Manufacturing Of Metal Parts Research Articles

Evaluation of computational homogenization methods for the prediction of mechanical properties of additively manufactured metal parts

It is well known that the strongly location-dependent microstructures observed in metal parts made using additive manufacturing (AM) processes differ from those found in components produced via traditional manufacturing processes. This is primarily because the microstructures in AM parts strongly depend on spatially-varying cooling rates that are caused by several factors including part geometry and proximity to the build plate. Consequently, it is necessary to take a fresh look into methods used for calculating resulting mechanical properties, as the increased spatial resolution that must be applied to the description of properties of AM parts calls for vast improvements in computational efficiency. Computational homogenization methods are employed for the calculation of these mechanical properties based on the polycrystalline microstructures typically encountered in metallic materials. Such calculations that enable the description of properties as a function of position increase the accuracy of a vital link in the structure–process–property–performance continuum that falls within the Integrated Computational Materials Engineering (ICME) paradigm. In this work we describe and critically review six of these methods and their application to AM microstructures. We find that the Fast Fourier Transform (FFT) method and the Finite Element Method (FEM) are the optimal choices based on several factors including accuracy, efficiency, and applicability to polycrystalline microstructures. Provided the microstructure is amenable to the use of uniform grids and the assumption of periodic boundary conditions, the FFT method has greater computational efficiency. Where unstructured meshes, adaptive remeshing and/or non-periodic boundary conditions are desired, the FEM is the method of choice. Our recommendations are equally applicable to functionally graded AM parts where site-specific microstructures are engineered using multiple materials or different process parameters. They can also be utilized for other material systems and circumstances where increased accuracy is achieved by describing mechanical properties as a function of location.

Fabrication sequence optimization for minimizing distortion in multi-axis additive manufacturing

Additive manufacturing of metal parts involves phase transformations and high temperature gradients which lead to uneven thermal expansion and contraction, and, consequently, distortion of the fabricated components. The distortion has a great influence on the structural performance and dimensional accuracy, e.g., for assembly. It is therefore of critical importance to model, predict and, ultimately, reduce distortion. In this paper, we present a computational framework for fabrication sequence optimization to minimize distortion in multi-axis additive manufacturing (e.g., robotic wire arc additive manufacturing), in which the fabrication sequence is not limited to planar layers only. We encode the fabrication sequence by a continuous pseudo-time field, and optimize it using gradient-based numerical optimization. To demonstrate this framework, we adopt a computationally tractable yet reasonably accurate model to mimic the material shrinkage in metal additive manufacturing and thus to predict the distortion of the fabricated components. Numerical studies show that optimized curved layers can reduce distortion by orders of magnitude as compared to their planar counterparts.

Sequential Solidification of Metal Powder by a Scanning Microwave Applicator.

This study examines the fundamental feasibility of sequential metal-powder solidification by localized microwave-heating (LMH) provided by a scanning, all-solid-state microwave applicator. This continuous process is considered for the additive manufacturing (AM) and 3D printing (3DP) applications of metal parts. In previous studies, we employed LMH for the incremental solidification of small batches of metal powder in a stepwise vertical manner. Here, we study a continuous lateral LMH process, layer by layer, in a fashion similar to laser scanning in powder beds, as performed in common laser-based AM systems. LMH solidification at scanning rates of ~1 mm3/s is obtained in bronze powder using ~0.25-kW microwave power. The effect is studied here by LMH scanning in one lateral dimension (~20-mm long) in layers, each of ~1-4 mm thickness and ~2-4 mm width (mechanically confined). Imperfect solid bars of ~20×4×5 mm3 are obtained with rough surfaces. Their joining in an L shape is also demonstrated. The experimental solidified products are tested, and their hardness and density properties are found to be comparable to laser-based AM products. The capabilities and limitations of the LMH scanning concept for metal-powder solidification are evaluated. The potential feasibility of a solid-state LMH-AM technology is discussed.

An overview of surface roughness enhancement of additively manufactured metal parts: a path towards removing the post-print bottleneck for complex geometries

An overview of surface roughness enhancement of additively manufactured metal parts: a path towards removing the post-print bottleneck for complex geometries

Servitization of SMEs: Focused on the Electrical Equipment and Metal Parts Manufacturers in South Korea

Servitization is becoming an essential strategy for manufacturers to gain competitive advantage, and several successful cases have already been reported. However, these success stories are mainly studied for large enterprises such as GE, IBM, Xerox, and Rolls-Royce. Therefore, it is difficult to apply the cases to the servitization of SMEs, thus in this study, the status of SMEs’ servitization was examined and the applicability was studied. Among those SMEs, manufacturing of electrical equipment and basic metal parts were selected because they are related to all manufacturing industries. As a research method, companies in the relevant industry were randomly selected and CEOs, managers, and employees were interviewed. Through in-depth interviews, the company’s current servitization status in the perception of different employment levels and new servitization opportunities are analyzed. As a result of the interview, the level of servitization in the industry seems to be very low, and it seems that there are very few new servitization opportunities due to the characteristics of general SMEs, such as lack of capital and human resources. Nevertheless, companies were aware that servitization was necessary for sustainability, and they could confirm their will to take on a challenge if there was an opportunity in the future.

The Influence of Atmospheric Oxygen Content on the Mechanical Properties of Selectively Laser Melted AlSi10Mg TPMS-Based Lattice

Selective Laser Melting (SLM) is an emerging Additive Manufacturing (AM) technique for the on-demand fabrication of metal parts. The mechanical properties of Selectively Laser Melted (SLMed) parts are sensitive to oxygen concentration within the SLM build chamber due to the formation of oxides, which may lead to various negative consequences. As such, this work explores the influence of SLM atmospheric Oxygen Content (OC) on the macroscopic mechanical properties of SLMed AlSi10Mg bulk material and Triply Periodic Minimal Surface (TPMS) lattices namely primitive, gyroid, and diamond. Standard quasi-static tensile and crushing tests were conducted to evaluate the bulk properties of AlSi10Mg and the compressive metrics of TPMS-lattices. Two oxygen concentrations of 100 ppm and 1000 were used during the SLM fabrication of the experimental specimens. The tensile test data revealed a small influence of the oxygen content on the bulk properties. The low oxygen concentration improved the elongation while slightly reduced the ultimate tensile strength and yield stress. Similarly, the influence of the oxygen content on the compressive responses of TPMS-lattices was generally limited and primarily depended on their geometrical configuration. This study elucidates the role of SLM atmospheric oxygen content on the macroscopic behaviour of SLMed AlSi10Mg parts.

Fatigue properties of Scalmalloy® processed by laser powder bed fusion in as-built, chemically and conventionally machined surface condition

Additive manufacturing of metallic parts via laser powder bed fusion has is attractive for applications such as aerospace engineering due to the high weight-saving potential, which is based on the ability of the process to produce complex designs. The aluminum alloy Scalmalloy® can increase this potential for lightweight design further with its high strength and high ductility. These advantages already led to a variety of use cases for statically loaded parts. Research on the dynamic mechanical behavior of Scalmalloy® is far less extensive than for other aluminum materials such as AlSi10Mg. There is limited insight into the fatigue behavior and mechanisms of Scalmalloy® in as-built and various surface-finished states. This study aims to understand the fatigue-fracture mechanisms of Scalmalloy® not only in two different as-built surface conditions but also in machined and chemically milled surface states. Fatigue specimens with four different surface modifications were produced, their surface morphology was characterized and correlated to the fatigue performance. Fractographic analysis was conducted to reveal the fracture-inducing defects. Defect-based modeling is shown to describe the influence of defect size on the fatigue behavior and verifies that the fatigue properties are independent of sample size. Kitagawa-Takahashi-diagrams are drawn upon to explain the influence of defect size, and an equivalent initial flaw size (EIFS) was defined and coupled to an El-Haddad-type model to arrive at a unified model predicting the fatigue strength for all four surface conditions despite their differences in defect nature.

Welding-based additive manufacturing processes for fabrication of metallic parts

Additive Manufacturing (AM) is modernizing the manufacturing industry by enabling the layer-by-layer deposition process to manufacture objects in nearly any form with minimum material waste. However, components developed utilizing the AM process have dimensional constraints. To address this issue, AM-produced metal materials can be coupled with various welding processes. This article focuses on the foundations, highlighting the distinguishing features, capabilities, and challenges of welding-based AM processes by categorizing them into two major groups; arc welding-based AM like Cold Metal Transfer (CMT), Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), Plasma Arc Welding (PAW), and high-energy density welding based AM like Laser Beam Welding (LBW) and Electron Beam Welding (EBW). The prior study findings of welding-based AM metal components on mechanical characteristics and microstructural characterization have been addressed. This work will aid researchers, academicians, and professional welders since it gathers vital information on welding-based AM processes. Furthermore, current research in the arena of welding-based AM and its future opportunities has been discussed.

Life Cycle Assessment of Wire Arc Additive Manufacturing Products

The industrial progress over these years has led to fast, goodquality production. Despite this progress, the impacts related to such type of production, whether these are social, economic, or environmental, have not been, at times, studied extensively. The industry realized the importance of a greener approach and as a result, new sustainable technologies, such as additive manufacturing (AM), have emerged. To generalize the environmental benefits of AM over traditional manufacturing, methodologies like Life Cycle Assessment (LCA) are used. The proposed work has the intent of understanding and quantifying the environmental impacts associated with a particular AM technique for the fabrication of metal parts, Wire Arc Additive Manufacturing (WAAM). An LCA is conducted and, considering the same circumstances, the environmental impacts related to the production of 3 different metal parts are analysed. In order to understand the results obtained, Computer Numerical Control (CNC) milling, which is also used for the fabrication of metal parts, is equally considered. In this particular application, when compared to CNC Milling, WAAM proves to have a 12%-47% in the environmental impact, depending upon the geometry considered. The environmental hotspot identified for both processes is the production of the raw material.

Manufacturing technology in pilot production of batches of parts based on photomasks

A new technology has been developed for manufacturing metal parts from thin (up to 1.5 mm) sheet using one-sided and two-sided templates coated with photoresists. The possibilities of a significant increase in the resource of using multilayer photomasks with a new coating with various methods of its application are revealed, restrictions are set for the use of coatings made of photoemulsion and photoresists, depending on the purpose, complexity of the parts obtained, accessibility for the tool when moving to the processing zone.

In-situ proces control strategies for selective laser melting

Selective Laser Melting (SLM) is an additive manufacturing process that has been attracting the attention of researchers and developers in academia and industry over the last two decades. The SLM manufacturing process is capable of producing sophisticated industrial tools and geometrically complex parts in fewer steps (near net-shape), thus saving resources compared to subtractive manufacturing processes. However, the current industry-scale platforms for manufacturing metal parts via SLM do not sufficiently exploit online feedback control strategies. There is still significant potential for advanced process control which can enhance the overall performance of the system, as well as enable sophisticated manufacture, for example via active control of microstructure to enhance part performance in geometrically complex parts. This paper presents a comparison between the performance of three well-known industrial control strategies, to illustrate strengths and weaknesses in addition to addressing the key challenges and identifying some research opportunities in the field.

Residual Stress and Phase Stability of Titanium Alloys Fabricated by Laser and Electron Beam Powder Bed Fusion Techniques

Additively manufactured metal parts often have a high level of residual stress and can exhibit complex crystalline phase properties due to the rapid cooling nature of their fabrication process. X-ray diffraction (XRD) is a non-destructive technique that can characterize both the residual stress and the crystalline phase properties in detail. However, XRD is an ex-situ measurement and provides only the final state of the manufactured parts. In this article, a method that combines the XRD analyses and numerical simulation of the thermal history during the manufacturing process is reviewed with two examples of titanium alloys fabricated by laser and electron beam powder fusion techniques.

INFLUENCE OF CATHODE MATERIAL ON COMBINED CATHODE PROCESSES IN AQUEOUS SOLUTIONS OF IRON(II) SULPHATE

Sulfuric acid is present in many enterprises for metal processing and manufacturing of metal parts. Existing methods of regeneration of spent solutions are not effective, in particular, spent sulfate solutions are neutralized with lye or waste from other industries containing solid carbonates and hydroxides. At the same time, sulfate waste is formed, which requires disposal at special landfills. Electrochemical regeneration of spent solutions of sulfate-acid treatment of steel solves the problem of disposal of such spent sulfate solutions with the inclusion of iron sulfates. The kinetics of combined cathodic processes in aqueous solutions of iron (II) sulfate at a concentration of 0.5 mol.·dm–3 of iron (II) sulfate, depending on the cathode material was studied. The research methodology was as follows: model aqueous solutions with a composition (mol∙dm–3): 0.5 iron (II) sulfate with the addition of 0.5 sulfuric acid and a control solution – 1.0 sulfuric acid were prepared from chemicals of high stage of purification by dissolution in distilled water. The study of the kinetics of combined cathodic processes in model aqueous solutions was carried out by the method of linear voltammetry using the MTech PGP-500 S potentiostat. The auxiliary electrode is platinum. The reference electrode is mercury sulfate. Determination of iron (II) ions in the solution was carried out by the permanganatometric method. Based on the analysis of the obtained current-voltage curves, the effectiveness of the application of electrochemical regeneration of model solutions of iron (II) sulfate with sulfuric acid was established, which makes it possible to cathodically deposit iron in the form of foil or metal powder, and through the course of the anodic process - convert sulfates into sulfuric acid. During this process, oxidation of Fe2+ to Fe3+ takes place at the slightly soluble anode. Therefore, it is proposed to use polymer porous diaphragms to prevent Fe2+ from entering the anode space. Platinum and copper were used as cathode material. The choice of cathode material was based on different electrochemical properties of these metals in relation to the hydrogen reaction. The balance research on the regeneration of the model solution was carried out in a three-chamber electrolyzer. The initial test solution was fed into the middle chamber. The cathodic current density was 0.025 and 0.035 A∙cm–2, the working area of the anode and cathode was 85 cm2. A compact iron deposit was obtained on the cathode with 08X12N10T, which peeled off. The analysis of the cathode deposit showed the presence of 0.065% hydrogen in iron. Output according to the current of iron was 92%. The end of the Tafel section of the course of cathodic reduction of iron with electrochemical control occurs due to Fe2+ concentration limitations and the ohmic resistance of adsorbed hydrogen at the boundary of heterogeneous phases. It is proposed to eliminate these limitations due to electrolyte mixing.

Residual stresses and deformations of laser additive manufactured metal parts: a review

Residual stresses and deformations of laser additive manufactured metal parts: a review

Sequence planning of sheet metal parts manufactured using progressive dies

Progressive dies are widely used for the mass manufacture of sheet metal parts requiring several stamping operations. Sequencing these stamping operations is vital as it influences the design of the die, especially the number of stations required to make the part. This paper presents a method for automatically generating the sequence plan for parts manufactured using progressive dies. This method establishes a scheme that maps sheet metal features into their corresponding stamping operations, including shearing, bending and forming. The mapped operations are initially placed in one of two categories and then the operations in one category are clubbed together using heuristic rules. The essential characteristics of each group are analysed to establish fuzzy relationships between any selected group and the remaining groups. The final membership value vector obtained from the fuzzy set theory is used to sequence these groups. A program developed in C++ based on this method has been tested on representative industrial sheet metal parts. The methodology is validated by comparing the generated sequences, for two case studies, with those used in industry.

Crack detection in metallic components with varying surface characteristics using laser spot scanning thermography

Cracks are the most common cause of failure in the manufacturing of metal parts, hence technologies for detecting them are essential for defect-free production. In this study, a local laser spot excitation combined with robotic scanning is used to identify vertical cracks in titanium. It is feasible to observe anisotropies in the lateral diffusivity by capturing temporal temperature data with an infrared camera utilizing local thermal stimulation. The crack parameter may then be quantified based on the regional transient behavior of temperature distribution. In doing so, we present an advanced technique for distinguishing between contrast created by the surface oxide layer and contrast caused by the vertical crack. In addition, we provide results from a numerical simulation that looked at the notion of local heat excitation for crack parameter quantification. Thermal conduction, radiation, and convection all play a role in the simulation. The experimental and theoretical findings were found to be quite consistent.

Preferential orientation and mechanical properties anisotropy of wire and arc additive manufactured duplex stainless steel

Wire and arc additive manufacturing (WAAMing) is a highly efficient way to fabricate metal parts. In this work, the 2209 duplex stainless steel (DSS) was WAAMed using cold metal transfer (CMT) method. The anisotropy of WAAMed 2209DSS was systematically discussed based on the characterization of microstructure and mechanical properties. The results showed that the prior ferrite had a strong anisotropy. The 〈100〉 crystal direction had a preferential orientation in building direction (BD). The 〈110〉 crystal direction had a preferential orientation in welding direction (WD) and transverse direction (TD). The austenite had a KS relationship on the orientation with ferrite. The tensile samples were machined in three crystal direction of prior ferrite, including <100> in BD, <110> in WD, and 〈111〉. The tensile sample in 〈111〉 showed the largest ultimate tensile strength (UTS). According to the variation of Schmid factors, the ferrite in <111> had the smallest Schmid factor in {110}〈111〉 slipping system. It yielded a larger stress for dislocation movement and contributed to the largest UTS. The tensile sample in <100> achieved the largest elongation as the larger Schmid factor of ferrite in {110}<111 > slipping system and austenite in {111}〈110〉 slipping system. In addition, the centrosymmetry of orientation around the axis of tensile sample in <100> weakened the stress concentration and helped a more uniform elongating.

Effect of print parameters on additive manufacturing of metallic parts: performance and sustainability aspects

In this study, the effects of print parameters on the mechanical properties of additively manufactured metallic parts were investigated using a tensile test. The 17-4 PH stainless steel specimens with two print parameters, including infill density and pattern orientation, were fabricated by additive manufacturing (AM) using the bound metal deposition (BMD) technique. The mechanical properties considered in this study are the Young’s modulus and ultimate tensile strength. The results demonstrate that the pattern orientations do not affect the Young’s modulus of the infill specimen with the triangular pattern. In contrast, the ultimate strength significantly varies depending on the pattern orientations, where the samples with the pattern orientation of zero degrees yield the best ultimate strength. In fact, the mechanical properties of infill specimens increase with their infill density. However, when operating cost and time are considered, an index for estimating performance and sustainability is consequently established. The relationship between the normalized ultimate strength of an infill specimen and the relative density is defined as the weight efficiency. The index for assessing a sustainable product is characterized by the weight efficiency versus sustainable parameter(s). The index can help end users select an appropriate infill density for AM products by considering the operating cost and time. Different cost models, including material-only costs, direct costs, and total costs, can be included in the index model to assess a sustainable product in a particular cost context.

Microstructure and mechanical properties of AlSi10Mg alloy built by laser powder bed fusion/direct energy deposition hybrid laser additive manufacturing

Laser-based metal additive manufacturing technology, which is represented by laser powder bed fusion (LPBF) and direct energy deposition (DED), has been widely used in high-end industries such as aerospace. However, with the rapid development of aerospace equipment, it has become increasingly difficult to meet the requirements of integrated design and manufacturing of metal parts by using LPBF or DED alone. LPBF/DED hybrid laser additive manufacturing technology is expected to greatly improve the overall manufacturing capacity of metal components by combining the advantages of the two technologies. It is expected to break through the limitation of overall manufacturing size, to realize the manufacturing of large and complex aerospace parts, and to reduce the number of components required for large and complex structures to meet the overall design and manufacturing requirements. In this paper, AlSi10Mg was selected as the build material for the LPBF/DED hybrid laser additive manufacturing process and the microstructure and mechanical properties of the as-built samples were studied. The analyses of the microstructure show that there are no obvious defects at the interface between the LPBF zone and the DED zone. Although the phase compositions of both the LPBF zone and the DED zone are composed of alpha-Al matrix and eutectic Si, the melt track shape, microstructural morphology, grain size, grain boundary angle distribution and grain texture change significantly around the LPBF/DED interface. The results of mechanical property tests indicated that the LPBF zone has higher microhardness and tensile strength but lower elongation in comparison with the DED zone. The fine microstructure containing a large number of Si-rich nano-precipitates and high amount of solid solution element enhance the microhardness and tensile strength of the LPBF zone, where the lower solid solubility and high percentage of low angle grain boundary increased the elongation of the DED zone. More importantly, the tensile strength of the LPBF/DED interface is not less than the DED zone, and the boundary of DED melt track as well as porosity defect in the DED zone are the weakest region of LPBF/DED hybrid laser additive manufacturing AlSi10Mg specimens. Therefore, the overall tensile strength of the sample is mainly determined by the DED zone. The formation mechanism of the gradient microstructure around the LPBF/DED interface and the effect of microstructure on properties were also analyzed. This paper proves that the LPBF/DED hybrid laser additive manufacturing technology can be used for the overall manufacturing of aluminum alloy components with regular surface structure.

Review of quality issues and mitigation strategies for metal powder bed fusion

PurposeSelective laser melting and electron beam melting processes are well-known for the additive manufacturing of metal parts. Metal powder bed fusion (MPBF) is a common term for them. The MPBF process can empower the manufacturing of intricate shapes by reducing the use of special tools, shortening the supply chain and allowing small batches. However, the MPBF process suffers from many quality issues. In literature, several works are recorded for qualification of the MPBF part. The purpose of this study is to recollect those works done for quality control and report their helpful findings for further research and development.Design/methodology/approachA systematic literature review was conducted to highlight the major quality issues in the MPBF process and its root causes. Further, the works reported in the literature for mitigation of these issues are classified and discussed in five categories: experimental investigation, finite element method-based numerical models, physics-based analytical models, in-situ control using artificial intelligence (AI) and machine learning (ML) methods and statistical approaches. A comparison is also prepared among these strategies based on their suitability and limitations. Additionally, improvements in MPBF printers are pointed out to enhance the part quality.FindingsAnalytical models require less computational time to simulate the MPBF process and need a smaller number of experiments to confirm the results. They can be used as an efficient process parameter planning tool to print metal parts for noncritical applications. The AI-ML based quality control is also suitable for MPBF processes as it can control many processing parameters that may affect the quality of the MPBF part. Moreover, capabilities of MPBF printers like thinner layer thickness, smaller beam diameter, multiple lasers and high build temperature range can help in quality control.Research limitations/implicationsThis study converts the piecemeal data on MPBF part qualification methods into interesting information and presents it in tabular form under each strategy. This tabular information provides the basis for further quality improvement efforts in the MPBF process.Originality/valueThis study references researchers and practitioners on recent quality control efforts and their significant findings for a better quality of MPBF part.