This work optimizes the parameters of ultrahigh-pressure water jet, with or without abrasives, for the cutting of Pterocarpus macarocarpus Kurz wood, a precious species. Parametric factors of cutting pressure, target distance and feed rate were analyzed with respect to the resultant surface roughness of the cuts on specimens using an orthogonal experiment. The optimal machining schemes were elected for water jets either with or without added abrasives based on microscopic evidences. The results showed that the impacts on the resultant surface-roughness of the factors with a given water jet, i.e. either with or without added abrasives, from the most to the least, are both in the order of water jet pressure>feed rate>target distance. Water jets with no added abrasives have lower cutting capacity, which was evidenced by the worse surface roughness of cuts resulted from rebound jet. Raising their kinetic energy, the probabilities of fracture from tearing would also rise, thus, inducing corrugation in the bottom with exacerbated overall surface roughness of cuts. Abrasive water jet has the feature of many ripples, decreasing the surface integrity of specimens. Therefore, to improve product quality of Pterocarpusma carocarpus Kurz wood, is to increase the portion that is smooth in the sections from water jet cuts by choosing carefully the process parameters. The investigation of water jet cutting in this work throws some light on the configuration of process parameters while applying ultra high-pressure water jets, both with and without added abrasives, to the cutting of wood products of precious species.
In this paper, the three-layer Canadian hemlock CLT panel was designed to test the elastic modulus and bending strength of CLT specimens by four-point bending method. The interlaminar shear of CLT specimens was tested by short-span three-point bending method. Strength, the shear strength and wood breaking rate of the CLT specimens were tested by the stair shear method. At the same time, the failure mode of the CLT board was analyzed. The main conclusions indicate that the test values of bending and shear performance of Hemlock CLT can meet the relevant grade requirements of standard ANSI APA PRG320: 2012. During the bending process, the CLT specimen firstly exhibits a rolling shear failure of vertical layer after reaching the non-elastic deformation phase. After that, the damage extends gradually to the interface layer. The final failure mode is shear failure of interface layer or tensile failure of parallel layer. The interlaminar shear performance is partly relevant to the converted timber performance of parallel layer of CLT under the short-span three-point bending test conditions. The position of interlaminar shear failures is concentrated near support points of specimens and the position is generally located at the interface between parallel and vertical layers, inclining to the parallel ones. CLT at Grade 1 has significantly higher interlaminar shear strength than CLT at Grade 2. There is a certain variability in the test results of wood failure rate of CLT. The overall mechanical properties of the hemlock specification material and the hemlock CLT can meet the relevant grade requirements of Standard ANSI APA PRG320: 2012. The above can provide reference for the optimization design and application work of CLT heavy-duty timber structure.