Method for evaluating bending performance of copper alloy plate strip based on force and displacement curve

Abstract

The invention provides a method for evaluating the bending performance of a copper alloy plate strip based on a force and displacement curve, which comprises the following steps of: preparing the copper alloy plate strip into a bending sample, and grinding and polishing the surface of the bending sample; a bending test is carried out on an electronic universal testing machine, a female die of a bending die is fixed to a compression platform of the testing machine, a male die of the bending die is fixed to a movable cross beam, the testing machine is controlled to move downwards to carry out the bending test, and a force and displacement curve of the copper alloy plate strip in the bending process is obtained; and judging the bending condition of the copper alloy plate strip according to the obtained force and displacement curve shape. The method has the advantages that the judgment mode is more direct, accurate and simple, the defects that an original judgment mode is low in precision, complex in process, incapable of achieving quantification, greatly affected by human factors and the like are overcome, and good applicability and innovativeness are achieved.

Description

Technical Field

[0001] The invention relates to the field of quantitative evaluation of the bending performance of copper alloy plates and strips, and in particular to a method for evaluating the bending performance of copper alloy plates and strips based on a force-displacement curve. Background Art

[0002] Copper alloy plates and strips have good mechanical properties and electrical and thermal conductivity, and are widely used in the manufacture of connectors, plug-ins, springs, etc. Often, the final product needs to be obtained through plastic forming processes such as stamping and bending. At present, the bending performance of strips is mainly evaluated through bending tests, but the existing bending methods are not standardized. They are mainly determined by observing whether there are visible cracks on the surface to determine whether the material bending test is qualified.

[0003] The existing evaluation method is too single, greatly affected by human factors, and lacks further verification process. Therefore, it is necessary to establish a reliable bending test and evaluation method to achieve quantitative judgment of bending conditions. Summary of the invention

[0004] The purpose of the present invention is to provide a method for evaluating the bending performance of copper alloy plates and strips based on force and displacement curves, so as to solve the problem that the prior art cannot quantify and accurately evaluate the bending performance of plates and strips.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: A method for evaluating the bending performance of a copper alloy plate and strip based on a force-displacement curve comprises the following steps in sequence: Step 1: Prepare the copper alloy plate and strip into a bending specimen, and grind and polish the surface of the bending specimen; Step 2: The bending test is carried out on an electronic universal testing machine. The concave die of the bending die is fixed on the compression platform of the testing machine, and the convex die is fixed on the moving crossbeam. The testing machine is operated to move the weight downward to carry out the bending test, and the force and displacement curve of the copper alloy plate and strip in the bending process is obtained; Step 3: Evaluate the bending performance of the plate and strip based on the shape of the force and displacement curve obtained in step 2.

[0006] Preferably, in step 1, the thickness t of the copper strip is 0.1-2 mm, and the size of the bending sample is 20×10 mm.

[0007] Preferably, in the bending test process in step 2, the moving speed of the punch is controlled to be 2-20 mm / min.

[0008] Preferably, the bending test in step 2 obtains different relative bending radii R by changing the punch radius r, and R is calculated as R=r / t, and the range of R is between 0-10.

[0009] The evaluation method described in step three is to make a judgment based on the shape of the force and displacement curve. If the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0010] Advantages of the present invention: The feature of the present invention is that the bending quality of the plate and strip is converted into the form of a force and displacement curve, and the judgment form is changed from the existing observation of the surface morphology after bending (relying on a microscope) to judgment based on the shape of the curve. In comparison, the advantage of the present invention is that the judgment method is more direct, accurate and simple, avoiding the shortcomings of the original judgment method such as low precision, complex process, inability to quantify and being greatly affected by human factors. Therefore, this evaluation method has good applicability and innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of stress-displacement curve for surface crack specimen; Figure 2 It is a schematic diagram of the stress-displacement curve of the surface microcrack specimen; Figure 3 It is a schematic diagram of the stress-displacement curve of the surface wrinkle specimen; Figure 4 Schematic diagram of the stress-displacement curve for a smooth surface sample. DETAILED DESCRIPTION

[0012] Example 1 A method for evaluating the bending performance of a copper alloy plate and strip based on a force-displacement curve comprises the following steps in sequence: A 0.5 mm thick copper alloy sheet strip was selected to prepare a bending specimen with a size of 20×10 mm, and the surface of the bending specimen was ground and polished; Step 2: The bending test is carried out on an electronic universal testing machine. The bending die is fixed on the compression platform of the testing machine, and the punch is fixed on the moving crossbeam. The testing machine is operated to move the gauge downward for the bending test, and the moving speed of the punch is controlled to be 5mm / min5. Punches with different fillet radii are selected in turn for bending experiments to obtain the force and displacement curves of the copper alloy plate and strip bending process.

[0013] Step 3: Evaluate the bending performance of the plate and strip according to the shape of the force and displacement curve: if the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time, and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0014] Example 2 A method for evaluating the bending performance of a copper alloy plate and strip based on a force-displacement curve comprises the following steps in sequence: A 0.1 mm thick copper alloy sheet and strip was selected to prepare a bending specimen with a size of 20×10 mm, and the surface of the bending specimen was ground and polished; Step 2: The bending test is carried out on an electronic universal testing machine. The bending die is fixed on the compression platform of the testing machine, and the punch is fixed on the moving crossbeam. The testing machine is operated to move the gauge downward for the bending test, and the moving speed of the punch is controlled to be 20mm / min. Punches with different fillet radii are selected in turn for bending experiments to obtain the force and displacement curves of the copper alloy plate and strip during the bending process.

[0015] Step 3: Evaluate the bending performance of the plate and strip according to the shape of the force and displacement curve: if the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time, and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0016] The bending test described in step 2 obtains different relative bending radii R by changing the punch radius r. R is calculated as R=r / t, and the range of R is between 0-10.

[0017] The evaluation method described in step three is to make a judgment based on the shape of the force and displacement curve. If the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0018] Example 3 A method for evaluating the bending performance of a copper alloy plate and strip based on a force-displacement curve comprises the following steps in sequence: A 2mm thick copper alloy sheet strip was selected to prepare a bending specimen with a size of 20×10mm, and the surface of the bending specimen was ground and polished; Step 2: The bending test is carried out on an electronic universal testing machine. The bending die is fixed on the compression platform of the testing machine, and the punch is fixed on the moving crossbeam. The testing machine is operated to move the gauge downward for the bending test, and the moving speed of the punch is controlled to be 2mm / min. Punches with different fillet radii are selected in turn for bending experiments to obtain the force and displacement curves of the copper alloy plate and strip during the bending process.

[0019] Step 3: Evaluate the bending performance of the plate and strip according to the shape of the force and displacement curve: if the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time, and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0020] The bending test described in step 2 obtains different relative bending radii R by changing the punch radius r. R is calculated as R=r / t, and the range of R is between 0-10.

[0021] The evaluation method described in step three is to make a judgment based on the shape of the force and displacement curve. If the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

[0022] In addition to the above-mentioned experimental materials and implementation methods, the method of the present invention can also be extended to other alloy materials. Those skilled in the art can make various changes and deformations based on the present invention. As long as they do not depart from the spirit of the present invention, they should all fall within the scope defined by the claims attached to the present invention.

Claims

1. A method for evaluating the bending performance of copper alloy sheets and strips based on force and displacement curves, characterized in that : It includes the following steps in sequence: Step 1: Prepare the copper alloy plate and strip into a bending specimen, and grind and polish the surface of the bending specimen; Step 2: The bending test is carried out on an electronic universal testing machine. The concave die of the bending die is fixed on the compression platform of the testing machine, and the convex die is fixed on the moving crossbeam. The testing machine is operated to move the weight downward to carry out the bending test, and the force and displacement curve of the copper alloy plate and strip in the bending process is obtained; Step 3: Evaluate the bending performance of the plate and strip based on the shape of the force and displacement curve obtained in step 2.

2. The method for evaluating the bending performance of a copper alloy sheet and strip based on a force-displacement curve according to claim 1, characterized in that : The thickness t of the copper strip described in step 1 is 0.1-2 mm, and the size of the bending sample is 20×10 mm.

3. The method for evaluating the bending performance of a copper alloy sheet and strip based on a force-displacement curve according to claim 1, characterized in that : In the bending test process described in step 2, the moving speed of the punch is controlled to be 2-20 mm / min.

4. The method for evaluating the bending performance of a copper alloy sheet and strip based on a force-displacement curve according to claim 1, characterized in that : The bending test described in step 2 obtains different relative bending radii R by changing the punch radius r. R is calculated as R=r / t, and the R range is between 0-10.

5. The method for evaluating the bending performance of alloy plates and strips based on force and displacement curves according to claim 1 is characterized in that The evaluation method described in step three is to judge based on the shape of the force and displacement curve. If the curve rises and then remains straight, the surface is smooth or slightly wrinkled; if the curve rises first and then remains for a period of time and then drops, it is a slight surface crack; if the curve rises first and then drops immediately, it is a serious surface crack.

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