RIA: Brittleness Effects on the Structural Response of Strain-Softening Materials

应变软化是几种材料的特性 遇到土木工程。 例如，岩石、混凝土和 密实土表现出切线模量减小的特性 从初始正值变为负值， 增大 当软化涉及结构部件时， 然而，可能发生内部快速恢复不稳定性， 软化分支呈正斜率。 此类故障 即使在位移受控的情况下也是灾难性的， 必须加以预防。 本研究的目的是发展和应用一种理论， 脆性，以预测结构的整体行为 由应变软化材料组成。 弹塑性 局部应变分量采用本构关系， 虽然软化行为将根据 位移分量通过断裂的粘聚力区模型。 实验将在闭环伺服液压系统中进行 测试系统，以捕捉故障后的制度，并评估 必要的材料参数。 的软化反应 三点弯曲的混凝土梁将通过改变 几何形状、尺寸和约束，同时记录声学 故障过程中的排放。 声发射测试 作为一种可行的无损检测技术， 一种不稳定性。 这项研究将提供一个分析 解释和目前的实验证据的突变 与应变软化梁的回弹行为的对比。

Strain softening is a characteristic displayed in several materials encountered in civil engineering. For example, rock, concrete, and dense soil exhibit the behavior where the tangent modulus decreases from an initial positive value and becomes negative as strain increases. When softening is involved with a structural component, however, an internal snap-back instability may occur, with the softening branch taking on a positive slope. Failures of this type would be catastrophic even in a displacement-controlled setting and must be prevented. The objective of this research is to develop and apply a theory of brittleness in order to predict the global behavior of a structure composed of a strain-softening material. An elastic-plastic constitutive law will be adoptive for the local strain components, while the softening behavior will be described in terms of displacement components through a cohesive-zone model of fracture. Experiments will be conducted in a closed-loop, servo-hydraulic testing system to capture the post-failure regime and to evaluate the necessary material parameters. The softening response of concrete beams in three-point bending will be studied by varying the geometry, size, and constraint, while recording the acoustic emissions from the failure process. Acoustic emission testing in proposed as a viable nondestructive technique to detect the onset of an instability. This research will provide an analytical explanation and present experimental evidence of the snap-through versus snap-back behavior of strain-softening beams.