Stanciu Mariana D, Teodorescu Horațiu D, Vlase Sorin
Department of Mechanical Engineering, Transilvania University of Brașov, B-dul Eroilor 29, 500036 Brașov, Romania.
Polymers (Basel). 2020 Sep 23;12(10):2176. doi: 10.3390/polym12102176.
The mechanical properties of wood, respectively the elastic, plastic, and strength properties, depend on a large number of factors, due both to its structural and physical characteristics, as well as to the size, direction, nature, and speed of application of forces. Wood, generally considered to be a viscous-elastic material, has creep deformations over time under the effect of a constant load. In this study the behavior of pine wood samples was investigated due to its large utilization in different finished products, such as roof construction, furniture, outdoor applications, garden furniture, and toys. The paper aims to analyze the viscoelastic behavior of pine wood subjected to cyclically loading to traction-compression with different loads (1 kN; 1.5 kN; 2 kN), applied at different speeds (1 mm/min; 10 mm/min). It was observed that, at low speeds (1 mm/min) and low intensities of the applied force, it was possible to distinguish the three creep regions specific to wood: the primary area (primary flow), the secondary area, and finally the tertiary creep. As the force increases, the law of variation of the wood flow changes. The degradation of longitudinal elasticity modulus occurs with the increase of the number of cycles, so after 20 alternating symmetrical cycles of traction-compression of the pine wood samples, there is a decrease of its values by 35%.
木材的力学性能，即弹性、塑性和强度性能，取决于大量因素，这既归因于其结构和物理特性，也归因于力的大小、方向、性质和施加速度。木材通常被认为是一种粘弹性材料，在恒定载荷的作用下会随时间产生蠕变变形。在本研究中，由于松木在不同成品中的广泛应用，如屋顶建筑、家具、户外应用、花园家具和玩具等，对松木样本的行为进行了研究。本文旨在分析在不同载荷（1 kN；1.5 kN；2 kN）和不同速度（1 mm/min；10 mm/min）下循环拉伸-压缩加载时松木的粘弹性行为。观察到，在低速（1 mm/min）和低施加力强度下，可以区分木材特有的三个蠕变区域：初级区域（初级流动）、次级区域，以及最后的三级蠕变。随着力的增加，木材流动的变化规律发生改变。纵向弹性模量会随着循环次数的增加而退化，因此在对松木样本进行20次交替对称的拉伸-压缩循环后，其值下降了35%。
