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V} '21 13;") 1f “fig-717m This is to certify that the thesis entitled SIMULATED TRANSIT VIBRATION DAMAGE 0N RETORT POUCHES presented by POON KONGCHAROENKIAT has been accepted towards fulfillment of the requirements for MASTER degree in _RA£_|$AGJ.NG_ Date NOVEMBER h, 1980 0-7639 I 5239 '1'; $991 ‘ I Jllflsla $2002 uvcxuut PINES: 25¢ per day per item RETURNING LIBRARY MATERIALS: ____________...__.._._ Place in book return to remove charge from circulation records SIMULATED TRANSIT VIBRATION DAMAGE ON RETORT POUCHES By Poon Kongcharoenkiat A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE School of Packaging 1980 57% ($057 ABSTRACT SIMULATED TRANSIT VIBRATION DAMAGE ON RETORT POUCHES By Poon Kongcharoenkiat In this study packaged retort pouches were subject to vibration at the frequency at which the shipping containers were in resonance when stacked. The stacks were eleven boxes high as currently used in distribution. Both horizontal and vertical orientation of pouches were studied. Results showed that the vertically oriented pouches incurred more total damage. The top box had the greatest occurrence of damage in both orientations. When making pouch to pouch comparison, the horizontal orientation resulted in more damage in the lower boxes of the shipping load. This indicates that horizontally oriented pouches are more sensitive to compression from the boxes above. Finally, vibration tests on a unitized load were also conducted and resulted in less damage in both orientations. In the horizontally oriented pouches, the average occurrence of damage per box was reduced by half while the average occurrence of damage per box in the vertical orientation was slightly reduced. TO Oon Yun Huang My late mother, who has never seen any academic success of her only son ACK NOW LEDG EM EN T The author very sincerely wishes to express his thanks to Dr. James W. Goff, for patient guidance and help. Without his support my study program could hardly have been possible. I wish to extend my appreciation to my committee, Dr. Hugh E. Lockhart, Professor of School of Packaging and Dr. Thomas R. Pierson, Associate Professor of Department of Agricultural Economics. I also would like to extend my gratitude to those who worked diligently in helping this study: MS. Diana Twede, Senior Research Assistant in the School of Packaging, Mr. Terrence Baird, Instructor in the School of Packaging and also to Mr. Bunyad Sariga and Mrs. Patricia Atteberry for their assistance in preparing this document. Finally, I wish to thank my wife Somporn Kongcharoenkiat whose help during my study program was necessary for my graduation. ii TABLE OF CONTENTS Page ACKNOWLEDGEMENT. . ....................... ii TABLE OF CONTENTS ......................... iii LIST OF TABLES . . ............. . . . . . ....... iv LIST OF ILLUSTRATIONS. . . . .................... v INTRODUCTION ................... . ........ ' 1 Purpose . . . . ................. ' ........ 1 Method . . . . ......................... 1 Scope . . ........ . . . ................. 2 BACKGROUND....... ..... . ..... ...... 3 Vibration . .......... I ............ . . . . . 3 Literature Review .................... . 4 EXPERIMENTAL PROCESS ............ . . . . . . . . . . . 6 Equipment and Product ...................... 6 Conditioning . . ......................... 7 Product Damage ..... . ........... . . ...... 7 Vibration of Stacked Shipping Containers . . ............. 8 Vibration of Representative Boxes. ........ I ......... 8 Vibration of Unitized Stack. ...... . . . .i ........ . . IO RESULT AND DISCUSSION ....................... ll Damage Due to Pouch Orientation. ................. 11 Nature of Damage on Pouch ........... . ..... . . . 15 Effect of Unitizing ........................ 18 RECOMMENDATION AND CONCLUSION. . . . . . . .......... 26 LIST OF REFERENCES ................. . ....... 29 iii LIST OF TABLES Page Nature of Damage in Each Box . ..... . . . . . . . . 12 Amount of Damage AS a Result of Horizontal Orientation ..... 16 Amount of Damage As a Result of Vertical Orientation ...... 17 Amount of Damage As a Result of Horizontal Orientation (Unitized vs Ununitized) . . . . . . . . . . . . . . . ' ...... 19 Amount of Damage As a Result of Vertical Orientation (Unitized vs Ununitized) . ...... . . ............ 21 Damage on Opposite Side versus Total Damage . . . ...... 25 Representative Boxes and Occurrence of Damage . ....... 27 iv LIST OF ILLUSTRATIONS Page Horizontal Orientation. . . . . . . . . . . . . ...... . . 9 Vertical Orientation. . . . . . . . . . . . . . ........ 9 Damage Inspection Areas (8) . . . . . . . . . . . . . ..... 9 Damage Inspection Areas (10). . . . . . . ..... . . . . . . IO Occurrence of Damage versus Position of the Box . . . . . . . . . 13 Relationship of Amplification and Number of Box in Column . . . . lit INTRODUCTION The retort pouch is a flexible pouch designed to be filled with a food product (1) and fully heat processed. Because of its convenience and better product quality, the market for retortable pouched products in Japan reached sales of] 4 trillion Yen in 1968.(1 I) In the U. 5., it has been estimated that a $2 billion market iS realistic (13) by 1981. However, damage to the retort pouch as a result of vibration especially at the resonant frequency, has not yet been seriously studied. 1. Purpose The purpose of this study is to observe the vibration damage on retort pouches at the most severe condition - resonant frequency. The main area of concern is to see the nature of damage occurring to the pouch. By Studying the vibration performance of the pouch in both the horizontal and vertical configurations, many comparisons of vibration damage may be made concerning the effects of orientation. 2- Manes: ASTM Standard D 999—75 - Methods for Vibration Testing of Shipping Containers, Method C Unitized Load or Vertical Stack - at resonance tests was applied throughout this study. Some deviations from this standard are as follows: (a). Dwell time at resonant frequency was performed for one hour, instead of the recommended 15 minutes dwell time. Thus, more damages can be expected in the pouch. (b). Acceleration amplitude for severity test is l G (peak to peak) instead of 0.5 G (peak to peak) as recommended, so more damages would be expected. In addition, pouch and corrugated box fatigue were not considered in this study. In fact, according to Godshall (1971), corrugated-board fatigue has little effect on the strength of corrugated containers.(3) 3. Scope The study is divided into two main parts: the study of the nature of damage in different orientations resulting from vibration of a Shipping load and the effect of unitizing on the vibration damage of the pouches. The unitized load is considered to be a method of reducing vibration damage. BACKGROUND In the past few years, the attention given to packaging and to the environment through which products travel has increased immensely. One of the main areas of the environment receiving this attention is the vibration environment and the damage it causes. 1. Vibration (9) Vibration is oscillating motion about a reference point. All products will undergo vibration during transit. Sources of these inputs are many; the suspension and tires of a semi-trailer and the suspension of a rail car are examples. Vibration is transmitted through the floor of the truck or rail car and is propagated through the entire load. A product's natural frequency is dependent upon the design and construction of the product and its components. When vibrated at its natural frequency, the product system will amplify the input considerably, thus greatly increasing chances of product damage. Due to the complex nature of products, the only practical method to determine product natural frequency is in the laboratory, using vibration equipment designed to operate over transit frequency ranges.(9) During transportation, the containers on pallets form a column, which has its own frequency response. The product package system exhibits its own natural frequency while the stack produces natural frequencies which are unique to the column. With a top load, the bottom package will act like a Spring. Thus the higher. the pallet load, the more severe is the vibration of the top container. 2. Literature Review As far as the retort pouch is concerned, several laboratory vibration tests have been conducted. U. S. Army Natick Laboratories, which is the pioneer in this field, has conducted a rough handling test by using vibration (one hour of vibration at 268 cycles per minute or 4.5 Hz, at an acceleration of l G). The results show that the flexible material was capable of withstanding this vibration hazard as well as metal cans.(2) ' Another vibration test was conducted by Star di Agrate Briango, Milan, Italy. Five shipping cases of product were vibrated at 190 to 195 cycle per minute (3.25 Hz) for 30 minutes, followed by five drops from 12 inches. The performance (10) result was no visual damage. Nughes reported in 1973 that no significant failure or breakage and 13.596 minor damage (less evident failure defined as not visible to the naked eye) from his performance test.(12) Supplementary testing consisting of a truck shipment of ten cases for a minimum of 500 miles was carried out. On return, the failure rate was found to be less than 0.25%.“2’ Regarding the transportation test, U. S. Army Natick Laboratories also conducted one in 1971. An integrated Engineering Test and Service Test (ET/ST) was conducted. Approximately t4,000 cases of test item were shipped from Kansas City, Missouri to test sites loacted in Virginia, Georgia, North Carolina, Louisiana and as far as Panama. As noted in the report, the performance of the cases and packages from the shipping and handling standpoint was considered "excellent" for all means of transportationft‘) Another shipping test was conducted by Reynolds Metals. Palletized shipments were made by rail and truck over 1,000 miles distances, some of the major findings were: (a). All retorted pouch foods can be successfully shipped in palletized loads by both rail and truck for distance up to 1,500 miles and probably further. ' (b). There is no need to glue pouches into the cartons. (c). Vertical placement of cartons into cases should be evaluated.(6) The last finding is an expression of the need for this study, so that the degree of damage between horizontal and vertical orientations can be compared. EX PERIM ENTAL PROC ESS The intent of this laboratory performance test is to simulate, by means of controlled vibration, the effect of shipping upon retort pouches. The durability of the retort pouch, defined as the ability of the package to withstand the rigors and physical abuse of normal distribution without excess failure or safety hazards, is among the first of performance requirements that has to be faced. In order to conduct this study on vibration damage of a stack of cases of retort pouches, it was necessary to use a number of different pieces of equipment. The equipment was utilized in such a way that the acceleration level and frequency range could be controlled and the damage to product could be determined. 1. Equipment and Product The vibration tests were conducted on an electrohydraulic vibrator and this vibration was controlled by a servo system to provide a constant acceleration over a range of frequencies. Some type of guide was also necessary to control the amount of horizontal movement of the packages and prevent them from falling down from the stack. These guides were made of plywood and were placed one inch from the side of stack. In addition to the above mentioned equipment, a microscope, with 48 power magnification, was used to identify damage incurred by each pouch. Twenty two identical boxes of retort pouches were utilized. Some boxes of product were used several times to form a stack of unitized load height, so that the inspection time could be reduced and still obtain satisfactory results. Sample retort pouches were filled with Chicken A La King. The dimensions of each pouch were 5 1/2" x 8 5/8" (measured in finished Shape) and each contained 8 ounces of product. The pouches which are commercially available were made by Continental Group. Paperboard cartons measuring 6 1/4" x 8 1/2" x 7/8" were used as secondary packages for pouches as a protecting package so that the pouches can be protected from physical abuse during transportation. Finally, all of the fore-mentioned packages were placed in regular Slotted fiberboard containers (RSC). These c’ontainers were made of 275-pound test, C-flute, corrugated board, with inside dimensions of 7 3/4" x 10 3/14" x 5 3/4". This corrugated shipper assured a tight fit for all the Sides of the secondary package inside the shipper. ‘ 2. Conditioning To assure consistent board properties, all the samples were preconditioned at the Standard condition of 73°F and 50% RH for at least 2# hours before testing. The testing atomsphere was also controlled at the same conditions. 3. Product Damage The laboratory test was set up to study the product damage from vibration. The damage was determined after all package testing and was classified into 3 categories as follows: I (a). Critical Damage: leakage from pouch such that product can be seen either by the naked eye or through a microscope. (b). Major Damage: pouch damage which could be seen by naked eye but no product leaks. (c). Minor Damage: microscopically visible cracks (48X)on the surface of the pouch. If the damage area at the surface did not Show a cracked solid line on the pouch surface, it would be judged as no damage. (I. Vibration of Stacked Shipping Containers Eleven boxes of product, which form one pallet load height during Shipping, were inspected and left 2# hours in the controlled atmosphere. Twelve cartoned pouches were loaded in horizontal orientation in each of the eleven boxes (see figure 1) and subjected to vibration at the resonance frequency at 7.2 Hz with amplitude at l g (peak to peak) for 1 hour. When this test was completed, all pouches in the eleven boxes were inspected. The tested pouches were then packed in new corrugated boxes, in the vertical orientation (see figure 2), and the test was repeated. A new resonant frequency was observed at 7.7 Hz and the stack was vibrated at this new resonant frequency. Other than this change, the equipment set up and inspection were the same as the one just described. During the inspection, all the damage on the pouches were identified according to the position of damage as in figure 3. 5. Vibration of Respresentative Boxes After learning the nature of damage in each orientation from the previous testing, both of the tests were performed again at the resonant frequency of the sample packed in the representative boxes. Due to the limited number of samples, only three new representative boxes at the bottom, middle and top position were used for damage inspection. Again, an inspection of each pouch was conducted both before and after vibration. But in this step and the next, the damage was identified in 10 separate areas (see figure 4) instead of 8 as in the previous inspection, so that more details of damage could be compared. FIGURE 1 HORIZONTAL ORIENTATION FIGURE 2 VERTICAL ORIENTATION FIGURE 3 POUCH IN 8 POSITIONS DAMAGE INSPECTION AREAS (8) 10 The pouch faces were identified as the front face where the pouch code numbers were found and the other face was identified as the back face. By this classification of faces, the occurrence of damage on opposite face was observable. Figure 4 POUCH IN 10 POSITIONS DAMAGE INSPECTION AREAS (10) 6. Vibration of Unitized Stack In order to reduce damage, a shipping method, which involved unitizing the whole stack height, was proposed. Three more new boxes with horizontally oriented pouches Were put in the representative position and 8 old boxes with the same (horizontal) pouch orientation were stacked to reach the shipping height (11 boxes). Then, the whole stack was tied together in the vertical direction by pressure sensitive tape. The system was vibrated again at the same amplitude as before but at the new resonant frequency of 6.2 Hz. The same experiment was repeated for vertically oriented pouches where the resonant frequency was now 7 Hz. Finally, the experiment ended with the inspection of all pouches in 6 boxes and the damage was determined in 10 different locations on each face of each pouch. RESULTS AND DISCUSSION For each tested pouch, all the damage found was marked on the pouch upon observing it through the microscope. In all, 3!} boxes of product or l1108 pouches were inspected. l. Damage Due to Pouch Orientation For the first stage of the experiment, all the pouches in 11 boxes of both horizontal and vertical orientation had been inspected. The position of damage on each facing of the pouches was identified by 8 different. positions. With regard to pouch location, "front face" refers to side with the printed code number and the "back face" was the opposite side. By comparing the results of both types of testing, the vertical orientation had more total damage than the horizontal orientation, in every category of damage type. The average of total damage of vertical orientation is 6.0 occurrences of damage per pouch more than the horizontal one (Table I). There was also some relationship between the box position on this stack and the damage (Table l and Figure 5). Theoretically,‘the higher the box in the stack the more damage should occur. This phenomena can be explained by amplification factor of the box on the stack. Boxes stacked on boxes act like distributed springs and masses, and the stack resonates. This is evidenced by sizable amplification of input vibration to cause the top package to jump. Kusza and Young (1974) have worked out the relationship of amplification factor and number of container in the (9) stack in curves in figure 6. ll 12 TABLE I AMOUNT OF DAMAGE IN EACH BOX Box # Horizontal Orientation Vertical Orientation Type of Damage Type of Damage Critical Major Minor Total Critical Major Minor Total Top 11 a ll 59 74 9 17 147 173 10 - - 29 29 — 2 52 5a 9 - - 41+ 44 - a 54 58 8 — - 22 22 — 7 55 62 7 - l 43 £14 2 5 37 at: Middle 6 2 5 37 all - 1 I6 17 5 - - 38 38 - 1 16 17 a 1 - 14 15 — - 25 25 3 - ‘ 1 a7 48 - - 12 12 2 - - 18 18 - - 7 7 Bottom 1 l l 40 #2 l l 7 9 Total 8 19 391 1418 12 38 428 478 ’7 38 M S.D. 17 (I7 Occurrence of Damage Occurrence of Damage 100 80 60 140 20 200 180 I60 140 120 100 80 60 40 20 13 FIGURE 5 _L p-l—up—un-n—fipqu-r hon-nan I OCCURRENCE OF DAMAGE VS. POSITION OF THE BOX a—np-D-v-Q i=38 1 2 3 a 5 6‘ 7 8 9 10 J Numbe‘f'Bro ox Bottom Middle Top in Column HORIZONTAL ORIENTATION I. —-1—db-ul—dhnl——-J-qb~d[~ -~ I "“""" 32:94 1 Bottom 1 111117 8910 Top VERTICAL ORIENTATION . 11 Number of Box in Column l4 Amplification of Top Package :{l in Column FIGURE 6 RELATIONSHIP OF AMPLIFICATION AND NUMBER OF BOX IN COLUMN SOURCE: "Testing" by Thomas J. Kusza and Dennis E. Young.(9) 15 Damage, other than that to the top shipping container, in the horizontal orientation is independent of the position in the stack (Figure 5). The average damage in the horizontal configuration is 38 occurrences of damage per box with a standard deviation of 17. In the vertical orientation, the average damage and standard deviation (i: M, S.D. :48) are much higher than in the horizontal orientation. The damage occurrence in the horizontal orientation did not vary with the position of the box. On the other hand the damage occurrence in the vertical orientation seemed to have a tendency to relate to the position of box on the stack (the higher the box the more damage to the pouch). 2. Nature of Damage on Pouch The individual pouches in each box in both horizontal and vertical orientations had more damage in position one and two which are the upper portion of the pouch (Table 2 and 3). One reason for this is that both edges of the upper part have a notched area which is triangular Shaped in order to create a convenient opening point for the pouch. These notched areas cause the weak Spots on the pouch where bending and creasing are likely to occur in vibration. Regarding the occurrence of damage on each face of the pouch, there was no significant data to compare on one face relative to the other. For example, in horizontally oriented pouch in Table 2, 6 out of 11 boxes had more occurrence of damage on front face. As the vertical orientation, 7 of 11 boxes had more occurrence of damage on back face. However, where packages were folded, more severe damage was found on the inside of the fold rather on the outside. h. 16 TABLE 2 AMOUNT OF DAMAGE AS A RESULT OF HORIZONTAL ORIENTATION 1— 5 :1 4 1 | I 7 .. __ .1. _. __ 8 l 3 1 ., l 6 Box # 1 2 3 4 6 7 8 UPpapretr LPoawretr FFraoCnet :23: To ta1 Top 11 22 22 21 9 - - - 44 30 36 38 74 10 M3 2 10 3 - I - 16 13 18 11 29 9 19 14 6 4 - I - 33 11 20 24 44 8 9 4 3 5 - I - 13 9 7 15 22 7 19 11 11 4 - - - 30 15 26 19 45 MiddIe 6 14 9 11 5 1 1 3 25 19 24 20 44 5 12 10 6 8 - 'I 1 23 15 19 19 38 4 5 2 5 2 - - — 8 7 10 5 15 3 16 9 14 7 - 1 1 26 22 26 22 48 2 6 3 6 3 - - - 9 9 10 8 18 Bottom 1 20 17 1 - — 3 1 38 20 22 42 Tota1 155 103 94 50 1 9 6 265 154 216 203 419 x' = 38 S.D. = 17 .-__—. _. _. _. . __—_—— 17 TABLE 3 AMOUNT OF DAMAGE AS A RESULT OF VERTICAL ORIENTATION 5 I I 1 1 2 7 .. _.' .. s l l 3 I 4 6 Upper Lower Front Back Box fl 1 2 3 4 5 6 7 8 Part Part Face Face Total Top 11 59 49 31 27 - 2 3 ' 2 110 63 72 101 173 10 17 13 6 8 3 - 7 - 35 19 24 30 54 9 27 15 5 8 - - 3 - 43 15 22 36 58 8 17 12 8 14 - 3 5 3 32 30 35 27 62 7 17 11 7 6 - ‘— 2 1 29 15 21 23 44 Middle 6 7 6 4 - - - - - 13 4 5 12 17 5 6 5 3 3 - - - - ll 6 7 10 17 4 ll 3 8 3 - - - - 14 ll 16 9 25 3 6 3 2 1 - - - - 9 3 6 6 12 2 5 - l - - - 1 - 5 2 l 6 7 Bottom 1 5 2 1 l ’- - - - 7 2 5 4 9 Total _ 177 119 76 71 3 5 21 6 308 170 214 264 478 i = 44 SOD. '3 [‘8 18 3. Effect of Unitizing This section deals with the comparison and unitized shipping loads. The stack of boxes, mounted on the vibration table, was subjected to vibration input at its own natural frequency. All the pouches were divided into 10 positions for inspection, rather than 8 as in the previous inspection. Thus the degree of damage between the sides and central parts of the pouch were able to be compared. For this analysis, three new boxes were placed at the bottom, middle and the top of the stack as representative boxes. By this method fewer samples were used and a good comparison also could be done. The‘rfirst comparison will be the nature of total damage on unitized and ununitized shipping loads. This will be followed by a comparison of horizontal versus vertical pouch orientation subject to unitizing effects. Finally, a comparison of occurrence of damage on each section of the pouch also will be conducted. 3.1 Pouch Orientation The results of the vibration'test on unitized representative boxes reconfirm the results of the previous tests. Again, more damage occurred in the vertical orientation than in the horizontal orientation (Tables 4 and 5). The middle and bottom representative boxes had much less damage than the tOp one, especially on the vertically oriented stack. This means that the horizontally oriented pouches are more compression-sensitive than the vertical ones. As far as the unitizing effect was concerned, the unitized horizontal orientation reduced damage much more than the ununitized vertical one. Especially on the top box of the horizontally oriented stack, the occurrence of damage was reduced by half due to unitizing. Comparing the vertically oriented stack, the occurrence of damage on the unitized one was slightly reduced. l9 .Q.m on n 8 u m :2 3 e... an R2 RR 2: - - - - RR RR : me am em :38 OR R 2 m 2 m 2 - - - - m m R n m m Eofiom 2 M: RR 2 ON 2 R - - - - e e L M: R R 28:2 6: 8 mm mm em 9 Re - - - - M: 2 R R em em 8e .88 88.2 88". 85o «Em tea tea 2 R w R e A e R R R R 6m xomm Each 5304 Loan: 38% 89:55 \D d" N UN M --4 N AQMNHCZD m> QMNHCZDV ZOE CMNCLZDZDV ZOC.<._.Zm:mO IE... :xmm> LO thwmm < m< mU< SEC LO HZDOE< . .8: .h R2 " .a.m mm n m ”RR RD E 8 DR 6: R2 - .. - R S Re : Rm 3 8 =38 w e R a R m R - - - - R z - L R m 588m 9R 3 2 e 8 2 2 - - - - n e R L R 6 28:2 eem Rmz e_z mm mm_ 002 was - - - . R we Ne w on an an ace n .93 MM “com“ 28:8 8% BMW? Ream: 2 a m R e n e m R L e 6m DMDZHPZOU .1 .. n mum/E. 8.85 83:5 23 Because all the samples in these tests were new samples from the manufacturing plant, overall occurrence of damage in each box after testing was muchmore than the previous described tests. The reason for this is that some new occurrence of damage due to testing would not occur in the same previous area of damage. Especially on the pouch's surface more occurrence of damage was found (Position 1-6 in Tables 4 and 5). However, it can be concluded at this stage that the unitizing method helps to reduce the occurrence of damage in both orientations. 3.2 Damage Position During the inspection, the pouches were divided into 10 positions in order to identify the damage. The only difference was the area along the width of the pouch's surface which was divided into 6 positions instead of 4 in the former inspection. It was found that almost two-thirds of all the damage in the vertical orientation was on the sides instead of the central portions. Regarding the upper and lower part of the pouch, the results were just like the previous tests. The majority of damage, specifically almost half of all damage, is on the upper half (Table 4). Especially on the vertically oriented pouches the total damage on the upper-left portion of the pouch (Position #1) had more damage than any other portions. One reason is the upper part of the pouch moves easier and is thinner than the lower part where most of the product is settled. Another reason is the notched areas on both edges of the upper portion of pouches caused the weak areas as described in the result of previous tests. Again, the damage on the front and back face of each pouch was difficult to describe because the amount of damage on each face was similar. During the vibration test, pouches had equal opportunity to be folded on either face. 24 During the inspection in these stages, all the occurrence of damages which were on opposite sides of the pouches were observed (Table 6). The maximum percentage of damages in one box which were on opposite side were 56 but the average of 2696 of damage were found opposite to each other. ‘ Even though the unitizing method was able to reduce some degree of occurrence of damage, the top box of the unitized vertically oriented pouches still had almost the same amount of damage as in the ununitized ones. The conclusion is that unitizing methods were quite effective in reducing total occurrence of damage in the horizontal orientation but did not work so well in the vertical one. 25 TABLE 6 DAMAGE ON OPPOSITE SIDE VS TOTAL DAMAGE Type of Box Total Opposite . . . . 9”" Damage (96) Stack Orientatlon Position Damage Damage Total Damage Ununitized Horizontal Top 1 16 54 47 Middle 45 10 22 Bottom 20 1 5 Vertical Top 248 137 55 Middle 37 9 24 Bottom 16 2 l3 Unitized Horizontal Top 50 ll 22 Middle 23 2 9 Bottom 26 1 4 Vertical Top 246 138 56 Middle 24 11 46 Bottom 8 1 13 Average 26 RECOMMENDATION AND CONCLUSION Overall, the results obtained from the study were very interesting and enlightening. A few assumptions that were made seem to be reasonable. In particular, the assumption that the fatigue can be neglected for all the boxes seems to be certain because the natural frequency of each orientation did not change significantly. To summarize the vibration tests, each incidence of damage was classified as critical, major, minor damage and identified on 8 or 10 different portions on the pouches. The overall results are shown in Table 7. The Study verified that whole shipping load of retort pouches was a frequency-sensitive system, with resonant frequencies ranging from 5.8 - 7.9 Hz. These resonant responses occur within the range of frequencies likely to be present in transportation vehicles. This should be seriously considered when selecting or designing shipping containers. Overall comparison of damage on pouches showed that vertically oriented pouches incurred more damage than the horizontal one. But the lower (boxes of the stack of vertically oriented pouches (Boxes III-6) had less occurrence of damage than the boxes of horizontally oriented pouches. The cause of damage can be summarized as follows: 1. The springness of the corrugated box increases the occurrence of damage on the pouch during vibration. 2. Notched areas on both edges of pouches cause weak areas subject to vibration damage. 3. Headspace in the upper portion of the pouch provided an area which can easily be creased and become damaged. 26 27 TABLE 7‘ REPRESENTATIVE BOX AND OCCURRENCE OF DAMAGE Nature Box Damage Total Natural of Stack Orientation Position Box Damage Frequency Ununitized Horizontal Top 74 Middle 44 Bottom 42 160 7.2 Vertical Top 173 Middle 17 Bottom 9 199 7.7 Ununitized Horizontal Top 1 16 Middle 45 Bottom 20 181 5.8 Vertical Top 248 Middle 37 Bottom 16 301 7.9 Unitized Horizontal Top 50‘ Middle 23 Bottom 26 99 6.2 Vertical Top 246 Middle 24 Bottom 8 278 7.0 28 4. The nature of the product in a retort pouch affects the severity of damage. According to Burke and Schulz (1972) semi-solid products caused fewer failures than pumpable ones.(2) 5. The size of the pouch as compared to the size of carton can be a factor in damage. When the cartons are too big, the vibration can cause more occurrences of damage due to more moving space inside the carton. On the other hand, when the cartons are slightly smaller than the pouches, the more severe folding of the pouch will also increase the amount of damage. This concept also applies to the size of the cartons in relation to the corrugated shipping boxes. From the test results and suspected causes of vibration damage on retort pouches, the market success of these products might be improved by slightly modifying the package system in order to reduce vibration damage in transit. For example, shrink or stretch wrapping using corrugated trays could be considered in lieu of corrugated shipping boxes. Changing the position of the notched‘area from both side edges to the top edge of pouches might reduce losses. Finally, redesigning the secondary package, in order to obtain a tighter fit, could produce a system which is less sensitive to vibration. In light of these tests, a few recommendations for future testing may be helpful. First, the amplitude level of input should be raised and lowered beyond the value used to see if the nature of damage does in fact level off at 1 g (peak to peak) level inputs. Second, the pouches in future tests should also be varied to consider another kind of product. The third possibility might be to test the pouch without any carton. Some saving on production costs by eliminating the carton may be possible. In this case a biotest for pouch leakage inspection should also be considered. 10. ll. 12. 13. 14. 15. LIST OF REFERENCES Barker, J., 1979, "The Retort Pouch - A Review," Plastics in Retail Packaging Bulletin Vol. 1, No. 12, March, pp 2. Burke, P. T., Schulz, G. L., 1972, "The Comparative Performance of Flexible Packages and Metal Cans," Technical Report No. 73-62-GP, US Army Natick Lab., pp 25. * Godshall, W. D., 1968, "Effects of Vertical Dynamic Loading on Corrugated Fiberboard Containers," USDA Forest Service Research Paper No. FPL 94, Forest Products Lab., Madison, Wisconsin, pp 16-17. Godshall, W. D., 1971, "Frequency Response, Damping, and Transmissibility Characteristics of Top-Loaded Containers," USDA Forest Service Research Paper No. F PL 160, Forest Products Lab., Madison, Wisconsin. Godshall, W. D., 1978, "Transportation Vibration Effects on Unitized Corrugated Containers," USDA Forest Research Paper No. FPL 322, Forest Products Lab., Madison, Wisconsin. I Goldfarb, P. L., 1971, "Pouch for Low-Acid Foods," Modern Packaging, January, pp 25. Gordon, G. A., Messent, P. A. and Smith, R. J. F., 1979, "Vibration Testing of Palletized and Unit Loads," Paper Present to Third IAPRI International Conference, Stockholm, Reprinted in PIRA Report No. PK 14 (R). Gordon, G. A. and Smith, R. J. F., 1979, "Developing Better Vibration Tests for Packages," Paper Present to Third IAPRI International Conference, Stockholm, Reprinted in PIRA Paper No. PK 10 (R). Kusza, Thomas J. and Young, E. Dennis, 1974, "Testing," Package Development, November/December. Lampi, R. A., 1977, "Flexible Packaging for Thermoprocessed Foods," Advance in Food Research 22, pp 304-377. Mizutani, T. A., 1972, "Retort Pouch," Graphic Arts Japan, Vol. 13, pp 34-36. Nughes, F., 1973, "Perspective Report on Retortable Pouch Packaging in Europe," Report No. T 7313, Packaging Institute, St. Louis, Missouri. Peter, W. J., 1975, "Retail Debut of Retort Pouch Earns Consumer Acceptance," Food Product Development, March, pp 24. Szczeblowski, W. J., 1971, "An Assessment of the Flexible Packaging System for Heat-Processed Foods," Technical Report No. 71-57-GP, US Army Natick Lab., pp 23. Urbanik, T. J., 1978, "Transportation Vibration Effects on Unitized Corrugated Containers," USDA Forest Research Paper No. FPL 322, Forest Products Lab., Madison, Wisconsin. nrcHIan STATE UNIV. LIBRARIES IIIIIVIIIIIIIIIHIIIIIIIIIIIIIIIIlllllllllllllllIIIIIIIII 31293104109743