Binder Jetting and Infiltration of Metal Matrix Nanocomposites

The ability to produce a dense part of Al-based metal matrix nanocomposites using binder jetting followed by infiltration was investigated. A green density above 1.58 g/cm3 was determined to be necessary for spontaneous direct liquid infiltration to commence, and a press-compaction-assisted binder jetting process is needed to achieve this benchmark. A green density of 1.64±0.02 g/cm3 only resulted in a density of 1.65±0.03 g/cm3 by sintering at 1050 °C, which showed that densification is not possible with sintering alone. However, infiltration with Al-6061 produced specimens with a density of 2.74±0.04 g/cm3, which corresponded to a density improvement of 65%. Moreover, the infiltrated specimens had a low open porosity of 2.71±0.95% and a high hardness of 54 HRA. This study suggests that it is feasible to manufacture parts with complex shapes and superior mechanical properties using binder Jetting followed by infiltration.

An Algorithm for Partitioning Objects Into a Cube Skeleton and Segmented Shell Covers for Parallelized Additive Manufacturing

Despite a growing application of additive manufacturing, build volume has limited the size of fabricated parts. Machines that can produce large-scale parts in whole have high costs and less commercially available. A workaround is to partition the desired part into smaller partitions which can be manufactured in parallel, with the added benefit of controlling process parameters for each partition independently and reducing manufacturing time. This paper proposes an approach that divides a part into a cube skeleton covered by shell segments where all components can be fabricated with smaller 3D printers. The proposed algorithm first hollows out the original fully dense part to a user-specified thickness, then partitions the part into 26 surrounding regions using the six faces of the maximally inscribed cube (or cuboid). Islands, i.e., small, disconnected partitions within each region, are combined with the smallest neighbor to create up to 26 connected partitions. To minimize the number of printed partitions, the connected partitions are ranked based on their volume and combined with their smallest neighbor in pairs in descending order, while ensuring each pair fits within a pre-selected build volume of available 3D printers. The final partitioned shell segments, the cube (or cuboid) center, and the secondary layer of cubes propagated from the face centers of the maximally inscribed cube are generated by the algorithm. Results of two cases are shown.

Bending Properties of Lightweight Copper Specimens with Different Infill Patterns Produced by Material Extrusion Additive Manufacturing, Solvent Debinding and Sintering

Material extrusion additive manufacturing (MEX) is a versatile technology for producing complex specimens of polymers, ceramics and metals. Highly-filled filaments composed of a binder system and a high-volume content of sinterable powders are needed to produce ceramic or metal parts. After shaping the parts via MEX, the binder is removed and the specimens are sintered to obtain a dense part of the sintered filler particles. In this article, the applicability of this additive manufacturing process to produce copper specimens is demonstrated. The particular emphasis is on investigating the production of lightweight specimens that retain mechanical properties without increasing their weight. The effect of infill grades and the cover presence on the debinding process and the flexural properties of the sintered parts was studied. It was observed that covers could provide the same flexural strength with a maximum weight reduction of approximately 23%. However, a cover on specimens with less than 100% infill significantly slows down the debinding process. The results demonstrate the applicability of MEX to produce lightweight copper specimens.

Extreme Image Classification Algorithm Based on Multicore Dense Connection Network

Extreme images refer to low-quality images taken under extreme environmental conditions such as haze, heavy rain, strong light, and shaking, which will lead to the failure of the visual system to effectively recognize the target. Most of the existing extreme image restoration algorithms only handle the restoration work of a certain type of image; how to effectively recognize all kinds of extreme images is still a challenge. Therefore, this paper proposes a classification and restoration algorithm for extreme images. Due to the large differences in the features on extreme images, it is difficult for the existing models such as DenseNet to effectively extract depth features. In order to solve the classification problem in the algorithm, we propose a Multicore Dense Connection Network (MDCNet). MDCNet is composed of dense part, attention part, and classification part. Dense Part uses two dense blocks with different convolution kernel sizes to extract features of different sizes; attention part uses channel attention mechanism and spatial attention mechanism to amplify the effective information in the feature map; classification part is mainly composed of two convolutional layers and two fully connected layers to extract and classify feature images. Experiments have shown that the recall of MDCNet can reach 92.75% on extreme image dataset. At the same time, the mAP value of target detection can be improved by about 16% after the image is processed by the classification and recovery algorithm.

A novel design, analysis and 3D printing of Ti-6Al-4V alloy bio-inspired porous femoral stem

The current study is proposing a design envelope for porous Ti-6Al-4V alloy femoral stems to survive under fatigue loads. Numerical computational analysis of these stems with a body-centered-cube (BCC) structure is conducted in ABAQUS. Femoral stems without shell and with various outer dense shell thicknesses (0.5, 1.0, 1.5, and 2 mm) and inner cores (porosities of 90, 77, 63, 47, 30, and 18%) are analyzed. A design space (envelope) is derived by using stem stiffnesses close to that of the femur bone, maximum fatigue stresses of 0.3σys in the porous part, and endurance limits of the dense part of the stems. The Soderberg approach is successfully employed to compute the factor of safety Nf > 1.1. Fully porous stems without dense shells are concluded to fail under fatigue load. It is thus safe to use the porous stems with a shell thickness of 1.5 and 2 mm for all porosities (18–90%), 1 mm shell with 18 and 30% porosities, and 0.5 mm shell with 18% porosity. The reduction in stress shielding was achieved by 28%. Porous stems incorporated BCC structures with dense shells and beads were successfully printed.

INTER-RELATIONSHIP OF LIVER AS A PART OF HAYAT AL AZA (MORPHOLOGY) IN THE FORMATION OF TEMPERAMENT IN UNANI SYSTEM OF MEDICINE

Temperament occupies an important place in Unani Medicine and forms the basis of pathology, diagnosis and treatment. This concept was originally introduced by Hippocrates (460-370 BC) in which he stated that “It is more important to know what sort of person has a disease than to know what sort of disease a person has”. Ibn Sina says “Allah most beneficent has furnished every one and each of its member with a temperament which is entirely the most appropriate and best adopted for the performance of its functions and passive state”. Human interest in the liver is as old as the science of medicine. Since time immemorial it has been considered as one of the vital organs of a human body. It was during the Greco-Arabian period of medical history that the intimate relationship between the liver and the health of the individual was established. Considering liver as an important and essential organ, Hippocrates (460-377 BC) says “if we live a good life, it is because of the health of our liver” (Ibn-e-Zohr, 1989). Galen (131-210AD) believed that liver retained a dominant role as the “seat of sanguification and the source of veins”. According to Avicenna- “Physicians regard the liver as the seat of manufacture of the dense part of the humours” (Grunner, 1930). Avicenna further writes- “Liver is a large factory where due to digestive and metabolic changes, the various humours of the body are formed in plenty (Kabiruddin, 1947). According to Unani Physicians, humours play an important and deciding role in the creation of human temperament. Therefore it can be revealed that liver is an important metabolic organ, which plays an important role in the formation of temperament of a person.

Nobeyama 45 m mapping observations toward Orion A. II. Classification of cloud structures and variation of the 13CO/C18O abundance ratio due to far-UV radiation

We present results of the classification of cloud structures toward the Orion A Giant Molecular Cloud based on wide-field 12CO (J = 1–0), 13CO (J = 1–0), and C18O (J = 1–0) observations using the Nobeyama 45 m radio telescope. We identified 78 clouds toward Orion A by applying Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) to the data cube of the column density of 13CO. Well-known subregions such as OMC-1, OMC-2/3, OMC-4, OMC-5, NGC 1977, L1641-N, and the dark lane south filament (DLSF) are naturally identified as distinct structures in Orion A. These clouds can also be classified into three groups: the integral-shaped filament, the southern regions of Orion A, and the other filamentary structures in the outer parts of Orion A and the DLSF. These groups show differences in scaling relations between the physical properties of the clouds. We derived the abundance ratio between 13CO and C18O, $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$, which ranges from 5.6 to 17.4 on median over the individual clouds. The significant variation of $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$ is also seen within a cloud in both the spatial and velocity directions and the ratio tends to be high at the edge of the cloud. The values of $X_{^{13}\mathrm{CO}}/X_{\mathrm{C}^{18}\mathrm{O}}$ decrease from 17 to 10 with the median of the column densities of the clouds at the column density of $N_{\mathrm{C^{18}O}} \gtrsim 1 \times 10^{15}\:$cm−2 or visual extinction of AV ≳ 3 mag under the strong far-ultraviolet (FUV) environment of G0 > 103, whereas it is almost independent of the column density in the weak FUV radiation field. These results are explained if the selective photodissociation of C18O is enhanced under a strong FUV environment and it is suppressed in the dense part of the clouds.

A New Multifunctional β Ti Alloy Produced via Powder Metallurgy for Biomedical Applications

Recent studies have revealed remarkable properties in β- Ti alloys, including low elastic modulus, high strength and superelasticity. The unique properties and potentials in engineering and biomedical applications have invoked many physicists, material scientists and metallurgists to study its phenomenon. The requirements of these alloys in biomedical applications restrict the usage of toxic or allergic elements in the alloy design. Only a few alloying elements are suitable for developing non-toxic β titanium alloys such as Nb , Ta and Zr . In this study a press-and-sinter process was used to consolidate the elemental powder mixture of Ti - Nb - Ta - Zr . Solid state sintering studies were established to investigate the effect of various green densities, sintering temperatures (i.e. 1650 °C – 1700 °C) and sintering atmosphere (i.e. Argon and Vacuum). PM near net shape process of showed a pathway to obtained a near dense part at sintered density of ~97 % with compaction pressure of 707 MPa at 1700°C. Majority of the sintered Ti -23 Nb -0.7 Ta -2 Zr (at.%) alloy's structure is β- austenite (bcc).