Study On The Damage Of Soft Package After Dropping

Plastic flexible packaging bags are the main form of food packaging.However,factors such as rough handling and falling from high places in the logistics process can easily cause the packaging bags to break,resulting in product loss and threatening the reputation of the company.At present,the phenomenon of broken bags in food logistics often occurs in the market,food and packaging companies are bothered by it.However,based on the existing literature and the research results with the top food flexible packaging companies in my country(Hangzhou Dingzheng Packaging Material Co.,Ltd.),there is very little research on the logistics of food flexible packaging bags.And the companies only rely on experience or rough experiments to solve this question.Scientific detection and protection methods are extremely lacking,which hinders the rapid development of the food packaging industry.According to the needs of the enterprise,this article first takes the red bean paste filling soft packaging bag as the research object,explores the mechanism of the soft packaging bag surface falling damage,and builds a flexible packaging bag internal pressure measurement system to measure the pressure within the bag when it falls,then use the system to measure the internal pressure of different packaging methods and logistics conditions,which provides a theoretical basis for the design of non-liquid packaging to prevent breakage.Finally,according to the enterprise’s proposal that if the liquid packaging bag is placed in the box by the way of “surface to bottom” or “side to bottom”,there may be different drop damage situation,the finite element analysis of the drop stress of the small liquid bag is carried out to study it.The main conclusions are as follows1.In order to explore the damage mechanism of the soft packaging bag surface,we observed the falling process of the filling material soft packaging bag surface by high-speed camera and recorded the falling state.It was found that(1)the geometric shape of the bag body was almost unchanged during the falling process;(2)the head and tail of the bag were suspended in the air.In the non-contact area,the side pressure of the filling here(hereinafter referred to as the internal pressure)can only be balanced by the internal tension of the film,so the internal force of the film here is extremely large;(3)the damage location is concentrated in the heat-sealed connection of the non-contact area(ie The heat-sealed area of the bag and the transition line of the normal film of the bag body,the same below).In summary,the analysis of the phenomenon of bag breakage of the flexible packaging bag should be carried out to analyze the force of the breakage-heat-sealed connection.Assuming that the geometric shape of the heat-sealed joint does not change during the drop,the damage mechanism is that the excessive internal pressure here causes the excessive internal force of the film,and it breaks after reaching the critical value.2.In order to determine the evaluation method of the anti falling performance of soft packaging bags,the difference between the failure samples of thermal sealing strength and positive pressure bursting test sample and the actual falling failure sample is compared.It is found that the state of the damaged sample of the positive pressure bursting method conforms to the actual drop condition,and the heat seal strength is not in accordance with the actual situation.It shows that the traditional method of detecting the bad sealing by the heat seal strength in the current enterprise can not effectively detect the anti falling and damage ability of the packaging bag,but it should be tested by the positive pressure bursting method.3.The effect of bag making technology on the falling resistance of soft packaging bags was studied.Firstly,through the micro observation of the joint of the heat seal,found that the heat sealing process will lead to the defects of the hole and thickness mutation in the joint of the heat seal,which makes it became the weak point of the bag when falling,increases the probability of damage.And the bursting strength of the bag made by different thermal sealing temperature was measured by positive pressure method,proving that the temperature of the heat seal will affect the drop resistance of the bag.The second factor is the length of the bag.The bursting strength of different length bags is measured by positive pressure method.It is found that the slight change of bag length will affect the fall resistance of the bag,but it is not significant(P<0.05).4.In order to detect the instantaneous internal pressure in the package when falling,a hardware system is built,which is composed of force sensitive strain gauge,resistance voltage module and voltage acquisition card,and the software system is designed by Lab VIEW software.The system can detect the instantaneous pressure in the bag when falling,verified by pressing experiment and the subsequent practical measurement.It provides a quantitative scientific method for the mechanical detection of soft packaging bag drop,which can replace the rough empirical method of the enterprise.5.The influence of falling height,stacking layer,bag length and corrugated board on the pressure of the drop moment was tested using the soft packaging bag drop internal pressure test system.The results show that:(1)the pressure inside the bag increases with the increase of the drop height(P<0.05);(2)the pressure increases with the increase of the number of layers and the difference is significant(P<0.05);(3)the change of bag length has no significant effect on the internal pressure when the bag filling quality is constant(P>0.05);(4)the increase of lining pad at the bottom of the carton can reduce the internal pressure and play a buffer rol e(P>0.05).The above conclusions can provide reference for the design of anti falling and damaged packaging.6.If the liquid packaging bag is placed in the box by the way of “surface to bottom” or “side to bottom”,there may be different drop damage situation,so this paper uses ABAQUS to analyze the drop of liquid packaging bags by finite element method,and preliminarily verifies the results by comparing the final state and the pressure comparison of special points.The results show that when the liquid bag falls,the maximum equivalent stress is from large to small,which is short side landing >long side landing > bottom landing.The maximum equivalent stress on the bottom landing is 63.39 MPa,the one on the long side landing is 140.984 MPa,and the one on the short side landing is 219.197 MPa.Adding another corrugated between the bag and the corrugated box bottom plate can reduce the equivalent stress,and the maximum stress of the bag body is only 121.94 MPa,which is about 19 MPa smaller than that without corrugated.Therefore,under the same conditions,it is better to put the liquid bag bottom landing to reduce the risk of fracture when stacking.If not,it is better to make the liquid bag long side landing and add the corrugated plate as buffer to reduce the risk of fracture.