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The Effects of Low Frequency on the Microstructure and Mechanical Properties of High-Strength Al-Mg Aluminum Alloys by Wire and Double-Pulsed Arc Additive Manufacturing
An innovative and high deposition efficiency process, the double-pulsed arc additive manufacturing process, is used to produce high-strength Al-Mg wall components. This dissertation investigates the electrical parameter acquisition, bead appearance, porosity morphology, microstructure and mechanical properties of additively manufactured high-strength Al-Mg wall components and how these are affected by the low frequency of the double-pulsed arc additive manufacturing process. Then, using this process at different low frequencies of 0, 1, 3, 5, 7 and 9 Hz, multilayer deposition experiments were performed. It can be observed that the deposit porosity is obviously eliminated compared with cold metal transfer (CMT) process. The bead appearance of the deposited aluminum wall varies clearly with low frequencies, and at a low frequency of 3 Hz, its appearance is the best of all. The optical observation of microstructure proves that the average grain size varies significantly with low frequency, and at a low frequency of 1 Hz, it is the smallest. In addition, the deposited wall showed maximum mean microhardness and maximum ultimate tensile strength at a low frequency of 3 Hz. Considering the deposited porosity and mechanical priorities, double-pulsed arc additive manufacturing with a frequency of 3 Hz is more suitable for making high-strength Al-Mg wall components than at other low frequencies.
Effects of Holding Time on the Sintering of Cemented Tungsten Carbide Powder and Bonding with High-Strength Steel Wire
Cemented tungsten carbide (WC-10Co) and high-strength (AISI 4340) steel were successfully bonded by hot compaction diffusion bonding at a low temperature. The effects of holding time (5-50 min) on microstructure and mechanical properties of the sintered carbides and bonding strengths of the dissimilar bilayered composite materials were examined. The results show that the mechanical properties of the carbides increase, but the bonding strength increases firstly and then decreases with the increase in holding time. The maximum density and hardness achieved are 95.92 and 99.5%, respectively. A transitional layer forms at the interface as a result of elemental interdiffusion. The depth of the layer increases with the increase in holding time. The optimal bonding time is determined to be 40 min at a temperature of 1200°C and a pressure 160 MPa, by which the maximum bonding strength of 204 MPa of the WC-10Co/4340 steel joints can be achieved.
Texture and Strain Measurements from Bending of NiTi Shape Memory Alloy Wires
Abstract not provided
Effects of Hydrogen Charging on the Phase Transformation of Martensitic NiTi Shape Memory Alloy Wires
Abstract not provided
Characterization of Thermomechanically Processed High-Temperature Ni-Lean NiTi-20 at.% Hf Shape Memory Wires
Abstract not provided
Three-dimensional electric field calculations for wire chamber using element refinement method in ANSYS
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Degradation Processes and Mechanisms of PV Wires and Connectors.
Abstract not provided.
Shape-memory characterization of NiTi microtubes fabricated through interdiffusion of Ti-Coated Ni wires
Abstract not provided
Strategies for a scalable multi-robot large scale wire arc additive manufacturing system
Not Available
Material properties and mechanical behaviour of functionally graded steel produced by wire-arc additive manufacturing
Metal Big Area Additive Manufacturing is an additive manufacturing technique based on Gas Metal Arc Welding (GMAW) with the option to use many shielding gases, and materials. The system is equipped with a dual torch design allowing for printing different materials; in our study, AISI 410 stainless steel and AWS ER70S-6 mild steel are both printed in the same component. Different print strategies were designed to highlight changes in material and mechanical properties. Deformation behaviour of a materials’ interface was analysed by two-dimensional digital image correlation of uniaxial tensile specimens in displacement-controlled tests. Instances of non-homogeneous local strains adjacent to the interface are observed, as well as variability in mechanical behaviour and microstructure based on location within the print. Optical and electron microscopy are used to evaluate three microstructural zones in a 5 mm range of the interface between mild steel and stainless steel. Areas far from the interface produced polygonal ferrite and pearlite, while areas close to the interface produced acicular ferrite and bainite. Chromium redistribution profiles are dependent on the print strategy used, as shown by scanning electron microscopy with Energy dispersive spectroscopy. Evidence produced via electron backscatter diffraction is shown to support the argument that transformation induced plasticity is not the cause for the non-homogeneous deformation.
Microstructure, deformation and fracture mechanisms in Al-4043 alloy produced by laser hot-wire additive manufacturing
Not Available
Formulation and numerical analysis of a fully-coupled dynamically deforming electromagnetic wire
Here, an electromagnetic beam model is developed for the simulation of actuated electronic textiles. The beam is solved using a nonlinear director-based kinematic description with additional temperature and electric potential fields along its length. The three fields are fully coupled by mutual dependences on the deformation, Lorenz force, back electromotive force, temperature dependent constitutive responses, and the Seebeck effect. Instead of solving Maxwell's equations in full detail, a quasistatic approximation is used to solve the electric potential in the presence of a moving material medium. The current-carrying beam approximation is used to further simplify the solution space for the potential. While this formulation alleviates the spatial and temporal discretization restrictions, the coupled problem is an index-1 semi-explicit Differential Algebraic Equation requiring special treatment. The time dependent problem is solved using different Runge-Kutta methods. Diagonally implicit Runge-Kutta methods and explicit Runge-Kutta methods using implicit solution of the electric potential problem are explored. The finite element model is implemented using the open source package FEniCS, which is able to automatically generate the linearizations of the multiphysics equations required for the implicit solutions. A model problem is constructed with which to test and analyze the physical formulation and numerical solution techniques. The time stepping methods are verified using the convergence orders of the higher-order Runge-Kutta methods. Runtime comparisons show that the explicit methods are generally more computationally efficient than the implicit schemes used for this problem. For the implicit schemes, a staggered solution is significantly faster than a monolithic solution at most time step sizes. However, at very large time steps, such as those that would be used for dynamic relaxation, the monolithic solution can be more efficient than the staggered solution.
Prediction of Ni-based alloy microstructure in wire arc additive manufacturing from cellular automata model
Not provided.
Interactions between martensitic NiTi shape memory alloy and Nb nanowires in composite wire during t
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