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Feature extraction of wood-hole defects using wavelet-based ultrasonic testing 被引量:7
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作者 Huiming Yang Lei Yu 《Journal of Forestry Research》 SCIE CAS CSCD 2017年第2期395-402,共8页
The primary bottleneck to extracting wood defects during ultrasonic testing is the accuracy of identifying the wood defects. The wavelet energy moment was used to extract defect features of artificial wood holes drill... The primary bottleneck to extracting wood defects during ultrasonic testing is the accuracy of identifying the wood defects. The wavelet energy moment was used to extract defect features of artificial wood holes drilled into 120 elm samples that differed in the number of holes to verify the validity of the method. Wavelet energy moment can reflect the distribution of energy along the time axis and the amount of energy in each frequency band,which can effectively extract the energy distribution characteristics of signals in each frequency band; therefore,wavelet energy moment can replace the wavelet frequency band energy and constitute wood defect feature vectors. A principal component analysis was used to normalize and reduce the dimension of the feature vectors. A total of 16 principal component features were then obtained, which can effectively extract the defect features of the different number of holes in the elm samples. 展开更多
关键词 wavelet defects ultrasonic extracting replace validity identifying verify processed bottleneck
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Design Process Optimization Based on Design Process Gene Mapping
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作者 LI Bo TONG Shu-rong 《International Journal of Plant Engineering and Management》 2011年第3期178-185,共8页
The idea of genetic engineering is introduced into the area of product design to improve the design efficiency. A method towards design process optimization based on the design process gene is proposed through analyzi... The idea of genetic engineering is introduced into the area of product design to improve the design efficiency. A method towards design process optimization based on the design process gene is proposed through analyzing the correlation between the design process gene and characteristics of the design process. The concept of the design process gene is analyzed and categorized into five categories that are the task specification gene, the concept design gene, the overall design gene, the detailed design gene and the processing design gene in the light of five design phases. The elements and their interactions involved in each kind of design process gene signprocess gene mapping is drawn with its structure disclosed based on its function that process gene. 展开更多
关键词 design process optimization design process gene design process gene characteristic are identified and the delocates the defective design mapping design process
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Influence of Process Parameters and Sr Addition on the Microstructure and Casting Defects of LPDC A356 Alloy for Engine Blocks 被引量:10
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作者 Giulio Timelli Daniele Caliari Jovid Rakhmonov 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2016年第6期515-523,共9页
The effects of Sr addition and pressure increase on the microstructure and casting defects of a low-pressure die cast (LPDC) AISi7Mg0.3 alloy have been studied. Metallographic and image analysis techniques have been... The effects of Sr addition and pressure increase on the microstructure and casting defects of a low-pressure die cast (LPDC) AISi7Mg0.3 alloy have been studied. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes and the amount of porosity occurring at different Sr levels and pressure parameters. The results indicate that an increase in the filling pressure induces lower heat dissipation of the liquid close to the die/core surfaces, with the formation of slightly greater dendrite arms and coarser eutectic Si particles. On the other hand, the increase in the Sr level leads to finer microstructural scale and eutectic Si. The analysed variables, within the experimental conditions, do not affect the morphology of eutectic Si particles. Higher applied pressure and Sr content generate castings with lower amount of porosiW. However, as the filling pressure increases the flow of metal inside the die cavity is more turbulent, leading to the formation of oxide films and cold shots. In the analysed range of experimental conditions, the design of experiment methodology and the analysis of variance have been used to develop statistical models that accurately predict the average size of secondary dendrite arm spacing and the amount of porosity in the low-pressure die cast AISiTMg0.3 alloy. 展开更多
关键词 Aluminium alloys Engine block Microstructure Casting defects Sr addition Process parameters
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Improving the process forming limit considering forming defects in the transitional region in local loading forming of Ti-alloy rib-web components 被引量:2
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作者 Pengfei GAO Xiaodi LI +2 位作者 He YANG Xiaoguang FAN Zhenni LEI 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2017年第3期1270-1280,共11页
The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by... The isothermal local loading forming technology provides a feasible way to form Ti-alloy large-scale rib-web components in aerospace and aviation fields.However,the local loading process forming limit is restricted by forming defects in the transitional region.In this work,the feasibility of controlling forming defects and improving the process forming limit by adjusting die parameters is explored through finite element(FE) simulation.It is found that the common cavum and folding defects in the transitional region are significantly influenced by the fillet radii of left rib and middle rib,respectively.The cavum and folding defects can be effectively controlled by increasing the fillet radii of left rib and middle rib,respectively.The process forming limits considering forming defects in the transitional region are determined by the stepwise searching method under various die parameters.Moreover,the relationship between the process forming limit and die parameters is developed through the response surface methodology(RSM).The developed RSM models suggest that increasing the fillet radii of left and middle ribs is effective to improve the process forming limit during local loading forming of rib-web components.The results will provide technical basis for the design of die parameters and the reduction amount,which is of great importance to control forming defects and improve the process forming limit in local loading forming of Ti-alloy large-scale rib-web components. 展开更多
关键词 defect Large-scale rib-web component Local loading forming Process forming limit Transitional region
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Crack analysis in Ti-6Al-4V alloy produced by selective laser melting 被引量:2
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作者 Hui-Yan Zhang Yan-Hui Liu +3 位作者 Zhi-Wei Li An-Hui Xiong Ke Li Jia-Yun Fu 《Tungsten》 2021年第3期361-367,共7页
Quality and property control have become one of the critical problems for the metallic parts produced by selective laser melting.In this paper,the crack spontaneously formed in the Ti-6 Al-4 V alloy by selecting laser... Quality and property control have become one of the critical problems for the metallic parts produced by selective laser melting.In this paper,the crack spontaneously formed in the Ti-6 Al-4 V alloy by selecting laser melting is investigated.The crack is C-shape without branching in macro view.In micro view,the crack originates from and propagates toward the selective laser melting(SLM)processing defects.The crack surface topography shows that the crack is typical dimple cleavage.A few heads of martensiticα’laths appear at the bottom of the dimple.And the secondary crack nucleates and grows up near by the martensiticα’laths.A lot of spatters and cavities formed at the top surface of the SLM body and the residual stress accumulated in the SLM body is up to 640 MPa,which confirms that the SLM processing defects and the residual stress induced the origination and propagation of the crack.The research results indicate that preventing spatter and controlling residual stress are important to SLM processing. 展开更多
关键词 Selecting laser melting TI-6AL-4V CRACK processing defect Residual stress
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