The invention relates to a testing device for establishing a high-temperature formed limit diagram of an ultrahigh-strength boron steel plate. The testing device comprises an upper die frame and a lower die frame, wherein the lower die frame is provided with a plurality of guide posts, the upper die frame is sleeved on the guide posts, the lower surface of the upper die frame is provided with a male die device, and the lower die frame is provided with a blank holder and a female die which correspond to the position of the male die device and are stacked up and down and fixed together through a connector; the upper die frame and the lower die frame are provided with a cooling water passage respectively; heaters are arranged in a male die, the female die and the blank holder; and a temperature probe is arranged at the inner end of the male die. Meanwhile, the invention also discloses a testing method using the device. By combining the high-temperature expansion test requirement of the ultrahigh-strength steel plate, the formed limit diagram of the ultrahigh-strength steel plate at a certain specific high temperature is obtained by thermal forming limit test. The device and the method have significance for researching the forming performance of the ultrahigh-strength boron steel plate for an automobile, and can promote the popularization and application of ultrahigh-strength boron steel in the field of automobiles.

Testing device and testing method for establishing high-temperature formed limit diagram of ultrahigh-strength boron steel plate

The invention discloses a method for improving sheet forming limit, namely a bidirectional pressurization charging and forming method for a sheet. The method can improve the forming limit of the sheet to a great extent, thus realizing heating and constant temperature control on the sheet with high heating efficiency and small error. In the invention, the sheet is subjected to differential temperature forming in the heat charging and forming process so as to improve the forming limit of the sheet and enhance the actual efficiency of the method. In the invention, the sheet bears unequal hydraulic pressures in the positive and negative directions in the forming process, thus facilitating forming of the sheet. The method for improving sheet forming limit is not only suitable for the charging and forming process of normal temperature metal sheets, but also applicable to the charging and forming process of high temperature metal sheets.

Method for improving sheet forming limit

The invention provides a device and a method for testing a forming limit of a sheet material in a three-dimensional stress state, relating to the device and the method which are used for testing the forming limit of the sheet material. Aiming to the problems that the forming limit of the sheet material in the three-dimensional stress state is difficult to test and an influence of normal pressure to the forming limit is difficult to estimate, the device comprises an upper die and a lower die. In a test, a fluid medium is injected into the lower die, a test sample of the sheet material is placed, mold clamping force is applied, the fluid medium is injected into the upper die, and pressurized deformation is carried out by controlling pressure in the upper die and the lower die in sequence. Braking strains of the test sample of the metal sheet material can be calculated according to measured data before and after circular or square mesh deformation, namely epsilon 1=Ln[d1-d/d] and epsilon 2=Ln[d-d2/d]; a plurality of groups of different limit strain data points can be obtained by changing a ratio of a long shaft to a short shaft of an oval cross section of a cavity; and the obtained data points can be connected or fitted by respectively using the epsilon 1 and the epsilon 2 as a transverse coordinate and a vertical coordinate, so as to obtain the sheet material forming limit curve at the three-dimensional stress state at a certain normal pressure condition to estimate the influence of the normal strain to the forming limit in the three-dimensional stress state.

Device and method for testing forming limit of sheet material in three-dimensional stress state

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.

Method for acquiring metal temperature forming limit diagram (TFLD) and testing device therefor

The invention relates to an intelligent pressure detection stamping die and belongs to the technical field of metal stamping The intelligent pressure detection stamping die comprises an upper die holder and a lower die holder which are arranged opposite to each other, wherein a male die is arranged on the upper die holder; a female die is arranged on the lower die holder; a pressing plate for blank pressing of a stamping forming piece is arranged on the female die; the female die comprises a female die plate and a coaming plate connected with the lower die holder and the female die plate; the lower die holder, the female die plate and the coaming plate form a forming cavity; a forming hole through which the male die can go in and come out of the forming cavity is formed in the female die plate; pressure sensors are paved in the male die and the female die uniformly at intervals; the output ends of the pressure sensors are connected with an analog/digital conversion module and a central processing unit sequentially; and the output port of the central processing unit is connected with a 485 communication module

Intelligent pressure detection stamping die

The utility model provides a sheet-forming limit testing die, which comprises a female die, an edge-pressing die and a male die, and heating parts for heating and temperature sensors for temperature measurement are arranged in the edge-pressing die and the male die, and are connected to a temperature controller through cables. The sheet-forming limit testing die can simulate the temperature state in the actual stamping process, carry out equal-temperature or different-temperature forming limit test on sheets within a certain temperature range, independently heat the female die, the male die and the edge-pressing ring of the die and independently control the temperature of each part of the die to obtain an optimal forming limit diagram, and moreover, the sheet-forming limit testing die is simple and easy to operate.

Sheet-forming limit testing die

The utility model discloses a deep-drawing mould for evaluating the forming performance of a metal thin plate. The deep-drawing mould comprises a concave mould, an edge pressing mould and a convex mould which are sequentially arranged from top to bottom. Heating components and thermocouples are respectively arranged at the inner parts of the concave mould, the edge pressing mould and the convex mould; the heating components are used for carrying out heating, the thermocouples are used for carrying out temperature detecting, and all the heating components and the thermocouples are respectivelyconnected onto an external temperature controller by cables. The deep-drawing mould respectively heats the concave mould, the edge pressing mould and the convex mould by the heating components, so asto simulate the mould temperature rising environment in the forming process of the metal thin plate, thereby truly evaluating the deep-drawing forming performance of the metal thin plate under the conditions of heating and temperature difference; in addition, the thermocouples can carry out independent temperature detecting; moreover, the split type structure of the convex mould and a supporting rod can improve the heat isolating performance between each mould and a test pressure machine.

Deep-drawing mould for evaluating forming performance of metal thin plate

The utility model discloses an experimental die used for testing tube forming. The experimental die comprises a lower die insert provided with a hollow ring-shaped semi-columnar structure, and an upper die insert connected with the lower die insert, wherein, the upper die insert comprises a main body of the upper die insert, a hollow elliptic columnar body and two chamfer areas; the main body of the upper die insert, which is provided with a hollow ring-shaped semi-columnar structure, is connected with the lower die insert to form a hollow ring-shaped columnar structure; the hollow elliptic columnar body is arranged on the main body of the upper die insert and communicated with the main body of the upper die insert; and the two chamfer areas are arranged on the main body of the upper die insert and respectively positioned on the two sides of the hollow elliptic columnar body. By utilizing the experimental die used for testing tube forming, which is disclosed by the utility model, each ultimate strain state and a corresponding double-drawing strain state FLD (forming limit diagram) curve of an experimental tube in a hydraulic forming test can be acquired conveniently.

Experimental die used for testing tube forming

The utility model discloses a stamping die for measuring a plate shaping friction coefficient; the stamping die comprises a blank-holding die, a male die stretching into the blank-holding die and a female die arranged at the upper end of the blank-holding die; mounting cavities are arranged inside the blank-holding die, the male die and the female die; and a pressure sensor for measuring the friction coefficient is arranged in the mounting cavity. The stamping die can carry out real simulation plate stamping and shaping test by the driving of the tester, and can count a tangential resultant force and a normal force in the position through the conditions of the three-directional stress in the plate deformation position measured by the pressure sensor, therefore, the utility model accurately measures the real-time friction coefficient in the position and provides real and reliable data for the production research of the plate.

Stamping die for measuring plate shaping friction coefficient

The utility model relates to bulging molds, particularly to a spherical bulging mold. The spherical bulging mold comprises a concave mold, a convex mole and an edge pressing mold, wherein, the concavemold and the edge pressing mold are fixedly connected with the upper tabletop and the lower tabletop of a tester respectively; the material pressing surfaces of the edge pressing mold and the concavemold are in concave-convex fit; the convex mold is arranged in the inner chamber of the edge pressing mold; and the bottom of the convex mold is connected with the actuator of the tester. The bulgingmold further comprises a sensor, a profile contact, a cover plate and a mounting bolt, wherein, a mounting hole is formed on the convex mold; the sensor is arranged in the mounting hole; the profilecontact is mounted at the upper end of the sensor and the outer surface of the profile contact is in the same plane of the surface of the convex mold; the cover plate is arranged at the lower end of the sensor; a mounting screw hole is formed on the cover plate; and the sensor and the profile contact are mounted in the mounting hole of the convex mold by the mounting bolt through the mounting screw hole. The bulging mold can perform accurate and real-time measurement to the friction coefficient at the plate characteristic points during punching, and realizes simple structure and convenient operation.

Spherical bulging mold

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