温度和内压作用下装药结构完整性分析

【作者】 韦世锋；

【导师】 鲍福廷；

【作者基本信息】 西北工业大学 ， 航空宇航推进理论与工程， 2006， 硕士

【摘要】 本文对固体火箭发动机装药结构在温度和内压作用下的完整性分析的研究内容和具体实现过程进行了系统的论述,还进行了几种典型装药结构的参数化分析的工作,该参数化分析应用了具有面向对象特性的C++Builder开发工具和ANSYS的二次开发语言APDL。由于推进剂药柱是粘弹性材料,本文对推进剂的力学松弛特性、线粘弹性力学模型、线粘弹性叠加理论、时—温等效原理、压强的影响、推进剂极限特性都做了充分论述。药柱结构完整性分析的经验公式法是历史上广泛应用的方法,并且还应用于现阶段的初步分析,本文对其进行了适当的论述,并根据经验公式编制了简单药柱结构完整性分析程序。对热结构分析和粘弹性分析的有限元公式进行了适当地推导,为热结构和粘弹性分析阐明所应有的理论知识。对ANSYS在热结构分析和粘弹性分析方面的应用做了详细地介绍。利用C++Builder和ANSYS的APDL语言开发具有参数化分析能力的程序,本文对此过程进行了适当叙述。最后给出一些分析实例,一方面证明本文有限元方法的正确性,另一方面对装药结构完整性分析过程进行较详细地论述。 在以上工作中,本文较好地完成了以下工作: 1.解决了粘弹性参数的处理问题。ANSYS对粘弹性材料的定义是分别定义弹性项和粘性项。定义弹性项时,需要输入瞬时弹性模量和泊松比。定义粘性项时需输入剪切模量和体积模量的PRONY级数表达式的非瞬时项。定泊松比的分析可以不输入体积模量的粘性项,此时体积模量为常数。在分析前,其它形式的粘弹性参数必须转化为ANSYS所需的格式。 2.解决了均匀温度场条件下的热结构分析问题。温度变化时间较长和不关心温度变化过程温度梯度引起的热应力、应变时,认为温度场均匀变化,使分析较易进行,且可得出较满意的结果。均匀温度场时,弹性和粘弹性分析都可以顺利进行。 3.解决了瞬态热结构分析问题。需要知道温度变化过程中由于温度梯度产生的应力、应变时,认为温度场是瞬态的,在空间上存在梯度。应用ANSYS提供的耦合单元很好地实现了瞬态热结构的弹性分析,可以得出任一时刻的温度场和对应的弹性应力、应变。 4.解决了温度和压强联合作用的分析问题。通过载荷步的形式将温度和压强在不同时间点施加在模型上,实现了两者联合作用条件下的结构分析。 5.初步实现了装药结构的参数化分析。应用C++Builder和ANSYS的APDL语言编制了输入界面友好的装药结构参数化程序,程序可以对典型的二维装药结构和几种简单的三维装药结构进行参数化结构分析。更多还原

【Abstract】 The research content and process of the solid propellant grain structural integrity analysis under temperature and pressure loads is discussed in this paper, and program with ability to make parametric analysis for some representative grains is made. That program is based on both C++Builder programming tool which has objective property and APDL language which is the language used in ANSYS to make advanced analysis. Discussions for propellant mechanical relaxation, linear viscoelastic models, linear viscoelastic accumulative theory, time-temperature equivalent theory and limit properties are discussed fully, because the solid propellant is a typical viscoelastic material. Since the experiential method for grain structural integrity analysis was widely used in history and is still being used in the primary design stage nowadays, it is discussed properly in this paper, and a simple program for grain structural integrity analysis is made used it. The element equations for thermal-structure analysis and viscoelastic analysis are deduced to depict the theory applied in the thermal-structure analysis and viscoelastic analysis. The process of making thermal-structure analysis and viscoelastic analysis using ANSYS is depicted in detail. The process of making the parametric analysis program using C++Builder and APDL is described in detail. At last some examples are given, on one hand to give a proven for the element method, on the other hand to give a detail description for the grain structural integrity analysis.In the work above, some are well done in this paper:1. The way to deal with the viscoelastic parameters is given. Elastic and viscoelastic items are defined separately to define the property for viscoelastic material in ANSYS. The items of shear modulus and bulk modulus which are not instantaneous are input when define the viscous items. The bulk modulus items in viscous items are not necessary to be input, when the Poison’s Ratio is constant, and this means that the bulk modulus is constant. The viscoelastic parameters given in other forms need to be transferred to the form in ANSYS.2. The thermal-structure problems under unified temperature field are solved. The temperature is presumed to change in uniformity, when the duration for temperature changes is long enough, or when the stress/strain induced by temperature gradient during the cycle of temperature loads can be ignored. The presume makes the analysis more easily, but can still get acceptable results. Further more, not only can the elastic analysis be made, but also the viscoelasticanalysis can be made.3. The process of transient thermal-structure analysis is given. When the stress/strain induced by the gradient during temperature cycles needs to be known, the temperature changes inconsistently, and has gradient in space. The elastic analysis for transient thermal-structure is well made with coupling elements offered in ANSYS. The temperature distribution and corresponding elastic stress and strain can be got at any time point.4. The combined effect of temperature and pressure is made out. By defining temperature loads and pressure loads on the model at different time in the forms of load steps, the effect of them is got.5. The propellant grain structural parametric analysis is realized in primary level. The grain structural parametric program which has a very convenient interface is made with C++Builder and APDL in ANSYS. The program can make parametric analyses for typical tow dimensional grains and several simple three dimensional grains.更多还原