Chittaranjan Sahay

Analysis of Ultrasonic Machining Using Monte Carlo Simulation

Proper selection of manufacturing conditions is one of the most important aspects in Ultrasonic Machining process, as these conditions determine the Material Removal Rate (MRR). In this work, two very popular mathematical models proposed by Miller and Shaw have been investigated using Monte Carlo simulation based Crystal Ball analysis tool. Effects of abrasive particle size, particle concentration, amplitude of tool vibration, tool radius and depth of hole on MRR have been analyzed for both models. Miller’s model indicates a strong positive relationship between abrasive grain size, concentration and MRR. Contrary to the literature search on experimental data, Shaw’s mathematical model indicates a negative relationship between MRR and grain size, and a very weak relationship between MRR and concentration. No definite relationship could be established between either tool radius and MRR or amplitude and MRR. A negative relationship between depth of hole and MRR was obtained for Shaw’s model.Copyright

Process Improvement of Brake Lever Production Using DMAIC (

This work describes a strategy to reduce the cost associated with poor quality, by reducing the parts per million defects by Defining, Measuring, Analyzing, Implementing and Controlling (DMAIC) the production process. The method uses a combination of principles of Six Sigma applications, Lean Manufacturing and Shanin Strategy. The process has been used in analyzing the manufacturing lines of a brake lever at a Connecticut automotive components manufacturing company for reducing the cost associated with the production of nonconforming parts. The analysis was carried out with the help of the data collected on nonconformance parts and the application of phase change rules from DMAIC (+). Data analysis was carried out on statistical process control softwares, MINITAB and SPC XL 2000. Although, the problem of tight bushing existed on only one line of the brake lever assembly, this problem solving approach has solved the tight bushing problems on all assembly and alternates lines in a time- and cost-effective way.Copyright

Optimization of Assembly and Disassembly of GP7200 Engine

Build studies were conducted on three different GP7200 engines at a local aircraft engine manufacturer to reduce cost while improving quality, reducing time (cycle time, takt time and lead time), reducing scrap, rework and reducing injuries (increased safety). The paper describes the development of an efficient and effective Dress and Strip process. This project incorporated standard concepts including, DIVE (Define, Investigate, Verify, Ensure), Takt time, Set-Up Reduction, 6S (Sort, Straighten, Shine, Standardize, Sustain and Safety), Kaizen, Quality control & Quality Information System (QIS) and Quality Clinic Process Charting program (QCPC). Seven Wastes (Overproduction, waiting for the next process, unnecessary transportation of materials, over processing of parts due to poor tool and product design, excess inventories, unnecessary movement, and defective parts from supplier), Standard Work, Total Productive Maintenance (TPM) and Value Stream Mapping (VSM) were used in the project. In addition, tools such as, Relentless Root Cause Analysis (RRCA), Root Cause Corrective Action (RCCA) and Mistake Proofing (MP) have been used in conjunction with other quality tools. Following the successful optimization of the process of assembly and disassembly of these engines, several recommendations were made including redesign of some assembly and disassembly tools. The paper presents an improved Assembly/ Disassembly spaghetti diagram and changes in tool design based on observations.Copyright

Modeling Laser Travel and its Effects on Thermal Stresses in Laser Hardening of Steel

To achieve a precise and controlled laser process, a thorough analysis of the thermal behavior of the material is necessary. The knowledge of the thermal cycles is important to ascertain suitable processing parameters, thus improving surface properties when the alloys are laser irradiated. In the present paper, a numerical simulation of the laser hardening process has been developed using the finite element (FE) code ABAQUS™ to solve the heat transfer equation inside the treated material (AISI 4140 steel). The thermal analysis is based on Jaeger’s classical moving heat source method by considering the laser beam as a moving plane (band/disc) heat source and the target material is a semi-infinite solid. However, the FE model, used to solve the governing equation, does not directly accommodate the moving nature of heat source. A reasonable approximation is to divide the laser travel on the substrate into many small time/load steps, and apply variable flux and boundary conditions in each time/load step. This approximates the quasi-steady state phenomena over the series of these time steps for the complete laser travel. This paper investigates the effects of the choice of time/load steps on the temperature and thermal stress evolution as well the computing times in the process.Copyright

Motorcycle Swing Arm Development and Refinement Using Response Optimization

The purpose of this project is to develop a motorcycle rear swing arm using finite element analysis and response optimization. This paper aims to discuss the specific features, benefits, and precautions when using design optimization to develop a specific project. Design Optimization has been an evolving process for many years. The latest versions of finite element software allow users to develop, analyze, and optimize structural designs within one program quickly and efficiently. A single shock absorber mounted close to the chassis and centrally located was the design selected to be analyzed. The design was selected for use in a variety of motorcycle types. This project consisted of a unique set of design attributes that were ideal to exemplify design optimization techniques. Static structural models were created to refine the design before using response optimization. These models finalized the material selection and initial sizes. A central composite design type was generated with selected boundary conditions for four parametric dimensions of the model. The ideal design of this component would include the resulting stress below a safe allowable value, minimal deflection, and the least amount of weight. It is evident that these three parameters will oppose one another as geometry is changed. Conceptually, an ideal candidate can be created that is a balance of the three parameters. Using the parameters of the selected candidate, a new model was generated for analysis. The final model was further refined by removing unnecessary material that was identified in the structural models.The first step in a thorough optimization is generating an appropriate amount of design parameter values that are an acceptable representation of all the possible outcomes, or design of experiments (DOE). The DOE tool used to generate the parameters in this project was central composite design (CCD), since it is the most appropriate for second order response models [1]. The second order relationship was confirmed using a trade-off plot. The two level, four input parameter DOE produces twenty five potential candidates that were refined using response surface. The response surface method used in this design process [2,3] to make judgement calls on the final design is examined during this development, and proves useful. Initial static structural models are created and used to set up the model for optimization. Material selection was also accomplished in this phase of development. This process aides in the overall design process by identifying areas of concern as well as the range of parameters that will be analyzed. Multiple acceptable candidates were selected through the use of the optimization tools and a final candidate was selected based on the output of the design attributes and the values of the corresponding parametric geometry. The final selection was also made with the consideration for cost, ease of fabrication, and standardization.Copyright

Modeling Phase Transformation Kinetics and Their Effect on Hardness and Hardness Depth in Laser Hardening of Hypoeutectoid Steel

Much research has been done to model laser hardening phase transformation kinetics. In that research, assumptions are made about the austenization of the steel that does not translate into accurate hardness depth calculations. The purpose of this paper is to develop an analytical method to accurately model laser hardening phase transformation kinetics of hypoeutectoid steel, accounting for non-homogeneous austenization. The modeling is split into two sections. The first models the transient thermal analysis to obtain temperature time-histories for each point in the workpiece. The second models non-homogeneous austenization and utilizes continuous cooling curves to predict microstructure and hardness. Non-homogeneous austenization plays a significant role in the hardness and hardness depth in the steel. A finite element based three-dimensional thermal analysis in ANSYS is performed to obtain the temperature history on three steel workpieces for laser hardening process with no melting; AISI 1030, 1040 and 1045 steels. This is followed by the determination of microstructural changes due to ferrite and pearlite transformation to austenite during heating and the subsequent austenite to martensite and other diffusional transformations during cooling. Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is used to track the phase transformations during heating, including the effects of non-homogenous austenitization. The solid state nodal phase transformations during cooling are monitored on the material’s digitized Continuous Cooling Transformation (CCT) curve through a user defined input file in ANSYS for all cooling rates within the Heat Affected Zone (HAZ). Material non-linearity is included in the model by including temperature dependent thermal properties for the material. The model predictions for hardness underneath the laser and the HAZ match well with the experimental results published in literature.Copyright

Modeling Laser Travel and its Effects on Temperature Evolution in Laser Hardening of Hypoeutectoid Steel

To achieve a precise and controlled laser process, a thorough analysis of the thermal behavior of the material is necessary. The knowledge of the thermal cycles is important to ascertain suitable processing parameters, thus improving surface properties when the alloys are laser irradiated. In the present paper, a numerical simulation of the laser hardening process has been developed using the finite element (FE) code ABAQUS™ to solve the heat transfer equation inside the treated material (AISI 4140 steel). The thermal analysis is based on Jaeger’s classical moving heat source method by considering the laser beam as a moving plane (band/disc) heat source and the target material is a semi-infinite solid. However, the FE model, used to solve the governing equation, does not directly accommodate the moving nature of heat source. A reasonable approximation is to divide the laser travel on the substrate into many small time/load steps, and apply variable flux and boundary conditions in each time/load step. This approximates the quasi-steady state phenomena over the series of these time steps for the complete laser travel. This paper investigates the effects of the choice of time/load steps on the temperature evolution as well the computing times in the process.© 2014 ASME

Comparative Study Between FEA-Based Sequentially-Coupled and Fully-Coupled Thermal Stress Models in a Laser Hardening Process

Numerous mathematical investigations of laser transformation hardening process have been conducted in the past three decades. The commonly used strategy of a sequentially coupled temperature-stress analysis is to first obtain temperature results from the temperature elements in a thermal loading model, followed by the calculations of thermal stresses from the structural elements under structural loading. Temperature is used as a predefined variable (varies with position and time only) as it is assumed to not change by the stress analysis. Fully coupled thermal-stress analysis is needed when the stress analysis is dependent on the temperature distribution and the temperature distribution depends on the stress solution This paper compares these two finite element (FE) based approaches for modeling temperature and thermal stress evolution in laser transformation hardening of hypoeutectoid steels. The dependence of temperature results on stresses and vice versa at higher temperatures involving significant inelastic strains has been demonstrated. Preliminary investigation reveals that under such circumstances thermal and mechanical solutions must be obtained simultaneously rather than sequentially.Copyright

Effects of Within Part Variation on Measurement System Analysis

Inherent variation of the measurement system, part-to-part variation and variation arising due to the operator are considered to be the most common sources of variation in a measurement system analysis (MSA). Often errors due to within part variation are overlooked, or even worse, are assumed to be from the inherent variation of the measurement system. Understanding the sources of variation in a measurement system is important for all measurement applications. It becomes even more critical when the part used to evaluate a gage has a significant within part variation. This is an important source of measurement system error that the current procedures followed for MSA studies do not clearly or adequately address. The primary reason for this is a lack of awareness, and there are no clear guidelines on conducting a MSA study under these circumstances. A detailed analysis of the effects of within part variation on MSA is described in this paper. An improved method for conducting the MSA under these circumstances is also presented. This improved and more effective MSA takes all sources of variations into consideration.Copyright

Airfoil Deformation Analysis During Stator Repair Process

The compressor stator assembly of a jet engine normally consists of stainless steel and Inconel alloys. Nickel based alloys can be also used as brazing material. Mechanical distortion of the stator assembly components may result during the brazing process. The coefficient of thermal expansion of the component materials, thermal history of manufacturing and operation also contribute to the stator deformation. The purpose of this work is to study the factors causing the distortion in vane stages. The study uses Finite Element Analysis tool ANSYS 5.7 for modeling the engine stator assembly. A finite element structural analysis of a single airfoil model is conducted at various repair points to assess the airfoil deformation and stress levels, before and after the brazing process. It is then used to identify materials and brazing parameters responsible for the observed distortion. The model analyzed shows general agreement between the numerical results and observations from the repair process. The probable causes of distortion are found and recommendations for fixing the distortion problem are also made.Copyright