Microstructural characterization of blanked surface of C5191 phosphor bronze sheet under ultra-high-speed blanking

The deformation mechanism of C5191 phosphor bronze sheet under ultra-high-speed blanking was investigated.By virtue of a DOBBY-OMEGA F1 ultra-high-speed press,the ultra-high-speed blanking test was conducted on C5191 phosphor bronze sheets with a thickness of 0.12 mm at 3000 strokes per minute.The microstructures of the blanked edges were characterized and analyzed separately by electron back-scatter diffraction(EBSD)and transmission electron microscopy(TEM).The results show that grains in the blanked edges are stretched along the blanking direction.Strong{001}<100>cube textures(maximum pole densities of 9 and 12,respectively)and secondarily strong{011}<011>textures(maximum pole densities of 4 and 7,respectively)are formed in local zones.Additionally,deformation twins are found in the shear zone of the blanked edges which are rotated and coarsened due to the blanking-induced extrusion and local thermal effect which can further form into sub-grains with clear and high-angle boundaries.The C5191 phosphor bronze sheet is subjected to adiabatic shear during ultra-high-speed blanking,accompanied with dynamic recrystallization.

FEM SIMULATION AND EXPERIMENTAL RESEARCH ON THE SHEET BLANKING

Both experiment and simulation are made on the AlMg4 . 5Mn0 .4 sheet blanking with 1 % , 10% and 20% relative clearance respectively. The cutting force curves and the cutting surface parameters which can be used to describe the quality of the blankings are measured. Simulation is accomplished by MARC Autoforge software package. Calculated cutting forces are always bigger than measured ones. All difference between experiment and simulation is not greater than 20% . It is feasible making virtual experiment on workstation to estimate the cutting force and to predict the quality of the workpiece for new material using certain blanking technical parameters.

Ductile damage and simulation of fine-blanking process by FEM

Based on the Curson Tvergaard void damage plastic potential equation and by using orthogonal rules of plastic material, the influence of void volume fraction on stress and strain fields was introduced into Levy Mises flow rules. The variation principle of rigid plastic material with void degradation was demonstrated. Furthermore, FEM equations coupled with damage factor were presented to study the void growth and the criterion to judge the damage was also given. Using the developed system, the fine blanking process was simulated and the sheared surface of the part edge was predicted. Meanwhile, the influence of process parameters, such as punch die clearance, V ring force, counter force, radius of punch and die edges, on the height and quality of the sheared surface was analyzed. The calculation results were compared with the experiments, which can be used to guide the design of fine blanking process.

NUMERICAL METHOD FOR PREDICTION OF NET-SHAPED BLANK IN MULTI-POINT FORMING OF SHEET METAL

A new numerical method to predict the initial blank geometry from the desiredobjective shape of parts is presented. Based on the conditions that the deformations in materialare most evenly distributed and that the volume remains constant, a positive definite functional forblank design is constructed. The functional is minimized by an iterative scheme of finite element,and then the optimal initial configuration is obtained. The method is easy and expedient to use. Theresults of numerical simulation of forming process and multi-point forming experiments for sheetmetal demonstrate that good precision is achieved by the proposed method.

Effects of parameters on rotational fine blanking of helical gears

The application of fine blanking to the manufacturing of helical gears directly from a strip has been restricted due to the traditional linear cutting stroke of the punch and die.In this work,rotational fine blanking which combined the linear and rotational motion of punch and counterpunch was applied for the forming of helical gears.A three-dimensional(3D) rigid-plastic finite element model was developed on the DEFORM-3D platform.By finite element simulation and analysis,the influences of key parameters on the punch load and cut surface were investigated.It is shown that: 1) with increasing the counterforce or helical angle,the punch load and the depth of die roll increase; 2) with increasing blank holder force,the punch load increases while the depth of die roll decreases; 3) V-ring indenter facilitates an improvement in the quality.The results of this research reveal the deformation mechanism of rotational fine blanking of helical gears,and provide valuable guidelines for further experimental studies.

Investigation of the Process Parameters on the Blanking of AISI 304 Stainless Steel by Using Finite Element Method

Blanking is a major process and has a wide range of usage in manufacturing industry. The general concept of blanking seems a simple one but governing parameters are many and have a complex relationship which directly affect the quality of the produced parts （blanks） and also the energy efficiency of the process. The main problem is the lack of prediction capabilities of the effect of these parameters that lead to time, money and labor consuming trial and error procedures in experimental studies. Usage of FEM based programs to simulate blanking to obtain numerical results and observe the shearing mechanism is a cheap and a detailed way for industrial applications. In this study five different clearances （1%, 3%, 5%, 10% and 20%） and three different thicknesses （t = 2 mm, t = 3 mm and t = 4 mm） were used for simulation and experimental studies of the blanking process. Simulations were executed by using the FEM program, Deform 2-D. Investigations were made on the parameters related to crack progression like crack initiation and crack propagation angles, indentation angle, rollover angle and depth and also the related blanking energy values. The results of the present paper are in agreement with the results of experimental studies.

COUPLED ELECTRICAL-THERMAL-MECHANICAL ANALYSIS FOR ELECTRICAL/LASER HEATING ASSISTED BLANKING

A coupled electrical-thermal-mechanical analysis is conducted for electrical/laser heating assisted blanking. Two novel localized-heating methods, electrical heating and laser-heating, recently proposed for small-part blanking, are investigated with FE simulations. Results show that electrical heating would result in an advantageous distribution of temperature in a 316 stainless steel work-material. A desired temperature distribution may also be achievable for a copper work-material, if laser beam is used. Both electrical heating and laser-heating enable to reduce the blanking force and increase the aspect ratio achievable by blanking. The simulation also demonstrates that both electrical heating and laser-heating can result in desired temperature-distributions at sufficiently high heating-rates, ease of implementation and application. Comparatively, electrical heating could generate more favorable temperature distribution for small-part blanking.

Effects of Break-through State and System Rigidity on Vibration and Noise in Blanking

This paper studies the effects of break through state and system rigidity on vibration and noise in blanking, suggests the describtion of the generation state of breakthrough by the unloading gradient obtained from the force stroke curve, discusses the effect of the relation between the unloading gradient and the vibration system rigidity on vibration, and gives the optimal relationship between these two factors to efficiently reduce the vibration, and this conclusion is verified by noise experiments done by using two presses of unequal rigidity to carry out the same blanking.

Mechanism of localized severe plastic deformation and damage fracture in fine-blanking using mixed displacement and pressure FEM

A mixed displacement-pressure updated Lagrange FEM was used to simulate the severe plastic deformation, which can overcome shear locking and volume locking. Together with adaptive remeshing technique based on strain gradient and surface curvature, the strain localization in severe plastic deformation can be captured. Schiffmann damage density was used to predict the developments of damage and fracture in sheet metal. The intensive dislocation and slip appear under the action of severe shear deformation, and metallic grains are flattened and elongated in shear band. Because of the existence of large radius of die edge, the flow direction of grains changes, and the grains are elongated and simultaneous. As a result, it is not easy to cut the grains off, and outer surfaces with clean cut are formed.

Comparative Study on Shearing Edge Quality Influence of the Change of Tool Geometry in Fine-Blanking for Non-homogeneous Materials

Excellent quality of shearing edge implies that a s mo oth cutting edge without tearing will be observed on the whole edge surface. Thi s is one of the most significant features of the Fine-blanking process. To achi eve such a superb blanking edge quality in fine-blanking, there actually involv es quite a large number of factors, such as blanking speed, processing material, product shape, lubrication and tool geometry, to be considered simultaneously d uring the operation. Nevertheless, the thorough investigations on different effe cts of those critical factors for different kinds of popular and applicable mate rial are rare and limited. Thus, the objective of this paper is mainly focused o n the study of the quality influence of tool geometry change in fine-blanking f or non-homogeneous materials. However, the most obvious change of the tool geo metry during the operation will be the essential variation of the nose radius of the punch. This is because the nose radius usually seriously deteriorates with the increasing service period in mass production which eventually causes the ent irely lose of the specific features of the fine-blanking process. Therefore, a tailor-made experimental study was carried out to investigate the relationship between the punch nose radius and the shearing edge quality, such as blanked edg e finish, burr height and die-roll height, during fine-blanking for different types of material. Five punches with each specified nose radius (Rp), 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm and 1.00 mm, and four kinds of blanking material ( Mil d steel SS400, Stainless steel AISI316L, Copper alloy UNSC16200 and Aluminium al loy AA6063 ) were employed throughout the study. Subsequently, features of the s heared edge surfaces and data of each experiment were observed and captured for further analysis in this research. Consequently, findings show that an increase of punch nose radius would produce a higher percentage of fracture of blanked ed ge and increase the amount of burr height. In overall comparison, it is found th at mild steel and copper alloy do provide better surface edge finish with higher percentage of sheared area and less burr height than that of stainless steel an d aluminium alloy.

Dynamic Constitutive Model of Physical Simulation in High-Speed Blanking for C5191 Phosphor Bronze

Strain hardening,strain rate strengthening and thermal softening data of C5191 phosphor bronze at highspeed blanking are not easy to be obtained with a general measure method,therefore,it is quite difficult to establish the dynamic constitutive model.To solve this problem,the tensile properties at a strain rate of 1 s^(-1) by GLEEBLE-3500,and dynamic tensile conditions at strain rates of 500,1 000 and 1 500 s^(-1) by split Hopkinson tensile bar (SHTB) apparatus are studied.According to these test data,the classic Johnson-Cook equation is modified.Furthermore,the modified Johnson-Cook equation is validated in the physical simulation model of high-speed blanking.The results show that the strength of C5191 phosphor bronze maintains a certain degree of increase as the strain rate increasing and presents a clear sensitivity to strain rate.The modified Johnson-Cook equation,which has better description accuracy than the classical Johnson-Cook equation,can provide important material parameters for physical simulation models of its high-speed blanking process.

Application of CAD redevelopment in process design of stepping-mode laser blanking

To design a stepping-mode laser blanking process,in this study,CAD software was redeveloped based on VBA and a computer interface was established in the process design system. The program employs the modularization method to perform functions including one-key initialization of the process planning environment,creation and deletion of blanking steps,automatic identification of belt coordinates,recognition of the number of blanking steps in each domain,and the output and import of process data. The difficult problem of recognizing CAD block references with the same name in the automatic acquisition of belt coordinates is solved using the selection sets method,which greatly improves the efficiency of the process design,while also guaranteeing rapid development of the flexible data mold in stepping-mode laser blanking.

The Applied Research of Fracture in Three-point Bending to Blanking of Bearing Steel

The application of fracture in three-point bending to blanking of bearing steel is studied in this paper. Several mechanical models of stress blanking are discussed at first. And then the experiments have been made in special equipment of three-point bending designed by us. Several problems, such as the suitable span, the relations between bending and tension bending complex, the ratio of blanking length to the diameter, the relations of blank length to force, the feature of fracture, are studied through the experiments. The suitable parameters of three-point bending to blanking, depth and tip radius of notch and the ratio between blanking length and stick diameter have been proposed.

Investigation on ductile fracture in fine-blanking process by finite element method

In order to continuously analyze the whole fine-blanking process, from the beginning of the operation up to the total rupture of the sheet-metal, without computational divergence, a 3-D rigid visco-plastic finite-element method based on Gurson void model was developed. The void volume fraction was introduced into the finite element method to document the ductile fracture of the sheet-metal. A formulation of variation of the rigid visco-plastic material was presented according to the virtual work theory in which both the effects of equivalent stress and hydrostatic pressure in the deformation process were considered. The crack initiation of the sheet was predicted and the crack propagation was geometrically fulfilled in the simulation by separating the nodes according to the stress state. Furthermore, the influences of different state-variables on the deformation process were also studied.

Effect of Ultrasonic Vibration on Deformation in Micro-blanking Process with Copper Foil

Effect of ultrasonic vibration on deformation in micro-blanking was investigated with copper foils of different grain sizes using a developed device. It is found that maximum shearing strength is decreased by ultrasonic vibration, and this effect becomes bigger for coarse grain than that for fine grain, which can be attributed to acoustic softening effect considering the absorbed acoustic energy. Surface roughness R_a of smooth zone decreases for the polishing effect of vibration at the lateral contact surface. When ultrasonic vibration is applied, the sheared deformation area becomes relatively narrow, and it leads to the reduction of radius of rollover. The analysis of cross section in sheared deformation area shows that the crack initiation is inhabited for the existence of acoustic softening, and the proportion of smooth zone is increased. Also, angle of crack propagation becomes smaller because of periodic strain, and the angle of facture surface is decreased. As a result, the quality of micro-sheet parts is improved by applying ultrasonic vibration.

wbForming mechanism of collapse angle of fine blanking parts with sharp corners and influence of position of V-ring indenter of die on it

Fine blanking parts with sharp corners produce collapse angles in the fine blanking process,and larger collapse angles can affect the parts’ performance and lifetime. In this paper,a fine blanking part with sharp corners was taken as an example to analyze the forming mechanism of the collapse angles by DEFORM 3 D,then studying the influence of the position of the V-ring indenter of die on the collapse angle. It was concluded that the material’s metal flow line was intensive near the blanking clearance;The equivalent stress area of the material was mainly concentrated around the blanking clearance,and then gradually shrinked to joint of part and scrap;the closer the distance L was,and the smaller equivalent stress area was mainly concentrated around the blanking clearance was,and the smaller collapse angle was.

OPTIMIZING THE CUTTER FOR SLANTING KNIFE CUTTING OPERATION AND ITS BLANKING FORCE

The cutting force under a slanting cutter is discussed.It is not only related to the sheet to be cut and the slanting cutter height,but also to the shape of the cutter.It is from this point of view that the question of optimizing the cutter for slanting knife cutting operation is addressed.Then the general differential equations for the optimum cutter are obtained,and analytic solutions for the workpiece,the contour of which consists of straight lines and arcs,are obtained.A method for solving the general equations is also presented.The cutting force and breaking noise will be minimized for a given slanting cutter height and workpiece if the optimum cutter is employed.

Comparison study on measurement of rail weld joint between inertial reference method and multi-point chord reference method

Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint with a5-m wavelength range, leaving a significant knowledge gap in this field.Design/methodology/approach – In this study, the authors used the well-established inertial referencemethod (IR-method), and the state-of-the-art multi-point chord reference method (MCR-method). Two methodshave been applied in different types of rail straightness measurement trollies, respectively. These instrumentswere tested in a high-speed rail section within a certain region of China. The test results were ultimatelyvalidated through using traditional straightedge and feeler gauge methods as reference data to evaluate the railweld joint straightness within the 5-m wavelength range.Findings – The research reveals that IR-method and MCR-method produce reasonably similar measurementresults for wavelengths below 1 m. However, MCR-method outperforms IR-method in terms of accuracy forwavelengths exceeding 3 m. Furthermore, it was observed that IR-method, while operating at a slower speed,carries the risk of derailing and is incapable of detecting rail weld joints and low joints within the track.Originality/value – The research compare two methods’ measurement effects in a longer wavelength rangeand demonstrate the superiority of MCR-method.

Research advance in forest restoration on the burned blanks

How to restore the destroyed forest after forest fire is a key question that man must face. This paper reviewed the research situation and history on the forest restoration burned blanks and summed up the research methods used into four scales: seed-bank scale, community scale, ecosystem scale and landscape scale. The new technologies such as GIS & Remote Sensing used to vegetation restoration were also summarized. The strategies and developing trend of vegetation restoration research on burned blanks were discussed.

Landscape change on burned blanks in Daxing'an Mountains

Daxing抋n Mountains was one of the most important forest areas in China, but it was also an area which was prone to suffering forest fire. The catastrophic forest fire that occurred in Daxing抋n Mountains on May 6, 1987 devastated more than 1.33?06 hm2 of natural forests, which leaded to the formation of some mosaic areas with different burn intensities. Two forest farms of Tuqiang Forest Bureau (124?5-122?8E, 53?4-52?5N) were chosen as a typical area to analyze the post-fire landscape change by drawing and comparing the two digital forest stand maps of 1987 and 2000. The landscape lands of forest were classi-fied into 12 types: coniferous forest, broadleaf forest, needle-broadleaf mixed forest, shrub, nursery, harvested area, burned blanks, agricultural land, swamp, water, built-up, grass. The results showed that: 1) The burned blanks was almost restored, some of them mainly converted into broadleaf forest land during the process of natural restoration, and coniferous forest land by the artificial re-forestation, and the others almost changed into swamp or grass land; 2) The proportion of forest area increased from 47.6% in 1987 to 81.3% in 2002. Therefore, a few management countermeasures, such as the enhancing peoples consciousness of fire-proofing and constructing species diversity, were put forward for forest sustainable development.