WOOD RESEARCH Volume 70, Number 4, 2025
JINGGUI WANG, MING LI, SAIYIN FANG, TINGTING DENG, JIAXIN GUO, ERZHUANG ZHAI, and WENTAO XU

THE STUDY ON THE DAMAGE CHARACTERISTICS OF PINUS SYLVESTRIS VAR. MONGOLICA UNDER DIFFERENT MOISTURE CONTENTS

This study investigated the effects of moisture content (0%, 12%, 20%, 30%, 40%, 50%) on the mechanical behaviour and damage evolution of Pinus sylvestris var. mongolica three-point bending tests. A Weibull distribution model quantified damage progression, extracting scale (λ) and shape (k) parameters. Results revealed moisture regulated failure mechanisms, Low moisture (≤20%) induced brittle fracture (high k, low λ) with tensile crack dominance and stress concentration. High moisture (≥30%) promoted ductility (low k, high λ) via enhanced λ, driven by shear cracks. Mixed cracks persisted across all stages. Moisture altered cell wall plasticization, inter-fibre friction, and interfacial bonding, modulating damage evolution. Weibull modelling effectively captured stage dependent damage variable trends. Increased moisture facilitated fibre slippage and interlayer shear through lubrication and cell wall softening.This work establishes quantitative links between moisture content, mechanical response, and micromechanical damage mechanisms in wood, providing insights for moisture dependent structural applications of engineered timber.

WOOD RESEARCH Volume 70, Number 3, 2025
ERZHUANG ZHAI, SAIYIN FANG, MING LI, TINGTING DENG, BOWEN ZHANG, JIAXIN GUO, KEFEI CHEN, and KUN DU

Research on clustering identification of acoustic emission events in the process of wood crack propagation using PCA

This study presents a methodology for feature extraction and identification of acoustic emission (AE) events during wood crack propagation utilizing Principal component analysis (PCA) and enhanced K-means clustering algorithm. Experimental setups included double cantilever beam (DCB) for mode I crack propagation analysis and three-point bending test for mixed-mode crack propagation assessment. Various AE parameters, such as amplitude, duration, absolute mean value, peak frequency, and frequency centroid, were computed. PCA applied for dimensionality reduction to extract principal components and eliminate redundant information. The optimal number of clusters was determined using a combination of the elbow method and the Davies-Bouldin index to classify damage modes. Results indicate that the principal components contribute to 88.5% and 92% of the variance in the two tests, respectively, yielding three distinct types of AE events in both crack propagation scenarios. Specifically, high-frequency, low-amplitude signals correspond to microcrack initiation; low-frequency, low-amplitude signals signify interface delamination; and high-amplitude, long-duration events indicate mode I opening macroscopic damage (high frequency) and mixed-mode macroscopic failure (low frequency).

WOOD RESEARCH Volume 70, Number 2, 2025
ZHIYING TIAN, SAIYIN FANG, MING LI, TINGTING DENG, ERZHUANG ZHAI, CHUMIN CHEN, and YONGCHUAN WU

THE ANISOTROPIC VELOCITY MODEL OF INTERNAL ACOUSTIC EMISSION SIGNALS IN ZELKOVA WOOD AND THE INFLUENCE OF HOLES ON THEIR PROPAGATION PROCESS

In this article, an acoustic emission (AE) source was generated through pencil-lead break (PLB). On Zelkova schneideriana specimens featuring central through-holes with diameters ranging from 8 to 16 mm, the time-difference-of-arrival (TDOA) in combination with the least squares fitting approach was utilized to establish an anisotropic model of the AE wave velocity within the wood as it varies with the detection angle. Then, a pulse signal was generated through a signal generator to analyze the influence of the holes on the peak values of AE signals at different angles. The results indicate that when the propagation angle is less than 80°, the AE wave velocity rises rapidly with the increase of the angle and eventually approximates the longitudinal wave velocity along the grain. The AE signal peak emerged in the direction approximately 30° for the specimen without holes. In the presence of holes, as the hole diameter increases, the variation trend of AE peak amplitudes within an angular range of -18° to +18° relative to the hole center becomes progressively smoother, with a concurrent reduction in their mean value. This distinct characteristic can serve as a robust indicator for identifying internal hole defects in wood

WOOD RESEARCH Volume 70, Number 1, 2025
JINGGUI WANG, MING LI, SAIYIN FANG, TINGTING DENG, ERZHUANG ZHAI, CHUMIN CHEN, and KEFEI CHEN

RESEARCH ON WOOD DAMAGE FRACTURE CHARACTERISTICS BASED ON ACOUSTIC EMISSION RA-AF VALUE AND ENERGY CONCENTRATION

To study the acoustic emission (AE) characteristics and fracture properties of wood at different stress stages, three-point bending tests and real-time AE monitoring were carried out on Zelkova schneideriana and Pinus sylvestris var. in this paper. Different stress stages were classified according to AE ringing counts-cumulative AE ringing counts-load curves, damage modes of wood at different stages were identified based on distribution characteristics of RA-AF data, and fracture behavior of wood was predicted by energy concentration k. Results show that distribution characteristics of AE RA-AF data can characterize the types of cracks generated in each stress stage of wood. The crack modes generated by both specimens during three-point bending loading are tension shear composite cracks, and the proportion of tensile cracks is significantly higher than that of shear cracks, but during the elastic-plastic stage, Zelkova schneideriana specimens will produce a large number of shear cracks, whereas Pinus sylvestris var. specimens have predominantly tensile cracks, with only a small number of shear cracks produced before and after fracture. The sudden change in the energy concentration k curve between elastic-plastic deformation stage and fracture stage can be used as a precursor of damage for both specimens under three-point bending test conditions