Infill Volume Research Articles

Design of the shell-infill structures using a phase field-based topology optimization method

The design of shell-infill structures has been a focal point in the topology optimization community due to their advantages in energy absorption characteristics, strength-to weight ratio and bucking resistance. This paper introduces a phase field-based topology optimization method for designing shell-infill structures. Interface-related issues can be easily addressed through the phase field function. A coupled topology optimization process is proposed to establish the connection between the shell and infill, facilitating the generation of optimized structures. The shell thickness, infill pattern and infill volume percentage, can be naturally controlled by different model parameters. Additionally, multiscale phase field topology optimization integrates the numerical homogenization method to evaluate the effective elasticity matrix of the microstructural infill. The approach is introduced for a uniform, periodical microstructure layout in the infill region, thereby achieving superior mechanical properties. Numerical results indicate the effectiveness of the proposed method in the design of both 2D and 3D shell-infill structures.

Web Stiffening of Additive Manufactured Polylactide (PLA) Railroad Tracks Using Fiberglass Wrapping

Three-dimensional (3D) printed railroad tracks can properly address the rendering of a variety of topographic profiles of naturally occurring landscapes and reduce construction costs. Load tests of PLA railroad tracks found that web failure is a dominant failure mode. This paper evaluates the web stiffening strategies of additively fabricated PLA railroad tracks for rail-guided, micro-people movers (MPMs). To strengthen the track web, web-widening with additional PLA material and stiffening using composite reinforcement using glass fiber reinforced polymer (GFRP) wrap have been investigated. The composite wrapping technique was conducted by bonding fiberglass cloth to both sides of the web using a polymeric resin. Flexural load tests were conducted on the specimens with different infill volume percentages. A linear trend was observed on the peak bending capacities of specimens with PLA infill fiber contents ranging between 20% to 100%. Different failure modes were observed for the different percentage specimens during the tests. When compared to their unreinforced counterparts, the 60% infill specimen had the largest increase in strength about 1,500 N in bending with the addition of GFRP wrap. The tangent stiffnesses of all samples were calculated which showed the 100% infill specimen had the highest increase of approximately 50%. The wrapping reinforcement was found to significantly modify the failure mechanisms of the 3D-printed tracks with different infill volume percentages. The strengthening of the 3D-printed tracks using GFRP wrapping is also shown to be similar to the widening of web sections of the additively printed railroad tracks.

Conductive Additive Manufactured Acrylonitrile Butadiene Styrene Filaments: Statistical Approach to Mechanical and Electrical Behaviors.

Additive manufacturing is a process in which digital three-dimensional (3D) design data are used to build a component in layers by accumulating materials. There are many materials used in additive manufacturing technology. The most basic features that distinguish these materials are their strength and electrical behavior. They can be strong or flexible, resistant to abrasion, depending on the application used. Recently, 3D printing filament and polymeric composite materials combined with carbon nanostructures with electrical conductivity have been used. In this study, acrylonitrile butadiene styrene (ABS), a carbon black-filled conductive material with high strength and hardness, was preferred. The aim in this study is to focus on the mechanical and electrical behavior of the material processed in filament form. Fabrication of samples was done using a fused deposition modeling-based printer that controls filament orientation. Different experimental studies were conducted: (1) mechanical tests to determine the maximum tensile strength values of the samples; and (2) electrical tests to analyze the electrical resistances of the samples. In the design of the first experiment, infill volume, layer height, infill type, and printing direction were determined as factors affecting strength. In the design of the second experiment, the length, nozzle temperature, and measurement temperature were determined as the factors affecting the electrical resistance. Statistical analysis of the measured data was performed to evaluate the overall result of the experiments. Finally, a prediction model of real-time tensile strength and resistance values was created using machine learning algorithms. These algorithms are Gaussian Process Regression and Support Vector Machine. The results confirmed the known linear dependence of electrical resistance on the length of the 3D-printed conductive ABS samples and showed how changing the fabrication settings affected the strength values.

Failure analysis of nylon gears made by additive manufacturing

Additive manufacturing enables fast manufacturing of polymer gears directly from a 3D model. Failed polymer gears can be replaced easily and quickly using many different materials. Mechanical and thermal characteristic of gears manufactured using additive manufacturing are mostly dependent on selected manufacturing parameters and material. In this research, the influence of the most important manufacturing parameter (infill percentage) on failure types and service life of additive manufactured nylon gears is experimentally investigated. The experimental tests were carried out using a custom-made gear testing device. Samples with 20, 40, 60, 80 and 100% of infill volume were tested. Infill type, shell thickness, and manufacturing speed were the same for all samples. Service life of gears was tested and failure types were characterized.

Investigations into the effect of thermal annealing on fused filament fabrication process

ABSTRACT The mechanical properties of fused filament-fabricated specimens are the primary considerations of researchers. Process parameters have a significant impact on the mechanical strength of 3D-printed parts. In this work, the effect of process variables such as infill volume, pattern, layer height, nozzle temperature, and print speed on tensile and compressive strength of polylactic acid samples are investigated. The maximum tensile strength of 27.87 MPa was obtained at 90% infill density for gyroid pattern of a layer thickness of 0.1 mm at a nozzle temperature of 220°C and print speed of 30 mm/s. The maximum compressive strength of 38.21 MPa was achieved at 90% infill density for the triangle pattern of a layer thickness of 0.1 mm at a nozzle temperature of 220°C and print speed of 30 mm/s. Thermal annealing as a post processing method to enhance the mechanical properties is also explored. The effect of annealing temperatures 65°C, 95°C and 125°C and time 30, 60 and 120 minutes on mechanical strength were studied. Ultimate tensile strength showed an improvement of 25.26% to achieve 34.91 MPa whereas compressive strength increased by 21.87% to give 46.57 MPa strength.

Computation of Implicit Representation of Volumetric Shells with Predefined Thickness

We propose and validate a method to find an implicit representation of a surface placed at a distance h from another implicit surface. With two such surfaces on either side of the original surface, a volumetric shell of predefined thickness can be obtained. The usability of the proposed method is demonstrated through providing solid models of triply periodic minimal surface (TPMS) geometries with a predefined constant and variable thickness. The method has an adjustable order of convergence. If applied to surfaces with spatially varying thickness, the convergence order is limited to second order. This accuracy is still substantially higher than the accuracy of any contemporary 3D printer that could benefit from the function as an infill volume for shells with predefined thicknesses.

Non-destructive simulation of node defects in additively manufactured lattice structures

Abstract Additive Manufacturing (AM), commonly referred to as 3D printing, offers the ability to not only fabricate geometrically complex lattice structures but parts in which lattice topologies in-fill volumes bounded by complex surface geometries. However, current AM processes produce defects on the strut and node elements which make up the lattice structure. This creates an inherent difference between the as-designed and as-fabricated geometries, which negatively affects predictions (via numerical simulation) of the lattice’s mechanical performance. Although experimental and numerical analysis of an AM lattice’s bulk structure, unit cell and struts have been performed, there exists almost no research data on the mechanical response of the individual as-manufactured lattice node elements. This research proposes a methodology that, for the first time, allows non-destructive quantification of the mechanical response of node elements within an as-manufactured lattice structure. A custom-developed tool is used to extract and classify each individual node geometry from micro-computed tomography scans of an AM fabricated lattice. Voxel-based finite element meshes are generated for numerical simulation and the mechanical response distribution is compared to that of the idealised computer-aided design model. The method demonstrates compatibility with Uncertainty Quantification methods that provide opportunities for efficient prediction of a population of nodal responses from sampled data. Overall, the non-destructive and automated nature of the node extraction and response evaluation is promising for its application in qualification and certification of additively manufactured lattice structures.

Lessons from Structural Analysis of a Great Gothic Cathedral: Canterbury Cathedral as a Case Study

ABSTRACT Damage in Gothic cathedrals can occur due to single extreme events or long-term processes, often associated with large deformations and cracking. This paper presents the damage survey and structural assessment of a UNESCO world heritage site and one of the oldest, most visited and most known Christian temples in the UK: Canterbury Cathedral, in Kent. Inspection and damage survey showed repetitive crack patterns on the vault’s intrados, with more severity in the south aisle, including outward rotating movement and cracking in the south flying buttresses. Ambient vibration tests were carried out to identify the structure modal properties. An FE model of a typical transversal section of the nave and lateral aisles was prepared, and calibrated based on the tests. Nonlinear static analyses were performed, considering the main parameters of influence to the structure, as the construction process, the infill volume, the presence of lateral thrusts from the nave’s roof and differential settlements. A validated FE model, presenting sufficient correlation with the existing damage was used to determine the safety factors for lateral and vertical loading, which according to the local hazard are considered adequate. A comparison with limit analysis, based on the static approach, was also carried out.

Three-Dimensional Printed Models for Lateral Skull Base Surgical Training: Anatomy and Simulation of the Transtemporal Approaches.

Three-dimensional (3D) printing holds great potential for lateral skull base surgical training; however, studies evaluating the use of 3D-printed models for simulating transtemporal approaches are lacking. To develop and evaluate a 3D-printed model that accurately represents the anatomic relationships, surgical corridor, and surgical working angles achieved with increasingly aggressive temporal bone resection in lateral skull base approaches. Cadaveric temporal bones underwent thin-slice computerized tomography, and key anatomic landmarks were segmented using 3D imaging software. Corresponding 3D-printed temporal bone models were created, and 4 stages of increasingly aggressive transtemporal approaches were performed (40 total approaches). The surgical exposure and working corridor were analyzed quantitatively, and measures of face validity, content validity, and construct validity in a cohort of 14 participants were assessed. Stereotactic measurements of the surgical angle of approach to the mid-clivus, residual bone angle, and 3D-scanned infill volume demonstrated comparable changes in both the 3D temporal bone models and cadaveric specimens based on the increasing stages of transtemporal approaches (PANOVA<.003,<.007, and<.007, respectively), indicating accurate representation of the surgical corridor and working angles in the 3D-printed models. Participant assessment revealed high face validity, content validity, and construct validity. The 3D-printed temporal bone models highlighting key anatomic structures accurately simulated 4 sequential stages of transtemporal approaches with high face validity, content validity, and construct validity. This strategy may provide a useful educational resource for temporal bone anatomy and training in lateral skull base approaches.

Novel 3D printed synthetic dielectric substrates

ABSTRACTThis letter presents dielectric properties of air filled synthetic substrates fabricated in a single process using three‐dimensional printing. The permittivity and loss tangent of a given sized substrate can be changed by controlling the air infill volume fraction. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2344–2346, 2015

Effect of Varying the Volume Infill Sand on Synthetic Clay Surfaces in Terms of the Shoe-surface Friction

The friction developed by the shoe-surface interface on artificial clay has not been widely studied, and can influence player's performance and injury risk. The aim of this research was to investigate the effect of varying the quantity of infill sand on shoe- surface friction on an artificial clay court tennis surface. A laboratory-based mechanical test rig was used to measure the friction force developed at the shoe-surface interface. Additionally, the perception of a group of participants, performing a turning movement on the same surface under dry conditions, was collected in order to compare against the mechanical results. The relationship between the normal force and friction generated by the shoe-surface interaction was examined for surfaces with different sand in-fill volumes. The mechanical testing was performed under dry and wet conditions, showing strong and significant differences. Results indicated that the normal force significantly influenced the static and dynamic frictional forces. For lower sand infill volumes, as normal loading increased, the dry condition was found to exhibit the lowest peak static friction force and highest average dynamic friction force. However, for higher sand infill volume conditions, the opposite behaviour was observed. Strong and significant positive linear relationships were found between peak friction force and average dynamic friction force for all infill sand volumes and conditions. The mechanical results were in agreement with the perception data, which suggests that the participants were sensitive to the small changes in sand infill volumes.The findings of this study will therefore aid the understanding of tennis players’ perceived response to a tennis court surface. In order to get a better understanding of friction behaviour, further testing needs to be performed, and once the mechanisms involved are understood, surface properties could be modified to increase performance and reduce injury risk.

Fusion of multi‐resolution surface (terrestrial laser scanning) and subsurface geodata (ERT, SRT) for karst landform investigation and geomorphometric quantification

ABSTRACTA multi‐method research design based on terrestrial laser scanning, GIS, geophysical prospecting (electrical resistivity tomography, refraction seismics) and sedimentology is applied for the first time to investigate enclosed karst depressions in an integrated way. Fusing multi‐resolution surface and subsurface geodata provides profound insights into the formation, geometry and geomorphologic processes of dolines. The studied landforms, which are located in the Dikti Mountains of East Crete, are shown to be filled by loose sediments of thicknesses of up to 30 m that mainly consist of fine‐grained material overlying solid bedrock at depths below 35 to 45 m. By combining subsurface observations with geomorphometric calculations, local doline genesis can be traced back to initial collapse of fractured bedrock followed by subsequent infilling with colluvials. In order to define crucial methodological requirements and guidelines for data fusion, both the impact of different elevation models and the influence of data resolution are assessed. Surface volumes of depressions derived by the digital surface model are 7–21% higher than the results obtained from the terrain model due to vegetation. Similarly, estimates of infill volume calculated on the basis of geophysical outcomes and elevation data differ by up to 13%. Calculations of the landforms' current volumes (i.e. total surface and subsurface volume), however, are fairly insensitive to raster resolution. Hence, the distinct geomorphologic properties of landforms (e.g. shape, terrain roughness, slope inclination) substantially determine the geomorphometric analysis of both surface and subsurface data. As shown by the findings, data fusion to integrate digital terrain, geophysical and sedimentological datasets of varied resolutions benefits geomorphologic studies and helps provide a comprehensive image of landforms. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Adaptive TIN 필터링을 이용한 화성 계곡의 체적 추정

화성의 계곡망 추출 및 체적 분석은 과거 화성에 존재했을 지표수의 흐름을 규명할 수 있는 중요한 정보를 제공하고 있다. 이를 위해 본 연구에서는 기존의 이미지 프로세싱 분석을 대체할 수 있는 포인트 클라우드 기반의 지형 필터링 알고리즘을 사용한 새로운 방법론을 제시하였다. 우선 추출하고자 하는 계곡을 지면으로부터 분류하기 위해 대상지역에서 취득한 포인트 클라우드 자료의 고도값을 역전한 뒤, Adaptive TIN 필터링을 적용하였다. 분류한 지면과 대상물의 포인트 클라우드로부터 각각 ground DEM과 object DEM을 생성하고, 격자 단위로 두 DEM 간의 고도차와 object DEM으로부터 취득한 계곡 면적을 곱함으로써 최종적으로 계곡의 체적을 추정하였다. 화성 Tuscaloosa 분화구에 인접한 두 계곡을 대상으로 추정된 체적의 총 합은 약 <TEX>$1.41{\times}10^{11}m^3$</TEX>으로 Tuscaloosa 분화구 내 퇴적물의 체적 및 기존의 이미지 프로세싱 기법인 BTH 결과와 각각 12% 및 16%의 차이를 나타내었다. The investigation of valley networks and their volume provide important information about past water activities on Mars. As an alternative of conventional image processing methods, terrain filtering algorithm using pointcloud data is suggested in this study. First, the topography of pointcloud is inverted so that the valleys become positive features and the algorithm is then applied to distinguish the valleys from the surface. Ground DEM and object DEM are generated from both the valleys and the surface pointcloud then the volume of valleys is estimated by multiplying the height difference between the surface with valleys and the area of valleys based on grid cellsize. In the test of valleys adjacent to Tuscaloosa crater, the total volume of valleys was estimated to be <TEX>$1.41{\times}10^{11}m^3$</TEX> with the difference of 12% and 16% compared with the infill volume of Tuscaloosa crater and BTH result respectively.

A Reference Equation for Objectively Adjusting Dwell Volume to Obtain More Ultrafiltration in Daily Practice of Peritoneal Dialysis

Objectives. Few studies mention how to objectively adjust peritoneal dialysis (PD) dwell volume for adult continuous ambulatory peritoneal dialysis (CAPD) patients. We proposed a reference equation composed of parameters from the peritoneal equilibrium test (PET) for adjusting daily dialysate dwell volume to obtain more ultrafiltration volume. Better fluid control could reduce more fluid overload-related complications. Design. We used body mass index, waist circumference, intraperitoneal pressure, and other parameters from peritoneal equilibrium test to compose a reference equation for fine-tuning daily dwell volume. Patients and Setting. Eighty-eight PD patients in one center with laboratory data collected during half-yearly PET evaluations were enrolled. Instilled dialysate was composed of 2.57% glucose PD fluid, either 1500 ml or 2000 ml in volume. In addition to other demographic data, intraperitoneal pressure (IPP) was also measured twice in the supine position four hours apart. We applied statistical multivariate techniques of discrimination analysis and logistic regression to verify the most feasible and optimal formula to determine infill volumes for patients. Results. We determined a novel formula for calculating daily dialysate dwell volume, Z: Z = (0.523 × waist circumference) + (0.852 × body mass index), derived from rotating axes to obtain an accurate prediction rate of 80.68% using the multivariate approach. Conclusion. The novel formula used objective, real-time parameters for determining appropriate dwell volumes for PD patients to optimize maximal ultrafiltration volumes and reduce subjective abdominal discomfort. The novel formula makes frequent adjustment of daily dwell volume by physicians or patients easy to calculate.

Fundamental principles of indwelling urinary catheter selection.

Catheter selection is a skilled element of continence care, particularly when the catheter is intended to remain in situ for prolonged periods. It is important to choose carefully, referring to catheter length, material, Charrière size and balloon infill volume, any of which may--if not attended to correctly--cause problems. This article gives some advice on catheter selection and outlines what may occur if certain issues are dealt with incorrectly.

Catheters: design, selection and management.

Urinary catheterization is a common procedure that is performed on 12% of hospital patients (Crow et al, 1996) and 4% of community patients (Getliffe, 1990). When considering catheterization as a method of care, many decisions need to be made in order to select the optimum equipment and provide effective catheter care. This includes selecting the type of catheterization that needs to be performed, i.e. intermittent or indwelling, and choosing the right catheter material, size and balloon infill volume. The type and design features of the urinary drainage and suspensory system have a direct effect on individual patient comfort, dignity and life. Aspects of catheter care that need to be considered include: meatal hygiene, fluid intake, bladder washouts, constipation, clamping catheters, collecting specimens of urine, fixation of catheters and sexuality.

The Hudson Shelf Valley: Its role in shelf sediment transport

The Hudson Shelf Valley was deeply incised by Pleistocene lowstands of the sea. During the Holocene transgression, fluvial, estuarine, and estuary-mouth depositional environments were displaced landward, and sedimentation in these environments partially filled the valley. Holocene sediment thickness in the seaward half of the valley is about the same as on the shelf to either side, but in the landward half of the valley, 22 m of sediment is present versus 5–10 m on the adjacent shelf. Sediment volume calculations in the upper shelf valley show that there is about three times the infill volume east of the thalweg as compared to the infill to the west. This configuration indicates that the valley has served as a sediment trap and records the westward migration of the thalweg during the Holocene. Most of the infill was the result of littoral drift which transported sand westward along the south shore of Long Island during the Holocene transgression. Modern sediment transport, as calculated from currentmeter observations and inferred from bedform observations, is mainly south westward, along the regional trend of the isobaths and across the shelf valley. Therefore, infill on the eastern side of the shelf valley is continuing at present. Observations of the regional distribution of sediment types indicate that the asymmetrical valley fill is part of a pattern of bottom response to flow. The former drainage divides on both sides of the shelf valley are surfaced by coarse lag deposits on slopes facing northeast, into the direction from which the major storm flows come, while the down-current sides are mantled with fine sand.