Step characteristic roll punching forming limit evaluation die and measuring method thereof
Technical Field
The invention relates to the field of plate forming, in particular to a step characteristic roll punching forming limit evaluation die.
Background
The roll punching process is a composite forming process, and essentially combines a punching process with a roll bending process. The roll punching process is particularly suitable for processing narrow and long variable-section parts, and has the advantages of stable forming process and small redundant deformation of the plate. Step features are common with various mechanical structures, and furthermore, a variable depth feature is also a common step feature. The current research on the forming limit of the sheet material is mostly limited to the stamping process, and the patent CN1903474A provides a forming limit testing device for the hydraulic bulging forming process. Patent CN2676182Y provides a die for forming test, in particular to a forming limit test of an arc or rectangular sample of a stamping process. Patent CN2702311Y provides a forming limit diagram measuring mold for a differential thickness laser tailor-welded blank, which can be used to obtain a forming limit diagram of a differential thickness laser tailor-welded blank of a stamping process. Patent CN201780237U provides a die for testing the forming limit of a sheet material, which is added with a heating component, and can complete the forming limit test of isothermal or differential temperature press forming of the sheet material within a certain temperature range.
However, the above-mentioned measuring device for the forming limit of the sheet material is not directed to the roll-to-roll forming process, and no patent for evaluating the forming limit of the roll-to-roll forming process has been proposed. Due to the complexity of stress and strain in the forming process of roll punching forming, the forming limit obtained by a general test has larger error when being used in the roll punching forming process, and is not beneficial to the application and popularization of the roll punching forming process. Therefore, it is necessary to develop a step characteristic forming limit evaluation mold suitable for a roll punching forming process to obtain a step characteristic roll punching forming limit, and further establish a specification indicating the design of a roll punching forming process part.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an evaluation die for researching the forming limit of the step characteristic formed by the roll punching process, so as to make up the research blank in the field of measuring the forming limit of the step characteristic roll punching.
The invention provides a step characteristic roll-punching forming limit evaluation die, which comprises an upper die set and a lower die set, wherein:
the upper die set comprises a plurality of upper die blocks, one side of each upper die block is arranged on the roller punching forming equipment, and the other side of each upper die block extends outwards to form a bulge;
the lower die set comprises a plurality of lower die blocks, one side of each lower die block is arranged on the roll punching forming equipment, and the other side of each lower die block extends inwards to form a groove matched with the corresponding protrusion;
the upper die set and the lower die set are matched with each other through the bulges and the grooves;
the at least one upper die block is a step upper die block, the protrusion of the step upper die block is provided with a step protrusion surface, the at least one lower die block is a step lower die block, and the groove of the step lower die block is provided with a step groove surface matched with the step protrusion surface.
Preferably, the step convex surface comprises a first arc surface and a second arc surface, wherein:
the first cambered surface is smoothly connected with the second cambered surface;
the first cambered surface is a concave cambered surface, and the second cambered surface is a convex cambered surface; or the first cambered surface is a convex cambered surface, and the second cambered surface is a concave cambered surface.
Preferably, if the height difference of the step convex surface is h, the radius corresponding to the first cambered surface is r1, and the radius corresponding to the second cambered surface is r2, the step characteristic of the step convex surface is defined by the parameters h, r1 and r 2.
Preferably, still include horizontal upper die piece, horizontal lower die piece, transition upper die piece and transition lower die piece, wherein:
the horizontal upper die block, the transition upper die block and the step upper die block are sequentially connected;
the horizontal lower die block, the transition lower die block and the step lower die block are connected in sequence.
Preferably, the surface of the protrusion of the horizontal upper die block and the surface of the groove of the horizontal lower die block are horizontal planes;
the surface of the bulge of the transition upper die block and the surface of the groove of the transition lower die block are inclined planes, and the transition upper die block is in transition with the horizontal upper die block and the step upper die; the transition lower die block is used for transition of the horizontal lower die block and the step lower die.
Preferably, the corners of the upper die block and the lower die block are provided with chamfers.
Preferably, the step convex surface of the step upper die block and the step concave surface of the step lower die block are provided with directions.
According to the invention, the measuring method of the roll punching forming limit evaluation die based on the step characteristics comprises the following steps:
a step of installing a die: respectively installing an upper die set and a lower die set on roll punching forming equipment;
step characteristic roll punching forming test steps: starting the roll punching forming equipment, taking down the test sample after the step features are completely formed, and finishing the primary test; adjusting parameters of the step convex surface and the step groove surface, performing a step characteristic roll punching forming test again, and performing a plurality of tests aiming at each group of different parameters;
grid measurement and size measurement: carrying out grid measurement on a step characteristic region of a formed sample piece, and further obtaining the main strain and the secondary strain of the region; measuring the dimension of the step characteristic area of the formed sample to obtain the dimension precision;
a standardization step: after a series of main strain and secondary strain of step features with different sizes are obtained, the parameters of the step convex surface and the step groove surface are standardized to obtain the forming limit of the step features formed by roll punching.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention can accurately measure the forming limit of the step characteristic roll punching by adjusting parameters h, r1 and r 2.
2. The method can be used for evaluating the step characteristic roll punching forming limit of plates with different thicknesses and different materials.
3. The step features contained in the invention have directionality, and the study of the forming limit of two conditions can be considered at the same time.
4. The invention comprises two equal section parts, and can eliminate the end influence in the forming limit evaluation process.
5. The die blocks included in the invention can be replaced, so that the service life is prolonged, and the cost is reduced.
6. The invention has simple structure, convenient use and higher flexibility.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic view of a step feature roll-punch forming limit evaluation mold provided by the present invention;
FIG. 2 is a schematic view of a lower die set;
FIG. 3 is a top view of the lower die set;
FIG. 4 is a schematic cross-sectional view A-A of a lower die set from above;
FIG. 5 is a schematic view of an upper die set;
FIG. 6 is a front view of the upper die set;
FIG. 7 is a schematic view of a mold block on a step;
FIG. 8 is a front view of the stepped upper die block;
FIG. 9 is a schematic view of a step lower die block;
FIG. 10 is a left side view of the step lower die block;
FIG. 11 is a schematic cross-sectional view B-B of a left side view of the stepped lower die block.
The figures show that:
first horizontal upper die block 1
First transition upper die block 2
Step upper die block 3
Second transition upper die block 4
Second horizontal upper die block 5
First horizontal lower die block 6
First transition lower die block 7
Step lower die block 8
Second transition lower die block 9
Second horizontal lower die block 10
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
As shown in fig. 1, the step feature roll-punching forming limit evaluation mold provided by the invention comprises an upper mold set and a lower mold set. The upper die set comprises five die blocks, namely a first horizontal upper die block 1, a first transition upper die block 2, a step upper die block 3, a second transition upper die block 4 and a second horizontal upper die block 5 which are connected in sequence; the lower die set comprises five die blocks, namely a first horizontal lower die block 6, a first transition lower die block 7, a step lower die block 8, a second transition lower die block 9 and a second horizontal lower die block 10 which are connected in sequence and are respectively matched with a first horizontal upper die block 1, a first transition upper die block 2, a step upper die block 3, a second transition upper die block 4 and a second horizontal upper die block 5. The upper die block and the lower die block respectively comprise bolt hole structures so as to be matched with roll punching forming equipment; the upper die block and the lower die block include a chamfer feature to avoid interference during the rotational forming process.
In this embodiment, the first horizontal upper mold block 1 and the second horizontal upper mold block 5 are equal-section mold blocks, that is, mold blocks with horizontal convex surfaces, the first transition upper mold block 2, the step upper mold block 3, and the second transition upper mold block 4 are variable-section mold blocks, the convex surface of the step upper mold block 3 includes directional step characteristics, and the convex surfaces of the first transition upper mold block 2 and the second transition upper mold block 4 are inclined surfaces as transition surfaces. The first horizontal lower die block 6, the first transition lower die block 7, the step lower die block 8, the second transition lower die block 9 and the second horizontal lower die block 10 are respectively matched with the first horizontal upper die block 1, the first transition upper die block 2, the step upper die block 3, the second transition upper die block 4 and the second horizontal upper die block 5. And will not be repeated here.
In more detail, the step convex surface comprises a first arc surface and a second arc surface, see fig. 8. Wherein: the first cambered surface is smoothly connected with the second cambered surface; the first cambered surface is a concave cambered surface, and the second cambered surface is a convex cambered surface; or the first cambered surface is a convex cambered surface, and the second cambered surface is a concave cambered surface. And if the height difference of the step convex surface is h, the radius corresponding to the first cambered surface is r1, and the radius corresponding to the second cambered surface is r2, the step characteristic of the step convex surface is defined by parameters h, r1 and r2, wherein r1 and r2 can be equal.
The invention also provides a forming limit measuring method using the step characteristic roll punching forming limit evaluation die. The step characteristic roll-punching forming limit test using the evaluation die provided by the invention comprises the following steps:
the method includes the steps of installing a mold block. A first horizontal upper die block 1, a first transition upper die block 2, a step upper die block 3, a second transition upper die block 4, a second horizontal upper die block 5, a first horizontal lower die block 6, a first transition lower die block 7, a step lower die block 8, a second transition lower die block 9 and a second horizontal lower die block 10 are respectively arranged on a roller punching forming device, and it is noted that a variable cross-section die block needs to be arranged in the middle of an equal cross-section die block to eliminate the end influence in the forming limit evaluation process.
And performing a step characteristic roll punching forming test. And starting the roll punching forming equipment, taking down the test sample after the step features are completely formed, and finishing the primary test. The parameters h, r1 and r2 were varied, the step feature roll-forming test was performed again, and for each different set of parameters, multiple tests were performed to reduce the error. It should be noted that, when the step characteristic roll-punching forming limit evaluating die provided by the invention is used for testing, two forming directions of the step characteristic can be considered, namely, the forming limit when a higher step is formed first and the forming limit when a lower step is formed first can be researched simultaneously.
And thirdly, grid measurement and size measurement. And carrying out grid measurement on the step characteristic region of the forming sample piece, and further obtaining the main strain and the secondary strain of the region. And measuring the dimension of the step characteristic area of the forming sample to obtain the related dimension precision.
And fourthly, standardizing. After the main strain and the secondary strain of a series of different-size step features are obtained, the parameters h, r1 and r2 are standardized based on specific requirements, and a more intuitive roll-punching forming step feature forming limit is obtained.
The invention can accurately measure the forming limit of the step characteristic roll punching based on the step characteristic roll punching forming limit evaluation die, and provides a design criterion for the design of roll punching forming parts. The method has important practical significance for popularizing the roll punching forming process, and fills the gap in the domestic field of measuring the roll punching forming limit of the plate.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.