Wood is a common flammable material in the building fire and the dominant fuel in the wildland fire. In this work, disc wood slices were examined under irradiation to characterize the smoldering burning and the corresponding deformation behaviors. Due to interactions between chemical reactions and thermomechanical stresses, four successive deformation stages were observed and hypothesized: (Ⅰ) drying shrinkage to ∪ shape, (Ⅱ) irradiation-driven thermal expansion to ∩ shape, (Ⅲ) pyrolysis shrinkage to ∪ shape, and (Ⅳ) oxidation-driven thermal expansion to ∩ shape. For these 5–15 mm thick samples, the degree and occurrence of these deformation stages are sensitive to the aspect ratio (i.e. D/δ). Increasing the slice thickness decreases the deformation in the first three stages but increases the deformation of the fourth stage. These experimental observations are qualitatively reproduced by a 2-D finite-element numerical model, coupling 3-step heterogeneous kinetics with a thermomechanical solver. Modeling results further verified the underlying heterogeneous processes (dehydration, pyrolysis, and oxidation) and thermomechanical stresses (thermal expansion and pre-stress) for each deformation stage. This study helps understand the influence of burning processes on the deformation of wood and the failure of timber structures.

木材是建筑火灾中常见的易燃材料，是荒野火灾中的主要燃料。在这项工作中，在辐照下检查了圆盘木片，以表征闷烧和相应的变形行为。由于化学反应和热机械应力之间的相互作用，观察到并假设了四个连续的变形阶段：（Ⅰ）干燥收缩成to形，（Ⅱ）辐射驱动的热膨胀成∩形，（Ⅲ）热解收缩成∪形，和（Ⅳ）氧化驱动的热膨胀成∩形。对于这些5-15 mm厚的样品，这些变形阶段的程度和发生情况对长宽比（即 D / δ）。切片厚度的增加会减少前三个阶段的变形，但会增加第四阶段的变形。这些实验观察结果由二维有限元数值模型定性地再现，该模型将3步异质动力学与热机械求解器耦合在一起。建模结果进一步验证了每个变形阶段的潜在异质过程（脱水，热解和氧化）和热机械应力（热膨胀和预应力）。这项研究有助于了解燃烧过程对木材变形和木材结构破坏的影响。