检索结果-南通市图书馆

无损检测 1995年第10期17卷 271-273,282页

作者：刘松平陈积懋北京航空工艺研究所复合材料ndt&E中心 100024

利用射频超声技术检测大密度金属钎焊蜂窝构件及缺陷识别技术。

关键词：超声检测钎焊蜂窝结构缺陷识别

Identifying the crystal structure of T 1 precipitates in Al-Li-Cu alloys by ab initio calculations and HAADF-STEM imaging

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Journal of Materials Science & Technology 2023年第2期133卷 41-57页

作者： Shuo Wang Xianghai Yang Junsheng Wang Chi Zhang Chengpeng Xue School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China

Controversial experimental reports on the crystal structure of T 1 precipitates in Al-Li-Cu alloys have ex-isted for a long time,and all of them can be classified into five *** clarify its ground-state atomic structure,herein,we have combined high-throughput first-principles calculations and CALPHAD,as well as aberration-corrected HAADF-STEM *** the special quasi-random structure(sqs)and supercell approximation(SPA)methods to simulate the local disorder on Al-Cu sub-lattices,we find that none of the present models can satisfy the phase stability in Al-Li-Cu ternary system based on temperature-dependent convex hull *** the cluster expansion(CE)formulas,structural predic-tions derived from the five-frame models were ***,by introducing the vibrational contribution to the free energy at aging temperatures,we proposed a novel ground-state T 1 structure that maintains a coherent relationship with Al-matrix at theAl *** underlying phase transition between the variants of T 1 precipitates was further *** means of ab initio molecular dynamics(AIMD)simulations,we resolved the controversy regarding the number of atomic layers con-stituting the T 1 phase and acknowledged the existence of Al-Li corrugated *** root cause of this structural distortion is triggered by atomic forces and *** work can have an positive impact on the novel fourth generation of Al-Cu-Li alloy designs by engineering the T 1 strengthening phase.

关键词： Al-Cu-Li alloys T 1 precipitates Cluster expansion First-principle calculations ab initio molecular dynamics HAADF-STEM

Concrete damage diagnosed using the non-classical nonlinear acoustic method

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Chinese Physics B 2009年第5期18卷 1898-1905页

作者：周到刘晓宙龚秀芬 Nazarov V E 马力 Key Laboratory of Modern Acoustics Ministry of EducationInstitute of AcousticsNanjing University institute of Applied Physics Russian Academy of ScienceRussian Federation institute of Acoustics Chinese Academy of Sciences

It is known that the strength of concrete is seriously affected by damage and cracking. In this paper, six concrete samples under different damage levels are studied. The experimental results show a linear dependence of the resonance frequency shift on strain amplitude at the fundamental frequency, and approximate quadratic dependence of the am- plitudes of the second and third harmonics on strain amplitude at the fundamental frequency as well. In addition, the amplitude of the third harmonics is shown to increase with the increase of damage level, which is even higher than that of the second harmonics in samples with higher damage levels. These are three properties of non-classical nonlinear acoustics. The nonlinear parameters increase from 106 to 108 with damage level, and are more sensitive to the damage level of the concrete than the linear parameters obtained by using traditional acoustics methods. So, this method based on non-classical nonlinear acoustics may provide a better means of non-destructive testing （ndt） of concrete and other porous materials.

关键词： concrete non-classical nonlinear acoustics non-destructive testing (ndt) crack

AN INTERPRETATION OF THE FORMATION OF SELF-QUENCHING STREAMER

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Chinese Science Bulletin 1986年第8期31卷 515-519页

作者：张良生 institute of High Energy Physics Academia Sinica Beijing mechanism for explaining the rate-dependent phenomena of high flux operation of gated multistep avalanche chamber has been reported in my previous paper. The calculation result reported is in accord with experiments. This mechanism may be generalized to explain the formation of self-quenching streamer (SQS).Here we propose another mechanism which is the generalization of the previous one.

A mechanism for explaining the rate-dependent phenomena of high flux operation of gated multistep avalanche chamber has been reported in my previous paper. The calculation result reported is in accord with experiments. This mechanism may be generalized to explain the formation of self-quenching streamer (sqs).Here we propose another mechanism which is the generalization of the previous one.

关键词： gated explain chamber quenching generalization simplified anode accord determ dense

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先进的超声手动扫描成象检测技术

无损检测 1997年第6期19卷 151-153,158页

作者：刘松平陈积懋郭恩明北京航空工艺研究所复合材料ndt中心北京100024

较详细地介绍了超声手动扫描成象检测技术,包括CCD视频图象定位技术、缺陷识别、典型的应用及主要技术性能.

关键词：手动扫描超声成象无损检测缺陷识别

Evaluation of defects in aluminum piston castings by using ultrasonics and computer tomography

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China Foundry 2012年第3期9卷 275-278页

作者： In-Sung Cho Jeong-Ho Hwang Jin-Seok Yang Seung-Mok Yoo Chae-Ho Lim Korea institute of Industrial Technology

Pistons used in automobile engines are made of aluminum alloy; and endurance of high pressure and high temperature is required. Recently, high strength pistons are needed to cope with the increase of pressure and temperature in the engine cylinder. A high strength piston is possible when the piston casting has little or no casting defects, such as micro-pores and cracks. Generally the defects can be evaluated by non-destructive testing (ndt), and the most efficient ways for evaluation are using ultrasonics and computer tomography. In the present study, two ndt methods were compared and evaluated to investigate the defects in the aluminum piston castings. Artificial defects were machined by using very small drill bits with diameters 1, 0.5, 0.3, 0.2 and 0.1 mm. The defects were investigated by using an ultrasonic tester and a computer tomography system. Defects smaller than 0.3 mm may not be found by using the ultrasonic test, but the defects may be found by using the computer tomography system. The investigation conditions for detecting small defects and the scanning time for in-line defect analysis are discussed in the present study.

关键词： piston ultrasonic test computer tomography aluminum defect

NUMERICAL SIMULATION OF ULTRASONIC NONDESTRUCTIVE TESTING FOR WELDS

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Acta Metallurgica Sinica(English Letters) 2004年第1期17卷 38-42页

作者： H.D.Chen Y.W.Wang J.Xue Welding Research institute Xi'an Jiaotong University Xi'an 710049 ChinaWelding Research Institute Xi'an Jiaotong University Xi'an 710049 ChinaWelding Research Institute Xi'an Jiaotong University Xi'an 710049 China

A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (ndt). In this paper, one goal of the simulation is to compute ultrasonic field radiated by arbitrary transducers into pieces under examination. The other simulates a testing experiment. The simulation approach is based on the model for the computation of the ultrasonic field in isotropic media radiated from actual ndt transducers. After the field is known, remaining to be modeled is the interaction between this field and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchhoff’s diffraction approximations theory applied to elastodynamics. We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous. The simulating results demonstrate that the model in ultrasonic ndt of welds is practical in further research and useful in optimizing testi

关键词： ultrasonic testing modeling welds numerical simulation

Effect of Thermal Treatment on CFRP Parts Before and After Adhesive Bonding

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 256-263页

作者： Pawe H Malinowski Mirosaw Sawczak Tomasz Wandowski Wiesaw M Ostachowicz institute of Fluid Flow Machinery Polish Academy of Sciences

Numerous non-destructive techniques are being investigated for assuring quality of the adhesive *** research presented here is focused on non-destructive assessment of carbon fibre reinforced polymer(CFRP)*** surface condition directly influences the performance of adhesive *** structural joints should ensure safe usage of a ***,some modifications of the surface may lead to weak bond that cannot carry the desired *** is why there is a search for methods of surface assessment before ***,reliable techniques are required to allow to verify the integrity of the adhesive bond after manufacturing or bonded *** focus on the laser induced fluorescence(LIF)method for assessing the surface *** LIF is a noncontact measurement *** the context of adhesive bond assessment the electromechanical impedance(EMI)method is *** EMI uses surface bonded piezoelectric sensors for excitation and *** investigated samples were made of CFRP *** samples were treated at elevated *** influence of the thermal treatment was studied using *** thermal treatment at 220℃could be clearly distinguishedrom the rest of the considered *** thermally treated plates were bonded to untreated plate and then they were measured with the EMI method to study the influence of the treatment on the adhesive *** changes of EMI spectra were significant for the treatment at 280 ℃ and for some thermally treated samples that were later contaminated with de-icing fluid.

关键词： adhesive joints carbon fibre reinforced polymer (FRP) composite laminates composite materials andrepairs composites electromechanical impedance non-destructive testing (ndt)

Full Wavefield Analysis for Damage Assessment in Composite Materials

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第2期35卷 264-274页

作者： Tomasz Wandowski Pawel Malinowski Wieslaw Ostachowicz institute of Fluid Flow Machinery Polish Academy of Sciences

In this paper damage assessment based on guided elastic wave propagation phenomenon is *** waves are generated by piezoelectric transducer and registered by scanning laser doppler vibrometer(SLDV).Signal processing is based on the analysis of full wavefield measurements gathered from dense mesh of measurement points spanned over area of investigated *** wavefield measurement approach allows creation of animations presenting the guided wave propagation in the *** such approach is suitable for analysis of interaction of guided waves with discontinuities located in *** the research attention is paid especially on analysis of phenomenon of S0/A0′guided wave mode conversion due to interaction with investigated discontinuities-teflon inserts and impact *** presented work is related to glass fibre reinforced polymer(GFRP)*** the research,auxiliary non-destructive testing(ndt)method is also *** aim of this method is to indicate the depth of discontinuity,and to prove that delamination was created in the case of impact *** method is based on terahertz spectroscopy(THz)where the analysis of propagation of electromagnetic waves in the terahertz band is *** spectroscopy method can be utilized for damage assessment in the dielectric materials like GFRP.

关键词： damage assessment guided wave propagation (GW) mode conversion terahertz spectroscopy(THz)

Constant Speed Control for Complex Cross-section Welding Using Robot Based on Angle Self-Test

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Chinese Journal of Mechanical Engineering 2014年第2期27卷 260-268页

作者： XUE Long ZOU Yong HUANG Jiqiang HUANG Junfen TAO Xinghua HU Yanfeng Opto-Mechatronic Equipment Technology Beijing Area Major Laboratory Beijing Institute of Petrochemical Technology School of Automation Science and Electrical Engineering Beihang University SINOPEC Research institute of Petroleum Engineering

Expandable profile liner（EPL） is a promising new oil well casing cementing technique, and welding is a major EPLs connection technology. Connection of EPL is still in the stage of manual welding so far, automatic welding technology is a hotspot of EPL which is one of the key technologies to be solved. A robot for automatic welding of＂8＂ type EPL is studied. Four quadrants of mathematical equations of the 8-shaped cross-section track of EPL, consisting of multiple arcs, are established. Mechanism program for complex cross-section welding of EPL based on angle detection is proposed according to characteristics of small size, small valleys, and large forming errors, etc. A welding velocity vector control model is established by linkage control of a welding vehicle, a small driven actuator, and a height tracking mechanism. A constant speed control model based on an angle and symmetrical analysis model of rectangular coordinate system for EPL is built. Constraint conditions of constant speed control between each section are analyzed with 4 sections in first quadrant as an example, and cooperation work mechanism of the welding vehicle and the small tracking actuator is established based on pressure detection. The constant speed control model using angle self-test can be used to avoid the need for a precise mathematical model for tracking control and to adapt manufacture and installation deviation of EPL workpiece. The model is able to solve constant speed and trajectory tracking problems of EPL cross-section welding. EPL seams welded by the studied robot are good in appearance, and non-destructive testing（ndt） shows the seams are good in quality with no welding defects. Bulge tests show that the maximum pressure of welded EPL is 35 MPa, which can fulfill expansion performance requirements.

关键词： expandable profile liner welding robot minitype driven actuator velocity vector model