The laser powder bed fusion(L-PBF)method of additive manufacturing(AM)is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts.However,the parts ...The laser powder bed fusion(L-PBF)method of additive manufacturing(AM)is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts.However,the parts produced by L-PBF usually contain such defects as crack and porosity because of the technological characteristics of L-PBF,which affect the quality of the product.Laser ultrasonic testing(LUT)is a potential technology for on-line testing of the L-PBF process.It is a non-contact and non-destructive approach based on signals from abundant waveforms with a wide frequency-band.In this study,a method of LUT for on-line inspection of L-PBF process was proposed,and a system of LUT was established approaching the actual environment of on-line detection to evaluate the method applicability for defects detection of L-PBF parts.The detection results of near-surface defects in L-PBF 316L stainless steel parts show that the crack-type defects with a sub-millimeter level within 0.5 mm depth can be identified,and accordingly,the positions and dimensions information can be acquired.The results were verified by X-ray computed tomography,which indicates that the present method exhibits great potential for on-line inspection of AM processes.展开更多
The objective of this paper was to evaluate the sugar and water content in sugar cane samples by means of twonon-destructive techniques in comparison with conventional methods. One non-destructive technique is the Bio...The objective of this paper was to evaluate the sugar and water content in sugar cane samples by means of twonon-destructive techniques in comparison with conventional methods. One non-destructive technique is the Biospeckle, aninteraction between the laser and the biological material which provides information about the material. The other technique is thenear infrared spectroscopy （NIR）. The Biospeckle technique has been constantly used in agricultural engineering. In this paper, therelation between the water and the sugar contents were obtained. The results for the Biospeckle were acquired through the moment ofinertia （MI）. The data acquired through already consolidated methodologies were used to quantify the samples＇ water and sugarcontents, correlating to the spectroscopy results and also to the Biospeckle. It was obtained a high determination coefficient （R^2 =0.9287） between the predicted Brix by the model generated by NIR spectroscopy and Brix measured by refractometer. It was alsopossible to differentiate the water contents of the sugar cane samples both externally lit （husk） and internally lit （cut） by Biospeckleanalysis through the calculation of MI. It is possible to evaluate the water content and the sugar content in samples combiningBiospeckle and NIR spectroscopy, which are non-invasive and non-destructive methods.展开更多
Composite materials are increasingly used in the aerospace industry.To fully realise the weight saving potential along with superior mechanical properties that composites offer in safety critical applications,reliable...Composite materials are increasingly used in the aerospace industry.To fully realise the weight saving potential along with superior mechanical properties that composites offer in safety critical applications,reliable Non-Destructive Testing(NDT)methods are required to prevent catastrophic failures.This paper will review the state of the art in the field and point to highlight the success and challenges that different NDT methods are faced to evaluate the integrity of critical aerospace composites.The focus will be on advanced certificated NDT methods for damage detection and characterization in composite laminates for use in the aircraft primary and secondary structures.展开更多
Holographic methods for non-destructive testing,shape measurement,and experimental stress analysis have shown to be versatile tools for the solution of many inspection problems.Their main advantages are the non-contac...Holographic methods for non-destructive testing,shape measurement,and experimental stress analysis have shown to be versatile tools for the solution of many inspection problems.Their main advantages are the non-contact nature,the non-destructive and areal working principle,the fast response,high sensitivity,resolution and precision.In contrast to conventional optical techniques such as classical interferometry,the holographic principle of wavefront storage and reconstruction makes it possible to investigate objects with rough surfaces.Consequently,the response of various classes of products on operational or artificial load can be examined very elegantly.The paper looks back to the history of holographic metrology,honors the inventors of the main principles,discusses criteria for the selection of a proper inspection method,and shows exemplary applications.However,the main focus is on modern developments that are inspired by the rapid technological process in sensing technology and digitization,on current applications and future challenges.展开更多
Surface roughness is commonly used to characterize material microstructure during processing,and accurate measurement of surface roughness is the premise and foundation of machining.Therefore,online non-destructive me...Surface roughness is commonly used to characterize material microstructure during processing,and accurate measurement of surface roughness is the premise and foundation of machining.Therefore,online non-destructive measurement of surface roughness based on the laser speckle method has become a hot issue in recent research.The improvements in surface roughness measurements based on the laser speckle method are systematically reviewed.Theory of speckle formation is introduced.The statistical properties of the speckle patterns including first-order statistical properties and second-order statistical properties are directly related to surface roughness.Surface roughness measurements based on the laser speckle method are roughly divided into the speckle contrast method,speckle correlation method,and fractal method.The three methods are described in detail,and an extensive comparison among all the methods is presented.The recent progresses and application of surface roughness measurements are reviewed.Finally,surface roughness measurements based on the laser speckle method are prospected and summarized.展开更多
This paper presents the activities in the field of shearography in chronological order and highlights the great potential of this holographic measurement technology.After a brief introduction,the basic theory of shear...This paper presents the activities in the field of shearography in chronological order and highlights the great potential of this holographic measurement technology.After a brief introduction,the basic theory of shearography is presented.Shear devices,phase-shift arrangements,and multiplexed shearography systems are described.Finally,the application areas where shearography has been accepted and successfully used as a tool are presented.展开更多
基金the National Key R&D Program of China(Grant No.2018YFB1106100)。
文摘The laser powder bed fusion(L-PBF)method of additive manufacturing(AM)is increasingly used in various industrial manufacturing fields due to its high material utilization and design freedom of parts.However,the parts produced by L-PBF usually contain such defects as crack and porosity because of the technological characteristics of L-PBF,which affect the quality of the product.Laser ultrasonic testing(LUT)is a potential technology for on-line testing of the L-PBF process.It is a non-contact and non-destructive approach based on signals from abundant waveforms with a wide frequency-band.In this study,a method of LUT for on-line inspection of L-PBF process was proposed,and a system of LUT was established approaching the actual environment of on-line detection to evaluate the method applicability for defects detection of L-PBF parts.The detection results of near-surface defects in L-PBF 316L stainless steel parts show that the crack-type defects with a sub-millimeter level within 0.5 mm depth can be identified,and accordingly,the positions and dimensions information can be acquired.The results were verified by X-ray computed tomography,which indicates that the present method exhibits great potential for on-line inspection of AM processes.
文摘The objective of this paper was to evaluate the sugar and water content in sugar cane samples by means of twonon-destructive techniques in comparison with conventional methods. One non-destructive technique is the Biospeckle, aninteraction between the laser and the biological material which provides information about the material. The other technique is thenear infrared spectroscopy （NIR）. The Biospeckle technique has been constantly used in agricultural engineering. In this paper, therelation between the water and the sugar contents were obtained. The results for the Biospeckle were acquired through the moment ofinertia （MI）. The data acquired through already consolidated methodologies were used to quantify the samples＇ water and sugarcontents, correlating to the spectroscopy results and also to the Biospeckle. It was obtained a high determination coefficient （R^2 =0.9287） between the predicted Brix by the model generated by NIR spectroscopy and Brix measured by refractometer. It was alsopossible to differentiate the water contents of the sugar cane samples both externally lit （husk） and internally lit （cut） by Biospeckleanalysis through the calculation of MI. It is possible to evaluate the water content and the sugar content in samples combiningBiospeckle and NIR spectroscopy, which are non-invasive and non-destructive methods.
基金the support of NVIDIA Corporation with the donation of the Titan Xp GPU used for this researchsupported by EPSRC grant EP/R002495/1the European Metrology Research Programme through grant 17IND08。
文摘Composite materials are increasingly used in the aerospace industry.To fully realise the weight saving potential along with superior mechanical properties that composites offer in safety critical applications,reliable Non-Destructive Testing(NDT)methods are required to prevent catastrophic failures.This paper will review the state of the art in the field and point to highlight the success and challenges that different NDT methods are faced to evaluate the integrity of critical aerospace composites.The focus will be on advanced certificated NDT methods for damage detection and characterization in composite laminates for use in the aircraft primary and secondary structures.
文摘Holographic methods for non-destructive testing,shape measurement,and experimental stress analysis have shown to be versatile tools for the solution of many inspection problems.Their main advantages are the non-contact nature,the non-destructive and areal working principle,the fast response,high sensitivity,resolution and precision.In contrast to conventional optical techniques such as classical interferometry,the holographic principle of wavefront storage and reconstruction makes it possible to investigate objects with rough surfaces.Consequently,the response of various classes of products on operational or artificial load can be examined very elegantly.The paper looks back to the history of holographic metrology,honors the inventors of the main principles,discusses criteria for the selection of a proper inspection method,and shows exemplary applications.However,the main focus is on modern developments that are inspired by the rapid technological process in sensing technology and digitization,on current applications and future challenges.
基金This work was supported by the National Key Research and Development Plan(Grant No.2020YFB1713600)Xinjiang Science and Technology Assistance Program(Grant No.2021E02060)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-20-105A1 and FRF-TP-19-002A3)National Natural Science Foundation of China(Grant No.51975043)the China Postdoctoral Science Foundation(Grant No.2021M69035)。
文摘Surface roughness is commonly used to characterize material microstructure during processing,and accurate measurement of surface roughness is the premise and foundation of machining.Therefore,online non-destructive measurement of surface roughness based on the laser speckle method has become a hot issue in recent research.The improvements in surface roughness measurements based on the laser speckle method are systematically reviewed.Theory of speckle formation is introduced.The statistical properties of the speckle patterns including first-order statistical properties and second-order statistical properties are directly related to surface roughness.Surface roughness measurements based on the laser speckle method are roughly divided into the speckle contrast method,speckle correlation method,and fractal method.The three methods are described in detail,and an extensive comparison among all the methods is presented.The recent progresses and application of surface roughness measurements are reviewed.Finally,surface roughness measurements based on the laser speckle method are prospected and summarized.
文摘This paper presents the activities in the field of shearography in chronological order and highlights the great potential of this holographic measurement technology.After a brief introduction,the basic theory of shearography is presented.Shear devices,phase-shift arrangements,and multiplexed shearography systems are described.Finally,the application areas where shearography has been accepted and successfully used as a tool are presented.
