Testing and calculating method for measuring hole expansion rate

A calculation method and technology of hole expansion rate, applied in the direction of applying repetitive force/pulsation force to test material strength, measuring devices, instruments, etc., can solve the problems of limited hole expansion test standard engineering application, so as to save purchase cost and management Cost, enhanced application space, and cost-saving effects

Active Publication Date: 2021-11-02
肖锋
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] Therefore, both GB / T 24524 and ISO 16630 have great deficiencies and controversies in terms of "judgment of the termination moment of the crack penetrating through the thickness of the sample" and "calculation method of material hole expansion rate", which seriously limit The Engineering Application of Hole Reaming Test Standard

Method used

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  • Testing and calculating method for measuring hole expansion rate
  • Testing and calculating method for measuring hole expansion rate
  • Testing and calculating method for measuring hole expansion rate

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Experimental program
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Effect test

Embodiment 1

[0078] In this embodiment, the material DP780 / 2.1mm is taken as an example, and its flow chart is as follows figure 1 The new reaming test flowchart of shown embodiment one comprises the steps:

[0079] Step 1. Preparation of reaming samples: According to the sample size requirements and punching regulations stipulated in GB / T 24524 or ISO 16630 standards, prepare a number of samples with an initial diameter of D 0 Reaming specimens equal to 10mm, such as figure 2 Specimens after punching as shown;

[0080] Step 2, fixed-stroke loading: take 3 samples from the prepared reaming samples; place the reaming samples on the reaming testing machine with the burrs facing upwards, and keep the lower edge of the hole in line with the The conical punch is in contact, that is, the empty stroke d 0 equal to zero, then the set fixed loading stroke d fix Equal to effective loading stroke d eff . In this fixed stroke loading test, the effective loading stroke d eff It is equal to 6.87...

Embodiment 2

[0095] According to the test process and test method in Example 1, the sample burr is facing down, and the hole expansion test is carried out. When the effective loading stroke is equal to 6.3mm, there is one sample among the three samples, and the edge of the outer diameter of the hole is the most serious. The state of the crack is "only micro-cracks visible to the naked eye", such as Figure 9 Microcracks are visible to the naked eye on the edge of the outer diameter of the hole with the burr facing downward, and no microcracks visible to the naked eye are seen in the other two samples, which meet the test termination conditions, and this sample is judged to be an effective sample. Measure and record the outer diameter D of this effective sample after reaming out Equal to 12.45mm, then the hole expansion rate of material DP780 with burrs facing downward measured in this hole expansion test is 24.5%. If there are multiple effective samples, take the average value as the hole...

Embodiment 3

[0097] In this embodiment, the material DP780 / 2.1mm is taken as an example, and its flow chart is as follows figure 1 shown, including the following steps:

[0098] Step 1. Preparation of reaming samples: According to the sample size requirements and punching regulations stipulated in GB / T 24524 or ISO 16630 standards, prepare a number of samples with an initial diameter of D 0 Reaming specimens equal to 10mm, such as figure 2 shown;

[0099] Step 2, fixed-stroke loading: take 3 samples from the prepared reaming samples; place the reaming samples on the reaming testing machine with the burrs facing upwards, and keep the lower edge of the hole in line with the The conical punch is in contact, that is, the empty stroke d 0 equal to zero, then the set fixed loading stroke d fix Equal to effective loading stroke d eff . In this fixed stroke loading test, the effective loading stroke d eff It is equal to 6.878mm, and the same effective loading stroke is used to carry out th...

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Abstract

The invention discloses a testing and calculating method for measuring a hole expansion rate. The method comprises the following steps: preparing a hole expansion sample, loading a fixed stroke, judging an effective sample, recording test data and calculating the hole expansion rate. According to the method, corresponding technical solutions are formulated for the problems of crack judgment standards and hole expansion rate calculation methods in current hole expansion test standards, the technical defects in a traditional test method are overcome, the measurement precision of the material hole expansion rate is improved, a solid foundation is laid for engineering application of the hole expansion rate in a stamping simulation model, and the problem of edge cracking of advanced high-strength steel can be solved. The method has the technical advantages of practicability, low cost, high precision and standardization, and has important engineering practical significance and wide engineering application prospects.

Description

technical field [0001] The invention belongs to the field of thin metal plate forming, in particular to a test and calculation method for measuring the hole expansion ratio of metal materials. Background technique [0002] Advanced high-strength steel is prone to edge cracking in stamping forming of parts, which is a common engineering problem faced by OEMs and steel plants. "How to prevent edge cracking?" and "How to predict edge cracking?" are the current research focus on edge cracking in academia and engineering. [0003] Aiming at "how to prevent edge cracking?", OEMs and steel mills have formed a broad consensus that increasing the hole expansion rate of materials can effectively reduce the risk of edge cracking of parts. Regarding "how to predict edge cracking?", some experts and scholars have realized the feasibility and importance of hole expansion rate as an evaluation index of edge cracking, such as the published literature of the United States Steel Corporation ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01B21/10G01N3/32G01N3/06
CPCG01B21/10G01N3/32G01N3/06G01N2203/0005G01N2203/0062G01N2203/0282Y02P90/30
Inventor 肖锋
Owner 肖锋
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