A method for optimizing the design of a marine gearbox housing structure

Abstract

The present invention provides a method for optimizing the design of a marine gearbox housing structure, mainly for the existing marine gearbox housing design, which is still based on theoretical calculation, empirical analogy, model making, experimental comparison, and then improvement. This mode is putting the cart before the horse, time-consuming and labor-intensive, and requires a lot of cost to design a gearbox structure that meets the requirements, and the designed gearbox may not be the best. A method for optimizing the design of a marine gearbox housing structure based on the HyperWorks analysis platform is proposed. A variety of optimization methods are comprehensively utilized, with housing stiffness, natural frequency, bearing seat vibration, and engine foot vibration as optimization targets or constraints, and improvement measures are proposed for places with poor performance in the housing structure, such as excessive local stress, local deformation that may affect transmission accuracy, and parts with excessive vibration amplitude, and redundant design parts in the housing structure are improved, so that the housing can meet both the requirements of vibration reduction and noise reduction and the requirements of lightweight design.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical equipment, and in particular to a method for optimizing the design of a housing structure of a marine gearbox. Background Art

[0002] As the most commonly used mechanical transmission component, gearboxes have been widely used in the fields of automobiles, aviation, aerospace, and ships due to their advantages of high transmission efficiency, compact structure, and stable transmission ratio. Gearboxes are mainly composed of transmission gear pairs, bearings, and housings. Due to the manufacturing errors and installation errors of the gears themselves, the gears will vibrate and generate meshing noise when they are meshed. The gear shaft transmits the vibration to the housing through the bearing, causing the vibration of the entire gearbox. The vibration of the gearbox is one of the main sources of ship radiation noise and will directly affect the combat effectiveness of the ship. Therefore, for ship gearboxes, it is not only required to have high transmission power, small size, and light weight, but also to have low vibration and noise to improve the combat performance of the ship.

[0003] Among the various structures of the gearbox reducer, the housing is an important component. It is the base of the transmission parts and should have sufficient strength and rigidity. Some large ships are usually powered by multiple main engines of different forms, which requires the gearbox to have the ability to evenly distribute the main engine power to achieve the best utilization of the main engine. However, this type of gearbox usually has a complex structure. In actual transmission connections, the housing often distorts due to insufficient rigidity, thereby inducing abnormal vibration. In addition, insufficient rigidity during operation will also cause impact damage. In this regard, the traditional design method usually remains in the mode of theoretical calculation, empirical analogy, model making, experimental comparison, and then improvement. The above design method is upside down, time-consuming and labor-intensive, and it takes a lot of money to design a gearbox structure that meets the requirements, and the designed gearbox may not be the best.

[0004] To solve the above problems, the present invention proposes a method for optimizing the design of a marine gearbox housing structure based on the HyperWorks analysis platform. The method comprehensively utilizes a variety of optimization methods, takes housing stiffness, natural frequency, bearing seat vibration, and machine foot vibration as optimization targets or constraints, and proposes improvement measures for areas with poor performance in the housing structure, such as excessive local stress, local deformation that may affect transmission accuracy, and areas with excessive vibration amplitude, and improves redundant design areas in the housing structure, so that the housing can meet both the requirements of vibration reduction and noise reduction and the requirements of lightweight design. Summary of the invention

[0005] The object of the present invention is to provide a method for optimizing the design of a marine gearbox housing structure in view of the above-mentioned defects of the prior art.

[0006] The object of the present invention is achieved in that the steps are as follows:

[0007] Step 1: Design the box and build a 3D model of the box;

[0008] Step 2: Optimize the design of the box shape and determine the reinforcement position;

[0009] Step 3: Optimize the design of the box size and optimize the rib size to reduce the weight of the box.

[0010] The present invention also includes such structural features:

[0011] 1. The box shape optimization design includes the following steps:

[0012] (1) Box 3D model processing: Remove the reinforcement features in the preliminary design box 3D model to make it a large panel structure.

[0013] (2) Finite element modeling: Import the processed model into HyperMesh software, determine the optimization area, perform meshing, set material properties and unit types, and apply constraints and loads.

[0014] (3) Use the OptiStruct solver morphology optimization module to perform optimization calculations. Determine the design variables, input the rib height, rib angle, and rib height, set the response function to the strain energy of the optimization area, set the optimization goal to minimize the strain energy, and set the constraints to the natural frequency of the box, vibration acceleration, bearing seat deformation, and maximum box stress. Calculate the optimal reinforcement position, design the reinforcement at the optimal reinforcement position, perform finite element analysis, and adjust the reinforcement properties until the design indicators such as vibration meet the requirements.

[0015] (4) Use Hyperview software for post-processing and output of the optimized 3D model. Combined with process experience, secondary design is performed.

[0016] 2. The cabinet size optimization design includes the following steps:

[0017] (1) Perform finite element modeling on the optimized box. Import the reinforced model into HyperMesh software, determine the optimization area, perform meshing, set material properties and unit types, and apply constraints and loads.

[0018] (2) Use the OptiStruct solver size optimization module to perform optimization calculations. The goal of optimization is to minimize the box mass, with the box strain energy, maximum stress, and vibration acceleration at the box bearing seat and machine foot as constraints. The box structure size is used as the design variable for size optimization until the box mass is minimized and the relevant vibration indicators are met.

[0019] (3) Use Hyperview software to post-process and output the dimensionally optimized 3D model. Combine process experience to perform secondary design.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention mainly aims at the existing marine gearbox housing design, which is still in the mode of theoretical calculation, empirical analogy, model making, experimental comparison, and then improvement. This mode is putting the cart before the horse, time-consuming and labor-intensive, and requires a lot of cost to design a gearbox structure that meets the requirements, and the designed gearbox may not be the best. In this case, a marine gearbox housing structure optimization design method based on the HyperWorks analysis platform is proposed. The method comprehensively utilizes a variety of optimization methods, takes housing stiffness, natural frequency, bearing seat vibration, and machine foot vibration as optimization targets or constraints, and proposes improvement measures for places with poor performance in the housing structure, such as excessive local stress, local deformation that may affect transmission accuracy, and parts with excessive vibration amplitude, and improves the redundant design parts in the housing structure, so that the housing can meet both the vibration reduction and noise reduction requirements and the lightweight design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of a method for optimizing the structure of a marine gearbox housing of the present invention;

[0022] Figure 2 It is a flow chart of the box body shape optimization design method of the present invention;

[0023] Figure 3 It is a flow chart of the box size optimization design method of the present invention;

[0024] Figure 4 This is a finite element model diagram of a certain type of marine gearbox housing of the present invention;

[0025] Figure 5 This is the result of the optimization analysis of the housing shape of a certain type of marine gearbox of the present invention;

[0026] Figure 6 It is a three-dimensional model of a certain type of marine gearbox after optimization of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] A method for optimizing the structure of a marine gearbox housing according to the present invention is as follows: Figure 1 As shown, it mainly includes the following steps:

[0029] (1) Preliminary design of the box and 3D modeling. The preliminary design of the box mainly includes the design of the main structural parameters of the box, such as the thickness of the box wall, the thickness of the center panel, the thickness of the bottom plate, the thickness and length of the reinforcing ribs, the diameter of the bearing seat bolts, the diameter of the center panel bolts, and the diameter of the anchor bolts. These designs can be completed by referring to the relevant formulas in the mechanical design manual, and the 3D model of the box is established based on the preliminary calculation results.

[0030] (2) Based on step (1), the morphology of the box is optimized. The main purpose of the box morphology optimization is to use the finite element simulation method to change the mechanical properties of the structure by modifying the unit node position and the internal structure shape of the preliminarily designed box, and obtain the optimal reinforcement position of the box. Figure 2The specific implementation steps for morphology optimization are as follows. When performing morphology optimization, the rib features in the three-dimensional model of the box body in step (1) should first be removed to make it a large panel structure; secondly, finite element modeling should be performed, and the processed model should be imported into the HyperMesh software to determine the optimization area. Positions that are not suitable for reinforcement, such as the bearing seat and the support plate, are non-optimized areas. The geometry is cleaned up, the mesh is divided, the material properties and unit types are set, and the mesh is modeled. The morphology optimization model is established using Shell units, and the size of the mesh division and the definition of the material properties are the same as those of the solid unit model. Considering the actual installation of the marine gearbox, when applying constraints, the 6 degrees of freedom of each bolt hole on the bottom flange are fully constrained, the main node is grounded, and the stiffness and preload of the bolt are ignored. The RBE2 rigid unit is used to simulate the threaded connection and pin connection between the upper and lower boxes. RBE2 units are established at the threads and pin holes of the two boxes respectively. After connecting the slave nodes on the cylindrical surface of the hole with the master node at the center point of the hole, the master nodes of the two boxes are connected one by one. For the bearing load application, the RBE3 flexible unit is used for simulation. The main node of the RBE3 unit located at the center hole of each bearing seat is connected to the slave node located on the inner surface of each hole, and then the box load is evenly applied to the main node of the unit of each bearing seat. The load size is calculated by the input torque. This load application method can be achieved in HyperMesh by creating a corresponding functional curve and loading the radial force according to the corresponding functional relationship of the curve. The OptiStruct solver morphology optimization module is used again to optimize the established finite element model. The design variables of the morphology optimization are set as the area to be optimized, and the rib height, rib angle and width of the optimization area are input. The width is generally twice the minimum grid width, the rib angle is generally 60°~75°, and the rib height is 3 times the wall thickness. Set the response function as the strain energy of the optimization area. Set the optimization goal to minimize the strain energy, and the constraints are the natural frequency of the box, vibration acceleration, bearing seat deformation, and maximum stress of the box. The opticontrol panel is used to control the number of optimization iterations and convergence results and other parameters, and the recommended reinforcement position is calculated. According to the reinforcement position, the reinforcement design is performed. The finite element analysis of the gearbox housing after reinforcement is performed to evaluate whether the vibration and other indicators can meet the design goals. If they can, the optimization ends. If the design goals are not met, the rib properties of the optimization area are adjusted, and the optimization is continued until the goals are met. Finally, the Hyperview software is used for post-processing to view the results. The three-dimensional solid model that meets the design requirements is output to the three-dimensional solid modeling software, and a secondary design is performed according to the feasibility of the forming process. Note that it is not advisable to add reinforcement to the bearing seat, but the thickness of the bearing seat can be appropriately reduced and the thickness of the bottom flange can be increased to improve the stiffness of the housing and reduce vibration.

[0031] (3) After completing the preliminary design of step (1) and determining the reinforcement position according to the morphology optimization of the housing in step (2), the rib plate size is further optimized by changing the thickness, mass and other properties of the structural unit to reduce the weight of the gearbox. Figure 3 The specific implementation steps for the optimized design of the box size. The size optimization design steps are similar to the morphology optimization, except that the selected solution modules and design goals are different. First, the HyperMesh software is used to extract the mid-surface of the three-dimensional model after morphology optimization, divide the mesh, add constraints and loads, and complete the finite element modeling. Secondly, the OptiStruct solver size optimization module is used to minimize the box mass as the goal, and the box strain energy, maximum stress, and vibration acceleration at the box bearing seat and machine foot are used as constraints. The box structure size is used as the design variable to establish a size optimization model and perform size optimization calculations on the box, and optimize until the box mass is minimized and meets the relevant vibration indicators. Finally, the final design of the box is completed according to the results of the size optimization, and the optimized three-dimensional solid model is output to the three-dimensional solid modeling software. The secondary design is performed according to the feasibility of the forming process to complete the final structural design of the gearbox, and a box with high stiffness, low vibration, and light weight is obtained, thereby achieving lightweighting of the box.

[0032] An embodiment of the present invention is given in combination with specific parameters: a structural optimization design is performed on a certain marine box. After completing the preliminary design, the morphology optimization design begins. The three-dimensional solid unit model is simplified into a two-dimensional plate and shell unit model. The simplified shell unit model only retains the main topological structure of the box, and ignores some structural details, such as chamfers, fillets, small bosses, circular holes, etc. The bearing seats of the box are directly stressed parts, and the structure cannot be changed, so the non-optimized areas are located. In addition, since the mesh deformation between ribbed and unribbed is large after mesh deformation, in addition to the installation position and the position where ribs are not required, for some parts that are bent or the areas where the normal angles of the mesh nodes change greatly, in order to avoid the phenomenon that the mesh in this area is of poor quality due to automatic deformation and the calculation does not converge, these areas are also set as non-optimized design areas, and finally the optimized positions of this type of gearbox are determined to be the upper and lower box wall panels. The material used is set to be Q235 steel, and the load is calculated based on the actual ship working conditions. The finite element modeling is completed as follows: Figure 4 As shown. At the same time, the minimum width of the rib is determined to be 20mm, the rib angle is 70°, and according to the elongation characteristics of the box material, the rib height is taken as 3 times the wall thickness, and the rib height is determined to be 90mm. The optimization goal is to minimize the strain energy, and the weights of all working conditions are the same. The constraints are the natural frequency, vibration acceleration, and maximum stress under the rated working conditions. After determining the above conditions, the morphology optimization calculation of the box is performed. The optimization analysis results obtained after iterative calculation are shown as follows. Figure 5As shown. The dark area in the figure is the position where ribs are required. According to the analysis results, the arrangement plan of the reinforcing ribs can be obtained. At the same time, considering that the bearing seat is the direct force point, in order to ensure the strength and rigidity of the box, transverse ribs are arranged to connect the bearing seat and each connecting plate and the bottom flange. After the morphology optimization, the size of the box is optimized. The reasonable value range of each design variable in the size optimization is set. At the same time, considering the numerical simulation results of the morphology optimization, the various structural dimensions of the box have a great influence on the characteristics of the box. The natural frequency, vibration acceleration and maximum stress of the box are used as constraints. The final optimized box is shown in Figure 6 The weighted strain energy of the optimized box is reduced by 5J compared with the original weighted strain energy, the mass is reduced by 0.32t, the maximum stress of the box is reduced by 5%, and the natural frequency is basically unchanged from the original box.

Claims

1. A method for optimizing the structure of a marine gearbox, characterized in that: Here are the steps: Step 1: Design the box and build a 3D model of the box; Step 2: Optimize the design of the box shape and determine the reinforcement position; Step 3: Optimize the design of the box size and the size of the ribs to reduce the weight of the box; The cabinet size optimization design includes the following steps: (1) Finite element modeling of the optimized box: import the reinforced model into HyperMesh software, determine the optimization area, perform meshing, set material properties and unit types, and apply constraints and loads; (2) Use the OptiStruct solver size optimization module to perform optimization calculations: During optimization, the goal is to minimize the box mass, and the box strain energy, maximum stress, and vibration acceleration at the box bearing seat and machine feet are used as constraints. The box structure size is used as the design variable for size optimization until the box mass is minimized and the relevant vibration indicators are met; (3) Use Hyperview software for post-processing and output of dimensionally optimized 3D model: perform secondary design based on process experience.

2. The method for optimizing the structure of a marine gearbox according to claim 1, characterized in that: The box shape optimization design includes the following steps: (1) Box 3D model processing: remove the reinforcement features in the preliminary design box 3D model to make it a large panel structure; (2) Finite element modeling: Import the processed model into HyperMesh software, determine the optimization area, perform meshing, set material properties and unit types, and apply constraints and loads; (3) Use the OptiStruct solver morphology optimization module to perform optimization calculations: determine the design variables, input the rib height, rib angle, and rib height, set the response function to the strain energy of the optimization area, set the optimization goal to minimize the strain energy, set the constraints to the natural frequency of the box, vibration acceleration, bearing seat deformation, and maximum box stress, calculate the optimal reinforcement position, design the reinforcement at the optimal reinforcement position, perform finite element analysis, and adjust the reinforcement properties until the vibration and other design indicators meet the requirements; (4) Use Hyperview software for post-processing and output of the optimized 3D model: perform secondary design based on process experience.

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