Sriram Malladi | Michigan Technological University (original) (raw)

Papers by Sriram Malladi

Conference Proceedings of the Society for Experimental Mechanics Series, 2016

Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Modeling, Simulation and Control of Adaptive Systems, 2015

Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting, 2015

2015 International Conference on Location and GNSS (ICL-GNSS), 2015

Conference Proceedings of the Society for Experimental Mechanics Series, 2015

Conference Proceedings of the Society for Experimental Mechanics Series, 2014

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Structural Health Monitoring; Keynote Presentation, 2014

Shape memory alloy (SMA) actuators exhibit considerable hysteresis between the supply voltage (co... more Shape memory alloy (SMA) actuators exhibit considerable hysteresis between the supply voltage (conventionally used in resistive heating) and strain characteristics of the SMA. Hence, it is not easy to control the strain of a thin-SMA wire, unless a model is developed that can match the actuator's nonlinearities for predicting the supply voltage required by the SMA system accurately. The work presented in this paper proposes the use of a black-box technique called the adaptive neurofuzzy inference system (ANFIS) to study the hysteretic behavior of SMAs. The input parameters for such an ANFIS model would be a physical variable at time t and at a time t + n, where n is a time shift. The present work studies the effect of a time shift on the actuator nonlinearities for two ANFIS models. One of the models studies the relationship between the desired displacement of an SMA and the supply voltage across the SMA, while the other model predicts the actual displacement of an SMA from the feedback temperature. A novel SMA–Constantan thermocouple records the feedback temperature.

SMASIS 2014

Traveling waves have shown the potential to transport material and are thus investigated as a pr... more Traveling waves have shown the potential to transport
material and are thus investigated as a propulsion mechanism.
Through the use of piezoelectric actuators (PZTs), traveling
waves were produced in beams with both free-free and fixed-free boundary conditions. It is shown that traveling waves can be generated by exciting two PZTs at a common frequency with a phase difference between the PZT signals. Experimentation showed the signal that creates the best traveling wave occurs at a driving frequency halfway between adjacent bending resonance frequencies and a phase difference of 90° between both PZTs signals. This has produced traveling waves in fixed-free beams and free-free beams
in both air and water as well as for an underwater vehicle.
These traveling waves generated useful propulsion in both
the fixed -free and free-free beams.

A mechanical wave is generated as a result of an oscillating body interacting with the well-defin... more A mechanical wave is generated as a result of an oscillating
body interacting with the well-defined medium and it propagates through that medium transferring energy
from one location to another. The ability to generate and control the motion of the mechanical waves through
the finite medium opens up the opportunities for creating novel actuation mechanisms. The focus of this study is on
understanding the traveling wave generation and propagation by establishing the relationships that illustrate the role of structural and electromechanical parameters. A brass be
a m with free-free boundary conditions was selected to be the medium through which the wave propagation occurs. Two piezoelectric elements were bonded on the opposite ends of the beam and were used to generate the controlled oscillations.
Excitation of the piezoelectrics results in coupled system dynamics that can be translated into generation of the
waves with desired characteristics. Theoretical analysis based on the distributed parameter model and experiments were conducted to provide the comprehensive understanding of the wave generation and propagation behavior.

Proceedings of ASME 2013 Conference on Smart Materials, Adaptive structures and Intelligent Systems. Snow Bird,Utha

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

Given the light weight and sensitive nature of gossamer structures, applying non-intrus... more Given the light weight and sensitive nature of gossamer structures, applying non-intrusive excitation and measurement techniques is beneficial during either the design stage or in operational conditions. The use of non-contact measurement techniques,such as laser
vibrometry, has been extensively used in testing of lightweight structures and proven beneficial. The
successful implementation of non-contact excitation techniques, however, is more difficult. Commonly used
and seen in past literature, has been the implementation of boundary excitation and acoustics in order to generate a non-contact type of excitation source. Both these techniques distribute the excitation generated on the surface of the specimen as opposed to a point source. A SISO or SIMO type of approach cannot be used for system identification
as the nature of these excitations are not single input. The implementation of a MIMO approach
should not be used either, as the excitation cannot be
measured directly nor are the inputs uncorrelated. The work here investigates the use of a
pressurized solenoid valve with compressed air to generate a point excitation on an ultra-lightweight circular membrane. The experimental results are compared with a previously validated theoretical model of a membrane in air. An impedance-based model of a circular membrane is used which takes into account the energy loss due to radiation to the far field.
This work also attempts to quantify in a general sense
the errors induced when neglecting these
differences using distributed type excitations versus single point.

Proceedings of the 31st IMAC, A Conference on Structural Dynamics, 2013

The work herein presents a novel approach for sound field characterization based on a continuous ... more The work herein presents a novel approach for sound field characterization based on a continuous scanning/roving approach. Conventional methods use sensor arrays or a discreet moving sensor to characterize an acoustic field. Although these methods are well established, this new approach attempts to take advantage of a continuous measurement methodology, in space and time, in order to increase spatial resolution of the acoustic field, minimize the use of sensors required, and the acquisition time. The novel approach relies on processing amplitude-modulated time signal, with geometrical reference, in order to characterize the acoustic field. This technique can be thought of as an extension of continuous scanning laser Doppler vibrometry techniques.The work is demonstrated on a lab test article and used to identify the acoustic propagation generated by the excitation of several structural modes. The work shown here is preliminary and mainly aimed at proving the methods feasibility.

Active research of SMA has presented the measurement of thermoelectric properties as a useful and... more Active research of SMA has presented the measurement of thermoelectric properties as a useful and a potential tool in the study of phase transformations. The Seebeck coefficient is sensitive to the martensitic transformation behavior of SMA and can potentially be used to determine the state of Martensitic transformation of a SMA. The combination of Shape Memory Alloy having a positive Seebeck coefficient and Constantan with a negative Seebeck coefficient (−35 μV/K) is a suitable thermocouple pair to measure temperature. This relation along with the displacement characteristic provides a feasible method to determine the state of SMA at any point during Martensitic phase transformation. Future work aims at utilizing the thermoelectric relation of the SMA-Constantan thermocouple as a feedback variable in replacing external sensor.

International Journal of Information Processing. 01/2012; 6(4):55-63., Jan 2012

ABSTRACT: Recursive partitioning produces a classification tree in which factors are assigned to... more ABSTRACT: Recursive partitioning produces a classification tree in which factors are assigned to mutually exclusive subsets as per set of predictor variables. In this work recursive partitioning has been used as a substitute to multiple linear regression for multi variable analysis of data from a petrochemical process for Poly Butadiene Rubber (PBR) plant for control of its product quality parameter, Mooney viscosity. Poly Butadiene Rubber is used in rubber processing industries. Mooney viscosity is an important quality parameter of PBR. The design range of Mooney viscosity of the product from last reactor outlet is in the range of 37-47. Reduction in the variation in Mooney viscosity improves product quality and results in greater customer satisfaction. Data mining techniques have been used to analyze the Mooney viscosity and process variable data to obtain range of values of process variables that result Mooney in the desired range of 37-43. Recursive partitioning identified various subgroups with different mean values of the quality parameter. Of all the subgroups, the classification tree produced by recursive partitioning that consisted of 5 factors is found to be suitable to get the desired range of Mooney viscosity value.

Poly Butadiene Rubber (PBR) is used in rubber processing industries. Mooney viscosity is an impor... more Poly Butadiene Rubber (PBR) is used in rubber processing industries. Mooney viscosity is an important quality parameter of PBR. The design range of Mooney viscosity of the product from last reactor outlet is in the range of 37-47. The existing variation of Mooney viscosity is between 37 and 43 for 92% of the product. Further reduction in the variation in Mooney viscosity improves product quality and results in greater customer satisfaction. Data mining techniques have been used to analyze the Mooney viscosity and process variable data to obtain range of values of process variables that gives Mooney in the desired range of 37-43. Data partitioning and interval plots are used to obtain the range of process variables that will keep the Mooney viscosity in the desired range.

Indian Welding Journal, Oct 2010

The interactions of welding input parameters are studied by an ANFIS model in MATLAB of Submerged... more The interactions of welding input parameters are studied by an ANFIS model in MATLAB of Submerged Arc Welding process. SAW is a high quality, very high deposition rate welding process commonly used to joint plates. The main objective is to identify the main input factors, to determine the interaction amongst the input factors and finally establish the optimum model for predicting the weld bead parameters that leads to the desired weld quality.

Recent Advances in Information Technology (RAIT), 2012, Mar 2012

Analysis of stability (mainly bearing strength and settlement) under a footing on regularly b... more Analysis of stability (mainly bearing strength and settlement) under a footing on regularly bedded, jointed and layered model rock mass is conducted using Back Propagating Neural Network (BPNN) and Adaptive Neuro Fuzzy Inference Systems (ANFIS). The inputs required for the modeling were imported from the laboratory results of the measurements carried out earlier [1]. Rock mass were modeled as elastic-plastic with Drucker- Prager failure criteria for plane strain condition. The results of the footing settlements and bearing strengths derived from BPNN and ANFIS models were compared with the footing settlements corresponding to the maximum applied bearing pressure on floor strata (for different sizes of footing plates and also under varying anisotropy conditions of floor strata) as obtained from the experimental results and FEM investigations and the bearing strengths obtained from the laboratory investigations. It is deduced that ANFIS model predicts accurately well vis-à-vis experimental results though the results predicted from BPNN model compares well with those of FEM analysis.

The primary objective of steelmaking through Basic Oxygen Furnace (BOF) process is to achieve d... more The primary objective of steelmaking through Basic Oxygen Furnace (BOF) process is to achieve desired end point carbon content, temperature and percentage composition at the lowest cost and in the shortest possible time. As of now, most widely used models for prediction of parameters of converter steelmaking are mechanistic model, statistical model and neural network model for the prediction of the end point carbon content and temperature from BOF process parameters with reasonable accuracy. The (BOF) process is a widely preferred and effective steelmaking process due to its higher productivity and low production cost. The process of converter steel making is complicated and not completely understood as it involves multiphase physical chemical reaction at high temperature. Obtaining molten steel of desired chemical composition is the objective of the process. Obviously, in the converter steel making, the end point carbon content and temperature of the molten steel are important controlling parameters to ascertain whether the molten steel of desired quality is achieved or not. In the present paper, the authors have made an attempt to develop model for end point carbon and temperature with the latest methodology i.e., Adaptive Neural Fuzzy Inference System (ANFIS) and then have brought out the comparison of the results achieved in Neural Network and GRNN models. Results from ANFIS model predict more accurately in contrast to those from BPNN model vis-à-vis the measured carbon content and temperature.