The bolted-flange connection is one of the most popular detachable mechanical joints in mechanical flange connection. It is well known that bolted-flange joints need to be tightened to meet the assembly performance in...
The bolted-flange connection is one of the most popular detachable mechanical joints in mechanical flange connection. It is well known that bolted-flange joints need to be tightened to meet the assembly performance in practical engineering applications. However, the dispersion of the pre-tightening force caused by the elastic interaction between the bolts has a serious impact on the sealing and safety of the product, and therefore the optimization of bolt preload has always been a hot spot in the assembly research field. Combining mathematical theory and experimental data, this paper proposes an optimization model for uniformly distributed preload based on the Markov theory. The torque method was utilized to fasten the bolt-flange joint. The bolt pre-tightening force in the final state was collected and used as sample data. A state transition model was constructed to determine the state transition matrix. Ultimately, an iterative model of the preload was deduced, and the rationality of the model was verified through experimentation. The proposed optimization method of bolt preload can be applied to determine the initial preload of each bolt. This method improves the assembly efficiency and accuracy, which provides a theoretical approach to effectively guide the tightening work of bolted-flange connections.
The reliability allocation method of machinetools has the feature of high complexity and uncertainty. To reduce the fuzziness in the process of reliability allocation, this paper proposes a novel reliability allocati...
The reliability allocation method of machinetools has the feature of high complexity and uncertainty. To reduce the fuzziness in the process of reliability allocation, this paper proposes a novel reliability allocation method of CNC machinetools based on Intuitionistic Trapezoidal Fuzzy Number and Grey Correlation. First, the subsystems of CNC machinetools are divided based on function, and the reliability of subsystems are also allocated. Then, expert decision matrixes are obtained based on intuitionistic trapezoidal fuzzy numbers. The result is obtained by the calculation of the grey relation degree between decision matrixes and ideal matrixes. Finally, an example is taken to verify the effectiveness of the proposed method. Compared to the traditional method, the proposed method can reduce the calculation and more convenient to use.
Bolted joints have a significant effect on the dynamical behaviour of assembled structures. Accurate contact stiffness model of bolted joint is crucial in predicting the dynamic performance of bolted structures. In th...
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Long forging production cycle and low equipment utilization are the important problems currently facing domestic die forging ring production lines. To solve this problem, a simulation optimization method for die forgi...
Long forging production cycle and low equipment utilization are the important problems currently facing domestic die forging ring production lines. To solve this problem, a simulation optimization method for die forging production line based on Flexsim was proposed. Firstly, the ECRS theory method was used to analyze the bottleneck process of the production line. Then, built a logistics simulation model of die forging production line based on Flexsim, The parallel and cycle processing steps was set reasonable parameters and simulated. Next, through logic analysis, methods such as adding processing equipment, improving equipment efficiency and balancing equipment handling tasks were used to optimize and improve the production line. Finally, compared and analyzed the original and optimized model. The simulation results show that the optimized production line equipment task allocation tends to be rationalized, the equipment utilization rate is increased by 4.34%, and the product cycle time is reduced by 27.65%, and optimized planning and design are achieved.
For the change of uncertainty caused by the influence of time on the bolt connection during use, this paper is based on a time-varying uncertainty design method for several parameters that change with time. The method...
For the change of uncertainty caused by the influence of time on the bolt connection during use, this paper is based on a time-varying uncertainty design method for several parameters that change with time. The method consists of stochastic differential equations. The bolt-on time-varying design combines mathematical models of the distribution parameters of multivariate random variables. The design method of bolting connection with uncertainties of various influencing factors with time is proposed, and the time-varying design of tightly connected bolts subjected to axial working load is taken as an example. The method considers the dynamic changes of the stress and the allowable stress of the bolted joint, so that the safety of the bolted product is more accurately evaluated for dynamic reliability. Through this method, combined with the set initial values of the parameters and the historical data obtained by the test, the reliability of a certain time can be calculated. The design of the example uses Matlab to simulate the data, and the reliability of the specified time is obtained, which is the test of the bolting result. And assessment provides an important reference.
Bolted joints have a significant effect on the dynamical behaviour of assembled structures. Accurate contact stiffness model of bolted joint is crucial in predicting the dynamic performance of bolted structures. In th...
Bolted joints have a significant effect on the dynamical behaviour of assembled structures. Accurate contact stiffness model of bolted joint is crucial in predicting the dynamic performance of bolted structures. In this research, a modified three-dimensional fractal model of normal contact stiffness is presented to more accurately predict the dynamic characteristic of a bolted assembly. In the present model, while the contact deformation exceed the critical value the elastic-plastic contact is used to take the place of Hertz elastic contact in the traditional M-B model, and revise the drawback that elastic-plastic contact occurs before elastic contact in existing elastic-plastic fractal models. As the increase of contact force, the plastic deformation of single asperity is considered again, which is omitted in the two type fractal models. An experimental set-up with two T-shaped specimen is designed conducted to verify the efficiency of the proposed model. Comparing with the ZX elastic-plastic fractal model, the present model can predict contact stiffness and dynamic performance more accurately, particularly, while for higher contact loads. The results show that the modified elastic-plastic fractal contact model can be used to more accurately predict the stiffness and dynamic characteristic of bolted structures in the machinetools.
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