Zhi He

3D-FE simulation of inhomogeneous stress and strain distributions in cold profiled ring rolling process under different hardening coefficients

Cold profiled ring rolling is an advanced continuous local metal forming technology widely used for manufacturing various seamless complex-section rings. Investigating the stress and strain distributions (SSD) is very significant for rapidly predicting the defects and improving the quality of deformed rings. The non-uniform SSD in T-shaped cold ring rolling with different hardening exponents are investigated based on 3D-FE simulation. The results show: 1 despite the difference in hardening exponent, the compressive effect of stress is larger near the outer-surface and decreases toward the core; it increases from the core to contact inner-surface but decreases from the core to the non-contact inner surface 2 the deformation around the groove fillet is larger and more non-uniform 3 the surface layer of the filling part near the fillet deforms a little smaller but still non-uniformly, the tensile principal stress components increases and the hydrostatic stress is positive, resulting in poor plasticity.

Research on the effects of geometric parameters of ring blank on cold profiled ring rolling process

Cold profiled ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometric parameters of ring blank and rolls, forming process parameters, material properties, friction, etc. Among these factors, the geometric parameters of ring blank play significant roles because they directly affect the dimensional accuracy and internal quality of deformed ring. In this paper, through numerical simulation for typical cold profiled ring rolling process (cold T-shaped ring rolling) based on dynamic elastic-plastic 3D-FEM under ABAQUS/explicit environment, the effects of three geometric parameters of ring blank (average radius, radial thickness and axial width) on filling behaviour, diameter expansion and forming quality around the groove entrance have been investigated. It can be found that, These achievements provide an important basis for design and optimisation of ring blank dimensions in cold profiled ring rolling process.

Effects of speed parameters on cold rolling process of double groove ball-section ring

Abstract Double groove ball-section ring is an important part of complex profiled-section rings and has been widely used in energy industries, and cold double groove ball-section ring rolling is a new plastic forming technology that can directly fracture seamless double groove ball-section rings with high-precision and high-performance. Because the speed parameters (including the rotational speed of driving roll and the feed rate of mandrel) affect the feed amount per revolution and play important roles in the stability of cold double groove ball-section ring rolling process and the quality of deformed double groove ball-section ring production, the effects of speed parameters on the variation of ring configuration and the variation of strain in cold double groove ball-section ring rolling process are investigated. The obtained results provide valuable guidelines for the selection of speed parameters in the practical cold double groove ball-section ring rolling process.

Multi–response optimisation design of parameters for cold ring rolling process using fuzzy–grey method

Cold ring rolling (CRR) is a complex metal forming process with continuous and local three–dimension metal flow under coupled effects with multi–factors, which includes geometry sizes of rolls and ring blank, material properties, speed parameters, friction conditions, etc. In this paper, a multi–response optimisation design for the forming parameters of opened–pass plain CRR process is proposed to obtain the desired quality and precision of the deformed ring. Sixteen virtual orthogonal experimental arrays with five control factors (the radii RD and the rotational speed nD of the driving roll, the radii RM and the feed rate vM of the mandrel, and the friction coefficient µ) are designed based on Taguchi methodology, and four responses (the average spread AS, the fishtail coefficient FC, the equivalent plastic strain distribution SDP and the maximum rolling force MaxRF) are measured according to three–dimension finite element numerical simulation. Moreover, a novel fuzzy–grey optimisation design method, which can effectively deal with the uncertain nature of the measured data and observably reduce the analysis cost by parallel computing, is proposed by integrating grey relational analysis with fuzzy relational analysis. The investigation clearly shows that the proposed method can serve as a valuable guideline to optimise the forming parameters of the CRR process.

Research on Intelligent Fault Diagnosis Method Based on Rough Set Theory and Fuzzy Petri Nets

Rough sets theory (RST) and Fuzzy Petri nets (FPN) have been widely used in fault diagnosis. However, RST has the weakness of over-rigidity decision, and FPN has the dimensional disaster problem. In order to solve these shortcomings, according to complementary strategy, a new fault diagnosis method based on integration of RST and FPN was presented. Firstly, RST was applied to remove redundant fault features and simply fault information, so that the minimal diagnostic rules can be obtained and the fault was roughly diagnosed. Secondly, the optimal FPN structure was built and the fault diagnosis was finally realized through matrix operation of FPN. Finally, a diesel engine fault diagnosis example was analyzed, and the results show that the proposed method not only holds the ability of RST for analyzing and reducing data, but also has the advantage of FPN for parallel reasoning, so it has strong engineering practicability and validity.

Research on Fault Recognition for Centrifugal Compressor Using Entropy Weight-Based Gray Relational Analysis

A new fault recognition method for centrifugal compressor was proposed by using entropy weight-based gray relational analysis (EW-GRA). Firstly, the weight values of all fault features were calculated objectively by the entropy method to avoid the influence of subjective factors. Secondly, an improved local gray relational coefficient (LGRC) formula with weight measures was designed to reflect the contributions of different fault features. Thirdly, according to the relationship between similarity degree and Euclidean distance, the local gray relational distances (LGRD), the global gray relational distances (GGRD) and the global gray relational grades (GGRG) were calculated, and consequently, the fault recognition result was obtained by using the max membership degree principle. Finally, the engineering practicability and validity of the EW-GRA method was demonstrated by a centrifugal compressor fault diagnosis example, and the results show that the EW-GRA method is more effective and accurate than the traditional gray relational analysis (T-GRA) method and the weighted gray relational analysis (W-GRA) method.

Research on Intelligent Fault Diagnosis Method for ESP Protector Based on Fuzzy Petri Nets

The protector is a key part of electric submersible pump (ESP), seals the motor and prevents the water entering into it. In order to solve the problem of complexity and uncertainty of fault propagation and analysis in protector, a new method for ESP protector fault diagnosis based on Fuzzy Petri nets (FPN) is proposed. Firstly, according to expert experiences and maintain rules, the FPN structure which has 28 places and 11 transitions is built to describe the protector fault propagation relations. Secondly, the five matrixes representing the FPN structure are obtained, and a rapid fault inference algorithm is designed via matrix operations. Finally, two fault diagnosis cases are analyzed, and the results show that the proposed method is valid and has strong engineering practicality.

Research on Fault Recognition for Centrifugal Compressor Based on Fuzzy Gray Relational Grade

In practical centrifugal compressor fault diagnosis, it is very difficult to improve the fault recognition rate, especially when the sample sizes are small. To solve this problem, a new fault recognition method based on fuzzy gray relational grade was proposed. Firstly, according to fuzzy set theory, the fuzzy relation coefficient (FRC), fuzzy relation degree (FRD) and fuzzy relative weights (FRW) of all fault features were calculated. Secondly, the gray system theory was used to obtain the gray relational coefficients (GRC). Thirdly, by combining FRW and GRC, two fuzzy gray relation grades (FGRG) were presented, which is the Hamming distance-based fuzzy gray relation grade (HD-FGRG) and the Euclidean distance-based fuzzy gray relation grade (ED-FGRG), respectively. Finally, the fault recognition results were obtained by using the max membership degree principle. The centrifugal compressor fault diagnosis results show that the ED-FGRG method is more effective and accurate than traditional gray relational analysis (T-GRA) method, the weighted gray relational analysis (W-GRA) method, and the entropy weight-based gray relational analysis (EW-GRA) method and the HD-FGRG method.

Research on Fault Diagnosis for Centrifugal Compressor Using Entropy-Based Fuzzy Gray Relational Analysis

. A novel fault diagnosis method for centrifugal compressor was proposed by using entropy- based fuzzy gray relational analysis (EF-GRA). Firstly, the minimize entropy principle (MEP) was used to subdivide all real-valued fault features and construct membership functions of fuzzy variables. Secondly, based on the gray theory, the fuzzy-gray relational coefficients (F-GRC) were calculated and the weighted fuzzy-gray relation degrees (WF-GRD) were obtained, so that the diagnostic result can be determined. Finally, a centrifugal compressor fault dataset was used to illustrate the proposed method, and the results show that it has strong engineering practicability and validity.

Calculating the Phase Equilibria of Al Rich Al-Cu-Mg Alloys

This paper investigates a new method, the Levenberg-Marquardt method, to calculate the phase equilibria of the Al-Cu-Mg ternary alloys. The Levenberg-Marquardt method is the best algorithm to obtain the least-square solution of non-linear equations. Its application to ternary Al-Cu-Mg system is executed in detail in this paper. The calculated phase equilibria agrees well with the experimental results. Furthermore, the Levenberg-Marquardt method is not sensitive to the initial values.