Linear Grooves Research Articles

Analysis of light extraction in light pipes by linear and elliptical grooves using different source aperture angles

An analytical and numerical analysis of light extraction from light pipes using total internal reflection grooves with linear and elliptical profiles is presented. We performed the study considering light sources with different aperture angles, such as sunlight delivered by optical fibers and LEDs. With this analysis, we propose an analytical model based on the edge ray concept that allows selecting the most convenient profile, size, and orientation of the groove to extract light with a desired illumination area according to the source aperture angle employed in the light pipe system. We also have numerically found that for sources with high aperture angles, the light extracted by the linear and elliptical grooves produces similar irradiance and angular distributions, whereas for sources with low aperture angles, the elliptical groove focuses the extracted light and produces a higher angular distribution in comparison to this obtained with the linear groove. Our results are scalable to different light pipe dimensions and provide a systematic way to obtain preliminary designs of grooves for lighting systems that employ optical sources with different aperture angles.

A green, maskless, and universal preparation method for patterned surfaces on various metal substrates

Superhydrophobic surfaces with hydrophilic patterns are widely used in liquid transport, water collection, and cell screening. However, the preparation process of these patterned surfaces tends to be time-consuming and complicated. Here, we apply a simple, efficient and versatile laser processing method. Superhydrophobic substrates are firstly constructed by laser treatment and fluoroalkylsilane (FAS) solution; then superhydrophilic patterns such as dot-shaped or linear grooves are processed by secondary laser treatment. The dot-shaped grooves have strong adhesive force to droplets, and the linear grooves show obvious anisotropic adhesion behavior. On the basis of these features, applications like liquid transport, droplets grabbing and mixing, and fog collection are successfully achieved. The proposed laser processing method is applicable for various metal substrates including aluminum, copper, steel and titanium, and is expected to have promising application prospects in lab-on-a-chip system and chemical analysis domains.

Residual Stresses and Surface Roughness Analysis of Truncated Cones of Steel Sheet Made by Single Point Incremental Forming

The dimensional accuracy and mechanical properties of metal components formed by the Single Point Incremental Forming (SPIF) process are greatly affected by the prevailing state of residual stress. An X-ray diffraction method has been applied to achieve an understanding of the residual stress formation caused by the SPIF process of deep drawing a quality steel sheet drawpiece. The test object for an analysis of residual stress distribution was a conical truncated drawpiece with a slope angle of 71° and base diameter of the cone of 65 mm. The forming process has been carried out on a 3-axis HAAS TM1P milling machine. Uniaxial tensile tests have been carried out in the universal tensile testing machine to characterize the material tested. It was found that the inner surface of the drawpiece revealed small linear grooves as a result of the interaction of the tool tip with the workpiece. By contrast, the outer surface was free of grooves which are a source of premature cracking. The stress profile exhibits a nonlinear distribution due to different strengthening of the material along the generating line of the truncated conical drawpiece. The SPIF parts experienced a maximum residual stress value of about 84.5 MPa.

Numerical Investigation of the Derivative Cutting Effect of Micro-Textured Tools in Dry Cutting of Ti6Al4V

In this study, FEM simulation of titanium alloy machining with micro-textured tool using Thirdwave AdvantEdge. Micro-scale textures on the rake face of the cutting tool is a single linear groove parallel to the cutting edge. Viewing simulation results ,derivative cutting did occur under the cutting parameters in this study. The tool-chip contact length decreases due to the existence of the micro-textures. Shear angle increases which indicates smaller deformation of the cutting layer and thus smaller cutting forces and cutting temperature. However, the derivative cutting effect increases the variations of the cutting forces. Therefore, strength of the cutting tool must be taken into consideration during the designation of the micro-textured cutting tool.

Advanced microstructural characterisation of cast ATI 718Plus\xae\u2014effect of homogenisation heat treatments on secondary phases and repair welding behaviour

The influence of base metal conditions on the weld cracking behaviour of cast ATI 718Plus® is investigated by comparing 4 h and 24 h dwell time pseudo-hip homogenisation heat treatments at 1120, 1160 and 1190 °C with the as-cast microstructure. Scanning electron microscopy (SEM), X-ray diffraction (XRD) on electrolytically extracted powder and transmission electron microscopy (TEM) were used to identify Nb-rich secondary phases in interdendritic areas as the C14 Laves phase and Nb(Ti) MC-type carbides. All homogenisation heat treatments but the 1120 °C 4-h condition dissolve the Laves phase. A repair welding operation was simulated by linear groove multi-pass manual gas tungsten arc welding (GTAW). The Laves phase containing microstructures resulted in lower total crack length for heat affected zone cracking. Constitutional liquation of Nb(Ti) MC-type carbides is observed as a liquation mechanism in Laves-free microstructure, while thick liquid film formation due to the Laves eutectic melting could reduce the formation of weld cracks in microstructures containing the Laves phase.

Effect of deposition methods on microstructure and mechanical properties of Al 7075 alloy-rice husk ash surface composites using friction stir processing

In this study, friction stir processing (FSP) technique was used to fabricate rice husk ash (RHA) reinforced aluminum 7075 alloy (AA7075) surface composites (SCs). In which, deposition method of RHA into AA7075 substrate has been taken as a variable and its effects on microstructure, microhardness and tensile properties of resultant SCs were analyzed. The deposition methods used were- zigzag pattern surface blind holes, linear pattern surface blind holes and grooves pattern method. The microhardness increased in all methods AA7075/RHA SCs than base alloy. In particular, AA7075/RHA SCs by linear pattern surface blind holes method showed higher microhardness than other methods SCs and base alloy. The maximum microhardness of 604 HV obtained for SC processed with linear pattern blind holes method. However, tensile strength of all SCs were found lower than AA7075 alloy. Amongst SCs, zigzag blind holes method processed SCs exhibited higher tensile strength than others. Though SEM imaging confirmed good distribution of RHA particles, certain defects such as agglomeration of particles and tunnels were present within processed zone of SCs. The energy dispersive X-ray analysis (EDX) tests confirmed presence RHA particles in the form of silicon oxides (SiO2), aluminum oxides (Al2O3) etc. as constituents. Thus, AA7075/RHA SCs were fabricated successfully using FSP with increased microhardness properties, further optimization of FSP process parameters needed in order to avoid defects in the resultant materials.

Crohn’s disease with isolated gastric involvement as an example of a rare disease phenotype: a clinical case

Crohn's disease (CD), along with ulcerative colitis, is one of the predominant nosological forms of inflammatory bowel diseases. In CD, any part of the gastrointestinal tract can be affected; however, the process is commonly associated with terminal ileum or colon involvement. CD cases with isolated or mixed involvement of upper gastrointestinal tract (esophagus, stomach, and duodenum) are rare and least studied types of the disease. In isolated stomach involvement, the complaints are non-specific and include epigastric pain, gastric dyspepsia, early satiety, decreased appetite, and nausea. Isolated CD of upper gastrointestinal tract can be diagnosed after comprehensive work-up and always requires a high diagnostic level, including clinical, endoscopic and morphological one. We present a clinical case of CD with isolated stomach involvement in a 62-year-old woman. The diagnosis was confirmed by the histopathological findings of an epithelioid cell granuloma in the gastric antrum. Treatment with systemic corticosteroids reduced the disease clinical activity and improved the histological characteristics of the gastric biopsy sampled obtained by endoscopy. In this clinical case, there were specific macroscopic gastric lesions found at endoscopy in CD patients with upper gastrointestinal tract involvement, which is characterized by thickened longitudinal folding and linear grooves. This type of lesion has been described in the literature as “bamboo joint-like appearance”.Conclusion: Comprehensive assessment of clinical manifestations, endoscopic and histopathological specific features is crucial for the timely diagnosis and treatment of inflammatory bowel diseases.

Effect of novel hybrid texture tool on turning process performance in MQL machining of Inconel 718 superalloy

ABSTRACTHigher cutting zone temperatures are responsible for poor turning process performance during dry machining of Inconel 718 material. In the present work, a novel hybrid surface texture tool under minimum quantity lubrication (MQL) has been proposed to reduce the decremental effects that cause during machining of Inconel 718 material. Present work compared to the performance of three tools, namely, untextured tool (T1), texture tool having circular pit holes (T2) and hybrid texture tool combination of circular pit holes and linear grooves (T3) under MQL cooling technique. It was observed that hybrid texture tool (T3) significantly reduced the cutting zone temperature (Tm), tool flank wear (Vb) and surface roughness (Ra) to a maximum of 36%, 59% and 46%, respectively, when compared to the T1 tool whereas it was 22%, 48%, and 30% when compared to the T2 tool, respectively. The present work meets the stringent environmental regulation along with the improved machinability of Inconel 718 superalloy.

Evaluation of hybrid textured tool performance under minimum quantity lubrication while turning of AISI 304 steel

Nowadays, the surface texture of tool is an attractive machining technique due to the benefits in any chip removal machining process performance. However, surface texture design on texture tool plays a significant role in improving the turning process performance, in this context, a novel hybrid surface texture design has been proposed in the current work. The present work focused on the machinability improvement of AISI 304 material by employing the surface texture tool under minimum quantity lubrication (MQL) condition. In this work, comparative evaluation of turning performance has been carried out with a fabricated single texture tool which consists of circular pit holes pattern (T-1) and a fabricated novel hybrid texture tool combination of linear grooves and circular dimples (T-2), respectively, during machining of AISI 304 material at increasing cutting velocity condition. From the result, it was observed that the proposed hybrid texture tool (T-2) significantly reduced the cutting temperature (Tm), tool flank wear (Vb) and surface roughness (Ra) to a maximum of 26%, 31% and 34%, respectively, when compared to T-1. Further, low built-up edge (BUE) was found in T-2 tool over T-1, respectively.

Analytical and experimental investigations on the mechanisms of surface generation in micro grinding

Micro grinding is an emerging technology for producing structured surfaces on hard and brittle materials. A micro pencil grinding tool (MPGT) consists of a layer of superabrasive grits, bonded to a solid cylindrical surface. Randomly distributed and geometrically undefined grits interact with the workpiece surface at random positions. These random grit positions and protrusions lead to a difference in the size of undeformed chips. This study presents an analytical method to understand the undeformed chip geometry, that considers grit kinematics. Kinematic simulation of grit trajectory paths in longitudinal direction showed a reduced number of active grits in micro grinding with an increase in speed ratio and with reduced tool dimensions. MPGTs with different diameters, grit sizes, and planar grit densities have been used to perform the experiments on a 16MnCr5 hardened steel material. The influence of maximum radial height grits on surface generation in micro grinding has been verified experimentally for up and down grinding modes. Microscopic observations of ground surfaces have shown the distinct differences between up and down grinding modes, which are similar to the surface generation in milling processes. Moreover, the formation of linear grooves with uniform depth and width unlike conventional surface grinding at lower speed ratios indicated the influence of individual grits on surface generation. Trajectory path simulation results have also shown the same observation.

Structural Basis for Recruitment of DAPK1 to the KLHL20 E3 Ligase

SummaryBTB-Kelch proteins form the largest subfamily of Cullin-RING E3 ligases, yet their substrate complexes are mapped and structurally characterized only for KEAP1 and KLHL3. KLHL20 is a related CUL3-dependent ubiquitin ligase linked to autophagy, cancer, and Alzheimer's disease that promotes the ubiquitination and degradation of substrates including DAPK1, PML, and ULK1. We identified an “LPDLV”-containing motif in the DAPK1 death domain that determines its recruitment and degradation by KLHL20. A 1.1-Å crystal structure of a KLHL20 Kelch domain-DAPK1 peptide complex reveals DAPK1 binding as a loose helical turn that inserts deeply into the central pocket of the Kelch domain to contact all six blades of the β propeller. Here, KLHL20 forms salt-bridge and hydrophobic interactions including tryptophan and cysteine residues ideally positioned for covalent inhibitor development. The structure highlights the diverse binding modes of β-propeller domains versus linear grooves and suggests a new target for structure-based drug design.

Effect of interface surface design on the fracture behavior of bilayered composites.

This study aimed to evaluate the effect of different interface designs on the load‐bearing capacity of bilayered composite structures (BLS). Cylindrical specimens of BLS were prepared from base composite of 3.5 mm thickness and surface composite of 1.5 mm thickness (n = 80). Two different base composites – flowable bulk‐fill (FBF) [smart dentin replacement (SDR)] and short fiber‐reinforced (FRC) (everX Posterior) – were evaluated, and conventional composite (G‐ænial Posterior) was used as the surface layer. Four different interface designs were used: (i) pyramidal; (ii) mesh; (iii) linear grooves; and (iv) flat surface (control). Three‐dimensional printed molds were fabricated to standardize the interface design between the surface and the base composites. The specimens were then statically loaded with a steel ball until fracture using a universal testing machine. Fracture types were classified into catastrophic, complete, and partial bulk. anova revealed that both the material and the interface design had a statistically significant effect on the load‐bearing capacity. Flowable bulk‐fill showed lower mean load‐bearing capacity than FRC in all the interface designs tested, except for the flat surface design. Fracture analysis showed that FRC demonstrated up to 100% partial bulk fractures with the pyramid interface design, but no incidence of catastrophic bulk fracture. By contrast, FBF demonstrated up to 84.6% and 40% catastrophic bulk fractures with the flat interface design but no incidence of partial bulk fracture. Consequently, the interface designs studied enhanced the fracture behavior of BLS.

Research on the Improvement Effect and Mechanism of Micro-Scale Structures Treated by Laser Micro-Engraving on 7075 Al Alloy Tribological Properties.

During various applications in aerospace, ships, autos, and aircraft, 7075 Al alloy will frequently contact other materials, and therefore suffer from slight abrasion. However, the poor tribological properties of 7075 Al alloy greatly affect its performance and life length, leading to limitations in its application. Preparing roughness structures on the surface is regarded as a promising method to improve the properties of materials. However, the tribological properties of 7075 Al alloy cannot be enhanced significantly by roughness structures in complex dynamic changeable environments, owing to the incomplete understanding of the effect of roughness structures. Given the above issues, in this paper, micro-scale structures (linear grooves, gridding grooves, and arc grooves) were designed and prepared on 7075 Al alloy surfaces by a surface treatment (laser micro-engraving), which provides excellent controllability of the morphology and dimensions of as-prepared roughness structures. The tribological properties of the as-prepared surfaces were investigated systemically. The effect of micro-scale structures on the tribological properties was studied. The wear mechanism and tribological properties improvement mechanism of the surfaces were clarified. Furthermore, the effect degree of the enhancement factors of the micro-scale structures on the tribological properties was explored under different conditions. The results indicate that the micro-scale structures play an important role in improving the tribological properties of Al alloy under different sliding speeds. The improvement mechanism can be summarized by four factors. However, the effect degrees of these factors on the tribological properties exhibit considerable differences. This study not only develops specific micro-scale structures that can dramatically improve the tribological properties of 7075 Al alloy under different conditions, but also offers guidance for the construction of appropriate roughness structures that can dramatically improve the tribological properties of Al alloy according to the friction conditions.

Influence of tool path strategies on the residual stress development in single point incremental forming

Abstract The prevailing residual stress state in a formed metal component highly affects its mechanical properties. The single point incremental forming (SPIF) process allows a flexible adjustment of the process parameters during the forming process to influence the residual stress state. A selective induction of compressive residual stresses in the component can improve product properties, such as the fatigue strength. The effect of the dominant forming mechanisms on the residual stress state of the manufactured component is analyzed. Linear grooves are formed into aluminum alloy 5083 sheets and their resulting residual stress state is measured by means of X-ray diffraction (XRD). The grooves are manufactured in a multiple-stage process to ensure the transferability of the results to the incremental forming process of complex-shaped components. Different unidirectional and bidirectional tool path strategies were used to analyze the residual stress development. To set the dominant forming mechanism, the process parameter step-down increment Δz was adjusted, the other process parameters were kept constant. The dominant forming mechanisms were evaluated numerically. The results suggest that the influence of the tool path strategy on the resulting residual stress amplitude is unincisive. Distinctive residual stresses can be observed in bending-dominated regions. In case of shear domination, the resulting residual stress state is less pronounced.

Forming mechanisms-related residual stress development in single point incremental forming

The mechanical properties of a component are significantly influenced by the prevailing residual stress state. A deliberate induction of compressive residual stresses or a reduction of tensile residual stresses can improve the component properties, such as fatigue strength. Single point incremental forming is a flexible manufacturing process to produce complex shaped parts by the computerized numerically controlled movement of a hemispherical forming tool. Because the process parameters can be locally adjusted it is possible to influence the residual stress state of the component. The influence of the forming mechanisms bending, shearing and membrane stretching, as well as the role of the hydrostatic compression on the residual stress state is widely unknown. This work aims to fill this gap. Therefore, linear grooves are formed into AA5083 sheets in a single-stage incremental forming process. The residual stress state of the unclamped sheet is measured on both sides of the groove center by means of X-ray diffraction. The relative intensity of the dominant forming mechanism is adjusted by adapting the relevant process parameters step-down increment Δz and tool radius RTool. The forming mechanisms are analyzed numerically by splitting the total plastic energy into the three forming mechanisms bending, shearing and membrane stretching. The numerical results for bending and membrane stretching could be validated by crystallographic analysis. A shift in the energy ratio of the forming mechanism from bending to shearing with increasing relative step-down increment Δz/RTool could be observed numerically. The maximum residual stress amplitudes are found for Δz/RTool < 1. The results indicate that a deliberate residual stress state can be induced by adjusting the dominant forming mechanism of the process.

Influence of multiscale and curved structures on the migration of stem cells.

Understanding how topographical cues can control cell behavior is a major fundamental question which is of particular interest for implant design. Recent findings show that cell-scale curvature, as well as nanoscale topography, can affect different aspects of cell migration. However, the correlation between specific curvature radii and cell behavior, as well as the combinatorial effect of nanoscale topography and cell-scale curvature, has not yet been investigated. Herein, the authors employ a new femtosecond laser ablation method to generate multiscale topographical patterns directly on titanium surfaces. The process allows us to produce microgrooves of specific curvature imprinted with oriented nanotopographical features called Laser-Induced Periodic Surface Structures (LIPSS). The authors show that curved grooves stimulate the stem cell migration speed in comparison to flat or linear grooves. The fastest velocities are observed on 75 μm curvature radius, whereas cells migrating on 125 μm curvatures exhibit a lower speed similar to the ones migrating on straight lines. Double replicas of these grooves allow us to mask the LIPSS while keeping identical the cell-scale pattern, therefore permitting to uncouple the effect of nanoscale and microscale topographies. The authors found that the presence of nanoscale topographies improves the reading of microgrooves curvature by cells. Altogether, this work shows that the combination of specific curvatures together with nanopatterning can control the velocity of migrating stem cells and promote the use of femtosecond laser ablation in the context of surface implant design.

Study on the surface quality of CFRP machined by micro-textured milling tools

Commonly known the carbon fiber reinforced plastics (CFRP) is easy to produce burr, avulsion (tear), delamination and other defects in traditional milling process. Changing the contact characteristics of tool-chip interface can be used to improve the cutting process, which may be achieved by surface texturing of the tools. Thus, two kinds of surface structures were fabricated on the rake face of the carbide double-edge milling tool: (1) linear grooves parallel to the main cutting edge (named PAM); (2) linear grooves perpendicular to the main cutting edge (named PEM). Dry cutting tests were carried out on unidirectional laminated CFRP with different fiber orientations (0°, 45°, 90° and 135°) using the two developed tools and the conventional tool (named NCM). Thesurface quality of machined workpieces was assessed in terms of the surface roughness, burr, tear phenomenon and the way of fiber breakage. Results show that the surface quality of CFRP machined by the micro-textured milling tools is improved over that by the conventional one. Meanwhile, the types of surface texture and fiber laying have a profound effect on the surface quality of machined part. In this experiments, the linear grooves parallel to the main cutting edge is more effective in reducing the burr length, bending deformation of fiber chip and the tearing phenomenon of machined surface. The possible mechanisms for the effects of micro-textures on the surface quality of machined CFRP were revealed.

Nanoimprinted Anisotropic Topography Preferentially Guides Axons and Enhances Nerve Regeneration

Surface topography has a profound effect on the development of the nervous system, such as neuronal differentiation and morphogenesis. While the interaction of neurons and the surface topography of their local environment is well characterized, the neuron-topography interaction during the regeneration process remains largely unknown. To address this question, an anisotropic surface topography resembling linear grooves made from poly(ethylene-vinyl acetate) (EVA), a soft and biocompatible polymer, using nanoimprinting, is established. It is found that neurons from both the central and peripheral nervous system can survive and grow on this grooved surface. Additionally, it is observed that axons but not dendrites specifically align with these grooves. Furthermore, it is demonstrated that neurons on the grooved surface are capable of regeneration after an on-site injury. More importantly, these injured neurons have an accelerated and enhanced regeneration. Together, the data demonstrate that this anisotropic topography guides axon growth and improves axon regeneration. This opens up the possibility to study the effect of surface topography on regenerating axons and has the potential to be developed into a medical device for treating peripheral nerve injuries.

Axial buckling modes and crashworthiness of circular tube with external linear gradient grooves

Metallic circular tube with external uniform grooves has excellent behaviors on axial crashworthiness during axial compression because it can generate stable responses. In the present research, three novel energy absorbers are proposed based on uniform grooved tube (UGT), namely, depth gradient grooved tube (D-GGT), thickness gradient grooved tube (T-GGT) and coupling gradient grooved tube (C-GGT). A theoretical model considering both the depth and thickness gradients and an efficient numerical model based on axisymmetric assumption are put forward. Meanwhile, some quasi-static compression experiments are performed to validate the theoretical and numerical models. The results conclude that the deformation of gradient grooved tubes (GGTs) under axial buckling can be classified into two modes, namely, random asymptotic buckling (RAB) and sequential asymptotic buckling (SAB). Compared with UGT, the D-GGT has a slight improvement on the axial energy performance even though the sum of depth of thin-walled sections is constant; for T-GGT, a force-displacement curve with upward trend and an obvious improvement of energy absorption are observed; specially, the energy absorption characteristics of D-GGT and T-GGT will occur simultaneously when C-GGT is subjected to axial loading.

Polarization-resolved second-harmonic-generation imaging of dermal collagen fiber in prewrinkled and wrinkled skins of ultraviolet-B-exposed mouse.

.Skin wrinkling is a typical symptom of cutaneous photoaging; however, the skin wrinkling depends on not only the actual age but also exposure history to ultraviolet B (UVB) rays in individuals. Therefore, there is considerable need for its assessment technique in vivo in skin cosmetics and antiaging dermatology. Wrinkles always appear as linear grooves in the skin, and dermal collagen fibers play an important role to determine the morphology and mechanical properties of the skin. Therefore, an optical probe sensitive to dermal collagen fiber and its orientation will be useful. Polarization-resolved second-harmonic-generation (SHG) microscopy is a promising approach for in vivo evaluation of collagen fiber orientation because the efficiency of SHG light is sensitive to collagen fiber orientation when the incident light is linearly polarized. We investigate orientation change of dermal collagen fiber in prewrinkled and wrinkled skins of the UVB-exposed mouse model using polarization-resolved SHG microscopy. A polarization anisotropic image of the SHG light indicates that the change of collagen fiber orientation starts in the prewrinkled skin of UVB-exposed mice, then the wrinkle appears. Furthermore, the dominant direction of collagen fiber orientation in the prewrinkled skin is significantly parallel to the wrinkle direction in the wrinkled skin. This result implies that the change of collagen fiber orientation is a trigger of wrinkling in cutaneous photoaging.