Publications

Manufacturing of parts and products regardless of their shape, geometric features and materials involves a series of processes and operations. Nowadays, it is broadly recognized through the industrial sectors that many manufacturing techniques which are currently implemented in fabricating products lead to production of industrial waste. Lean manufacturing (LM) is a business template that has philosophies designed to eliminate waste in the manufacturing process...

The chip formation in machining operations is commonly accomplished by a combination of several elements working together to complete the job. Among these components, cutting tool is the key element that serves in the front line of cutting action. Cutting action becomes a challenge when it comes to machining difficult-to-cut materials. Titanium and its alloys are among the most difficult-to-cut materials which are widely used in diverse industrial sectors...

Titanium and its alloys are outstanding materials of choice, and their applications are rapidly growing worldwide in high-value markets such as aerospace, marine, power generation, heat exchangers, automotive and biomedical industries. They owe their popularity to their superior characteristics such as high strength to density ratio, also known as high strength to weight ratio or specific strength, as well as high corrosion resistance. Titanium alloys are used in aerospace industry to protect the fuselage, especially in military aircraft, from corrosion and heat damages caused by air friction in supersonic and hypersonic speeds...

One of the most significant faults that can occur during the fused filament fabrication (FFF) additive manufacturing process is a loss of power. After such an event there is often no straightforward way to resume the 3D print, and the incomplete part must be discarded. Existing solutions depend on a battery back-up or non-volatile memory but may be insufficient when the interruption occurs during an active print motion. In the present paper, a new method is proposed and tested which utilizes computer vision to determine the precise layer the failure occurred on, and the precise location of the nozzle at the time of loss of power. Print failure detection is carried out using various functions in the OpenCV library of computer vision processing tools running on an independent Raspberry Pi 5 microcomputer. This makes the system retrofittable to a large variety of machines and allows for a high degree of automation in the process. After determining the precise point of failure at the top layer, a new G-Code file is automatically generated that trims the original file and adds corrective actions that allow the print to be resumed seamlessly. Testing and experimentation showcased how the proposed system can robustly function across a variety of geometries, including straight lines, circles, curves, independent islands, and a complex puzzle piece. The puzzle piece was further tested to validate the system's functionality under various lighting scenarios, such as low-contrast conditions and high background noise. Overall, this paper demonstrates that full print resumption is possible using inexpensive, off-the-shelf components and software. The uncertainty of the system in detecting the failure point is bounded by the camera's spatial resolution, approximately 0.055 mm per pixel in the presented configuration, which confines the detected failure location to well within a single extrusion width.

Material extrusion additive manufacturing, particularly metal fused filament fabrication (MFFF), is advancing rapidly in industry. However, MFFF parts require post-process machining to meet quality standards. The layer-by-layer nature of MFFF introduces anisotropy, which affects machining performance depending on print orientation. This paper investigates the machining characteristics of MFFF 17-4PH and 316 L stainless steels. Quasi-static tensile tests, split Hopkinson pressure bar experiments, and finite element analysis were performed to determine the Johnson–Cook plasticity and damage parameters for force modeling. …

This work investigates the combined effects of multi-walled carbon nanotubes (MWCNTs) weight%(wt%), aspect ratio (AR), and surfactant content on tool wear during MQL machining using nanofluids. While advancements have been made in the application of nanofluids in machining processes, the interplay between these parameters and their influence on both nanofluids stability and tool wear has not been systematically examined. The turning operation of AISI 304 austenitic stainless steel revealed that nanofluid combinations with lower wt% and AR of MWCNTs improved tool wear performance.…

Metal additive manufacturing (AM) is an emerging technology for producing metallic parts, with metal fused filament fabrication (FFF) technique gaining attention due to its cost-effectiveness. In FFF, a filament composed of metal powder and polymeric binder is deposited layer by layer, followed by debinding and sintering to produce the final part. However, FFF parts often contain microstructural defects, with porosity being one of the most critical ones, as it significantly impacts material properties. Accurate porosity measurement is therefore essential for ensuring part quality. Various methods have been proposed to analyze the microstructure and measure the porosity of AM metals. …

The shift of additive manufacturing from pure prototyping technology to producing end-use components has raised a new challenge for mechanical design. Efficient design requires a method for predicting the strength of a fused filament fabricated (FFF) material to replace slow and costly trial and error methods. Previous studies have developed models for failure prediction in FFF materials but often only for in-plane stress analysis, not for full 3D. In the current paper, a modified Tsai-Wu (TW) criterion for full 3D failure prediction of FFF poly-ethylene terephthalate glycol (PETG) polymer was implemented both analytically and numerically. …

Fused filament fabrication (FFF) is a promising additive manufacturing method; nevertheless, the mechanical properties of its final products, particularly for end-use applications, still require enhancements. Combining FFF's low cost and well-established technology with enhanced mechanical properties would increase its competitiveness among other additive manufacturing methods. Similar to the well-established subtractive manufacturing methods, the majority of the trajectory planning algorithms developed for FFF, prioritize print time and dimensional accuracy. However, the effect of trajectory planning on the strength of parts produced through FFF has not received adequate attention. …

Metal additive manufacturing, particularly metal fused filament fabrication (FFF), presents notable advantages, including cost-effectiveness and design flexibility, which make it an attractive choice for various applications. However, the presence of porosity in metal FFF parts introduces inconsistency to mechanical properties and poses significant complications to structural reliability, potentially impacting the performance of components. This study investigates the behavior of 17-4PH stainless steel produced through FFF, focusing on how porosity affects material behavior. Experimental analyses were performed to quantify the porosity of FFF, forming the basis of a modeling approach that directly incorporates porosity by element removal within the finite element model. Algorithms for element removal were established using pore size distributions derived from microscopic analysis and image processing data. Tensile …

Metal additive manufacturing is an emerging technology for creating metallic parts, with metal fused filament fabrication (FFF) rapidly gaining popularity due to its cost-effectiveness. Despite the acceptable mechanical properties of additively manufactured metals using FFF, a significant technical challenge is the presence of undesirable porosity, which affects material performance. This study aims to model the material behavior of FFF 17-4 PH stainless steel, considering its porosity, using the Gurson–Tvergaard–Needleman (GTN) damage model. The GTN model, which incorporates the micromechanical behavior of ductile metals, shows great potential for failure prediction. The GTN model parameters were identified for both wrought and FFF 17-4 PH stainless steel through a series of proposed methods. Initial void volume fractions were determined using density measurements. The evolution of void volume …

Additive manufacturing, particularly fused filament fabrication or fused deposition modeling, has grown explosively in the past ten years. Studies have begun to form a greater understanding of the influence of the print parameters on the mechanical properties of fused filament fabricated materials. Many of these studies have shown that the material properties of fused filament fabricated components vary highly with the parameters and settings used to print them. Therefore, growing efforts have been made to predict material properties based on print parameters using a reduced set of initial tests. In the present paper, a new method has been proposed to combine these theories into a unified predictive model based upon a modified Tsai-Hill criterion. A modified version of the Tsai-Hill criterion was developed for the prediction of the yield strength of additively manufactured materials without needing to test every print …

Inspired by computer numerical control (CNC) technology and drastic changes in the world of electronics and microcontrollers, the idea of using non-cartesian coordinate system for CNC machines became a topic of interest. Non-cartesian coordinate systems provide freedom of movement in systems with large working spaces where high dimensional accuracy is not a prime concern. Applications of such systems can be found in murals, where a painting is applied to a large wall of any arbitrary build material. In the present paper, a new design was introduced to automate the process of drawing murals on large surfaces. The proposed mechanism utilized chain and sprocket to overcome the size limitations of traditionally available x-y tables. In addition to that, the developed mechanism does not utilize the common robust structures used in the conventional CNC systems and the tool motion is created using flexible …

This paper proposes a model to predict the tensile characteristics of metal fused filament fabricated (MFFF) components. The proposed model consists of mathematical, experimental, and finite element (FE) models. The mathematical model was constructed based on the composite laminate theory and was combined with experiments for basic layup of 0° and 90° raster angle to describe the behavior of MFFF parts. The FE model was built to simulate the behavior of MFFF parts in a virtual environment and its validity was verified using independent experiments for a more common layup....

Metal additive manufacturing finds its applications in various sectors, especially the automotive and aerospace industries, wherein weight reduction of components is of paramount importance with respect to performance and fuel consumption. However, additively manufactured metallic components usually undergo post-processing steps to make them ready for end use application. One of these steps is finish machining that is employed to overcome the surface irregularities and poor tolerances produced as a result of additive manufacturing (AM). These finish machining processes involve turning, milling, drilling, reaming, or grinding....

The severe operation conditions in nuclear reactors, such as highly turbulent coolant flow, high temperatures and excessive irradiation doses, can compromise the structural integrity of nuclear fuel bundles. Specifically, the irradiation doses influence the microstructure of the material in terms of segregation and precipitation in addition to swelling. This leads to changes in the mechanical properties of the material and consequently, the dynamic characteristics will be altered. The current study presents a fully-coupled, three-dimensional, numerical, structural model that takes...

Material extrusion is an additive manufacturing (AM) technique that provides an innovative and layer-by-layer fabrication method for components with intricate geometry. Due to the effect of various process parameters and the layerwise nature of material extrusion, the material behavior of parts made by this method is not isotropic. Considering the anisotropic material behavior of parts made by material extrusion, developing a finite element (FE) model to predict their mechanical properties is the focus of this study. Experiments including tensile tests, digital image correlation (DIC), and torsion tests were conducted to acquire the material constants for building an accurate FE model. Tensile behavior of specimens printed flat with different raster angles was investigated through a tensile test and modeled by FE software, Abaqus...

Additive manufacturing (AM) is experiencing widespread adoption in many sectors including aerospace and biomedical. Several research works have already studied AM to ensure high quality final parts can be consistently achieved. To aid in virtually simulating the additive manufacturing processes, companies like ANSYS have developed simulation packages for their finite element software. These packages have been proven to be effective in predicting and minimizing distortion and warping, but their capability in predicting resultant mechanical characteristics requires further investigation. This paper...

Characteristics and behaviors of materials during manufacturing processes highly depend on their mechanical properties and microstructures. However, these characteristics and behaviors can be greatly influenced by other factors such as strain, strain rate, and temperature during the process. The Johnson-Cook (J-C) constitutive material model has been extensively used to describe the material behavior under such circumstances. The J-C parameters are usually determined using the Split Hopkinson Pressure Bar (SHPB) test which is time consuming and costly...

Application of additively manufacturing (AM) metals is growing rapidly; however, post-process finish machining is still required to improve dimensional accuracy and surface quality. Determining the high-strain high-temperature behavior of AM metals is critical in simulating finish machining, designing appropriate cutting tools, and predicting surface integrity. This paper investigated the machining characteristics of AM Ti-6Al-4V produced using powder bed fusion. High-strain high-temperature behavior of AM Ti-6Al-4V was determined numerically and used in simulating the process...

Determining the mechanical characteristics of additively manufactured materials has been an active topic of research in recent years. Many studies have been performed analyzing the impact of different 3D print parameters on the tensile properties of the printed material. However, compared to typical metals and polymers, there is no widely adopted standard for testing additively manufactured polymers. Consequently, the test results reported by the researchers in this field exhibit high amounts of variability between studies...

The goal of active ankle-foot orthoses (AAFO) is to assist the user in recreating a nominal gait motion. Previously proposed control systems for AAFOs have been reactive, with controllers based on the current tracking error. However, the optimal AAFO controller must ensure adequate trajectory tracking while minimizing the amount of assistance provided to the user. To this end, a model predictive controller (MPC) can be considered to determine the optimal control sequence for a given trajectory...

This work investigated the impact of cutting tools varying edge radii by presenting a 3-dimensional finite element analysis (3D FEA) model during the milling of hardened steels. The proposed numerical model was able to capture the effect of micro geometrical changes between cutting tools of five different edge radii (25 μm, 30 μm, 35 μm, 40 μm, and 45 μm). Experimental milling tests were performed to validate the numerical model and close agreement was reported between the experimentally acquired cutting forces and the numerically simulated ones...

Proper design of micro-textured cutting tools is an effective strategy to improve the machining performance by reducing the tool-chip contact length and the resultant friction and thus improving tool life and workpiece surface integrity. In this paper, an Oxely-based analytical model is developed to optimize micro-textured cutting tool design(s) which eliminate the occurrence of derivative cutting. The model accommodates any workpiece material, tool geometry, and machining parameter...

This letter outlines the modelling, design, and experimental validation of a novel power-efficient actuator for an active ankle-foot orthosis (AAFO). The actuator is based on a new principle of discrete non-linear stiffness. Two or more linear springs are discretely compressed at specified displacement intervals to reduce the peak mechanical power required to actuate the AAFO. The actuator uses a crank-rocker configuration...

Manufacturing industries are constantly pressured by market demands to produce low-cost, high-quality products. Market demands tend to be complex and full of variations, especially in fast-paced industrial settings. To cope with the rising market demands, traditional manufacturing techniques are forced to develop and adapt advanced practices and methods. However, as advances in manufacturing technology grow, so does the need to implement them in an efficient and cost-effective manner...

One of the effective strategies to improve dry machining processes is the implementation of micro-textured cutting tools. Micro-textures decrease the chip-tool contact length and thus reduce friction and heat which lead to better surface quality and longer tool life. However, micro-cutting of the bottom side of the chip, known as derivative cutting, is an issue when using textured tools. Derivative cutting increases the cutting forces, heat, and ultimately tool wear...

Manufacturing processes are typically divided into three categories: formative, subtractive, and additive. While formative and subtractive manufacturing processes are considered more traditional, additive manufacturing (AM) is a family of evolving technologies that are rapidly growing with techniques and constraints yet to be explored. In this paper, a life cycle assessment comparison of casting (formative), machining (subtractive), and three AM methods, namely, binder jetting (BJ), powder bed fusion (PBF), and novel bound powder extrusion (BPE) has been performed...