scholarly journals The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 374 ◽  
Author(s):  
Inka Dressler ◽  
Niklas Freund ◽  
Dirk Lowke
Keyword(s):  
3D Printing ◽  
Yield Stress ◽  
Fresh Concrete ◽  
Testing Machine ◽  
Image Correlation ◽  
Early Age ◽  
Stress Evolution ◽  
Functional Interaction ◽  
Concrete Properties ◽  
Instantaneous Increase

Recently, the progress in 3D concrete printing has developed enormously. However, for the techniques available, there is still a severe lack of knowledge of the functional interaction of processing technology, concrete rheology and admixture usage. For shotcrete 3D printing technology, we present the effect of accelerator dosages (0%, 2%, 4% and 6%) on fresh concrete properties and on interlayer strength. Therefore, early yield stress development up to 90 min is measured with penetration resistance measurements. Deformation of layers under loading is investigated with digital image correlation and a mechanical testing machine. One point in time (10 min after deposition) is examined to quantify vertical buildability of elements depending on the accelerator dosage. Four different interlayer times (0, 2, 5 and 30 min), which occur for the production of small and large elements as well as due to delay during production, are investigated mechanically as well as quantitatively with computed tomography regarding the formation of cold joints. With increased accelerator dosage, an instantaneous increase in early age yield stress and yield stress evolution was observed. An increase in interlayer time leads to a reduced strength. This is mainly attributed to the observed reduced mechanical interlocking effect of the strands. Finally, a model to describe interlayer quality is presented. In the end, advantages as well as limitations of the findings are discussed.

scholarly journals Rheological Property Criteria for Buildable 3D Printing Concrete

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 657 ◽  
Author(s):  
Hoseong Jeong ◽  
Sun-Jin Han ◽  
Seung-Ho Choi ◽  
Yoon Lee ◽  
Seong Yi ◽  
...  
Keyword(s):  
3D Printing ◽  
Stress Distribution ◽  
Yield Stress ◽  
Fresh Concrete ◽  
Maximum Shear Stress ◽  
Initial Yield Stress ◽  
Elapsed Time ◽  
Initial Yield ◽  
Cfd Analyses ◽  
Hardening Coefficient

Fresh concrete used in 3D printing should ensure adequate yield stress, otherwise the printed concrete layer may suffer intolerable deformation or collapse during the printing process. In response to this issue, an analytical study was carried out to derive the initial yield stress and hardening coefficient of fresh concrete suitable for 3D printing. The maximum shear stress distribution of fresh concrete was calculated using a stress transformation equation derived from the equilibrium condition of forces. In addition, the elapsed time experienced by fresh concrete during the printing processes was estimated and was then substituted into the elapsed time-yield stress function to calculate the yield stress distribution. Based on these results, an algorithm capable of deriving both the initial yield stress and the hardening coefficient required for printing fresh concrete up to the target height was proposed and computational fluid dynamics (CFD) analyses were performed to verify the accuracy of the proposed model.

scholarly journals A Novel Approach for a Faster Prototyping of Winter Sport Equipment Using Digital Image Correlation and 3D Printing

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 125
Author(s):  
Martino Colonna ◽  
Benno Zingerle ◽  
Maria Federica Parisi ◽  
Claudio Gioia ◽  
Alessandro Speranzoni ◽  
...  
Keyword(s):  
3D Printing ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Sport Activity ◽  
Image Correlation ◽  
Topological Optimization ◽  
Design Parameters ◽  
Sport Equipment ◽  
Novel Approach ◽  
3D Printed

The optimization of sport equipment parts requires considerable time and high costs due to the high complexity of the development process. For this reason, we have developed a novel approach to decrease the cost and time for the optimization of the design, which consists of producing a first prototype by 3D printing, applying the forces that normally acts during the sport activity using a test bench, and then measuring the local deformations using 3D digital image correlation (DIC). The design parameters are then modified by topological optimization and then DIC is performed again on the new 3D-printed modified part. The DIC analysis of 3D-printed parts has shown a good agreement with that of the injection-molded ones. The deformation measured with DIC are also well correlated with those provided by finite element method (FEM) analysis, and therefore DIC analysis proves to be a powerful tool to validate FEM models.

scholarly journals Transverse Isotropic Behavior Identification using Digital Image Correlation of a Pre-structured Material Manufactured by 3D Printing

2020 ◽  
Vol 28 ◽  
pp. 978-985
Author(s):  
Marouene Zouaoui ◽  
Julien Gardan ◽  
Pascal Lafon ◽  
Carl Labergere ◽  
Ali Makke ◽  
...  
Keyword(s):  
3D Printing ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
Transverse Isotropic

Enhancing the Yield Stress in Liquid Polydimethylsiloxane to Allow Its 3D Printing: Hydrogels as Removable Fillers

2021 ◽  
Vol 306 (2) ◽  
pp. 2000553
Author(s):  
Clément Perrinet ◽  
Edwin‐Joffrey Courtial ◽  
Arthur Colly ◽  
Christophe Marquette ◽  
René Fulchiron
Keyword(s):  
3D Printing ◽  
Yield Stress

scholarly journals Comparison of Resistive and Optical Strain Measurement for Early Fracture Detection

2020 ◽  
Vol 6 (3) ◽  
pp. 196-199
Author(s):  
Alina Carabello ◽  
Constanze Neupetsch ◽  
Michael Werner ◽  
Christian Rotsch ◽  
Welf-Guntram Drossel ◽  
...  
Keyword(s):  
Surgical Training ◽  
Error Detection ◽  
Strain Measurement ◽  
Testing Machine ◽  
Image Correlation ◽  
Strain Gauges ◽  
Measurement Technology ◽  
Bone Surface ◽  
Fracture Detection ◽  
Local Strains

AbstractTo increase learning success in surgical training, physical simulators are supplemented by measurement technology to generate and record objective feedback and error detection. An opportunity to detect fractures following hip stem implantation early can be measurement of occurring strains on bone surface. These strains can be determined while using strain gauges, digital image correlation (DIC) or photoelasticity. In this research strain gauges and DIC were compared regarding their suitability as strain measurement tools for use in physical simulators. Therefore a testing method was described to replicate the implantation of a hip stem. Testing devices modelled on a realistic prosthesis were pressed into prepared porcine femora in a two-step procedure with a material testing machine. The local strains occurring on bone surface were determined using an optical measurement system for DIC and strain gauges. The initial fractures in the tested femora are located medial-anterior in most cases (73,6%). With increasing indentation depth of the test device, the strains on bone surface increase. Comparing the local strains determined by DIC and strain gauges consistencies in curves are noticeable. Maximal determined strains before fracturing amount to 0,69% with strain gauges and 0,75% with DIC. In the range of the fracture gap, strain gradients are determined by using DIC. However the detected surfaces are of low quality caused by gaps and motion artefacts. The results show strains on bone surfaces for early fracture detection are measurable with strain gauges and DIC. DIC is assessed as less suitable compared to strain gauges. Furthermore strain gauges have greater level of integration and economic efficiency, so they are preferred the use in surgical training simulators.

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