Straight Edge Research Articles

Fem Analysis of Progressive Failure for Composite Hypar Shells

The finite element method is used to to study progressive failure aspects of laminar composite skewed hypar shells with straight edges employing the eight-node isoparametric element in linear and elastic ranges under uniformly distributed static loading. A stiffness decrease scheme is proposed in which the stiffness properties of the failed element are gradually reduced resulting in redistribution of eveloping stresses on the extent of damage it accumulates. Specific numerical problems of earlier investigators are solved to validate the present approach. Numerical experiments are further carried out for different parametric variations, including some complicated boundary conditions and stacking orders of practical importance to obtain the first ply and progressive failure loads. Well accepted failure criteria are used to evaluate the failure loads and its development. Progressive failure in hypar shells are examined to arrive at some conclusions useful to the practicing engineers regarding tailoring guidelines of laminar composites and planning of nondestructive test programs for their health monitoring.

Sold out or bought in? Complexities of the X Swatch as subcultural accessory for the straight edge scene

This research explores lifestyle consumerism and inquires into a subcultural community’s use of a mainstream fashion object to express alternative values. The ‘X-rated Swatch Watch’ is extremely popular within straight edge, a clean-living punk offshoot in which participants abstain from alcohol, tobacco and illicit drugs. Swatch first released the watch in 1987 with a black band and white face featuring a large black ‘X’, a prominent symbol in the straight edge scene visible on clothing, in tattoos and drawn on hands. The limited-edition watch became highly collectable on the second-hand market and was re-released by Swatch in 2018 with design changes, including larger size and more colour options. The first and second incarnations of the watch, as well as knockoffs, indicate aesthetic trends in the fashion cycle, evolutions as well as stagnations in subcultural individual and community expression, and the complexities of a mass market item that has multiple cultural meanings within the same time period. In this article, we use qualitative mixed methods to explore the significance of the watch for United States straight edgers who own or express interest in the watch. Primary data collection included surveys, social media discussions, participant observation and archive visits. Results indicate that wearers utilize this watch to strengthen their straight edge identity and communal connections to similar individuals and to the historic lineage of their lifestyle. X Swatch consumers are not overly concerned with the duality of subcultural and mainstream meanings as they compartmentalize their community from wider society.

Sawtooth Carrier-Based PWM Methods With Common-Mode Voltage Reduction for Symmetrical Multiphase Two-Level Inverters With Odd Phase Number

The increased phase number of multiphase systems enables us to exploit more degrees of freedom, such as the shape of phase carriers in pulsewidth modulation (PWM). The sawtooth carrier-based PWM (SCPWM) techniques are proposed in this article to reduce common-mode voltage (CMV) in both the peak-to-peak amplitude and the changing frequency, and it can be easily extended to symmetrical multiphase two-level inverters with any odd phase number. Theoretical analysis reveals that the switching between mirror-symmetrical carriers within one phase narrows the range of the sum of switching states in all phases, which leads to the reduction of CMV amplitude. Meanwhile, the overlapping of sawtooth carriers' straight edges among different phases slows down the change of the sum of switching states, which results in the decrease of CMV changing frequency. Moreover, the effects of voltage harmonics injection and switches' dead-time settings on the CMV reduction performance under the proposed SCPWM techniques are investigated. Finally, the experiment results in a five-phase induction machine and multiphase RL loads verify the improved CMV performance and the extensibility of the proposed SCPWM methods.

I want something new: Limp Records and the birth of DC punk, 1976–80

Recountings of the Washington, DC punk rock scene’s history often start with the founding of Dischord Records in 1980 and focus on the subsequent ascent of Dischord co-owner Ian MacKaye’s bands like Minor Threat and Fugazi. As seminal as Dischord remains in the narrative of DC punk – a community still thriving today – the years just prior to the label’s founding generated the scene’s true incunabula. Beginning with the self-released debut EP from the Slickee Boys in 1976, this first wave of DC bands – also including Razz, Nurses, White Boy and others – combined elements of art rock, surf, proto-punk, pub rock and power pop together to craft a protean version of punk that embraced eccentricity and humour, serving as the city’s own defiant rebuke of the staid state of 1970s rock music. No record label was more central to the nascent punk scene in DC than Limp Records. Operated by Skip Groff, Limp provided the punk community with its first proper record label. Rather than a label that centred around the efforts of a single band – as most other new DC punk labels did – Limp issued singles for several groups, collaborating with the fledgling Dacoit and O’Rourke labels to co-release defining singles for the Slickee Boys and Razz. DC punk would not have taken shape the way it did without Groff’s efforts, particularly considering his connections with bands like Bad Brains and the Slickee Boys and his musical and entrepreneurial influence on local teenage punks like MacKaye, Jeff Nelson and Henry Rollins. This article is a history of DC punk record labels from 1976 to 1980 and seeks to establish this overshadowed era of the scene as one of the most critical in the community’s 43-year existence. Considering the outsize influence the DC scene ultimately had on punk culture – whether through the eponymous clean living philosophy inspired by the Minor Threat song ‘Straight Edge’, the unwaveringly independent business model of Dischord or the pacesetting music reliably turned out each decade by participants in the scene – the impact of Groff and his first wave DC punk peers must be acknowledged.

Application of an industrial robot for processing the edges of parts

The possibility of using a robotic complex when machining the edges of parts with solid polymer-abrasive radial brushes is studied. The dependences of the parameters of the machined edge and the roughness of the machined surface on the cutting speed, brush deformation, feed and the angle of inclination of the tool relative to the machined surface are determined. The possibility of processing the edges along the outer radius, in the oval hole, straight edges in the groove and on inclined sections is shown. Keywords edge, processing, robotic complex, polymer-abrasive brush, mode parameters. Dimov-Ura@yandex.ru

Edge plasmon-polaritons on isotropic semi-infinite conducting sheets

From a three-dimensional boundary value problem for the time harmonic classical Maxwell equations, we derive the dispersion relation for a surface wave, the edge plasmon-polariton (EP), which is localized near and propagates along the straight edge of a planar, semi-infinite sheet with a spatially homogeneous, scalar conductivity. The sheet lies in a uniform and isotropic medium and serves as a model for some two-dimensional (2D) conducting materials such as the doped monolayer graphene. We formulate a homogeneous system of integral equations for the electric field tangential to the plane of the sheet. By the Wiener–Hopf method, we convert this system to coupled functional equations on the real line for the Fourier transforms of the fields in the surface coordinate normal to the edge and solve these equations exactly. The derived EP dispersion relation smoothly connects two regimes: a low-frequency regime, where the EP wave number, q, can be comparable to the propagation constant, k0, of the ambient medium, and the nonretarded frequency regime in which |q| ≫ |k0|. Our analysis indicates two types of 2D surface plasmon-polaritons on the sheet away from the edge. We extend the formalism to the geometry of two coplanar sheets.

Density functional calculations for structures and energetics of atomic steps and their implication for surface morphology on Si-face SiC polar surfaces

We perform large-scale density-functional calculations using the real-space finite-difference scheme endorsed by the Gordon Bell prize in 2011 that reveal detailed atomic and electronic structures of atomic steps on silicon carbide (SiC) polar surfaces for the first time. The accurate structural optimization elucidates characteristic atomic reconstruction among the upper and lower edge atoms, which is peculiar to compound semiconductors having both covalent and ionic nature. The calculated formation energies of all the possible atomic steps lead us to unequivocally identify the abundant atomic steps on the Si-face SiC polar surfaces. The energetics thus obtained for the atomic steps provides a natural and persuasive microscopic reason for the difference in the step morphology observed experimentally, i.e., the meandering and straight step edges depending on the inclined direction on the polar vicinal SiC surfaces. Electron states caused by those atomic steps are also calculated, which assists in the identification of the atomic steps by future experiments.

Symmetric Free Form Building Structures Arranged Regularly on Smooth Surfaces with Polyhedral Nets

The article is an original insight into interdisciplinary challenges of shaping innovative unconventional complex free form buildings roofed with multi-segment shell structures arranged with using novel parametric regular networks. The roof structures are made up of nominally plane thin-walled folded steel sheets transformed elastically and rationally into spatial shapes. A method is presented for creating such symmetric structures based on the regular spatial polyhedral networks created as a result of a composition of many complete reference tetrahedrons by their common flat sides and straight side edges arranged regularly and symmetrically in the three-dimensional Euclidean space. The use of the regularity and symmetry in the process of shaping different forms of (a) single tetrahedral meshes and whole consistent polyhedral structures, (b) individual plane walls and complex elevations, (c) single transformed folds, entire corrugated shell roofs, and their structures allow a creative search for attractive rational parametric solutions using a few author’s parametric algorithms and their implementation as built-in commands of the AutoCAD visual editor or applications of the Rhino/Grasshopper program.

Numerical investigation on thermal hydraulic performance of supercritical LNG in sinusoidal wavy channel based printed circuit vaporizer

As a new type of micro-channel heat exchange, printed circuit heat exchanger (PCHE) is a better choice as main cryogenic heat exchanger (MCHE) on LNG carriers and LNG floating terminals for high efficiency and compactness. In this work, a 3D-numerical model of PCHE employing SST k-ω turbulent model is built after validating against the classic experimental data of supercritical fluid. The cross section of S-LNG channel is a semi-circle with radius of 0.9 mm, size of solid region (stainless steel) is 2.15 mm × 1.6 mm, the overall length of the channel is 500 mm and the centerline formula of the channel is z = 0.5∙sin(0.5∙x). Based on this model, the thermal hydraulic performance of supercritical LNG (S-LNG) in sinusoidal wavy channel of printed circuit vaporizer (PCV) is investigated, and the effects of heat flux and operation pressure on flow and heat transfer are analyzed, which aim to improve the understanding of flow and heat transfer mechanism of S-LNG in sinusoidal wavy semi-circuit channel. Moreover, the simulation result indicates that the maximum gap of heat transfer coefficient between adjacent observation cross section can reach 1.28 kW·m−2·K−1, and the effect of buoyancy force is not domination on heat transfer; the reverse flow occurs nearly in every periodic segment, and the flowing “dead zone” and vortex appear close to the inner wall of cross section, especially near the region of included angle between the straight edge and the semi-circle curve; the lower intensity of both turbulent structure rebuilding and secondary flow appears under higher operating pressure, and after passing large specific heat region, the effect of operating pressure is inappreciable.

Uniform motion of an edge dislocation within Mindlin’s first strain gradient elasticity

Motion of dislocations plays the fundamental role in plastic deformations of crystalline solids. According to the prediction of classical elasticity, the strain and stress fields due to a moving dislocation suffer from singularities. In the present paper, it is shown that the employment of Mindlin’s first strain gradient theory of elasticity leads to the removal of the singularities from all the elastic fields induced by a straight edge dislocation that moves uniformly in an infinitely extended isotropic body. However, at distances far enough away from the dislocation core, the predictions of such theory and classical elasticity coincide with each other. The present analysis also shows that the corresponding plastic strain field of the moving dislocation is, likewise, free from any singularity. Moreover, explanations are provided in the current paper for the roles of the micro-inertia and the characteristic lengths of the constituent material of the body as well as the effect of the velocity of the dislocation on its induced field quantities.

Robust composite sine-trapezoidal phase-shifting algorithm for nonlinear intensity

Phase-shifting profilometry (PSP) is an efficient three-dimensional (3D) measurement technique. The accuracy of the PSP based 3D measurement system is generally affected by the nonlinear intensity response of the projector. In general, nonlinear errors can be reduced by projecting more fringe patterns, but this approach significantly increases the measuring time. To improve the measurement accuracy and speed, a new composite sine-trapezoidal phase-shifting profilometry technique that suppresses nonlinear error is proposed in this study. The main idea of the proposed method is projecting a set of sinusoidal fringe patterns and two sets of composite sine-trapezoidal fringe patterns with different intensity ranges in sequence. Among these patterns, the sinusoidal fringe is used to encode the pixel position, and the order of the wrapping phase is determined by the region code of the composite fringe. The flat intensity parts of the composite fringe are used to encode the nonlinear intensity response of the measurement system. Through system identification, the response parameters of the pixels can be obtained, and the gray value of the pixels can be corrected to gain a better phase distribution. Compared to the straight edges of the trapezoidal fringe, the sinusoidal edges of the composite fringe are more robust to the projector defocus, which improves the accuracy of the identification of the system intensity response model. Simulation results show that the proposed method can achieve a higher phase retrieval accuracy than the trapezoidal PSP and the sine PSP. The experiment results indicate that the proposed method has a better measurement accuracy than those of the standard 3-step and 4-step sine PSP methods.

Tension failure analysis for bolted joints using a closed-form stress solution

Bolted joints are widely used to connect safety-critical parts in the aeronautical industry and require precise structural assessment tools. Focus of this paper is the development of an overall analytical calculation method to determine the stresses of a bolted joint with quasi-isotropic composite material, which is then used in a tension failure analysis. The stress solution is obtained by means of the Airy stress function. To predict crack initiation in the tension failure analysis use is made of the Theory of Critical Distances. Crack initiation occurs in the net section plane and its assessment requires precisely calculated net section stresses. For this purpose, the stress boundary conditions in load direction at the straight free edges must be fulfilled, which is reached by supplementing the field modelling the load introduction with auxiliary functions. This technique is a physically motivated means to deal with symmetric finite geometry problems involving straight free edges. However stress boundary conditions perpendicular to the load direction are not covered and some inaccuracies in the stress solution may arise. A failure analysis is conducted to investigate their impact on the predicted failure load using literature values based on Finite Fracture Mechanics as reference.

Detection of Damaged Stop Lines on Public Roads by Focusing on Piece Distribution of Paired Edges

In this study, a system for detecting stop lines on roads with damaged paint is developed to enhance a digital map localization system. Existing methods to detect stop lines focus on features such as straight edges and adequate size; however, these methods are not suitable to be used in rural areas because the paint of stop lines on the roads is damaged sometimes. In addition, lane marks, which are focused on by other existing methods, are often not present on actual roads in rural areas. Thus, to enable the detection of stop lines in the absence of conditions necessary for using the abovementioned features, we focus on pieces of faint features of damaged stop lines. First, we extract the positive and negative edges from an inverse perspective mapped image of the camera input by using a Sobel filter. Next, we verify the pairs of positive and negative edges from the trinarized edge image by confirming the width between both edges. Subsequently, we detect the candidates of stop lines by analyzing the distribution of the line segments extracted by the Hough transformation. In addition, we combine the data of the estimated driving distance and the result of detection of the preceding vehicles with the proposed system to prevent false detections in terms of bicycle crossing lanes and preceding vehicles. The damaged stop lines are detected eventually using these processes. To evaluate the performance of the proposed method, we collect driving data on actual public roads. The results of offline evaluations confirm that the proposed system can detect all target stop lines without any false detections, at a reasonable speed. The findings of this study are expected to contribute to the realization of intelligent vehicles on community roads.

Picosecond laser ablation of high-quality micro-grooves on CIGS (CuIn(1-x)Ga2Se x ) thin films

ABSTRACT This paper presents a study of the effects of ablation direction, beam profile and outer environment on the width and morphology of micro-grooves ablated by a 10-ps, 532-nm laser with a changing range of fluences and scan speeds on 600 nm-thick CIGS (CuIn(1-x)Ga2Se x ) thin films. Experiments show that rear-side ablation by picosecond laser with a flat top beam in water environment yields a larger groove width than normal front-side ablation with a Gaussian beam in air, which is attributed to different material removal mechanisms, uniform energy distribution and the refraction of laser in water. The heat-affected zone and irregular edges induced by the tearing effect are the main defects of groove morphology associated with front- and rear-side ablation processes, respectively. Our studies indicate that flat top beam ablation, in general, inhibits the over-ablation in the central region, thereby improving the uniformity of grooves, though it does not eliminate the heat-affected zone and irregularity of two edges. The straightness of groove edges is further improved with the flat top beam ablation carried out in a water environment, resulting from the action of the shock wave in water. Hence, the nearly perfect micro-grooves can be fabricated with rear-side flat top beam ablation under water, which are characterized by steep sidewalls, straight edges and intact glass substrate without cracks.

Deformation behavior in multi-point forming using a strip steel pad

The blank is prone to wrinkles and spring-back in multi-point forming, seriously affecting the quality and forming accuracy of the formed part. To improve this state, a sandwich structure constructed from a strip steel pad and blank was presented. The deformation behaviour and forming accuracy using three forming processes, namely, without a cushion, using a polyurethane elastic pad and using a strip steel pad, were analysed by numerical simulation and experimentation. The results showed that the use of the strip steel pad in multi-point forming can effectively increase the deformation resistance of the sheet bending; make the material evenly thinned during forming; suppress defects such as wrinkles, spring-back, dimples and straight edges; and improve the forming accuracy.

Influence of outlet orientation and variable tube length on high temperature zones of U‐tube trisection helical baffle electric heaters

AbstractNumerical simulation was performed to optimize temperature distribution especially at high temperature zones at the rear part of U‐tube bundle electric heaters with unique one‐plus‐two U‐tube layouts. The influences of variable tube lengths and different outlet nozzle orientations on flow and thermal features on axial separation trisection helical baffle schemes in contrast to segmental schemes were investigated. The results show that the variable tube length schemes can effectively ameliorate high temperature zones and obtain more uniform temperature fields. The mean heat transfer coefficient, h.t.c., and tube wall temperature, Tw, of the variable tube length scheme HV15(10)°‐180° are respectively 0.7% higher and 3.1 K lower than those of the normal scheme H15(10)°‐180°. The optimal relative position of the outlet and tube bundle for helical schemes is that the outlet axis is not only tangent to the last straight edge of the baffle but is also on the side near it, while the optimum outlet angle for the segmental scheme is 90° within the research scope. Compared with segmental scheme S200‐90°, the averaged heat transfer coefficients, h.t.c.s, and comprehensive indexes, h · Δp−1/3, of the helical baffle schemes HV15(10)°‐180°/HV15(10)°‐Ax respectively rise by 14.6/11.8% and 16.1/13.8%, while the average Tw declines by 40.7/33.3 K.

Two-step method to improve geometry accuracy of elongated hole flanging by electromagnetic forming

Electromagnetic forming (EMF) was used to conduct elongated hole flanging in this work. The investigation showed that the low geometry accuracy around the elongated hole flanging attributed from an uncoordinated deformation occurred, including unequal flanging heights and different rebound amounts between the straight edges and the circular edges. The uncoordinated flanging height resulted from different strain distribution. The strain distribution of the circular edges was similar to circular hole flanging, while the strain distribution of the straight edge regions was similar to sheet stretch bending. The uncoordinated rebound amount resulted from different deformation mechanisms, stress distribution, and structural stiffness within the forming regions. To improve the geometry accuracy of the elongated hole flanging, a two-step method combined geometric compensation electromagnetic forming (GC-EMF) and electromagnetic calibration (EM calibration) was proposed. GC-EMF was used to achieve equal flanging height by optimizing the prefabricated hole, while EM calibration after GC-EMF was used to improve the forming accuracy by reducing the amount of rebound. The difference in the flanging heights between the straight edges and the circular edges was only 0.1 mm after the GC-EMF process, when the compensation dimension on both sides of the straight edges of a prefabricated hole was 3.4 mm. The gap between the die and the straight edges was 0.2 mm, the gap between the die and the circular edges was 0.1 mm, after EM calibration. Therefore, the improved geometry accuracy of the elongated hole flanging was achieved by combining the GC-EMF with EM calibration. The results obtained and the method proposed in this work present significant guidance for the process of elongated hole flanging or other irregular hole flanging by EMF.

Conceptualization, development and design of a mortar spraying machine

Abstract Wall plastering is a laborious and often time-consuming process for the construction industry. Mortar spraying is the rendering of mortar at high velocity to achieve compaction and placement at the same time. This research aimed at conceptualizing various options, leading to the development, design and fabrication of a semi-automated machine to reduce the amount of time taken in plastering. A mortar spaying machine was designed, manufactured and tested, using locally available materials. It improved the surface finish and protected the wall from moisture weakening the structure. In an effort to identify a gap locally, a survey was also conducted in Harare, Zimbabwe through timing different builders whilst plastering. The survey revealed that the use of a trowel can cover an average of 5m2/hour. However, with the mortar spraying machine, an area of 30m2/hour can be covered. The mortar spraying machine was fabricated from light materials and weighed just below 20kg, making it flexible and mobile with the addition of poly-wheels. Pre- mixed wet mortar was placed into the hopper and stirred by a conveying screw, driven by a power drill. After rendering, a straight edge was used to level the sprayed mortar. The mortar spraying machine had a maximum volume flow rate of 10l/min. The set-up was designed to reduce the power consumed since most of the material flowed by gravity. The machine had a simple layout and minimal parts to accomplish the mechanization of plastering. The design has managed to bring many positive attributes to the construction sector such as, reduced lead time to provision of houses, ergonomics, reduced labour costs and quality product in terms of consistence and compaction of plastering compared to the manual method.

Alternative Bi precursor effects on the structural, optical, morphological and photocatalytic properties of BiOI nanostructures

BiOI nanostructures were synthetized through a hydrothermal process using either bismuth acetate or subsalicylate as Bi precursor. Regardless of the used Bi source, the same crystalline structure of BiOI was obtained; nevertheless, the nature of the Bi precursor had an evident impact in the color appearance of the obtained sample. Another notable difference was observed in the resulting morphology, where ∼1.6 μm flower- and dandelion-like shapes were obtained for acetate and subsalicylate, respectively; both structures assembled by around 30 nm thick nanoflakes with rounded and straight edge, respectively. UV–vis diffuse reflectance shows an energy gap around 1.8 eV. Raman spectroscopy confirms also the tetragonal phase of BiOI. The photocatalytic activity was evaluated through degradation of methyl orange dye using visible and UV light sources, comparing results with P25 TiO2. Both BiOI nanostructures presented an improvement of photocatalytic activity when irradiated with visible light, having the best photoactivity the sample synthetized with bismuth acetate.

A review of chamfer technology in continuous casting process

Chamfer technology, with funnel-shaped curved surface on the narrow side of the mold, is a novel technology that can effectively improve the quality of continuously cast products. This study reviews the available literature on the theoretical and applied research in chamfer technology to provide an in depth analysis of the employed approaches and the obtained results. According to theoretical research results, combined with the working conditions of slab caster, patented technologies and related equipment were developed. The research has broken the technology bottlenecks of the industrial application, while ensuring a long-life operation of the chamfer mold. In recent years, chamfer technology, which is used in slab casting processes, can prevent transverse corner cracks to form at the slab surface of micro-alloyed steel completely. Chamfer technology, which is used in thin slab casting processes, can reduce the occurrence of longitudinal surface crack of the slabs and straight edge seam defects of the rolled strip. In addition, chamfer technology, which is used in a continuous casting bloom, can reduce the risk of internal cracks and avoid the off-corner cracks occurring in as-cast bloom.