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In automobiles there is large scope for composite materials to be used for manufacture of structural parts. The development of electric vehicles has caused for a gain in utilization of composites i...

Single point incremental forming (SPIF) has higher formability than other sheet metal forming processes. In SPIF, the existing computer numeric control (CNC) incremental forming which adopts 3-axis CNC milling machine to form the part incrementally by using a hemispherical tool has the limitation of forming steeper wall angle parts. An additional 2-degree of freedom (DOF) manipulator has been proposed to integrate with the existing 3-axis CNC milling machine to improve the formability of the sheet. In this method, to control the material flow and deformation state, the posture of the sheet has been changed by tilting the sheet along the needed direction and rotating at specific speed with respect to the vertical forming tool. Formability of the sheet has been investigated in terms of sheet thinning and strain distribution after deformation. Numerical simulation has been implemented initially and has been validated by conducting the experiments. The result of the research shows that formability can be improved by adding the 2-DOF manipulator to the existing system.

In case of a crash due to collision of vehicles, effective impact energy absorption by the vehicle safety structure is significant as it reduces the damage to the vehicle and its occupants. Components made of composite materials have a more complex mode of deformation, unlike metals, which in general deform with buckling or bending modes. The deformation mode of the component made of a composite is of great importance as the energy absorption level depends on it. Deformation mode can be modified by introducing special geometric features known as triggers in the design of the crash box. A trigger can also be useful in achieving required deformation mode and thereby helpful in attaining target energy and force values. The present study focuses on the effect of geometric shapes along with three novel trigger types on the level of energy absorbed for the GFRP composite material passenger car crash box in a low-velocity impact, named as “RCAR Test” in the automobile industry. All possible combinations of four different types of geometric cross sections, namely, square, cylindrical, hexagonal, and decagonal, and three novel patterns of notch trigger, imparted to a GFRP crash box were considered for study in the present work. The force distribution, energy absorbed, and SEA (specific energy absorption) were estimated. The relative merit of crash boxes with different combinations of cross-sections and trigger types for these parameters was assessed. The best performing combinations made from various notch triggers and different cross sections of crash boxes have been identified.

Composite materials are being widely used in automobile industry in order to meet the ever increasing demand to achieve significant weight reduction by maintaining the performance levels. Additiona...

There is an ever-increasing demand in the automotive sector to continuously improve the performance and reduce cost through weight reduction in the structure of the vehicle. In the present scenario, it is also necessary to meet the standards set by crash safety regulating authorities in various parts of the world. In automobiles, the crash box is placed in the anterior region to absorb the impact energy in the event of an accident. Glass fiber reinforced plastic crash boxes have a high strength-to-weight ratio and also are good in energy absorption, particularly useful in this scenario. In this paper, the effectiveness of different triggers in combination with various geometries is investigated for Glass fiber reinforced plastic crash boxes using drop-weight impact testing. A trigger is a geometric irregularity introduced in the crash box design to alter the energy as well as force levels by modifying the deformation mode under loading. Comparison of change in force level, absorption of impact energy, specific energy absorption values was performed for composite crash boxes made of various types of cross-sectional geometries along with multiple patterns of triggers. Force versus displacement (F–D) curves are drawn for all the cases of the glass fiber reinforced plastic crash boxes to understand the behavior of each combination formed with various types of geometries and triggers, under impact loading. Strength-to-weight ratio was considered as the deciding factor for the comparisons to know the best and worst cases of the crash boxes made of different cross-sections along with various trigger types. This study provides detailed insights into the drop-weight impact testing procedure including the preparation of specimens, setting up the drop-weight impact test, preparation of specimen clamps, safety precautions involved, data acquisition from the test and its processing.

The authors have developed trans-tibial prosthetic sockets using additive manufacturing. These sockets made with mono-material thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) at lower thicknesses were found to fracture within a few days of use by the amputees. The fracture was repeatedly found to occur at specific locations such as the lobe corners and the socket’s lower one-third zone. The most probable causes of crack initiation are lack of fusion (LOF) sites and voids. The causes of crack propagation are the lower interlayer bond strength compared to intra-layer bond strength. However, no scientific work exists that clearly explains these phenomena and methods to prevent such potential crack initiation sites and arrest the propagation of such fracture in additively manufactured polymeric structures. Therefore, in the present work, the investigation was carried out into possible enhancement in the resistance to fracture by different strength-enhancing post-processing techniques. In the first technique, the placement of stiffener features at selected locations on the socket was investigated. Three-point bending tests were carried out on D790 standard ABS specimens with different stiffeners introduced on the bottom face. The study focused on fracture characteristics in the stiffener-based topologically optimized geometric design of plate structures made by Fused Deposition Modeling (FDM) under flexural loading. The D790 three-point bending specimens were provided with differently shaped stiffeners, namely, triangular, prismatic, cuboidal, and pyramidal, extending all along the specimen’s length and spread with differential gaps in the width direction. In the second method, thermosetting epoxy resin coatings were applied on the three-point bending specimens of ABS, and the effect of the coating on the flexural strength was investigated. Bending tests were done on three specimens, the first specimen without any coating, the second specimen with only the epoxy resin coating, and the third specimen with two different coating layers. The first of the two coating layers on the third specimen was with primer and the second layer was with epoxy resin. Scanning electron microscope (SEM) and energy dispersion spectroscopy (EDS) scanning analyses were conducted on the fractured specimens. The scanning images indicated that both the primer and resin materials showed a tendency to diffuse into the substrate of ABS, thereby weakening the extreme fibers of material on the specimen’s tension side, resulting in premature crack initiation and propagation. Significant gain in the flexural strength was observed in both the strength enhancement techniques compared to plain specimens.

Automobile manufacturers using tailor welded blank (TWB) technology carryout forming operations for curved shape components by orienting multiple welds. This process results in the formation of inflection point at the welded joints, leading to fracture during forming. The study of the effect of curvilinear weld profile on formability aspects with regard to stamping/deep drawing operations is limited. Curvilinear welds decrease the number of weld requirements, scrap material and avoid imperfections whenever two welds intersect. In this work, the effect of different shapes of weld profiles viz. circular, elliptical and spline shapes on the weld line movement (WLM) was studied. WLM is one of the primary concerns in the manufacture of tailor welded blanks, because it affects component assembly and also leads to wrinkling and tearing during forming. Simulation results showed that the spline curve weld profile has a considerable effect in reducing WLM with improved formability compared to straight welds.

In this paper, studies on the tensile strength, fracture initiation and propagation behaviour of composite material layered shell structures manufactured by extrusion based additive manufacturing (AM) is reported. To understand the basic mechanical behaviour, simple tension tests have been conducted on ASTM-D638 specimens of carbon fiber and natural fiber reinforced polymer matrix composites made by AM in different modes as well as directly in filament form using a filament extruder. The tensile strengths reveal that the internal defects unique to additive manufacturing, such as lack of fusion (LOF) sites and voids, play crucial role in the macroscopic fracture. Based on the tensile test results, finite element analysis of shell structures typical of below-knee prosthetic sockets has been conducted to predict the fracture initiation sites and propagation paths. The analysis results have shown close correlation with the experimental observation of the fracture phenomenon in the prosthetic sockets given to pilot test amputees.

Manufacturing of composites is different from metals and requires special techniques. Therefore, this paper is dedicated to explaining in detail the manufacturing process for preparing the composite GFRP (glass fiber reinforced plastic) crash boxes. In this research paper, step by step procedure for manufacturing of the specimens is presented with details. The various steps involved in the manufacturing technique require design of moulds, estimation of curing time, techniques of curing and the methods of removal of the specimens from the moulds. Hand lay-up technique is used for making all the GFRP composite crash boxes in the present research paper. Manufacturing of mould for the specimen, precautions while dealing with glass fibers, hardening agents and resins. Wrapping techniques and curing time prediction, use of releasing agents for pull out of specimens are explained.

For severe metal deformation processes such as metal drawing operations, the use of porous lubricant carrier layer on metal surfaces has been proposed in recent literature for better lubricant retention and effectiveness under extreme conditions. The porous layer may be generated by different methods and the method chosen in this study involves electroplating a thin layer of an alloy of tin and zinc on the parent metal and subsequent selective etching of zinc. The aim of this study is to optimize parameters for specific application of the new technique in steel tube drawing operation using Taguchi's experimental design procedures. Experiments are designed based on three controllable factors namely electric current density, process time and Sn-Zn composition by weight in electrolyte at three levels. L9 orthogonal array is used for this study. The regression models have been constructed for drawing force and surface roughness along with verification of the model fit using (R2) values and analysis of variance (ANOVA). The optimal values for parameters have been identified using signal to noise (S/N) ratio. All the calculations are obtained by using Minitab software. The optimal levels for: current density (I) is 1 A/cm2; for plating time (T) is 12 min and; Sn:Zn composition is 1:6. This study may pave the way for industrial adoption of the new technique of using porous layer in tube drawing operations to bring out the associated benefits of doing away with the conventional lubrication systems that have proven environmental hazards.

Use of graph theory for enumeration of Epicyclic gear trains (EGTs) is common during conceptual stage. According to theory of structural synthesis of EGTs, two kinds of graphs are defined namely rotation and displacement graphs, for a given number of links and one degree of freedom. In case, all the non-isomorphic rotation graphs are enumerated, then the next stage of synthesis involves the generation of displacement graphs for each rotation graph. To this end, given a rotation graph, the present work proposes an algorithm for generation of all the displacement graphs. Firstly, the rotation graph is decomposed into modules called kinematic units (KUs). Then, for each KU, all the edge-labeling possibilities of turning pairs are evaluated. Finally, displacement graphs are obtained by building the edge labeled KUs in all possible ways. Acyclic graph based representation is employed and displacement graphs with and up to 7 links are enumerated. The enumeration of displacement graphs is treated as two different cases corresponding to rotation graphs enumerated using recursive and non-recursive schemes and the results are in agreement with C.H. Hsu and others.

The problems associated with the prostheses for transtibial amputees are related mainly to the fit and comfort. There has been a steady effort to improve the wearability, stability, and durability of the below-knee prosthesis. The liner in the below-knee prosthesis plays a crucial role in ensuring these quality characteristics. Isotropic liner material either acts hard and hence result in discomfort or deforms too much and results in eventual loosening of the prosthetic socket. The material hyper-elastic behavior and thickness are both critical in the design of the liner with optimum comfort. A generalized deformation model taking into account the interaction of the socket, liner, muscle, and tissue becomes cumbersome. In the literature, numerous hyper-elastic models have been applied. Studies on suitability and application of hyper-elastic materials for liner material has not been sufficiently carried out. In this paper, the suitability of liner materials in terms of their ability to allow sufficient elastic deformation in the normal direction for the cushioning effect while undergoing limited shear deformation has been investigated. The hyper-elastic liner and rigid socket pair have been idealized as adhesively bonded flat layers of suitable thicknesses subjected to various combinations of normal and shear loads. The deformations for a normal load and varied range of shear loads have been compared to conclude on the best-suited material model. The low shear deformation observed for all three liner materials implies that the shear loading will not affect the adhesive bond between the liner and socket and hence will not cause loosening with prolonged usage of the prosthetics. The deformation observed was maximum with Ogden 3-parameter hyper-elastic model, whereas it was least in the case when Mooney Rivlin 3-parameter hyper-elastic model. The results obtained for the Mooney-Rivlin 3-parameter model and Neo-Hookean model are very close to each other.

The kinematic structure of an epicyclic gear train (EGT) contains the information regarding which link is connected to which other link and by what type of joint. In accordance with the graph theoretic framework for EGTs, its kinematic structure can be represented using a simple graph model. During the conceptual stage, structural synthesis of EGTs is performed, and it is aimed at the enumeration of all non-isomorphic graphs (concepts), for a given number of links and DOF. All the candidate graphs are generated by performing some combinatorial operations on a set of parent graphs. Basically, the structural synthesis approaches in the mechanisms literature can be grouped into three categories, namely, recursive, non-recursive and acyclic graph-based schemes, respectively. In this work, the strategies for generation of EGTs, adopted by different researchers and spanning all the three categories, are reviewed. Moreover, the different graph representations encountered in synthesis of EGTs and the generation algorithms are lucidly explained using examples. A recent trend is the development of synthesis methods of EGTs inspired from established methods of those of linkage-type kinematic chains.

In this work, the formability aspects in terms of desired cup height during stamping operation of tailor welded blanks have been studied along with minimizing the movement of weld line. Circular sheets were prepared by joining austenitic stainless steel (ASS 304 Grade) and drawing quality mild steel (AISI 1018) materials with tungsten inert gas welding. To reduce the undesirable weld line movement during stamping process, a novel heat-assisted forming method involving localized and controlled heating of the stronger material side (ASS 304 steel) has been carried out. The experimental setup developed for this purpose enabled heating and maintained the selected zone at the desired temperature during the stamping process. The entire process has been simulated using finite element method and the results obtained were in close agreement with the experimental results. The effect of selective heating of tailor welded blank also resulted in the overall improvement in the quality of the product.

In incremental sheet metal forming (ISF), by maintaining contact between tool and sheet metal can help in uniform thickness distribution and improved surface quality. In the present work the tool path versatility has been explored by transferring some of the tool-sheet relative movements to the work piece by using a two-degree of freedom robotic manipulator with an aim to improve surface finish and achieve greater wall angles. The robotic manipulator has been designed to orient the sheet metal part with respect to the forming tool fixed in the three-axis machine tool to form steeper wall angle parts with better surface finish. The effect of rotational speed, wall angle, tilting angle and tool linear step interval on forming quality in robot assisted incremental forming has been studied and analyzed. Steeper wall angles and better surface finish were found to be obtained with the help of the robotic manipulator than the conventional incremental forming. The results of design of experiments based parametric study on surface finish have been presented.

The limitation over the maximum formable wall angle in single stage incremental forming can be overcome by adopting multi stage forming strategy. This paper focuses on some preliminary finite element studies on deformation behavior of EDD steel in multi stage incremental forming in terms of thickness distribution, strains and geometric accuracy. The study has been carried by forming a conical cup with 850wall angle in four stages. Thickness distribution results revels that the sine law cannot predict the thickness with increase in number of stages. The major and minor principal strain history shows that the material is under plane strain condition in stage#1 and is towards bi-axial stretching with increase in number of stages. The simulation results also captured the geometric inaccuracies due to the formation of residual cone in Multi Stage Incremental Forming (MSIF). The finite element simulations can be used successfully to decide the number of stages and geometric accuracy parts in MSIF.

The main objective of this study is to investigate the effect of process parameters on maximum formable wall angle in incremental forming of 0.5 mm thickness extra deep drawing steel sheets. For th...

Triggers can be implemented in the design of crash box to help in achieving desired deformation pattern, energy absorption and peak force value. In this study, crashworthiness of glass fibre reinforced plastic (GFRP) composite crash box structures with novel geometrically intrinsic triggers has been studied extensively for different types of geometric cross sections. In this study, GFRP crash boxes with four types of cross sections: square, cylindrical, hexagonal and decagonal are considered. Six different types of novel triggers, namely; type-1 slot, type-2 slot, type-3 slot, thickness variation 1, thickness variation 2 and thickness variation 3 are applied to all the types of crash boxes. A comparative numerical analysis is done to study the effect of each trigger on the energy absorption of crash boxes in low velocity impact, based on the ‘Research Council for Automobile Repairs’ test popularly known as the ‘RCAR’ test. Force versus displacement curves were plotted for each case providing detai...

Tailor welded blank (TWB) technology has been used in the manufacture of automobile body-in-white components since a long time. These components consist of different materials/thicknesses. Researchers and manufacturers involved with production of warm formed TWB components failed to address the sustainable issues related to warm forming. Rather they concentrated more on reducing the weld line movement (WLM). The WLM if not arrested shall lead to fracture, due to wrinkles, produced during forming. In this paper, the sustainability aspects involved in the warm forming of TWB were discussed with respect to energy and material savings. The results show a reduction of about 50% punch load in a hydraulic press during deep drawing under warm forming conditions. This paper addresses the questions related to the implications of thickness ratio on the weld line movement and further shows how material savings of nearly 33% has been obtained. It also discusses about the carbon emissions during manufacturing of raw materials and the recycling benefits of stainless steel, so as to minimize emissions at the production stage itself during raw materials production.

Machines, automobiles, robots, etc., usually employ epicyclic gear trains (EGTs) in their transmission systems. The graph theory-based representation of an EGT has enabled in the development of structural synthesis algorithms for enumerating all the feasible concepts in the form of non-isomorphic graphs. The enumerated EGTs are of importance to an EGT designer during the conceptual stage of design. One of the important steps in the structural synthesis is that of detection and elimination of those graphs that contain degenerate structure/s as subgraphs. In this work, graph theory-based methods are presented for the detection of degenerate EGT graphs among the enumerated collection. It is shown that the graph of any degenerate structure can be evolved to that of EGTs of single/multi-degree of freedom (SDOF/MDOF) through the addition of graph components thereby giving rise to degenerate EGTs. Through a series of statements, it is concluded that degenerate EGTs can be divided into two classes: those with one or more cut vertices and those without any cut vertex. A simple decomposition scheme is formulated which when applied to any EGT graph would determine whether or not it contains a degenerate structure. The proposed method is applied as a test for degeneracy in the structural synthesis of SDOF and MDOF EGTs, and the results for nondegenerate graphs are verified to be correct.

The cleanroom is used for manufacturing of high accuracy, high sensitivity, and small-sized Micro-electro-mechanical systems such as micro-sensors and micro-actuators. It is a controlled environment, in which the contaminant particles, temperature, and humidity are maintained within limits recommended by the International Standards Organization (ISO). The design, construction, and assessment of the design sustainability and energy sustainability during full production time and idle-time of a cleanroom are reported in this paper. Evaluation of design sustainability of the present cleanroom was carried out through experiments on the time taken for scavenging of contaminant particles out of the positive pressure cleanroom by the air handling units. The cleanroom designed in the present work scavenges all sizes of contaminant particles to as low a value as 2% of the prescribed ISO class within 10 min. Assessment of energy sustainability of the cleanroom was done using two metrics of net total pressure efficiency (NTPE) and total energy performance index (TEPI) through a novel adaption of their concepts to the cleanroom. With measured values of NTPE of about 35% and TEPI of 5.6 for the entire MEMS production subarea of the cleanroom consisting of twelve fan filter units, the results of the present work are in close agreement with these metrics reported for a single fan filter unit in the literature. Finally, a novel adaption of the existing life cycle assessment (LCA) methods to cleanroom resulted in an environmental sustainability score of 56.1/60. The details of the work done on the environmental sustainability of the cleanroom are also presented. With the rapid advancements in technology, the sustainability and feasibility demonstrated in the present work through the novel way of applying lifecycle assessment methods, and two energy sustainability metrics to determine the efficacy of the design of a MEMS cleanroom can prove beneficial for developing economies such as SAARC and African countries.

Asymmetric parts have been in a great demand in industries and manufacturing of the same requires affluent dies. Single point incremental forming and two point incremental forming are the two methods which have been introduced to replace partially the use of expensive dies in introduction phases. But one of the major limitations of the existing methods of incremental sheet metal forming is the limiting wall angle, where a wall angle of greater than about 70° is difficult to obtain. The recently proposed solution of multi-stage incremental forming can enable obtaining wall angles close to 90° but it takes longer manufacturing time and may pose problems for materials that severely strain harden. Advance automation and robotics can enhance this task, productivity and accuracy of the part. One of the technologies evolving in manufacturing industry is Robot assisted incremental sheet metal forming. (RISF). 3 axis CNC machine and robotic manipulator can be integrated to make the process more flexible. Forming of any part with a robotic manipulator requires continuous relocation of supporting robots during machining. In this forming operation tool is given 3DOF and manipulator is given 2DOF.Tool head and manipulator sequentially relocate and affix themselves in such a way that final complex geometry can be formed. To follow the work piece geometry, adequate positioning of end effector is required. In this paper evolutionary path planning of robotic manipulator and CNC tool is presented.

In this study energy absorption characteristics are investigated for GFRP (glass fiber reinforced plastics) crash boxes made of different types of geometries viz. square, cylindrical, hexagonal and decagonalwhen subjected to an axial crush loading. Initially the crash performance characteristics of crash boxes are compared without the use of triggers. Later two different types of triggers are used in the crash boxes and a comparison is done for various types of crash boxes considering the peak force, energy absorbed and S.E.A as parameter values. The failure modes of the crash boxes are investigated and compared. The use of triggers changed the deformation pattern and energy absorption value significantly.It was observed that the effect of trigger varied with the geometry type. The use of trigger improved the energy absorption capacity for hexagonal type significantly whereas the cylindrical type showed best energy absorption when trigger was not used.

An automobile crash box is a thin walled structure made of metal or composite material which is mounted on the front region of the vehicle. Its main purpose is to absorb the energy due to collision in the event of a crash. Crash boxes made of metals like steel and aluminum are widely used whereas use of composite crash boxes is in development phase in automobile industry. In automobile industry there is always a quest to reduce the mass of the vehicle for reduction of raw material usage and also to increase fuel efficiency. Composite crash boxes provide very good weight to stiffness ratio which makes them good contenders. But the behaviour of parts made of composite material in impact or collisions has to be understood for its usage in automobile structure. Crash box plays an important role in the event of a frontal collision of the vehicle. A crash box should absorb maximum possible energy and should deform sequentially so that the deformation pattern is not random. In this paper the effect of various types of triggers is investigated for GFRP composite crash boxes. Trigger is a geometrical feature applied to the crash box with the objective of achieving the desired energy absorption, deformation pattern and peak force. A comparative study of variation of peak forces, energy absorbed, S.E.A (specific energy absorbed) was done with the variation of triggers for crash box. Force vs. displacement curves were plotted for each case providing detailed insights into the force variation during deformation.

Tailor-welded blanks (TWBs) are welded sheets consisting of different materials, thicknesses, shapes, and sizes. They are subjected to forming at a particular temperature to achieve the desired sha...

An investigation to symmetry in epicyclic gear trains (EGTs) is carried out in this research. As a consequence of the graph theoretic framework for EGTs, an EGT graph serves as an isomorphic substitute for its kinematic structure. In this work, Nauty & Traces software package is employed for an EGT graph for determining the automorphism group and orbits of its vertices or edges. The procedure is applied to all the rotationally non-isomorphic graphs available in the published atlases, with and up to 7 links and results are presented. It was inferred that only few percentage of distinct EGT chains (graphs) exhibit any symmetry at all.

This paper deals with optimizing geometric parameters such as thickness ratio and weld line location, to minimize the movement of weld line during the stamping of tailor-welded blank (TWB) components. Weld line movement (WLM) is an important aspect to consider; otherwise, it leads to wrinkling and other forming-related problems. The major contributors to WLM are thickness ratio, weld line location, and strengths of the respective blanks. Selective heating is a recent technique adopted to reduce the material properties of the higher strength TWB blank by heating it locally, thus allowing a shift in the weld line. In this work, laboratory and simulation experiments were conducted under warm forming conditions on the TWB blanks. Experiments were also conducted by placing the weld line at an offset distance of ± 1 mm from the centre of blank. The situation is to choose the best possible value among thickness ratio and weld line location under the influence of selective heating to minimize the WLM. The objective function of WLM is obtained from the MINITAB statistical software by conducting ANOVA method. The optimum values of the parameters were obtained by minimizing the objective function.

Single point incremental forming (SPIF) is a novel and potential process for sheet metal prototyping and low volume production applications. This article is focuses on the development of predictive models for surface roughness estimation in SPIF process. Surface roughness in SPIF has been modeled using three different techniques namely, Artificial Neural Networks (ANN), Support Vector Regression (SVR) and Genetic Programming (GP). In the development of these predictive models, tool diameter, step depth, wall angle, feed rate and lubricant type have been considered as model variables. Arithmetic mean surface roughness (Ra) and maximum peak to valley height (Rz) are used as response variables to assess the surface roughness of incrementally formed parts. The data required to generate, compare and evaluate the proposed models have been obtained from SPIF experiments performed on Computer Numerical Control (CNC) milling machine using Box–Behnken design. The developed models are having satisfactory goodness of fit in predicting the surface roughness. Further, the GP model has been used for optimization of Ra and Rz using genetic algorithm. The optimum process parameters for minimum surface roughness in SPIF have been obtained and validated with the experiments and found highly satisfactory results within 10% error.

Incremental forming is a novel sheet metal forming process in which the sheet is deformed in a series of incremental steps with a small hemispherical punch. The motion of the tool is controlled by a computer numerical control (CNC) part program and the process is carried out on a CNC milling machine. The present paper discusses the effect of various process parameters on forces, plastic strain and thinning through numerical simulations. Three important process parameters, namely the punch diameter, step depth and wall angle are used as input parameters. Taguchi orthogonal arrays are used to plan the number of simulations to study the effect of process parameters on the response variables. The numerical simulations are performed using finite element software LS-DYNA. Initially, the tool path is generated using Pro-manufacturing software and is modified into suitable format for numerical simulations using Python and MATLAB programming. The results show that the wall angle has maximum influence on al...

Incremental sheet metal forming (ISF) process is an emerging technology used in various sectors of industries to reduce the cost of dies and for flexible manufacturing. Robotic assistance in ISF, like in other manufacturing processes, has been attempted by several researchers to make the processes more flexible and efficient. Hence, in addition to the conventional ISF process description, a detailed account of robotic assistance in ISF is also explained here. When a serial robot is used as a machining platform, most of the original tooling and machinery can be preserved. On the other hand, when such machining process is adopted to be used for ISF, due to varying forming forces and as stiffness of the robot may not be high, forming tool may deflect causing error in tool path, which in turn results in errors in geometry of the part. In order to compensate for this deflection, knowledge about the level of stiffness of robot in all its configurations and prediction of forces with sufficient accuracy are required. Hence, developing a procedure to predict forming forces is explained here. This will include dynamic analysis of a two-degree-of-freedom serial manipulator which is to be used in the forming operation. Dynamic analysis will give variation of forces with respect to the movement of links and joints used. Using the results of dynamic analysis, dimensional synthesis can be done which will also include determining link lengths. Inverse dynamic model is used to obtain the joint torques and forces for desired acceleration of platform using the state variables of the robot, i.e. the position and velocities. After finding out dimensions of link and joints, workspace volume is to be found out. To investigate the reliability of the proposed design for dynamic performance, multi-body dynamic (MBD) analysis and simulation of the manipulator is done using COMSOL Multiphysics. In the present work, task of the robot is to carry and manipulate sheet metal on which incremental forming operation is performed. Robotic manipulator manipulates the sheet with respect to 3-axis CNC tool to get a final shape. We mainly focus on dynamic analysis of a serial two-degree of freedom (2-DOF) robot used for incremental sheet metal forming.

Single-point incremental forming is the most economical process to make the sheet metal prototypes and low volume production without any dedicated dies and simple tooling. The surface finish of the parts produced in this process gets affected by various process parameters. To get the proper quality of parts for functional applications, it is important to understand the effect of various process parameters on part quality. Another drawback with this process is long processing time, which also gets affected by different process parameters. Thus, the first objective of this article is to study the effect of various process parameters on surface roughness and manufacturing time. Second objective is to carry out the multi-objective optimization to get optimum process parameters. For this, detailed experiments are conducted using Box–Behnken design. The effects of step depth, tool diameter, wall angle, feed rate and lubricant type on surface roughness and processing time have been investigated. Based on experimental data, mathematical models have been developed for both the response variables, namely, surface roughness and manufacturing time. Since the response variables are mutually exclusive in nature, multi-objective optimization algorithm (non-dominated sorting genetic algorithm-II) has been used to get optimum process parameters. The Pareto front obtained from this algorithm helps the manufacturing engineer to select optimum process parameters in single-point incremental forming process.

Tailor-Welded Blanks (TWBs) are obtained by welding together sheets of same or different metals of different thicknesses to produce a single blank prior to subjecting it to a forming process. Designers nevertheless need to overcome the difficulty faced in the forming of TWBs due to material property changes in the two parent metal sheets which is leading to weld line shift. The present work is aimed at studying the formability behavior of TWBs of two different steels viz. Interstitial free steels and Dual phase steels with respect to laser welding and Tungsten inert Gas welding. The formability of the TWBs and the base materials has been studied for differential strengths and analyzed with the help of LS Dyna Non-linear Finite element software. From the results, it was found that the weld shift can be altered by varying the strength parameters of the parent materials.

This work emphasizes on the geometric and dimensional accuracy of cylindrical tailor welded blank (TWB) components manufactured under warm forming conditions. In this work, TWB sheet material made of austenitic stainless steel (ASS 304 Grade) and deep drawing steel (IS 513 grade) materials were TIG welded before subjecting to stamping operation. Numerical simulations were validated with experimental results. Simulation results were analyzed to check the thickness variation and stress distribution within the component which otherwise would be difficult to measure experimentally. Measurements in terms of geometric accuracy gave encouraging results. The roundness and perpendicularity measurements indicated better accuracy whereas, cylindricity value has slightly improved. However, dimensional accuracy of the parts in terms of thinning, cup height and diameter has deteriorated. It was found that the spring back effect played a significant role in the deterioration of dimensional accuracy. Presence of residual stresses might be the cause for this effect; further studies are needed to address this issue.Copyright © 2017 by ASME

The closed loop feedback control system of an Automated Manual Transmission (AMT) electro-pneumatic clutch actuator is used for intelligent real time condition monitoring, enhanced diagnostics and prognostic health management of the dry clutch system, by integrating with the existing gearbox prognostics observer. The real-time sensor data of the clutch actuator piston position is analyzed for monitoring the condition of the clutch system. Original parameters of the new clutch are stored in the Electrically Erasable Programmable Read-only Memory (EEPROM) of the AMT controller and the real-time data is used by the observer for assessing the degradation/wear of the frictional clutch parts. Also, clutch slip during torque transmission is monitored, using the engine speed and the gearbox input shaft speed from Controller Area Network (CAN). Condition monitoring of clutch system provides enhanced prognostic functionality for AMT system which ensures consistent clutch performance, gear shift quality and timely warning for recalibration, repair and/or replacement of the critical wear and tear parts. Also, systematic analysis of the monitored data provides an accurate diagnosis of a developing fault. Thus, with the advanced control systems in place for AMT, a closed loop feedback based condition monitoring system is modelled for improved diagnostics and prognostics of AMT clutch system.

This paper focuses on investigation of formability, thickness distribution, strain distribution, and microstructural changes of extra deep drawing (EDD) steel in the single-point incremental forming (SPIF) process. For this, pyramidal frustums with varying wall angle along the depth were formed till the fracture. The parts were designed by rotating circular, elliptic, parabolic, and exponential curve segments. The varying wall angle pyramidal frustums (VWAPF) can minimize the number of experiments required to find the maximum wall angle compared to conventional constant wall angle pyramidal frustums. The maximum wall angle corresponding to fracture depth and thickness distribution along the depth was measured for parts with different generatrices. The maximum formable wall angle was found to be 73 ± 2°. Experimental thickness distribution was compared with the thickness distribution obtained from numerical simulations using the LS-DYNA software. A good correlation was found between experimental and numeri...

An integrated finite element analysis–evolutionary algorithm simulation approach is proposed in this work to model the density characteristics of the three-dimensional printing, specifically for selective laser sintering process. The approach consists of modeling sintering phenomenon by finite element analysis simulation, which is further fed into an evolutionary algorithm cluster comprising genetic programming. The integrated approach is useful to model the functional relationship of density characteristic of selective laser sintering–fabricated components with respect to laser power, scan velocity and scan spacing. Performance of the proposed model is evaluated against the actual results obtained from the literature. We find that our proposed finite element analysis–evolutionary algorithm model is able to model the selective laser sintering process very well, which can be used to complement the analytically and experimentally obtained results. For the validation of the robustness of the model, we also conducted sensitivity and parametric analyses and investigated the specific influence, and variation, of each of the input process parameters on the density of the selective laser sintering–fabricated component. It was found that scan spacing has the least influence, whereas scan velocity has the highest influence on the density of the selective laser sintering–fabricated component. Non-linear relationships unveiled between the process parameters highlight the capability of the model in simulating the density characteristic of the complex selective laser sintering process in uncertain input conditions.

In incremental sheet forming (ISF) the tool moves along the specified trajectory and deforms the sheet in to required shape. In the present paper incremental forming process is simulated using explicit finite element software LS-DYNA. The computational time for the simulation of ISF is very long due to long tool paths used in the process. To overcome this problem time scaling and mass scaling are used in the present paper. The effect of time scaling and mass scaling on forming forces, plastic strain, internal energy, kinetic energy, thickness distribution and computational time is studied. A continuously varying wall angle conical frustum is simulated for this study. Extra deep drawn steel, which is most commonly used in automotive applications, has been used as a blank material. Thickness distribution obtained with different mass and time scaling factors is compared with experimentally measured thickness distribution.

The present work investigates, by both mathematical modelling and experiment, the contribution of bonding between the filaments to the strength of the parts manufactured by fused deposition modelling (FDM). A mathematical model for neck growth between cylindrical filaments is derived based on viscous sintering for cylindrical filaments. Theoretical ultimate tensile load is determined from the layer thickness information and predicted average final neck size between filaments. The experimental ultimate tensile load is obtained by conducting a simple tension test with two different build directions. Agreement between theoretical and experimental ultimate tensile load and scanning electron microscope (SEM) photomicrographs of the fracture surface indicate that the strength of the FDM part is primarily due to intra-layer bonding, inter-layer bonding and neck growth between filaments. It also indicates that the total time and heat available to the filaments are just sufficient to grow necks but not enough to f...

In the present work, the relationships between two important quality objectives, namely, strength and volumetric shrinkage of fused deposition modelling (FDM) parts and selected process parameters, namely the build interior, the horizontal build direction and the vertical build have been determined through a minimum number of experiments based on face centred central composite design. Specimens have been manufactured on an FDM machine and tests have been conducted to evaluate strength and volumetric shrinkage. The relationship for each of these two response variables in terms of the three process parameters has been constructed using analysis of variance. The resulting two objective functions are optimised simultaneously using the non-dominated sorting genetic algorithm. In order to validate the Pareto optimal solution, three randomly chosen experimental runs at intermediate parameter values (other than design of experiments levels) were repeated and good correlation was found between these results and th...

This paper reports the simulation based analysis results of air flow in a MEMS clean room aimed at predicting the air borne distribution of 0.5 μm particles as per the ISO standard. These particulate contaminants, if not flushed by proper design of the ventilation system of the clean room can get deposited and accumulated on the MEMS devices under fabrication, contributing possibly to the affected functionality of the device, particularly high precision devices such as single cantilever type precision MEMS sensors and actuators. The results of computational fluid dynamics (CFD) based flow analysis done in COMSOL™ estimated for adverse conditions such as a desired ISO-5 cleanliness degrading to ISO-8 cleanliness due to poor maintenance have been presented. Based on the flow conditions, conclusions on the particle accumulation have been drawn.