Transverse Cross Section Research Articles

Computational and Experimental Studies on the Effect Back Pressure on Twist Extrusion Process

In the current study, aluminium 6063 alloy (AA6063) was successfully gain refined by twist extrusion (TE) technique. TE is a representative severe plastic deformation process to fabricate ultrafine-grained in bulk materials by repetitive passes. In order to investigate the influence of back pressure, a direct extrusion (DE) channel was embedded after the twist zone and the behavior of AA6063 was investigated and compared with and without this channel. Analyzing microstructural evolutions by scanning electron microscope and Vickers microhardness evaluations showed that, adding the DE channel increased the hardness distribution and a more homogenous structure was obtained. Finite element analysis was utilized to study the distribution of the equivalent plastic strain (PEEQ) numerically. According to the obtained results, with applying the TE process, strain increase was observed all over the sample surface, whereas modeling the DE channel after the twist zone caused a better homogeneity in the PEEQ distribution of the transverse cross-section. The PEEQ distribution during TE process can be correlated to the extent of grain refinement and the uniformity of ultrafine grains. This method seems to be very interesting and very promising for the future industrial application.

Effect of ultrasonic vibration on current density and keyholing capability of plasma arc

ABSTRACTUltrasonic-assisted plasma arc welding (U-PAW) process was developed to improve the penetrability. The current density of plasma arc on the anode surface was measured in plasma arc welding (PAW) and U-PAW processes. It was found that ultrasonic vibration can increase the peak value of the current density of plasma arc on anode surface. Both PAW and U-PAW experiments were conducted to examine the effect of ultrasonic vibration on the keyholing/penetrating capability of plasma arc. The weld macrographs at transverse cross-sections in PAW and U-PAW were also compared. The results show that the integration of ultrasonic vibration and the controlled pulse current waveform can ensure the open keyhole establishment and complete penetration at lower peak current or higher welding speed.

Features of the Spatial Localization of Particles in the Coherent Channeling Mode and the Mechanism for the Formation of Controlled Directional Radiation

Features of the spatial evolution of a wave function that describes the motion of fast particles in a planar channel in the coherent channeling mode are considered. It is shown that the interference of eigenstates leads to modulation of the probability density of particle localization in the transverse channel cross section and the longitudinal direction of nonquantized motion if the parametric coupling of longitudinal momentum and the energy of transverse particle motion are taken into account. In the case of a very narrow wave packet, the spatial structure of the probability density is close to the classical particle trajectory. In the case of a particle whose state corresponds to a plane wave before its entrance into the channel, the interference process leads to longitudinal-transverse focusing and the formation of periodically located clusters with a very large probability density. As the entrance angle increases, the position of these clusters approaches the channel walls. In this paper, it is shown that the presence of such clusters leads to the possibility of forming similarly located clusters of excited atoms and nuclei and to a new type of generation of quasicoherent directional radiation.

Role of liquid backfilling in reducing solidification cracking in aluminium welds

ABSTRACTThe solidification cracking susceptibility of aluminium alloys 2024, 2219, 6061 and 7075 was evaluated recently by the transverse motion weldability test (the lower sheet moved in the transverse direction of lap welding to cause cracking). The tested welds were analysed in the present study. Their transverse cross-sections showed wide backfilled cracks in 2219 (least susceptible) and narrow open cracks in 6061 (most susceptible). Their fracture surfaces showed continuous eutectic in 2219 and discontinuous eutectic in 6061, consistent with the less backfilling in 6061. T was plotted against (fS)1/2 (T: temperature; fS: fraction solid) to explain the differences. The critical local strain rate near the crack was estimated, significantly lower in 6061 than 2219 and consistent with the higher crack susceptibility of 6061.

Microstructural toughening mechanisms in nanostructured Al2O3/GdAlO3 eutectic composite studied using in situ microscale fracture experiments

This work uses in situ transmission electron microscopy (TEM) based micromechanical testing to isolate and quantify the microstructural toughening mechanisms active in nanostructured Al2O3/GdAlO3 eutectic samples. The effect of fracture direction across orthogonal sections of the rod-like eutectic was used to reveal the influence of different fracture paths and mechanisms on toughening. The average fracture toughnesses of the rod-like structures in the longitudinal cross-section and transverse cross-section are 2.4 MPa·m1/2 and 2.7 MPa·m1/2, respectively. Multiple samples tested in the longitudinal cross-section show significant R-curve toughening response, and obtain values greatly exceeding the initial values upon crack extension. It is concluded that nanoscale crack bridging induces deflection of the crack path, which leads extrinsic energy dissipation as the crack opens. Micropillar compressions are also performed to investigate the composite’s strength. Sample orientation strongly affects the deformation mode and interfacial sliding occurs when the maximal shear stress is parallel to the interface.

Correlation between pulsed laser parameters and MC carbide morphology in H13 tool steel/TiC composite coating

In this study, composite coatings were fabricated by preplacing a TiC layer on H13 tool steel and surface melting with a pulsed Nd: YAG laser. Since the morphology of hard phase particles is one of the determinants of the wear properties of composite coatings, the role of process variables on the shape and size of carbide precipitates was investigated. The transverse cross-section of the laser-scanned samples was studied by an optical microscope to evaluate the geometrical changes of alloyed areas. Scanning electron microscopy and X-ray energy dispersive spectroscopy were used to probe the microstructure and chemical composition of the coating layers. X-ray diffraction was used to identify the phases. The results showed that by the partial or total dissolution of TiC particles in the melt pool, TiC-type MC carbides precipitated as the primary phase. Alterations in pulse laser variables changed the geometry of the alloyed region and hence the concentration of dissolved Ti and C elements in the composite coating. Investigation of the effect of the laser variables in the form of “effective peak power density” (EPPD) revealed that increasing the EPPD led to an increase in the Fe/Ti weight ratio in the composite. As the Fe/Ti weight ratio increased, the shape of the MC precipitates changed gradually, from fully developed dendrites to petal, and polyhedral morphology.

Dynamics of chirped finite Olver Gaussian beam propagating paraxial to uniaxial crystal

Paraxial transmission characteristic of a second-order frequency chirped finite Olver Gaussian beam (CFOGB) in the uniaxial crystal orthogonal to the optical axial is investigated based on the generalized Huygens–Fresnel integral equation. The exact expression for the CFOGB passing through the uniaxial crystal is derived. The contour graph of the CFOGB intensity distribution on some transversal cross sections, the side view of this beam propagating in three different kinds of uniaxial crystal models are discussed, the influence of the frequency chirp parameter on the beam evolution properties is explored as well. We make sure that the formulae and the conclusions obtained can provide an effective and quick method to adjust and control this CFOGB evolution path and profile through choosing the proper uniaxial crystal structure and frequency chirp value to meet the practical usage.

Grain structure and texture of the SLM single track

The grain structure and texture of metal parts fabricated by selective laser melting (SLM) are of interest for their effect on the properties. The study of the SLM single track can reduce the variables to be concerned and, hence, facilitate the understanding of the development of grain and texture in the SLM process. In this work, the austenitic stainless 316L single tracks are fabricated at different scanning speeds, and they are characterized by electron backscattered diffraction (EBSD) from transverse, serial transverse, and longitudinal cross-sections. It is validated that curved grain is common in the SLM single track. The effects of the varied thermal gradient and the shape of the melt pool on competitive growth of grain are analyzed. All the three equivalent <001> orientations of the columnar grain are considered, which leads us to put forward a crystallographic feature of a favorable grain during the competitive growth in SLM. Such a crystallographic feature is validated by the texture of the SLM single track, especially the <001> // scanning direction (SD) texture.

Carbamoylethyl locust bean gum: Synthesis, characterization and evaluation of its film forming potential

The synthesis of carbamoylethyl locust bean gum (CLBG) was optimized using Plackett-Burman design. The generated model showed high significance (p < 0.05) to all the response variables which justifies the authenticity of the designed model. The optimal conditions i.e. acrylamide (5.12 mM), sodium hydroxide (3.00 mM), reaction temperature (50.97 °C) and reaction time (2.00 h) supported maximum -CONH2 content (5.44%), –COOH content (3.04%), degree of substitution (0.85) and product yield (7.25%, w/w). Carbamoylethylation of locust bean gum (LBG) involved substitution of its hydroxyl (-OH) moieties with amide group (-CH2CH2CONH2). FTIR and NMR spectroscopy confirmed the addition of amide group to CLBG. Scanning electron microscopy assured the slight rough surface of CLBG particles. Differential scanning calorimetry showed that carbamoylethylation of LBG lowered its melting temperature range (205.60–272.45 °C). However, the amorphous nature, non-Newtonian flow and shear-thinning behaviour of pure LBG were retained in CLBG. Further, CLBG films prepared with glycerol (1%, w/w, plasticizer) showed partially smooth surface and have clear transversal cross-sections. CLBG-glycerol films were highly water resistant and almost transparent. Further, CLBG-glycerol films showed good tensile strength (18.55 ± 0.02 MPa) and higher percentage elongation (6.11 ± 0.01%). Water vapor transmission rate of CLBG-glycerol film was quite lower (0.211 ± 0.001 g.mm/h.m2.kPa) which verified its higher resistance towards water.

Sandalwood-derived carbon quantum dots as bioimaging tools to investigate the toxicological effects of malachite green in model organisms

Malachite green is an N-methylated diaminophenylmethane dye that has generated much concern over its suggestive carcinogenic nature. After its excessive use in aquaculture industry as an effective ectoparasitide, much debate was raised over its toxicological effects leading to scientific studies conducted on animal models. Even after several bans, malachite green is still easily available in many parts of the world and unscrupulously even used to give green vegetables a fresher look. This study aims to address this concern by systematically studying the toxicological effects of malachite green through bioimaging in plant and animal cell and tissue. Sandalwood-derived carbon quantum dots have been used as a bioimaging tool since they are non-cytotoxic and show excellent fluorescence properties. Onion tissues demonstrate the translocation of the dye inside cells having high affinity for the nuclei and cell walls. Toxicological effects on the growth of Vigna radiata (mung beans) have been studied methodically. Bioimaging of the transverse cross-section of the dye-treated plant root shows a significant difference from the control. In animal cells, dose-dependent decrease in cell viability of MG-63 cells was observed with MG. CQD showed good fluorescence in both cytoplasm and nucleus of MG63 cells. In addition, CQDs were employed as a great tool for bioimaging of the histopathologically adverse effects of MG in Golden hamster animal model. This study showed CQDs could be used as an alternative non-site specific fluorescent probe for cell and tissue imaging for better visualization of cell and tissue architectural changes.

Laser Surface Modification of Aluminium Alloy AlMg9 with B4C Powder.

This paper presents the effects of laser treatment (fiber laser YLS-4000) on the microstructure and selected mechanical properties of the surface layer of AlMg (AlMg9) foundry alloy obtained by alloying with boron carbide (B4C). The correlation between laser alloying process parameters and selected properties of the formed layer was discussed. The studies were supported by microstructural analysis of the remelted zone (RZ), heat affected zone (HAZ), undissolved carbide particles, substrate material, and precipitates formed during rapid solidification. Metallographic investigations of the laser-treated layer were performed using optical microscopy and scanning electron microscopy (SEM). The elemental composition and a detailed analysis of chemical composition in micro-areas were carried out using energy dispersive X-ray spectroscopy (EDS). The remelting thickness, heat-affected zone (HAZ), and amount of base material in surface layers were determined. Microhardness tests were performed on transverse cross-sections of the remelted zone to obtain the hardness profiles in the base material (BM), remelted zone (RZ), and heat affected zone (HAZ). The hardness, roughness, and wear resistance measurements showed that the highest tribological properties of the obtained surface layer were achieved using 0.5 Bar protective gas (Ar) during alloying with B4C powder.

The Influence of Texture on the Ductile-to-Brittle Transition Behavior in Fe20Cr4.5Al Oxide Dispersion Strengthened Alloy

This paper reports on hardness, tensile properties and notch impact bending toughness values of an Fe20Cr4.5Al oxide dispersion strengthened (ODS) alloy specifically processed to achieved different preferential orientations: random, &lt;100&gt;, &lt;110&gt; and &lt;111&gt; parallel to the bar axis. In spite of the differences in the grain size, it was found for &lt;100&gt;, &lt;111&gt; and random orientations that the mean hardness values on the transverse cross sections is not remarkably sensitive to the texture. On the other hand, a significantly different mean hardness value for the material having the &lt;110&gt; crystalline orientation was found. Regarding the yield strength, it was found for random, &lt;100&gt; and &lt;111&gt; orientations that the yield strength is proportional to the Taylor’s factor. The difference between experimental and predicted yield strength values for &lt;110&gt; orientation was attributed to the offset effect induced by the dislocation cell size. The variation of the cleavage fracture strength with the texture was analyzed in the basis of two criteria: one based on the Normal Stress Law (macroscopic nature), and the other based on the assumption that fracture occurs from the propagation of a microcrack-like defect (microscopic nature). In this sense, it was concluded from the fractographic evidences that random and &lt;100&gt; orientations follow a mechanism where the fracture kinks along of the cleavage plane from a penny shaped microcrack nucleated in a second phase particle, meanwhile in the &lt;110&gt; and &lt;111&gt; orientations the fracture propagation arises from a penny shaped defect on the cleavage plane. Finally, the lower shelf values determined for the conditions studied are the same regardless of the texture and microstructure. The effect of texture on the notch toughness was noted where plastic flow predominates, i.e., in the ductile to brittle transition temperature and in the upper shelf energy.

Geophysical Study by Electrical Soundings of the Tartar Aquifer Unit, Boujdour Region, Morocco

The Tartar aquifer unit, is located at the SSO of the city of Boujdour, at a distance of nearly 86 km, and crossed (in its western part) by the National Road N1 connecting the towns of Boujdour and Lagouira passing through the vicinity of the city of Dakhla (PK40). It is exploited by rural settlements for domestic use (especially the inhabitants of fishing villages) and livestock watering, only through wells named Khtout Hobia (IRE 126/124) and Hassi Tartar known as Khtout Trayh (IRE 104/124). These wells have been tracked by a piezometric groundwater table and from 2011 to the present day. The interpretation of the electrical soundings in AB ≤ 2000 m allowed to differentiate the presence of two families of electrical soundings A and B, to establish the resistivity maps in AB = 200, 300 and 400 ihm&#8901m with qualitative aspects, to draw up the map of the isohypses of the roof of the intermediate Dt1 representing the impermeable floor of the aquifer and to highlight two types of discontinuities; electrical discontinuities corresponding to lateral facies changes (limit of erosion surfaces) separating the families A and B of electrical soundings and those corresponding to syn-sedimentary faults which structured the formations into horsts and grabens. The lithological sections of the existing water points and that of oil well 43-1 allowed the geological identification of the geoelectric layers highlighted by the electrical soundings diagrams. As a result, the sandstone and lumachelic formations constituting the aquifer are of Moghrebian-Pleistocene age represented by the resistant R (Family A), sometimes grouping, in its basal part, sandstone levels of the Miocene roof (Family B). These formations lie directly on the Miocene sandy marls represented by the intermediate Dt1. For the present work, we will focus only on the transverse geoelectric cross-section TA, with an SW-NE orientation, which characterizes all the longitudinal sections established following the correlation between the different electric sounding diagrams. It highlights the presence of the gravels G1 and G3 separated by the horst H1 where the resistant R is admitted as aquiferous at the level of the gravels G1 (Khtout Trayh well 104/124) and G3 (well 126/124) and sterile at the level of the horst H1.

Effects of rocking direction on load and forged geometry in cylinder upsetting

In this study, we demonstrate the reduction of forging loads using a rocking motion forging process with four linear actuators. We investigate the effects of the rocking direction on the upsetting load and shape through experiments using aluminum cylinders. The load reduction ratio is not significantly affected by the rocking direction under identical rocking conditions. The oval shape of the transverse cross section that was observed in the case of one-direction rocking changed into a near circular shape when two-direction rocking motion was applied. A positive correlation was confirmed between the load and the contact area reduction ratios, regardless of the rocking direction, even though the shape of contact area was different.

Microstructure and Properties of a 2.25Cr1Mo0.25V Heat‐Resistant Steel Produced by Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) technology was used to produce samples of a 2.25Cr1Mo0.25V heat‐resistant steel. The phase composition, microstructure, and crystal structure of the investigated material in the as‐cladded state and postcladding heat‐treated (705°C × 1 h) state were analysed by optical emission spectrometry (OES), optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The properties of the investigated material in the as‐cladded state and postcladding heat‐treated (705°C × 1 h) state were determined by a microhardness tester, mechanical properties tester, and Charpy impact tester. Through a study of the microstructure and properties, it is found that the investigated material produced by WAAM exhibits good forming quality and excellent metallurgical bonding properties, and no obvious defects are found. The microstructure consists mainly of Bg (granular bainite) and troostite precipitated at the grain boundaries. The results from high‐resolution transmission electron microscopy observations show that the crystal structures of the 2.25Cr1Mo0.25V heat‐resistant steel samples produced by WAAM in the as‐cladded condition have many defects, such as dislocations and martensite‐austenite (M‐A) constituents, and their grain edges are sharp. There is a dramatic decrease in the dislocations in the 2.25Cr1Mo0.25V heat‐resistant steel samples produced by the WAAM condition after the postcladding heat treatment (705°C × 1 h), and the grains become smooth. The distribution of the microhardness in the longitudinal and transverse cross sections of the samples is very uniform. The average longitudinal and transverse microhardness of the samples in the as‐cladded state is 310 HV0.5 and 324 HV0.5, respectively. The average longitudinal and transverse microhardness of the samples after post‐cladding heat treatment is 227 HV0.5 and 229 HV0.5, respectively. The yield strength of the samples without a postcladding heat treatment is 743 MPa, the tensile strength is 951 MPa, the elongation is 10%, and the Charpy impact value at ‐20°C is 15 J. After the postcladding heat treatment, the yield strength, tensile strength, elongation, and Charpy impact value of the samples are 611 MPa, 704 MPa, 14.5%, and 70 J, respectively.

Effects of contusion load on cervical spinal cord: A finite element study.

Injury of cervical spine is a common injury of locomotor system usually accompanied by spinal cord injury, however the injury mechanism of contusion load to the spinal cord is not clear. This study aims to investigate its injury mechanism associated with the contusion load, with different extents of spinal cord compression. A finite element model of cervical spinal cord was established and two scenarios of contusion injury loading conditions, i.e. back-to-front and front-to-back loads, were adopted. Four different compression displacements were applied to the middle section of the cervical spinal cord. The distributions of von Mises stress in middle transverse cross section were obtained from the finite element analysis. For the back-to-front loading scenario, the stress concentration was found in the area at and near the central canal and the damage may lead to the central canal syndrome from biomechanical point of view. With the front-to-back load, the maximum von Mises stress located in central canal area of gray matter when subject to 10% compression, whilst it appeared at the anterior horn when the compression increased. For the white matter, the maximum von Mises stress appeared in the area of the anterior funiculus. This leads to complicated symptoms given rise by damage to multiple locations in the cervical spinal cord. The illustrative results demonstrated the need of considering different loading scenarios in understanding the damage mechanisms of the cervical spinal cord, particularly when the loading conditions were given rise by different pathophysiological causes.

Seismic response of large diameter buried concrete pipelines subjected to high frequency earthquake excitations

Buried pipelines are tubular structures that cross large areas with different geological conditions. During an earthquake, imposed loads from soil deformations on pipelines may cause drastic damages. In this study two dimensional finite element models of pipelines and surrounding soils are used for simulation of seismic waves that propagate from the bedrock through the soil. The models describe both longitudinal and transverse cross-sections of pipelines and the soil-pipe interaction is described as a nonlinear behaviour. The effects of uniform ground with different burial depth and soil layer thickness, soil stiffness and non-uniform ground on the seismic response of reinforced concrete pipelines is studied. Two earthquakes, with high and low frequency contents, are employed for the dynamic analysis. The results show a significant effect on the response due to non-uniform ground caused by inclined bedrock, especially for high frequency earthquake excitations.

Technical Stability of Very Slender Rectangular Columns Compressed by Ball-And-Socket Joints without Friction

Stability of load-bearing members, as known, is a challenging issue and several tools are available for designers. Disregarding the material properties in use, the avoidance of possible stability troubles is a mandatory and challenging step of the overall design process. In this study, a theoretical model is presented for the of loss of stability in elastic states of very slender rectangular shell elements axially compressed through ball-and-socket joints without friction. According to this theory, as shown, a loss of carrying capacity of very slender columns in elastic states occurs when the line of force leaves a critical transverse cross-section. The critical transverse cross-section, moreover, progressively moves because of the superposition of bending and pure compression. The theory allows to determine the governing differential equations of curved central lines and their slopes, as well as the critical stresses of columns, in the form of surface function in dependence on slenderness ratios and cross-sectional areas. The graphs for the elastic deflected central line y(x), slope dy/dx, dependence yL/2(P), stresses and strains for a rectangular column made of steel and compressed by ball-and-socket joints without friction, as well as the corresponding surface graphs of critical stress, are presented in this study. The obtained surface graphs of critical stresses are then discussed and compared with Euler’s formulation.

Graph-analytical optimization of the transverse vertical cross-section of a contact zone between soil and an elastic wheeled mover

The intensification of agricultural production under modern conditions implies the use of super-powerful mobile technical means, which leads to an increase in the levels of technogenic impact on soil and, consequently, deteriorates its fertility. Therefore, the most acute issue related to current agricultural production is aimed at resolving the task on improving the operational indicators of wheeled running systems of mobile technical means. This necessitates an analytical study into the processes of soil deformation under the elastic motors of mobile wheeled agricultural machinery. We have proposed a procedure of the graph-analytical step-by-step modeling of the process of soil deformation under pneumatic tires of mobile agricultural equipment taking into consideration the changing shape of an elastic tire sheath. Using appropriate graphic models makes it possible to explore, in stages, the process of soil compaction inside the profile of the track it formed. It has been found that in the contact area «deformed soil – the surface of an elastic wheeled mover of the mobile vehicle» the highest level of compaction is observed in the soil layer, which is directly in contact with the elastic mover. The depth of the recompacted soil layer on the «track bottom» depends on the dimensions of a tire of the wheeled mover and does not exceed the value of 0.075 width of the tire. The highest soil compaction level is observed in the area directly adjacent to the gauge. It has been established that the most dangerous design of a pneumatic tire, in terms of soil overcompaction in the track, is the shape of an elastic tire sheath that is described by the curve of the Cassini oval with four points of inflection. We have outlined distinctive features of recommendations to determine the operational values of tire working pressure depending on specific physical-mechanical and agro-technological properties of soil and the character of performed technological operations

AGROCHEMICALS AND STEM CUTTING TYPES FOR PLANTLET PRODUCTION OF Spondias sp

ABSTRACT Umbu-caja (Spondias sp.) is a fruit tree native to the Northeast region of Brazil, which is grown because of its highly valuable fruits for fruit processing industries. The objective of this work was to evaluate the effect of agrochemical applications and cutting types on the rooting and development of Spondias sp. plantlets. The experiment was conducted at the experimental field of the Embrapa Tropical Agroindustry, in Pacajus, CE, Brazil. A randomize block experimental design was used, with five treatments - control (T1); cuttings with two lesions at the base (CL) + rooting gel (RG) (Sela Gel®) (T2); CL + rooting fertilizer (RF) (Radimax®) (T3); cuttings with two transversal cross sections at the base (CS) + RG (T4); and CS + RF (T5). The environments (blocks) used were: full sun; 100% shade ceiling; 50% shade walls and ceiling; and 50% shade ceiling. The plots consisted of eight cuttings, totaling 160 cuttings. Propagules were taken from Spondias sp. plants to make woody cuttings with length of 25 cm, diameter of 29.7 mm, and mean bud per cutting of 8.7. All cuttings were immediately treated with a 0.05% sodium hypochlorite solution for four minutes before making the lesions and transversal cross sections and applying the treatments. The RG was applied by brushstroke, and the RF was applied by immersion in an aqueous solution of 10 mL L-1 for 10 minutes. The cuttings were planted into 6-liter black plastic pots filled with a pasteurized mixture of vermiculite, coconut husk powder, ground leaf fibers of Copernicia prunifera, and carbonized rice husk (2:1:1:1; v v-1). The treatments and blocks significantly affected the rooting and development of cuttings. The treatment with CS and application of the RG (T4) promoted root callus formation, rooting, and vigorous development of plantlets, whereas the RF (T3 and T5) failed to promote root formation.