Study on torque and clamping forces of screw‐connected plywood

Cedou Kumpenza,Ulrich Müller,Gerhard‐David Schmidt,Andreas Ringhofer,Adeayo Sotayo

doi:10.1002/eng2.12211

Abstract

AbstractIn various engineering applications, screws are commonly used to connect wood and engineered wood products to each other. To describe the axial loads which may be transmitted with these components, it is important to quantify the resulting clamping forces in relation to the applied screw torques. In this initial study, birch plywood panels with thicknesses of t = 12, 16, and 20 mm connected with screws (major thread diameter d ≈ 5 mm) are experimentally tested to establish screw driving, tightening and stripping torques. In addition to that, the resulting clamping forces that occur over a time period of 120 hours are monitored and analyzed. A good agreement was found between the established time‐dependent clamping force functions compared to the regression model, which are recommended in the literature.

Highlights

At the beginning of the 20th century, wood was frequently used in combination with steel as structural parts of vehicles.[1]
Only a few studies have dealt with the investigation of the long-term clamping forces that appear in the screwed wood members, in direct relation to the applied screw torques
It was assumed that specimens with a thickness of t = 12, 16, and 20 mm should be tightened with screw torques of tightening torques (TT) = 3, 4, and 5 Nm, respectively

Summary

Introduction

At the beginning of the 20th century, wood was frequently used in combination with steel as structural parts of vehicles.[1]. Provide an economical and reliable fastening solution.[5] applying screws as connectors for lightweight materials like solid wood and engineered wood products exhibits challenges that need to be addressed. Only a few studies have dealt with the investigation of the long-term clamping forces that appear in the screwed wood members, in direct relation to the applied screw torques. Kuang et al[22] and Tor et al[23,24] investigated the appearing screw torques in relation to applicable pilot holes and screw penetration depths in engineered wood products. The aim of this research study is to give fundamentals about the time-dependent progression of clamping forces in direct relation to the applied screw torques that can be expected when plywood elements are screwed to each other. It is believed that these data can be considered for the design of screw connections and input data for structural simulations

Methods

Results

Conclusion