かえりなしせん断加工の成功条件および切り口面品質に及ぼす材料延性の影響

To compare the quality and reproducibility of cuts produced by four automatic microkeratomes: Amadeus, Hansatome, Summit-Krumeich-Barraquer (SKBM), and Supratome. For the adjustable models (Amadeus and SKBM), the effects of oscillation frequency and blade feed rate were determined. Eight cuts (flap thickness 160 to 180 microm) were made with each microkeratome at each parameter setting and examined using a scanning electron microscope. Quality of the cut surface was scored for each flap according to four criteria, and results were averaged to give a maximum possible score of 64. Quality of the cut edges was scored from 1 (blurred indistinct edge) to 3 (sharp and clearly visible edge). The four microkeratomes performed similarly on overall quality of the cut surface (range: 78% to 88% of theoretical maximum). The Hansatome scored highest (88%), followed by SKBM (86%; 1.0 mm/s blade feed and 7000 rpm oscillation), Amadeus (84%; 2.5 mm/s, 8000 rpm), Supratome (84%; 16.6 mm/s, 12,500 rpm), Amadeus (81%; 3.0 mm/s and 13,000 rpm), and SKBM (78%; 1.5 mm/s, 14,000 rpm). Performance differences were clearer for cut edge quality. The Amadeus produced cuts of the highest quality in 62.5% of cases (at both settings), compared with only 12.5% of cases with the Hansatome, 25% of cases with the Supratome and SKMB (1.0 mm/s, 7000 rpm), and in no cases with the SKBM at 1.5 mm/s and 14,000 rpm. Overall, high frequency with low blade feed rate is desirable for reproducible sharp edges and cut area quality. However, at very high frequencies (e.g., 14,000 rpm with the SKBM) tissue is displaced, producing an uneven cut area. Oscillation/feed quotients of 2000 to 4000 (rpm/mm x s) are a good compromise. Sharp edges are believed to reduce the risk of comeal erosion, introduction of epithelial cells into the interfacial region, and scarring during wound healing.

Ring-shaped glass fiber/polyester composite specimens cut from composite pipes with various lengths and cut edge quality were immersed into deionized water, and their water absorption was noted regularly by registering their mass gain. Monotonic ring compression tests were performed to monitor the stiffness properties during the water absorption process. Effect of specimen length and cut edge sealing with the matrix material of the pipe on the water absorption process was analyzed. Water absorption curves were fitted to the experimental data with very high correlation coefficients. Specimen types with cut edge sealing were found to absorb significantly less water than the other types, and the absorbed water showed a nonlinear monotonic decreasing tendency with specimen length. Mechanical properties were found to be only slightly affected by moisture probably because of the small amount of absorbed water.

Lasers are increasingly being used in the manufacturing of lithium (Li)-ion batteries. Lasers provide a number of advantages over conventional mechanical processes, including no tool wear, flexible cut pattern, improved edge quality, increased precision, and lower cost of operation. In particular, pulsed infrared (IR) lasers have, in many cases, successfully replaced mechanical punching processes for Li-ion battery foil cutting. While the quality of the cuts achieved using IR lasers is acceptable, it is suspected that slight impurities and defects on cut edges may potentially lead to lower battery performance. One possible way to alleviate such concerns is to improve the processing quality by reducing the wavelength of the processing laser. Another possibility is to use ultrashort-pulse lasers. In this work, we compare foil cutting results using pulsed IR and green lasers. We demonstrate that speeds of greater than 1 m/s can be achieved with a burr height of less than a few microns for cutting both coated and bare anode and cathode foils.Lasers are increasingly being used in the manufacturing of lithium (Li)-ion batteries. Lasers provide a number of advantages over conventional mechanical processes, including no tool wear, flexible cut pattern, improved edge quality, increased precision, and lower cost of operation. In particular, pulsed infrared (IR) lasers have, in many cases, successfully replaced mechanical punching processes for Li-ion battery foil cutting. While the quality of the cuts achieved using IR lasers is acceptable, it is suspected that slight impurities and defects on cut edges may potentially lead to lower battery performance. One possible way to alleviate such concerns is to improve the processing quality by reducing the wavelength of the processing laser. Another possibility is to use ultrashort-pulse lasers. In this work, we compare foil cutting results using pulsed IR and green lasers. We demonstrate that speeds of greater than 1 m/s can be achieved with a burr height of less than a few microns for cutting both coated...

The article describes the influence of the parameters of laser cutting on the cut edge quality of 10 mm S355J2 structural steel. The cutting process was carried out with a fiber laser. The basic evaluation criteria were measurements of perpendicularity tolerance, average profile height of roughness Rz5, visual evaluation, and measurements of hardness HV10. Moreover, the factorial regression models were prepared to investigate the standardized effects of the process parameters on the cutting quality. The variable process parameters were laser beam power, cutting velocity and working gas pressure. For regression modeling, low and high levels of these factors were considered representing the effective range of each parameter. The research presented in this paper proves that there are statistical correlations between the examined factors that have a significant impact on the achieved cutting effect. By the analysis of the process control parameters, it is possible to achieve an optimal level of quality that facilitates further technological operations on a given cutting product.

Analysis of fracture in burr formation at the exit stage of metal cutting

The latest research on laser beam fusion cutting (LBFC) with static beam shaping have shown a limitation in the quality of cut parts for thick steel plates (> 6 mm) when using solid state lasers. The approach of dynamic beam oscillation has recently shown to be capable of overcoming this challenge, allowing to increase the cutting speed as well as improving cut edge quality beyond the state of the art. The present paper investigates the influence of longitudinal, linear beam oscillation in LBFC of 12 mm mild and stainless steel plates by analyzing different parameters as cutting speed, burr, surface roughness, heat affected zone (HAZ), and recast layer. Reasons for the observed process improvements compared to static beam shaping have been discussed. The adjustment of the energy deposition and interaction time of the laser beam with the material found to be most relevant for optimizing the LBFC process. In particular, for beam oscillation, a gradual energy deposition takes place and increases the interaction time. This reduces the heat input in terms of HAZ and recast layer by more than 50%, resulting in high cut edge quality and more than 70% faster cutting speed.

Laser beam cutting is a non-contact, production-flexible and highly productive technique that allows accurate profiling of a wide range of sheet materials. To these and further benefits, laser machining is increasingly being adopted by industry. This paper investigates the effect of material type, workpiece thickness, cutting speed and assistant gas pressure on cut quality for industrial-relevant applications using a CO2 laser. AlMg3 aluminum alloy, St37-2 low-carbon steel and AISI 304 stainless steel were selected to represent the most established materials in many industrial fields and gain insight into different processes (i.e., inert-assisted fusion cutting and oxygen cutting) and absorption behaviors with respect to CO2 laser wavelength. The aim was to enhance the understanding of the mechanisms through which laser cutting parameters and workpiece parameters interact in order to identify general criteria and well-optimized process parameters which guarantee the kerf quality. The quality of laser cut was analyzed in its basic terms: kerf geometry, surface roughness and cut edge quality. The experiments were performed by using a systematic experimental design approach based on Design of Experiments, and the results were validated via Analysis of Variance. Quality assessment was presented and discussed. The visual inspection of cut sections confirms good overall quality and limited presence of laser cut imperfections. The experimental investigation demonstrates that the different materials can be successfully processed within a wide range of the tested values. In addition, optimum cutting conditions which satisfy the straight requirement of the quality standard adopted are identified for each material. This study involves an analysis of both phenomenological and practical issues.

The forming failure of AZ31 alloy sheet during deep drawing processes was predicted by the FEM and ductile fracture criteria. Uniaxial tensile tests of round-notched specimens and FE simulations were performed to calculate the critical damage values for three ductile fracture criteria. The critical damage values for each criterion were expressed as a function of strain rate at various temperatures. In order to determine the best criterion for failure prediction, Erichsen cupping test under isothermal conditions at 250℃ were conducted. Based on the plastic deformation histories obtained from the FE analysis of the Erichsen cupping tests and the critical damage value curves, the initiation time and location of fracture were predicted under bi-axial tension deformation. The results indicate that the Cockcroft-Latham criterion had good agreement with the experimental data. In addition, the FE analysis combined with the criterion was applied to another deep drawing process using an irregular shaped blank and these additional results were verified with experimental tests.

The shielded slot plates for a molten carbonate fuel cell(MCFC) have a sheared corrugated trapezoidal pattern. In the FEM simulations for the production of the shielded slot plate, the user material subroutine VUMAT in the commercial FEM software ABAQUS was used to implement a ductile fracture criterion. The critical damage value for the ductile fracture criterion was determined by comparing the experimental results of the shearing process with the simulation results. Using the ductile fracture criterion, the FEM simulation of the three-dimensional forming process of the shielded slot plate was conducted. The effects of the shearing process on the forming process were examined through FEM simulation and experiments. The forming simulation of nine unit cells was conducted. Using the simulation results of the forming process, the deformed shape after springback was calculated. The experimental result shows good agreement with the simulation.

High power fiber lasers offer several advantages for industrial use; high power with stable output, parameter flexibility, low maintenance costs, high efficiency and small footprint. A 200W SPI / Rofin fiber laser system was used to study the potential for high speed remote cutting and welding using a galvo scanner. Metallurgical analysis of the weld quality, cut edge quality and the throughput of fiber laser welding for a variety of materials and applications are presented.

The investigation was carried out using a Cilas 2000 W CO 2 laser on various armor steel grades with thicknesses less than or equal to 15 mm.The purpose of this investigation was to thoroughly characterize the cuts so obtained, assess the influence of cutting parameters on the quality of cut edges and determine the contribution of laser cutting of physical and mechanical properties, fabricability and service behaviour of armor steels as compared to other means of cutting or machining.Special emphasis was laid on the attempt to know about residual stresses in the cut heat affected zone and to determine the fatigue resistance of the laser-cut or -machined parts.

In the present study, high-power CO2 laser cutting of steel plates has been investigated and the effect of the input laser cutting parameters on the cut surface quality is analyzed. The average roughness of the cut surface of the specimens, produced by different laser beam diameter and laser power, were measured by using roughness tester. The scanning electron microscopy SEM is used to record possible metallurgical alterations on the cut edge. The aim of this work is to investigate the effect of laser beam diameter and laser power on the cut surface roughness and on the heat affected zone width HAZ of steel plates obtained by CO2 laser cutting. An overall optimization was applied to find out the optimal cutting setting that would improve the cut surface quality. It was found that laser beam diameter has a negligible effect on surface roughness but laser power had major effect on roughness. The cut surface roughness decreases as laser power increases. Improved surface roughness can be obtained at higher laser power. Also, laser beam diameter and laser power had major effect on HAZ width. It increases as laser power increases.

Fracture prediction of thin plates under localized impulsive loading. Part II: discing and petalling

Evaluation of ductile fracture criteria in a general three-dimensional stress state considering the stress triaxiality and the lode parameter

ABSTRACTField observations on deep parts of the root zone of the Caledonian orogen are combined with the geophysical data available for recent continental collision zones such as the Alps, to provide a model for dynamics of crustal root zones.Rocks descending into the root zone are locally infiltrated by fluids which cause eclogitization along shear zones and fluid pathways. The eclogite facies rocks vary in density from 3.1 to 3.6 g cm‐3, reflecting the compositional variation in their protoliths. Where the amount of highly ductile eclogitic material reaches about 40% the descending crustal segment loses its coherence and disintegrates into a breccia where blocks of granulite facies rocks float in a matrix of eclogite material. A density‐stratified root zone develops, where light unreacted or partly eclogitized material floats on an ‘ocean’ dominated by eclogite facies rocks, the top of which may correspond to the Moho. Catastrophic decent of this eclogitic layer may (1) transport blocks of light material to depths of > 90 km, which upon further disintegration due to eclogitization are released and return by buoyancy forces to the crust; (2) result in extension and uplift of the partly‐eclogitized lighter material.