Advanced Materials Research Vols. 201-203

Abstract: 0MnVTiNb, 12Cr1MoV, 20Cr2Ni4, 35CrMo, 40Cr, 42CrMo, 60Si2CrV and T8 steels and Fe-1.2C alloy were used to study the morphology and formation mechanism of martensite by metallographic microscope, QUANTA-400 environmental scanning electron microscope and JEM-2100 transmission electron microscope after they were austenized at different temperature and then quenched respectively. The results show that the martensite of low-carbon steel is lath martensite, the martensite of high-carbon steel is plate martensite, and the martensite of medium-carbon steel is the integrated microstructure of lath martensite and plate martensite. With the increase of carbon content, the morphology of martensite in steel evolves from lath shape to plate shape, the distribution of martensite slices changes from in parallel to with crossing angle, and the substructure evolves from high density dislocations and stacking faults to twin crystals. The martensite in steel can nucleate in the austenite crystal grain interior as well as along the austenite crystal grain boundary. It is proposed that the volumetric strain energy in martensite transformation is the essential reason of the different morphologies of martensite.

Abstract: This paper is concerned with the problem of automatic inspection of hot-rolled plate surface using machine vision. An automated visual inspection (AVI) system has been developed to take images of external hot-rolled plate surfaces and the detailed characteristics of the sensor system which include the illumination and digital camera are described. An intelligent surface defect detection paradigm based on morphology is proposed to detect structural defects on plate surfaces. The proposed method has been implemented and tested on a number of hot-rolled plate surfaces. The results suggest that the method can provide an accurate identification to the defects and can be developed into a commercial visual inspection system.

Abstract: Magnetic flux leakage (MFL) is a non-destructive testing method used to inspect ferrous materials. However, apparatus parameters could affect the MFL inspection tool’s ability to characterize anomalies. In this paper, MFL signals obtained during the inspection of pipes have been simulated using three-dimensional finite element analysis and the effects of magnet assembly on MFL signals are investigated. According to numerical simulations, an increase in the leakage flux amplitude is observed with an increase in the permanent magnet size and the inflexion point may indicate the presence of magnetizing pipe wall to near saturation. It clearly illustrates degradation in the MFL with increasing backing iron length. The relationship between MFL apparatus parameters and MFL signals could be utilized in the MFL technique to characterize the defect.

Abstract: Aiming to the problem that is very difficult to establish the mechanism model of quality for the process of tobacco leaves redrying, this paper proposes a quality prediction model based on principal component analysis (PCA) and improved back propagation (BP)neural network for tobacco leaves redrying process. Firstly, 12 input variables are confirmed by analyzing the factors on quality of tobacco leaves redrying process. Second, the methods of PCA is used to eliminate the correlation of original input layer data, in which 12 input variables are transformed into 6 uncorrelated indicators. Then, the quality prediction model based on improved BP neural network is established. Finally, a simulation experiment is conducted and the average prediction error is as low as 1.03%, the absolute error for forecasting is fluctuated in the range of 0.16% - 2.49%. The result indicates that the model is simpler and has higher stability for prediction, which can completely meet the actual requirements of the tobacco leaves redrying process.

Abstract: In aluminium smelters, the operational staffs constantly face decision making situations for operation and process control and these decisions can have significant impact on the process. The smelting process involves highly complex mechanisms and has rich information but low observability. In this environment, without support tools, systematic information management, or robust control models, decision making is challenging. This paper discusses different types of decision making processes and demonstrates that naturalistic decision making models (Recognition-Primed Decision Making, ie RPD) are more suitable to describe the situations in smelters. A model which combines an advanced control model, a system and human interactive approach and the thinking process in RPD is proposed to improve the quality of decisions for the operational staffs in smelters, hence the efficiency and productivity of the process.

Abstract: The improved GPS (Geometrical Product Specification) system uses uncertainty as an economic tool to enable optimum allocation of resource amongst specification, manufacturing and verification. For a given GPS standard-chain, the key question is to calculate the compliance uncertainty. The determination of compliance uncertainty is a complex question because specification uncertainty and measurement uncertainty arise from many causes and propagate through the GPS standard-chain. A calculation method for compliance uncertainty of GPS standard-chain is proposed in this article. According to ISO 17450–2, a GPS process should be either in default state or special state. The biggest difference between the two states is that whether the specification operator is accordant with the verification operator. Aiming at the two states, the flow for the computation of compliance uncertainty is given respectively, and a case study is applied in default state. Results show it enables to generate compliance uncertainty on the verification of a GPS standard-chain, which makes the acceptance or refusal of GPS characteristic can be conducted in a quantitative way, so the veracity of verification could be improved.

Abstract: Traditionally, independent dam or tidal fences in the sea should be built before the tidal energy electric power generating. In the near future, more and more cross sea bridges will be constructed between the mainland and the islands in the east of China, or between the islands. If the tidal fences are designed to be installed on these bridges, much investment will be saved than constructing tidal fences independently. But it will increase the loads of the bridges. Considering the bridges with or without tidal fences installed, three types of cross sea bridge models are built numerically. The stresses and deformations of the bridge structures are calculated. And the effects of the fences on the bridge structure are evaluated. The results may be useful for the designing of cross sea bridges and power generating device of tidal energy.

Abstract: This research presents a design of a thermal deformation errors compensation system for CNC machine tools which can compensate thermal deformation of Z-axis during the working time. The thermal deformation errors compensation system includes three instruments: displacement tester, temperature tester and thermal errors compensator. Displacement and temperature testers have been designed in the early researches, and the thermal errors compensator is designed in this research. The compensation process includes two parts, modeling part and compensation part. Modeling part focuses on making a model of thermal deformation, and compensation part focuses on using the model to compensate the thermal deformation of Z-axis during the working time.

Abstract: Natural ventilation of residential buildings not only affects the comfort of people` s outdoor areas, but also has an influence on the pressure distribution in front of or behind a single building. Based on the natural climatic conditions in Hefei, the most common three arrangements are referred in this paper, and their ventilation will be simulated and analyzed by the computer. The advantages and disadvantages of different arrangements will also be compared.

Abstract: Silicone rubber mold is one of soft mold processes for rapid tooling. Based on a master pattern, it can be used for casting the materials of wax, plastic, and low-melting metals directly during a short developing time, very suitable for sample fabrications. This paper conducts vacuum casting experiments by Taguchi’s method to derive the optimal parameter selections on ABS plastic vacuum casting using a silicone rubber mold. The factor that affects pouring characteristics maximally is the mold vacuuming time.