Edge Damage Research Articles

Numerical modelling of shear cutting using particle methods

The use of Advanced High Strength Steel (AHSS) allows for lightweighting of sheet steel components, with maintained structural integrity of the part. However, AHSS grades show limitations in edge crack resistance, primarily influenced by sheared edge damage introduced by the shear cutting process. Numerical modelling of the shear cutting process can aid the understanding of the sheared edge damage, thus avoiding unforeseen edge cracking in the subsequent cold forming. However, the extreme deformations of the blank during the shear cutting process are likely to cause numerical instabilities and divergence using conventional Finite Element modelling. To overcome these challenges, this work presents the use of a particle-based numerical modelling method called the Particle Finite Element Method (PFEM). PFEM accurately solves some of the challenges encountered in shear cutting with the standard Finite Element method, such as large deformation, angular distortions, generation of new boundaries and presents an efficient way of transfer historical information from the old to the new mesh, minimising the results diffusion. The present work shows prediction of cut edge morphology of AHSS using a PFEM modelling scheme, where the numerical results are verified against experiments. With these results, the authors show new possibilities to obtain accurate numerical prediction of the shear cutting process, which promotes further advances in prediction of edge damaged related to shear cutting of AHSS.

Influence of Cutting Process on the Flanging Formability of the Cut Edge for DP980 Steel

Flanging is a key process in the forming of automobile parts and is influenced by the cutting process before it. In this paper, a set of self-designed tools is adopted. The flanging height and flanging radius are specified as the indexes to investigate the influence of the cutting process on the flanging formability of DP980 steel. Microstructure, microhardness, and tensile properties are tested to evaluate the formability of cut edges. The results show that the flanging formability is positively correlated with an increase in flanging height and a decrease in flanging radius. The flanging formability of six cut edges can be ranked as: LC-L > LC-H > WEDM-HS > WEDM-LS > CNC milling > WJC. In the LC process, acicular martensite is formed and the microhardness of the cut edge significantly increases, with a heat-affected zone of about 150 μm. More and larger microvoids are found on the edge of WEDM-LS than WEDM-HS, which reduces the formability to a certain extent. Plastic deformation of the edges is the reason for the decrease in the formability of CNC milling. For WJC, the formation of irregular edge damage and the generation of burrs are the main reasons for the unstable performance. This research is helpful in guiding the selection of the cutting process, and it may contribute to a high part formability for DP980 steel.

Research on the stress intensity factor of crack on the finite width plate with edge damage based on the finite element method

In aircraft structure maintenance, when we remove edge cracks of some structures, such as aircraft skin, or frame edges, the removal depth and radius affect the stress intensity factor of the crack tip, thereby affecting the service life of the structure. In this paper, we use the finite element method to calculate the crack stress intensity factor of the finite width plate and compare it with the engineering analysis method, which proves the effectiveness of the finite element method. We further research the influence of the crack stress intensity factor with different edge damage depths and radii of the finite width plate, which will provide a reference for aircraft structure edge damage tolerance analysis in engineering.

Rendered Tile Reuse Scheme Based on FoV Prediction for MEC-Assisted Wireless VR Service

Interactive real-time wireless Virtual Reality (VR) has become increasingly popular because it provides an immersive experience for VR users anytime, anywhere. Introducing multi-access edge computing (MEC) to wireless VR service can solve the problem that VR devices having insufficient rendering power. However, the problem that some tiles in the overlapping field of views (FoVs) may be rendered repeatedly usually be ignored. Repeated rendering would waste the computing resources of edge nodes and damage users' quality of experience (QoE). This paper proposes a rendered tile reuse scheme based on FoV prediction and 3 C (caching, computing, and communication) optimization for the MEC-assisted VR service. Firstly, we model the above scheme as an optimization problem that aims to maximize the total users' QoE value under the motion to photons (MTP) delay constraints. Secondly, we use the recurrent neural network model with gated recurrent unit (GRU) architecture to dynamically predict the users' FoV in the next time slot. Thirdly, we use the proximal policy optimization (PPO)to learn the question's solution iteratively based on the results of FoV prediction. The simulation results show that our proposed algorithm is superior to other algorithms in improving the value of total users' QoE and reducing the MTP delay.

Wind tunnel test of airfoil with erosion and leading edge protection

This paper describes wind tunnel tests of a NACA 633 – 418 airfoil with erosion and leading edge protection. Measurements are carried out at high Reynolds number (Re = 5 million) representing modern wind turbines. Three examples of deviations from the perfect airfoil surface are shown. It is seen how the presence of a roughness mesh degrades the aerodynamics and that the presence of the mesh is more important than the actual topology of the mesh. That is also the case for the stall strips where a small strip influences the performance slightly less than a big stall strip, but the presence of the stall strip alone is influencing the performance significantly. Finally, a simulated leading edge protection (LEP), represented by a sheet of paper, can influence the performance significantly as the paper leads to a backward facing step. Furthermore, the measurements showed that correct mounting of LEP is important to avoid too big losses in aerodynamic performance. Investigating the impact of reduced airfoil performance for the rotor performance showed losses in annual energy production of between 0.3% and 4.0%. All in all the wind tunnel tests reflected that leading edge damages have a significant impact on the aerodynamic performance.

On the influence of edge damage on thermally induced buckling of stepped circular bi-laminates

The influence of edge damage on thermo-mechanical buckling of stepped circular bi-laminates is examined analytically. The nonlinear equations of equilibrium, the associated boundary conditions and the transversality conditions for the propagating interior boundaries of a region of sliding contact are derived via the Principal of Stationary Potential Energy as a propagating boundary problem in the calculus of variations. The problem is ultimately recast in a mixed formulation expressed in terms of the membrane forces and the transverse displacements of the composite structure. A loading parameter is identified and closed form analytical solutions to the resulting non-linear problem are determined. In addition, a stability criterion is established based on the second variation of the total potential energy of the structure, and qualitative behavior concerning contact is deduced analytically. Results of numerical simulations based on the analytical solutions established herein are generated and the phenomenon of “sling-shot buckling” is observed, whereby the structure first deflects in one direction upon heating (or cooling) and then, when a critical temperature is achieved, dynamically “sling-shots” from the current equilibrium configuration to an alternate equilibrium configuration possessing deflections in the opposite sense. In addition, the phenomenon of “buckle-trapping” is observed for stepped circular bi-laminates with hinged-fixed supports, as well as for clamped-fixed structures with relatively large damaged area. A robust mixture of contact behavior, including propagating sliding contact, edge contact and no contact, and the transition from one form of contact to another, is exhibited for both pre-buckling and post-buckling configurations. The influence of edge damage on critical load and characteristic behavior is assessed.

Spin-Wave Optics in YIG Realized by Ion-Beam Irradiation.

Direct focused-ion-beam writing is presented as an enabling technology for realizing functional spin-wave devices of high complexity, and demonstrate its potential by optically-inspired designs. It is shown that ion-beam irradiation changes the characteristics of yttrium iron garnet films on a submicron scale in a highly controlled way, allowing one to engineer the magnonic index of refraction adapted to desired applications. This technique does not physically remove material, and allows rapid fabrication of high-quality architectures of modified magnetization in magnonic media with minimal edge damage (compared to more common removal techniques such as etching or milling). By experimentally showing magnonic versions of a number of optical devices (lenses, gratings, Fourier-domain processors) this technology is envisioned as the gateway to building magnonic computing devices that rival their optical counterparts in their complexity and computational power.

Investigation on a sustainable composite method of glass microstructures fabrication—Electrochemical discharge milling and grinding (ECDM-G)

Glass structures with microchannel morphology play an important role in the fields of biology, medicine and MEMS. The non-traditional machining methods currently used to machining glass have problems such as excessive energy consumption, poor sustainability, and harmful to operators and the environment. To achieve precision, efficient, green, sustainable production and save resources, a novel composite machining method of electrochemical discharge milling and grinding (ECDM-G) was proposed in this paper. Compared with tranditional electrochemical discharge machining, lower discharge energy is applied, and KH2PO4 solution is used as electrolyte instead of alkaline solution, thus realizing energy-saving and green machining. Compared with mechanical grinding, tool wear is reduced and the sustainability of machining is improved. In the theoretical part, the heat conduction process of electrochemical discharge was simulated and the softening effect of workpiece material was analyzed. Furthermore, the matching mathematical model between electrochemical discharge energy and material removal by grinding was established. So as to accurately control the energy and avoid waste. In the experiment part, the key parameters were determined through the Plackett-Burman experiment, and then the Box-Behnken experiment was conducted on the key parameters and the Response Surface Methodology (RSM) was used to obtain the optimal combination of machining parameters. Compared with mechanical grinding, the problems of edge collapse and breakage are solved. The overcut is reduced by 35.1%, the edge damage is reduced by 42.2%, the surface morphology is improved and the surface roughness value is reduced by 47.7%. Compared with ECDM, the problems of heat affected zone and thermal defects are solved. The overcut is reduced by 49.1%, the edge damage is reduced by 56.6%, the surface feather morphology is removed and the surface roughness value is reduced by 74.9%. The machining stability and consistency of ECDM-G method are analyzed by machining array microchannels. Finally, with the optimized machining parameters, the microfluidic chip with typical microchannel structure was fabricated by ECDM-G, and the tool electrode has no severe wear after machining the long path complex structure, which proves that ECDM-G can be an energy-saving, sustainable and effective method for machining precision glass microstructures with high quality, and further shows that ECDM-G has industrial application prospects in the manufacturing of key biological and medical components.

Effect of Stitching, Stitch Density, Stacking Sequences on Low-Velocity Edge Impact and Compression after Edge Impact (CAEI) Behavior of Stitched CFRP Laminates.

Low-velocity edge impact and compression after edge impact (CAEI) behavior of stitched carbon-fiber-reinforced plastic (CFRP) laminates were experimentally investigated in the paper. Five groups, including three stacking sequences (P1, P2, P3) and two stitch densities (stitch space × stitch pitch is 10 mm × 10 mm and 15 mm × 15 mm) of stitched/unstitched CFRP laminates, were prepared by the VARTM technique and subjected to low-velocity edge impact and compression after edge impact experiments. The damage of CFRP laminates was detected by optical observation and micro-CT. The effects of stitching, stitch density, stacking sequences and impact energy on properties of edge impact and CAEI were discussed. The results show that the damage of edge impact of stitched laminates is smaller than that of unstitched laminates. The main failure mode of CAEI of the unstitched laminates is delamination and that of the stitched laminates is global buckling. The addition of stitches can effectively improve the edge impact resistance and damage tolerance of CFRP laminates. Compared with the unstitched laminates with the same stacking sequence, the peak impact force of the laminates with stitch density 15 mm × 15 mm increases by 5.61-12.43%, and the increase in residual compression strength is up to 5-20.9%. The peak impact force of the laminates with stitch density 10 mm × 10 mm increases by 8.1-31.4%, and the increase in residual compression strength is up to 24.2-27%. Compared with the other two stacking sequences (P1 and P2), the stacking sequence P3 has excellent resistance of edge impact and CAEI properties.

Simulation of edge cracking using shear GTN damage model during hot plate rolling of magnesium alloys

Edge cracks are a more prominent problem during the rolling process of magnesium alloy sheets. The hexagonal structure of magnesium alloys and the product defects caused by the second phase impurities mixed in the sheets are the main causes of edge cracking. Conventional hot-rolled edge cracking simulations can only characterize the edge damage of the sheets numerically, however, the actual crack morphology is ignored. In this paper, the Gurson-Tvergaard-Needleman (GTN) damage model coupled with a continuous medium shear damage model was developed for improving the applicability of the model at low-stress triaxiality. Powell’s “Dogleg” method was used in the numerical solution of the damage model instead of the traditional Newton-Raphson method and the Vumat subroutine was written for the finite element simulation by the stress return algorithm. The damage model parameters were calibrated by a shear specimen. The results showed a good agreement between the simulated crack morphology and the experiment.

Prediction of magnesium alloy edge crack in edge-constraint rolling process by using a modified GTN model

Edge cracks are a type of damage that critically affect the quality and properties of rolled Mg alloys sheet. Accurate damage prediction plays a key role in root cause analysis and process optimization. Although the phenomenological prediction of edge damage in Mg alloy rolling has made some progress so far, the prediction of edge crack behavior and analysis of the mechanisms of crack formation and evolution during rolling have not yet been well reported. In this research, a modified Gurson-Tvergarrd-Needleman (GTN) model was proposed by modifying the growth mode of shear damage. The three-dimensional single-unit finite element (FE) model test results indicated that the proposed model improved the accuracy of the fracture response under negative stress triaxiality. Using AZ31B Mg alloy as the case study material, physical experiments and FE analysis of the rolling process were conducted. The simulations showed that the proposed model can accurately reflect the morphology and location of cracks during the rolling process, and revealed that the high-stress triaxiality at the Mg alloy edge was a significant cause of edge cracking. On this basis, an edge-constraint rolling process was proposed to inhibit edge cracking by embedding the billet into a U-shaped sheet. The numerical results showed that the minimum value of edge stress triaxiality could be reduced from -0.8 to -2.05 during edge-constraint rolling, and the accumulation of damage could be limited. The sheet forming quality was verified with different reduction rates of 30, 35, and 40%, and the results showed that the edge cracks could be effectively avoided during edge-constraint rolling, which provides an important basis for optimizing the rolling deformation process of Mg alloys.

Thermo-mechanical properties of RTM-made carbon fibre/polyimide composite attaching collar under transient heating

This study focuses on the thermo-mechanical properties of Carbon Fibre/Polyimide Composite (CFPC) attaching collars under transient heating. The CFPC attaching collars were fabricated by a high-temperature resin transfer moulding process, and their thermo-mechanical properties under the conditions of simultaneous transient heating and bending load were investigated. The results show that the attaching collar tends to fail at 118% of the limit load. The failure mode includes the fracture of the connecting screws, local extrusion damage of the hole edges, and slight ablation damage at the outer plies. And there is no observable residual deformation in the composite attaching collar. Furthermore, considering that the material properties vary with temperature, a progressive damage model based on the sequential thermo-mechanical coupling method was established to study the failure mechanism of the attaching collar. Finally, the damage factor of the CFPC was calculated to assess the safety status of the attaching collar. The results show that the primary damage modes of the composite attaching collar are intralaminar failure, which mainly occurs at the heat insulation layer and the hole edges, and these slightly affect the structural bearing capacity. A good correlation between the experiment and FEA is obtained. The test methods and analysis models proposed contribute to the safety assessment of composite structures under transient heating.

Strong influence of leaf tie formation and corresponding weak effect of leaf quality on herbivory in eight species of Quercus

Abstract Leaf shelter construction by herbivorous insects can improve leaf quality, sometimes changing resultant herbivory. In two experiments in a Missouri (USA) deciduous forest we quantified the impact of leaf tie construction and changes to leaf quality on subsequent leaf damage. First, using eight Quercus species, we compared damage to single leaves versus experimental leaf ties that had been stocked with either Pseudotelphusa quercinigracella (Gelechiidae) or Psilocorsis cryptolechiella (Depressariidae) to determine how initial leaf quality (total phenolics) influenced damage caused by shelter inhabitants. Skeletonization by leaf tying caterpillars and leaf edge chewing by free feeding species were 12.2× and 1.3× greater on tied than on non‐tied leaves, respectively. July and September leaf phenolic content had a slight positive effect on the probability of skeletonization, none on the probability of edge damage, and a weakly positive or negative effect on the intensity of skeletonization and edge damage, depending on leaf position. Second, we created experimental leaf ties, protected from herbivores, on the same Quercus species to determine whether tie formation changes leaf quality (total phenolics, nitrogen, water, toughness). Tie formation decreased phenolics, but this change was predicted to add only 0.8% leaf area loss. Synthesis. Herbivory increased dramatically when leaves were in ties, with the effect mostly due to the tie itself rather than a change in leaf quality. We predict that the advantages of building and using leaf ties in this system are more likely to be escape from natural enemies and changes in abiotic factors.

Bird impact response and damage mechanism of 3D orthogonal woven composite aeroengine blades

Various gelatin simulated bird projectiles were used to impact two key positions of three-dimensional (3D) orthogonal woven composite stator blades used in aeroengines: the center and leading edge at the blade back. The effects of impact velocity, projectile weight, and impact position on the macro damage mode were determined. Numerical simulations were conducted using the constitutive model developed in our previous work (Liu et al. 2023). The numerical simulation results were in good agreement with the experimental results. Combined test results, micro-CT and SEM observation and the numerical simulation results, the internal damage mechanism of the blade was explored. Four types of damage modes were seen under bird strike: edge damage on the narrow blade root, cracks on both sides of the narrow blade root, damage in the impact area, and complete fracture. Furthermore, the impact energy thresholds for visible damage and fracture were obtained for different bird weights and impact locations, which is of great significance to the anti-bird-strike design of composite blades.

Structural analysis of cotton stalk Puller and Shredder Machine

World scenario after pandemic COVID-19 has been drastically changing and researchers more focusing on, to minimize the post-pandemic effects on economy, energy sustainability and food security. Agriculture sector is playing pivotal role in world food security and energy sustainability. There is high need to optimize the mechanization technologies to increase the yield in limited energy inputs and operation time to fulfill the world growing food demand. This research is mainly focused on the design development and structural analysis aiding with Finite Element Analysis (FEA) approach for Cotton Stalk Puller and Shredder machine (CSPS) to cut the crop leftovers, soil conditioning (shredding the plant waste into soil) and sowing of next crop in single run by conserving input resources. The experimental trials revealed that there is high pressure on cutting blades, chocking of shredder section and excessive pulling load on tractor hitches, which affected the machine’s performance. To mitigate deficiencies and design optimization to improve the machine safety/reliability, the structure analysis carried out. Six core components of machine including baseplate, blade, gear system, root digger, pulley and shaft has investigated as per field conditions. The results revealed that the material of blade, root digger and teeth of gear system receiving the high stress under the operational conditions which results the edge wear and damage. The carbonization up to one-millimeter thickness can provide the extra strength to bear the excessive load on edge layers.

Fan Stability With Leading Edge Damage: Blind Prediction and Validation

Abstract This paper considers the impact of a damaged leading edge (LE) on the stall margin and stall inception mechanisms of a transonic, low-pressure ratio fan. The damage takes the form of a squared-off leading edge over the upper half of the blade. Full-annulus, unsteady CFD simulations are used to explain the stall inception mechanisms for the fan at low- and high-speed operating points. A combination of steady and unsteady simulations shows that the fan is predicted to be sensitive to leading edge damage at low-speed, but insensitive at high-speed. This blind prediction aligns well with rig test data. The difference in response is shown to be caused by the change between subsonic and supersonic flow regimes at the leading edge. Where the inlet relative flow is subsonic, rotating stall is initiated by the growth and propagation of a subsonic leading edge flow separation. This separation is shown to be triggered at higher mass flow rates when the leading edge is damaged, reducing the stable flow range. Where the inlet relative flow is supersonic, the flow undergoes a supersonic expansion around the leading edge, creating a supersonic flow patch terminated by a shock on the suction surface. Rotating stall is triggered by the growth of this separation, which is insensitive to the leading edge shape. This creates a considerable difference in sensitivity to damage at low- and high-speed operating points.

Study on Characteristics for Reaming Titanium Alloy Ti6Al4V with Two Kinds of Cemented-Carbide Groove Reamers.

Titanium alloys have been extensively used in practical machining owing to their outstanding mechanical properties, high specific strength and low thermal deformation. In this study, the cutting experiments are carried out on Ti6Al4V material with right-hand and straight cemented-carbide groove reamers. The experimental results show that the cutting force with the right-hand reamer is smaller compared to straight groove reamer due to the groove structure. The main tool wear forms are micro-chipping, adhesive wear, abrasive wear, and coating falling off on the right-hand reamer, while there is a built-up edge and serious damage failure on the cutting edge of the straight groove reamer. Notch wear and pitting on the surface of the hole wall are mainly caused by chip adhesion and tool wear. The surface-roughness value is the lowest as the cutting speed is 60 m/min and the feed rate is 0.4 mm/rev. The holes machined by the right-hand reamer have a low hole diameter deviation with various cutting parameters. The geometric accuracy of cylindricity is higher as the feed rate is 0.4 mm/rev and the cutting speed is 40 m/min for both kinds of reamers, and the cylindricity is better with the right-hand reamer.

Multi-Channel High-Dimensional Data Analysis with PARAFAC-GA-BP for Nonstationary Mechanical Fault Diagnosis

Conventional signal processing methods such as Principle Component Analysis (PCA) focus on the decomposition of signals in the 2D time–frequency domain. Parallel factor analysis (PARAFAC) is a novel method used to decompose multi-dimensional arrays, which focuses on analyzing the relevant feature information by deleting the duplicated information among the multiple measurement points. In the paper, a novel hybrid intelligent algorithm for the fault diagnosis of a mechanical system was proposed to analyze the multiple vibration signals of the centrifugal pump system and multi-dimensional complex signals created by pressure and flow information. The continuous wavelet transform was applied to analyze the high-dimensional multi-channel signals to construct the 3D tensor, which makes use of the advantages of the parallel factor decomposition to extract feature information of the complex system. The method was validated by diagnosing the nonstationary failure modes under the faulty conditions with impeller blade damage, impeller perforation damage and impeller edge damage. The correspondence between different fault characteristics of a centrifugal pump in a time and frequency information matrix was established. The characteristic frequency ranges of the fault modes are effectively presented. The optimization method for a PARAFAC-BP neural network is proposed using a genetic algorithm (GA) to significantly improve the accuracy of the centrifugal pump fault diagnosis.

Analysis of large edge breakage of WC-Co cemented carbide tool blades emerging in precision grinding process

This paper analyzes the edge damage characteristics of the cutting blade made of WC-Co cemented carbide material after precision grinding. The edge damage characteristics present tiny cracks and serrated continuous edge breakage. The main causes of the edge damage were explored regarding the edge residual stress, microstructure, and the change of element content. The results show that the value of the average residual compressive stress on the rear surface of the caving edge is −1745.7 MPa, which is much larger than that recorded before grinding (−578.6 MPa). The content of element C and element W on the surface increased obviously (from 28.35% to 34.29% and 54.51%–61.06% respectively). The increase of WC grains and the decrease of Co content will lead to the decrease of the bonding strength of the corresponding material, which will easily lead to the crack at the edge and cave. The grinding experiment of WC-Co cemented carbide was carried out with a bowl shape resin-bonded diamond grinding wheel and was optimized with the orthogonal experimental method. The optimized results show that the single grinding amount was the biggest factor affecting the processing time. The angular speed of rotation and the single grinding amount was listed as the factors that had the greatest influence on the blade rejection rate. Considering the processing efficiency and quality comprehensively, adopting the improved combination during the grinding process, the experimental results were as follows the blade rejection rate is 10%, and the processing time of a single blade is 205 s.

Leading edge cracking observed in WEST

One of the missions of the WEST tokamak is to test in a realistic tokamak environment, the ITER-like divertor plasma facing components made with tungsten. On exposed leading edges of monoblocks, poloidally-distributed cracks having an average spacing of 0.4 mm, running perpendicular to the cooling tube axis, were observed following the experimental campaigns in 2018. Damage may be induced by different processes which can lead to: brittle fracture below the Ductile to Brittle Transition temperature or ductile failure for which softening (recovery/recrystallization) process plays a major role. To improve our understanding about the leading edge damage process, numerical simulations were run here. The following results are specially studied: (i) the thermal gradients; (ii) the softening fraction gradient and (iii) the stress and strain distributions taking into account the mechanical properties of tungsten (elastic-viscoplastic) and the softening phenomenon. This paper describes the results obtained for a range of WEST steady state parallel heat flux (from 45 MW/ m2 to 70 MW/ m2 ) and disruption (600 MW/ m2 ) heat loading on the leading edge. Estimated results related to the plastic strain accumulation, give an interpretation of the premature cracking of the monoblock leading edge but do not explain the poloidal distribution. According to the numerical results, brittle fracture are expected under disruption as estimated normal stresses are beyond the material yield stress, along 88% of the leading edge.