CN-122016504-A - Method for determining high-temperature tensile true stress strain curve

CN122016504ACN 122016504 ACN122016504 ACN 122016504ACN-122016504-A

Abstract

The invention relates to the technical field of material experiments, in particular to a method for determining a high-temperature tensile true stress strain curve, which comprises the steps of taking a rod-shaped tensile sample with a circular section for high-temperature tensile experiments, drawing a force-time change curve according to a force value acquired by the experiments and the tensile length of the sample under the same coordinate system, finding out the force value and the corresponding sample elongation in the same time, determining the total length of two sections of samples, the total elongation of a selected section of necking area along the axial direction of the sample and the original length of the sample before deformation, calculating the minimum cross-section area of the necking area of the sample, calculating the corresponding stress value through the stress value, and obtaining the relation between stress and strain according to the stress value, thereby obtaining a corresponding true stress strain curve.

Inventors

ZHAO BAOCHUN
HUANG LEI
YUAN HUI
MA HUIXIA
JIN XING
SUN CHENGQIAN

Assignees

鞍钢股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260209

Claims (4)

1. The method for determining the high-temperature tensile true stress strain curve is characterized by comprising the following steps of: s1, taking a rod-shaped tensile sample with a circular section for high-temperature tensile test, wherein the radius of the circular section of the sample is Length of ; S2, the force value corresponds to the elongation of the sample; Drawing a force time-varying curve under the same coordinate system according to the force value acquired by the experiment and the stretched length of the sample, and finding out the force value in the same time when the stretched length of the sample is time-varying curve and the time is the same Elongation of sample corresponding to the elongation ; S3, determining parameters before and after deformation of the high-temperature tensile sample; the tensile sample is broken into two sections through a high-temperature tensile experiment, and the total length of the two sections of samples is When the test piece is broken by stretching, the total elongation is Then ; Taking one of the two broken samples for analysis, and measuring the length of the necking area along the axial direction of the sample as , Part of the sample involved in deformation, original length 2 before deformation Calculated from the following formula: 2 ; s4, calculating the minimum cross-sectional area of the sample necking zone: ; Wherein, the A minimum cross-sectional radius for the necked area of the sample; S5, calculating the corresponding stress value through the stress value F And obtaining the relation between stress and strain according to the stress value, thereby obtaining a corresponding true stress strain curve, wherein the relation between stress and strain is as follows: ; Wherein, the Is stress as True strain at that time.
2. The method for determining the high-temperature tensile true stress strain curve according to claim 1, wherein the step S1 specifically comprises the steps of taking a rod-shaped tensile sample with a circular section, welding a thermocouple at the middle position of the sample, and then mounting the sample on a thermal simulation tester for high-temperature tensile experiments, wherein force values, strain and the tensile length of the sample are collected in the experimental process.
3. The method of claim 1, wherein the minimum cross-sectional radius of the necked down region of the specimen is the specimen bearing force value The radius of the smallest cross-section circle of the sample is calculated as follows: The test specimen is subjected to a force value of during high-temperature stretching When the elongation of the sample was When the bearing force value of the sample The radius of the smallest cross-sectional circle of the sample is The elongation of the sample at the side of the smallest cross-sectional circle was Taking the straight line where the diameter of the smallest cross-section circle is located as the x axis, and the straight line where the axis of the sample is located as the y axis, and establishing a rectangular coordinate system, the equation corresponding to the curve of the side surface of the sample on one side of the smallest cross-section circle in the established rectangular coordinate system can be expressed as follows: ; Wherein, the Is a constant to be determined; The coordinates of the curve equation passing through two points are respectively ,0)、( , + ) Solving for the undetermined constant : ; ; According to the principle of calculus, and the tensile sample participating in the deformation part, the volume before and after deformation is unchanged, and the following formula is provided: ; the left end is a volume calculation formula of a deformed sample, the right end is a volume calculation formula of the deformed sample, and the minimum cross-section radius of a sample necking zone is obtained: 。
4. The method for determining a high-temperature tensile true stress-strain curve according to claim 1, wherein the stress value F is calculated to be the corresponding stress value : 。

Description

Method for determining high-temperature tensile true stress strain curve Technical Field The invention relates to the technical field of material experiments, in particular to a method for determining a high-temperature tensile true stress strain curve. Background The high-temperature tensile test can reflect the comprehensive influence of external force and temperature on the performance of the metal material, and in scientific test or accident analysis, the characteristic values, characteristic curves, such as maximum stress, true stress-true strain curves and the like, of the material at each temperature need to be known. The plasticity and toughness of the material are important performance parameters for reflecting the characteristics of the material, and the true stress-strain curve is a true reflection of the plastic deformation rule of the material in the stretching process and is an important basis for determining the true breaking strength and deformation resistance of the material. The high-temperature mechanical property and rolling force prediction of the material based on the high-temperature tensile test data are mainly adopted by a thermal simulation tester and a material mechanical tester. The force sensor is embedded in the conventional test equipment, so that the force value of the material in the whole test process can be directly obtained, but the equipment is not provided with a device capable of directly obtaining the change condition of the cross-sectional area of the material in the test process. In the test process, the tester can obtain parameters such as temperature, deformation, force value, stress value and the like of the material through corresponding sensors. One of the important parameters in the high-temperature tensile test data is a stress value, however, the device can accurately acquire the load force value which can only be borne by the sample, so that the cross-sectional area of the sample which changes along with the tensile process is difficult to acquire, especially when the sample is deformed unevenly in the high-temperature tensile process, the difficulty of acquiring the cross-sectional area of the sample is increased, and the stress is the ratio of the load force value to the corresponding cross-sectional area of the sample, so that the accurate measurement of the stress value in the tensile process is difficult to realize through the prior art. When researching the high temperature strength of a material and predicting the rolling force of a rolling mill, one method is to obtain material tensile test data by a high temperature tensile method, and based on the data, carrying out regression fit to obtain a stress-strain curve, and considering the influence of deformation rate and deformation temperature on rheological stress so as to obtain a high-precision rolling force prediction value. The traditional method has limitation on the measurement of the true stress strain curve all the time, so that the development of a method for measuring the true stress strain curve of a tensile experiment has very important significance. Disclosure of Invention The invention provides a method for determining a high-temperature tensile true stress strain curve, which is used for finding out the cross section area of a sample corresponding to a force value in a deformation process by analyzing the deformation characteristics of a material so as to effectively acquire the true stress strain curve of the material in the high-temperature tensile process. In order to achieve the above purpose, the invention is realized by adopting the following technical scheme: A method for determining a high-temperature tensile true stress strain curve comprises the following steps: s1, taking a rod-shaped tensile sample with a circular section for high-temperature tensile test, wherein the radius of the circular section of the sample is Length of ; S2, the force value corresponds to the elongation of the sample; Drawing a force time-varying curve under the same coordinate system according to the force value acquired by the experiment and the stretched length of the sample, and finding out the force value in the same time when the stretched length of the sample is time-varying curve and the time is the same Elongation of sample corresponding to the elongation ; S3, determining parameters before and after deformation of the high-temperature tensile sample; the tensile sample is broken into two sections through a high-temperature tensile experiment, and the total length of the two sections of samples is When the test piece is broken by stretching, the total elongation isThen ; Taking one of the two broken samples for analysis, and measuring the length of the necking area along the axial direction of the sample as , Part of the sample involved in deformation, original length 2 before deformationCalculated from the following formula: 2 ; s4, calculating the minimum cross-sectional area of the sample