CN112729634A

CN112729634A - Stress rapid detection method for laser additive manufacturing alloy steel member

Info

Publication number: CN112729634A
Application number: CN202011512323.0A
Authority: CN
Inventors: 段成红; 张银洲; 陈辉; 陈勇; 罗翔鹏
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2020-12-19
Filing date: 2020-12-19
Publication date: 2021-04-30

Abstract

The invention discloses a stress rapid detection method for a laser additive manufacturing alloy steel member, the laser additive manufacturing alloy steel member has residual stress due to a manufacturing mode, the residual stress is very necessary to be measured, the analysis of X-ray diffraction residual stress has long been developed, and sin is mainly used²Psi method and cos alpha method, the residual stress of the surface of the alloy steel component manufactured by laser additive manufacturing is mainly concentrated on the residual stress along the scanning speed and the scanning speed which is vertical to the scanning speed, the residual stress on the forming height is small, the X-ray diffraction cos alpha method can better test the residual stress of a plane stress state, and the cos alpha method is compared with sin alpha method²The psi method is high in detection speed, and can be applied to the field of laser additive manufacturing.

Description

Stress rapid detection method for laser additive manufacturing alloy steel member

Technical Field

The invention relates to a residual stress measurement technology, in particular to a stress rapid detection method for a laser additive manufacturing alloy steel member.

Background

Laser additive manufacturing is receiving great attention and developing rapidly worldwide as a revolutionary leading technology in the manufacturing field. As an advanced manufacturing technology, the laser additive manufacturing technology combines the technologies of computer aided design, material forming processing and the like, and solid metal products are manufactured by sintering, melting and the like. Different from the traditional manufacturing mode of material reduction (cutting and the like), the laser additive manufacturing is a manufacturing method of layer-by-layer accumulation forming of metal materials, so that the development period of products can be shortened, the efficiency is improved, and the cost is reduced.

However, in the laser additive manufacturing process, the manufactured part has large residual stress, which greatly affects the performance of the material, and the residual stress is usually reduced by heat treatment and the like after the manufacturing process is completed, so that the residual stress is very necessary to be measured. In the technique of measuring residual stress, sin in X-ray diffraction method is generally adopted at present²The psi method generally requires fitting ellipses with diffraction peak values of more than 9 psi angles to calculate stress values, the required steps are complex and long in time, the cos alpha method in the X-ray diffraction method can calculate the stress values by utilizing a debye ring for one-time measurement, but the quality acquired by the debye ring influences the accuracy of the stress values.

At present, the rapid detection of the residual stress of a laser additive manufacturing part has very important significance for the engineering application of the additive manufacturing part.

Disclosure of Invention

Aiming at the problem that the existing laser additive manufacturing steel member cannot be completely applied in engineering practice, the invention aims to provide a method for rapidly detecting the stress of the laser additive manufacturing alloy steel member, which can rapidly detect the stress of the additive manufacturing steel member under the condition of ensuring the precision and accelerate the research period of the additive manufacturing steel member. According to the stress rapid detection method for the laser additive manufacturing alloy steel member, the residual stress exists in the laser additive manufacturing alloy steel member due to the manufacturing mode, the residual stress is very necessary to be measured, the analysis of the X-ray diffraction residual stress is long-developed, and sin is mainly used²Psi method and cos alpha method, the residual stress of the surface of the alloy steel component manufactured by laser additive manufacturing is mainly concentrated on the scanning speed and the scanning speed which are vertical to the scanning speed, the residual stress on the forming height is small, and the X-ray diffraction cos alpha method can better test the plane stress stateResidual stress, cos alpha method compared to sin²The psi method is high in detection speed, and can be applied to the field of laser additive manufacturing.

The method is based on a cos alpha method in an X-ray diffraction method, and can be used for rapidly detecting the stress of additive manufacturing under the condition of ensuring the precision.

The technical scheme of the invention is as follows:

a stress rapid detection method for a laser additive manufacturing alloy steel member comprises an X-ray tube, a goniometer, a flat panel detector, a displacement sensor, a workbench, a microcomputer and a stabilized voltage power supply; the X-ray tube, the angle gauge, the flat panel detector and the displacement sensor are integrated in the measuring head, the X-ray tube, the flat panel detector and the displacement sensor are positioned inside the measuring head, and the goniometer is positioned at the upper part of the displacement sensor; the X-ray tube emits X-rays which penetrate through a central hole of the flat panel detector and irradiate the additive manufacturing sample, the flat panel detector can detect an X-ray diffraction peak, the position of the measuring head is adjusted by using the goniometer and the displacement sensor, meanwhile, the quality of the diffraction peak on the microcomputer is observed, and the microcomputer is used for calculating stress; the method comprises the following specific steps:

firstly, determining a laser scanning direction X, a laser scanning direction Y perpendicular to the laser scanning direction and a forming direction Z for manufacturing a sample of an additive manufactured part;

placing an additive manufacturing sample on a workbench, wherein an XOY surface of the additive manufacturing sample is placed in parallel to a workbench surface, and polishing the surface of the additive manufacturing sample;

step (3) placing the measuring head and an XOY plane of the additive manufacturing sample at a certain angle, adjusting the relative position of the additive manufacturing sample and the measuring head through a goniometer and a displacement sensor, detecting a diffraction peak by using a flat panel detector, observing the quality of the diffraction peak, and determining a better position; the resulting debye loop was processed by software, and the stress was calculated from the debye loop by cos α method in X-ray diffraction method.

The distance between the measuring head and the material increase manufacturing sample is rapidly adjusted through the displacement sensor, and then an X-ray diffraction peak with good quality is obtained.

The material of the X-ray tube anode target is Cr, V, Cu, Co, Mn and other metals, and the X-ray tube parameters are 30Kv and 1.5 mA; the manual control of the workbench X, Y, Z three-dimensional directional motion is realized.

The invention aims to quickly detect the stress of a laser additive manufacturing alloy steel member based on the stress characteristic of an additive manufacturing member and a cos alpha method in an X-ray diffraction method, and quickly obtain a Debye ring with better quality through a goniometer and a displacement sensor aiming at the defect of the cos alpha method, thereby improving the accuracy of a stress value.

Drawings

Fig. 1 is a schematic view of the measurement of the apparatus.

FIG. 2 is a schematic diagram of cos α method.

Detailed Description

The scheme of the invention is further detailed in the following by combining the drawings and the embodiment:

the method for measuring the stress of the alloy steel component manufactured by the laser additive based on the X-ray diffraction method is based on a cos alpha method in the X-ray diffraction method, and the key point is how to quickly adjust the distance between a measuring head and an additive manufacturing sample to obtain a high-quality Debye ring.

Examples

(1) Preparation of additive manufacturing samples

The invention firstly utilizes the research result of a laboratory subject group, the selected powder material is 12CrNi2, and the processing technology is shown in the following table:

a 40mm by 20mm by 10mm (X by Y Z) additive manufacturing sample was printed and the surface treated.

(2) Adjustment of device position

The schematic diagram of the device measurement is shown in fig. 1, and the sample is firstly placed on the working platform, the measuring head of the device is placed at a certain angle with the working platform, and the proper position is adjusted by the goniometer and the displacement sensor to ensure that the debye ring with good quality is obtained.

(3) Measurement of stress

The cos α method utilizes a principle diagram of the Debye ring for stress measurement as shown in FIG. 2, and the stress can be calculated by combining equations (1) to (3).

Wherein psi₀The angle between an X ray and an additive manufacturing sample is shown, 2 eta is the angle between the X ray and an X ray diffraction line, 2 theta is the complementary angle of 2 eta, alpha is the angle between a Debye ring under stress and the Debye ring under no stress, E is the elastic modulus of the material, and v is the Poisson ratio of the material.

Claims

1. A stress rapid detection method for a laser additive manufacturing alloy steel member comprises an X-ray tube, a goniometer, a flat panel detector, a displacement sensor, a workbench, a microcomputer and a stabilized voltage power supply; the X-ray tube, the angle gauge, the flat panel detector and the displacement sensor are integrated in the measuring head, the X-ray tube, the flat panel detector and the displacement sensor are positioned inside the measuring head, and the goniometer is positioned at the upper part of the displacement sensor; the X-ray tube emits X-rays which penetrate through a central hole of the flat panel detector and irradiate the additive manufacturing sample, the flat panel detector can detect an X-ray diffraction peak, the position of the measuring head is adjusted by using the goniometer and the displacement sensor, meanwhile, the quality of the diffraction peak on the microcomputer is observed, and the microcomputer is used for calculating stress; the method is characterized in that: the method comprises the following specific steps:

2. The method for rapidly detecting the stress of the laser additive manufacturing alloy steel component according to claim 1, is characterized in that: and (3) quickly adjusting the distance between the measuring head and the additive manufacturing sample through a displacement sensor, and further obtaining an X-ray diffraction peak.

3. The method for rapidly detecting the stress of the laser additive manufacturing alloy steel component according to claim 1, is characterized in that: the material of the X-ray tube anode target is Cr, V, Cu, Co and Mn metal, and the X-ray tube parameters are 30Kv and 1.5 mA.

4. The method for rapidly detecting the stress of the laser additive manufacturing alloy steel component according to claim 1, is characterized in that: the manual control of the workbench X, Y, Z three-dimensional directional motion is realized.