CN104198576A

CN104198576A - Device for rapidly detecting inner crack of metal bent component

Info

Publication number: CN104198576A
Application number: CN201410461650.6A
Authority: CN
Inventors: 张卫民; 邱忠超; 杨秀江; 果艳; 秦峰
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2014-09-11
Filing date: 2014-09-11
Publication date: 2014-12-10

Abstract

The invention relates to a novel sensor structural device for rapidly detecting an inner longitudinal crack flaw of a metal plate bent component. Metal plate bending belongs to one common machining mode, such as the processing of a vehicle oil tank container. As the bent part is subjected to excessive plastic deformation and various load actions, the crack easily occurs in the bending longitudinal direction. As the crack usually first occurs on the inner wall of the container, the crack is difficult to find by a common detection method. The invention provides a sensor detector utilizing flux leakage non-destructive detecting principles. The sensor detector is specially used for the site rapid detection of the internal crack of the metal bent component and is expected to well solve the problem. A special guide wheel mechanism is adopted in the sensor to ensure that the detector scans along the bent part. A forced excitation device is adopted to enhance flux leakage signals at flaw parts. A differential hall element detector is adopted to improve the detecting sensitivity. When no crack exists at the bent part, the output signal amplitude of the detector is basically constant. When the crack exists at the bent part, the output signal amplitude of the detector changes. The detecting method is rapid and simple, can realize non-contact detection, does not need to pre-process a to-be-detected object and is convenient for site use.

Description

The device for fast detecting of metal folding part underbead crack

Technical field

The invention belongs to magnetic nondestructive testing field, relate to a kind of Rapid non-destructive testing device designing for detecting the inner longitudinal crack producing of sheet metal bending.Can be used for the container products such as fuel tank along in the defect eddy detection technology of bending part metal material, is the defects detection of engineering structure, and a kind of novel sensor scheme is provided.

Background technology

The bending of sheet metal belongs to cold plasticity process, is usually used in the machining of the canister that bearing requirements is not high, in the processing of oil tank of vehicle.Because bending part often exists compared with large plastometric set, remaining higher residual stresses, under alternate load effect, often causes crackle to occur during work, and then produces cracking.If crackle, in the inner generation of chamber wall, causes potential faults, at external container, be difficult to find, common detection method is difficult to prove effective, if adopt the methods such as industry CT, is unsuitable for again the Site Detection under environment for use.

The defects such as the fatigue crack of metal material, are to affect equipment life and safe key factor, and the defect of load-carrying member is carried out to Non-Destructive Testing, are important contents of modern mechanical manufacturing.Due to the defect of practical structures, its position and direction are unforeseen.While utilizing traditional eddy current sensor to detect, owing to there is detection sensitivity difference, when crackle is when detecting non-sensitive direction, easily produce undetected.

The object of the invention is to, for detecting the generation of sheet metal bending part underbead crack, provides a kind of fast and convenient device can be used under on-the-spot environment for use, the basic functional principle of the principle of invention based on Nondestructive detection with magnetic flux leakage.

Summary of the invention

Sensor detecting device of the present invention is formed by following structures: exciting bank, and detecting sensor, sampling wheel mechanism, as shown in Figure 1.Excitation part is comprised of iron core 1 and the armature 2 of two coil windings, during work, form closed magnetic circuit together with test specimen, the direct current that passes to 6V produces ac magnetization effect to test specimen, while there is no defect in test specimen, the magnetic line of force passes through from test specimen inside, while there is defects i.e.cracks in test specimen, because magnetic resistance increases, the part magnetic line of force is leaked in air by fault location, by sensor, detected, thus the defect of detecting.For guaranteeing that pick-up unit carries out scanning along bending part, exciting bank iron core bottom design becomes V-type shape, as shown in Figure 2.Make device in excitation simultaneously, play guide effect, scanning that assurance pick-up unit can " be ridden rib ".Detecting sensor is arranged along scanning direction by two mini Hall elements, forms difference structure, to improve the ability of detection sensitivity and inhibition noise.Detecting sensor 4 forms (seeing Fig. 3) by two Hall sensor element that form difference structure, and the object of difference structure is in order to improve detection sensitivity, offsets random noise disturbance.Pick-up unit afterbody is provided with friction sampling wheel 5, can adjust position in certain limit, to realize with the reliable of test specimen, contacts, and by the photoelectric encoder 6 of coaxial connection, realizes signal Space domain sampling, records the position that crackle occurs.

Fig. 4 is detecting sensor subsequent process circuit figure, the voltage signal of two-way Hall element output, first by AD620 chip, carry out elementary amplification, adopt afterwards the passive low-pass filtering link of secondary filter away high frequency noise, then through UA741 chip, carry out secondary amplification, last two paths of signals carries out differential amplification.Fig. 5 is circuit pictorial diagram.

Beneficial effect:

The present invention has designed a kind of device for fast detecting that detects metal folding part underbead crack, can realize the underbead crack generation that internal tank causes because of metal folding plastic yield, this pick-up unit is easy to use, loose to environmental requirement, can be used for using on-the-spot non-disassembly, there is important engineering practical value.

Accompanying drawing explanation

Fig. 1: four bed device structural drawing.

In figure: 1-magnetic excitation coil, 2-yoke, 3-exciting bank iron core bottom V-block, 4-detecting sensor, 5-friction sampling wheel, 6-photoelectric encoder.

Fig. 2: exciting bank iron core bottom V-block partial enlarged drawing.

Fig. 3: detecting sensor pictorial diagram.

Fig. 4: detecting sensor circuit theory diagrams.

Fig. 5: detecting sensor circuit pictorial diagram.

Fig. 6: pick-up unit pictorial diagram.

Fig. 7: certain heavy armored vehicle is through the fuel tank container of metal folding processing.

Fig. 8: the metal folding part exemplar that has crack defect.

Fig. 9: the genetic defects signal that filtered ripple is processed.

Figure 10: the flaw indication after processing after filtering.

Embodiment

For objects and advantages of the present invention are described better, below in conjunction with the drawings and specific embodiments, the present invention will be further described.

Fig. 7 is certain Armoured Vehicle, Heavy with fuel tank, and because material and technique exist some problems, bending part often produces underbead crack, exist cracking, leakage of oil dangerous with fuel tank, needs to strengthen detecting at present.

Fig. 8 is the inner actual exemplar that has crackle.Crack length is about 40 mm, width 0.5mm, and the degree of depth is about 0.5mm.

Sensor is moved along test specimen bending seamed edge length direction, friction sampling wheel is close to test specimen, guarantee its friction rolling, at defective locations, can observe signal amplitude undergos mutation, as shown in Figure 9, signal, by further processing such as low-pass filters, is got final product to the clear flaw indication that extracts, as shown in figure 10.

The present embodiment only detects for a kind of test specimen of material.The present invention can detect multiple conductive material, and wire circle of sensor, wire diameter etc. can be adjusted.

Claims

1. the sensor construction device for the inner longitudinal crack defect of sheet metal bending part fast detecting, it is characterized in that: adopt excitation and guide effect in the exciting bank of one, to adapt to the testing requirement of bending part, adopt the Hall element of difference structure, to increase detection sensitivity, meet the needs that detect inner embed crack, sampling runner is installed on device, to record crackle, produce position.

2. exciting bank adopts two iron cores that are wound with lattice coil to form, excitation unit and test specimen form closed magnetic circuit, produce arousal effect, iron core is characterised in that: V font is made in bottom, to adapt to the detection needs of bending part, by adjusting V-shape angle, can adapt to effective detection of different angles bending part, when realizing incentive action, have guide effect concurrently.

3. this sensor device test section, is characterized in that: by two Hall elements, along device moving direction cloth, become difference structure mode, to offset noise, improve detection sensitivity.

4. pick-up unit rear portion is provided with the friction runner of adjustable position, is coaxially connected with photoelectric encoder, to realize the spatial sampling in testing process, records the defective locations in testing process.