95 results about "Forming limit diagram" patented technology

The invention relates to a method for establishing and using failure criteria for a laser tailor-welded blank with different thicknesses. The method is mainly used for judging the necking or the fracture of the laser tailor-welded blank with different thicknesses and for estimating the forming performance. The method for establishing a forming limit diagram of the laser tailor-welded blank with different thicknesses comprises the following steps: the tailor-welded blank forming limit diagram is formed by combining a welding area material, and a forming limit curve of the thin tailor-welded lateral mother plate; and the forming limit curve of the tailor-welded material adopts the M-K theory and is obtained by calculating performance parameters by combining the tail-welded area material. The method for using the forming limit diagram of the laser tailor-welded blank with differential thicknesses comprises the following steps: the strain value of the danger part of the part of the tailor-welded blank is measured and is divided into the strains of the welding area and the thin lateral mother plate; the measured strain is compared with the welding area corresponding to the strain, and the forming limit curve of the thin tailor-welded lateral mother plate, and whether the part of the tailor-welded plate loses effectiveness is judged. The method for establishing and using the failure criteria for the laser tailor-welded blank with different thicknesses accurately establishes the forming limit diagram, predicts successfully the failure of the tailor-welded plate, and effectively estimates the forming performance.

The invention discloses a method for acquiring a metal temperature forming limit diagram (TFLD). The method is characterized by comprising acquiring a TFLD of a high-strength steel plate thermal-forming process, and acquiring a TFLD of a lightweight alloy warm-forming process. The invention also discloses a test device of a TFLD. The test device is characterized by comprising a hydraulic tester, a mold, a mold heating furnace, an automatic feeding mechanism, a plate heating furnace, a plate fast-cooling device, a heating control system and a strain measurement analysis device. The method and the test device guarantee mold heating uniformity, do not change a plate forming temperature, satisfy temperature forming requirements, acquire the TFLD comprising the all-range isothermal or non-isothermal forming limit diagram in a test temperature range, have the advantages of simple operation, high automation degree and high work efficiency, and satisfy practical temperature forming process requirements.

The invention discloses a test device and method for acquiring forming limit diagrams under the complicated loading condition and belongs to the technical field of forming processing of metal plates. The test device is formed by refitting a specially made male die on the premise that a multifunctional plate forming machine is included originally, and other devices and molds are original equipment; the specially made male die comprises a small male die and a large male die, a hoop interface is arranged at the lower end of the small male die and used for butt joint with a hydraulic ejection rod, and a cavity capable of being in sleeving connection with the small male die is formed in the large male die. By means of the provided test device and method, complicated loading can be further realized, corresponding predeformation on plates is not required before bulging, and the ageing problem and the relatively complicated test process are avoided. The plates in the same size are adopted, plates in various sizes are not required to be processed, batch processing can be performed, the test time is saved, and the test period is shortened.

The invention relates to a testing device and a testing method for a forming limit diagram under a high-temperature constant-strain rate condition. The device comprises a sample deformation pressure device, a real-time strain measurement device and a controller; based on a testing method for the forming limit diagram under the high-temperature constant-strain rate condition built by the testing device, the constancy of the strain rate of a sample in a central point is realized under the condition of constant forming temperature, and a forming limit diagram under the obtained slab isothermal condition contains a forming limit curve under a constant-strain rate condition in a certain strain rate range. The testing device and the testing method have the advantages of high control accuracy and accuracy in measurement, and are significant in theoretical research and practical application of light alloys and high-strength steel warm-hot forming.

The invention relates to a method for determination of a forming limit curve of sheet metal. A piece of stamping shaping CAE simulation analysis software DYNAFORM is used for simulation of stamping forming of a piece of sheet metal to be detected, thereby determining a FLD 0 value in a shaping limit graph; and the forming limit curve of the sheet metal to be detected is calculated out though the Keeler formula. Compared with the prior art, the method for determination of the forming limit curve of sheet metal provided by the invention is simple, feasible and has low cost and small error.

The invention provides a test device for acquiring a plate thermoforming limit diagram. The device includes a universal tester, a mould, a strain measurement analysis apparatus, a heating control apparatus and a heat insulation apparatus. The universal tester includes a middle beam and a force sensor connected to the middle beam. The heating control apparatus consists of a temperature control unit and a heating component and a temperature sensing component that are respectively connected to the temperature control unit. The mould comprises a female die base, a blank-holding die and a male die. The female die base and the blank-holding die are assembled through a blank holding force control apparatus to form a plate clamping part for clamping plates. The strain measurement analysis apparatus consists of a controller, a metal corrosion marking unit and a CCD image sensor. The test device provided by the invention has a simplified overall structure, through combination of the universal tester, the mould, the strain measurement analysis apparatus, the heating control apparatus and the heat insulation apparatus, realizes precise control of the plate blank holding process and stamping forming process, and accurately acquires the plate thermoforming limit diagram.

A tester apparatus capable of obtaining a forming limit diagram pertaining to a sample having a high degree of precision includes a fixing jig and a mobile jig installed at an upper side of the fixing jig so as to enable a vertical movement. The mobile jig may be configured to fix the sample in cooperation with the fixing jig, and a driving apparatus disposed at a lower side of the fixing jig may be configured to drive the vertical movement of the mobile jig. An interlocking apparatus provided in between the mobile jig and the driving apparatus may be configured to deliver a driving force of the driving apparatus to the mobile jig.

The invention relates to an evaluation method for the hot stamping fracture property of an automobile part. The evaluation method comprises the steps that the shortest distance between a strain-temperature state coordinate point of one unit on a numerical model subjected to finite element simulation and a forming limit curve at corresponding temperature is expressed as a forming margin, and the degree of the hot stamping part relative to a fracture limit is reflected by the forming margin. The forming margins of all the units on the numerical model subjected to finite element simulation are calculated, and distribution of the strain-temperature state points is expressed in a forming limit diagram through different colors according to the forming margin gradient; the forming margins are stored in a text document in a certain format, the text document containing the forming margin information is read by a stamping forming finite element simulation software postprocessing module, and the stamping property of the hot stamping part is directly reflected in the mode of a forming margin cloud diagram on the hot stamping part numerical model. According to the method, the stamping property of the hot stamping part can be more accurately judged.

The invention discloses a pipe liquid filling bulging test method and device. The pipe liquid filling bulging test method comprises the following steps: restraining two ends of a test pipe, only releasing the freedom degree of axial movement of the test pipe, applying uniformly-increased hydraulic pressure p inside the test pipe, and synchronously applying equal force on the two ends of the pipe respectively until the pipe is broken; acquiring a real-time wall thickness t and a bulging height h of a highest point of the pipe in a bulging process; when the axial force can be used for rightly counteracting the acting force of internal pressure to the end surface of an inner cavity of the pipe, deducing an axial free bulging stress-strain curve and material parameters of the pipe by virtue of acquired bulging process data p, t and h according to a plastic theory. Pipe forming tests under different loading routes can be completed by applying different pulling force or pushing force at the two ends of the pipe so as to provide test data for the drawing of a pipe forming limit diagram. Embodiments show that a pipe bulging stress-strain curve and pipe stress-strain data with a relatively large strain range can be accurately acquired by using the method disclosed by the invention; and the test device and the pipe are convenient to disassemble and assemble repeatedly in expansion and bulging processes, and are good in implementation effect.

The invention discloses a method and a system for establishing a fracture forming limit diagram of a high-strength aluminum alloy sheet, and relates to the technical field of sheet forming limit determination. The method comprises the following steps of firstly, obtaining a fracture criterion related mechanical variable comprising fracture initial strain and fracture end strain through a combination scheme of a unidirectional tensile test, a plane strain test and a bidirectional equal-tension test in the stable stress states; secondly, determining two groups of fracture parameters according tothe mechanical variable and a Lou-Huh toughness fracture criterion; and finally, computing a forming limit curve according to the two groups of fracture parameters, and drawing a fracture forming limit diagram with a fracture zone, a dangerous zone and a safety zone. According to the method disclosed by the invention, the establishment of the forming limit diagram of the high-strength aluminum alloy sheet is realized through a simple and easily-implemented test means in combination with a novel theoretical method with stronger applicability, so that the complexity of the forming limit diagramobtained by testing is avoided, the inapplicability of a traditional theory to the high-strength aluminum alloy sheet is also solved, and typical problems existing in a realization process of the novel theoretical method are also effectively avoided.

A prediction equation “R₀/t(2R/t+(2R/t+1)ε_f)/2(1−(1+2R/t)ε_f)” is derived which predicts that bendability-dominated fracture will not occur when the critical surface strain ε_critical is not exceeded by a strain on the metal sheet surface causing the occurrence of ductility-dominated fracture that is obtained from the minimum curvature radius R₀ of a press-forming mold and the critical strain ε_f in a plane strain region in a forming limit diagram. The minimum curvature radius R₀ of a mold required to prevent the occurrence of bendability-dominated fracture is estimated, and the mold is designed with a curvature radius that is not less than the curvature radius R₀.

The invention discloses a method for measuring sheet metal deformation based on images, which adopts a multi-axis rotation and lifting structure, a CCD camera, an optical lens, and an image and data processing computer. The images of a sheet metal before and after deformation are shot and stored in the image and data processing computer to form data files; and a forming limit diagram and parameter information are acquired through a bulging test and a tension test respective to form standard data files. The method can store and analyze material performance in various aspects so as to screen spare sheet metals from various aspects.

The invention relates to a method and a device of forming a limit diagram in the technical field of laser shock sheet forming, in particular to a laser-propelling-based method and a laser-propelling-based device for producing a sheet shock forming limit diagram, which are mainly used for judging failure and deformation of sheets such as necking or cracking and for evaluating forming performance of the sheets. The method is characterized in that: a laser controller (2) controls a repeatable frequency pulse laser device (3) to transmit laser beam of a certain laser pulse width, a facular adjusting device adjusts the diameter of a facular, the laser beam acts on a bullet, the bullet produces momentum under the laser effect to act on different sheets with different widths, a bullet guide structure is changed along with different width of the sheets, the bullet guide structure guarantees an acting force and an acting direction of a shock force, so the sheets are uniform to deform; and by changing the length-to-width ratio of the sheets (11), different limit stress points under different stress ratios can be obtained so as to obtain the forming limit diagram of the sheets.

The invention discloses a test and calculation method for measuring an equivalent plastic strain forming limit diagram. The method comprises the following steps: measuring real uniform strain and realbreaking strain of a material; calculating primary strain and secondary strain under different simple strain paths; and drawing and correcting an equivalent plastic strain forming limit diagram (EPS-FLD). Various defects in the prior art are overcome through theoretical innovation; a technical solution is provided for automobile steel under a new situation; meanwhile, the measurement of the uniform forming limit and the fracture forming limit of the material is integrated into a uniaxial tension DIC test; under the condition that no extra test is needed and a better technical target can be achieved, no extra test is needed, and precious manpower cost and equipment cost are saved, so that the method has important theoretical and engineering practice significance.

The invention discloses a thin plate high temperature forming limit testing device. The device comprises a press plate assembly, a concave mould assembly, a convex mould assembly, a guiding and supporting assembly, a heating assembly, and a sealing assembly. The press plate assembly is arranged on the upper side and lower side. The sealing assembly is arranged on the press plate assembly and the guiding and supporting assembly. The concave mould assembly is arranged in the sealing assembly. The convex mould assembly is arranged on the press plate assembly. The heating assembly is arranged in the concave mould assembly and the convex mould assembly. The provided thin plate high temperature forming limit testing device can be used to measure the forming limit pattern of a thin plate at different temperatures under different strain rates; a heating rod is arranged in the mould, thus the testing device has a compact structure; a thermocouple-relay control loop is adopted to realize precise varied temperature experiments; at the same time, an sealed environment filled with nitrogen is adopted to achieve the high temperature forming tests of metals that can be easily oxidized; and the external surface of moulds will not be destroyed due to built-in heating devices.

The invention discloses a method for determining a forming limit of a high-strength aluminum alloy sheet. The method comprises the following steps of preparing a plurality of high-strength aluminum alloy sheet samples; carrying out a tensile test on the samples to obtain a tensile displacement curve of each sample, elastic modulus and power function hardening model parameters; carrying out simulation on a tensile process by adopting finite element software; determining stress triaxiality change data and Lode parameter change data of each sample according to the tensile displacement curve and asimulation result; solving by adopting an analytic expression of an Lou-Huh ductile fracture criterion in order to obtain a plurality of groups of fracture parameter values; determining a predictionerror of each group of fracture parameter values to each sample; and computing a forming limit diagram of the high-strength aluminum alloy sheet by adopting a principal strain space function in a principal strain space according to the plurality of groups of fracture parameter values of which the prediction error is smaller than a set threshold value. According to the method, on the basis of preferred selection, the ductile fracture criterion is applied to obtain the forming limit curves in order to form a fracture judgement ribbon area, and a judgement result is more reliable.

The invention discloses a manufacturing method of a laser impact sheet limit diagram and a data acquisition device, the limit manufacturing comprises data acquisition and drawing sheet forming limit diagram, wherein, the data acquisition comprises (1) putting the sheet printed with fine circular grids at an oval concave module; (2) the center surface of the sheet is provided with vertical laser impact load, and an optical power meter is used as an instrument for detecting the sheet break, when a digital display of the optical power meter displays the continuous red light emitted by a red light, the laser impact is stopped, and the sheet is taken out from the oval concave module; (3) the grid which presents oval shape after deformation and is most near to the break point is selected from the sheet, an grid instrument is used to detect a long shaft value and a short shaft value of the oval grid and calculates and converts them to a first main strain value and a second main strain value; (4) the ovality of the oval concave module is changed, and the steps (1)-(3) are repeated, at least 5 groups of experimental data are obtained to draw the curve; the key point of the device lies in that an infrared lamp and the optical power meter are adopted to detect whether break occurs. The invention is simple, the experimental cost is low, and the laser impact forming limit diagrams of various sheets can be rapidly drawn.

The invention discloses an experimental method for building forming limit diagram of transformation induced plasticity steel plates, relating to the building method of forming limit diagrams. The method of the invention comprises the following steps: (1) the thickness and the strain hardening index of the transformation induced plasticity steel plate are determined; (2) the limit strain value of the transformation induced plasticity steel plate under the condition of plane strain state is calculated; (3) a strain coordinate system is built, data is synthesized on the coordinate system so as to build the forming limit diagram of the transformation induced plasticity steel plate. The invention is an effective tool for solving the transformation induced plasticity steel plate material punching problem, can successfully predict transformation induced plasticity steel plate material invalidation, effectively estimates the forming performance and reduces the existing measuring workload for building a shaping limit diagram.

The invention discloses a method for establishing a shaping limit graph of a thin wall tubing and an apparatus thereof. The method is characterized in that symmetrical apertures are arranged on a surface of a target tubing, bulging is generated under effect of hydraulic pressure in a bearing tubing at an internal layer, by changing shapes, sizes and positions of the apertures, and shaping limit ofthe target tubing under all stress states in a scope from unidirectional stretching to bidirectional stretching can be obtained; under effect of hydraulic pressure in the bearing tubing at the internal layer, the target tubing and the bearing tubing at the internal layer are subjected to synchronous expansion, friction effect between two tubing is little, and an inaccurate result cannot be generated due to friction influence of the target tubing. Compared with a method for axially applying pressure or pulling force, the method of the invention is simple, closed loop servo control of the internal pressure and axial force are not required, the shapes, sizes and positions of the apertures are required to be designed in a reasonable mode, and the appropriate bearing tubing at the internal layer is selected as a support.

The invention discloses a method for establishing a forming limit diagram of a laser tailor-welded blank. The method comprises the following steps: (A) establishing an XY coordinate system of which the X represents a direction perpendicular to the direction of a welding seam and the Y represents the direction parallel to the direction of the welding seam; (B) calculating an ultimate strain of a material in a welding zone by adopting an empirical formula and combining with performance parameters of the material, and then, based on stress strain relation of the material in the welding zone and weak side parent metal, calculating to obtain weak side parent metal FLC by combining with the performance parameters of the weak side parent metal when the material in the welding zone is invalid, namely, Y-direction strain is larger than X-direction strain; (C) calculating the weak side parent metal FLC when the weak side parent metal is invalid, namely, the Y-direction strain is smaller than the X-direction strain by adopting the empirical formula and combining with the performance parameters of the weak side parent metal; and (D) marking the weak side parent metal FLCs obtained in step (B)and step (C) into an XY direction strain coordinate system at the same time to establish the forming limit diagram of the laser tailor-welded blank. The method can establish the forming limit diagramof the laser tailor-welded blank suitable for engineering application to effectively evaluate forming limit of the tailor-welded blank.