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 Investigations and Multi-response Optimization of Silicon Dioxide (Quartz) Machining in Magnetic Field Assisted TW-ECSM Process
Travelling wire electrochemical spark machining (TW-ECSM) has the potential for the machining of advanced non-conducting materials like glass, quartz, silicon nitride, various composites and ceramics. In the present work, experimental investigations have been conducted on the magnetic field assisted travelling wire electrochemical spark machining (TW-ECSM) process. In this technique, a magnetic field has been introduced in the TW-ECSM process in order to improve the machining performance in terms of improved material removal rate (MRR) and reduced surface roughness (Ra) of non-conducting materials. Material removal rate (MRR) and surface roughness (Ra) were selected as the responses during the experimentation. The experimental results revealed that the magnetic field assisted approach gives reduced values of Ra and increased MRR when compared to the TW-ECSM process. The minimum and maximum values of surface roughness and MRR were found to be 7.42 µm and 0.19 mg/min with magnetic field assisted TW-WCSM process respectively. The optimization function has been developed to minimize Ra and maximize MRR for obtaining the optimum process parameters.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.