Burr Defects Research Articles

Detection and characterization of hole processing defects in carbon fiber-reinforced polymer

Abstract The defects of carbon fiber-reinforced polymer (CFRP) during the drilling process will affect the mechanical properties and service life of the components. We investigate the detection and characterization of delamination and burr defects after drilling CFRP. The drilling test was conducted on CFRP specimens, followed by image processing software to detect and extract the resulting defects. Subsequently, a more accurate two-dimensional quantitative characterization of the extracted delamination and burr defects was performed. Finally, by comprehensively considering the quality indexes of delamination and burr defects, a comprehensive evaluation factor that can fully reflect the hole-making defects is established to provide a theoretical basis and technical support for enhancing CFRP’s hole-making quality.

RER-YOLO: improved method for surface defect detection of aluminum ingot alloy based on YOLOv5.

Aluminum ingot alloy is one of the commonly used materials in industrial production and intelligent manufacturing, whose quality directly affects the performance of aluminum processed products. Therefore, the inspection of surface defects of aluminum ingot alloy is extremely valuable for actual industrial engineering. Aiming at the issues of low detecting precision and the slowly processing rate thatexisted in the traditional target detection methods for aluminum ingot alloy dataset, the YOLOv5-based improvement model RER-YOLO is proposed. Firstly, the aluminum ingot alloy dataset is coped with the image pretreatment methods of rotation, translation, contrast and brightness transformations in a random combination so as to boost the capacity of generalization for model training. Secondly, a multi-scale characteristic extraction network block (Res2Net) is utilized to take the place of the C3 block in the previous YOLOv5 to augment the model's ability that can accurately extract rich features. Finally, an over-parameterization-based re-parameterized convolutional block is utilized in place of the 3×3 convolutional blocks in the Res2Net residual block and baseline model, enlarging the search space of the network and boosting the model's fitting ability while maintaining inference rate. The comparison experimental results demonstrate that the RER-YOLO reaches a mean average precision of 75.1% on the aluminum ingot alloy dataset, which is higher 4.9% than the conventional YOLOv5 and does not increase the inference delay. It also improves the detection accuracy by 12.7% for burr defects, which are fewer in number in the dataset and the defect features are difficult to extract. It can be seen that the presented model in this study has an important reference value towards detecting surface defects in aluminum ingot alloy.

Abrasive water-jet applications in 6 mm flat glass cuttings

Abrasive Water-Jet Cutting (AWJC) is an unique technique and has found wide applications in the glass cutting industry due to high performance and cost-effective properties. There are several interconnected parameters of great importance in this method. In this experimental study, the selected AWJC parameters are working distances (3, 4 and 5 mm) and feed rates (1000, 1250 and 1500 mm/min) at constant water pressure (140 bar), abrasive grain size (120 mesh) and nozzle diameter (0,76 mm). This study will be concerned with investigating the effects of these parameters on the surface quality of flat glasses. AWJC can improve the surface quality of flat glass, if the cutting parameters are chosen appropriately. It was observed that; the optimum working distance and feed rate parameters should be selected as 3 mm and 1250 mm/min respectively, if minimum grit defect is required. Additionally, 4 mm of working distance and 1000 mm/min of feed rate cutting parameters would generate minimum burr defect.

Experimental study on machinability in sub-millimeter range of the Aluminum Alloy using Face Turning Method

One of the most factors that affect the quality of machining results is the machinability of materials. Machinability can affect the accuracy of dimension of the machining product, especially in producing small products. This study has purpose to obtain the circularity value and surface morphology of specimen as indicator of machinability of alloys Al 6020 by using face turning method in the range sub-millimeter. The effects of spindle speed and feed on circularity and surface morphology are the subject of the study. Three variations of spindle speed (440 rpm, 740 rpm and 1500 rpm) and six variations of feed (0.05 mm/rev, 0.1 mm/rev, 0.2 mm/rev, 0.3 mm/rev, 0.5 mm/rev and 1 mm/rev) were used. The circularity was calculated by image processing software and surface morphological was observed using SEM and optical microscope. Results show that the better circularity was found on smallest and largest feed for each spindle speed. The surface morphology shows some burr defect and also scatter.

Effect of fiber orientation on the milling performance of quartz fiber composites in cryogenic cooling

Quartz-reinforced polyimide composite is a kind of material with anisotropic and nonuniform properties. The machinability has high dependence on fiber orientation θ. This paper presents the first comprehensive investigation on the cutting model of composites based on fiber orientation. A series of cryogenic cooling milling experiments were carried out to study the influence of fiber orientation on surface morphology, roughness, milling force, and tool wear. The results show that fiber orientation with acute angle has more advantages than obtuse angle. At the same time, it can provide effective chip breaking for latitude and longitude fibers at θ = 45° acute angle. Besides, when the tool is swept 96°, the milling force will reach the maximum, and the shearing effect of the latitude fiber is achieved maximum near θ = 60°. Similarly, the best surface quality is obtained where pits, crack, and burr defects are effectively restrained. Meanwhile, when the chosen cutting speeds are 50, 100, and 150 m/min, the roughness of 0.86 µm, 0.61 µm, 0.5 µm can be attained with θ = 48°, 55°, and 57°, respectively. Although the tool wear is relatively obvious when θ = 60°, the tool is still in a stable wear stage with better machining effect. Hence, it can be concluded that cryogenic cooling machining has better machinability and cutting effect at fiber orientation θ = 60° with larger milling parameters.

Formation mechanism of burr defect in aramid fiber composites based on fly-cutting test

Burr, tear, and other defects induced by machining make aramid fiber-reinforced plastic (AFRP) a representative difficult-to-cut material. For analyzing the formation mechanism of burr defect, a cutting mechanical model of AFRP was established to predict effects of the angle between the feed direction and the fiber orientation on tensile and shear behavior during the cutting process. The cutting process of AFRP was studied through the single-point fly-cutting method. The failure modes of AFRP was investigated by observing the morphologies of scratches, analyzing the cutting force and effect of tool tips. The results show that large burr defects are formatted by the tensile force during the cutting process, where the clear yield and necking phenomena of aramid fibers are observed. When the fibers are in the shear stress state, few burr defects can be found. Burr defect can be reduced by increasing cutting speed and sharpness of cutting tools. With the increasing of cutting depths, the elastic recovery phenomenon is significantly decreasing the machining quality.

Milling properties of Kevlar 49 fiber composite based on fiber orientation in cryogenic cooling

Aramid fiber–reinforced epoxy resin matrix composite is an anisotropic and heterogeneous material. And the machinability is strongly dependent on the fiber orientation. In this paper, a composite milling model was established based on fiber orientation θ. Meanwhile, a series of cryogenic cooling milling experiments were carried out to research the influence of fiber orientation on surface morphology, surface roughness, milling force, and tool wear. The results show that the acute angle milling has more advantages than the obtuse one. When tool sweeps at about θ = 55°, the maximum milling force can be gotten. And the maximum shearing action can be reached for latitude fiber at θ = 30°, as well as effectively chip broken for latitude and longitude fibers. Similarly, with increased θ, the shearing fracture is weakened with insufficient chip breaking, but none affected for longitude fibers. Besides, it can be predicted that when the cutting speeds are 50, 100, and 150 m/min, as well as fiber orientation 26°, 34°, and 35°, respectively, the processed surface roughness is 0.93 μm, 0.71 μm, and 0.6 μm. At the same time, tool wear is relatively serious with θ = 40° with a stable tool wear stage, and the processing effect is not affected. Furthermore, using the bigger cutting parameters, the better cryogenic cooling milling effect can be obtained at fiber orientation near 30° with less burr defect.

Challenges to Fabricate Large Size-Controllable Submicron-Structured Anodic-Aluminum-Oxide Film

Anodic aluminum oxide (AAO) is well known for its unique controllable structure and functional contributions in research and developments. However, before AAO can be widely used in the industry, some engineering problems should be overcome. In this study, we designed a novel electrochemical mold, which can resolve the exothermal problem for large-size aluminum sheets during high-voltage anodization process. AAO film with a large sample size of 11 x 11 cm2 in area, 148 μm in thickness and 450 nm in average pore diameter, decorated with ordered-pattern structure, was successfully obtained through a 200 V anodization process. It was noticed that the local heat was generated with increasing the anodizing voltage, resulting in undesired pits and burr defects on the AAO surface. In order to retain AAO’s quality and reduce the producing cost of the anodization process, a mass producing system combining with an overhead conveyor was proposed. The convenient anodization system, novel electrochemical mold and bath may help to fabricate high-quality AAO films efficiently.

Defects Study on Drilling of Carbon Fiber Reinforced Polymer (CFRP) Laminates

The new developed carbon fiber reinforced polymer laminates are widely used in main structural components of big commercial aircrafts. Generally drilling is the final operations in manufacturing structure, which is the most important operation during assembly. Defects such as burrs and delamination always appear in the process of drilling, which makes it hard to control the drilling quality. In this research, the drilling defects of T800 CFRP laminates are evaluated by using a brad point drill and a multifacet drill in terms of drilling forces, burr defect and delamination detection. The results show that the spindle speed is the most significant factor affecting the delamination defect followed by the feed rate. High speed drilling and low feed rate could improve the surface quality and reduce the delamination. The multifacet drill showed excellent drilling performance than the brad point drill and generated smaller defects.

Experimental investigation on drilling of high strength T800S/250F CFRP with twist and dagger drill bits

T800S/250F lamination is a new high strength carbon fibre reinforced plastic (CFRP) material, which is usually defined as difficult-to-machine material and used to manufacture the key load-bearing structural components of large commercial aircrafts. Drilling is the most frequently operation used as the final assembling process for CFRP components, while the hole defects, such as delamination and burr, always occur at the exit of hole in the CFRP laminate. In this paper, the machinability of T800S/250F was investigated in term of drilling force, burr morphology and delamination factor by using uncoated carbide twist and dagger drill bits. The experimental results indicated that high spindle speed and low feed rate favour the reduction of thrust force for both drill bits. It was also identified that the dagger drill showed good performance with smaller burr defect and lower delamination factor as compared with the twist drill.

Drilling machinability evaluation on new developed high-strength T800S/250F CFRP laminates

The new developed high-strength CFRP laminates are widely employed in varieties of applications and are mainly used in main loadbearing structural components of large commercial aircrafts. Drilling is one of the important operations in manufacturing composite structure, often a final operation during assembly. Defects such as burrs and delamination in drilling of CFRP are always serious problems and lead to rejection and impose heavy loss. In the present research, the machinability of a new developed high-strength T800S/250F CFRP laminate is evaluated by using CVD coated twist drill and CVD coated dagger drill. The machinability was investigated in terms of drilling forces, burr defect, hole wall surface morphology and delamination damage. The results indicate that feed rate is the most significant factor affecting the machined surface finish followed by the spindle speed. The dagger drill showed excellent drilling performance than the twist drill and was more suitable for drilling of T800S/250F CFRP laminate. The results also highlight the importance of employing the high speed drilling to minimize the drilling-induced defects.

Effect of Fiber Directions on the Surface Quality of Milling C/SiC Composites

ts difficult to guarantee the surface quality when processing the carbon/silicon carbide (C/SiC) composites, and also easy to produce burr defect. So firstly the law of the burrs generated on different direction of fiber was analyzed theoretically. And then we milled the C/SiC composites by electroplating diamond cutting tool with different cutting parameters and fiber directions. The cutting force and the burr area size of the milling surface were also tested. After analyzing the results, the milling burr evaluation method was proposed. Then the burr area size of different fiber directions was analyzed, and the effect on the surface quality of fiber direction during milling process was studied. The result shows that the angle between surface laid carbon fiber direction and cutting direction has a significant influence on the processing quality. Milling surface quality was declined in order as 0°, 45°, 90° and 135°. So in order to improve the quality of the milling surface, the angle between surface laid fabric fiber direction and cutting direction should be less than 45°.