Ancient architectural wood components were evaluated in terms of mechanical properties, material color expression, ultrasonic shape, chemical components, and deformation of shape and position by comparing them with new red pine materials. The results showed that the deterioration of the surface material properties of wood components was very serious, mainly caused by weathering. The attenuation degree of the inner layer of the wood component was relatively low, and the color change of the wood was obvious, which was mainly caused by fungi. Ultrasonic nondestructive testing technology was used to detect the internal damage of ancient wood components. According to the test results, it was speculated that the root defects of pillar components were serious. Three components of wood after long-term weathering changed significantly, and lignin had been seriously damaged. This damage was reflected in the degradation of the number of aromatic groups and the changes in the nature of the group. The main wood beams in the main halls of the three yards were bent at 0 mm offset scale and unit offsets of the pillars of the four courtyards were within the safe range.

No abstract

Polyethylene wax (PEW) has emerged as a commonly used material for maintaining the quality of wood. The emulsification of solid PEW before being injected into wood can effectively overcome the shortcomings of the high-temperature melting and injection process of solid PEW. The PEW emulsion permeability of Eucalyptus (Eucalyptus saligna) and Mongolian Scotch pine (Pinus sylvestris var. Mongolica) in vacuum environment was investigated using impregnation tests. Steaming pretreatment and microwave irradiation pretreatment were applied. The small particle size and low viscosity of the PEW emulsion facilitated its penetration into the wood capillary system. The weight percent gain (WPG) of Eucalyptus and Mongolian Scotch pine post impregnation in vacuum was positively correlated with both the vacuum-holding time and the impregnation temperature, but after 60 min of impregnation the WPG of both wood species decreased significantly. Both pretreatment methods could substantially improve the wood permeability and effectively promote the penetration of the PEW emulsion into the wood. For steaming, Eucalyptus steamed for 80 min and Mongolian Scotch pine steamed for 120 min gained the maximum WPG. For microwave irradiation, both species exhibited the highest WPG after water immersion for 60 min and microwave irradiation for 30 s. There was a significant variation in WPG between the two species with the same pretreatment method. The relatively lower density and better-developed capillary system of Mongolian Scotch pine allowed more efficient penetration of PEW emulsion. It is recommended that, considering the time cost and practical enhancement, microwave irradiation should be given priority to when pretreating wood.

Wood is a non-homogeneous and orthotropic natural polymer material. It is important to test the wood shear modulus and elastic constants accurately and reliably using dynamic methods. Based on the introduction of the advantages of six common methods for dynamic testing of wood shear modulus, such as free plate torsional mode method, free bar torsional vibration method, and Timoshenko beam iterative method, issues associated with the applicability and accuracy of these methods are also pointed out. Recent methods, such as the free square plate torsional mode method and the square plate static torsional strain method, that were developed to dynamically test the shear modulus of wood and wood composite materials, are presented as effective ways to tackle these issues. These new approaches are expected to provide beneficial technical support for using small specimens, overcoming the size effect of specimens, simplifying the testing procedures, improving the test accuracy, and expanding the application range in the dynamic testing of wood shear modulus. These approaches have practical significance in promoting the industrialization and development of structural engineering, furniture and interior decoration, transportation, military, and musical instrument industries.

No abstract