【作者】 赵宝虎；

【导师】 亢一澜； 侯振德；

【作者基本信息】 天津大学 ， 固体力学， 2009， 博士

【摘要】 冲击问题具有重要的工程应用背景。譬如机械部件间的碰撞、鸟撞飞机、冲压成型、创伤性颅脑损伤等都是常见的冲击问题。近年来,因军事防护工程中涉及的装甲防护、地下工程防护等问题,冲击问题越来越引起了国内外研究者的关注。由于冲击过程中,物体的材料性质、形状尺寸、冲击接触方式等都是影响冲击结果的主要因素,因此,从理论上对其进行准确的描述或者用数值方法对其进行仿真模拟都存在一定的困难。如进一步考虑冲击过程中接触区域的变化及摩擦效应等因素,冲击问题则变得更为复杂。目前只有少数的简化的冲击问题给出了理论解或者近似的理论解,很多实际的冲击应用问题都超出了这些解的适用范围。因此,随着实验技术的不断进步,从实验方法入手分析研究冲击问题具有重要的科学意义与工程应用背景。冲击问题中,杆形射弹与弹性材料的冲击问题是一类具有广泛应用背景的典型问题,已经有了一些相关的理论分析方面研究成果,但仅有少量的实验工作,且冲击速度较低,小于2m/s,未见有系统的实验研究成果发表。本文从实验的角度系统地研究了杆形射弹与弹性材料的冲击问题,分析了冲击初速度、射弹材料性质、被冲击物材料性质及几何特性等因素对射弹中应力波的影响,讨论了仅通过射弹中应力波的信息来分析被冲击物的材料特性和几何性状的可行性。本文的另一部分工作是用实验的方法对盾构始发阶段的盾构反力架进行安全监测。盾构掘进施工是一种先进的隧道施工方法,在我国的隧道建设中正发挥着重要作用。盾构始发阶段是盾构工法的重要一环,施工难度,事故多发,而盾构反力架是在盾构始发阶段为盾构机掘进提供反作用力的机构,其安全稳定性关系着盾构始发施工的成败。在本文工作中,首先利用ABAQUS6.5有限元软件对盾构反力架在设计极限载荷作用下的应力分布进行了数值计算,进而结合数值结果与现场工况可行性,设计了反力架监测点的电测应变传感器优化布局方案,进行了历时近四个月的现场跟踪监测。通过丰富的实测数据,对盾构施工始发阶段反力架的载荷分布以及变化进行了分析,对反力架在盾构施工中的功能与作用进行了科学评价,为盾构施工中的反力架的强度分析与优化设计提供了原始资料,也对今后合理适时拆除反力架提供了实验依据和指导。更多还原

【Abstract】 The impact problems are important in engineering field, such as collision between components of mechanical devices, bird-impact to aircraft, stamping and forming, traumatic craniocerebral injury, etc. In recent years, impact problems have been paid more attentions by the researchers in the applications in military field, including the armor protections and underground engineering protections. In an impact problem, the process is mainly affected by material properties, shapes and sizes, impact modes of the impact objects, and etc. Consequently, it is difficult to describe an impact process by an exact theoretical model or through some numerical simulation methods only. Furthermore, the more factors to be considered, such as changes of contact area and the friction effects, the more complex the impact problem will become. Hitherto, only a few approximate theoretical solutions have been achieved, but most of practical problems exceed the application ranges of these theoretical solutions. Therefore, it is significant for the academic investigations and engineering applications to study and analyze the impact problems by new experimental methods.It is a representative impact problem to project a bar to an elastic solid. Some theoretical results have been published, but only a few experimental researches have been done with low impact velocities. There is still a lack of systematic experimental analysis work as yet. In this work, the impact problem of the long-bar projectile with elastic solid is studied by means of experiments. The effects of impact factors on stress waves, such as initial impact velocity, material properties of the projectiles and impacted solids, geometric characteristics, are analyzed based on a series of experiments. Moreover, it is also discussed that the possibility for identification of the material properties and geometric characteristics from experimental information of the impact stress waves.The other work of this thesis is the experimental analysis for the safety of the shield counterforce frame in the shield originating stage. Shield method is a kind of advanced tunnel construction method, which is widely used in the tunnel construction in our country. As one of the important component of the shield system, the shield counterforce frame are used to offer the crutch force for shield excavation in the begin stage of the tunnel construction, and its safety is related with the whole shield project. In this work, the strength of the shield counterforce frame under the design limit load is simulated by Abaqus6.5 first. Using numerical results, an optimization layout of the electrometric strain sensors is designed according to the feasibilities in the on-site conditions. Then, the real-time stresses in the frame are monitored during four months. Based on the achieved testing data, the stress distributions are analyzed and the function and efficacy of the shield counterforce frame in the shield construction are evaluated.更多还原