Thermal stresses during electro-chemical spark machining
The high temperature distribution generated during electro-chemical spark machining (ECSM) results in large localised thermal stresses in a very small heat affected zone. These thermal stresses can lead to micro-cracks and a decrease in strength and fatigue life of the components. A finite element model is developed to estimate the temperature distribution and thermal stresses due to a single spark (Gaussian distributed heat flux) and within the zone of influence of a single spark. Firstly, the finite element based (FEM) code is developed to estimate temperature distribution in the workpiece due to a single spark and, based on this temperature distribution, thermal stresses are calculated. Thermal stress analysis shows high temperature gradient zones and the regions of large stresses where, sometimes, they exceed the material yield strength.
Experimental Set Up to Improve Machining Performance of Silicon Dioxide (Quartz) in Magnetic Field Assisted TW-ECSM Process
In the present scenario, machining of the pioneering engineering materials such as various ceramics and composites which possess high hardness, brittleness, strength and electrically insulated becomes very difficult. This study focuses on the development of magnetic field assisted traveling wire electrochemical spark machining (MF-TWECSM) process set up and its utilization for the machining of electrically insulated materials. TW-ECSM process is a combination of the Wire-EDM and ECM processes. In this process, effects of the electrochemical reaction and electric spark are responsible for the material removal from the workpiece. Quartz found to be suitable as work material due its high hardness, good chemical stability and piezoelectric properties. Magnetic field has been applied during the machining for better circulation of the electrolyte during experimentation. Enhanced electrolyte circulation improves the efficiency of the process resulting in higher material removal rate (MRR) of the work material and reduction in the discharge current during experimentation. The improvement in MRR with magnetic field was found in the percentage range of 9% to 200% during experimentation. For the very first time, a brass wire with diameter 0.1 mm has been used during TW-ECSM process.
A New Vacuum Pressure Infiltration CFRP Method and Preparation Experimental Study of Composite
In order to prepare a carbon-fiber-reinforced polymer composite (CFRP) with ideal microstructure and properties, a new vacuum pressure infiltration CFRP method is proposed based on an analysis of existing CFRP preparation process methods. Research on composite material preparation systems was carried out by using this new method principle. The system mainly includes a fiber pre-forming module, a vacuum heating infiltration module, a hot-press curing molding module, and a data acquisition control module. Under the conditions of natural curing at 0 MPa + 6 h + 25 °C, vacuum heating curing at –0.05 MPa + 30 min + 80 °C, and hot-press curing at 0.7 MPa + 5 min + 50 °C, a two-dimensional (2D) CFRP with excellent microstructure and properties was successfully prepared. Observing the microstructure of the prepared composite material, it can be found that the inside of the composite material was sufficiently and uniformly infiltrated, and common preparation defects such as holes and delamination were effectively controlled. Through the performance test, the bending strength of the material reached 790 MPa.