摘要:
加工与装配的公差导致间隙在工程结构中广泛存在，强动载下间隙内可能产生威胁结构可靠性与安全性的间隙射流，而间隙射流的形成机制与传统高速金属射流不同，其形成过程尚需进行系统的研究。基于二级轻气炮对带有间隙的金属钨样品进行超高速冲击加载实验，通过高速分幅照相系统记录了间隙射流的形成及演化过程。采用ANSYS Autodyn软件建立了预测间隙射流形成的数值模型，并基于代表性实验获取的射流形态及头部速度历史验证了该数值模型的适用性。通过调整数值模型中的飞片速度、间隙宽度和间隙半角，分别研究了这三者对间隙射流形成的影响，分析了定常射流模型的局限性。在此基础上，结合数值模拟结果，提出了预测间隙射流头部速度与质量的经验模型。研究表明，基于欧拉方法建立的数值模型能够较为准确地预测强动载下间隙射流的形成。加载压力是控制射流头部速度与质量的主要因素，随着加载压力的增加，射流头部速度与质量也相应增加。间隙宽度与间隙半角对射流头部速度的影响较小，但其质量随间隙宽度与间隙半角的增加呈线性增长。由于间隙闭合速度的估算存在较大误差，定常射流模型未能准确预测间隙射流的形成，而所提出的经验模型与数值模拟结果具有较好的吻合度。
Abstract:
Tolerances in machining and assembly often result in gaps in engineering structures. Under strong dynamic loading, gap jets may form within these gaps, posing a threat to the reliability and safety of the structure. However, the formation mechanism of gap jets differs from that of traditional high-speed metal jets, and its formation process still requires systematic research. Based on a two-stage light gas gun, hypervelocity impact loading experiments were conducted on tungsten samples with gaps. The formation and evolution of the gap jet were recorded using a high-speed framing camera. A numerical model for predicting the formation of gap jets was established using ANSYS Autodyn. The applicability of the numerical simulation method was validated by comparing the numerical results with the jet morphology and head velocity history data obtained from a representative experiment. By adjusting the flyer velocity, gap width, and gap half-angle in the numerical model, the effects of these three factors on the formation of the gap jet were studied. The variations in the gap jet head velocity and mass with respect to these factors were obtained, and the limitations of the steady-state jet model were analyzed. Based on the findings from numerical simulations, an empirical model was developed to predict the jet head velocity and mass. The results show that the numerical model based on the Eulerian method can accurately predict the formation of the gap jet under strong dynamic loading. Loading pressure is the main factor controlling the jet head velocity and mass; as the loading pressure increases, both the jet head velocity and mass increase accordingly. The gap width and half-angle have little effect on the jet head velocity, but the mass increases linearly with the gap width and half-angle. Due to significant errors in estimating the gap closing velocity, the steady jet model fails to accurately predict the formation of the gap jet. In contrast, the developed empirical model shows good agreement with the numerical results.
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