated through die compaction of powders and subsequent sintering at 580 °C. Valve seat inserts were also fabricated through the gravity die casting process. The Rockwell hardness, density, radial crushing load and surface roughness of the Al-SiC_p composites (with different wt % of SiC_p) and steel valve seat inserts presently used in engines were measured and compared. The Rockwell hardness and radial crushing load for Al-15, 20, and 25wt% of SiC_p composite valve seat inserts were higher than that of the steel valve seat inserts presently used in engines. The microstructure of the cast and powder metal Al-SiC_p composites was also studied.     

Development of abrasive cut-off wheel having side grooves

The abrasive cut-off wheel fails prematurely during the routine sectioning of workpiece, which may cause injury to the operator. One of the major reasons of premature failure is the improper mixing of the abrasive mixture. In order to provide strength to the wheel, it was reinforced by woven roving type glass fiber and the abrasive mixture was ball milled. Cutting zone temperature becomes high during the cutting operation, which may cause thermal damage to the workpiece and debonding of abrasive from the wheel. It is very difficult to supply the cutting fluid to the cutting zone in order to reduce the temperature. New types of abrasive cut-off wheels were developed, which have radial passages on their surfaces to supply the cutting fluid to the cutting zone. Performance of the wheels was compared and the mechanical strength of the wheel material was tested.     

High Performance Lithium‐Ion Batteries Using Layered 2H‐MoTe2 as Anode

The major challenges faced by candidate electrode materials in lithium‐ion batteries (LIBs) include their low electronic and ionic conductivities. 2D van der Waals materials with good electronic conductivity and weak interlayer interaction have been intensively studied in the electrochemical processes involving ion migrations. In particular, molybdenum ditelluride (MoTe₂) has emerged as a new material for energy storage applications. Though 2H‐MoTe₂ with hexagonal semiconducting phase is expected to facilitate more efficient ion insertion/deinsertion than the monoclinic semi‐metallic phase, its application as an anode in LIB has been elusive. Here, 2H‐MoTe₂, prepared by a solid‐state synthesis route, has been employed as an efficient anode with remarkable Li⁺ storage capacity. The as‐prepared 2H‐MoTe₂ electrodes exhibit an initial specific capacity of 432 mAh g^?1 and retain a high reversible specific capacity of 291 mAh g^?1 after 260 cycles at 1.0 A g^?1. Further, a full‐cell prototype is demonstrated by using 2H‐MoTe₂ anode with lithium cobalt oxide cathode, showing a high energy density of 454 Wh kg^?1 (based on the MoTe₂ mass) and capacity retention of 80% over 100 cycles. Synchrotron‐based in situ X‐ray absorption near‐edge structures have revealed the unique lithium reaction pathway and storage mechanism, which is supported by density functional theory based calculations.     

Numerical Modeling of Exit-Ply Delamination During Drilling of CFRPs Considering Thermal Effects

Abstract

A finite element (FE) model for exit-ply delamination during drilling carbon fiber reinforced polymers (CFRPs) laminates is presented. The current FE model is developed to predict critical thrust force at the onset of delamination for 1 and 2 plies under the twist drill for various cutting temperatures. The interface behavior for delamination onset is modeled using surface based cohesive zone model (CZM). The numerical predictions for critical thrust force are compared with experimental thrust forces for various number of plies under the twist drill over a range of cutting temperature. Thrust force predictions were found to match with experimental data.     

A review of non-destructive techniques used for mechanical damage assessment in polymer composites

Polymer composite materials are being increasingly used in primary load-bearing structures in several advanced industrial fields such as aerospace vessels, railway wagons and mega-scaled wind turbines where detection of subcritical damage initiation can significantly reduce safety issues and maintenance costs. It is therefore crucial to inspect these composite structures in order to assess their structural health and to ensure their integrity. Non-destructive testing techniques (NDT) are used for this purpose, making it possible to monitor mechanical damage of composite materials under in situ or ex situ service conditions. This paper reviews the capabilities of the most common NDT techniques used to inspect the integrity of composite materials. Each technique has a detection potential and cannot allow a full diagnosis of the mechanical damage state of the material. Thus, depending on the occurring damage mechanism and the conditions of use, one technique will be preferred over another, or several techniques should be combined to improve the diagnosis of the damage state of the structures.     

Thermal Decomposition Study on CuInSe$$_{}$$ Single Crystals

The thermal analysis of the chemical vapor transport (CVT)-grown \(\hbox {CuInSe}_{2}\) single crystals was carried out by recording the thermogravimetric, differential thermogravimetric and differential thermal analysis curves. All the three thermo-curves were recorded simultaneously by thermal analyzer in the temperature range of ambient to 1080 K in inert nitrogen atmosphere. The thermo-curves were recorded for four heating rates of 5 K \(\cdot \,\hbox {min}^{-1}\), 10 K \(\cdot \,\hbox {min}^{-1}\), 15 K \(\cdot \,\hbox {min}^{-1}\) and 20 K \(\cdot \,\hbox {min}^{-1}\). The TG curve analysis showed negligible mass loss in the temperature range of ambient to 600 K, stating the sample material to be thermally stable in this temperature range. Above 601 K to the temperature of 1080 K, the sample showed continuous mass loss. The DTG curves showed two peaks in the temperature range of 601 K to 1080 K. The corresponding DTA showed initial minor exothermic nature followed by endothermic nature up to nearly 750 K and above it showed exothermic nature. The initial exothermic nature is due to absorbed water converting to water vapor, whereas the endothermic nature states the absorption of heat by the sample up to nearly 950 K. Above nearly 950 K the exothermic nature is due to the decomposition of sample material. The absorption of heat in the endothermic region is substantiated by corresponding weight loss in TG. The thermal kinetic parameters of the CVT-grown \(\hbox {CuInSe}_{2}\) single crystals were determined employing the non-mechanistic Kissinger relation. The determined kinetic parameters support the observations of the thermo-curves.     

Assessment of triboelectricity in colossal-surface-area-lanthanum oxide nanocrystals synthesized via low-temperature hydrothermal process

Journal of Materials Science: Materials in Electronics - Triboelectric nanogenerators (TENGs) have marked their applications in various fields, most importantly, in medical devices. The electrical...     

Mixed Lead Halide Passivation of Quantum Dots

Infrared‐absorbing colloidal quantum dots (IR CQDs) are materials of interest in tandem solar cells to augment perovskite and cSi photovoltaics (PV). Today's best IR CQD solar cells rely on the use of passivation strategies based on lead iodide; however, these fail to passivate the entire surface of IR CQDs. Lead chloride passivated CQDs show improved passivation, but worse charge transport. Lead bromide passivated CQDs have higher charge mobilities, but worse passivation. Here a mixed lead‐halide (MPbX) ligand exchange is introduced that enables thorough surface passivation without compromising transport. MPbX–PbS CQDs exhibit properties that exceed the best features of single lead‐halide PbS CQDs: they show improved passivation (43 ± 5 meV vs 44 ± 4 meV in Stokes shift) together with higher charge transport (4 × 10^‐2 ± 3 × 10^‐3 cm² V^‐1 s^‐1 vs 3 × 10^‐2 ± 3 × 10^‐3 cm² V^‐1 s^‐1 in mobility). This translates into PV devices having a record IR open‐circuit voltage (IR V_oc) of 0.46 ± 0.01 V while simultaneously having an external quantum efficiency of 81 ± 1%. They provide a 1.7× improvement in the power conversion efficiency of IR photons (>1.1 µm) relative to the single lead‐halide controls reported herein.     

A robust software watermarking framework using shellcode

Multimedia Tools and Applications - Watermarks have long been applied to ensure the authenticity of media contents. Computer software is an intellectual outcome in the digital domain. Therefore, it...