阅读说明：本技术 面向发动机尾喷管可靠运动的关键结构参数优化方法 (Key structure parameter optimization method for reliable movement of engine tail nozzle ) 是由 金鑫 李寅岗 朱海天 刘璐 于 2021-06-25 设计创作，主要内容包括：本发明公开了发动机复合材料尾喷管的运动灵活度和可靠性的优化方法,包括步骤：第一步、分析影响尾喷管运动灵活度和可靠性的重要参数,确定优化对象；第二步、确认各优化对象参数的数值范围,针对这一范围进行后续的优化；第三步、制定发动机尾喷管运动性能评价指标和应力损伤失效指标；第四步、建立复合材料尾喷管的冲击动力学仿真,对各参数进行优化仿真计算；第五步、通过分析各参数对尾喷管的运动灵活度和可靠性的影响趋势,提出复合材料尾喷管销孔配合单边间隙、表面摩擦系数和驱动气压的参数选择建议指标。本发明解决了尾喷管运动灵活度低,易发生失效的问题,实现从感觉经验到理论方法、从定性摸索到定量优化的提升。(The invention discloses a method for optimizing the motion flexibility and reliability of a composite material exhaust nozzle of an engine, which comprises the following steps: analyzing important parameters influencing the motion flexibility and reliability of the tail nozzle and determining an optimized object; secondly, confirming the numerical range of each optimized object parameter, and carrying out subsequent optimization aiming at the range; thirdly, establishing an engine tail nozzle motion performance evaluation index and a stress damage failure index; fourthly, establishing impact dynamics simulation of the composite material exhaust nozzle, and performing optimization simulation calculation on each parameter; and fifthly, through analyzing the influence trend of each parameter on the motion flexibility and reliability of the tail nozzle, parameter selection suggestion indexes of the pin hole matching unilateral clearance, the surface friction coefficient and the driving air pressure of the composite material tail nozzle are provided. The invention solves the problems of low motion flexibility and easy failure of the tail nozzle, and realizes the promotion from sensory experience to a theoretical method and from qualitative groping to quantitative optimization.)

1. The method for optimizing the reliable motion of the engine tail nozzle based on the composite material is characterized by comprising the following steps of: the composite material tail nozzle is a convergent-divergent tail nozzle, the overall structure of the tail nozzle is not changed, and the motion flexibility and the reliability of the tail nozzle are improved only by changing the pin hole assembly unilateral clearance, the material surface friction coefficient and the driving air pressure parameter setting.

2. The method for optimizing the reliable motion of the composite-based engine nozzle according to claim 1, wherein: the motion flexibility and the reliability of the composite material exhaust nozzle are calibrated through a motion characteristic evaluation index and a stress damage failure evaluation index, the motion characteristic evaluation index is composed of parameters such as motion speed and motion time, and the stress damage failure index is composed of parameters such as a maximum stress value and a damage failure proportion.

3. The method for optimizing the reliable motion of the composite-based engine nozzle according to claim 2, wherein: the method for optimizing the reliable movement of the composite material engine tail nozzle comprises the following steps of:

first, analyzing influence factors and determining an optimized object

And carrying out sensitivity analysis on a plurality of assembling process parameters, working condition parameters and material surface parameters, and determining that the optimized objects are pin hole assembling gaps of the pin shaft, the surface friction coefficient of the material and driving air pressure. The unilateral clearance between the pin shaft and the pin hole specifically refers to the unilateral clearance value between the pin at each part on the engine tail nozzle and the respective pin hole. The surface friction coefficient of the material specifically refers to the friction coefficient of a pin hole cylindrical surface of a pin, and the driving air pressure specifically refers to the air pressure value applied to the periphery of the middle area between the fixed end and the sliding end of the tail nozzle.

Second, determining the optimized range of the parameters

According to the three confirmed optimization objects: the single-side gap of the pin hole, the friction coefficient of the surface of the material and the driving air pressure are optimized and calculated by selecting a proper numerical range aiming at each object, so that the optimal parameters and a better interval can be obtained in the range conveniently.

Thirdly, establishing a performance evaluation index and a failure evaluation index

And formulating a motion performance evaluation index and a stress damage failure index of the engine tail nozzle for evaluating whether the optimization degree or the optimization effect of each optimized object parameter reaches the standard or not.

Fourthly, establishing impact dynamics optimization simulation of each parameter

The influence trend of different parameter settings of the same object on the motion characteristic and the stress damage condition of the tail nozzle is explored, abaqus is used as a finite element analysis tool, and an optimized object is used as a single variable and is input into the abaqus for nonlinear dynamics analysis.

Fifthly, analyzing the influence trend of different parameters on reliable movement and providing parameter selection suggestion indexes

According to the dynamics analysis result, obtaining the variation trend of each parameter, the movement speed, the movement time, the maximum contact stress and the damage ratio of the optimized object, visualizing the variation trend into a curve relation, and analyzing the optimal parameter and the optimal interval of each optimized object by utilizing the curve relation and the optimization index.

4. The method of optimizing reliable motion of a composite-based engine nozzle according to claim 3, wherein: the material surface friction coefficient is obtained by the functional relation between the surface roughness Ra of the composite material and the friction coefficient mu, and the functional relation is as follows:

5. the method of optimizing reliable motion of a composite-based engine nozzle according to claim 3, wherein: the method comprises the following steps of:

analyzing the pins at all positions, classifying the pins at similar positions into one class, and selecting one pin from each class to analyze the initial condition calculation result;

analyzing and calculating results, and selecting a pin which has the maximum movement speed and is most easy to damage as an index reference object;

and establishing a motion performance evaluation index and a stress damage evaluation index of the reference pin.

Technical Field

The invention belongs to the field of optimized simulation of an engine tail nozzle. And more particularly, to a method for optimizing the reliable motion of a convergent-divergent composite engine nozzle.

Background

The tail pipe is an important component of the engine, and the main function of the tail pipe is to obtain forward thrust by ejecting high-temperature airflow backwards. The nozzle can be divided into an adjustable tail nozzle and a non-adjustable tail nozzle according to whether the nozzle is fixed or not. The adjustable tail nozzle can adjust the flow of the nozzle. The variable nozzle is divided into a convergent type and a convergent-divergent type according to the variation form of the sectional area, wherein the convergent-divergent type variable nozzle has better supersonic performance and is widely applied to engines of advanced warplanes and missiles. The convergent-divergent nozzle is characterized in that the inner diameter is reduced and then enlarged, and since the diameter of the middle part is minimum and the shape is similar to a narrow throat, the part is called a nozzle throat, and the nozzle realizes flow regulation through the contraction of the throat.

The tail nozzle generally works in high-temperature wake flow, and the working temperature range is approximately in the range of 800-2000K. The parts are mostly made of FRCMCs materials for bearing high temperature, and have the characteristics of high hardness, large brittleness and poor processability, so that the machining error of the parts of the tail nozzle is large, the surface quality is poor, and the problems of low speed and poor flexibility exist when the parts shrink under the condition of a complex high-temperature field; when the air pressure drive reaches the contraction limit position, a large impact load is easily generated at the key assembly connection position, high local stress and even damage failure on a key part are caused, and the reliability of the tail nozzle is seriously influenced. In recent years, the demand of China for high and new weaponry is pressing day by day, and the motion flexibility and the reliability of the tail nozzle are key factors for the normal performance of a plurality of weaponry, so that how to optimize the motion performance and the reliability of the tail nozzle has important significance.

Disclosure of Invention

The invention aims to explore the influence rule of the assembly process parameters and the working conditions of the engine tail nozzle on the motion characteristics and the local stress concentration state of the tail nozzle and form a corresponding optimization theory and design method. The improvement from sensory experience to a theoretical method and from qualitative groping to quantitative optimization is realized, an analysis optimization method is provided for the improvement of the motion performance and the reliability of the tail nozzle, and technical support is provided for the improvement of the performance level of equipment in China.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for optimizing the reliable movement of a composite material engine tail nozzle, which comprises the following steps:

first, analyzing influence factors and determining an optimized object

The motion characteristic of the engine tail nozzle is mainly influenced by the assembly process parameters, the working condition parameters and the material property, the most important of the assembly process parameters is the unilateral clearance between a connecting pin shaft and a pin hole, and the clearance between the pin shaft and the pin hole has the greatest influence on the motion flexibility of the tail nozzle; the most important of the working condition parameters is the internal and external driving air pressure of the tail nozzle, the driving air pressure determines the shrinkage and expansion speed of the tail nozzle, and the influence on the damage failure degree of the workpiece is most obvious; the most important of the properties of the material is the surface friction coefficient, and the friction coefficient has great influence on the movement speed and the flexibility of the tail nozzle.

Second, selecting the range of the parameter to be optimized

According to the three confirmed optimization objects: the single-side gap of the pin hole, the friction coefficient of the surface of the material and the driving air pressure are optimized and calculated by selecting a proper numerical range aiming at each object, so that the optimal parameters and a better interval can be obtained in the range conveniently.

Thirdly, establishing a performance evaluation index and a failure evaluation index

And formulating a motion performance evaluation index and a stress damage failure index of the engine tail nozzle for evaluating whether the optimization degree or the optimization effect of each optimized object parameter reaches the standard or not.

Fourthly, establishing impact dynamics optimization simulation of each parameter

The influence trend of different parameter settings of the same object on the motion characteristic and the stress damage condition of the tail nozzle is explored, abaqus is used as a finite element analysis tool, and an optimized object is used as a single variable and is input into the abaqus for nonlinear dynamics analysis.

Fifthly, analyzing the influence trend of different parameters on reliable movement and providing parameter selection suggestion indexes

According to the dynamics analysis result, obtaining the variation trend of each parameter, the movement speed, the movement time, the maximum contact stress and the damage ratio of the optimized object, visualizing the variation trend into a curve relation, and analyzing the optimal parameter and the optimal interval of each optimized object by utilizing the curve relation and the optimization index.

In the first step, the process of determining the important parameters is as follows: the sensitivity analysis method is used for calculating a plurality of variables of the models, and the obtained pin hole clearance, the driving air pressure and the material surface friction coefficient have the most obvious influence on the simulation calculation of the models, in other words, the pin hole clearance, the driving air pressure and the material surface friction coefficient have the greatest influence on the reliable motion of the tail nozzle and have universality. Thus, the three are confirmed as the optimization target.

In the first step, the unilateral clearance between the pin shaft and the pin hole specifically refers to the unilateral clearance value between the pin at each position on the engine tail nozzle and the respective pin hole. The driving air pressure specifically refers to the peripheral air pressure value applied to the middle area between the fixed end and the sliding end of the tail nozzle, and the peripheral driving air pressure overcomes the internal pressure of the tail nozzle to drive the throat of the tail nozzle to contract. The material surface friction coefficient specifically refers to the friction coefficient of the surface of the tail nozzle material, and when the influence of the friction coefficient on reliable movement is researched, the friction coefficients of the outer cylindrical surface of the pin shaft, the cylindrical surface of the pin hole and other contact surfaces at various positions are mainly considered. The friction coefficient is obtained by the functional relation between the surface roughness Ra of the composite material and the friction coefficient mu, and the functional relation is as follows:

in the third step, in order to carry out optimization research on the driving air pressure and the friction coefficient of the tail nozzle, an evaluation index of an optimization effect needs to be determined. Impact-oscillation in the movement process of the jet nozzle, especially the primary impact-oscillation process, is the key point of analysis, and the movement indexes related to the impact-oscillation process are concerned. In addition to the motion performance, the optimization effect needs to be evaluated from both the local stress concentration state and the damage failure condition. The composite material used by the tail nozzle belongs to a brittle material and meets the condition of the second strength criterion, so that the tensile strength and the compressive strength are taken as failure criteria. Therefore, the evaluation index specifically refers to: the speed before and after impact collision, the collision process key time node, the contraction stabilization time and the like in the movement process of the tail nozzle are used as the movement performance evaluation indexes of the tail nozzle, and the maximum tensile and compressive stress and node tensile and compressive damage failure proportion of the composite material of each pin shaft in the X, Y and Z directions are used as the local stress concentration state and damage failure evaluation indexes in the key analysis position of the tail nozzle.

In the fourth step, finite element calculation is carried out on different parameters, steps such as model creation, material attribute setting, analysis step setting, boundary condition setting and load setting, grid division and the like are required, when the grid is divided, the finite element method divides the analysis model into a plurality of smaller grid units to realize model discretization, wherein mechanical response on unit nodes is determined through integral points in the grid units, the more the grid units and the nodes on the grid units are, the more accurate the calculation result is, but the increase of the number of the grid units and the nodes leads to the remarkable increase of calculation amount; due to the existence of the floating point calculation rounding error, when the number of grid units is too large, the calculation precision is reduced due to the accumulation of the error. Therefore, the size value of the main structural grid of the jet nozzle model is set.

In the fifth step, the reliable motion specifically refers to the motion of the engine exhaust nozzle meeting the motion flexibility evaluation index and the stress damage failure evaluation index, and the parameter selection suggestion index specifically refers to the optimal numerical value suggestion and the optimal numerical value interval suggestion of each optimized object, wherein the suggestion indexes of the pin shaft and the pin hole clearance parameter are respectively proposed according to the position of the pin shaft, and the suggestion indexes of the material surface friction coefficient are respectively proposed according to the position of the pin shaft.

The optimization method for the reliable movement of the engine tail nozzle has the beneficial effects that:

according to the invention, through impact dynamics finite element simulation calculation, the assembly clearance, the friction coefficient and the driving air pressure at the pin shaft position are analyzed to generate obvious influences on the motion performance of the tail nozzle, the local stress concentration state of each pin shaft in the tail nozzle and the damage failure condition of the pin shaft, and the motion flexibility and the reliability of the tail nozzle are directly influenced. The movement performance of the tail nozzle is improved by adjusting the assembly clearance and driving air pressure, and the movement flexibility of the tail nozzle is improved; the local stress concentration state and damage condition of the pin shaft are improved by adjusting the assembly clearance and the friction coefficient, and the reliability of the tail nozzle is improved.

Drawings

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a main structure of a convergent-divergent nozzle;

FIG. 3 shows the distribution of internal and external air pressures in the exhaust nozzle;

FIG. 4 is an image of A, B, C pin velocity and displacement over time;

FIG. 5 is a graph of maximum tensile and compressive stress of the C-pin over time;

FIG. 6 is an image of the optimization evaluation index varying with the assembly gap value;

FIG. 7 is an image of the change of the optimization evaluation index with the friction coefficient;

fig. 8 is an image of the optimization evaluation index according to the driving air pressure.

Detailed description of the preferred embodiments

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Features of various aspects of embodiments of the invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention is not limited to any particular arrangement or method provided below, but rather covers all product structures, any modifications, alterations, etc. of the method covered without departing from the spirit of the invention.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

The following describes an optimization method for the reliable movement of the engine exhaust nozzle, by taking an optimization example of the reliable movement of the adjustable exhaust nozzle made of composite materials of certain types of engines:

FIG. 1 is a schematic structural diagram of a Cf/SiC material convergent-divergent type variable nozzle, and the structure has periodic repeatability in the circumferential direction. D. The E piece moves along with the AB piece and the BC piece, and the moving form of the AB piece and the BC piece is equivalent to a connecting rod sliding block system in an ideal condition. Because the machinability of the Cf/SiC composite material is poor, the function realization and the processing technology are considered, the pin shaft of the tail nozzle A, B, C is in clearance fit, and the middle value of the pin shaft and the pin hole size at each position is as follows: the diameters of the pins A to E are 6.00 mm; the diameters of the pin holes A to E are 6.40 mm; the gap value is 0.2 mm. The tail nozzle completes the throat reducing action through air pressure driving, and the driving air pressure is constant to be 0.12 MPa. As shown in FIG. 2, the pressure inside the exhaust nozzle is equal in the circumferential direction, wherein the pressure at the fixed end is 0.16MPa, the pressure at the throat position is 0.10MPa, and the pressure at the sliding end position is 0.04 MPa. The air pressure value changes linearly along the axial direction between the fixed end and the throat part and between the throat part and the sliding end.

The method for optimizing the reliable movement of the tail nozzle specifically comprises the following steps:

first, determining an optimized object

The motion characteristic of the engine tail nozzle is mainly influenced by the assembly process parameters, the working condition parameters and the material properties, and is obtained by carrying out sensitivity analysis on a plurality of assembly process parameters, working condition parameters and material surface parameters, wherein the most important of the assembly process parameters is the unilateral clearance of a connecting pin shaft and a pin hole, and the clearance value of the pin shaft and the pin hole has the greatest influence on the motion flexibility of the tail nozzle; the most important of the working condition parameters is the internal and external driving air pressure of the tail nozzle, the driving air pressure determines the shrinkage and expansion speed of the tail nozzle, and the influence on the damage failure degree of the workpiece is most obvious; the most important of the properties of the material is the surface friction coefficient, and the friction coefficient has great influence on the movement speed and the flexibility of the tail nozzle. Therefore, in order to change the throat section as required, all components of the jet nozzle mechanism should move to a specified position as quickly and smoothly as possible without damage, and the optimized objects of the convergent-divergent jet nozzle are the unilateral clearance of pin holes of the pin shaft, the surface friction coefficient of the material and the driving air pressure.

The unilateral clearance between the pin shaft and the pin hole specifically refers to the unilateral clearance value between the pin at each part on the engine tail nozzle and the respective pin hole. The material surface friction coefficient specifically refers to the friction coefficient of the surface of the tail nozzle material, and the outer cylindrical surface of the pin shaft and the cylindrical surface of the pin hole at each position are mainly considered when the influence of the friction coefficient on reliable movement is researched. The friction coefficient is obtained by the functional relation between the surface roughness Ra of the composite material and the friction coefficient mu, and the functional relation is as follows:

the driving air pressure specifically refers to the peripheral air pressure value applied to the middle area between the fixed end and the sliding end of the tail nozzle, and the peripheral driving air pressure overcomes the internal pressure of the tail nozzle to drive the throat of the tail nozzle to contract.

Second, determining the optimized range of the parameters

According to the three confirmed optimization objects: the method comprises the following steps of selecting a proper numerical range for optimization calculation aiming at each object, and obtaining optimal parameters and a better interval in the range.

In the structure of the tail nozzle, the design values of the assembly gaps of the pin A, the pin B, the pin C, the pin D, the pin E and the pin hole are all 0.2mm, the peripheral driving air pressure of the tail nozzle is 0.12MPa, and the surface friction coefficient of each pin shaft and the pin hole is 0.29 through conversion calculation of the surface roughness friction coefficient. Setting a reasonable parameter optimization range according to the actual condition of the tail nozzle, and calculating the assembly clearance between the pin shaft and the pin hole once every 0.05mm, wherein the optimization range is 0.05-0.35 mm; for the driving air pressure, the optimized range is 0.1-0.18 MPa, and the calculation is carried out once every 0.01 MPa; and (3) calculating the surface friction coefficient of the pin hole of the pin shaft once every 0.01, wherein the optimized range is 0-0.5.

Thirdly, establishing relevant indexes of reliable movement of the tail nozzle

In order to carry out optimization research on the driving air pressure and the friction coefficient of the tail nozzle, an evaluation index of an optimization effect needs to be determined. In order to ensure the effectiveness of relevant indexes, firstly, impact dynamics simulation calculation is carried out on initial data, the contact condition of pins and pin holes at each position is specifically analyzed, the main structure part of the jet nozzle can be simplified due to the fact that the integral model of the jet nozzle is complex and the circumferential structure of the jet nozzle is periodic, the enlarged part of the jet nozzle in the figure 1 is a simplified structure, in order to clearly express the motion form of the pin shaft, the axial direction and the radial direction of the jet nozzle are appointed, the difference between the motion states of a pin D and a pin A is small, the difference between the motion states of a pin E and a pin C is small, and therefore only pins at three positions A, B, C are selected for comparison. The movement speed and displacement of the pin at three positions are calculated by initial data simulation as shown in fig. 4, and it can be seen that the maximum movement speed and displacement of the pin C are greater than those of the pins a and B, and the stress borne by the pin C in a collision is also maximum. Structurally, the C pin is matched with a pin hole on the BC piece on one hand and is matched with a pin hole on a tail mechanism of the tail jet pipe on the other hand. Because the tail device of the tail nozzle plays a role in limiting the movement of the tail nozzle, the movement freedom degree of the tail nozzle is limited to be only in the axial direction of the tail nozzle, so that the C pin can generate unidirectional main movement along the axial direction of the tail nozzle along with the pin hole on the C pin, and the analysis difficulty caused by the complex movement direction and movement form, excessive vibration and unstable state is avoided. In conclusion, the speed-time and displacement-time curves of the pin C are mainly used in the pin shafts A, the pin B and the pin C, and the pin B is used as an auxiliary part to carry out analysis on the overall motion state of the tail nozzle, so that the analysis is most suitable.

And (5) carrying out unfolding analysis on the C pin in the X, Y and Z directions in the movement process of the tail nozzle. Extracting and processing data of each node on the C pin in the simulation model, and acquiring data of maximum tensile stress and maximum compressive stress on the C pin at each moment, wherein the tensile stress and the compressive stress of the C pin in the X, Y and Z directions have the following trend characteristics in the movement process of the tail nozzle as shown in FIG. 4:

(1) the maximum level of the compressive stress on the C pin is obviously higher than that of the tensile stress, wherein the compressive stress is mainly in the X, Y direction, and the compressive stress in the Z direction is not obvious; tensile stress is mainly in the Z direction, and is not significant in the X, Y direction.

(2) The stress peak value of the C pin occurs in an acceleration stage before the primary impact and in two impact-oscillation stages, so that the time interval from the initial state to the completion of the secondary impact is a main object of stress analysis of the C pin in the movement process of the tail nozzle.

Based on the typicality of the C pin and the similarity of the structures of all pin shafts, the stress characteristic of the C pin is suitable for all pin shafts in the tail nozzle, and subsequent parameter optimization research is carried out by taking the stress characteristic as reference.

Based on the characteristics, the sports performance evaluation indexes and index symbols are formulated as shown in the following table:

the Cf/SiC composite material used for the tail nozzle has small change of the strength limit value in the range, the composite material belongs to a brittle material and meets the condition of a second strength criterion, and therefore the tensile strength and the compressive strength are taken as failure criteria. The composite material is an orthotropic material on the macroscopic scale, has different mechanical properties in three main directions of a material coordinate system X, Y, Z, and the strength limit values in all directions are shown in the following table:

the stress index and damage failure index and their symbols are shown in the following table:

fourthly, establishing the dynamic simulation of the impact of the tail nozzle

Numerical values in the optimization ranges of the parameters are respectively input into ABAQUS for impact dynamics simulation calculation, and an explicit algorithm which is suitable for analysis of impact-equal-strength nonlinear problems, has no convergence problem and is higher in calculation efficiency is selected in the embodiment; the contact type selects a universal contact, and the normal contact behavior and the tangential contact behavior in the universal contact algorithm are respectively researched. Defining 'hard contact' behavior in a normal direction through a penalty function mode according to the impact working condition and the material characteristic; the grid type is set as: the C3D8R mesh is used for key parts, contact positions and body parts of the model, and the C3D10M mesh is used for non-important parts with complex shapes.

Fifthly, analyzing the simulation data and proposing suggestion indexes

And performing data extraction and processing on the simulation analysis result to obtain the image relationship between the motion performance evaluation index, the stress damage evaluation index and the optimization object, wherein the image relationship between the evaluation indexes and the optimization object is selected as an example because the number of the evaluation indexes is too large and the analysis method is similar.

Optimizing object one, pin hole matching unilateral clearance

The motion characteristic analysis takes the difference between the absolute values of the C pin velocities before and after the initial impact collision and the contraction stabilization time of the jet nozzle as an example, such as the variation trend of the partial motion performance evaluation index and the assembly clearance shown in FIG. 5, and the difference between the absolute values of the C pin velocities before and after the initial impact collision (i.e., the velocity loss caused by the collision) Δ ν^{Impact Loss}The value shows a cubic curve trend along with the change of the assembly gap value, when the assembly gap is 0.05-In the range of 0.15mm and in the range of 0.25-0.35mm,. DELTA.v^{Impact Loss}The value decreases as the fit clearance increases; when the fitting clearance is in the range of 0.15-0.25 mm, Δ v^{Impact Loss}The value increases as the assembly clearance increases. Δ v when the fitting clearance is 0.05mm^{Impact Loss}The value is maximum and the fitting clearance is minimum at 0.20 mm. Contraction stabilization time t of tail nozzle^{Initial-Stable}The values tend to increase first and then to a stable value as the assembly gap increases. When the assembly gap is in the range of 0.05-0.20mm, t^{Initial-Stable}The value increases as the assembly clearance increases; when the assembly gap is in the range of 0.20-0.35mm, t^{Initial-Stable}The values fluctuate around a small amplitude of 23ms, essentially tending to a steady value.

The stress variation of the pin shaft is A, C pin shafts as an example, as shown in fig. 6, the variation trend of the maximum tensile and compressive stresses in each direction of the A, C pin along with the assembly clearance is shown, the maximum tensile and compressive stress values in each direction of the pin a increase first and then decrease along with the increase of the assembly clearance, the maximum tensile and compressive stress values in each direction of the pin a reach the maximum value when the clearance value is 0.10mm, the maximum tensile and compressive stress values in each direction of the pin a obviously decrease along with the increase of the clearance value when the clearance value is within the range of 0.10-0.30mm, the decrease is slowed down when the clearance value is within the range of 0.30-0.35mm, and the overall optimization is realized when the clearance value is 0.35 mm. The value of the maximum compressive stress in the Y direction in the C pin is increased along with the increase of the clearance value, the trend of the maximum compressive stress in the Z direction is not obvious, and the value is comprehensively optimal when the clearance value is 0.05 mm. The stress damage failure condition of the pin shaft needs to be counted by integrating the stress condition and the strength index on each shaft, the analysis process is similar to the analysis process of the stress change condition, and the detailed chart and the detailed steps are not repeated.

In summary, from the consideration that the maximum stress value and the damage failure ratio value on the pin shaft are minimum and the better movement performance of the tail nozzle is met, the clearance value of 0.05mm is adopted at the pin C position, the clearance value of 0.20mm is adopted at the pin D position, and the clearance values of 0.35mm are adopted at the pin A, the pin B and the pin E.

Optimizing the surface friction coefficient of object two

The surface friction coefficient and the variation trend of the motion characteristic index of the pin shaft are determined by selecting the difference delta v between the absolute values of the C pin speeds before and after the initial impact collision^{Impact Loss}And the contraction stabilization time t of the tail nozzle^{Initial-Stable}For the purpose of example, the analysis, as shown in figure 7,when the friction coefficient is in the range of 0.00-0.16, the difference Deltav between the absolute values of the C pin velocities before and after the initial impact collision^{Impact Loss}The value fluctuates and increases with increasing friction coefficient; at a friction coefficient in the range of 0.16-0.50, Δ v^{Impact Loss}The values decrease with increasing coefficient of friction. When the friction coefficient is in the range of 0.00-0.23, the contraction stabilization time t of the tail nozzle^{Initial-Stable}The value decreases stepwise with increasing friction coefficient; t is in the range of 0.23-0.50 at the friction coefficient^{Initial-Stable}The values show a tendency to fluctuate as the coefficient of friction increases.

The variation trend of the friction coefficient and the stress of the surface of the pin shaft is analyzed by taking an A, C shaft as an example, as shown in fig. 8, the stress in the A, C pin is mainly the maximum tensile stress in the Z direction and the maximum compressive stress in the Y direction, secondly, the maximum tensile stress in the Y direction and the maximum compressive stress in the Z direction, and the maximum tensile stress in the X direction and the maximum compressive stress in the Y direction are not significant, so that the maximum tensile stress in the Z direction and the maximum compressive stress in the Y direction are taken as main evaluation criteria when the integral condition of the maximum tensile stress and the compressive stress in each direction is comprehensively considered. The conditions of the pin A and the pin C are similar, the maximum tensile stress value and the maximum compressive stress value in each direction show a reduction trend along with the increase of the friction coefficient, and the whole optimal condition is realized when the friction coefficient is 0.50. The method for analyzing the relationship between damage failure and friction coefficient is approximate and is not repeated.

In summary, from the consideration that the maximum stress value and the damage failure ratio value on the pin shaft are minimum and the influence on the movement performance of the tail nozzle in the contraction process is reduced, the friction coefficients of the pin A, the pin B and the pin C are respectively controlled to be more than 0.37, 0.38 and 0.44, and the friction coefficient of the pin D is controlled to be in the range of 0.20-0.44. If stress and damage failure states are considered seriously, the friction coefficient of the E pin is controlled to be in the range of 0.00-0.05; if the mechanical performance of the E pin part is sacrificed, the overall motion performance of the tail nozzle is improved, and the friction coefficient of the E pin can be controlled to be in the range of 0.22-0.23. The improvement of the motion performance of the tail nozzle in the contraction process by adjusting the friction coefficient of the C pin position should be avoided as much as possible.

Optimizing object three, driving air pressure

The variation trend of the driving air pressure and the motion characteristic index is obtained by selecting the difference delta v between the absolute values of the C pin speeds before and after the initial impact collision^{Impact Loss}And the contraction stabilization time t of the tail nozzle^{Initial-Stable}For the purpose of example, analysis is made as shown in FIG. 8 for the difference Δ v between the absolute values of the C pin velocities before and after the initial impact collision^{Impact Loss}The value fluctuates greatly along with the change of the driving air pressure, and the integral trend is not obvious. Δ v at 0.17MPa^{Impact Loss}The local maximum value at 0.11MPa is close to the maximum value; Δ v at 0.13MPa^{Impact Loss}Has a minimum value of 0.10MPa^{Impact Loss}The value is close thereto. Contraction stabilization time t of tail nozzle^{Initial-Stable}The value shows a secondary reduction trend along with the increase of the driving air pressure, the reduction speed is gradually slowed down, and the value basically approaches to a stable minimum value within the range of 0.16-0.18 MPa.

The variation trend of the surface friction coefficient and the stress of the pin shaft is analyzed by taking A, C shafts as an example, as shown in FIG. 8, when the driving air pressure of the pin A is in the range of 0.10-0.18MPa, the maximum stress value of the pin A in each direction is increased along with the increase of the driving air pressure; when the driving air pressure is in the range of 0.10-0.17 MPa, the maximum stress values in other directions except the maximum pressure stress in the Y direction on the A pin are increased, slowed down and reduced along with the increase of the driving air pressure; the maximum stress value of the C pin in each direction is rapidly increased when the driving air pressure is increased from 0.10MPa to 0.11MPa, and the maximum stress value of the C pin in each direction is gradually increased or even decreased along with the increase of the driving air pressure when the driving air pressure is in the range of 0.17-0.18 MPa. The analysis method of the relationship between the damage failure and the driving air pressure is similar and is not repeated.

In conclusion, considering the motion performance of the tail nozzle in the contraction process and the maximum stress and damage failure proportion on the pin shaft, the driving air pressure is controlled to be in the range of 0.11-0.14MPa, and when the motion performance of the tail nozzle in the contraction process is emphasized, a larger value can be adopted in the range; when the local stress concentration and damage failure states of the pin shaft in the tail nozzle are expected to be improved as much as possible and the reliability of the tail nozzle is concerned, a smaller driving air pressure is adopted in the range.