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Interval Optimization Method for Structural Dimensional Parameters and Dimensional Tolerance of Mechanical Parts

A technology of mechanical parts and structural dimensions, applied in the field of mechanical structure optimization design, can solve problems that affect the performance of structural design optimization targets or change constraints, structural dimension parameters and dimensional tolerances cannot be optimized simultaneously

Active Publication Date: 2020-10-20
NANJING UNIV OF SCI & TECH
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Problems solved by technology

[0006] In order to solve the problem that structural size parameters and dimensional tolerances cannot be optimized simultaneously, and the error of key structural dimensional parameters will affect the optimization target performance of structural design or the feasibility of changing constraints, the present invention provides a method of structural dimensional parameters and dimensional tolerances of mechanical parts The interval optimization method discretizes the interval of the key structural size parameters into discrete random variables to obtain the target performance interval distribution, and uses the processing accuracy as the evaluation index to construct the average tolerance grade coefficient evaluation function, and establishes the interval distribution of the target performance and the constraint condition interval distribution. Simultaneously optimize the nominal size and dimensional tolerance of key structural dimensional parameters with the uncertainty optimization model of machining accuracy

Method used

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  • Interval Optimization Method for Structural Dimensional Parameters and Dimensional Tolerance of Mechanical Parts
  • Interval Optimization Method for Structural Dimensional Parameters and Dimensional Tolerance of Mechanical Parts
  • Interval Optimization Method for Structural Dimensional Parameters and Dimensional Tolerance of Mechanical Parts

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Embodiment 1

[0082] Consider the following deterministic optimization problem with two design parameters:

[0083]

[0084] According to formula (5), n is set to 10, and the obtained m-dimensional possibility matrix 10×10 for:

[0085]

[0086] According to formula (13), the above optimization problem is transformed into:

[0087]

[0088] The optimal design parameters in the above formula are

[0089] Transform it into an unconstrained optimization problem using formula (16), combining figure 2 , using NSGA-Ⅱ genetic algorithm programming calculation, the population size is 100, iteration 400 generations, the crossover probability of arithmetic crossover is 0.8, and the mutation probability of Gaussian mutation is 0.1.

[0090] combine image 3 , Figure 4 It is known that there are many obvious jumps before the iteration 220 of the genetic algorithm, indicating that a better individual has been found. After 220 generations, the target performa...

Embodiment 2

[0096] Aiming at the problem of the large radial size and insufficient compact structure of the retreating machine of a large-caliber artillery, this paper adopts the above optimization model to obtain its parameter error scheme. The main structural parameters of the brake are the working length L of the brake and the working area of ​​the piston A 0 , The inner diameter of the withdrawal cylinder D T , Outer diameter of brake rod d T , Diameter of the inner cavity of the brake rod d 1 , control ring diameter d p , Outer diameter of the withdrawal cylinder D 1 , where other parameters depend on the inner diameter of the brake cylinder D T and the outer diameter of the brake rod d T get, select D T and d T is the key design parameter [x 1 , x 2 ]=[D T , d T ]; the objective function is to minimize the absolute value of the difference between the working area of ​​the piston obtained by considering the actual structure and the working area of ​​the pis...

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Abstract

The invention discloses mechanical component structural dimension parameters and an interval optimization method for dimensional tolerance thereof. The method comprises following steps: determining mechanical component structural dimension parameters requiring interval optimization design; assuming that the structural dimension parameters obey normal distribution, discretizing the structural dimensional parameters and functions thereof and establishing an interval likelihood model based on discretization; describing the structural dimension parameter interval with interval midpoints and interval radius and establishing the average tolerance grade coefficient; establishing interval optimization model of structural dimension parameters and dimensional tolerance of mechanical components; converting to non-restraint optimization problem with the penalty function method; using the multi-target genetic algorithm for solutions. According to the invention, optimization can be simultaneously carried out to obtain the nominal dimension and the dimension tolerance, and optimization can be carried out to obtain solutions with the better target performance, meanwhile, the average tolerance grade coefficient has obvious engineering significance.

Description

technical field [0001] The invention relates to the field of mechanical structure optimization design, in particular to an interval optimization method for structural dimension parameters and dimension tolerances of mechanical parts based on discretized interval possibility and machining accuracy. Background technique [0002] Traditional mechanical design problems are generally based on determined parameters and optimization models, and are solved with the help of classic deterministic optimization problems, but in actual engineering problems, structural dimensions, material properties, loads, boundary conditions, component parameters, measurement Errors or uncertainties such as deviations must exist, and these errors or uncertainties will affect the optimization target performance of the design or the feasibility of changing constraints. The present invention starts from the uncertainty of the structural size to optimize the design of the mechanical structure. [0003] The...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F30/17G06F30/27G06F111/04
CPCG06F30/17G06F30/20G06F2111/04
Inventor 李荣杨国来葛建立孙全兆刘宁李志旭
Owner NANJING UNIV OF SCI & TECH
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