Joining Metallurgically Incompatible Metals

A method for joining a second alloy material to a first alloy material where the two alloy materials are incompatible, comprising forming three successive interface layers over a substrate comprising the first alloy material, followed by forming a structure of the second alloy material over the interface layers, wherein the composition and deposition method for each of the layers is selected so that brittle intermetallics are not formed between elements of the adjacent layer compositions

Numerical Investigation of Thermo-Mechanical Field during Selective Laser Melting Process with Experimental Validation

In this study, thermo-mechanical simulation was conducted to predict thermal and stress behavior in Selective Laser Melting (SLM). Temperature-dependent material properties for processed material 304L stainless steel were incorporated into the model in order to capture the change from powder to fully dense solid stainless steel. Temperature and thermal stress history were tracked under conditions of different parameter sets which were designed to reduce defect formation. The thermal model predicted the temperature history for multi-track scans under different process parameters, such as laser power, effective scanning speed and hatch spacing. Subsequently, the corresponding melt-pool size, solidification rate and temperature gradients could be calculated from simulated temperature data. These three parameters from the simulation were compared with experimental melt pool size, grain structure and cell spacing data obtained from a Renishaw AM250. The experimental data were also used to determine unknown simulation parameters required by the continuum model, e.g., the optical penetration depth and thermal conductivity multiplier for the molten region. This allowed the simulation model to accurately predict melt pool size and solidification structure of SLM 304L stainless steel. Simulated stress showed that the subsequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. This work will provide insight for studying microstructure morphology, residual stress and deformations in the SLM process of 304L stainless steel

Optimal Design Rules Applied To The Design Of High-speed Mechanisms Under Deflection And Stress Constraints

Presented in this paper are two approaches for the design of flexible mechanisms under stress and deflection constraints. Based on the optimality conditions derived in this paper, two procedures are developed to design the minimum weight of mechanisms subject to stress and deflection limitations. The first procedure is the improvement of Thornton\u27s design process r 17), and the second procedure is based on the interpolation technique. Several design examples are also presented to demonstrate these methods

Review of AM Simulation Validation Techniques

Due to the complexity of Additive Manufacturing (AM), it can require many trial runs to obtain processing parameters which produce a quality build. Because of this trial and error process, the drive for simulations of AM has grown significantly. Simulations only become useful to researchers if it can be shown that they are true representations of the physical process being simulated. All simulations have different methods of validation to show that they are an accurate representations of the process. This paper explores the various methodologies for validation of laser based metal AM simulations, focusing mainly on the modeling of the thermal processes and other characteristics derived from thermal history. It will identify and explain the various validation techniques, specifically looking at the frequency of reported use of each technique

Depth of Cut Monitoring for Hybrid Manufacturing using Acoustic Emission Sensor

Laser Metal Deposition LMD is a hybrid manufacturing process consist of a laser deposition system combined with a 5-axis CNC milling system. During laser deposition many parameters and their interaction affect the dimensional accuracy of the part produced, powder flow rate, laser power and travel speed are some of these parameters. Sensing the acoustic emission during milling marching gives feedback information regarding depth of metal being cut subsequent part dimensions, if an error in dimensions is found certain actions, such as remaching, close loop control, or laser remelting can be carried out to correct it. Thus a reliable hybrid manufacturing management system requires that a depth-of-cut detection system be integrated with the milling machine architecture. This work establishes, first a methodology to detect an acoustic emission signal, so that the acoustic emission characteristics of the milling could be analyzed. Second, it sought to relate these acoustic data to machining parameters to detect depth-of-cut

Review of Metal AM Simulation Validation Techniques

Due to the complexity of metal AM (additive manufacturing), it can require many trial runs to obtain processing parameters which produce a quality build. Because of this trial and error process, the drive for simulations of AM has grown significantly. A simulation only becomes useful to researchers if it can be shown that it is a true representation of the physical process being simulated. Each process being simulated has a different method of validation to show it is an accurate representation of the process. This paper explores the various methodologies for validation of laser-based metal AM simulations, focusing mainly on the modeling of the thermal processes and other characteristics derived from the thermal history. It will identify and explain the various validation techniques used, specifically looking at the frequency of reported use of each technique

Experimental Investigation of Laser Metal Deposition of Functionally Graded Copper and Steel

Laser metal deposition is an emerging technology for producing fully dense metallic parts. This process shows a promising future for the deposition of functionally graded steel - copper alloys. Good thermal conductivity of copper and a high wear resistance of steel can be achieved in dies and cores. However, to accomplish this, there are many issues to be resolved, such as the formation of an undesirable phase, solidification cracking, porosity at the interface and difference in thermal coefficient of expansion between steel and copper. The influences of process variables, such as laser power, laser scan speed, composition, powder flow rate, on the success of the process, should be studied

General Rules for Pre-Process Planning in Powder Bed Fusion System -- A Review

Powder bed fusion (PBF) is one of the current additive manufacturing techniques that can fabricate almost fully dense functional metal components. Through a layer by layer fabrication methodology, complex geometries to meet the requirements of aerospace, automotive, biomedicine industries, etc. can be produced. The success of a build largely depends on having a flawless pre-process planning, including build orientation selection, support structure optimization, process parameter chosen, etc., which closely relates to the quality of the final products. Geometric inaccuracy and poor surface quality can occur due to a bad build plan. This review presents the crucial general planning rules for the build process. Build orientation selection, support structure optimization, and process parameter chosen in terms of residual stress reduction are the mainly concerns, which have been surveyed and discussed. The overall objective of this work is to help setup build plans that can ensure precise dimensions and high surface quality among the built components