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Localized density effects on fastener holding capacities in wood-based panels. Part 2: cyclic tests.

Abstract

To improve our understanding of localized density effects in wood-based panels on the holding capacities of fasteners commonly used in furniture, a comprehensive study was conducted using static and cyclic tests of withdrawal and head pull-through of screws and staples and lateral resistance of screws in oriented strandboard (OSB), medium density fiberboard (MDF), and particleboard. In this paper, results of cyclic tests are presented and comparisons are made with the static test results reported in Part 1. Similarly to static tests, cyclic test data indicated that density variation in OSB panels had a significant effect on screw withdrawal, head pull-through, and lateral resistances, but the effects were less evident with staple withdrawal and head pull-through. For particleboard, density variation had a significant effect on screw and staple face withdrawal and head pull-through resistances, but the effects were less pronounced for screw and staple edge withdrawal and screw lateral resistances. For MDF, no significant correlations were found, which was likely due to the low density variation in these panels. The data from this study will be useful to the panel industry and furniture manufacturers for optimizing use of panel products and fasteners in furniture frames.

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To reduce the cost of framing components, upholstered furniture manufacturers are always interested in alternative materials that are less expensive, but as strong and reliable as the traditionally used materials. With the development of computer numerical control technology, composite panels, such as oriented strandboard (OSB), medium density fiberboard (MDF), and particleboard, potentially can be used as replacements for solid wood in upholstered furniture frames. But, the suitability and performance of traditional fasteners used in panel products for such applications has not been well studied. One of the concerns is density variation and non-uniformity across the thickness and in the plane of the panel, and how it could affect the holding capacity of fasteners. Available reference values are based on static tests; only limited information is found about the density effects on fastener holding capacities in wood-based panels under cyclic loading conditions.

In-service upholstered furniture frames are subjected to a wide range of loads, which act as repetitive events of loading and unloading. Typically, in the furniture industry, long-term fatigue loading is studied using a large number of non-reversed loading cycles (25,000 cycles on each load level depending on the performance acceptance level) with an average rate of 20 cycles per minute (GSA 1998). This performance test regime is based on a zero-to-maximum (one-sided or non-reversed) cyclic stepped fatigue load method rather than a static or constant amplitude cycling load method (Eckelman 1988). For example, Zhang et al. (2006) studied bending fatigue life of metal-plate-connected (MPC) joints in furniture-grade pine plywood by subjecting the joints to one-sided stepped cyclic bending loads.

Several studies were conducted on the performance of wood or wood-based material assemblies under cyclic or fatigue tests using different test protocols. For example, reversed and non-reversed cyclic loading (Hayashi et al. 1980) were used to evaluate the fatigue properties of wood butt joints with metal-plate connectors in timber. De Melo Mouria et al. (1995) used a non-reversed cyclic load schedule (varying tension) followed by a sinusoidal function to examine the influence of wood density on the mechanical behavior of MPC joints.

This study is part of a broader research program to examine the localized density effects on fastener holding capacities in wood-based panels. This paper presents cyclic test data and complements the static test results reported by Wang et al. (2007). The key objective of this study was to evaluate the holding capacity of screws and staples in commercial wood-based panels under cyclic loading in comparison with static loading. This paper also discusses the correlation between fastener holding capacity and density distribution in panels. Technical information generated in this study will be used to provide recommendations to the panel industry on the use of fasteners in their products and how to optimize the construction of furniture frames.

Materials and methods

The specimens for cyclic tests were prepared using the same materials and mapping and cutting techniques as described in the previous paper (Wang et al. 2007). The following panels were used in the study:

1. MDF: 16 mm thick, grade 150,

2. Particleboard: 16 mm thick, grades M2 and MS (two of each),

3. OSB: 11 mm (7/16 in.) thick,

4. OSB: 15 mm (19/32 in.) thick, and

5. OSB: 18 mm (23/32 in.) thick.

The OSB panels were made of aspen and were grade O2. In each of these five categories, four full-sized (1.22 by 2.44 m) panels, marked A, B, C, and D, were chosen for specific tests, so that one half of the specimens were cut for static tests and the other half were cut from the same panel for the matching cyclic tests. Table 1 provides information on the types and number of cyclic tests performed. Each specimen was used for two tests. Fasteners were driven into the specimens following the same techniques as described in Part 1 (Wang et al. 2007).

The tests were conducted in accordance with ASTM D1037 (ASTM 2005a) and ASTM D 1761 (ASTM 2005b) standards with the following modifications. The test set-up used for the screw lateral resistance was modified by adding a screw supporting device on each side, as shown in Figure 1, to allow for cyclic loading without slack. Load rate was adjusted to produce 15 cycles per minute under load-controlled conditions at a uniform rate of loading at every step. Ultimate loads ([P.sub.ult]) determined from static monotonic tests were used to calculate the reference load levels ([P.sub.ref]) needed for cyclic stepped loading (Tables 2 through 5) Cyclic loading was applied in three steps with 30 cycles at each load level: 15 percent, 35 percent, and 70 percent [P.sub.ult], after which the specimens were loaded to failure (Fig. 2). Note that for the staple edge withdrawal tests, load levels in the first step were 30 percent [P.sub.ult] and 25 percent [P.sub.ult] for parallel and perpendicular orientations, respectively (Table 3). A preload of 40 N was applied to eliminate slack in the system during cycling.

The cyclic load regime used in this study is referred to as short-term cyclic to distinguish it from a typical fatigue loading which is usually conducted with a large number of cycles until failure occurs. Due to the amount of time needed to perform a single test following the General Service Administration (GSA 1998) procedure, it was decided to conduct the short-term cyclic test that lasts approximately 6 minutes. This allowed for testing a sufficient number of specimens from various panel types and thicknesses.

An analysis of variance (ANOVA) general linear model procedure was performed on individual fastener holding capacities for all types of panels to examine the correlation between localized density and ultimate holding capacity. In order to classify the holding capacities of the fasteners in the panels, Duncan's multiple tests were performed on the average values.

Results and discussion

An example of typical load-displacement curves of the cyclic and corresponding static tests of screw head pull-through are shown in Figure 3. In this study, ultimate fastener holding capacity has been used as an indicator of connection resistance. Other parameters associated with the load--displacement relationship, however, could be established (e.g., initial stiffness and the slip of the fastener in the panel at a certain load level or at failure). Summarized test results including classified average resistance values for each type of panel are presented in Tables 6 and 7 and Figures 4 through 7. Comparisons between static and cyclic test data are shown in Table 8.

[FIGURE 1 OMITTED]

Withdrawal resistance of screws

Figure 4 shows the average withdrawal resistance of screws for each tested panel. With the exception of the 11-mm and 18-mm OSB panels, face withdrawal resistance was significantly higher than that from the edge. There were no significant differences between the edge withdrawal resistances parallel and perpendicular to the long axis of the panel for all of the panels tested. The average face withdrawal resistance was highest with the 15-mm OSB panel and lowest for the 11-mm OSB panel. MDF panels showed resistances similar to the 15-mm OSB panel. Particleboard panels performed similarly to the 18-mm OSB panels. In edge withdrawal, the 11-mm OSB and 16-mm particleboard panels showed the lowest resistances, which can be explained by the low core density of particleboard and the small thickness of OSB. Also, some specimens were split during the insertion of screws prior to testing. Edge withdrawal resistance in the 15-mm and 18-mm OSB panels were similar to that of the 16-mm MDF panel.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

ANOVA was performed to verify if a relationship exists between screw withdrawal resistance and localized density of the panel. Results indicated that for cyclic face withdrawal in all of the OSB and particleboard panels the relationship was significant at the 95 percent confidence level. The r-values of the linear regression model ranged from 0.47 to 0.83 (Table 6). A poor relationship, however, was observed for MDF panels. This could be attributed to the uniformity in the MDF localized density in comparison to OSB or particleboard panels. For edge withdrawal of screws under cyclic load, the relationship was found to be significant for all of the OSB panel specimens perpendicular to the long axis of the panel, while in the parallel direction, the relationship was only significant in the 11-mm and 18-mm OSB panels (Table 6). Relationships were poor for both MDF and particleboard panels.

As can be seen in Table 8, in general no significant differences were found between static and cyclic screw withdrawal resistances, with the exception of edge withdrawal resistance of screws from OSB which generally appeared somewhat higher than the static on a statistically significant level. Note, however, that the cyclic load regime used in the tests did not produce fatigue damage.

Withdrawal resistance of staples

Figure 5 illustrates that face withdrawal resistance was significantly higher than edge withdrawal for all types of panels. MDF specimens showed the highest resistance in face and edge withdrawal, while 11-mm OSB specimens demonstrated the lowest resistance. Edge withdrawal resistance of 11-mm OSB was less than half that of the other panels which can be explained by the splitting associated with stapling due to the small thickness of the panel. In fact, the split was visible in some specimens before the test. There were no significant differences between edge withdrawal resistances parallel or perpendicular to the long side of the panel for all of the tested materials except the 15-mm OSB and MDF.

When examining interactions between localized density and face withdrawal of the staples under cyclic load, it was found that the relationships were significant for OSB and particleboard panels at a 95 percent confidence level (Table 7). The r-values of the linear regression models ranged from 0.55 to 0.82. For staple edge withdrawal resistance parallel to the long panel axis, the relationships were reasonably significant for OSB panels but not for MDF and particleboard panels. In the perpendicular direction, however, the correlation was significant for the 15-mm and 18-mm OSB and MDF panels only. Particleboard specimens did not exhibit any significant relationship between the two parameters (Table 7).

Comparisons with static loading show that generally lower withdrawal resistances were observed under cyclic loading of OSB panels and not in MDF or particleboard panels (Table 8). Therefore, it could be concluded that staple face and edge withdrawal resistance of OSB is more sensitive to cyclic loading than in the other panel products tested.

Lateral resistance of screws

Data in Figure 6 indicate that the 18-mm OSB and MDF panels demonstrated the highest resistances among the tested panels. Resistances of the 11-mm OSB and particleboard panels were the lowest. With the exception of the 11-mm OSB panels, there were no significant differences between screw lateral resistances in the direction parallel and perpendicular to the long axis of the panels.

Significant linear relationships between localized density and the lateral resistance of screws were found for OSB panels in both loading directions, except for the 18-mm OSB panels with screws loaded perpendicular to the long axis of the panel. But, the relationships were found insignificant for MDF and particleboard panels (Table 6).

As shown in Table 8, cyclic lateral resistances of screws appeared to be lower than those determined from static tests; however, in most cases the differences were not statistically significant. Note again that no fatigue failures of screws were observed.

Screw head pull-through

The average resistance of MDF panels to screw head pull-through was the highest and that of the 11-mm OSB panels was the lowest (Fig. 7). The 15-mm OSB panels exhibited similar resistance to the 18-mm OSB and the 16-mm MDF panels, probably due to the high density and uniform density distribution throughout the thickness of the panels.

Statistical analysis indicated that the relationships between screw head pull-through resistance and localized density for individual OSB and particleboard panels were significant at a 95 percent confidence level, with the r-values of the linear regression models ranging from 0.43 to 0.80 (Table 6). For MDF panels, the correlation could not be proven statistically significant due to the low variation of the horizontal density.

Average cyclic screw head pull-through resistance was higher than static resistance for all of the tested panels (Table 8). One possible explanation is that the cyclic load used in the tests did not produce fatigue damage. Another explanation could be the crushing of cell walls under the screw head due to repeated loading and subsequent densification of the surface layer. In practice, such densification is only possible if the head pull-through resistance of screws does not exceed the withdrawal resistance of the screw shank from the main member. Otherwise, the screw would withdraw completely from the adjacent member before the full head pull-through resistance is developed.

Staple head pull-through

The average resistance to staple head pull-through of the 15-mm OSB panels was the highest and that of the 11-mm OSB panels was the lowest (Fig. 7). The 18-mm OSB panels showed a lower resistance than the 15-mm OSB panels, which was likely due to the lower density of the specimens. The average resistance of MDF panels was in the same order as that of 15-mm OSB panels, which was likely due to the high face and core density of the panels. The relationship between staple head pull-through resistance and localized density was statistically significant for all of the panels except for the MDF (Table 7).

It should be noted that in some tests, at load levels near failure, the gripping device was not able to sustain the locking mechanism of the staple's legs, and one leg slipped off, while the other remained locked. Consequently, the staple was pulled out of the panel by one leg, and the overall failure load was lower than in those cases where slippage did not occur. Slippage was observed more often during cyclic tests.

Comparing the cyclic and static tests it was found that the cyclic resistance was higher than the static resistance for the 15-mm OSB and particleboard specimens. No significant differences were observed for the other panels (Table 8).

Conclusion

Generally, cyclic tests of fastener holding capacities in wood-based panels showed similar results to the corresponding static tests. For the cyclic loading regimes used in this study (90 cycles at different load levels), no significant differences were observed between static and cyclic behavior in terms of ultimate fastener holding capacity with few exceptions. Localized densification of wood fibers could be attributed to increasing fasteners capacities for certain panel and fastener combinations following repeated events of loading and unloading. Lower values of cyclic capacity for other combinations sometimes were associated with the lower specimen density. In order to better understand fatigue response, loading regimes with an increased number of loading cycles are needed. Further analysis of the load-deformation relationships including initial stiffness and deformation at a certain load level can be used to better characterize the cyclic behavior of the fasteners.

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

Results obtained in this study provide useful information for panel producers and furniture manufacturers about the holding capacities of screws and staples in various wood-based panels of various thicknesses. In most cases, increasing panel density would improve fastener holding capacity. Additionally, reducing the variation in localized density by producing panels with more consistent and uniform density distribution for use in the upholstered furniture industry could be more effective and possibly more economical for improving the fastener holding design values of the panels. The edge splitting of 11-mm-thick panels under screws and staples indicates that these fasteners should not be used with thin panels.

Acknowledgments

The authors wish to thank the technicians at the Department of Wood and Forest Sciences at Laval University and at the Building Systems Dept. at FPInnovations-Forintek Division for their technical support. Acknowledgment is also made of the financial support from Natural Resources Canada--Canadian Forest Serv., CIBISA--the Industrial Chair on Engineered Wood Products for Structural and Appearance Applications. Thanks are also extended to Alberta Research Council, University of British Columbia and Structural Board Association for their assistance.

[FIGURE 7 OMITTED]

Literature cited

American Society for Testing and Materials (ASTM). 2005a. Test methods for evaluating properties of wood-base fiber and particle panel materials. D1037-99. Annual Book of ASTM Standards. ASTM, West Conshohocken, PA.

--. 2005b. Test methods for evaluating mechanical fasteners in wood. D1761. Annual Book of ASTM Standards. ASTM, West Conshohocken, PA.

De Melo Mouria, J.D., C. Bastian, G. Duchanois, J.M. Leban, and P. Triboulot. 1995. The influence of wood density on metal-plate connector mechanical behavior under cyclic loading. Forest Prod. J. 45(11/12):74-82.

Eckelman, C.A. 1988. Performance testing of furniture. Part II: A multipurpose universal structural performance test method. Forest Prod. J. 38(4):13-18.

General Service Administration (GSA). 1998. Upholstered furniture test method. FNAE-80-214A. Furniture Commodity Center, Federal Supply Services, Washington, DC.

Hayashi, T., H. Sasaki, and M. Masuda. 1980. Fatigue properties of wood butt joints with metal plate connectors. Forest Prod. J. 30(20):49-54.

Wang, X., A. Salenikovich, and M. Mohammad. 2007. Localized density effects on fastener holding capacities in wood-based panels. Forest Prod. J. 57(1/2):103-109.

Zhang, J., Y. Yu, and F. Quin. 2006. Bending fatigue life of metal-plate-connected joints in furniture-grade pine plywood. Forest Prod. J. 56(11/12):62-66.

Xiaodong Wang *

Alexander Salenikovich *

Mohammad Mohammad

The authors are, respectively, Postdoctoral Assistant/former PhD Candidate and Associate Professor, Dept. of Wood and Forest Sciences, Laval Univ. Quebec City, Quebec, Canada (jerrytommy@yahoo.com, Alexander.Salenikovich@sbf.ulaval.ca); and Research Scientist and Group Leader, FPInnovations--Forintek Division, Ste-Foy, Quebec, Canada (mohammad.mohammad@qc.forintek.ca). This paper was received for publication in May 2007. Article No. 10362.

* Forest Products Society Member.

[c] Forest Products Society 2009.
Table 1.--Types and number of tests performed.

 Fastener type Property

Screw gage 10 Withdrawal Face
 (25 mm long) Edge Parallel to
 long axis
 Perpendicular
 to long axis

Screw gage 10 Lateral Parallel to
 (50 mm long) resistance long axis
 Perpendicular
 to long
 axis
 Head pull-
 through

Staple gauge 16 Withdrawal Face
 (38 mm long, Edge Parallel to
 11 mm crown) long axis
 Perpendicular
 to long axis

 Head pull-
 through

 Number of Number
 specimens Panel of tests
Fastener type per panel replication per panel

Screw gage 10 Withdrawal 10 D 20
 (25 mm long) 10 D 20
 10 D 20

Screw gage 10 Lateral 10 A 20
 (50 mm long) resistance 10 A 20
 Head pull- 10 1/2 of B 20
 through

Staple gauge 16 Withdrawal 10 C 20
 (38 mm long, 10 C 20
 11 mm crown) 10 C 20
 Head pull- 10 1/2 of B 20
 through

Table 2.--Reference load levels for cyclic loading: screw
withdrawal from face and edge (N).

 Face

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 mm 1087 15% 163
 (7/16 in.) 35% 380
 70% 761

OSB 15 mm 1448 15% 217
 (19/32 in.) 35% 507
 70% 1014

OSB 18 mm 1308 15% 196
 (23/32 in.) 35% 458
 70% 915

MDF 1394 15% 209
 (16 mm) 35% 488
 70% 976

Particleboard 1206 15% 181
 (16 mm) 35% 422
 70% 844

 Edge
 (parallel) (a)

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 mm 712 15% 107
 (7/16 in.) 35% 249
 70% 498

OSB 15 mm 953 15% 143
 (19/32 in.) 35% 334
 70% 667

OSB 18 mm 949 15% 142
 (23/32 in.) 35% 332
 70% 665

MDF 1239 15% 186
 (16 mm) 35% 434
 70% 867

Particleboard 808 15% 121
 (16 mm) 35% 283
 70% 566

 Edge
 (perpendicular) (b)

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 mm 801 15% 120
 (7/16 in.) 35% 280
 70% 561

OSB 15 mm 1047 15% 157
 (19/32 in.) 35% 366
 70% 733

OSB 18 mm 880 15% 132
 (23/32 in.) 35% 308
 70% 616

MDF 1191 15% 179
 (16 mm) 35% 417
 70% 834

Particleboard 827 15% 124
 (16 mm) 35% 289
 70% 579

(a) "Parallel" refers to the direction of loading parallel
to the long axis of the panel.

(b) "Perpendicular" refers to perpendicular to the long axis
of the panel.

Table 3.--Reference load levels for cyclic loading: staple
withdrawal from face and edge (N).

 Face

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 nun 482 15% 72
 (7/16 in.) 35% 169
 70% 338

OSB 15 nun 785 15% 118
 (19/32 in.) 35% 275
 70% 550

OSB 18 rum 870 15% 130
 (23/32 in.) 35% 304
 70% 609

MDF 976 15% 146
 (16 nun) 35% 342
 70% 683

Particleboard 644 15% 97
 (16 mm) 35% 225
 70% 451

 Edge
 (parallel) (a)

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 nun 204 30% 61
 (7/16 in.) 35% 71
 70% 142

OSB 15 nun 479 15% 72
 (19/32 in.) 35% 168
 70% 336

OSB 18 rum 565 15% 85
 (23/32 in.) 35% 198
 70% 395

MDF 628 15% 94
 (16 nun) 35% 220
 70% 440

Particleboard 517 15% 78
 (16 mm) 35% 181
 70% 362

 Edge
 (perpendicular) (b)

 Panel type [P.sub.ult] [P.sub.ref]

OSB 11 nun 277 25% 69
 (7/16 in.) 35% 97
 70% 194

OSB 15 nun 548 15% 82
 (19/32 in.) 35% 192
 70% 384

OSB 18 rum 551 15% 83
 (23/32 in.) 35% 193
 70% 386

MDF 612 15% 92
 (16 nun) 35% 214
 70% 428

Particleboard 492 15% 74
 (16 mm) 35% 172
 70% 344

(a) "Parallel" refers to the direction of loading parallel
to the long axis of the panel.

(b) "Perpendicular" refers to perpendicular to the long axis
of the panel.

Table 4.--Reference load levels for cyclic loading: screw
lateral resistance (N).

 Parallel (a)

Panel type [P.sub.ult] [P.sub.ref]

OSB l1 mm (7/16 in.) 1122 15% 168
 35% 393
 70% 786

OSB 15 mm (19/32 in.) 1842 15% 276
 35% 645
 70% 1289

OSB 18 mm (23/32 in.) 2201 15% 330
 35% 770
 70% 1540

MDF (16 mm) 2265 15% 340
 35% 793
 70% 1586

Particleboard (16 mm) 1148 15% 172
 35% 402
 70% 804

 Perpendicular (b)

Panel type [P.sub.ult] [P.sub.ref]

OSB l1 mm (7/16 in.) 1127 15% 169
 35% 394
 70% 789

OSB 15 mm (19/32 in.) 2008 15% 301
 35% 703
 70% 1405

OSB 18 mm (23/32 in.) 2505 15% 376
 35% 877
 70% 1755

MDF (16 mm) 2247 15% 337
 35% 786
 70% 1573

Particleboard (16 mm) 1119 15% 168
 35% 392
 70% 783

(a) Parallel refers to the direction of loading parallel
to the long axis of the panel.

(b) "Perpendicular" refers to perpendicular to the long axis
of the panel. Comparisons between static and cyclic test data
are shown in Table 8.

Table 5.--Reference load levels for cyclic loading:
screw and staple head pull-through (N).

 Screw

Panel type [P.sub.ult] [P.sub.ref]

OSB 11 mm (7/16 in.) 1491 15% 224
 35% 522
 70% 1044

OSB 15 mm (19/32 in.) 2677 15% 402
 35% 937
 70% 1874

OSB 18 mm (23/32 in.) 2460 15% 369
 35% 861
 70% 1722

MDF (16 mm) 2694 15% 404
 35% 943
 70% 1886

Particleboard (16 mm) 1587 15% 238
 35% 555
 70% 1111

 Staple

Panel type [P.sub.ult] [P.sub.ref]

OSB 11 mm (7/16 in.) 882 15% 132
 35% 309
 70% 617

OSB 15 mm (19/32 in.) 1148 15% 172
 35% 402
 70% 804

OSB 18 mm (23/32 in.) 1071 15% 161
 35% 375
 70% 750

MDF (16 mm) 1369 15% 205
 35% 479
 70% 958

Particleboard (16 mm) 842 15% 126
 35% 295
 70% 589

Table 6.--Test results for screws under cyclic load.

 Average
 Nominal density
 Property Panel thickness (x)

 (mm) (kg/
 [m.sup.3])

Screw gage 10, 25 mm long
 Face OSB 11 586
 withdrawal 15 616
 18 585
 MDF 16 788
 Particleboard 16 688

 Edge Parallel to OSB 11 568
 withdrawal long axis 15 665
 18 596
 MDF 16 782
 Particleboard 16 703
 Perpendicular OSB 11 554
 to long 15 676
 axis 18 593
 MDF 16 791
 Particleboard 16 683

Screw gage 10, 50 mm long
 Lateral Parallel to OSB 11 568
 resistance long axis 15 655
 18 615
 MDF 16 784
 Particleboard 16 688
 Perpendicular OSB 11 583
 to long 15 645
 axis 18 562
 MDF 16 793
 Particleboard 16 675

 Head pull- OSB 11 613
 through 15 675
 18 582
 MDF 16 779
 Particleboard 16 685

 Average holding
 capacity
 Property (observed y)

 (N)

Screw gage 10, 25 mm long
 Face 898 (37.4) (c) C (d)
 withdrawal 1448 (20.2) A
 1210 (25.8) B
 1394 (7.4) A
 1183 (9.5) B

 Edge Parallel to 813 (23.8) B
 withdrawal long axis 1137 (16.4) A
 1153 (23.0) A
 1194 (11.5) A
 833 (10.8) B
 Perpendicular 872 (18.2) B
 to long 1121 (18.8) A
 axis 1173 (25.7) A
 1206 (9.3) A
 810 (12.5) B

Screw gage 10, 50 mm long
 Lateral Parallel to 953 (35.5) C
 resistance long axis 1829 (27.0) B
 2162 (26.2) A
 2114 (9.6) A
 1037 (17.8) C
 Perpendicular 1225 (22.4) B
 to long 1971 (25.9) A
 axis 2026 (24.0) A
 2162 (15.4) A
 966 (14.8) C

 Head pull- 1764 (25.7) B
 through 2918 (14.6) A
 2904 (23.4) A
 3008 (3.7) A
 1921 (8.3) B

 Regression equation
 Property (predicted y)

Screw gage 10, 25 mm long
 Face y = 2.58x - 613
 withdrawal y = 2.00x + 218
 y = 1.76x + 179
 y = -0.27x + 1609
 y = 2.66x - 651

 Edge Parallel to y = 1.28x + 88.5
 withdrawal long axis y = 0.12x + 1056
 y = 3.08x - 682
 y = 1.54x - 10.9
 y = 1.58x - 277
 Perpendicular y = 1.18x + 218
 to long y = 2.01x - 238
 axis y = 2.91x - 553
 y = 0.67x + 673
 y = 0.29x + 615

Screw gage 10, 50 mm long
 Lateral Parallel to y = 3.17x - 845
 resistance long axis y = 4.00x - 788
 y = 6.99x - 2136
 y = 0.89x + 1413
 y = -0.56x + 1426
 Perpendicular y = 2.35x - 147
 to long y = 4.31x - 807
 axis y = 3.29x + 178
 y = 4.23x - 1192
 y = 1.61x - 123

 Head pull- y = 3.13x - 156
 through y = 2.42x + 1283
 y = 6.61x - 941
 y = 1.80x + 1603
 y = 3.71x - 616

 Property r RMSE (b)

Screw gage 10, 25 mm long
 Face 0.83 (a) 182
 withdrawal 0.53 (a) 243
 0.47 (a) 271
 0.06 101
 0.59 (a) 89.1

 Edge Parallel to 0.51 (a) 162
 withdrawal long axis 0.04 182
 0.76 (a) 167
 0.24 132
 0.42 79.1
 Perpendicular 0.46 (a) 137
 to long 0.59 (a) 165
 axis 0.45 (a) 262
 0.20 108
 0.09 98.5

Screw gage 10, 50 mm long
 Lateral Parallel to 0.70 (a) 239
 resistance long axis 0.68 (a) 355
 0.79 (a) 340
 0.11 196
 0.08 181
 Perpendicular 0.56 (a) 222
 to long 0.57 (a) 408
 axis 0.33 449
 0.34 305
 0.34 131

 Head pull- 0.78 (a) 278
 through 0.43 (a) 378
 0.80 (a) 404
 0.33 101
 0.71 (a) 110

(a) Significant difference at a probability level of 0.05.

(b) Root mean squared error.

(c) Values in parentheses are coefficients of variation.

(d) The comparison was performed within the type of test; values
with the same capital letter are not statistically different
at 5% significant level.

Table 7.--Test results for staples under cyclic load.

 Average
 Nominal density
 Property Panel thickness (x)

 (mm) (kg/
 [m.sup.3])

Staple gauge 16, 38 mm long, 11 mm crown
 Face OSB 11 599
 withdrawal 15 649
 18 588
 MDF 16 791
 Particleboard 16 762

 Edge Parallel OSB 11 580
 withdrawal to long 15 650
 axis 18 605
 MDF 16 776
 Particleboard 16 741

 Perpendicular OSB 11 598
 to long 15 608
 axis 16 609
 MDF 16 775
 Particleboard 16 760

 Head pull- OSB 11 566
 through 15 688
 18 589
 MDF 16 778
 Particleboard 16 702

 Average holding
 capacity
 Property (observed y)

 (N)

Staple gauge 16, 38 mm long, 11 mm crown
 Face 377 (44.7) (c) D (d)
 withdrawal 752 (29.0) B
 825 (21.9) B
 1029 (10.2) A
 649 (19.8) C

 Edge 209 (47.2) D
 withdrawal Parallel 388 (34.4) C
 to long 461 (21.8) B
 axis 543 (14.7) A
 474 (20.7) B

 Perpendicular 238 (36.1) C
 to long 459 (27.9) B
 463 (35.4) B
 604 (13.6) A
 483 (10.9) B

 Head pull- 824 (22.6) C
 through 1438 (28.3) A
 1159 (18.1) B
 1346 (9.2) A
 1101 (13.1) B

 Regression
 equation
 Property (predicted y)

Staple gauge 16, 38 mm long, 11 mm crown
 Face y = 1.28x - 387
 withdrawal y = 1.74x - 378
 y = 1.65x - 145
 y = 0.21x + 859
 y = 1.53 to 516

 Edge y - 1.04 to 393
 withdrawal Parallel y = 1.55 to 616
 to long y = 0.74 + 16.2
 axis y = -1.55 + 1746
 y = -0.68x + 979

 Perpendicular y = -0.04 + 259
 to long y = 1.49 to 445
 y = 2.03x - 774
 y = 1.46x - 532
 y = 0.59 + 35

 Head pull- y - 1.24 + 123
 through y = 4.20 - 1447
 y = 1.49x + 280
 y - -0.79 + 1959
 y = 1.97 to 282

 Property r RMSE (b)

Staple gauge 16, 38 mm long, 11 mm crown
 Face 0.82 (a) 94.3
 withdrawal 0.57 (a) 176
 0.65 (a) 134
 0.05 102
 0.55 (a) 106

 Edge 0.79 59.4
 withdrawal Parallel 0.53 (a) 111
 to long 0.53 83.6
 axis 0.35 73.2
 0.20 94.3

 Perpendicular 0.002 83.9
 to long 0.50 (a) 108
 0.64 (a) 124
 0.48 (a) 70.8
 0.39 47.4

 Head pull- 0.49 (a) 159
 through 0.47 351
 0.53 (a) 173
 0.14 120
 0.54 (a) 118

(a) Significant difference at a probability level of 0.05.

(b) Root mean squared error.

(c) Values in parentheses are coefficients of variation.

(d) The comparison was performed within the type of test; values
with the same capital letter are not statistically different at a
5% significant level.

Table 8.--Comparisons of screw and staple holding
capacities under static and cyclic loads.

 Nominal
 Panel thickness

 (mm)

Screw gage 10, 25 mm long or staple gauge 16, 38-mm long, 11-mm crown
 Face OSB 11
 withdrawal 15
 18
 MDF 16
 Particleboard 16

 Edge Parallel to OSB 11
 withdrawal strong axis 15
 18
 MDF 16
 Particleboard 16

 Perpendicular OSB 11
 to strong 15
 axis 18
 MDF 16
 Particleboard 16

Screw gage 10, 50 into long or staple gauge 16, 38-mm long, 11-mm crown
 Lateral Parallel to OSB 11
 resistance strong axis 15
 18
 MDF 16
 Particleboard 16

 Perpendicular OSB 11
 to strong 15
 axis 18
 MDF 16
 Particleboard 16

 Head pull- OSB 11
 through 15
 18
 MDF 16
 Particleboard 16

 Screw average holding capacity

 Static Cyclic

 --(N)--

Screw gage 10, 25 mm long or staple gauge 16, 38-mm long, 11-mm crown
 Face 1087 (26.9) (a) A (b) 898 (37.4) A
 withdrawal 1448 (21.7) A 1448 (20.2) A
 1308 (21.3) A 1210 (25.8) A
 1394 (7.4) A 1394 (7.4) A
 1206 (12.5) A 1183 (9.5) A

 Edge Parallel to 712 (24.9) B 813 (23.8) A
 withdrawal strong axis 953 (29.9) B 1137 (16.4) A
 949 (32.4) B 1153 (23.0) A
 1239 (6.7) A 1194 (11.5) A
 808 (10.5) A 833 (10.8) A

 Perpendicular 801 (27.2) A 871 (18.2) A
 to strong 1047 (22.4) A 1121 (18.8) A
 axis 880 (30.2) B 1173 (25.7) A
 1191 (9.8) A 1206 (9.3) A
 827 (11.9) A 810 (12.5) A

Screw gage 10, 50 into long or staple gauge 16, 38-mm long, 11-mm crown
 Lateral Parallel to 1122 (35.3) A 953 (35.5) A
 resistance strong axis 1842 (24.7) A 1829 (27.0) A
 2201 (26.0) A 2162 (26.2) A
 2265 (7.0) A 2114 (9.6) B
 1154 (13.5) A 1037 (17.8) B

 Perpendicular 1127 (39.1) A 1225 (22.4) A
 to strong 2006 (27.7) A 1971 (25.9) A
 axis 2505 (22.1) A 2026 (24.0) B
 2247 (6.7) A 2162 (15.4) A
 1119 (13.2) A 966 (14.8)B

 Head pull- 1491 (22.5) B 1764 (25.7) A
 through 2677 (15.4) B 2918 (14.6) A
 2460 (17.8) B 2904 (23.4) A
 2697 (7.9) B 3008 (3.7) A
 1587 (12.0) B 1921 (8.3) A

 Staple average holding capacity

 Static Cyclic

 --(N)--

Screw gage 10, 25 mm long or staple gauge 16, 38-mm long, 11-mm crown
 Face 482 (35.0) A 377 (44.7) B
 withdrawal 820 (26.8) A 752 (29.0) A
 892 (27.0) A 825 (21.9) A
 976 (8.4) B 1029 (10.2) A
 630 (16.6) A 649 (19.8) A

 Edge Parallel to 204 (40.4) A 209 (47.2) A
 withdrawal strong axis 479 (25.6) A 388 (34.4) B
 564 (46.6) A 461 (21.8) A
 628 (21.5) A 543 (14.7) B
 513 (13.5) A 474 (20.7) A

 Perpendicular 277 (30.3) A 238 (36.1) A
 to strong 548 (18.1) A 459 (27.9) B
 axis 551 (27.1) A 463 (35.4) A
 612 (25.6) A 604 (13.6) A
 491 (11.5) A 483 (10.9) A

Screw gage 10, 50 into long or staple gauge 16, 38-mm long, 11-mm crown
 Lateral Parallel to -- --
 resistance strong axis -- --
 -- --
 -- --
 -- --

 Perpendicular -- --
 to strong -- --
 axis -- --
 -- --
 -- --

 Head pull- 882 (27.9) A 824 (22.6) A
 through 1148 (30.3) B 1438 (28.3) A
 1071 (32.5) A 1159 (18.1) A
 1387 (17.7) A 1346 (9.2) A
 842 (17.5) B 1101 (13.1) A

(a) Values in parentheses are coefficients of variation.

(b) The comparison was performed between static and cyclic tests;
values with the same capital letter are not statistically different
at a 5% significant level.
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Author:Wang, Xiaodong; Salenikovich, Alexander; Mohammad, Mohammad
Publication:Forest Products Journal
Geographic Code:1USA
Date:Apr 1, 2009
Words:5962
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