Closed fractures of distal radius and ulna are one of the most common skeletal injuries, occurring at all ages. Temporary arm immobilization through cast is part of the standard treatments. However, ...traditional casting procedures are time consuming, operator's skill dependent and do not always guarantee a satisfactory outcome. From a clinical perspective, casts are often considered uncomfortable and can be associated to skin lesions. To overcome these limitations, the recent growth of 3D technologies has enabled new standardized casting procedures: additive manufacturing (AM) is a technique that creates highly customized cast models from anatomical 3D data by using digitally controlled and operated material laying tools. Compared with conventional casts, those produced with AM technique could potentially reduce skin complications and satisfy both mechanical and clinical requirements of functionality, comfort, and aesthetics.
The objective of this study is to describe the new practical methodology to produce a 3D printable cast for upper arm immobilization. The parametric modelling tool, employed to develop a semi-automatic design system for generating the printable cast model, reduces the complex process of orthosis design to a few minutes and all the manufacturing operations remain unaffected by CAD skills of the operator. Specific hardware and software tools (3D scanner, modelling software and FDM technology) were chosen to mitigate design and production costs while guaranteeing suitable levels of data accuracy, process efficiency and design versatility. To highlight the effectiveness of the proposed solution, a finite element analysis simulation was performed on models with different geometry, highlighting the mechanical strength of generated structures.
The final result is a personalized 3D printed cast with a highly ventilated structure that is lightweight but still maintains a high level of strength and provides hygienic benefits, reducing the risk of cutaneous complications, potentially improving treatment efficacy and increasing patient satisfaction.
In order to improve the structural performance of the aero-engine gearbox housing and reduce the adverse effects of the engine bad working conditions on the supporting components， the topology ...optimization theory based on variable density method is adopted， and the minimum flexibility index and weighted average transverse eigenvalue are taken as the target number， and the coupling of thermal-elastohydrodynamic-lubrication effects of the supporting components are considered. Taking the maximum deformation less than 0.15 mm and the equivalent stress less than the material stress as the constraint conditions， the topology optimization design of the aero-engine gearbox housing is carried out. According to the topology optimization results， the geometric reconstruction of the housing structure is carried out， and the strength， stiffness and mass of the shell structure before and after optimization are compared and analyzed. The results show that， after optimization， the housing mass is reduced from 5.53 kg to 5.10
•Optimization of additive manufacturing product with numerical simulation.•Topological optimization dedicated to additive manufacturing.•Knowledge based management of additive manufacturing for ...numerical integration.•Weight saving by coupling topological optimization and additive manufacturing.
Rapid prototyping (RP) and more generally Additive Manufacturing (AM) enable the manufacture of complex geometries, which are very difficult to build with classical production. There are numerous technologies that are using different kind of material. For each of these, there are at least two materials: the production material and the support one. Support material is, in most cases, cleaned and becomes a manufacturing residue. Improve the material volume and the global mass of the product is an essential aim surrounding the integration of simulation in additive manufacturing process. Moreover the layer-by-layer technology of additive manufacturing allows the design of innovative objects and the use of topological optimization in this context can create a very interesting combination. The purpose of our paper is to present a methodology and a tool, which allow the use of topological optimization for the preparation of model for RP and AM.
This paper presents an end-to-end design process for compliance minimization-based topological optimization of cellular structures through to the realization of a final printed product. ...Homogenization is used to derive properties representative of these structures through direct numerical simulation of unit cell models. The resulting homogenized properties are then used assuming uniform distribution of the cellular structure to compute the macroscale structure. Results are presented that illustrate the fine-scale stresses developed in the macroscale optimized part as well as the effect that fine-scale structure has on the optimized topology. Finally, a new method is presented for generating an STL representation of the optimized part that is suitable for printing on typical industrial machines. Quite fine cellular structures are shown to be possible using this method.
•We designed the human-made corals by minimizing a carbon-solidification-related objective function and considering the morphological characteristics of corals.•We developed a surface mapping method ...to dent the surface of optimized structures homogeneously.•We prototyped the designs by additive manufacturing with biologically compatible magnesium and prototyped photosensitive material to test their capability to replace natural corals.
This paper presents an optimization method to systematically design human-made corals using the technique of solid isotropic material with the penalization. In optimization, we minimized the squared norm of the carbon gradient and considered the volume constraint and the length constraint. We homogeneously dented optimization results using a surface mapping method to provide shelters for polyps, which widely exist in natural corals like the anthocyanins. A computational fluid dynamics investigation based on the lattice Boltzmann method illustrated that the branches of the optimized configuration could shield polyps from ocean currents and afford sufficient nutrition. Eventually, we prototyped samples by digital light processing printer with an optimum mixture ratio of biologically compatible calcium carbonate and photosensitive material. Examples show the tropism of marine organisms in human-made corals is akin to the natural ones. The proposed method allows designing human-made corals and is crucial for environmental remediation.
A well-known and persisting problem in modern education is academic dishonesty. There are various forms of such dishonesty, like plagiarism, which is often debated in the media, but cheating during ...examination perpetuates, and remains one of the oldest and most impactful forms of altering one's educational outcome and diminishing an institution's reputation. The applied prevention of this phenomenon is the subject of scientific attention, but the existing methods are most of the time insufficient or poorly applied. By analyzing the types of problems that occur during written exams, we have developed and implemented an innovative solution to decrease the amount of unwanted collaboration among students, by using their underlying friendship topology to the students' disadvantage. Consequently, we have introduced an original student placement strategy inspired by the interdisciplinary field of social networks analysis, and compared it to no placement strategy at all, and to the state-of-the-art random method. Our method is based on acquiring the social network of students participating in the exam, and using genetic algorithms to rearrange them in seats, such that there is minimal overlapping between real-world friendships and seated neighbours. The three methods have been applied independently on six different pools of students over the period 2013–2016, resulting in an extensive case study on N=586 students in the Romanian higher education system. Next, we discuss the meaning of the results, as well as the applicability and limitations of our method. The analysis is presented both through empirical measurement of interaction between students during exam, as well as statistically, by introducing a metric for the placement effectiveness ε. Our proposed solution offers average improvements of ×2.8 in terms of breaking up real-world friendships, and a ×3.3 reduction in terms of empirically measured student interaction. On the other hand, we showcase that the easier to implement random placement brings about lower improvements of ×1.7 (statistical) and ×2.3 (empirically measured), over no seating strategy. Considering that many educational systems are unaware how vital the customization of student rearrangement is, we consider this case study to beacon an important institutional problem all around the world.
•Analysis of student seating during exam to understand the impact on cheating.•Observations on 586 students, backed up by acquired Facebook friendship data.•An optimized seating is proposed using network analysis and genetic algorithms.•Randomized placement reduces communication by 1.7–2.3 times.•Our approach reduces cheating chances by 2.8–3.3 times.
This paper discusses the use of topological optimization methods as an intermediate step in the design of metal building frames in the development of the geometry of volume structures, dimensions and ...thicknesses of individual elements and groups of elements. On the basis of open data the analysis of various methods of topological optimization used in different software calculation complexes was carried out, the problems of using topological optimization in the construction industry were described. On the example of the metal frame of the main building of the TPP, the results of the generated frame models were analyzed, the most suitable for reproduction variant was selected, and then, using classical design methods, a calculation model was built on the basis of the obtained variant of the frame. As a result of the analysis of the calculations performed, empirical dependences of the frame mass. The identified problems of such an approach to design were described, possible options for solving the identified problems, as well as possible algorithms for carrying out design activities. The design approaches shown in this paper can be used for practical purposes, as a justification for making appropriate design and organizational decisions.
Aiming at angular stability, a frequency-selective surface (FSS) with stable response to TE and TM polarization at large incidence angles is designed by the gradient-based topology optimization ...approach. According to the adjoint variable method (AVM), the adjoint sensitivity analysis for periodic boundary problems is formulated, and its physical significance is described. The optimization of FSS is a typical multisolution optimization problem, which has a slow convergence speed and is prone to generate morbidity solutions. Therefore, to obtain the desired FSS, an appropriate initial value is selected to avoid the optimization result falling into a morbidity solution and the objective function is improved to make it gradually converge. The optimized FSS is insensitive to polarization and it has stability at oblique incidence angle from 0° to 75°. The measured results are in good agreement with the simulation ones. It is shown that this is an effective design method for the stable response to the variety of incident angles, which can solve the periodic problem of multifrequency, multi-angle, and multimode.
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