Experimental Evaluation of Strength of End Joints with Rectangular Pressed Fingers

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Experimental Evaluation of Strength of End Joints with Rectangular Pressed Fingers

Journal Title: Lesnoy Zhurnal (Russian Forestry Journal) - Year 2020, Vol 15, Issue 3

Abstract

End jointing of wooden blanks is widely distributed in the manufacture of wood products. The most commonly used splicing technology on finger joints with pointy fingers has a number of drawbacks, including the presence of waste and an expensive cutting tool. We proposed an alternative type of end jointing with multiple rectangular tenons made by pressing. Commercialization of the new splicing method requires confirmation of its high quality. The main quality indicator of adhesive joint is its strength. The aim of the study is an experimental evaluation of the bending strength and tensile strength of end joints with rectangular pressed fingers (case study of pine wood blanks). The joints of two types: A and B, with a pitch of 4.2 and 8.2 mm and depth of mortises of 10 and 20 mm, respectively, were studied. The strength of the samples was determined taking into account the requirements of the Russian State Standards GOST 15613.4 and GOST 15613.5. In order to evaluate the quality of joints, we used the indicator “relative strength”; it is the ratio of the joint strength to the solid wood strength. Statistical processing was carried out both by data groups, and for each size and each test type separately. This allowed us to establish the average values of strength for each individual group of samples, as well as to obtain a statistically valid joint evaluation of some indicators. Joints of type A with small fingers showed better results in tensile strength (59.5 %) compared to joints of type B (53.2 %). No statistically significant effect of the joint type was revealed, when processing the results of bending tests in the studied range. Therefore, the average bending strength (80.2 %) characterizes both types of joints. Moreover, the strength of these two types of joints with sufficient reliability can be characterized by the average tensile strength (56.4 %). At the same time, both types of joints correspond in strength to the standard requirements to the products with adhesive end joints. The test results vary in a relatively narrow range, which indicates a stable quality of adhesive joints with rectangular fingers made by pressing. This study demonstrates the possibility of using rectangular pressed fingers for the manufacture of joints based on them.

Authors and Affiliations

О. A. Rubleva, A. G. Gorokhovsky

Keywords

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EP ID EP683377
DOI 10.37482/0536-1036-2020-3-128-142
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