CN105574306A - Method for obtaining theoretical strain in strength finite element analysis - Google Patents

Abstract

The invention provides a method for obtaining theoretical strain in strength finite element analysis. The method is characterized by comprising the following steps: (1) according to a finite element principle and a strain sensor measurement principle, establishing an additional bar element according to any given position and direction in the finite element model of a test specimen; (2) in order to prevent the additional bar element from affecting local structural stress and strain distribution characteristics, requiring to define that bar element stiffness characteristics are infinitesimal relative to the local structural stiffness characteristics; and (3) after analysis and solution are carried out, directly reading bar element strain in a result, wherein the strain is theoretical strain under any given position and direction.

Description

A Method of Obtaining Theoretical Strain in Strength Finite Element Analysis

technical field

The invention belongs to the field of strength finite element analysis and test verification, and relates to a method for obtaining theoretical strain in strength finite element analysis.

Background technique

The use of finite element method in strength analysis is becoming more and more extensive and in-depth, and the mutual verification of strength test and finite element analysis is becoming more and more common. In strength test, it is usually necessary to measure the strain at a given position and direction in the test piece through a strain sensor; by comparing The correctness of the finite element analysis or test is judged by the difference between the strain of the test piece and the strain corresponding to the position and direction in the finite element analysis, so the acquisition of the strain corresponding to the position and direction in the finite element analysis is particularly important.

In the past, the following steps were required to obtain the strain at a given position and direction in finite element analysis: first, determine the position and direction of the strain sensor in the test according to the analysis results, and then divide the finite element model according to the position and direction of the strain sensor in the test, Then establish a local coordinate system for the segmented area according to the direction of the strain sensor, and give the segmented area a direction in the established coordinate system, then follow the normal steps to solve it, and finally read it in the coordinate system corresponding to each segmented area Take the strain, which is the theoretical strain at the strain sensor in the test piece.

The cumbersomeness of the above method lies in that it is necessary to divide the test piece in a complex situation multiple times, define the coordinate system multiple times, and assign directions to the segmented area multiple times, and the strain at a certain position must be read in its corresponding coordinate system.

Contents of the invention

The purpose of the invention is to provide a method for obtaining theoretical strain in strength finite element analysis

The technical solution of the present invention is: a method for obtaining theoretical strain in strength finite element analysis, comprising the following steps:

Step 1: According to the finite element principle and the measurement principle of the strain sensor, an additional rod element is established according to the given arbitrary position and direction in the finite element model of the test piece;

Step 2: In order to ensure that the additional rod elements do not affect the local structural stress and strain distribution characteristics, it is necessary to define that the stiffness characteristics of the rod elements are infinitely small relative to the local stiffness characteristics of the structure;

Step 3: After analyzing and solving, directly read the rod element strain in the result, which is the theoretical strain at any given position and direction.

The advantage of the present invention is: the method of the present invention uses the additional rod element to simulate the strain sensor, compared with the previous steps: establishing the finite element model——dividing and dividing the area—establishing the local coordinate system—giving the material direction—analyzing and solving—in the local Reading the theoretical strain in the coordinate system greatly simplifies the steps of obtaining the theoretical strain, the principle is simple and clear, and it is easy to operate.

Description of drawings

Figure 1 is a local grid diagram of the finite element model of the test piece;

Fig. 2 is the local grid diagram of the finite element model after the rod element is added to the test piece;

detailed description

The present invention will be described in further detail below in conjunction with accompanying drawing, please refer to Fig. 1 to Fig. 2.

As shown in Figure 1, it is the local mesh diagram of the finite element model of the test piece;

As shown in Figure 2, in the finite element model of the test piece, the additional rod elements are established according to the given arbitrary position and direction, numbered from No. 1 to No. 15;

A method for obtaining theoretical strain in strength finite element analysis, comprising the following steps:

Step 1: According to the finite element principle and the measurement principle of the strain sensor, an additional rod element is established according to the given arbitrary position and direction in the finite element model of the test piece;

Step 2: Define the stiffness characteristics of the rod element to be infinitely small relative to the local stiffness characteristics of the structure;

Step 3: After analyzing and solving, directly read the rod element strain in the result, which is the theoretical strain at any given position and direction.

The advantage of the present invention is: the method of the present invention uses the additional rod element to simulate the strain sensor, compared with the previous steps: establishing the finite element model——dividing and dividing the area—establishing the local coordinate system—giving the material direction—analyzing and solving—in the local Reading the theoretical strain in the coordinate system greatly simplifies the steps of obtaining the theoretical strain, the principle is simple and clear, and it is easy to operate.

Claims (2)

1. A method for obtaining theoretical strain in strength finite element analysis, is characterized in that, comprises the following steps: (1) According to the finite element principle and the measurement principle of the strain sensor, an additional rod element is established according to a given arbitrary position and direction in the finite element model of the test piece; (2) In order to prevent the additional rod elements from affecting the local structural stress and strain distribution characteristics, it is necessary to define that the stiffness characteristics of the rod elements are infinitesimally small relative to the local stiffness characteristics of the structure; (3) After analyzing and solving, directly read the rod element strain in the result, which is the theoretical strain at any given position and direction. 2. the method for obtaining theoretical strain in strength finite element analysis according to claim 1, is characterized in that, in step 1, establishes additional rod element specifically: given arbitrary position and direction in the finite element model of test piece Select two nodes in the axial direction of the strain sensor, and use these two nodes to establish the rod element.