scholarly journals An experimental study on hole quality and different delamination approaches in the drilling of CARALL, a new FML composite

2021 ◽  
Vol 49 (4) ◽  
pp. 950-961
Author(s):  
Ergün Ekici ◽  
Ali Motorcu ◽  
Ensar Yıldırım
Keyword(s):  
Experimental Study ◽  
Hole Diameter ◽  
Hole Quality ◽  
Delamination Factor ◽  
Circularity Error ◽  
D Values ◽  
Delamination Damage

In this study, the hole quality was investigated in the drilling of CARALL composite. In addition, the delamination factor calculation approaches of Chen, Davim, and Machado were compared in terms of the delamination damage at the hole entrance surface. Chen's approach is based on the conventional delamination factor (F d) and Davim's on the adjusted delamination factor (F da). Finally, Machado's approach is based on the minimum delamination factor (F min). The values closest to the nominal hole diameter value were obtained with the uncoated (T1), followed by the TiN-TiAlN-coated (T2) and TiAl/TiAlSiMoCr-coated (T3) carbide drills, respectively. The average circularity error values for the hole top and bottom surfaces were 6.184 µm, 7.647 µm, and 8.959 µm for T1, T2, and T3 tools, respectively. Delamination factor values varied between 1.174 and 1.804. The F da values were found to be the highest, followed by F d values, with F dmin values determined as the lowest.

Experimental/Numerical Study of Multiple Rows of Confined Jet Impingement Normal to a Surface at Close Distances

2012 ◽  
Author(s):  
M. E. Taslim ◽  
N. Rosso
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Numerical Study ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Hole Diameter ◽  
Impingement Cooling ◽  
Discharge Coefficients ◽  
Hexahedral Elements ◽  
D Values

Impingement cooling is used in a variety of applications ranging from industrial bakeries, paper processing, heat exchangers and specially gas turbine engines of all sizes to name a few. Convective impingement cooling has been studied numerous times in a variety of configurations. However little work has been conducted regarding impingement between two surfaces separated by less than one impingement jet hole diameter. This configuration is of special interest for gas turbine cooling applications such as in shrouds, combustor liners and airfoils cooling cavities where small holes are used to cool and purge cavities between two adjacent pieces of hardware. In this study, flow and temperature fields as well as heat transfer coefficients for confined jet impingement are being investigated for multiple rows of round jets impinging normal to a target surface less than one hole diameter from the jet origin. The experiments were conducted for five rows of jets with five jets on each row and steady-state liquid crystal thermography for heat transfer measurements were utilized. Numerical results were obtained from a three-dimensional unstructured computational fluid dynamics model with over 4 million hexahedral elements. For turbulence modeling, the realizable k–ε was employed in combination with enhanced wall treatment approach for the near wall regions. Other available RANS turbulence models such as k–ω, v2f and large eddy simulation were tried for selected geometries and results are compared with those of k–ε model. Nusselt numbers on the target areas and discharge coefficients for flow across the jet holes are reported for jet Reynolds numbers ranging from 10000 to 50000, pitch-to-diameter, P/d, values of 2,3 and 4, each for jet distance-to-diameter Z/d, values of 0.3, 0.4, 0.5, 0.6, 0.8, 1, 2 and 3. Comparisons are made between the test and numerically-obtained results in order to evaluate the employed turbulence models and validate the numerically obtained results. Results showed severe reduction in discharge coefficients as the jet holes were brought closer to each other and closer to the target wall. Heat transfer performance for the hole lateral spacing of P/d = 4 was found to be superior to that for P/d = 2 or P/d = 3.

Comparisons of the use of twist, pilot-hole and step-drill on influence of carbon fiber-reinforced polymer drilling hole quality

2017 ◽  
Vol 52 (11) ◽  
pp. 1465-1480 ◽  
Author(s):  
Gong-Dong Wang ◽  
Melly S Kirwa
Keyword(s):  
Carbon Fiber ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Hole Quality ◽  
Pilot Hole ◽  
Reinforced Polymer ◽  
Thrust Forces ◽  
Step Drill ◽  
Delamination Damage

Understanding the drilling-induced damage to carbon fiber-reinforced polymer composites remains the most active research being undertaken in the composite materials world of today. Despite the vast amounts of literature available, the relationship between drilling and damage to the composites has not been fully understood. In this research, a comparative study of different drilling methods including the use of a twist drill, the use of a pilot hole/pre-drilled hole and the use of a step drill on the influence of the hole quality has been accomplished. In order to achieve this comparison, thrust forces have been monitored during drilling experiments where four different feed rates and one spindle speed have been considered. A finite element model has also been included to study delamination damage on the laminates and validate the experimental results. Results show that thrust forces increase with increasing feed rates and that drilling by step drill is the most appropriate method as it records low forces hence minimal delamination damage.

Experimental investigation on hole quality in drilling of composite pipes

2018 ◽  
Vol 42 (2) ◽  
pp. 147-155 ◽  
Author(s):  
Rajkumar Tibadia ◽  
Koustubh Patwardhan ◽  
Dhrumil Shah ◽  
Dinesh Shinde ◽  
Rakesh Chaudhari ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Feed Rate ◽  
Industrial Applications ◽  
Spindle Speed ◽  
Drilling Process ◽  
Hole Quality ◽  
Microstructural Investigation ◽  
Circularity Error ◽  
Composite Pipes

In recent years, the major reason for the rejection of composite pipes in industrial applications is due to the poor quality of the drilled hole. This paper investigates the effect of drilling process parameters on the hole quality in composite pipes made of an aluminium core surrounded by polyethylene layers. An empirical model is designed for the two input variables using response surface methodology (central composite design). An experimental investigation is carried out to study the effect of spindle speed and feed rate on quality of drilled holes, especially circularity error. It is observed that a moderate spindle speed and low feed rate are most effective in minimizing the circularity error. Microstructural investigation of drilled hole surface is also carried out using scanning electron microscopy (SEM).

Experimental study on drilling load and hole quality during rotary ultrasonic helical machining of small-diameter CFRP holes

2019 ◽  
Vol 270 ◽  
pp. 195-205 ◽  
Author(s):  
Daxi Geng ◽  
Yunda Teng ◽  
Yihang Liu ◽  
Zhenyu Shao ◽  
Xinggang Jiang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Small Diameter ◽  
Hole Quality

scholarly journals Response of round-hole tubes submitted to pure bending creep and pure bending relaxation

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110491
Author(s):  
Kuo-Long Lee ◽  
Bo-You Liu ◽  
Wen-Fung Pan
Keyword(s):  
Experimental Study ◽  
Aluminum Alloy ◽  
Theoretical Analysis ◽  
Research Team ◽  
Hole Diameter ◽  
Thickness Ratio ◽  
Experimental Results ◽  
Round Hole ◽  
Pure Bending ◽  
Time Relationship

This paper presents experimental study on the response of 6061-T6 aluminum alloy round-hole tubes with five different hole diameters of 2, 4, 6, 8, and 10 mm and four different diameter-to-thickness ratios of 30, 40, 50, and 60 submitted to pure bending creep and pure bending relaxation. Pure bending creep or relaxation is defined as bending the tube to the required moment or curvature and maintaining that moment or curvature for a period of time. The experimental results of pure bending creep show that the curvature increases with time. In addition, larger holding moment, diameter-to-thickness ratio, or hole diameter results in larger creep curvature. As the curvature continues to increase, the round-hole tube eventually breaks. The experimental results of pure bending relaxation show that the relaxation moment decreases sharply with time and tends to a stable value. In addition, larger holding curvature, diameter-to-thickness ratio, or hole diameter results in larger drop of the relaxation moment. Due to fixed curvature, the round-hole tube does not break. Finally, formulas proposed by the research team of Pan et al. were respectively improved to simulate the creep curvature-time relationship for pure bending creep in the initial and the secondary stages and the relaxation moment-time for pure bending relaxation. After comparing with the experimental results, it is found that theoretical analysis can reproduce the experimental results reasonably.

scholarly journals Experimental Study of Post Installed Rebar Anchor Systems for Concrete Structure

2020 ◽  
Vol 16 (2) ◽  
pp. 308-319
Author(s):  
Haidar H. Haidar ◽  
Faten I. Mussa ◽  
Abbas O. Dawood ◽  
Ahmed A. Ghazi ◽  
Rassel A. Gabbar
Keyword(s):  
Experimental Study ◽  
Bond Strength ◽  
Hole Diameter ◽  
The Other ◽  
Bonding Agents ◽  
Pull Out ◽  
Varied Chemical ◽  
Anchor Systems ◽  
Cylindrical Samples ◽  
Concrete Interface

AbstractThis study investigated the effectiveness of several types of adhesives used in post-installed rebar connections as a bonding agent between steel reinforcement bars and old concrete under pull out test. The experimental samples were; cylindrical samples of (150 mm dia. × 300 mm high) with anchors rebar of varying diameter (12 and 16 mm), different embedded length (100 and 150) mm with different holes’ diameters. The strategy of control were cast-in-place rebar concrete specimens while other samples are post-installed rebar concrete specimens of varied chemical adhesives as bonding agents, namely KUT EPOXY ANCHOR ‘NS’ and SIKAFLOOR169. The output showed that the different adhesives yielded closed pull-out load values. It is found that the pull-out capacity (bond strength) is increased by increasing the embedded length, the diameter of the rebar and slightly with the diameter of the hole. In addition, the failure mode of post-installed rebar concrete was governed by the embedded length and the area of contact with the adhesives. On the other hand, the larger diameter of rebar favors splitting or failure of concrete due to higher strength in binder-rebar interface compare to the binder-concrete interface. The results showed that the pull-out load was increased by (26 % and 32 %) as the rebar diameter increased from 12 mm to 16 mm for KUT “NS” and SIKAFLOOR respectively. The hole diameter had slightly effect of the pull out load where the average of increment was only 6 %. Finally, the bonding strength is considerably depended on the embedded length and less affected by the type of epoxy.

A Delamination Factor Prediction Model for Drilling of Composite Materials

2012 ◽  
Vol 601 ◽  
pp. 41-45 ◽  
Author(s):  
Xu Wang ◽  
Yan Li He ◽  
Jing Yi Wang
Keyword(s):  
Composite Materials ◽  
Shell Theory ◽  
Fiber Composite ◽  
Theory Model ◽  
Drilling Process ◽  
Carbon Fiber Composite ◽  
Damage Area ◽  
Delamination Factor ◽  
Fiber Composite Materials ◽  
Delamination Damage

In this paper，according to the shell theory , model are developed to predict delamination damage in the drilling process. Finally, we will get theoretical delamination factor and complete the prediction of the delamination damage area. The known references didn’t find similar model of predicting delamination damage. Therefore, it is new method. With the drilling process experimental contrast，the model is more effective for the prediction of delamination of the carbon fiber composite materials.

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