Omer Cansizoglu, Ola L.A. Harrysson, Harvey A. West, Denis R. Cormier and Tushar Mahale
Optimization techniques can be used to design geometrically complex components with a wide variety of optimization criteria. However, such components have been very difficult and…
Abstract
Purpose
Optimization techniques can be used to design geometrically complex components with a wide variety of optimization criteria. However, such components have been very difficult and costly to produce. Layered fabrication technologies such as electron beam melting (EBM) open up new possibilities though. This paper seeks to investigate the integration of structural optimization and direct metal fabrication process.
Design/methodology/approach
Mesh structures were designed, and optimization problems were defined to improve structural performance. Finite element analysis code in conjunction with nonlinear optimization routines were used in MATLAB. Element data were extracted from an STL‐file, and output structures from the optimization routine were manufactured using an EBM machine. Original and optimized structures were tested and compared.
Findings
There were discrepancies between the performance of the theoretical structures and the physical EBM structures due to the layered fabrication approach. A scaling factor was developed to account for the effect of layering on the material properties.
Practical implications
Structural optimization can be used to improve the performance of a design, and direct fabrication technologies can be used to realise these structures. However, designers must realize that fabricated structures are not identical to idealized CAD structures, hence material properties much be adjusted accordingly.
Originality/value
Integration of structural optimization and direct metal fabrication was reported in the paper. It shows the process from design through manufacturing with integrated analysis.
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Timothy J. Horn, Ola L.A. Harrysson, Harvey A. West II, Jeffrey P. Little and Denis J. Marcellin-Little
The aim of this study is to describe an improved experimental substrate for the mechanical testing of patient-specific implants fabricated using direct metal additive…
Abstract
Purpose
The aim of this study is to describe an improved experimental substrate for the mechanical testing of patient-specific implants fabricated using direct metal additive manufacturing processes. This method reduces variability and sample size requirements and addresses the importance of geometry at the bone/implant interface.
Design/methodology/approach
Short-fiber glass/resin materials for cortical bone and polyurethane foam materials for cancellous bone were evaluated using standard tensile coupons. A method for fabricating bone analogs with patient-specific geometries using rapid tooling is presented. Bone analogs of a canine radius were fabricated and compared to cadaveric specimens in several biomechanical tests as validation.
Findings
The analog materials exhibit a tensile modulus that falls within the range of expected values for cortical and cancellous bone. The tensile properties of the cortical bone analog vary with fiber loading. The canine radius models exhibited similar mechanical properties to the cadaveric specimens with a reduced variability.
Research limitations/implications
Additional replications involving different bone geometries, types of bone and/or implants are required for a full validation. Further, the materials used here are only intended to mimic the mechanical properties of bone on a macro scale within a relatively narrow range. These analog models have not been shown to address the complex microscopic or viscoelastic behavior of bone in the present study.
Originality/value
Scientific data on the formulation and fabrication of bone analogs are absent from the literature. The literature also lacks an experimental platform that matches patient-specific implant/bone geometries at the bone implant interface.
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Ola L.A. Harrysson, Denis R. Cormier, Denis J. Marcellin‐Little and Ketan Jajal
This report describes Rapid Prototyping (RP) ‐aided assessment and preoperative planning for treatment of bilateral multifocal pelvic limb deformities in a 1 year old German…
Abstract
This report describes Rapid Prototyping (RP) ‐aided assessment and preoperative planning for treatment of bilateral multifocal pelvic limb deformities in a 1 year old German Shepherd dog. Computed tomography (CT) scans were acquired on a General Electric CT scanner and converted to solid models using Mimics software from Materialise. Stereolithography patterns were prototyped using QuickCast build style on a SLA ‐190. Room temperature vulcanized silicone molds were constructed and three sets of polyurethane patterns were cast for pre‐surgical planning and rehearsal. The paper compares traditional osteotomy planning procedures using only radiographs and 2D CT images to planning with full‐scale physical biomodels. The biomodels had a clearly beneficial impact on the accuracy of surgery and positively influenced the clinical outcome.
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Li Yang, Ola A Harrysson, Harvey A West II, Denis R. Cormier, Chun Park and Kara Peters
The aim of this study is to perform a comparative study on sandwich structures with several types of three-dimensional (3D) reticulate cellular structural core designs for their…
Abstract
Purpose
The aim of this study is to perform a comparative study on sandwich structures with several types of three-dimensional (3D) reticulate cellular structural core designs for their low-energy impact absorption abilities using powder bed additive manufacturing methods. 3D reticulate cellular structures possess promising potentials in various applications with sandwich structure designs. One of the properties critical to the sandwich structures in applications, such as aerospace and automobile components, is the low-energy impact performance.
Design/methodology/approach
Sandwich samples of various designs, including re-entrant auxetic, rhombic, hexagonal and octahedral, were designed and fabricated via selective laser sintering (SLS) process using nylon 12 as material. Low-energy drop weight test was performed to evaluate the energy absorption of various designs. Tensile coupons were also produced using the same process to provide baseline material properties. The manufacturing issues such as geometrical accuracy and anisotropy effect as well as their effects on the performance of the structures were discussed.
Findings
In general, 3D reticulate cellular structures made by SLS process exhibit significantly different characteristics under low-energy drop weight impact compared to the regular extruded honeycomb sandwich panels. A hexagonal sandwich panel exhibits the largest compliance with the smallest energy absorption ability, and an octahedral sandwich panel exhibits high stiffness as well as good impact protection ability. Through a proper geometrical design, the re-entrant auxetic sandwich panels could achieve a combination of high energy absorption and low response force, making it especially attractive for low-impact protection applications.
Originality/value
There has been little work on the comparative study of the energy absorption of various 3D reticulate cellular structures to date. This work demonstrates the potential of 3D reticulate cellular structures as sandwich cores for different purposes. This work also demonstrates the possibility of controlling the performance of this type of sandwich structures via geometrical and process design of the cellular cores with powder bed additive manufacturing systems.
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Jessica Lichy, Jillian Dawes Farquhar and Maher Kachour
The purpose of this paper is to extend understanding of marketing in MENA by investigating how women entrepreneurs use social networking sites (SNS) in marketing their businesses…
Abstract
Purpose
The purpose of this paper is to extend understanding of marketing in MENA by investigating how women entrepreneurs use social networking sites (SNS) in marketing their businesses in Lebanon.
Design/methodology/approach
To address contextual issues arising from research in this region, this study consists of a two-phase research design of, first, a panel of specialised business commentators and, second, digital qualitative data collection that enabled access to hard to reach informants.
Findings
The study reveals that the activities of women entrepreneurs are fundamentally enabled by SNS as it allows them to optimise their networks in prospecting, communicating and developing relationships with stakeholders. It also allows them to support the social fabric of the family unit by providing an extra source of income and facilitating connections.
Research limitations/implications
This study draws on a single country within the MENA region; nonetheless, the analysis offers new and nuanced understanding to marketing of small businesses in uncovering how Lebanese women entrepreneurs are able to build and run their businesses using SNS.
Practical implications
This research demonstrates how women entrepreneurs can set up and run businesses using SNS to reach and extend their networks in a culturally diverse and growing economy. SNS provides an inclusive platform through which women build and run a small business.
Social implications
This research responds to a World Development aim of studying the relationships between gender and trade such as women entrepreneurs using social technologies.
Originality/value
This research responds to a World Development aim of studying the relationships between gender and trade, here by investigating how women entrepreneurs set up and run small businesses enabled by SNS.
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Niechen Chen, Prashant Barnawal and Matthew Charles Frank
The purpose of this paper is to present a new method for automated post machining process planning for a hybrid manufacturing process. The manufacturing process is expected to…
Abstract
Purpose
The purpose of this paper is to present a new method for automated post machining process planning for a hybrid manufacturing process. The manufacturing process is expected to generate complex functional parts by taking advantage of free form surface creation from additive manufacturing and high-quality surface finishing from CNC milling.
Design/methodology/approach
The hybrid process starts with additive manufacturing to generate a near net shape part with pre-defined machining allowances on surfaces requiring high quality surface or tight tolerances, along with integrated fixture geometry. The next step is to conduct automated machining process planning to determine critical parameters such as setup angle, tool selection, depth, tool containment, and consequently, the NC code to machine the part.
Findings
This method is shown to be a feasible solution for rapidly creating functional parts. The tests have been conducted to validate the method developed in this paper.
Originality/value
This paper introduces a new automated post machining process planning method for integrating additive manufacturing with a rapid milling process.
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Dana H. Abdeen and Bruce R. Palmer
This paper aims to study the effect of processing parameters of an electron beam melting (EBM) machine on the surface roughness, critical pitting temperature and density of…
Abstract
Purpose
This paper aims to study the effect of processing parameters of an electron beam melting (EBM) machine on the surface roughness, critical pitting temperature and density of Ti-6Al-4V parts produced from the EBM machine.
Design/methodology/approach
In this study, statistically designed experiments were used to manufacture Ti-6Al-4V samples in the EBM machine under different process parameters of beam current, beam speed and offset focus. Surface roughness was measured for as-built samples using a 3D profilometer. Then, a potentiostatic test was conducted under 2.40 V vs saturated calomel electrode to determine the critical pitting temperature (CPT) in 3.5 per cent mass NaCl solution for the samples of different processing parameters. Next, density was measured for these samples. Finally, model equations were established to relate EBM’s process parameters to measured properties of surface roughness, CPT and density.
Findings
Results showed that offset focus had the main influence on surface roughness more than the beam current and the beam speed. Changing processing parameters did not affect corrosion behavior of EBM Ti-6Al-4V as CPT did not vary widely, although a slight effect on CPT values obtained from the beam current and the beam speed. Density was greatly affected by the offset focus more than the other parameters. It can be concluded that uniform and precise measurements of roughness and density are not achievable through this machine; only a range of these properties can be attained.
Originality/value
EBM machine produces 3D parts in a layer-based building process under high temperature and vacuum atmosphere. Due to the manufacturing technique and conditions, the resulting object has irregularities on the exterior surface and voids that are formed within the part, both of which affect samples’ properties like surface roughness, CPT and density. This study established model equations that can relate parts’ properties to processing parameters so that parts of specific properties are obtained to fit the application they are used for. For each property, ANOVA fits vs linear energy were also obtained.
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Dana H. Abdeen and Bruce R. Palmer
This paper aims to evaluate the corrosion behavior of Ti-6Al-4V parts produced with electron beam melting (EBM) machine and compare it with wrought Ti-6Al-4V alloy.
Abstract
Purpose
This paper aims to evaluate the corrosion behavior of Ti-6Al-4V parts produced with electron beam melting (EBM) machine and compare it with wrought Ti-6Al-4V alloy.
Design/methodology/approach
Potentiodynamic and potentiostatic tests were applied on EBM Ti-6Al-4V in 3.5 per cent mass NaCl solution to determine the pitting potential and critical pitting temperature (CPT). A relation between pitting potential and temperature was established for EBM Ti-6Al-4V alloy by conducting potentiodynamic testing under different temperatures. CPT was also measured for EBM Ti-6Al-4V alloy in 3.5 per cent mass NaCl solution at a standard potential of 800 mV vs saturated calomel electrode (SCE). The same tests were performed on wrought Ti-6Al-4V for comparison purposes. Moreover, CPT for EBM Ti-6Al-4V alloy was measured in 3.5 per cent mass NaCl solution of different pH of 2.0, 5.7 and 10.0 to examine the effect of aggressive conditions on the pitting corrosion of EBM alloy.
Findings
Potentiodynamic test resulted in a relatively high pitting potential of EBM alloy, which was close to the pitting potential of wrought alloy even at higher temperatures. In addition, EBM samples did not pit when potentiostatic test was performed at 800 mV vs SCE, even at high and low values of pH.
Originality/value
EBM Ti-6Al-4V alloy has been increasingly playing an important role in aerospace, automobile and industrial fields. The technique and conditions of manufacturing form voids and increase roughness of the exterior surface of EBM objects, which might increase the tendency to initiate pitting corrosion within its holes and surface folds. This article shows that, despite surface variations and porosity in EBM Ti-6Al-4V alloy, the material maintained its corrosion resistance. It was found that the corrosion behavior of EBM alloy was close to that of the conventionally made wrought Ti-6Al-4V alloy.