Similarity evaluation model for the internal defect detection of strip steel

An internal defect meter is an instrument to detect the internal inclusion defects of cold-rolled strip steel.The detection accuracy of the equipment can be evaluated based on the similarity of the multiple detection data obtained for the same steel coil.Based on the cosine similarity model and eigenvalue matrix model,a comprehensive evaluation method to calculate the weighted average of similarity is proposed.Results show that the new method is consistent with and can even replace artificial evaluation to realize the automatic evaluation of strip defect detection results.

Comparison of Fuzzy Synthetic Evaluation and Field Measurement of Internal Defects in Assembled Concrete Detected by Ultrasonic Waves

Analyze and compare the basic principles of ultrasonic detection of voids in concrete,choose ZBL-U520/510 non-metallic ultrasonic detector,and use the opposite detection method to test the void size in the joints of prefabri-cated concrete structures.The results show that:ultrasonic method by testing the waveform,sound,and speed of sound analysis can effectively determine the position of the defect,and through the conversion formula can estimate the void size.Ultrasonic parameters are used to distinguish the internal defects of Assembly concrete.Sometimes there are diferent results with different para-meters.It is difficult for engineers to directly determine the internal de fects.Fuzzy comprehensive ev aluation can establish an overall evaluation of things or objects controlled by multiple factors by establishing membership functions.Through the inspection of engineering examples:the fuzzy comprehensive judgment method has no difference between the judgment of some good quality points and the judg-ment results of the original criteria,but for some abnormal points or points near the critical value,the advantages of fiuzzy criteria can be achieved.The judgment process will be more scientific by considering several parameters in a comprehen-sive manner and digtizing the original subjective judgments.

Internal Defect Measurement of Scattering Media by Optical Coherence Microscopy

Optical coherence microscopy is applied to measure scattering media'sinternal defect, which based on low coherence interferometry and confocal microscopy. Opticalcoherence microscopy is more effective in the rejection of out of focus and multiple scatteredphotons originating further away of the focal plane. With the three-dimension scanning, the internaldefect is detected by measuring the thickness of different points on the sample. The axialresolution is 6 μm and lateral resolution is 1. 2 μm. This method is possessed of the advantagesover the other measurement method of scattering media, such as non-destruction and high-resolution.

Effect of internal defects on tensile strength in SLM additively-manufactured aluminum alloys by simulation

This research investigates the effect of internal defects on the tensile strength of Selective Laser Melting(SLM)additively-manufactured aluminum alloy(AlSi10Mg)test parts used for civil aircraft light weight design.A Finite Element Analysis(FEA)model containing internal defects was established by combining test data and the stress concentration factor comparison method.The effect of variation in the number,location and shape of defects on the finite element results was analyzed.Its results show that it is reasonable to use spherical defect modeling.The finite element modeling and analysis methods are also applied to the study of the effect of internal defects on tensile strength in additive manufacturing of other metallic materials.According to the FEA results of single defects at different scales,the formula for calculating the weakening degree of tensile strength applicable to the defective area of less than 15%was established.The result of the procedure is reliable and conservative.This research results can guide the selection of process parameters for the additive manufacturing of aluminum alloys.Further,the research results can promote the application of metal additive manufacturing in designing light-weight civil aircraft structures.

Quality Control:Internal Defects Formation Mechanism of Selective Laser Melting Based on Laser-powder-melt Pool Interaction:A Review

Selective laser melting(SLM)is a 3D printing technology with a high near-net-shape ability and forming accuracy.However,the inevitable internal defects significantly hinder its development.Therefore,it is essential to fully understand the causes of internal defects in SLM processing and minimize the defects to achieve quality control accordingly.This work reviews the recent studies on internal defects in SLM,presenting the main internal defects of SLM as impurities,lack of fusion,gas pores,and micro-crack.These internal defects occur on the various phenomena in the laser-powder-melt pool(LPMP)stage.The formation of SLM internal defects is mainly affected by oxidation,denudation,balling,spatter,and keyholes;here,balling,spattering,and the keyhole phenomenon are the main factors causing internal defects in LPMP.Hence,this paper focuses on reviewing the balling effect,spatter behavior,and keyhole phenomenon,introducing the action mechanism of the above three phenomena under different process conditions.Additionally,the spatter behavior when forming internal defects is proposed.This review also considers the correlation between the spatter behavior and keyhole phenomenon and makes an important contribution to understanding and reducing SLM internal defects.It presents a reliable opinion on real-time monitoring and machine intelligent learning for SLM processing in the future,as well as supporting a systematic thinking for the suppression of defect formation in SLM.

Mango internal defect detection based on optimal wavelength selection method using NIR spectroscopy

A non-destructive technique should be developed for performance analysis of mango fruits because the spongy tissue or internal defects could lower the quality of mango fruit and incur a lack of productivity.In this study,wavelength selection methods were proposed to identify the range of wavelengths for the classification of defected and healthy mango fruits.Feature selection methods were adopted here to achieve a significant selection of wavelengths.To measure the goodness of themodel,the datasetwas collected using the NIR(Near Infrared)spectroscopy with wavelength ranging from 673 nm–1900 nm.The classification was performed using Euclidean distance measure both in the original feature space and in FLD(Fisher's Linear Discriminant)transformed space.The experimental results showed that the lower range wavelength(673 nm–1100 nm)was the efficient wavelength for the detection of internal defects in mangoes.Further to express the effectiveness of the model,different feature selection techniques were investigated and found that the Fisher's criterion based technique appeared to be the best method for effective wavelength selection useful for classification of defected and healthy mango fruits.The optimal wavelengths were found in the range of 702.72 nm to 752.34 nm using Fisher's criterionwith a classification accuracy of 84.5%.This study showed that NIR systemis a useful technology for the automaticmango fruit assessmentwhich has the potential to be used for internal defects in online sorting,easily distinguishable by those who do not meet minimum quality requirements.

Repair of oral mandibular defects with rib composite flap pedicled with internal thoracic

Objective To study feasibility and value of repair of oral mandibular defects with rib composite flap pedicled with internal thoracic vessels in basic level hospitals. Methods The clinical materials in 13 cases uith mandibular defects which were repaired with rib compos-

A Dynamics Study of a Magnetic Flux Leakage(MFL) Signal and its Application to Defect Location Discrimination in Steel Pipes MFL Testing Equipment

Difference processing was used to the direct current magnetic flux leakage （DC-MFL） signal, emanating from the defects machined artificially on the internal and external surfaces of a steel pipe. Consequently, the loea-tion discriminating index 8 was provided to identify the defect whether it is on the internal surface or the external one. Three characteristics, shape, depth and orientation of the defect, were discussed through a series of experiments on the artificial defects, such as transverse notches, oblique notches and pits on the steel pipe. The approach has been verified effective to address the defect location identifying problem, albeit the limits on the accuracy assessment to those natural defects on steel pipes in service.

Detection of a glass fiber-reinforced polymer with defects by terahertz computed tomography

Terahertz(THz)computed tomography(THz CT)exhibits the potential to provide a wealth of data,surpassing that of THz tomographic imaging in applications such as detecting embedded defects,particularly defect evolution within a glass fiber-reinforced polymer.To realize high-resolution THz CT,a systematic approach guided by wave propagation simulation was employed.First,the front wave of the THz beam was fine-tuned to realize a beam diameter of<2 mm.To mitigate the strong refractive effect and minimize Fresnel reflection loss,a refractiveindex-matching material was fabricated and utilized as a rounded enclosure for samples with sharp corners.To further improve the reconstruction resolution,a flat surface enclosure was applied to collect all incident beams at the detector.To realize comparable results to those of full-angle CT,a limited-angle CT approach was implemented,and the frequency range 0.1–3 THz was used in the image reconstruction study.The experimental and simulated images were used to validate the findings,and conductive and non-conductive defects measuring 200μm were successfully visualized.Additionally,a custom-built user interface enabled us to visualize the field spatial distribution of the THz beam with respect to frequency.

Fatigue Property of Additively Manufactured Ti-6Al-4V under Nonproportional Multiaxial Loading

The low cycle fatigue strength properties of the additively manufactured Ti-6Al-4V alloy are experimentally investi-gated under proportional and nonproportional multiaxial loading.The fatigue tests were conducted using hollow cylinder specimens with and without heat treatments,at room temperature in air.Two fatigue tests were conducted:one for proportional loading and one for nonproportional loading.The proportional loading was represented by a push-pull strain path(PP)and the nonproportional loading by a circle strain path(Cl).The failure lives of the additively manufactured specimens were clearly reduced drastically by internal voids and defects.However,the sizes of the defects were measured,and the defects were found not to cause a reduction in fatigue strength above a critical size.The fracture surface was observed using scanning electron microscopy to investigate the fracture mechanisms of the additively manufactured specimens under the two types of strain paths.Different fracture patterns were recognized for each strain paths;however,both showed retention of the crack propagation,despite the presence of numerous defects,probably because of the interaction of the defects.The crack propagation properties of the materials with numerous defects under nonproportional multiaxial loading were clarified to increase the reliability of the additively manufactured components.

Discrimination of brownheart of Korla pear using vibration frequency spectrum technique

The purpose of this work was to use a nondestructive method for detecting the brownheart of Korla pear to reduce the chance of infection among pears without brownheart.A mechanical impulse method based on vibration testing system was used to excite the fruits.The consistent acquisition signal indicated that the test is repeatable at the same positions of fruit equator(cheek).A remarkable frequency signal was excited at 9-12 N force by a rubber tipped hammer.The dominant frequency was identified at the maximum response magnitude to assess the internal defect,and the result was not influenced by the distances between the defect borders and the excitation points.The sharp increase of defect mass could significantly affect the dominant frequency.Relationship between the dominant response frequency(fd)and the defect mass percentage(ω)was characterized by an equation fd=410.649e-0.0833ω+261.947 with a good correlation coefficient(R2=0.925).A defect mass of 2.281%was determined as a discrimination threshold.Once the threshold exceeded 2.281%,the defective pear could be classified with a high accuracy rate of 96.7%.This finding would provide guidance for determining the optimal detecting time to the brownheart of Korla pears,according to the specific storage conditions when the vibration frequency spectrum method is deployed.

Application of a new reagent for analysis of oxygen presence in a lowcarbon steel wire rod

A microstructural analysis was performed to determine the presence of oxygen in a wire rod section of AISI 1008 steel with a surface mechanical failure produced during wire drawing.The failure zone was analyzed by comparison using three different attack reagents:alkaline sodium chromate(ASC),ASC with hydrogen peroxide and amyl alcohol,and a solution of nitric acid in ethyl alcohol.The reagents were applied in samples in the failure zone,showing different types of zones in regions with internal and superficial defects such as carbides,pores,cracks,deformation,and detachment zones,indicating the possible presence of oxygen.The areas identified were observed by means of an optical microscope and were correlated with the content of elements that were present in the region using a scanning electron microscope and a scattered X-ray energy spectrometer,which determined that the areas identified by chromate sodium correspond to regions with a high concentration of oxygen and slag-forming elements such as silicon,aluminum,and iron;this is associated with the presence of oxygen in the oxide form.It was also observed that the ASC and the modified ASC solution with hydrogen peroxide and amyl alcohol could identify areas with a high presence of oxides,while the nitric acid solution only identified the steel microstructure.The modified ASC solution is an alternative to identify the presence of chemical variants of oxygen because the conventional formulation is unstable and has a too short shelf life,and therefore,its application must be carried out at the time of preparation.