Eg llHlllHWHlWIN!WIN!WHWHWIMC! THS ‘ nmnw lllllllllllllllllfllll/lllllllllllllllllllllllllllllllllllll 301405 3288 This is to certify that the thesis entitled LOSS IN COMPRESSION STRENGTH OF CORRUGATED CONTAINERS DUE TO OFFSET AND ITS EFFECT ON STABILITY OF PALLETIZED LOADS presented by SAN—YOON (JIM) RHA has been accepted towards fulfillment of the requirements for MASTER degree in W KW DR. S. P L SINGH Major professor Date JANUARY 31, 1996 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution LIBRARY Michigan State University PLACE IN RETURN BOX to remove thin cbockwt from your «card. TO AVOID FINES return on or baton date duo. DATE DUE DATE DUE DATE DUE MSU In An Afflrmotlvo Action/Equal Opportunlty Institution 7 7 , mm d LOSS IN COMPRESSION STRENGTH OF CORRUGATED CONTAINERS DUE TO OFFSET AND ITS EFFECT ON STABILITY OF PALLETIZED LOADS BY Sang-Yoon (Jim) Rha A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1996 ABSTRACT LOSS IN COMPRESSION STRENGTH OF CORRUGATED CONTAINERS DUE TO OFFSET AND ITS EFFECT ON STABILITY OF PALLET IZED LOADS BY Sang-Yoon (Jim) Rha This study investigated the effect of lateral offset on the compression strength of single wall corrugated containers. Tests were conducted to evaluate stack stability in normal and tropical climatic conditions for different offsets. The results show that between 20% to 64% of the stacking strength is lost due to the presence of offset. This loss is further increased due to exposure to higher humidity environments. The data also showed that the initial 5% reduction in offset area resulted in the highest reduction in compression strength. Additional amount of offset reduced the compression strength but at a lower rate. The results also showed that offset contributed to a higher degree of strength reduction than exposure to high humidity for 48 hours. The results also showed that the stability of stacked palletized loads is neatly affected by the amount of shift of the center of gravity of the individual unit loads and the quality of the pallet. Copyright by Sang-Yoon (Jim) Rha 1996 I would like to dedicate this thesis to my parents for their love and belief. ACKNOWLEDGEMENT I would like to first express my sincere thanks to my major professor, Dr. S. Paul Singh, andtoothern'lembersofmyg'aduatecomnittee, Dr. Gary Burgess and Dr. George E. Mase. Their assistance throughout my research and analysis is gratefully acknowledged. I would also like to thank Stone Container, Laimbeer Packaging Company and Ross Products for the materials and supplies and the funding which made this research possible. lwould like to thank all the faculty and staff ofthe School of Packaging and all those who helped me in during the course of my graduate studies. I would like to extend my special thanks to my colleagues with whom I worked on various projects. Finally. I am especially thankful to my father. Jin-Koo Rha, and my mother. Kytng-Joo Lee for their everlasting intellectual and financial support throughout the program. I like to thank my sister, brother-in-law. and my close relatives for their guidance and support. TABLE OF CONTENTS LIST OF TABLES ......................................................................................... LIST OF FIGURES ...................................................................................... 1.0 INTRODUCTION ................................................................................ 2.0 erERATURE REVIEW ...................................................................... 3.0 EXPERIMENTAL DESIGN ................................................................. 3.1 Experiment 1 ........................................................................... 3.2 Experiment 2 ........................................................................... 4.0 DATA AND RESULTS ........................................................................ 4.1 Experiment 1 ........................................................................... 4.2 Experiment 2 ........................................................................... 5.0 CONCLUSIONS ................................................................................. LIST OF REFERENCES .............................................................................. APPENDIX A .................................... APPENDIX B ................................................................................................ vi Page vfi x 1 3 10 10 16 20 20 30 37 38 4O 58 Table PQN 10. 11. 12. 13. LIST OF TABLES BoxSpecificationofExperiment1 .......................................... DisplacementsforLaterelOffset in Experiment1 ................... Displacements for Diagonal Offset in Experiment 1 ................ Percent Reduction in Compression Strength of Double Stacked Boxes as a Function of Humidity (English Units) ........ Percent Reduction in Compression Strength of Double Stacked Boxes as a Function of Humidity (Metric Units) .......... Percent Reduction in Compression Strength as a Function of Lateral Offset at Normal Climatic Condition (English Units)... Percent Reduction in Compression Strength as a Function of Lateral Offset at Normal Climatic Condition (Metric Units) ..... Percent Reduction in Compression Strength as a Function of Lateral Olfset at Tropical Climatic Condition (English Units)... Percent Reduction in Compression Strength as a Function of Lateral Offset at Tropical Climatic Condition (Metric Units) ..... Percent Reduction in Compression Strength as a Function of Diagonal Offset at Normal Climatic Condition (English Units). Percent Reduction in Compression Strength as a Function of Diagonal Offset at Normal Climatic Condition (Metric Units)... Percent Reduction in Compression Strength as a Function of Diagonal Offset at Tropical Climatic Condition (English Units) Percent Reduction in Compression Strength as a Function of Diagonal Offset at Tropical Climatic Condition (Metric Units). vii Page 10 12 16 21 22 24 25 26 27 28 29 31 32 Table 14. 15. 16. A-1 A-4 A-5 A-6 A-8 A-9 A-1 O A-1 1 A-12 LIST OF TABLES (cont) Average Percent Reduction at Normal Climatic Conditions for Lateral and Diagonal Offsets .................................................... Average Percent Reduction at Tropical Climatic Conditions for Lateral and Diagonal Offsets .............................................. CenterofGravityPredictionandStabilityinaStack ............... Compression Strength of Control Data which is in Perfect Alimment (English Units) ......................................................... Compression Strength of Control Data which is in Perfect Alignment (Metric Units) .......................................................... Compression Strength Test of Lateral Offset in Type A Box (English Units) .......................................................................... Compression Strength Test of Lateral Offset in Type A Box (Metric Units) ............................................................................ Compression Strength Test of Lateral Offset in Type 8 Box (English Units) .......................................................................... Compression Strength Test of Lateral Offset in Type B Box (Metric Units) ............................................................................ Compression Strength Test of Lateral Offset in Type C Box (English Units) ......................................................................... Compression Strength Test of Lateral Ofi‘set in Type A Box (Metric Units) ............................................................................ Compression Strength Test of Diagonal Offset in Type A Box (English Units) .......................................................................... Compression Strength Test of Diagonal Offset in Type A Box (Metric Units) ............................................................................ Cornpressicn Strength Test of Diagonal Offset in Type B Box (English Units) .......................................................................... Compression Strength Test of Diagonal Offset in Type B Box (Metric Units) ............................................................................ viii Page 33 2‘3 45 47 49 51 52 55 LIST OF TABLES (cont) Table Page A-13 Compression Strength Test of Diagonal Offset in Type C Box (English UnIts) ..... 56 A—14 CompressionStrength TestofDiagonal Offset in TypeC Box (Metric Units) ............................................................................ 57 LIST OF FIGURES Figures Page 1. TestSet-tpforExperiment1(Contrcl) ................................ 13 2. Test Set-m for Experiment 1 (Lateral Offset) ...................... 14 3. Test Set-q) for Experiment 1 (Diagonal Offset) ................... 15 4. SampleSet-upDescriptionforExperimentZ ....................... 18 5. Stacking Patterns Developed for Experiment 2 .................... 19 A-1 PictueonypeA,8,andCBoxesinExperiment1 ............. 40 A-2 Picture of Perfect Alignment Testing in Experiment 1 .......... 41 A-3 PictueofLateral OffsetTewng in Experiment1 ................. 42 A-4 Picttre of Diagonal Offset Testing in Experiment 1 ............. 43 8-1 Illustration of Procedures in Experiment 2 ........................... 58 8-2 Picture of Similac Porductl Tray Sample in Experiment 2.... 59 8-3 Picture of Experiment 2, Option 1 ........................................ 60 8-4 Pictue of Experiment 2, Option 2 ........................................ 61 8-5 Picture of Experiment 2, Option 3 ........................................ 62 86 Picture of Experiment 2, Option 4 ........................................ 63 8-7 Picture of Experiment 2, Collapsing of the Stacked Structwe ............................................................................... 64 8-8 Pictue of Experiment 2, Collapsed Structure ...................... 65 1.0 Introduction Long term stability of stacked pallet loads is one of the important requirements forwarehouse and distribution package systems. A lack of complete information about the strength of a product/package system in a stacked configuration can result in leaning stacks that could eventually fall. Such scenarios though rare can result in excessive product damage and possibility of serious tunan injury. lnmanycases, packagingprcfessionalsoflenusecomputersoftware programs to optimize packages in trailers and warehouses. Most such tools often provide good information on cube utilization and different methodologies to arrange packages. However, these models do not account for factors such as inferior quality pallets, partially damaged packages, localized offset in the palletized load, uneven floor surface, and irregularity in the geometry of the package due to fabrication. All these factors can collectively produce an accelerated phenomenon that would cause packages in stacked pallets to yield and result in a catastrophic situation. The purpose of this study was to investigate the effect of offset in single wall corrugated containers to see how a loss in compression strength could affect the load bearing capacity of stacked packages. This provided a better understanding 2 of the package performance at the micro level. The effect of humidity and degree of offset was evaluated. The stability of palletized loads was studied at the macro level as well. This consisted ofstacking the pallets at varying degrees of offset that would result in the center of gravity of the top loaded pallets to shift sideways and result in a tipping scenario. In order to accomplish the objectives of this study, two different kinds of experiments were conducted. Each individual experiment is discussed in detail and is identified as ‘Experiment 1' and ‘Experiment 2'. The first experiment evaluates the package performance at the micro level and the second at the macro level. Detailed information on test procedures used and data collected is provided in Chapter 3 and 4 of this thesis. The primary objectives of this study are listed below. 1. Determine the loss in compression strength as a function of offset and exposure to humidity in three different sizes of single wall regular slotted containers. 2. Evaluate the effect of lateral offset to the center of gravity of stacked palletized loads on their vertical stability. 3. Perform actual simulations of palletized load offset scenarios that would cause stacked pallets to become unstable and fall. 2.0 Literature Review Warehouse costs are minimized by using full cubic capacity of the storage space and maintaining a fast change in stock cycle time. Of particular importance is the long term stability of stacked palletized loads. The bottom box or container inthestackmustcanytheresidual loadofthepackagesaboveitforthefull storage time without collapse or excessive bulge to the box or container itself. However. not fully mderstanding the capability of the package system’s strength in the stack. full ctbic utilization of the warehouse to achieve cost minimization could lead to leaning stacks that would potentially collapse. This could produce secondary damage as once a stack starts to collapse it would propagate to adjacent columns and would produce a ‘Dominos Effect'. Today, corrugatedcontainers areusedtopackageamajorityofproducts in the United States and account for over 90% of industrial and consumer goods (Fiedler. 1995). The design requirements critical for one type of packaging application may not be suitable for another application since factors such as storage time, humidity, stacking pattern. package weight, transportation all contribute to the overall performance of the package. It is therefore necessary to evaluate the effect of these various factors on the total padtage performance. 4 The load beefing ability of a box is related to the strength of the vertical panels in compression. The dominant influence on compression strength is comer rigidity since budding of corrugated sides can take place at relatively low loads. Theboxisweakestinthecenterpanelsandstrongestatthecomer. Thegreatest stacking strength is obtained by arranging the stack so that the strongest areas match together and the weakest areas also align. This provides a uniform deflection along the horizontal edges of each panel. This is ideally achieved by column stacking the boxes directly above one another. When interlock stacking is used,thestrongstiffcomersofone panel matchtheweakerareas inthosepanels inadoininglayersbothaboveandbelow. Thiscreatesunevendeflection alongthe horizontal edges ofthe panel causing excessive panel bulge and consequently box failure at lower loads than those for column stacking. Column stacking is said to show as much as 29% greater stacking strength than an interlocked stack (Wright, et al, 1992). The compression strength of a box depends on various factors such as board properties, construction, style. as well as its size and shape. The compression strength measured during laboratory testing generally determines a load at which the box collapses. This value is considerably higher than actual conditions since it does not account for creep (long term storage) or effects of the climatic environment. Thus a safety factor is generally used In real life applications. The safety factor will depend on the effect of moisture, the storage time. effect of stacking, the handling methods and distance and type of transportation (Wright et. al., 1992). The McKeefonnula, developed by McKee, Gender and Wachutta (1963) at the Institute of Paper Chemistry, provides corrugated box designers with an empirical formula for predicting top-to-bottom compression strength (CS) of corrugated boxes using the following equation: C8 = 5.8745 Pm hm 2““ where Pm is column crush in him, h is caliper of board in inches, and z is box perimeter in inches. This formula applies only to standard conditions (73 °F, 50 %RH) and RSC style boxes of a uniform shape where the depth of the box is at leastifloftheboxperimeter. There isnofactor toaccountfortheeffectofboth climatic, storage, and shipping environments. (McKee at al., 1963). Anothermethodtopredictcompressionstrengtliofcormgated shippers uses the Mullen Burst Test. lt determines the compression strength based on the perimeter of the box, burst strength value, and type of flute (Hanlon, 1985). However. theabove method alsodoesnotaccountfortheeffectsofcreepand humidity. A recent study done at the Institute of Paper Chemistry uses a better representationofconpression perfonnancebyaauallytesting the entire pallet load andevaluafingtherelafiveconuibufionofeadicomponentintennsoftotal package strength (box and its contents). They express the total load supported by each padtageintennsofthenmiberoflayersinthestackabovethebottom box ltalso shows the contribution of internal cell partitions and inserts and column or 6 interlockingstackingpattemonthetotalloadsupportstrength. Theresultsshowed that to have a better stack alignment a smaller cell size is required (SPl, 1993). However, the report does not investigate the effect of reused wooden warehouse pallets. Pallets with broken deck boards, wide voids between deck boards, and varying stacking patterns that have overhang, will all result in causing instability in stacked palletized loads. Under these circumstances, the potential stacking strength is also reduced. In addition, the ratio of the height of the stack to the size of the pallet also affects stacking performance. Increase in stack height will reduce the stability of the stack and result in an increase in leaning. Many studies have been done to investigate the effect of humidity on corrugated box performance. Maltenfort (1989) documents various studies that have studied this interaction. However though all studies show a reduction in compression strength on exposure to humidity, different levels of reduction were found among various investigators. This is attributed to the variation in the corrugated board manufacturing process, the consistency of the quality of paper used for the medium and liner, and the adhesive used to bond the different layers of paper to form the corrugated board. The results from various studies show that tearstengdwandpmdureshenghmcombinedboardareknowntodeaeaseand the stretch on liners increase on exposure to higher humidities. The porosity of paper decreases at higher humidities since the paper becomes saturated quicker. Packaging fresh produce that is often wet or allowing boxes to sweat during storage can have disastrous effects on stacking performance due to absorption of moisture in the board. levans (1973) developed an empirical factor to account for the effect of humidity on compression strength of corrugated boxes at different humidities. The firstsectionofhispapershowshowmoistuecontentaffects compression strength. He also investigated the effect of cycling certain range of humidities throughout someperiodoftimemditsinfluenceonthestacking strength. Sincethemoisture content of the outside boxes in a pallet is higher than that of the inside boxes in a pallet load, a floating platen compression tester was used to seek out the weaker members of the box. a situation similar to that expected in the warehouse. By this reasoning the report goes on to say that in an interlocking stacking pattern, the stronger boxes in the center of the arrangement would contribute to the entire stacking strength and increase the safe stacking period. In conclusion, the box collapsed almost immediately at the critical moisture content and the rate at which the failure occurred depended on the contents of the box, as well as on the limits of the high and low extremes in cyclic humidity. In column stacking, the reduction incompressionstrengthbyctwigingtherelativetunidityfrom 50%RH to85 %RH was found to be 26.7%. (levans, 1973). Beardsell (1960) cited a Refrigeration Research Foundation Scientific Advisory Council study that found that in general, the paper fibers soften as they increase in length, and thereby lose strength with gain in moisture. The continued expansion and contraction of paper fibers caused by cyclic humidity can weaken the fibers to the extent of structural failure. Also, the quantity of moisture available 8 tothefibersontheoutsideofthestackis differentfromthatwithinthestadt, more often in tightly stacked packages. There will appear a differential gradient of strength across the containers. He concluded that this strain could play a role in pallet load failing due to lack of uniformity. Beardsell (1960) goes on to state that stresses and strains on packages caused by extemal atmospheric conditions and byirhemalreadionsofflecufiertsofflrecontainerareapfimesourceofpmblem in the warehouse. Typical compression failures reported by Kellicutt (1963) state that the size and shape of the box not only determines how it will fail in compression but also the maximum load it will attain. For shallow boxes that are compressed in the top-to- bottom direction, failure results almost entirely by crushing along the top and bottom horizontal score lines. As box height increases, compressive failure results from acornbinationofcrushing alongthescore lines and budding ofthe side panelsof the box. Increase in length and width of the box will generally increase the compression strength. However, increase in depth ofthe box generally reduces the compression strength. Finally, after reading a specific height, the failure is almost entirely due to the result of budding. Kellicutt further investigated the effect of bearing surface, length of time the box supports a specific dead load, and staddng alignment factors. The compression strength decreased about 23% in perfectly aligned three high stack of boxes as compared for a single high B-flute box. This lower strength occurred because the top surface of the top box in the stack and the bottom surface of the 9 bottom box in the stack were the only surfaces bearing on the flat parallel platens ofthetestingmadiine.1heothertoparidbottornsufacesofthe boxes inthestad< weremakingacontact onthemeventoporbottomsufacesofthe adjacent boxes. Misalignment in the stadt reduced the strength more because the four vertical edges were misaligned and they are the stiffest parts of a box Edges that did not beardirectlyontopofeadrotherbutboresomeplaceonthebridgeofthepanel betweentwoofthemcausedareductioninstaddngstrength. Whencomparingthe stadting pattern, the interloddng stack showed 32% less compressive strength as compared to the column stack Maltenfort (1988) also investigated similar performance of corrugated containers as a function of staddng patterns. His results show that from changing the 3 tier column stadted load to the 3 tier interlodtingly stacked load, a 45% reduction in staddng strength occurred. In terms of inspecting the importance of the supporting area of the load, a 1 inch overhang in all four sides of the pallet resulted in a 32% reduction in compression strength, in a 3 tier column stad< of conugated boxes. 3.0 Experimental Design In order to accomplish the objectives of this study. two different experiments were conducted. Ead't individual experiments was identified as ‘Experiment 1' and ‘Experiment 2'. The respective test materials and methods used for each experiment are discussed in this chapter. 3,1 QPERIMENT L Materials: In ‘Experiment 1,’ three different sizes of C-flute corrugated board boxes were tested. Boxes were taped with '3M Brand Packaging Tape'. The box specifications for the three sizes is listed below in Table 1. Table 1. Box Specification of Experiment 1 10 ‘l 1 Conditioning and Test Methods: All samples were conditioned using the American Society for Testing and Materials Standard (D 4332) - “Standard Practice for Conditioning Containers, Packages, or Padtaging Components for Testing’. Two simulated warehouse atmospheric conditions mre selected for this study. Normal (23.0 t 1.0 °C @ 50 :I: 2.0 %RH) and Tropical (40 :t 2.0 “C Q 85 :I: 5.0 %RH). Standard conditions were measured and monitored using a Hygro-thennograph (Model number 594) recording instrunent. which records both relative humidity and air temperature. The sample boxes were conditioned for 48 hours at the tropical atmosphere in the environmental d'Iamber before being tested. The ASTM D 642 test method was used for compression testing of the corrugated boxes after they were subjected to conditioning. The test recommends touseacompressiontesterthathasafixedplaten and appliesa load ataconstant rate of 0.5 in! min. A preload of 50 lbs. was used for zero deflection. All samples were compression tested using a Lansmont Corporation Compression Tester (Model No. 76-5K). This machine provides a digital readout of force to within 1 3% accuracy and deflection reading to within :1: 1% linearity. Both the maximum force at failure and corresponding deflection were measured for all the box types and offsets used in this study. Procedures: Ten sample boxes of each size were tested for compression strength using a compression tester described above. These samples were conditioned at normal conditions as described in the previous section. These boxes were stacked in pairs and the total compression strength of a two high stack with perfectly aligned edges andcormrswasrneasured.1hisdatawasused asthe ideal strength ofa perfectly 12 aligned stack condition and represented the 'control' value. This test setup is shown in Figure 1. All subsequent test data was compared to this value. A second set often sample boxes were subjected to conditioning at the tropical conditions. These boxes were also tested in the perfectly aligned condition. The next phase of the tests consisted of initiating a 'lateral offset" among a pair of stadted boxes. This is shown in Figtre 2. Three different amounts of lateral offsets were evaluated. These were represented by the percent area of contact between the lower and upper box. The three levels were 95%, 90% and 85% contact area. The distance of lateral offset was determined that would provide the above required percent area of contact. These values are shown in Table 2. Table 2. Displacements for Lateral Offset in Experiment 1 type Lateral The third phase of this experiment consisted of initiating a “diagonal offset' among a pair of stadted boxes. This is shown in Figure 3. Three different amounts of diagonal offsets were also evaluated. These were represented by the percent area of contact between the lower and upper box The three levels were 95%, 90% 13 A .288 F EoEEonm .2 Elam amok .F 9:9”. / / o2< cam can 2: .o 52.: "32> E2". "Bo; noL. 14 23:0 .993 v :costooxw L2 3-8m «no... .N 93mm coco E25 3 do; seem can e55 522: "32> Eoi "Bo; no... 15 comuo 3885 v F Eostooxw .9 Elem amok .9 9:9“. \ o2< seem can 2.. .o 5.22: "so; EOE "32> no... 16 and 85% contact area. The distance of offset was determined that would provide the above required percent area of contact. These values are shown in Table 3. Table 3. Displacements for Diagonal Offset in Experiment 1 of The data was collected for stacked boxes after conditioning at both normal and tropical conditions. A total of 380 boxes were tested for all different sizes and test conditions. 3,2 EngERlMENT z Materials: In ‘Experiment 2' the offset to stacked palletized load was studied to determine the overall stability. The palletized loads were staged at the Michigan State University Salvage Yard so that any tipped pallet load does not cause potential injury. A 48" X 40' wood stringer GMA style pallet was used. The load consisted of plastic cans with aluminum tops that were packaged in corrugated 17 trays measuring 165" X 11" X 2.75“. The can was a 212 X 304 style two piece (Aluminum top I Plastic body) can. The palletized load weighed 2070 lbs. A fork truck was used to stack the palletized loads in the staging area. The palletized loadsweremarkedalongthededtboadtodetenninetheamountofoflset between stadted pallets. Procedure: This test was performed to determine the stability of the actually stacked pallet loads as a fmction of lateral offset. The instability of the stack of pallet loads was created by shifting the center of gravity of the pellets (Figure 4) stadted on top of the bottom pallet. Thedifferentpalletstadtconflgtrationsareshmvn in Figure 5. Thetestwas started with a perfectly aligned pallet stack as shown in Option 1. This is the condition of perfect stability where the center of gravity of all pallets pass through thesamestraightline.1'heviewofpallets shown are along the 40inch dimension. The Option 2 shifts the top two pallets collectively sideways. This lateral shift was performed in 6 indr increments. Theoretically this lateral shift could be done to maximum offset of 20 inches. However this assumes a very good quality pallet base. In a real situation a wood pallet would crad< before this condition due to concentrated load on the bottom deckboards. Similarly two additional conditions were studied as shown in Option 3 and Option 4. 18 N Eoetoaxw .8 529.35 938 macaw .v 9:9”. ..o__oa 9: :0 9o; 238233.?— \ aged c .380 32.8 o... a 52?. 32> E2“. 33> no... Stacking Patterns Option 3 Option 4 Figure 5. Stacking Patterns Developed for Experiment 2. 4.0 Data and Results Two different experiments on structural stability were performed. The data collected and the results of these experiments is discussed in this diapter. 1.1 5mm 1; The raw data for all the compression tests on the conugated containers for the various conditions performed in Experiment 1 are listed in Table A1 to A14 (Appendix A). The data is shown in both English and Metric units. These tables summarize. peak compression strengths and corresponding deflections of lateral and diagonal box offset in the three different sizes of boxes tested. The pemnt reduction of compression strength was calculated as follows: % Reduction in CS = madmm; mosmmcmmx 100 Ave. C8 of Control Samples The average percent reduction in compression strength in the three box sizes on exposure to the tropical storage condition as compared to normal storage condition was 16%, 19%, and 24% respectively for Type A, Type 8, and Type C boxes. This is also shown in Table 4 and 5. The larger size boxes showed a 20 21 E 8.3 .2 men. E 8.3 d. can 5 . seam , 36.30.5250 a. cozoacom .cooaeo moxom coxomfi 3530 do £9.95 5385,50 c_ cozeacom accused .v can... Exams O ".03: .ooiofi. £523 a “.03 3832 coEccoo emacoum cans—=0 EE: space Ease: Lo oozes“. e on AEo E. 5 .9. «8 is on. c .9. EN £53» e 9.3. £58m a coma. 59.9.6 5 .ooEoF .uanz oozes—com Eooaod cozficoo 322m 0.65:0 ES esoé sees: as 822:“. e we moxom coxomaw 2250 do 25:25 co_mmEano E cecacom «cooaod .m 298. 23 greater reduction in compression strength on exposure to humidity. Tables 6 and 7 show the percent reduction in compression strength of corrugated boxes as a function of the Lateral Offset at Normal Climatic Conditions for the three types of boxes tested. The data shows that the 95% contact area offset, resulted in between 20% to 27% reduction in compression strength compared to the control samples. Subsequent reduction in contact area to 90% and 85% showed further reduction in compression strength by as much as 47%. It is clear from comparing data between Tables 4(5) and 6(7) that even a 5% reduction in contact area caused by lateral offset shows a greater reduction in compression strength than boxes exposed to tropical climatic conditioning. Tables 8 and 9 show the percent reduction in compression strength of corrugated boxes as a ftnction of the Lateral Offset at Tropical Climatic Conditions for the three types of boxes tested. The data shows that the 95% contact area offset, resulted in between 42% to 43% reduction in compression strength compared to the control samples. Subsequent redudion in contact area to 90% and 85% showed further reduction in compression strength by as much as 64%. Tables 10 and 11 show the percent reduction in compression strength of corrugated boxes as a function ofthe Diagonal Olfset at Normal Climatic Conditions for the three types of boxes tested. 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E 8.3 E 00.3 E 8.. 8 «0 8 .0 8 8 .o. .8 .o. 08 .o. 8.. .o. 8. 083 E 8.: E 3.3 E .03 E 00.3 8 3 8 0.. 0.. 3 .o. 3.0 .o. 08 .o. 08 .o. 08 <83 00.< 000m 00.< 0000 00.< 000m 00.< 000m. 00.< 00mm 00.< 000m 00.< 000m :_ 89:00 :_ 89:00 :_ 89:00 :. Magoo :_ 89:00 :. 89:00 :_ 89:00 29 ES 8.0.2. 8.880 808.0 .882 .0 80.5 8500.0 .0 8.8000 0 00 50:95 8.0008800 :_ 8.8000: 800.00 .5 0.00 .r .8 9.3 80 8.3 .8 3.3 .8 5.3 8 «e .8 8 .8 8 .9. 8. .9. SN .9. e3 .9. .8 0 83 80 8.3 80 8.3 .8 8.: E. 3.: .8 00 .8 .0 .8 8 .9. 8. .9. 8. .9. 08 .9. 80 0 83 .8 8.3 .8 8.: 80 8.: Es 3... .8 3 8 8 .8 3 .9. 8. .9. wt .9. 08 .9. 80 < 83 00.< 000m. 00.< 000m. 00.< 000m 00.< 000m 00.< 000m 00.< 000m 00.< 000m :_ 69:00 :_ «09:00 :_ «09:00 :_ «09:00 :_ 69:00 :_ «09:00 :_ 59:00 .8 8 8 8 .8 8 8 8. 30 It is clear from comparing data between Tables 4(5) and 10(11) that even a 5% reduction in contact area caused by diagonal offset shows a greater reduction in conpressimsuengmmanboxesemosedtompicaldimaficcondifioning. Alsothe diagonal offset generally produced a greater reduction than lateral offset. Tables 12 and 13 show the percent reduction in compression strength of conugated boxes as a futction ofthe Lateral Offset at Tropical Climatic Conditions for the three types of boxes tested. The data shows that the 95% contact area offset. resulted in between 42% to 46% reduction in compression strength compared to the control samples. Subsequent reduction in contact area to 90% and 85% showed further reduction in compression strength by as much as 60%. Tables 14 and 15 show the average percent reduction for both lateral and diagonal offset at normal and tropical climatic conditions respectively. 1.2 mm 2; The degree of instability of stacked pallet loads was evaluated. Various conditions of lateral offset were staged using a fork truck to validate the model developed by the Consortium of Distribution Packaging at Michigan State University (Bugess, 1995). Table 16 shows these various conditions and also identifies if the overall system is stable or unstable. These were experimentally verified and some of these conditions are shown in the various photographs in Appendix B. Some of the drawbacks of the theoretical model that was evaluated are briefly discussed. The model assunes a good homogeneous weight distribution on 31 .025 002000. 820000 2.0520 .0209. .0 00:0 00000.0 .0 00.800“. 0 00 500000 00.000.00.00 0. 00.8000... .0020: .m. 0.000 0:. 00.0. E 00. .. 02 00.0. E 0.0. .x. 00 .0 .0 .x. 00 .2 3.0 .2 .00 .2 .00 .2 00. 083 .0. 00... E 0.0. .0. .00. E 00.. .0 00 00 .0 .x. 3 .2 000 .2 .00 .2 0.0 .2 .0. 083 E. 00.0. .0. 0.0. 0:. 00.0. 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G xom 35 Table 16. Center of Gravity Prediction and Stability in a Stack 8' Displacement at Top Option 1 Vertically aligned with the CG with No Displacement of bottom pallet load Stable Option 2 6' laterally to the right of with 6' Displacement the CG of bottom pallet load Stable Option 3 4' laterally to the right of S bl with 6' Displacement ta e at Middle & the CG of bottom pallet load 4' Displacement at Top Option 4 8" laterally to the right of S bl with 6' Displacement ta e at Middle & the CG of bottom pallet load 4" Displacement at Top Option 4 10' laterally to the right of *U bl with 6' Displacement nsta e at Middle & the CG of bottom pallet load * Both the top and middle samples tumbled down to cause stack failure. 36 the loaded pallet. This may not be true in real life loads that are stagger layered. Also the model assumes a good quality and strong pallet (high bending stiffness). In most applications this may not be true especially with reused wooden pallets whereioadconcentrationonthedeckboard memberswill causethemtofail before the theoretical model. Uneven floor surface, partially damaged packages in the pallet load, type of load restraining method (shrink wrap, stretch wrap, banding, etc) all will cause the load to become mstable before that predicted by the model. 5.0 Conclusions On the basis of this study, the following conclusions were reached: 1. The results show that both lateral and diagonal offset caused a greater percent reduction in compression strength as compared to humidity. The percent reduction in compression strength was found to be between 20% and 52% at normal conditions and between 42% to 64% at tropical conditions. 2. The results from the stability of stacked pallet loads experiment showed that the vaious factors that could cause accelerated instability in the stack are: quality of the pallet. condition of packages, load restraining method, center of gravity, non- homogeneous loads, and uneven floor surface. 37 LIST OF REFERENCES American Society for Testing and Materials. 1994. Standard Test Method for Determining Compression Resistance of Shipping Containers, Components, and Unit Loads. D 642-90. American Society for Testing and Materials, 1994. Standard Practice for Conditioning Containers, Packages, or Packaging Components for Testing. D 4332-89. Beardsell, AC., 'Corrugated Containers Under Refrigeration,’ TAPPI, vol. 12, 1960, p. 225-228A Birgess. 6.. “Evaluating the Degree of Instability in Pallet Load Stacks," School of Packaging, Michigan State University, East Lansing, Ml., 1995. Fiber Box Association. Em m; M Rolling Meadows, IL, 1989, p. 2-9. Fiedler. Robert M., W93 chkagigg MM. 481 Carlisle Drive, Hemdon, Virginia: Institute of Packaging Professionals, 1995, p. 139-157. Hanlon, J.F.. 11mm 3 m 533393333 234 99., McGraw- Hill, Inc., 1984, Chap.14. levans. Uldis l., 'Effect of Ambient Relative Humidity on the Moisture Content of Palletized Corrugated Boxes,’ Institute of Paper Chemistry, 1973. Kellicutt, KO. “Effect of Contents and Load Bearing Surface on Compressive Strength and Stacking Life on Corrugated Containers,“ TAPPI, vol. 46, Jan. 1963. Maltenfort. George G., W flipping 99333333, Plainview, NY: Jelmar Publishing Co., Inc. 1988, p. 113-157. Maltenfort. George 6.. 2009:1002 and Man. at $0200: Containers. Plainview, NY: Jelmar Publishing Co., Inc., 1989, p. 62-83. McKee, RC. J.W. Gander, and JR Wachuta, 'Compression Strength Formula for Corrugated Board,’ The Institute of Paper Technology. Sept. 1963. ' 39 Singh, S.P.. Private Communication. Michigan State University. School of Packaging. East Lansing, MI. SPI. 'Stacking Performance of Plastic Bottles in Corrugated Boxes.’ New York. N.Y.: The Society of Plastics Industry. Inc. 1993. Wright, P.G., P.R. Mchnlay, E.Y.N. Shaw, W W 5959;, Victoria, Australia: Arncor Fibre Packaging, 1992, p. 46-64. Appendix A Raw Data Results and Illustration of Experiment 1 Figure A-1. Picture of Type A, B, and C Boxes in Experiment 1 41 Figure A-2. Picture of Perfect Alignment Testing in Experiment 1 42 Figure A-3. Picture of Lateral Offset Testing in Experiment 1 43 Figure A-4. Picture of Diagonal Offset Testing in Experiment 1 02.02.00 0 .0 0600.6 00.000.00.00 0 0.0 0 . .0 0. ...o .0 00.0 00 0 .0 0. 00.0 00 00.0 00 0.00.0.0 00.0 .00 0.0 00. 00.0 000 00.0 .0. 00.0 000 00.0 000 02 00.0 000 0.0 00. .00 000 .00 00. .00 000 00.0 000 0 00.0 ..0 00.0 .0. 00.0 0.. ...0 000 00.0 000 00.0 000 0 00.0 0.0 00.0 000 .00 000 00.0 .00 .00 .00 00.0 000 0 00.0 000 00.0 0.. 00.0 000 ...o .0. .00 000 00.0 000 0 0.0 ..0 00.0 .00 00.0 0.0 00.0 .0. .00 000 .00 000 . .0.. 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Compression Strength Test of Lateral Off-Set in Type A Box (English Units) Conditioning Sample # 1 492 0.79 High Humidity High Humidity High Humidity High Humidity High Humidity 11 C.S. : Compression Strength Df. : Deflection 47 Table A-4. Compression Strength Test of Lateral Off-Set in Type A Box (Metric Units) Conditioning Sample # High Humidity High Humidity High Humidity High Humidity High Humidity Std. Dev. 5 1 CS. : Compression Strength Df. : Deflection Table A-5. Compression Strength Test of Lateral Off-Set in Type B Box (English Units) Conditioning Sample # Ambient High Humidity High Humidity High Humidity High Humidity High Humidity 47 44 0.23 37 C.S. : Compression Strength Df. : Deflection 49 Table A-6. Compression Strength Test of Lateral Off-Set in Type B Box (Metric Units) Conditioning Sample # High Humidity High Humidity High Humidity . 11 High Humidity 1 High Humidity 147 121 17 C.S. : Compression Strength Df. : Deflection Table A-7. Compression Strength Test of Lateral Off-Set in Type C Box (English Units) Conditioning Sample # Reduction C.S. Df. C.S. Df. 74 41 High Humidity High Humidity High Humidity High Humidity High Humidity 42 0.1 24 12 0.8. : Compression Strength Df. : Deflection 51 Table A-8. Compression Strength Test of Lateral Off-Set in Type C Box (Metric Units) Conditioning Sample # Reduction C.S. Df. Ambient 2.92 Ambient 2.03 1 Ambient High Humidity High Humidity High Humidity High Humidity 4 High Humidity 5 161 Ave. 1 Std. Dev. 1 CS. : Compression Strength Reduction C.S. Df. 1.88 1. 2.11 1.68 1 1 0.1 Df. 1 139 144 11 Df. : Deflection 52 Table A-9. Compression Strength Test of Diagonal Off-Set in Type A Box (English Units) Conditioning Sample # Reduction 08. Df. Ambient Ambient High Humidity High Humidity High Humidity High Humidity High Humidity 0.13 0.8. : Compression Strength Df. : Deflection Table A-10. Compression Strength Test of Diagonal Off-Set in Type A Box (Metric Units) Conditioning Sample # High Humidity High Humidity High Humidity 1 4 High Humidity 1 High Humidity 171 1 165 124 17 13 C.S. : Compression Strength Df. : Deflection Table A-11. Compression Strength Test of Diagonal Off-Set in Type B Box (English Units) Conditioning Sample # Reduction C.S. Df. C.S. Ambient High Humidity High Humidity High Humidity High Humidity High Humidity 74 79 1 1 C.S. : Compression Strength Df. : Deflection Table A-12. Compression Strength Test of Diagonal Off-Set in Type B Box (Metric Units) Conditioning Sample # High Humidity High Humidity High Humidity High Humidity High Humidity C.S. : Compression Strength Df. : Deflection Table A-13. Compression Strength Test of Diagonal Off-Set in Type C Box (English Unit) Conditioning Sample # Reduction C.S. Df. 1.1 High Humidity High Humidity High Humidity High Humidity High Humidity 24 C.S. : Compression Strength Df. : Deflection 57 Table A-14. Compression Strength Test of Diagonal Off-Set in Type C Box (Metric Units) Conditioning Sample # High Humidity High Humidity High Humidity High Humidity High Humidity 141 12 C.S. : Compression Strength Df. : Deflection Appendix 3 Illustration of Experiment 2 Illlll llllll LLIJ lIllT Step iii) Step ii) Step i) Step v) Figure B-1. illustration of Procedures in Experiment 2 59 Figure B-2. Picture of Similac Product! Tray Sample in Experiment 2 Figure B-3. Picture of Experiment 2, Option 1 61 Figure B-4. Picture of Experiment 2. Option 2 62 Figure B—5. Picture of Experiment 2, Option 3 Figure B-6. Picture of Experiment 2, Option 4 Figure B-7. Picture of Experiment 2, Collapsing of the Stacked Structure 65 Figure B-8. Picture of Experiment 2, Collapsed Structure HICHIGRN STRTE UNIV. LIBRRRIES illllllilllillillllillllillllllilliiiiIllilllllllillllilllllill 31293014053288