Temperature Distribution during Single Pass Multi-Layer Welding in Additive Manufacturing

Single bead welding, is a high-speed welding process that is used for manufacturing of thin walled components. Its application is a vast field of research to assess its ability to manufacture complex products. This is different from the conventional welding of two similar and dissimilar materials in which the focus lies on joining of the two metals. This process is used for the creation of a completely new component by weld bead deposition of material

Effective Handover Technique in Cluster Based MANET Using Cooperative Communication

Mobile ad hoc networks (MANETs) are becoming increasingly common now a days and typical network loads considered for MANETs are increasing as applications evolve. This increases the importance of bandwidth efficiency and requirements on energy consumption delay and jitter. Coordinated channel access protocols have been shown to be well suited for MANETs under uniform load distributions. However, these protocols are not well suited for non-uniform load distributions as uncoordinated channel access protocols due to the lack of on-demand dynamic channel allocation mechanisms that exist in infrastructure based coordinated protocols. We have considered a lightweight dynamic channel allocation algorithm and a cooperative load balancing strategy that are helpful for the cluster based MANETs and an effective handover technique to improve the increased packet transmission mechanism. This helps in reduce jitter, packet delay and packet transfer speed, we use a novel handover algorithm to address this problem We present protocols that utilize these mechanisms to improve performance in terms of throughput, energy consumption and inter-packet delay variation (IPDV)

Manufacture of Functionally Gradient Materials Using Weld-Deposition

When the inherent inhomogeneity of Additive Manufacturing techniques is carefully exploited, the anisotropy transforms into the desired distribution of the properties paving the way for manufacture of Functionally Gradient Materials. The present work focuses on using welddeposition based Additive Manufacturing techniques to realize the same. Mechanical properties like hardness and tensile strength can be controlled by a smaller degree through control of process parameters like current, layer thickness etc. A wider control of material properties can be obtained with the help of tandem weld-deposition setup like twin-wire. In tandem twin-wire weld-deposition, two filler wires (electrodes) are guided separately and it is possible to control each filler wire separately. The investigations done on these two approaches are presented in pape

Experimental Studies on Assessment and Reduction of Surface Waviness for Weld Deposition based Additive Manufacturing

Weld deposition based Additive Manufacturing (AM) is one of the economical and efficient ways for fabricating mesoscale metallic objects. This study focuses on the use of Gas Metal Arc Welding (GMAW) based weld-deposition for obtaining the near-net shape of the object, subsequently to be finish machined to the final dimensions. The near-net shape in most of the techniques is obtained through a series of weld-deposition and face milling for each layer. The interlayer face milling is needed because of the uneven surface produced during welddeposition. However, this operation increases the total time of the process and also reduces the material utilization. Hence, this study focuses on reducing the surface waviness of a given layer eliminating/minimizing the need for interlayer face milling. The surface waviness is caused mainly due to improper process parameters and repetitions/gaps arising in area-filling paths. While there is sizable literature on suitable process parameters, the effect of the area-filling path on the surface waviness is not fully analysed. The current work presents different experimental studies carried out for studying the effect of different areafilling features on the surface waviness. Accordingly, three area filling patterns namely spiral-in, spiral-out, and rectilinear with different surface waviness have been described. The material utilisation is measured using a 3D scanner and face milling. Both approaches gave similar results signifying the suitability of 3D scanner approach. Subsequently, the multi-layer experiments are also carried out for different area filling patterns and surface waviness is measured for 5-layer. Rectilinear is found to be the best. In the rectilinear pattern, different overlapping methods namely offset overlap, and criss-cross overlap is also explored. Among these methods, criss-cross shows the best Rt value

Evaluation of Rapid Manufacturing Solutions for Improved Knee Implants Using Finite Element Analysis

Knee joint is an important part of human body; failure of knee joint may occur mainly because of surface to surface contact of femoral and tibial surfaces owing to the dry out of bursae fluid. The damaged surfaces must be replaced by artificial implants made of metals, ceramics, or composite materials. This process is known as total knee replacement. Three-dimensional physical model of the knee implant is modeled in NX Unigraphics 7.5 software. This model is imported to ANSYS-WORKBENCH 13, solver used is MECHANICAL-APDL, which is based on Finite Element Method (FEM). The metallic implant is made of porous inside and dense outside. This reduces the overall weight of the implant. The failure of bearing component in knee implant is due to high stresses at the contact regions of femoral component and polyethylene insert causes wear and decreases the life of the implant. New improved knee joint implant is made, which reduces the stresses at the contact regions and increases the life of knee implant. The stiffness of artificial implants is around 110 GPa to 210 GPa, while that of the human bone is around 17 GPa. A metallic implant made of titanium-β alloy having stiffness of around 40 GPa to 60 GPa is used. This reduces the effect of stress shielding between the bone and implant

Manufacturing of Large Metallic Components through Wire and Arc Additive Manufacturing(WAAM)

Metal additive manufacturing have been in trend due to its ability to produce components at reduced cost and low buy-to- y ratio. There are various techniques employed for metal additive manufacturing depending on energy source and type of raw materials used. Based on raw materials, metal additive manufacturing can be classi ed as wire-based, powder-based and sheet-based (laminated object manufacturing). Amongst these three, wire based systems have higher material e ciency and high deposition rates. They also better suited for continious and uncluttered material supply. Hence, they are most suitable for large components. These wire based systems can be used in conjuction to di erent energy sources like Laser, Electron Beam and Arc. WLAM (wire and laser based additive manufacturing), EBAM (electron beam additive manufacturing) and WAAM (wire and arc based additive manufacturing) are examples of each of these energy sources respectively. In this study, Weld-depsotion based WAAM is chosen. The objective of this work is to fabricate large (greater than 1m in size) metallic components using WAAM process. Parameter study, kinematic setup for such working volumes and thermal analysis of deposition process to minimize distortions are some of the related aspects. Sample components in both multi-pass and single-pass geometries were also fabricated successfuly. This work was mainly carried out for mild steel (ER70S6); some priliminary studies on extending this to IN625 are also presented. Overall, this thesis presents the sutiability of WAAM in conjuction with a robotic or CNC type kinemetic setup to produce large metallic components

Thermo-Mechanical Analysis and Characterization of Wire Arc Additive Manufactured Components

Mechanical components are typically isotropic when manufactured by traditional methods such as casting, forging, etc. However, complex geometries would be difficult with these methods. In order to fabricate the complex components, various methods have been suggested. One of such methodsis weld based additive manufacturing wherein welding is used to join the material selectively at the different locations. Mechanical tests are usually employed in investigational work in order to obtain information for use in design and manufacturing to ascertain whether the material meets the specifications for its intended use, to produce desired mechanical properties like hardness and tensile tests The intention of performing a simulation or numerical model is to predict the physical performance of an existing process. On the other hand, it may be essential to compromise the results in terms of accuracy, computational time of the model. The aim of the current work is to survey and develop a modeling method to simulate the deposition of a single straight bead and implementing the same towards constructing thin wall components using the finite element analysis. The simulating phenomenon is carried out numerically and followed by DFLUX subroutine. The model must be efficient and reliable enough to be functional in the designing and path planning of the fabricating features. In addition, a transient thermal distribution of deposited weld metal is modeled analytically in aspects of various heat sources. Importantly the heat distribution of the Goldak’s heat source is explored to improve the results of the experimental analysis. An attempt has been made to correlate the microstructural analysis with the modeling results. Hence the phase proportion, deformed shape, residual stresses, the microstructural analysis could be evaluated

Determination of Process Parameter for Twin-Wire Weld-Deposition Based Additive Manufacturing

Various energy sources are available for sintering and/or depositing the material in additive manufacturing for metallic objects. These can be mainly categorized as laser based, electron beam based and arc based. While laser and electron offer better surface finish, it is possible to achieve high deposition rates in arc based weld-deposition. The inferior surface finish can be compensated by going for a hybrid system, combining deposition and machining. Twin-wire based weld-deposition, used in the present work, makes it possible to even realize functionally gradient material matrix; the use of two different filler materials into a single weld-pool makes this possible. Wire speed, torch speed and filler material are important factors that effect the composition of the deposited volume. Determination of the operating range and effect of these process parameters therefore is important to control the properties of the weld-deposited gradient objects. The current work presents the material composition of two filler materials ER70S6 and ER110SG with different wire speed and torch speed. Deposited material elemental compositions were analyzed using ED-XRF machine

Use of fractal curves for reducing spatial thermal gradients and distortion control

In Additive Manufacturing, the desired geometry is achieved by gradual and sequential addition of material. This evolutionary nature of AM, which facilitates the fabrication of complex geometries, also results in distinctive thermal evolution for each unit of material added. An asymmetry in the heat gradients and the resulting thermal imbalance can result in residual stresses and distortions. This thermal imbalance can be mitigated by controlling the spatial spread of the heat inside the system. The aim of the current work is to delve into the fundamental behavior of heat gradients and look at ways to mitigate these gradients in a manner that is applicable to a wider spectrum of setups and scales. Hence, the focus of the current work is on regulating the area-filling paths (scan patterns) to control the spatial distribution of heat. It is hypothesized that fractal area-filling curves, like Hilbert, due to their continuous and recursive nature, can help in better heat distribution and reduce residual stresses and distortions. This concept is actualized for the Wire and Arc Additive Manufacturing (WAAM) process through simulation and experimental validation. Three different geometries and each at three different dimensional scales were taken up for study. For each of these geometries, the area-filling paths were generated in Zigzag, Contour (out-to-in) and Hilbert area-filling methods. Based on the data extracted from the simulation of these cases in Simufact software, the Hilbert pattern was found to have minimal thermal gradients in all cases. This favorable behavior of Hilbert was further corroborated with the help of experiments using weld deposition of the geometries. For the Hilbert area-filling, the distortions are reduced to values 41 % - 53 % for scaled-up, 53 % - 63 % for unscaled and 80 % - 93 % for scaled-down. These results validate the correlation between the differential temperature and distortion and the ability of fractal curves like the Hilbert curve for achieving better thermal distribution, decreasing the differential temperature. © 2022 The Society of Manufacturing Engineer