Browsing by Author "Dey, K."

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    A mathematical model for estimating peak particle velocity in a space between two adjacent blast holes
    (2011) Arora, S.; Dey, K.
    Peak particle velocity (PPV) generated in blasting is accepted as a measure of rock and structural damage PPV is measured using a seismograph at a distance from the blast face to keep the instrument safe As the distance between the blast point and seismograph (point of interest) is significantly larger than the length of explosive charge column, the explosive column placed in the blast hole is considered as a point charge. Blast-induced rock damage occurs very close to the blast hole and therefore the charge length cannot be ignored. Thus, estimating the damaged zone by extrapolating far-field observations yields inaccurate results. In this paper, a mathematical model is developed for estimation of near-field PPV considering the effect of charge length in the hole. In the proposed model, effect of an elemental charge in the charge column is calculated and then summed up for the whole charge column of two adjacent holes. Apart from this it also takes into account the direction of blast waves originating from the blast holes. The proposed model is also tested for a field trial.
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    Comparison of two near-field blast vibration estimation models: A theoretical study
    (2013) Arora, S.; Murmu, P.; Dey, K.
    Blast-induced rock damage has been directly related to blast vibration by many researchers. The common measurement of blasting vibration is in terms of peak particle velocity (PPV). The levels of peak particle velocity at which the rock damage occur are termed as threshold levels of PPV for rock damage. As rock damage is a phenomena occurring very close to the blast holes (?1 m), the peak particle velocity levels at the point of damage cannot be measured directly. Thus, the threshold levels of peak particle velocity for rock damage are estimated by using different near-field blast vibration estimation models. These models essentially use the vibration predictors established from the vibration measurements taken at a safe distance. The most common two techniques of near-field vibration estimation models are the mathematical summation of peak particle velocity resulting from the elemental charge column and the integrated peak particle velocity for the charge length i.e., zero to charge height. However, till date the scope of application of near-field estimation models is limited to single-hole blast only. This paper incorporates a review of the near-field blast-vibration estimation models. Apart from this, an extension of a near-field vibration estimation model for a row of periphery holes is also presented. A theoretical comparison is also made in between single-hole model and row of holes model for estimating the threshold peak particle velocity levels for overbreak in a drift. Similarly, the damage profiles for both the cases are also developed and presented. � 2013 Taylor & Francis Group.
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    Comparison of two near-field blast vibration estimation models: A theoretical study
    (CRC Press, 2012) Arora, S.; Murmu, P.; Dey, K.
    Blast-induced rock damage has been directly related to blast vibration by many researchers. The common measurement of blasting vibration is in terms of peak particle velocity (PPV). The levels of peak particle velocity at which the rock damage occur are termed as threshold levels of PPV for rock damage. As rock damage is a phenomena occurring very close to the blast holes (<1 m), the peak particle velocity levels at the point of damage cannot be measured directly. Thus, the threshold levels of peak particle velocity for rock damage are estimated by using different near-field blast vibration estimation models. These models essentially use the vibration predictors established from the vibration measurements taken at a safe distance. The most common two techniques of near-field vibration estimation models are the mathematical summation of peak particle velocity resulting from the elemental charge column and the integrated peak particle velocity for the charge length i.e., zero to charge height. However, till date the scope of application of near-field estimation models is limited to single-hole blast only. This paper incorporates a review of the near-field blast-vibration estimation models. Apart from this, an extension of a near-field vibration estimation model for a row of periphery holes is also presented. A theoretical comparison is also made in between single-hole model and row of holes model for estimating the threshold peak particle velocity levels for overbreak in a drift. Similarly, the damage profiles for both the cases are also developed and presented. © 2013 by Taylor & Francis Group, LLC.
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    Comparison of two near-field blast vibration estimation models: A theoretical study
    (2013) Arora, S.; Murmu, P.; Dey, K.
    Blast-induced rock damage has been directly related to blast vibration by many researchers. The common measurement of blasting vibration is in terms of peak particle velocity (PPV). The levels of peak particle velocity at which the rock damage occur are termed as threshold levels of PPV for rock damage. As rock damage is a phenomena occurring very close to the blast holes (?1 m), the peak particle velocity levels at the point of damage cannot be measured directly. Thus, the threshold levels of peak particle velocity for rock damage are estimated by using different near-field blast vibration estimation models. These models essentially use the vibration predictors established from the vibration measurements taken at a safe distance. The most common two techniques of near-field vibration estimation models are the mathematical summation of peak particle velocity resulting from the elemental charge column and the integrated peak particle velocity for the charge length i.e., zero to charge height. However, till date the scope of application of near-field estimation models is limited to single-hole blast only. This paper incorporates a review of the near-field blast-vibration estimation models. Apart from this, an extension of a near-field vibration estimation model for a row of periphery holes is also presented. A theoretical comparison is also made in between single-hole model and row of holes model for estimating the threshold peak particle velocity levels for overbreak in a drift. Similarly, the damage profiles for both the cases are also developed and presented. © 2013 Taylor & Francis Group.
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    Computer aided cooling curve analysis to calculate the thermophysical properties of zinc aluminium 12
    (2019) Dey, K.; Sannayellappa, N.
    Computer Aided Cooling Curve Analysis (CA-CCA) is the utilization of time-Temperature graph to reveal several processing and material parameters. Its application ranges from prediction of transition temperatures, amount of different phases, latent heat and dendrite coherency point among various others. In the current paper, both Newtonian and Fourier methods were used and solidification parameters such as phase change temperature, latent heat and thermal diffusivity of zinc-12% aluminium alloy (ZA 12) were determined. The phase transition temperatures were observed at 440 +C and 370 +C for liquidus and solidus respectively. The value of latent heat obtained by Fourier technique was 130.7�J/g which is closer to the theoretical value of 118�J/g when compared to Newtonian technique. It can be mainly attributed to the fact that the effect of temperature gradient within the solidifying sample is taken into consideration in Fourier technique. Also thermal diffusivity was calculated as a temperature dependent function for the mushy zone (440-370 +C) using the Fourier method ranging from 5.04 � 10-5m2/s and 3.04 � 10-5m2/s. � 2019 Author(s).
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    Computer aided cooling curve analysis to calculate the thermophysical properties of zinc aluminium 12
    (American Institute of Physics Inc. subs@aip.org, 2019) Dey, K.; SannaYellappa, N.
    Computer Aided Cooling Curve Analysis (CA-CCA) is the utilization of time-Temperature graph to reveal several processing and material parameters. Its application ranges from prediction of transition temperatures, amount of different phases, latent heat and dendrite coherency point among various others. In the current paper, both Newtonian and Fourier methods were used and solidification parameters such as phase change temperature, latent heat and thermal diffusivity of zinc-12% aluminium alloy (ZA 12) were determined. The phase transition temperatures were observed at 440 +C and 370 +C for liquidus and solidus respectively. The value of latent heat obtained by Fourier technique was 130.7âJ/g which is closer to the theoretical value of 118âJ/g when compared to Newtonian technique. It can be mainly attributed to the fact that the effect of temperature gradient within the solidifying sample is taken into consideration in Fourier technique. Also thermal diffusivity was calculated as a temperature dependent function for the mushy zone (440-370 +C) using the Fourier method ranging from 5.04 × 10-5m2/s and 3.04 × 10-5m2/s. © 2019 Author(s).
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    Numerical simulation and characterization of zinc aluminium 12 alloy for latent heat thermal energy storage application
    (American Institute of Physics Inc. claims@aip.org, 2020) Dey, K.; SannaYellappa, N.
    Thermal Energy Storage (TES) has gained popularity in recent times as it provides an efficient and economical approach to limit the discrepancy between supply and demand for energy. In the current paper, the thermal performance of a hypereutectic zinc-12% aluminium (ZA 12) alloy has been studied and is proposed as a potential metallic phase change material to be used for the purpose of Latent Heat Thermal Energy Storage (LHTES) application operating at a temperature range of 300 °C to 500°C. Characterization of the alloy is performed using Fourier technique to determine relevant properties. The change in enthalpy is calculated to be 296.33?J/g-K, while the measured value of mean specific heat and latent heat were 0.531?J/g-K and 130.68?J/g respectively. Both solid fraction and thermal diffusivity were determined as a function of temperature for the mushy region. A numerically validated transient model based on the enthalpy -porosity formulation is employed to analyze the solidification/melting performance of ZA 12 alloy. Contour of liquid fraction and velocity streamline during phase transformation is obtained revealing various details about the process mechanism. © 2020 Author(s).