Bulletin of the JSME Journal of Advanced Mechanical Design, Systems, and Manufacturing
Vol.13, No.1, 2019
Effects of rotational velocity and hold time at folding posture on time-dependent release behavior of creased white-coated paperboard
Shigeru NAGASAWA*, Satoshi KANEKO* and Dai ADACHI*
* Department of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka-machi, Nagaoka-shi, Niigata 940-2188, Japan E-mail: snaga@mech.nagaokaut.ac.jp Received: 6 May 2018; Revised: 24 November 2018; Accepted: 17 December 2018
Abstract In this work, a folding experiment was performed to investigate the time-dependent creasing characteristics of white-coated paperboard of 0.3mm thickness. After folding up to the tracking angle of 90° under a specified rotational velocity, the creased part was hold for a chosen short time (0~20s) and the time-dependent release behavior of folding angle was experimentally investigated for the elapsed release time of 10s. When using the paperboard scored with a specified indentation depth, both the hold time of folded posture of creased part and the rotational velocity of fixture were varied. The folding angle of the paperboard was measured by a CCD camera of digital microscope and the bending moment resistance was measured by a load cell of bending test apparatus in the folding experiment. Through the experiment, it was found that the time-dependent release angle consisted of the hold time based intercept part and the creep-recovery based gradient part as a logarithmic function of the elapsed release time. When varying the folding velocity against a fixed unfolding velocity, the unfolded released behavior was isolated by the hold time from the first half folding velocity. Seeing the drop rate of bending moment at the tracking position and the dependency of initial release angle on the rotational velocity, a transient state and quasi-stationary state of bending moment relaxation were revealed.
Keywords
: Folding, Shear, Bending moment, Creasing, Relaxation, Creep, Paperboard
1. Introduction
Coated paperboard is a fundamental raw material for various printed-decorated packaging and transport packaging industries due to its advantages such as high strength-to-weight ratio, high surface smoothness, printability, sustainability, recyclability (Kirwan, 2013). If any cracks occur on the outside of the folded parts of paperboard, which is used for making a cabinet, the mechanical strength of the cabinet is weakened and also the folded parts are inferior in decorative aspects. Actual creasing range was investigated based on the relationship between the crease depth and crease width by Hine (1959). Nagasawa et al. (2003; 2008; 2011) reported about the quasi-static folding stiffness with respect to the indentation depth of the creaser and also discussed about the crease deviation effect on the folding deformation characteristics. Also, several advanced results are reported for the de-lamination mechanism and bulging deformation considering anisotropic material properties (Beex, et al., 2009; Nygards, et al., 2009; Sudo, et al., 2005). However, they were mainly based on the quasi-static solid mechanics. On the other hands, the time-dependent bending moment resistance acting on a hinge which is folded onto a scored line, is important in order to adjust the mechanical conditions of boxing stage performed by an automatic folder gluer. Various time-dependent problems on actual deformation phenomenon have not been sufficiently discussed in the past, although there are several reports of fiber creep and in-plane tensile relaxation of thin paper (Johanson et al., 1964; Sharon, et al., 2010). It is difficult to estimate various time-dependent responses from the quasi-static strength of a creased part, such as the maximum bending moment and the initial gradient of bending moment. Since such the transient deformation of the creased part subjected to a bending moment was not observed by any movie camera or load cells during the dynamic bending test, the time-dependent bending stiffness or its residual strain state could not be verified
Paper No.18-00230
© 2019 The Japan Society of Mechanical Engineers
[DOI: 10.1299/jamdsm.2019jamdsm0004]
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