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The purpose of this paper is to develop a physics‐based model that can predict how a main build material of water interacts with a water‐soluble sacrificial support material in the rapid freeze prototyping (RFP) process.

RFP uses water freezing into ice in a layer‐by‐layer manner as a main build material to create ice structures with complex geometries in a sufficiently cool environment. A eutectic dextrose‐water solution is used as a sacrificial support material. The supported areas in an ice structure are removed by placing the fabricated structure in an environment of appropriate temperature.

Two methods of concentration modeling have been developed to predict the interaction between the main and support materials around their interface region. The two models are described in detail and their predictions are compared to experimentally measured data. The experimental height data compared to the simulation result based on the concentration models agrees to within 6 percent for various build ambient temperatures. As ambient temperatures decreased, diffusion between the two materials also decreased.

The results obtained from this paper can be used as an aid in building complex ice parts in the RFP process so that minimal interaction between the main and support materials can be attained. An understanding of the interaction occurring during fabrication is provided with the concentration models. The method used to develop the concentration models can be applied to other layered manufacturing processes when using two miscible materials.

The aim of this study is to make a contribution towards reducing the deflections of silicon wafers. The deformation of silicon wafers used in the manufacture of electronic micro-components is one of the most common problems encountered by industrialists during manufacturing. Stack warping is typically produced during the process of depositing thin layers on a substrate. This is due to the thermal-mechanical stresses caused by the difference between the thermal expansion coefficients of the materials. Reducing wafer deformation is essential to increase reliability and improve quality. In this paper, the authors propose an approach based on minimal geometrical modifications to reduce the deformation of a silicon wafer coated with two thin layers. Numerical finite element models have been developed to evaluate the impact of geometrical modifications on warping amplitude. Finite element models have been validated compared with experimental models. The results obtained are encouraging and clearly show a considerable reduction in wafer deformation.

Reducing wafer deformation is essential to increase reliability and improve quality. In this paper, the authors propose an approach based on minimal geometrical modifications to reduce the deformation of a silicon wafer coated with two thin layers. Numerical finite element models have been developed to evaluate the impact of geometrical modifications on warping amplitude. Finite element models have been validated compared with experimental models.

The results obtained are encouraging and clearly show a considerable reduction in wafer deformation.

This paper describes the influence of geometric modification on wafer deformation. The work show also the cruciality of stress reduction in the purpose to obtain less wafer deformation.

Internal channels produced by selective laser melting (SLM) have rough surfaces that require post-processing. The purpose of this paper is to develop an empirical model for predicting the material removal and surface roughness (SR) of SLM-manufactured channels owing to abrasive flow machining (AFM).

A rheological model was developed to simulate the viscosity and power-law index of an AFM medium. To simulate the pressure distribution and velocity in the SLM channels, the fluid behavior and SR in the channels were simulated by using computational fluid dynamics. The results of this simulation were then applied to create an empirical model that can be used to predict the SR and material removal thickness. To verify this empirical model, it was applied to an actual part fabricated by SLM. The results were compared with the measurements of the SR and channel diameter subsequent to AFM.

The proposed model exhibits maximum deviation between the model and the measurement of −1.1% for the down-skin SR, −0.2% for the up-skin SR and −0.1% for material removal thickness.

The results of this study show that the proposed model can avoid expensive iterative tests to determine whether a given channel design leads to the desired SR after smoothing by AFM. Therefore, this model helps to design an AFM-ready channel geometry.

In this paper, a quantitatively validated AFM model was proposed for complex SLM channels with varying orientation angles.

Presents a simple heuristic optimization algorithm to determine weight‐minimal laminate structures. The algorithm is based on an inverted form of growth strategy, where material is removed in areas with low stresses. In the presented algorithm the removal of material is performed in a layerwise manner in areas with low stress or in areas where the layer orientation angle differs significantly from the principal stress direction. In order to get a production‐adapted structure, the layer orientation angles of the available individual plies are not modified and the material is removed only locally in the respective plies. Contrary to a more formal mathematical optimization no sensitivity analyses are needed by the procedure outlined so far and this keeps the corresponding numerical effort reasonably low. The structural analyses have been performed by the Finite Element Program ANSYS and the outlined heuristic algorithm has been implemented by ANSYS‐macros. Several examples of rectangular laminate plates show the effectiveness of the present algorithm.

Demonstrates the simple but effective application of a standard finite element program (PAFEC), and the associated geometric modelling code (PIGS), to the improvement of the design of an engineering component. The technique adopted involves augmenting material around zones of high stress and removing material in zones of low stress. This evolutionary procedure is related to the behaviour of bones in animals. The essentially two‐step procedure involves; finite element analysis of the preliminary component design using PAFEC; and, definition of a new geometry using PIGS, with selected stress contours giving an indication of the new shape. The technique, which proceeds iteratively, was first tested successfully on some classical academic optimisation problems. Its subsequent application to the industrial problem of a twin chamber pressurised extruded aluminium section, the primary component of an air drying system, resulted in material savings of up to 50 per cent and an associated drop in the maximum von Mises stress of 45 per cent. While this method does not determine the optimal structural form, it does generate substantial improvements in terms of material usage and reduced maximum stresses. It has the advantage that it can be used by any competent engineer with a working knowledge of the strength of materials, finite elements and structural form.

This study deals with adapting various repair technologies to the requirements of conformally coated printed circuit boards. Information was gathered from both military and industry sources in an effort to find best method examples, the culmination of which is reported in this paper. Repairability of conformally coated printed circuit boards is a prime concern of the electronics industry and is rapidly becoming a technology in its own right.

This chapter is about online hate speech propagated via platforms operated by social media companies (SMCs). It examines the options open to states in forcing SMCs to take responsibility for the hateful content that appears on their sites. It examines the technological and legal context for imposing legal obligations on SMCs, and analyses initiatives in Germany, the United Kingdom, the European Union and elsewhere. It argues that while SMCs can play a role in controlling online hate speech, there are limitations to what they can achieve.

Extends the evolutionary structural optimization method to the solution for the natural frequency optimization of a two‐dimensional structure with additional non‐structural lumped masses. Owing to the significant difference between a static optimization problem and a structural natural frequency optimization problem, five basic criteria for the evolutionary natural frequency optimization have been established. The inclusion of these criteria into the evolutionary structural optimization method makes it possible to solve structural natural frequency optimization problems for two‐dimensional structures with additional non‐structural lumped masses. Gives two examples to demonstrate the feasibility of the extended evolutionary structural optimization method when it is used to solve structural natural frequency optimization problems.

Excimer lasers are finding increasing use in the electronics manufacturing industry. In contrast to other types of laser processing in which material is removed by localised heating, excimer laser processing involves a non‐thermal ablative material removal mechanism. This is due to the ultra‐violet output and short pulse duration of these unique light sources. The result is a high precision means of patterning thin dielectric films, removing such films from metal substrates, or removing thin metal films from underlying dielectrics. Through proper selection of operating parameters it is possible to achieve smooth sidewall profiles with selectable amount of taper while leaving the surrounding and, in the case of film removal, the underlying material virtually untouched. This paper will review the growing use of excimer lasers in applications such as the skiving of access holes and windows in flexible wiring, the drilling of via holes for multilayer boards, the stripping of microwires and other chip bonding applications. The differences between excimer laser processing and conventional laser based techniques will be highlighted.

The purpose of this paper is to present a constraint and corresponding algorithm enhancing the evolutionary structural optimization (ESO) method, aiming to circumvent its structure break down problem in some special cases, such as the tie-beam problem.

A virtual soft material introduced to an element will change the stiffness of the element and may consequently change the stress distribution of that element and its neighbors. With this property, the virtual stiffness of the selected element is calculated and the threshold of the stress changes is derived. The stress threshold is used to evaluate the role of an element on the load path and therefore decide the contribution of the element to the structure. Adding this checking operation into the original ESO iterations enables validation of element removal.

The reason for structure break down with the ESO method is that the element removal criterion of ESO only works for certain optimal objectives. It cannot guarantee that the structure does not fail. The proposed operation offers a stronger and stricter constraint condition for ESO’s element removal process, preventing the structure from breaking down in some special cases.

The tests on several examples reported in the literature show that the proposed method has the same ability to achieve an optimum solution as the original ESO methods do, while avoiding incorrect deletion of structurally important elements. The benchmark tie-beam problem is solved successfully with this algorithm. The method can be used in other situations as well.