Tool wear processes in low frequency vibration assisted drilling of CFRP/Ti6Al4V stacks with forced air-cooling

Drilling CFRP/Ti6Al4V stacks in one-shot time becomes essential in the modern aerospace manufacturing sectors in order to guarantee the productivity due to the demands of riveting and fastening assembly. In the present study, a novel integrated system of low frequency vibration assisted drilling (LFVAD) coupled with the forced air-cooling was designed to investigate the tool wear issues in drilling of CFRP/Ti6Al4V stacks. The used uncoated solid tungsten carbide tools were specially designed with threaded shanks forfitting the adapter of the LFVAD tool holder. Main geometrical features of the threaded shank drills include a 6.35 mm diameter, a 140° point angle, a 30° helix angle and two cutting edges. Drilling temperatures and forces were in-situ measured for the LFVAD subjected to varying conditions, and the results were compared with the conventional drilling under the identical drilling conditions. It is found that the small titanium chip segments produced by the interrupted cut of vibration drilling can be removed efficiently via the help of the forced air-cooling. Compared with the conventional drilling, slower flank wear rates and lower cutting temperatures are identified under the LFVAD with the forced air-cooling. The adhesive wear is the main wear mode for both drilling methods; however, the chemical wear becomes more pronounced while the cutting edge chipping predominates in the LFVAD. In sum, the LFVAD with the forced air-cooling is confirmed capable of improving the machinability of the CFRP/Ti6Al4V stacks from the aspects of reducing tool wear

Study on Performance of PVD AlTiN Coatings and AlTiN-Based Composite Coatings in Dry End Milling of Hardened Steel SKD11

Dry milling of hardened steel is an economical and environmentally friendly machining process for manufacturing a mold and die. Advances in coating technology makes the dry milling a feasible approach instead of a traditional grinding process. However, the cutting condition is particularly severe in a dry machining process. High-performance coating is desired to meet the requirement of green and highly efficient manufacturing. This study concerned the performance of AlTiN-based coatings. The effect of Al content, and the AlTiN composite coating on the cutting performance of tools are investigated in terms of friction force at the tool–chip interface, specific cutting energy, cutting temperature on the machined surface, tool wear pattern and mechanism, and surface integrity. The results show that advanced AlTiN-based coatings reduce the force and cutting energy and protect the cutters from the high cutting temperature effectively. The main wear mechanisms of the coated tools are adhesive wear, chipping induced by fatigue fracture and abrasive wear. In general, the dry milling of hardened steel with AlTiN-based coatings gains a quite satisfactory surface quality. Furthermore, AlTiN-WC/C hard-soft multilayer coating performs well in reducing cutting force, preventing adhesion wear and isolating the cutting heat, being suitable for dry milling of hardened SKD11

Study on Performance of PVD AlTiN Coatings and AlTiN-Based Composite Coatings in Dry End Milling of Hardened Steel SKD11

Dry milling of hardened steel is an economical and environmentally friendly machining process for manufacturing a mold and die. Advances in coating technology makes the dry milling a feasible approach instead of a traditional grinding process. However, the cutting condition is particularly severe in a dry machining process. High-performance coating is desired to meet the requirement of green and highly efficient manufacturing. This study concerned the performance of AlTiN-based coatings. The effect of Al content, and the AlTiN composite coating on the cutting performance of tools are investigated in terms of friction force at the tool–chip interface, specific cutting energy, cutting temperature on the machined surface, tool wear pattern and mechanism, and surface integrity. The results show that advanced AlTiN-based coatings reduce the force and cutting energy and protect the cutters from the high cutting temperature effectively. The main wear mechanisms of the coated tools are adhesive wear, chipping induced by fatigue fracture and abrasive wear. In general, the dry milling of hardened steel with AlTiN-based coatings gains a quite satisfactory surface quality. Furthermore, AlTiN-WC/C hard-soft multilayer coating performs well in reducing cutting force, preventing adhesion wear and isolating the cutting heat, being suitable for dry milling of hardened SKD11

Experimental Investigation on Cutting Characteristics in Nanometric Plunge-Cutting of BK7 and Fused Silica Glasses

Ductile cutting are most widely used in fabricating high-quality optical glass components to achieve crack-free surfaces. For ultra-precision machining of brittle glass materials, critical undeformed chip thickness (CUCT) commonly plays a pivotal role in determining the transition point from ductile cutting to brittle cutting. In this research, cutting characteristics in nanometric cutting of BK7 and fused silica glasses, including machined surface morphology, surface roughness, cutting force and specific cutting energy, were investigated with nanometric plunge-cutting experiments. The same cutting speed of 300 mm/min was used in the experiments with single-crystal diamond tool. CUCT was determined according to the mentioned cutting characteristics. The results revealed that 320 nm was found as the CUCT in BK7 cutting and 50 nm was determined as the size effect of undeformed chip thickness. A high-quality machined surface could be obtained with the undeformed chip thickness between 50 and 320 nm at ductile cutting stage. Moreover, no CUCT was identified in fused silica cutting with the current cutting conditions, and brittle-fracture mechanism was confirmed as the predominant chip-separation mode throughout the nanometric cutting operation

An optimization investigation on surface roughness and its evolution with tool wear in dry turning of boron alloy cast iron

601-608Boron alloy cast iron (BACI) with good mechanical properties is usually used as cylinder liner material for heavy-duty diesel engines. Fine surface finish is often required for the machined surface of BACI cylinder liners. This study is mainly focused on the cutting parameters optimization on surface roughness and its evolution with tool wear in dry turning of BACI. Response surface methodology (RSM) involving central composite design is employed in the optimization of cutting parameters on surface roughness. An optimization parameter is determined with the consideration of the surface roughness and machining efficiency. The evolutions of tool wear and surface roughness are also investigated during BACI turning by using uncoated and PVD-TiAlN coated carbide inserts. The results indicate that RSM is effective for the optimization of cutting parameters on surface roughness. It is also confirmed that the PVD-TiAlN coated insert showed a good performance with long tool life and steady surface quality during BACI turning process

A Review on Roller Compaction Quality Control and Assurance Methods for Earthwork in Five Application Scenarios

Successful quality control and quality assurance (QC/QA) of earthwork compaction is critical to the long-term performance of roads, railways, airports, dams, and embankments. The purpose of this paper is to provide insights into the current practice, existing problems, challenges, and future development trends of QC/QA methods from the perspective of bibliometrics and the development stage. A bibliometric analysis is presented. Through quantitative analysis of literature and qualitative analysis of the development stage, insights into the current research practices and future directions of QC/QA methods have been derived from the perspectives of literature, cluster analysis, classification, different types of QC/QA methods, conclusions, and recommendations. It is found that the current QC/QA methods can be roughly divided into conventional compaction, digital rolling compaction, automatic rolling compaction, and intelligent control compaction. Currently, QC/QA methods are mainly confronted with the issues of accurate detection of compaction quality, autonomous optimization and intelligent decision-making of compaction process, multi-machine coordination, QC/QA-related specification formulation, and process standardization. To address these issues, several critical potential research directions are further identified: comprehensive CCI measurement system; simple and realistic mathematical representation of the complex compaction dynamics; parallel computing and distributed management of multi-source heterogeneous data; standardized application workflow and the cost–benefit assessment in the context of the full life cycle; intelligent control theories, methods, and technologies of earthwork compaction based on multidisciplinary integration. The paper enables researchers to obtain a comprehensive understanding of QC/QA methods for earthwork compaction as well as the suggested solutions for future work

Strain-rate sensitivity of tensile behaviors for nickel-based superalloys GH3044 and GH4033 at room temperature

336-340Nickel-based superalloys are of interest for high temperature applications, e.g. aircraft engine, due to their excellent high temperature mechanical/physical properties. The strain-rate sensitivity of the tensile behaviors at room temperature of nickel-based superalloys GH3044 and GH4033 are investigated concerning mechanical properties, microstructures and fracture surface morphologies. The experimental results showed that the yield strength and ultimate tensile strength of alloy are approximately 35%-40% larger than that of GH3044 alloy. With the increase of strain rate, the yield strength values of the two superalloys increased, while the configuration of the stress–strain curves is independent of strain rate. In addition, grain refinement phenomenon is observed on the microstructure of GH4033 alloy under a higher strain rate. It has a limited influence on the microstructure of GH3044 alloy, which can be attributed to the solid solution strengthening effect for the latter. Besides, the fracture analysis demonstrated that the dimple-ductile fracturing is the main tensile fracture mechanism for both GH3044 and GH4033 alloys

Influence of Fiber Orientation on Single-Point Cutting Fracture Behavior of Carbon-Fiber/Epoxy Prepreg Sheets

The purpose of this article is to investigate the influences of carbon fibers on the fracture mechanism of carbon fibers both in macroscopic view and microscopic view by using single-point flying cutting method. Cutting tools with three different materials were used in this research, namely, PCD (polycrystalline diamond) tool, CVD (chemical vapor deposition) diamond thin film coated carbide tool and uncoated carbide tool. The influence of fiber orientation on the cutting force and fracture topography were analyzed and conclusions were drawn that cutting forces are not affected by cutting speeds but significantly influenced by the fiber orientation. Cutting forces presented smaller values in the fiber orientation of 0/180° and 15/165° but the highest one in 30/150°. The fracture mechanism of carbon fibers was studied in different cutting conditions such as 0° orientation angle, 90° orientation angle, orientation angles along fiber direction, and orientation angles inverse to the fiber direction. In addition, a prediction model on the cutting defects of carbon fiber reinforced plastic was established based on acoustic emission (AE) signals