Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 2: moisture desorption

Holzforschung ◽  
2019 ◽  
Vol 73 (8) ◽  
pp. 737-746 ◽  
Author(s):  
Tianyi Zhan ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Yaoli Zhang ◽  
Jianmin Chang
Keyword(s):  
Shift Factor ◽  
Chinese Fir ◽  
Cunninghamia Lanceolata ◽  
Damping Properties ◽  
Master Curves ◽  
Frequency Dependent ◽  
Wood Stiffness ◽  
Set Up ◽  
Stiffness And Damping ◽  
Moisture Desorption

AbstractThe frequency-dependent viscoelasticity of Chinese fir (Cunninghamia lanceolata) during moisture desorption was investigated and the applicability of the time-moisture superposition (TMS) relation on wood stiffness and damping during the moisture desorption was verified. The hygrothermal conditions for the moisture desorption were set up as six constant temperatures ranging from 30 to 80°C and three relative humidity (RH) levels at 0, 30 and 60%. Due to the elimination of water during the moisture desorption, the stiffness of the Chinese fir increased, whereas the damping decreased. With the increase in frequency, increased stiffness and decreased damping were observed. Utilizing the TMS relation, it was possible to construct master curves of wood stiffness at temperatures ranging from 30 to 80°C. The linear relationship between the shift factor and the moisture content (MC) manifested a low intermolecular cooperativity between the polymers and a narrow relaxation window. However, the TMS relation was not able to predict the wood damping properties during the moisture desorption, because wood is a multi-relaxation system. The non-proportional relationship between the free volume and MC during the moisture desorption may also explain why the TMS relation failed to construct master curves of the wood damping properties.

Influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata). Part 2: moisture desorption

Holzforschung ◽  
2018 ◽  
Vol 72 (7) ◽  
pp. 579-588 ◽  
Author(s):  
Tianyi Zhan ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Yaoli Zhang ◽  
Jianmin Chang
Keyword(s):  
Cell Wall ◽  
Loss Modulus ◽  
Adsorbed Water ◽  
Chinese Fir ◽  
Cunninghamia Lanceolata ◽  
Dynamic Viscoelasticity ◽  
Heating Effects ◽  
Plateau Area ◽  
Set Up ◽  
Moisture Desorption

AbstractThe influence of hygrothermal condition on dynamic viscoelasticity of Chinese fir (Cunninghamia lanceolata) during the moisture desorption (MDes) process was investigated. The ambient hygrothermal environments were set up as a series of constant temperatures and two relative humidity (RH) modes (RHramp-downand RHisohume). The MDesprovided space for the rearrangement of the hydrogen bonds (Re-HB) and caused a mechano-sorptive (MS) effect. The enhancement of the Re-HB effect negatively correlated with the increment of loss modulus, while the elevation of the MS and the heating effects intensified the loss modulus. Lower values of RHc, determining the plateau area of loss modulus, were obtained at higher temperatures or greater RH ramping rates. The residual instability in the wood cell wall was quantitatively characterized by the extent of the MS effect. Residual instability was inversely proportional to the RHisohumelevel during the MDesprocess. The study of time dependent viscoelastic properties under moisture changing process provided insight into the condition of adsorbed water in the cell wall and optimized the manufacturing technique involved in the thermo-hygro-mechanical treatment of wood.

Identification of Nonlinear Property of Honeycomb Paperboard through Use of Hilbert Transform

2012 ◽  
Vol 590 ◽  
pp. 536-539
Author(s):  
Xiao Qin Wei ◽  
Da Peng Zhu
Keyword(s):  
Hilbert Transform ◽  
Nonlinear Property ◽  
Motion Equation ◽  
Damping Properties ◽  
Experiment Data ◽  
Free Response ◽  
Experiment System ◽  
Set Up ◽  
Stiffness And Damping

A method is formulated to model the properties of honeycomb paperboard based on Hilbert transform, In this method, there are no assumptions on the forms of the stiffness and damping properties, this method is truly nonparametric. An experiment system is set up to record the free response of the mass loaded honeycomb paperboard system, the experiment data are used to identify the stiffness and damping properties of honeycomb paperboard. The motion equation of mass loaded honeycomb paperboard system is formulated, the transmissibility curve is simulated, the comparison of the simulated curves and the experiment data indicates the model in this paper is accurate.

Dynamic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) during moisture desorption processes

Holzforschung ◽  
2016 ◽  
Vol 70 (6) ◽  
pp. 547-555 ◽  
Author(s):  
Tianyi Zhan ◽  
Jiali Jiang ◽  
Hui Peng ◽  
Jianxiong Lu
Keyword(s):  
Cell Wall ◽  
Viscoelastic Properties ◽  
Loss Factor ◽  
Loss Modulus ◽  
Polymer Networks ◽  
Chinese Fir ◽  
Cunninghamia Lanceolata ◽  
Unstable State ◽  
Factor Ratios ◽  
Moisture Desorption

Abstract The viscoelasticity of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) during moisture desorption processes were examined at 30°C and two relative humidity (RH) modes: RHramp-down mode from 85 to 0% RH, and RHisohume mode at 0, 30, and 60% RH, respectively. Dynamic viscoelastic properties were determined in a multi-frequency range of 1, 2, 5, 10, and 20 Hz. In both RH modes, desorption of water resulted in increasing stiffness and decreasing damping. The reduction in moisture content caused an unstable state in the cell wall due to the formation of free volumes in cell wall and rearrangement of hydrogen bonds within the polymer networks. Higher ramping rates resulted in greater destabilization, and the unstable state was more pronounced at a lower frequency. The ratio of storage modulus at 1 and 20 Hz remained unchanged during both RH modes. The ratios of loss modulus and loss factor at 1 and 20 Hz increased during the RHramp-down and decreased during the RHisohume period. The changes of loss modulus or loss factor ratios at two frequencies were suitable for evaluation of the unstable state. The instability was aggravated with reducing RH and slightly recovered at constant RH.

scholarly journals Frequency-dependent viscoelastic properties of Chinese fir (Cunninghamia lanceolata) under hygrothermal conditions. Part 1: moisture adsorption

Holzforschung ◽  
2019 ◽  
Vol 73 (8) ◽  
pp. 727-736 ◽  
Author(s):  
Tianyi Zhan ◽  
Jiali Jiang ◽  
Jianxiong Lu ◽  
Yaoli Zhang ◽  
Jianmin Chang
Keyword(s):  
Adsorption Process ◽  
Moisture Adsorption ◽  
Frequency Dependent ◽  
Wood Stiffness ◽  
Testing Frequency ◽  
Adsorption Processes ◽  
Proportional Relationship ◽  
Wlf Model ◽  
Moisture Conditions ◽  
Stiffness And Damping

AbstractTo elucidate the frequency-dependent viscoelasticity of wood under a moisture non-equilibrium state, changes in stiffness and damping as a function of frequency were investigated during the moisture adsorption process. The moisture adsorption processes were carried out at six temperatures (30–80°C) and three relative humidity levels (30, 60 and 90% RH). During the moisture adsorption process, the wood stiffness decreased, and damping increased with the increment of moisture content (MC). Regardless of the moisture adsorption time, the wood stiffness increased, and damping decreased with the increasing testing frequency. Based on the re-organized Williams-Landel-Ferry (WLF) model, the time-moisture superposition (TMS) relation was assumed to be applicable for developing a master curve of wood stiffness during the moisture adsorption process. The frequency ranges of the stiffness master curves spanned from 16 to 23 orders of magnitude at temperatures ranging from 30 to 80°C. However, the TMS relation was not able to predict the wood damping properties during the moisture adsorption process due to the multi-relaxation system of the wood and the non-proportional relationship between free volume and MC at transient moisture conditions.

scholarly journals Frequency-dependent orthotropic damping properties of Nomex honeycomb composites

2021 ◽  
Vol 160 ◽  
pp. 107372
Author(s):  
Yong Zhou ◽  
Anna Liu ◽  
Yongzheng Xu ◽  
Yunli Guo ◽  
Xiaosu Yi ◽  
...  
Keyword(s):  
Damping Properties ◽  
Frequency Dependent ◽  
Nomex Honeycomb

Age-dependent microRNAs in regulation of vascular cambium activity in Chinese fir (Cunninghamia lanceolata)

Trees ◽  
2021 ◽  
Author(s):  
Guijun Liu ◽  
Xian Xue ◽  
Jinling Feng ◽  
Dechang Cao ◽  
Jinxing Lin ◽  
...  
Keyword(s):  
Chinese Fir ◽  
Cunninghamia Lanceolata ◽  
Vascular Cambium ◽  
Age Dependent ◽  
Cambium Activity

Dynamic characteristics of squeeze-type mount using magnetorheological fluid

2005 ◽  
Vol 219 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Y K Ahn ◽  
J-Y Ha ◽  
Y-H Kim ◽  
B-S Yang ◽  
M Ahmadian ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Analysis ◽  
Vibration Isolation ◽  
Dynamic Behaviour ◽  
Electrical Current ◽  
Magnetorheological Fluid ◽  
Test Set ◽  
Mr Fluid ◽  
Set Up ◽  
Stiffness And Damping

This paper presents an analytical and experimental analysis of the characteristics of a squeeze-type magnetorheological (MR) mount which can be used for various vibration isolation areas. The concept of the squeeze-type mount and details of the design of a squeeze-type MR mount are discussed. These are followed by a detailed description of the test set-up for evaluating the dynamic behaviour of the mount. A series of tests was conducted on the prototype mount built for this study, in order to characterize the changes occurring as a result of changing electrical current to the mount. The results of this study show that increasing electrical current to the mount, which increases the yield stress of the MR fluid, will result in an increase in both stiffness and damping of the mount. The results also show that the mount hysteresis increases with increase in current to the MR fluid, causing changes in stiffness and damping at different input frequencies.

Genetic parameters and genotype–environment interactions of Chinese fir (Cunninghamia lanceolata) in Fujian Province

2014 ◽  
Vol 44 (6) ◽  
pp. 582-592 ◽  
Author(s):  
Liming Bian ◽  
Jisen Shi ◽  
Renhua Zheng ◽  
Jinhui Chen ◽  
Harry X. Wu
Keyword(s):  
Genetic Parameters ◽  
Breeding Strategy ◽  
Chinese Fir ◽  
Breeding Program ◽  
Cunninghamia Lanceolata ◽  
Environment Interaction ◽  
Fujian Province ◽  
The Third ◽  
Genotype Environment Interaction ◽  
Sib Families

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is the most commercially important conifer in China, and the Nanjing Forestry University – Fujian Province Chinese fir Cooperation (NJFU – Fujian Cooperation) breeding program has advanced it into the third cycle of selection and breeding. In this paper, we estimated genetic parameters from four sites for 80 half-sib families and summarized previous estimates of genetic parameters in Chinese fir with an objective to propose optimal breeding strategy. Heritability averaged 0.20 and 0.14 for height and diameter at breast height (DBH), respectively, for the four sites. A significant genotype–environment interaction (G × E) for growth was also observed among the four sites, with the greatest interactions between a marginal site and the three central sites in the Fujian Province Chinese fir plantation region. The average estimated type-B genetic correlation between the marginal site and the three central sites was 0.08 for height and –0.09 for DBH. However, the highly productive families were among the most stable across the four sites. The results from this study in combination with summarized genetic parameters from literature were used to discuss and propose an optimal breeding strategy for the third generation of the breeding program for Chinese firs in Fujian Province.

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