Reduction of Residual Stresses in Medium Density Fibreboard. Part 1. Taguchi Analysis

Summary This paper demonstrates how the Taguchi method of experimental design can be utilised to investigate methods for relieving the residual stresses present in medium density fibreboard (MDF). Panels have been subjected to heat, moisture and pressure, and after equilibration to room conditions, the changes in residual stresses through various layers have been measured using the dissection method. The application of heat and/or moisture has reduced the magnitude of residual stresses while generally the application of pressure has no effect on these stresses. The subsequent paper in this series uses Taguchi analysis to investigate how other board properties such as thickness swell, internal bond strength, surface layer tensile modulus and surface layer tensile strength are affected by the different treatment methods.

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Reduction of Residual Stresses in Medium Density Fibreboard. Part 2. Effects on Thickness Swell and Other Properties

Holzforschung ◽

10.1515/hf.2001.012 ◽

2001 ◽

Vol 55 (1) ◽

pp. 73-81

Author(s):

J. van Houts ◽

D. Bhattacharyya ◽

K. Jayaraman

Keyword(s):

Residual Stress ◽

Tensile Strength ◽

Surface Layer ◽

Residual Stresses ◽

Internal Bond ◽

Tensile Modulus ◽

Thickness Swell ◽

Medium Density ◽

Medium Density Fibreboard ◽

Taguchi Analysis

Summary The Taguchi method of experimental design has been utilised to investigate various treatments for relieving the residual stresses present in medium density fibreboard (MDF). These treatments involved subjecting panels to different combinations of heat, moisture and pressure. This paper reports on the Taguchi analysis of the internal bond strength, surface layer tensile modulus, surface layer tensile strength and thickness swell of the treated specimens. These properties were measured to indicate whether the treatments had any effect on panel strength and dimensional stability. A strong correlation between residual stresses and thickness swell has been identified. When the change in residual stress through the outer layers of a panel is almost completely removed, a reduction in thickness swell of approximately 20% for a 24 hour water soak is observed.

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Some advantages of three-layer medium-density fibreboard as compared to the traditional single-layer one

Journal of Wood Science ◽

10.1186/s10086-019-1822-4 ◽

2019 ◽

Vol 65 (1) ◽

Cited By ~ 1

Author(s):

Turgay Akbulut ◽

Nadir Ayrilmis

Keyword(s):

Bond Strength ◽

Internal Bond ◽

Single Layer ◽

Middle Layer ◽

Resin Content ◽

Internal Bond Strength ◽

Medium Density ◽

Medium Density Fibreboard ◽

Uf Resin ◽

Layer Medium

Abstract The aim of the study was to develop three-layer medium-density fibreboard (MDF) manufacture by adding the coarse fibres in the middle layer, like three-layer particleboard. The liquid urea–formaldehyde (UF) resin was reduced from 10.5 to 6.5 wt% in the middle layer of the MDFs. The UF resin content was kept constant at 10 wt% in the surface layers of all the MDFs. Moreover, the average density of MDFs was decreased from 730 to 650 kg/m3. The internal bond strength of three-layer MDFs decreased with decreasing UF resin content (10.5 to 8.5 wt%) in the middle layer. However, the decreases in the internal bond strength were statistically not significant. The internal bond strength values of the MDFs having density between 730 and 675 kg/m3 did not show significant differences. The cost savings of the resin were 20% when the amount of resin was reduced from 10.5 to 8.5 wt%. Three-layer MDFs had lower resin consumption at lower densities over traditional single-layer MDFs produced in the same plant with the same material components without decreasing their technological properties. In conclusion, it can be said that three-layer MDF could be produced at a lower cost than traditional single-layer MDF.

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Determination of Residual Stresses in Medium Density Fibreboard

Holzforschung ◽

10.1515/hf.2000.030 ◽

2000 ◽

Vol 54 (2) ◽

pp. 176-182 ◽

Cited By ~ 5

Author(s):

Jeroen van Houts ◽

Debes Bhattacharyya ◽

Krishnan Jayaraman

Keyword(s):

Residual Stress ◽

Residual Stresses ◽

Thickness Swell ◽

Hole Drilling ◽

Medium Density ◽

Stress Distributions ◽

Moisture Expansion ◽

Hole Drilling Method ◽

Drilling Method ◽

Residual Internal Stress

Summary Due to the moisture and temperature gradients developed during hot pressing of medium density fibre-board (MDF), residual stresses occur within the board as it equilibrates to room conditions. It would be extremely useful to measure these residual stresses and to determine their effects on board properties such as moduli of elasticity and rupture in bending, internal bond strength and dimensional stability. In this article two methods, namely dissection and hole drilling, have been adapted to measure residual internal stress distributions in six different samples of industry produced MDF. The dissection method involves cutting several pieces of MDF perpendicular to the thickness direction at different depths. The residual stresses released by the dissection can be determined by measuring the curvatures of cut pieces and knowing their elastic moduli. The hole drilling method, on the other hand, involves mounting three strain gauges on the surface of a piece of MDF and drilling a hole to release residual stresses in close proximity. The released stresses are manifested as strains in the forms of which can be measured in three directions on the surface of the board. A theoretical model for predicting residual stresses involving various parameters has been developed and an excellent agreement with the experimental results from both the dissection and hole drilling methods has been achieved. Linear moisture expansion coefficient appears to have the greatest influence on residual stress. When compared against each other, the residual stresses measured by the hole drilling method show some shortcomings towards the centre of the board. While all six of the MDF boards exhibited similar trends in their residual stress distributions, significant differences were identified in the magnitudes of residual stress measured. Finally, some preliminary results linking the residual stress with the thickness swell of the samples and their surface densities have been presented.

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Reduction of Residual Stresses in Medium Density Fibreboard

Holzforschung ◽

10.1515/hfsg.2001.67 ◽

2001 ◽

Vol 55 (1) ◽

pp. 67-72 ◽

Cited By ~ 3

Author(s):

Jeroen van Houts ◽

Debes Bhattacharyya ◽

Krishnan Jayaraman

Keyword(s):

Residual Stresses ◽

Medium Density ◽

Medium Density Fibreboard

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Reduction of Residual Stresses in Medium Density Fibreboard

Holzforschung ◽

10.1515/hfsg.2001.73 ◽

2001 ◽

Vol 55 (1) ◽

pp. 73-81 ◽

Cited By ~ 3

Author(s):

Jeroen van Houts ◽

Debes Bhattacharyya ◽

Krishnan Jayaraman

Keyword(s):

Residual Stresses ◽

Medium Density ◽

Medium Density Fibreboard

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Improving water resistance of wheat straw-based medium density fiberboards bonded with aminoplastic and phenolic resins

BioResources ◽

10.15376/biores.2.2.148-156 ◽

2007 ◽

Vol 2 (2) ◽

pp. 148-156 ◽

Cited By ~ 5

Author(s):

Thomas Hervillard ◽

Qi Cao ◽

Marie-Pierre G. Laborie

Keyword(s):

Bond Strength ◽

Wheat Straw ◽

Internal Bond ◽

Water Resistance ◽

Cost Effective ◽

Thickness Swell ◽

Flexural Properties ◽

Medium Density ◽

Phenolic Resins ◽

Wax Content

A long standing problem in the manufacture of wheat-straw based composites with cost-effective formaldehyde-based resins is their poor water resistance as demonstrated by their large water thickness swell. In this study, wheat straw based medium density fiberboards were manufactured using 3 resin/wax systems: a melamine-urea-formalde-hyde resin with either low or high wax content, and a phenol-formal-dehyde resin with low wax content. The flexural properties, internal bond strength, and thickness swell of the resulting composites were evaluated and compared according to ASTM methods. The three MDF compos-ites passed the requirements for MDF in interior application, except for the MDF manufactured with the aminoplastic resin and low wax content that failed to provide acceptable thickness swell. Using the phenolic resin in combination with low wax content resulted in a higher grade MDF composite, grade 120, than with the aminoplastic and high wax content. This study demonstrates that wheat straw based MDF manu-factured with cost-effective aminoplastic and phenolic resins can have flexural properties, internal bond strength and thickness swell perfor-mance above the requirements from the American National Standards Institute.

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Effect of diamond burnishing parameters on the state of the processed surface layer of billets made of high-strength "30ХГСН2А-ВД" steel

10.36652/0042-4633-2020-5-82-86 ◽

2020 ◽

pp. 82-86

Author(s):

A.N. Shvetsov ◽

D.L. Skuratov

Keyword(s):

Surface Layer ◽

Residual Stresses ◽

Strain Hardening ◽

Processing Speed ◽

Synthetic Diamond ◽

High Strength ◽

The State ◽

Diamond Burnishing

The influence of the burnishing force, tool radius, processing speed and feed on the distribution of circumferential and axial residual strses, microhardness and the depth of strain hardening in the surface layer when pr ssing of "30ХГСН2А-ВД" steel with synthetic diamond "ACB-1" is considered. Empirical dependencies determining these parameters are given. Keywords diamond burnishing, strain hardening depth, circumferential residual stresses, axial residual stresses, microhardness. [email protected], [email protected]

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Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

Journal of Manufacturing and Materials Processing ◽

10.3390/jmmp5020055 ◽

2021 ◽

Vol 5 (2) ◽

pp. 55

Author(s):

Robert Zmich ◽

Daniel Meyer

Keyword(s):

Surface Layer ◽

Residual Stresses ◽

Thermal Loads ◽

Deep Rolling ◽

Mechanical Loads ◽

Thermomechanical Process ◽

Compressive Stresses ◽

New Process ◽

Negative Effect ◽

Compressive Residual Stresses

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

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