scholarly journals Analytical and experimental investigation of the delamination during drilling of composite structures with core drill made of diamond grits: X-ray tomography analysis

2017 ◽  
Vol 52 (10) ◽  
pp. 1281-1294 ◽  
Author(s):  
Jamel Saoudi ◽  
Redouane Zitoune ◽  
Suhasini Gururaja ◽  
Mehdi Salem ◽  
Salah Mezleni
Keyword(s):  
Carbon Fibre ◽  
Analytical Model ◽  
Composite Structures ◽  
Thrust Force ◽  
Experimental Tests ◽  
X Ray ◽  
Reinforced Plastics ◽  
The Core ◽  
Proposed Model ◽  
Critical Thrust Force

Among the various forms of material damage, exit-ply delamination has been identified as one of the most deleterious damage processes associated with drilling fibre-reinforced plastics. The thrust force has been cited as the primary cause for drilling-induced exit-ply delamination. Only one analytical model for the prediction of the critical thrust force responsible for delamination using core drills can be found in the literature. In this study, a realistic model to predict critical thrust force responsible for drilling-induced exit-ply delamination in a multi-directional carbon fibre-reinforced plastic laminate with core drill has been proposed. A comparison between the proposed model, literature model as well as the experimental tests conducted during punching tests is presented. The proposed model is found to correlate well with experimental punching tests. In fact, the maximum relative errors recorded between the experimental values of the critical thrust force and the measured values are around 15%. Micro-tomography experiments have also been conducted that capture the drilling-induced damage in multi-directional carbon fibre-reinforced plastics in great detail. The X-ray images highlight the difficulty in controlling the thickness of the uncut plies located under the core drill during punching tests that can be attributed to some deviations in predictions of critical thrust force. Postmortem examination of the blind holes after punching tests also confirms the presence of a net delamination near the vicinity of the nominal diameter of the core drill, which correlates well to the hypothesis of the analytical model.

scholarly journals Theoretical modeling of the vertical stiffness of a rolling lobe air spring

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042094089
Author(s):  
Liufeng Xu
Keyword(s):  
Analytical Model ◽  
Ride Comfort ◽  
Experimental Tests ◽  
Geometric Parameters ◽  
Air Spring ◽  
Vertical Stiffness ◽  
Approximate Analytic Method ◽  
Proposed Model ◽  
Stiffness Characteristics ◽  
The Relationship

In order to study the characteristics of a rolling lobe air spring, a vertical stiffness analytical model is constructed based on thermodynamics and hydrodynamics. The merit of this vertical stiffness analytical model is that an analytical solution of geometric parameters is obtained by an approximate analytic method. Meanwhile, experimental tests are carried out to verify the accuracy of the vertical stiffness analytical model. The vertical stiffness analytical model can be used to qualitatively analyze the influence of geometric parameters on the vertical stiffness characteristics of a rolling lobe air spring. Therefore, the relationship between geometric parameters and the vertical stiffness characteristics is analyzed based on the proposed model. The conclusions show that the vertical stiffness analytical model can well predict the mechanical characteristics of a rolling lobe air spring and provide guidance for parameter design and vehicle ride comfort improvement.

Soft Computing Applications in Drilling of GFRP Composites: A Review

2013 ◽  
Vol 766 ◽  
pp. 99-107
Author(s):  
V.S. Senthil Kumar ◽  
C. Ezilarasan
Keyword(s):  
Surface Roughness ◽  
Composite Structures ◽  
Thrust Force ◽  
Optimization Techniques ◽  
Machining Parameters ◽  
Automotive Electronics ◽  
Gfrp Composites ◽  
Machining Processes ◽  
Nsga Ii ◽  
Reinforced Plastics

Glass fiber reinforced plastics (GFRP) are finding increased applications in various engineering fields such as aerospace, automotive, electronics and other industries. Among the various machining processes, drilling is the important process, mainly used in joining of composite structures. As a consequence, the number of authors have discussed on the aspects concerning the machiniability of GFRP composites. In this study, a review has been done on the machinability of drilling of GFRP composites through the various aspects such as tool materials and geometry, machining parameters and their influence on thrust force, torque, surface roughness, delamination factor and hole damage. Additionally, the modeling of the machining parameters on drilling of GFRP composites using response surface methodology (RSM), artificial neural network (ANN), fuzzy logic, NSGA-II etc., have been discussed. The results indicated that the thrust force, torque and surface roughness need to be controlled simultaneously for delamination free drilling. Further, there is a need to create a multi-response optimization in drilling of GFRP composites using different optimization techniques for obtaining optimum results of thrust force, torque, surface roughness and delamination free drilling.

scholarly journals Structurally informed design of interlocking block assemblages using limit analysis

2020 ◽  
Vol 7 (4) ◽  
pp. 448-468
Author(s):  
Elham Mousavian ◽  
Claudia Casapulla
Keyword(s):  
Limit Analysis ◽  
Rectangular Cross Section ◽  
Single Layer ◽  
Experimental Tests ◽  
Computational Framework ◽  
Coulomb’S Friction ◽  
The Core ◽  
Contact Points ◽  
Proposed Model ◽  
The Stability

Abstract This paper presents a computational framework to design assemblages of interlocking blocks and to analyze their structural feasibility. The core of this framework is an extension of limit analysis to corrugated interfaces with orthotropic sliding behavior. Such block interfaces are made of a number of locks (i.e. projections on the corrugated faces, locking the blocks together) with rectangular cross section. The sliding resistance at the block interfaces is governed by the shear resistance of the locks and Coulomb’s friction law, normal to and along the locks, respectively. This resistance is assumed as a function of different interface geometric parameters and the stress state on an interface is represented by using a number of contact points distributed over the lock centerlines. The abstraction model has been validated through the comparison of the torsion–shear behavior of an interface obtained by the proposed model and experimental tests reported in the literature. The extended limit analysis has been implemented to model single-layer shells. When the model is infeasible, the geometry of the overall shell, blocks, and interlocking interfaces can be adjusted by the designer to make the model structurally feasible. The performance of the framework is presented through several examples, which demonstrate the relationships between the geometry of the interlocking interfaces and the stability of the assemblages.

Critical thrust force predictions during drilling: Analytical modeling and X-ray tomography quantification

2016 ◽  
Vol 153 ◽  
pp. 886-894 ◽  
Author(s):  
Jamel Saoudi ◽  
Redouane Zitoune ◽  
Salah Mezlini ◽  
Suhasini Gururaja ◽  
Philippe Seitier
Keyword(s):  
Analytical Modeling ◽  
Thrust Force ◽  
X Ray ◽  
Critical Thrust Force

Modelling of thrust force for worn drill bits characterised by cutting edge radius in drilling carbon fibre–reinforced plastic/Ti-6Al-4V alloy stacks

2017 ◽  
Vol 232 (11) ◽  
pp. 1960-1972 ◽  
Author(s):  
Bin Luo ◽  
Kaifu Zhang ◽  
Yuan Li ◽  
Hui Cheng ◽  
Shunuan Liu
Keyword(s):  
Tool Wear ◽  
Carbon Fibre ◽  
Feed Rate ◽  
Thrust Force ◽  
Cutting Edge Radius ◽  
Reinforced Plastics ◽  
Edge Radius ◽  
Drill Bits ◽  
Carbon Fibre Reinforced Plastics ◽  
Maximum Thrust

Wear rates are rapid when drilling carbon fibre–reinforced plastics/Ti-6Al-4V alloy stacks because of their distinct mechanical properties. Tool wear leads to a high thrust force, thereby reducing the quality of the drilled holes. This article develops a novel mechanistic model for carbon fibre–reinforced plastics/Ti-6Al-4V stacks, which is characterised by the cutting edge radius, to predict the variation of the thrust force when drilling with worn drill bits. Drilling experiments with varying feed rates were performed using carbide twist drill bits. The thrust force and drill edge profile were measured to calibrate and validate the presented model. The edge radius increases with both the cutting distance and number of drilled holes at varying feed rates. It was found that the growth rate of the edge radius increased with the feed rate with identical cutting distances, whereas it decreased slightly with the feed rate when the number of drilled holes was identical. Tool wear reduces the equivalent rake angle of the drill edge, resulting in higher thrust force. The maximum thrust force increases almost linearly with the edge radius of worn drills for both materials. The predicted thrust force curves are in very good agreement with the measured curves during the entire process. Average absolute errors of the maximum thrust force for carbon fibre–reinforced plastics and Ti-6Al-4V alloy are 3.24% and 1.88%, respectively.

scholarly journals Planetary evolution with atmospheric photoevaporation

2020 ◽  
Vol 638 ◽  
pp. A52 ◽  
Author(s):  
C. Mordasini
Keyword(s):  
Analytical Model ◽  
Orbital Period ◽  
Core Mass ◽  
X Ray ◽  
Planetary Evolution ◽  
Atmospheric Escape ◽  
The Core ◽  
Core Composition ◽  
Low Mass ◽  
Gas Accretion

Context. Observations have revealed in the Kepler data a depleted region separating smaller super-Earths from larger sub-Neptunes. This can be explained as an evaporation valley between planets with and without H/He that is caused by atmospheric escape. Aims. We want to analytically derive the valley’s locus and understand how it depends on planetary properties and stellar X-ray and ultraviolet (XUV) luminosity. We also want to derive constraints for planet formation models. Methods. First, we conducted numerical simulations of the evolution of close-in low-mass planets with H/He undergoing escape. We performed parameter studies with grids in core mass and orbital separation, and we varied the postformation H/He mass, the strength of evaporation, and the atmospheric and core composition. Second, we developed an analytical model for the valley locus. Results. We find that the bottom of the valley quantified by the radius of the largest stripped core, Rbare, at a given orbital distance depends only weakly on postformation H/He mass. The reason is that a high initial H/He mass means that more gas needs to evaporate, but also that the planet density is lower, increasing mass loss. Regarding the stellar XUV-luminosity, Rbare is found to scale as LXUV0.135. The same weak dependency applies to the efficiency factor ε of energy-limited evaporation. As found numerically and analytically, Rbare varies a function of orbital period P for a constant ε as P−2pc∕3 ≈ P−0.18, where Mc ∝ Rcpc is the mass-radius relation of solid cores. We note that Rbare is about 1.7 R⊕ at a ten-day orbital period for an Earth-like composition. Conclusions. The numerical results are explained very well with the analytical model where complete evaporation occurs if the temporal integral over the stellar XUV irradiation that is absorbed by the planet is larger than the binding energy of the envelope in the gravitational potential of the core. The weak dependency on the postformation H/He means that the valley does not strongly constrain gas accretion during formation. But the weak dependency on primordial H/He mass, stellar LXUV, and ε could be the reason why the valley is so clearly visible observationally, and why various models find similar results theoretically. At the same time, given the large observed spread of LXUV, the dependency on it is still strong enough to explain why the valley is not completely empty.

scholarly journals Tire-Rim Interaction, a Semi-Analytical Tire Model

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Federico Ballo ◽  
Giorgio Previati ◽  
Massimiliano Gobbi ◽  
Gianpiero Mastinu
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Analytical Model ◽  
Lightweight Design ◽  
Experimental Tests ◽  
Tire Model ◽  
Crucial Importance ◽  
Wheel Rim ◽  
Proposed Model ◽  
Development And Validation

This paper deals with the development and validation of a semi-analytical tire model able to compute the forces at the interface between tire and rim. The knowledge of the forces acting on the rim is of crucial importance for the lightweight design of wheels. The proposed model requires a limited set of data to be calibrated. The model is compared with complete finite element (FE) models of the tire and rim. Despite its simplicity, the semi-analytical model is able to predict the forces acting on the rim, in agreement with the forces computed by complete FE models. The stress state in the wheel rim, computed by the developed semi-analytical model matches fairly well the corresponding stress state coming from experimental tests.

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