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The present study investigates the mechanical properties of three types of Ti6Al4V ELI bone screws realized using the laser powder bed fusion (LPBF) process: a fully threaded screw and two groups containing differently arranged sectors made of lattice-based Voronoi (LBV) structure in a longitudinal and transversal position, respectively. This study aims to explore the potentialities related to the introduction of LBV structure and assess its impact on the implant’s primary stability and mechanical performance.

The optimized bone screw designs were realized using the LPBF process. The quality and integrity of the specimens were assessed by scanning electron microscopy and micro-computed tomography. Primary stability was experimentally verified by the insertion and removal of the screws in standard polyurethane foam blocks. Finally, torsional tests were carried out to compare and assess the mechanical strength of the different designs.

The introduction of the LBV structure decreases the elastic modulus of the implant. Longitudinal LBV type screws demonstrated the lowest insertion torque (associated with lower bone damage) while still displaying promising torsional strength and removal force compared with full-thread screws. The use of LBV structure can promote improved functional performances with respect to the reference thread, enabling the use of lattice structures in the biomedical sector.

The paper fulfils an identified interest in designing customized implants with improved primary stability and promising features for secondary stability.

A new design of screw head, the Uni‐screw, has been developed to rival the well‐established slotted, Phillips and Pozidriv screws. It is based on a series of hexagonal recesses that avoids “cam‐out”, which occurs with the other designs when higher torques are applied. Other benefits include the need for only one driver over a wide range of screw sizes and easy alignment of driver to screw. Other recess forms can be used including pentagon and heptagon to provide high tamper resistance, and these can be tailored for a single user to give total security. The Uni‐screw is being manufactured and distributed by Forward Engineering under a licence from Uni‐screw and the first commercial products are aimed at the building and DIY markets. Strong interest has also been shown by several industrial organisations.

With the twin screw extruder being widely used, there are a lot of parameters considered in the method, and the extruder’s volume is an important parameter of twin screw extruders among them. In this paper, some of the extruder parameters such as the impacting extruder volume are introduced, and the mathematical relationship in these parameters is interpreted. The minimum power consumption is the goal of the authors’ structural design.

This paper further applies genetic algorithm, a kind of intelligent optimization methods, to obtain the most optimized design dimension, and power consumption function related to unit output of extruder is used as the optimizing target. Meanwhile, this paper takes channel depth of feeding section, channel depth of extrusion section affecting the energy consumption, the width of flight top and helix angle as design variables.

By using genetic algorithm, the optimal structure size is obtained, and the power consumption is minimum.

With the use of optimizing the structure, the power of consumption is reduced. This method has important economic significance and important social significance on energy saving.

The complications caused by metallic orthopaedic bone screws like stress-shielding effect, screw loosening, screw migration, higher density difference, painful reoperation and revision surgery for screw extraction can be overcome with the bioabsorbable bone screws. This study aims to use additive manufacturing (AM) technology to fabricate orthopaedic biodegradable cortical screws to reduce the bone-screw-related-complications.

The fused filament fabrication technology (FFFT)-based AM technique is used to fabricate orthopaedic cortical screws. The influence of various process parameters like infill pattern, infill percentage, layer height, wall thickness and different biological solutions were observed on the compressive strength and degradation behaviour of cortical screws.

The porous lattice structures in cortical screws using the rapid prototyping technique were found to be better as porous screws can enhance bone growth and accelerate the osseointegration process with sufficient mechanical strength. The compressive strength and degradation rate of the screw is highly dependent on process parameters used during the fabrication of the screw. The compressive strength of screw is inversely proportional to the degradation rate of the cortical screw.

The present study is focused on cortical screws. Further different orthopaedic screws can be modified with the use of different rapid prototyping techniques.

The use of rapid prototyping techniques for patient-specific bone screw designs is scantly reported. This study uses FFFT-based AM technique to fabricate various infill patterns and porosity of cortical screws to enhance the design of orthopaedic cortical screws.

This paper aims to investigate the temperature and wear properties of vertical ball screws and to discuss the surface design of ball screws in industrial applications.

The energy equation of the screw surface considering the frictional heat was established to verify the surface temperature of the ball screw. X-ray diffraction was used to examine the micro-contact temperature between the ball and screw. Debris size and density were examined to investigate wear properties of ball screws and to study the relationship of wear debris and temperature.

First, the main energy source for the surface temperature of high speed vertical ball screws is derived from friction force between ball and screw. Second, the temperature rise between the ball and screw has great relevance with wear debris concentration. Third, the surface temperature of the screw is higher than between the nut and ball for high speed vertical ball screws due to high convection heat transfer. The contact temperature of the nut near the flange is smaller than that of the nut away from the flange end due to the high contact load and thermal conduction. Finally, correlation of particle size and surface roughness value for vertical ball screws was established, and its effects on contact temperature were studied. The theoretical analysis and experiments will help to characterize the design and manufacture of vertical ball screws.

The surface temperature and micro-contact temperature analytical model were established to study the ball screw design. Based on the surface-particle micro-contact temperature balance, the optimal range of surface roughness was designed for vertical ball screws, considering the wear debris and micro-contact temperature.

A PROPOSAL to replace the 7‐ft. No. 1 wind tunnel at the N.P.L. by two new tunnels of the open jet type, housed in the old tunnel building, was put forward in 1930, and one of the new tunnels has now been completed and tested. The present report deals mainly with preliminary experiments on models, which were carried out to ensure that the projected tunnels should give the best possible aerodynamic performance.

Simulations exist for the prediction of the behaviour of building structural systems under fire, including two-way coupled fire-structure interaction. However, these simulations do not include detailed models of the connections, whereas these connections may impact the overall behaviour of the structure. Therefore, this paper proposes a two-scale method to include screw connections.

The two-scale method consists of (a) a global-scale model that models the overall structural system and (b) a small-scale model to describe a screw connection. Components in the global-scale model are connected by a spring element instead of a modelled screw, and the stiffness of this spring element is predicted by the small-scale model, updated at each load step. For computational efficiency, the small-scale model uses a proprietary technique to model the behaviour of the threads, verified by simulations that model the complete thread geometry, and validated by existing pull-out experiments. For four screw failure modes, load-deformation behaviour and failure predictions of the two-scale method are verified by a detailed system model. Additionally, the two-scale method is validated for a combined load case by existing experiments, and demonstrated for different temperatures. Finally, the two-scale method is illustrated as part of a two-way coupled fire-structure simulation.

It was shown that proprietary ”threaded connection interaction” can predict thread relevant failure modes, i.e. thread failure, shank tension failure, and pull-out. For bearing, shear, tension, and pull-out failure, load-deformation behaviour and failure predictions of the two-scale method correspond with the detailed system model and Eurocode predictions. Related to combined load cases, for a variety of experiments a good correlation has been found between experimental and simulation results, however, pull-out simulations were shown to be inconsistent.

More research is needed before the two-scale method can be used under all conditions. This relates to the failure criteria for pull-out, combined load cases, and temperature loads.

The two-scale method bridges the existing very detailed small-scale screw models with present global-scale structural models, that in the best case only use springs. It shows to be insightful, for it contains a functional separation of scales, revealing their relationships, and it is computationally efficient as it allows for distributed computing. Furthermore, local small-scale non-convergence (e.g. a screw failing) can be handled without convergence problems in the global-scale structural model.

This paper aims to develop an integrated and portable desktop 3D printer using direct extruding technology to expand applied material field. Different from conventional fused deposition modeling (FDM) which uses polymer filaments as feedstock, the developed system can fabricate products directly using polymer pellets. And its printing properties are also investigated.

A conical screw-based extrusion deposition (CSBED) system was developed with a large taper conical screw to plasticize and extrude fed materials. The 3D printer was developed with assistance of precision positioning and controlling system. Biocompatible thermoplastic polyurethane (TPU) pellets were selected as raw materials for experiments. The influences of four processing parameters: nozzle temperature, fill vector orientation, layer thickness and infill density on the product’s internal structure and tensile properties were investigated.

It is concluded that the customized system has a high manufacturing accuracy with a diminutive global size and is suitable for printing soft materials such as TPU. Theoretical calculation shows the developed conical screw is more effective in plasticizing and extruding compared with conventional screw. Printed samples can achieve applicable tensile properties under harmonious parameter cooperation. Deposited materials are found to have voids among adjacent roads under unbefitting parameters.

The developed system efficiently improves material limitations compared to commercial FDM systems and exhibits great potential in medical field because soft materials such as biocompatible TPU pellets can be directly used.

The aim of this study is to develop a die forging process for producing aircraft components made of magnesium alloy AZ61A using a screw press.

The proposed forging technique has been developed based on the results of a numerical and experimental research. The required forging temperature has been determined by upsetting cylindrical specimens on a screw press to examine both plasticity of the alloy and the quality of its microstructure. The next stage involved performing numerical simulations of the designed forging processes for producing forgings of a door handle and a bracket, both made of magnesium alloy AZ61A. The finite element method based on simulation programme, Deform 3D has been used for numerical modelling. The numerical results revealed that the forgings are free from material overheating and shape defects. In addition to this, the results have also helped determine the regions that are the most prone to cracking. The final stage of the research involved performing forging tests on a screw press under industrial conditions. The forgings of door handles and brackets were made, and then these were tested for their mechanical and structural properties. The results served as a basis for assessing both the viability of the designed technique and the quality of the produced parts.

The experimental results demonstrate that aircraft components made of magnesium alloy AZ61A can be produced by die forging on screw presses. The results have been used to determine the fundamental parameters of the process such as the optimum forging temperature, the method of tool heating, the way of cooling parts after the forging process, and the method of thermal treatment. The results of the mechanical and structural tests confirm that the products meet the required quality standards.

The developed forging technique for alloy AZ61A has been implemented by the forging plant ZOP Co. Ltd in Swidnik (Poland), which specializes in the manufacturing of aircraft components made of non-ferrous metal alloys.

Currently, the global tendency is to forge magnesium alloys (including alloy AZ61A) on free hydraulic presses using expensive die-heating systems. For this reason, the production efficiency of such forging processes is low, while the manufacturing costs are high. The proposed forging technique for alloy AZ61A is an innovative method for producing forgings using relatively fast and efficient machines (screw presses). The proposed forging method can be implemented by forging plants equipped with standard stocks of tools, which increases the range of potential manufacturers of magnesium alloy products. In addition, this technology is highly efficient and ensures reduced manufacturing costs.

This paper aims to design and optimize the threaded fastener of leakage current particulate matter (PM) sensor. The corresponding air-tight test is conducted to ensure the reliability of the installation strategy with screw connection.

Research on the pressure-deformation curve of seal gasket was conducted and the vibration load of engine was considered for the calculation of the minimum installation pre-tightening force. Simultaneously, the danger threaded section area was calculated, and the carrying capacity was verified. The height of the welding line was studied to ensure the reliability of the application. FEA was carried out to acquire the relationship between local structure size and local stress for continuous improvement of thread connection. The installation torque range was acquired from the torque control principle for the pre-tightening force. The sealing reliability of the connector was proved with leakage.

The air tightness of the thread connector is proved to be fine. When the pre-tightening force is over 8,000 N, and its length reaches 2 mm, the connector has good reliability at ambient temperature. The tightening torque of 60-74 Nm can guarantee the reliable fixing ability of thread connector, and its plastic non-deformation ability in the process of repeated tearing down.

This paper provides an installation strategy and an optimization of PM sensor, which has a positive effect on the study and the manufacture of PM sensor. It is helpful to further develop PM sensor and after-treatment technology. This kind of real-time monitoring PM sensor needs to be studied further to achieve its commercial application.