ANALYSIS OF PRINTING PARAMETERS IN 3D PRINTED CARBON FIBER COMPOSITES USING DESIGN OF EXPERIMENTS

Additive manufacturing of carbon fiber reinforced polymers (CFRP) provides the advantage of quick prototyping of complex geometries, while maintaining light-weight characteristics and keeping structural integrity. This paper presents flexural strength data from 3D printing of an onyx and carbon fiber composites. A MarkForged Mark 2 3D printer, with a dual printer head, is used to 3D print several configurations of CFRP composites. The configurations are set to examine the extreme parameters of the rectangular fill pattern, including fill density, roof and floor layers, and wall layers. The print angle along with the fill pattern stays consistent. Each sample comprises twenty- four layers of CFRP and undergoes a three-point bend test. Test data of load, deflection, and maximum stress are compared among the different configurations. Results show that the roof/floor layer has the largest impact on the flexural strength for each configuration. The configurations with less roof/floor layers are able to take on a larger load, because there are more CFRP layers present; while specimens with more roof/floor layers withstand less load and behave more ductile. These results show that the amount of roof/floor layers can change the CFRP composite from its usual brittle characteristic to a ductile behavior.

Transverse bunch-by-bunch feedback system for time-resolved experiments at PLS-II

A description of the upgraded bunch-by-bunch feedback system for time-resolved experiments at Pohang Light Source II (PLS-II) is provided. The bunch-by-bunch feedback system has been upgraded to increase the single-bunch current in the hybrid fill pattern of the PLS-II facility. The project is part of the SPring-8 and PLS-II collaboration. The main features of the upgrade are to employ a single 500 MHz analog-to-digital converter (ADC) instead of the previous four 125 MHz interleaved ADCs for 500 MHz rate, to replace a single-loop two-dimensional feedback with two independent one-dimensional feedback loops, to implement the tune measurement function with a single bunch, and mainly to implement single-bunch and stretcher control. The realization of a 400 mA hybrid fill pattern including a 10 mA single bunch demonstrates the precision of the upgraded bunch-by-bunch feedback system.

Minding the Gap in Vertebroplasty: Vertebral Body Fracture Clefts and Cement Nonunion

BACKGROUND: Vertebroplasty and kyphoplasty are leading treatments for patients with vertebral body compression fractures. Although cement augmentation has been shown to help relieve pain and instability from fractures containing a cleft, there is some controversy in the literature regarding the procedure’s efficacy in these cases. Additionally, some of the literature blurs the distinction between clefts and cement patterns (including cement nonunion and cement fill pattern). Both clefts and cement patterns have been mentioned in the literature as risks for poorer outcomes following cement augmentation, which can result in complications such as cement migration. OBJECTIVES: This study aims to identify the prevalence of fracture clefts and cement nonunion, the relationship between them as well as to cement fill pattern, and their association with demographics and other variables related to technique and outcomes. STUDY DESIGN: Retrospective cohort study. SETTING: Interventional radiology department at a single site university hospital. METHODS: This retrospective cohort study assessed 295 vertebroplasties/kyphoplasties performed at the University of Colorado Hospital from 2008 to 2018. Vertebral fracture cleft and cement nonunion were the main variables of interest. Presence and characterization of a fracture cleft was determined on pre-procedural imaging, defined as an air or fluid filled cavity within the fractured vertebral body on magnetic resonance or computed tomography. Cement nonunion was evaluated on post-procedural imaging, defined as air or fluid surrounding the cement bolus on magnetic resonance or computed tomography or imaging evidence of cement migration. Cement fill pattern was assessed on procedural and/or post-procedural imaging. Pain improvement scores were based on a visual analog score immediately prior to the procedure and during clinical visits in the short-term follow-up period. Additional patient demographics, medical history, and procedure details were obtained from electronic medical chart review. RESULTS: Pre-procedural vertebral fracture clefts were demonstrated in 29.8% of our cases. Increasing age, secondary osteoporosis, and thoracolumbar junction location were associated with increased odds of clefts. There was no significant difference in pain improvement outcomes in patients following cement augmentation between clefted and non-clefted compression fractures. Clefts, especially large clefts, and cleft-only fill pattern were associated with increased odds of cement nonunion. Procedure techniques (vertebroplasty, curette, and balloon kyphoplasty) demonstrated similar proportion of cement nonunion and distribution of cement fill pattern. LIMITATIONS: Cement nonunion was observed in only 6.8% of cases. Due to this low proportion, statistical inference tends to have low power. Multiple levels were treated in nearly half of the study’s patients undergoing a single vertebroplasty/kyphoplasty session; in these cases, each level was treated as independent rather than spatially correlated within the same study patient. CONCLUSIONS: Vertebral body fracture clefts are not uncommon and are related to (but distinct from) cement nonunion and cement fill patterns. Our study shows that, although patients with clefts will benefit from cement augmentation just as much as patients without a cleft, the performing provider should take note of cement fill and take extra steps to ensure optimal cement fill. These providers should also identify cement nonunion and associated complications (such as cement migration) on follow-up imaging. KEY WORDS: Kyphoplasty, vertebroplasty, compression fracture, cement nonunion, vertebral fracture cleft, spine, cement augmentation

Enhancing 3D Printing Producibility in Polylactic Acid Using Fused Deposition Modelling and Machine Learning

Polylactic acid (PLA) is brittle in nature with extensive deformation property. For improvement of the end-use quality, it is of significant importance to enhance the producibility of fused deposition modeling (FDM)-printed objects in PLA. The purpose of this investigation is to boost toughness and to reduce the production cost of the FDM-printed tensile test samples with the desired part thickness. To attain the research purpose number of experiments are designed and analyzed by the Response Surface Method (RSM). The statistical analysis is performed to deal with this concern considering layer thickness, infill percentage, and extruder temperature as controlled factors. The tensile test specimens are printed based on the designed experiments, and the tensile strength tests are conducted by SANTAM 150 universal testing machine based on ASTM D638. The honeycomb internal fill pattern is applied for the production of light-weight and high-strength specimens. The area under Force- Extension curve up to fracture is acquired as the toughness of the printed specimens. This study also developed a modeling process using ANN and ANN-GA techniques for developing an accurate estimation for toughness, part thickness, and production cost as dependant variables. Results were evaluated by correlation coefficient and RMSE values. According to the modeling results, ANN-GA as a hybrid ML technique could successfully improve the accuracy of modeling about 7.5, 11.5 and 4.5 % for toughness, part thickness, and production cost, respectively, in comparison with those for the single ANN method. In the other side, the optimization results confirm that the optimized specimen is cost-effective and able to comparatively undergo deformation, which develops the usability of printed PLA objects. The research is accomplished under the constraints of PLA compatibility with existing fused deposition modeling setup without changing the functional hardware/software of the machine. Although the mechanical properties and dimensional accuracy of PLA have already been studied, there is little literature on the toughness of the printed PLA with honeycomb internal fill pattern.

Influence of the Infill Orientation on the Properties of Zirconia Parts Produced by Fused Filament Fabrication

The fused filament fabrication (FFF) of ceramics enables the additive manufacturing of components with complex geometries for many applications like tooling or prototyping. Nevertheless, due to the many factors involved in the process, it is difficult to separate the effect of the different parameters on the final properties of the FFF parts, which hinders the expansion of the technology. In this paper, the effect of the fill pattern used during FFF on the defects and the mechanical properties of zirconia components is evaluated. The zirconia-filled filaments were produced from scratch, characterized by different methods and used in the FFF of bending bars with infill orientations of 0°, ±45° and 90° with respect to the longest dimension of the specimens. Three-point bending tests were conducted on the specimens with the side in contact with the build platform under tensile loads. Next, the defects were identified with cuts in different sections. During the shaping by FFF, pores appeared inside the extruded roads due to binder degradation and or moisture evaporation. The changes in the fill pattern resulted in different types of porosity and defects in the first layer, with the latter leading to earlier fracture of the components. Due to these variations, the specimens with the 0° infill orientation had the lowest porosity and the highest bending strength, followed by the specimens with ±45° infill orientation and finally by those with 90° infill orientation.

Normalized and color-filled logarithmic gamma-ray logs to enhance subsurface stratigraphic interpretation of carbonates and siliciclastics

Modern petrophysical software has broad capabilities for the display and manipulation of subsurface digital log data and for its integration with core data. Color and scale are two of the most important display attributes that can be used to enhance the visualization and interpretation of rock properties. The gamma-ray (GR) log, the most important log used in subsurface interpretation, is conventionally displayed on a linear scale of American Petroleum Institute (API) units. This makes it difficult to interpret in very clean lithologies with low API values or where the range of values is very large. We determine how displaying GR values on a logarithmic scale enhances the recognition of cyclicity in lithofacies with low GR values concurrently with rocks with very high API values. We further enhance the GR curve with a color-fill pattern that is intuitive and suggests the lithofacies. We calibrate the core-derived lithofacies data to the color-fill pattern, interactively “tuning” it to match lithofacies boundaries, further increasing the value of the methodology. Because of the many factors that cause variation in recorded API values, we normalized the GR curves, either by bulk shifts or statistical means, so that they display the same colors for equivalent lithologies in all wells in a cross section. We have developed two integrated studies demonstrating techniques to improve the display and interpretation of borehole logs, specifically those of Mesozoic carbonates and evaporites of the Middle East and Cenozoic siliciclastic fluvial and marginal marine systems of the Llanos Foothills of Colombia. Many examples of custom color-fill patterns for petrophysical logs could be suggested, the possibilities being limited only by the data available and the interpretation being presented.

Implementation of ultrafast X-ray diffraction at the 1W2B wiggler beamline of Beijing Synchrotron Radiation Facility

The implementation of a laser pump/X-ray probe scheme for performing picosecond-resolution X-ray diffraction at the 1W2B wiggler beamline at Beijing Synchrotron Radiation Facility is reported. With the hybrid fill pattern in top-up mode, a pixel array X-ray detector was optimized to gate out the signal from the singlet bunch with interval 85 ns from the bunch train. The singlet pulse intensity is ∼2.5 × 106 photons pulse−1at 10 keV. The laser pulse is synchronized to this singlet bunch at a 1 kHz repetition rate. A polycapillary X-ray lens was used for secondary focusing to obtain a 72 µm (FWHM) X-ray spot. Transient photo-induced strain in BiFeO3film was observed at a ∼150 ps time resolution for demonstration.