M.S. Srinath

A novel route for joining of austenitic stainless steel (SS-316) using microwave energy

Material processing through microwaves is a challenging area of research. The present work illustrates an application of the developing technology of joining bulk metallic materials through microwave heating. Stainless steel (SS-316) in bulk form was used as candidate material to be joined. Joining of bulk SS-316 was carried out using a multimode microwave applicator at the frequency of 2.45 GHz and power of 900 W. Joining was effected through fusing and metallurgical bonding of a sandwich layer between the bulk pieces. Heating in the sandwich layer was selectively induced by exposing it to controlled microwave radiation for a predetermined period. The joints were characterized through field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and measurement of Vickers microhardness, porosity, and tensile strength. The FE-SEM study showed that the faying surfaces are well fused and get bonded with base material. Examination of the joint microstructure showed cellular-like growth in the entire joint region. The average Vickers microhardness of the core of the joint area was observed to be 290±14 Hv; however, that in the interface zone was found to be significantly higher (∼420±15 Hv). Precipitation of metallic carbides occurred predominantly in the joint interface region. Porosity measurement in the joint area revealed negligible porosity (0.78 per cent). Evaluation of the tensile properties of the joints showed an ultimate tensile strength of the order of 309 MPa with an elongation of 11.50 per cent.

GSM based Automatic Irrigation Control System for Efficient Use of Resources and Crop Planning by Using an Android Mobile

The greenhouse based modern agriculture industries are the recent requirement in every part of agriculture in India. In this technology, the humidity and temperature of plants are precisely controlled. Due to the variable atmospheric circumstances these conditions sometimes may vary from place to place in large farmhouse, which makes very difficult to maintain the uniformity at all the places in the farmhouse manually. It is observed that for the first time an android phone-control the Irrigation system, which could give the facilities of maintaining uniform environmental conditions are proposed. The Android Software Development Kit provides the tools and Application Programmable Interface necessary to begin developing applications on the Android platform using the Java programming language. Mobile phones have almost become an integral part of human life serving multiple needs of humans. This application makes use of the GPRS (General Packet Radio Service) feature of mobile phone as a solution for irrigation control system. GSM (Global System for Mobile Communication) is used to inform the user about the exact field condition. The information is passed onto the user request in the form of SMS. Drip irrigation is artificial method of supplying water to the roots of the plant. It is also called micro irrigation. In past few years there is a rapid growth in this system. The user communicates with the centralized unit through SMS. The centralized unit communicates with the system through SMS which will be received by the GSM with the help of the SIM card. The GSM sends this data to ARM7which is also continuously receives the data from sensors in some form of codes. After processing, this data is displayed on the LCD. Thus in short whenever the system receives the activation command from the subscriber it checks all the field conditions and gives a detailed feedback to the user and waits for another activation command to start the motor. The motor is controlled by a simple manipulation in the internal structure of the starter. The starter coil is indirectly activated by means of a transistorized relay circuit. When the motor is started, a constant monitoring on soil moisture and water level is done & once the soil moisture is reached to sufficient level the motor is automatically turned off & a massage is send to subscriber that the motor is turned off. The water level indicator indicates three levels low, medium, high and also empty tank. Shen etc. al (2007) introduced a GSM-SMS remote measurement and control system for greenhouse based on PC-based database system connected with base station. Base station is developed by using a microcontroller, GSM module, sensors and actuators. In practical operation, the central station receives and sends messages through GSM module. Criterion value of parameters to be measured in every base station is set by central station, and then in base stations parameters including the air temperature, the air humidity. Indu etc. al (2013) mainly focuses on reviews in the field of remote monitoring and control, the technology used and their potential advantages. The paper proposes an innovative GSM/Bluetooth based remote controlled embedded system for irrigation. The system sets the irrigation time depending on the temperature and humidity reading from sensors and type of crop and can automatically irrigate the field when unattended. Information is exchanged between far end and designed system via SMS on GSM network. A Bluetooth module is also interfaced with the main microcontroller chip which eliminates the SMS charges when the user is within the limited range of few meters to the designated system. The system informs users about many conditions like status of electricity, dry running motor, increased temperature, water content in soil and smoke via SMS on GSM network or by Bluetooth. The GSM based irrigation system (Fig.1) may offer users the flexibility to regulate and control the operations of their irrigation systems with little intervention to reduce runoff from over watering for improvement in crop yield. This enables users to take advantage of the globally deployed GSM networks with its low SMS service cost to use mobile phones and simple SMS commands to manage their irrigation system. It will be possible for users to use SMS to monitor directly the conditions of their farmland, schedule the water

Microstructure and mechanical properties of Inconel-625 welded joint developed through microwave hybrid heating:

Application of microwave energy for processing of bulk metals is effectively utilized to join Inconel-625 plates through hybrid heating technique using Inconel-625 powder as an interface filler material. Post welding characterization of microwave developed joints through X-ray diffraction shows the development of carbides of niobium and chromium as well as intermetallic phases along with the primary γ-phase face-centered cubic matrix. Microstructural examination reveals the formation of Laves phase along the grain boundaries in the fusion zone. Microwave-induced joints exhibit average microhardness of 245 ± 20 HV and 0.7% porosity in the fusion zone. Average ultimate tensile strength and flexural strength of the developed joints were estimated at 375 and 377 MPa respectively. Average impact toughness of microwave-induced joints is observed to be 18 J.

Microstructural Investigation and Characterization of Bulk Brass Melted by Conventional and Microwave Processing Methods

Microwave processing of bulk metallic materials is an emerging area. In the present work, brass in bulk form is melted in a modified domestic microwave oven operating at 2.45 GHz frequency. As-received and the as-cast brass are subjected to metallurgical and mechanical characterization. Specimens’ surface morphology is studied under Scanning Electron Microscope (SEM). X-Ray Diffraction (XRD) pattern shows the presence of copper oxides phase in both cast brass. Average tensile strength of brass melted using microwave oven is found higher when compared with brass melted in muffle furnace. Hardness of the as-cast brass is found to be higher than the as-received brass. However, brass cast by microwave irradiation exhibits around 2 % higher hardness than the brass cast by conventional heating. Microwave melting of brass consumed nearly six times less time compared to conventional melting.

Melting of tin using muffle furnace and microwave energy and its characterization

Conventional melting of metals consume significant amount of energy. Furthermore, there are possibilities of material and energy losses along with safety risks. To overcome these inherent disadvantages of conventional melting, a novel approach for melting of bulk tin using microwave energy is presented. In the present work, bulk Tin is melted using a conventional muffle furnace and a domestic multimode microwave oven. As received and as cast metals are characterised. X-Ray Diffraction (XRD) technique is used to analyse the phases present. The average tensile strength of the metal casted using muffle furnace and microwave oven is 44.1982 MPa and 50.2867 MPa respectively. Scanning Electron Microscope (SEM) is made use for the study of fractured surface of the tensile specimen, which reveals the areas of plastic deformation. Microwave processed specimen shows 10% higher tensile strength compared to that processed using muffle furnace. Radiography clearly shows cast specimen free from defects. The average hardness of as received tin is higher compared to casted specimens. However, the average hardness value of microwave processed specimen is 19.28% higher than the specimen processed using muffle furnace.