Abstract: The paper presents the simulated 3D Finite Element Model (FEM) while grinding the Ti6Al4V alloy using a single abrasive wheel. Grinding simulation was carried out using a Lagrangian finite element based machining model to predict the tangential cutting force, temperature distribution at grinding zone and the effective stress and strain. All simulations were performed according to the cutting conditions designed, using the plane up-grinding. The work piece was considered as typical materials to machine difficulty. As the cutting speed is increased from 15 m/min to 33 m/min at higher feed rate, a maximum value of 750 MPa stress and higher temperature localization to an extent of 900°C at grinding zone were observed.
Abstract: In the application of laser marking, the biggest challenge is that machine-readable barcodes with superior quality were not marked consistently. To solve this problem, laser direct-part marking Data Matrix barcode experiments were carried out on titanium alloy substrates, using a Q-switched light-pumped Nd:YAG laser. The microstructure of the symbols was analyzed using an environmental scanning electron microscope (ESEM). The internal micro-stresses of the marked areas were analyzed using X-ray diffractometer (XRD). The influence of the pulse frequency on the symbol contrast is analyzed. Results showed the interaction between the laser and the titanium alloy can be found. This can further explain the physical mechanism of laser direct part marking Data Matrix symbols on titanium alloy substrates.
Abstract: Roll – forming is through the allocation of roll the sheets for multiple successive of transverse bending deformation process of the section, to form a specific shape with high energy efficiency, uniform cross section, stable product quality, etc. Since the 19th century began to study the roll-forming process, successively completed the exploration of this kind of technology and promotion from 1938 to 1938.It has entered the rapid development of roll-forming technology at present. Began to roll-forming technology research relatively late in our country, but the trend of development of fast, such as the construction industry, automotive industry, white home appliance industry has been widely used, to specific parts such as highway anti-collision WeiDang, auto parts anticollision beam beams, before and after the threshold of the anticollision beam and a side door production, etc.
Roll-forming technology belongs to the nonlinear problem of large plastic deformation, the forming theory of the present domestic scholars have researched, forming a simplified analytical method, energy analysis method, cable original research method and finite element method theory. With the development of computer aided design technology, through the computer simulation of sheet deformation and regional stress analysis, and makes the product design cycle is shortened, the product design quality was improved.
At home and abroad, roll-forming equipment have developed highly efficient, the formation of the uncoiled stamping - roll-forming - welding - material such as plastic - cut – code craft route, eventually forming the results approach to the product shape, implementation process highly integrated production mode, cold-formed molding equipment of high automation intelligent design, help to realize planning of ‘Made in China 2025 strategy’ in the industry of roll-forming.
Abstract: This paper study on the influence of ultrasonic vibration assisted grinding (UAG) process on surface topography and properties of C/SiC composites. Through the surface quality experiments of common grinding (CG) and UAG, the height distribution parameters and function parameters are obtained and used to analyze the characteristics of the material surface topography. The relationship between grinding process and the composites surface quality is pointed out by experimental research. The orthogonal design is employed to optimize ultrasonic parameters and grinding parameters. The optimized condition is carried out to modify the surface quality. The results show that ultrasonic vibration has a great influence on height and surface bearing properties; the surface roughness is improved by the small vibration amplitude and low frequency. The grinding depth is the key factor on surface topography modification and the feed rate is the second. According to the research, an important technical support is carried out to improve the surface performance of C/SiC composites.
Abstract: To evaluate the quality of the laser direct part marked Data Matrix symbols on titanium alloy substrates, the quality assessment methods at home and abroad were compared. A new quality assessment method of combining the effect of the laser on substrate materials and symbol grade of laser marked Data Matrix was put forward. Depending on previous research works, orthogonal experiment results were analyzed again and a modified nonlinear mathematics model was established. Analysis results indicate that this modified model can explain 90.6% of symbol contrast change and it is statistically significant. So it is better than previous linear regression model and can be used to estimate the quality of laser marked Data Matrix symbols on titanium alloy substrates. The nonlinear mathematics model can also explain the laser parameters influence on the symbol contrast.
Abstract: Utilizing all-direction electrochemical machining (ECM) for super-thin twist aero-engine, feed angle of tool cathode and blade fixture angle are investigated and optimized in this study. The most optimal combination of the two angles (oblique feed angle of tool cathode and fixture angle of blade stock) is selected from all 65341 angle combinations. Moreover, the affections of the optimized angle combination on machining error distribution between blade shape and plate are concentrated. The analysis and experimental results demonstrate that the optimized angle combination can satisfy the machining requirements of blade shape and error distribution of blade shape and plate.
Abstract: Based on geometry model of single abrasive particle, comparing abrasive geometries of different materials displayed in SEM images, it is proposed that abrasive geometry is similar to inverted cone with vertex radius in sphere. Based on abrasives with inverted cone geometry, through introducing sliding ratio, mathematical models of cutting force and specific grinding energy of single abrasive have been established to study about cutting force in meshing line of single abrasive; in accordance with specific grinding energy of single abrasive, combined with internal meshing principle, the relationship among specific grinding energy, engagement, and meshing line length l have been studied. Through simulation analysis, it is shown that the unit normal force of single abrasive in whole meshing line gradually increases from tooth top to pitch line and tooth root; the greater the value of l from pitch line to tooth top, the more the specific grinding energy accordingly; however the greater the value of l from pitch line to tooth root, the smaller the specific grinding energy therewith; the greater the engagement, the smaller the specific grinding energy which tends to stable with changing of l.
Abstract: The influence of four parameters of two-step aging on the mechanical properties of 6082 aluminum alloy bumper was studied by orthogonal test. The results show that compared with the single stage aging, the two-step aging process can reduce the aging time and improve the production efficiency under the premise of the mechanical properties of the bumper meet the requirements. Among the four aging process parameters, the second stage aging temperature and holding time are the main factors that affect the final results, while the first stage aging temperature and holding time are secondary factors. The most suitable aging process parameters for the 6082 aluminum alloy bumper is (150 °C, 2 h) + (190 °C, 2.5 h). After two-step aging, the grain of the aluminum bumper is small and evenly distributed, leading to good mechanical properties. The generalized experiment shows that the application of the two-step aging process still has some limitations and needs to be further optimized and perfected.
Abstract: Hard machinability of titanium alloy material and poor stiffness of thin-walled part restricted the extensive applications of titanium alloy thin-walled component in aerospace engineering. In order to increase geometric accuracy, a method of ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feeding direction was put forward in this paper, and the corresponding milling force characteristics in UVA milling of titanium alloy TC4 thin-walled workpiece were researched. Through theoretical analysis, the path of cutter tooth in UVA milling was analyzed. The important factors that affect milling force are obtained with the signal to noise ratio analysis. Results show that the radial cutting force in UVA milling is smaller than that in traditional milling. Cutting force fluctuate in high frequency when treated ultrasonic vibration. And the axial cutting feed is the core factor that affects the milling force. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.
Abstract: Cutting performance of reaming alloy gray cast iron HT250 using carbide, cermet and CBN reamers was studied. Experiments were conducted under constant cutting parameters and cooling strategy. Tool life, hole diameter, spindle power, surface roughness and tool wear were analyzed. The hole diameter and spindle power would keep steady when reaming with carbide reamer after 400 holes to the tool life of 1050 holes. But holes diameter reduced and spindle power increased with the number of machined holes increasing during the whole tool life when using cermet or CBN reamer. The surface roughness Rz of the holes reamed by carbide reamer was within the tolerance, although it was worse than that reamed by cermet and CBN reamer. It can be summarized that the carbide was the most suitable material for reaming alloy gray cast iron because of the longest tool life, steady hole diameter and spindle power, qualified surface roughness. After machining, crater wear and clearance wear were produced on the cermet and CBN reamer, which were caused by abrasive wear. In addition, flaking and breakages appeared on the edge of cermet reamer, which were not found on CBN reamer. However, the clearance wear of carbide reamer was smaller than that of CBN reamer, and built up edge was found along the cutting edge.