煤炭是我国的主体能源和重要原料，为国民经济的持续快速健康发展做出了不可磨灭的历史贡献。液压支架是重要的综采装备之一，是现代采煤安全防护、作业空间扩大和采煤效率提高的关键。立柱作为液压支架的主要支撑部件，具有升降推移、保持平衡、缓冲过载冲击等作用，其安全性和可靠性决定了液压支架的承载特性，因此，对立柱进行寿命预测，为制定合理的检修维修计划提供理论指导，对降低煤炭企业生产运营成本，提高煤矿开采效率具有重要意义。

目前常采用理论计算或疲劳试验对立柱的疲劳寿命进行预测，但传统理论计算忽略了材料性能、外部载荷等不确定因素带来的风险，进行疲劳试验只能获得几个或多个点的试验数据，不能全面确认其疲劳寿命且耗费大量时间，所以需要研究一种考虑立柱实际载荷条件的疲劳寿命预测方法，本文主要研究内容如下：

为了确定立柱的危险部位，对立柱进行受力分析，分析过程中考虑由于存在配合间隙而产生的偏移问题，进而考虑附加弯矩对立柱受力的影响。依据立柱的结构特点和受力状态，提出具有初始变形和初始挠度的简支梁模型，结合胡克定律和挠曲轴微分方程综合计算得到立柱各段最大挠度和最大弯矩。通过对立柱各段受力分析，求出各段的最大应力，确定立柱的危险部位同时对强度进行校核，结果表明立柱即使承受1.5倍载荷也不会发生强度破坏，最大应力位于中缸偏上与活柱底部接近处。通过对比求解临界载荷方法，选择能量法对立柱稳定性进行校核，结果表明在立柱完全伸出的情况下不会失稳。

基于某工作面综采液压支架立柱内腔压力实测数据编制程序载荷谱，利用雨流计数法对载荷数据进行统计分析，通过假设检验确定统计结果的数学模型，应用核密度估计确定概率密度函数，在此基础上得到能够代表立柱载荷时间历程的二维载荷谱。为了得到可直接实施疲劳试验的程序载荷谱，利用波动中心法对二维谱进行降维处理，得到可直接用于疲劳寿命计算的一维载荷谱。

结合立柱结构的特点，用Solidworks建立了立柱三维模型，同时利用ABAQUS建立了立柱的有限元模型。通过材料设置、网格划分和施加接近于缸体实际受载工况的约束条件，构件合理的离散化模型，计算得到静载过载压力下的结果，进而确定立柱的最大位移和最大应力都发生在中缸。得到了各部件的应力应变云图，并与第三章理论计算得到的结果进行对比，各构件最大应力值大小几乎相同，立柱易发生危险部位也相同，表明有限元模型是正确的。使用局部应力应变法，基于线性累积损伤理论，结合材料的疲劳特性曲线和立柱的载荷谱，通过FE-safe软件定义材料属性和疲劳累积算法，实现对立柱疲劳寿命预估，根据立柱整体寿命云图，确定在工作过程中易发生疲劳破坏的部位主要集中是在中缸。

Coal is the main energy source and the important raw material in China, which has made an indelible historical contribution to the sustained, rapid and healthy development of the national economy. Hydraulic support is one of the most important fully mechanized coal mining equipment, and it is the key to modern coal mine safety protection, expanding working space and improving mining efficiency. As the main supporting component of the hydraulic support, the upright post has the functions of lifting and moving, maintaining balance and buffering overload impact. Its security and reliability determine the bearing characteristics of the hydraulic support. Therefore, the life prediction of the pillar provides theoretical guidance for making a reasonable maintenance plans, and is of great significance for reducing the operating costs of coal enterprises and improve the efficiency of coal mining.

At present, theoretical calculation or fatigue test is usually used to predict the fatigue life of the column, but the traditional theoretical calculation ignores the risks caused by uncertain factors such as material properties and external loads. Fatigue tests can only obtain test data from several points or points, and it cann't completely confirm the fatigue life, and it takes a lot of time. Therefore, it is necessary to study a method of fatigue life prediction considering the actual load of the column. The main contents of this paper is as follows.

In order to determine the dangerous position of the column, the stress of the column is analyzed. In the process of analysis, the deviation caused by the matching gap is considered, and then the influence of additional bending moment on the stress of the column is considered. According to the structural characteristics and stress state of the column, a simply supported beam model considering initial deformation and initial deflection was proposed, and the maximum deflection and bending moment of each section of the column are obtained by combining Hooke's law and crankshaft bending differential equation. Through the stress analysis of each section of the column, the maximum stress of each section is found out, and the dangerous position of the column is determined. At the same time, the strength of the column is checked. The results show that the strength of the column will not be destroyed even under the load of 1.5 times, and the middle column is the most dangerous position of the column. By comparing the solutions of critical load, the most suitable method is selected, and the stability of the column is checked. The results show that when the column is fully extended, it will not lose stability.

Based on the measured load spectrum of fully mechanized mining hydraulic support column in a working face, the rain-flow counting method is used to statistically analyze the load data, the mathematical model of the statistical results was determined by the hypothesis testing method, and the probability density function was determined by the maximum likelihood estimation method. On this basis, the two-dimensional load spectrum representing the column load history is obtained. In order to obtain the programmed load spectrum which can be used for fatigue test directly, the one-dimensional load spectrum which can be used for fatigue life calculation is obtained by using the wave center method to reduce the dimension of the two-dimensional spectrum.

Combined with the characteristics of the column structure in this paper, the three-dimensional model of the column is established by Solidworks and the finite element model of the column is established with ABAQUS. By setting materials, meshing and imposing constraints close to the actual stress situation of the cylinder, the members are discretized, analyzed and calculated reasonably, and the results under static overload pressure are obtained, and then it is determined that the maximum displacement and maximum stress of the column occur in the middle cylinder. The reasonable discrete model of the member is analyzed and calculated, and the results under static load and overload pressure are obtained, so as to determine the maximum displacement and stress of the center column. The accuracy of the finite element model is verified theoretically and experimentally, which provides data support for the later life prediction of the column. Based on the results of static strength analysis, combined with the one-dimensional load spectrum compiled according to the measured load, the material properties and fatigue accumulation algorithm are defined by FE-SAFE software, and the fatigue life prediction of columns is realized. The results show that the cylinder is the weakest part of the column, so attention should be paid to the use of the cylinder in the design and use.

Based on the research work of the paper, a strength analysis method considering the column under off-load condition is proposed. Taking the load spectrum compiled by the measured load as the theoretical basis for calculating the fatigue damage of the column, it provides theoretical and data support for the use and maintenance of the hydraulic support column under actual service conditions.

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