First, the packaging function a protection function: the protection of the use of goods value, which is the primary function of packaging. B convenient features: mainly reflected in the convenience of storage and transportation, easy to use and easy to sell. C promotional functions: mainly in the appearance of the package, modeling and decoration is consistent with the new trend will play a major role. Second, the packaging structure design principles a scientific scientific principle is the application of advanced and correct design methods, the application of appropriate appropriate structural materials and processing technology, design standardization, serialization and generalization, in line with relevant laws and regulations, products to adapt to mass mechanized automatic production The B reliability reliability principle is that the packaging structure design should have sufficient strength, stiffness and stability in the circulation process can withstand the role of various factors and influence. C aesthetic aesthetics is to design the packaging to achieve the design and decoration design aesthetic requirements, including the structure of the six elements and the structure of the six rules. D economy is an important principle of packaging design, requiring a reasonable choice of materials, reduce raw material costs, reduce raw material consumption, require a reasonable design process, improve work efficiency, reduce costs and so on. Packaging structure design of the basic factors First, the contents of a physical properties of solid material, liquid, powder, and gaseous. B The chemical properties of the contents of the vulnerability, deformation, water resistance, moisture resistance, rust and anti-mildew and so on. C interior materials applications of food, medicine, electronics, chemicals and so on. Second, the packaging container design materials Modern packaging industry in the important packaging materials are paper, cardboard, plastic, metal, glass, ceramics and various composite materials. A Material of the physical properties: transparency, thickness, barrier and so on. B chemical properties of materials: chemical stability, safety, corrosion, rust and other characteristics. The mechanical properties of the material: strength, elastic modulus and so on. D material molding process: rheology, plasticity and so on. E Decorative materials: printability, smoothness and so on. Third, the circulation of environmental conditions a physical factors: shock vibration and stacking static pressure, etc. b biochemical factors: temperature, humidity, rain, radiation, harmful gases, microorganisms and so on. C Human factors: brutal handling and counterfeiting, etc. In the design of the package should be considered in the circulation of the measures taken and the sixth section of the design of the mechanical structure of the packaging structure design contains a lot of basic principles of mechanics, such as The compressive strength, rigidity and stability of the container, the stress concentration problem, the strength calculation of the pressure vessel, the bending of the metal structure, the mechanical problems in the press forming, and so on. This section of the mechanics of these basic theory and application of a brief introduction, in the future should be combined with specific learning content to further study. 1, the tensile properties of materials to engineering the most widely used, the most representative mechanical properties of low carbon steel, for example, the tensile test chart is as follows: It is divided into four main stages: 1), elastic stage: oa section, When the external force is removed, the deformation is completely restored. 2), the yield stage: ac, at this time there is a phenomenon of crystal slip, the temporary loss of resistance to deformation, and produce plastic deformation. 3), strengthen the stage: cd segment, resulting in irreversible plastic deformation. 4), local deformation: de, neck until broken. When the structural design, the general requirements of the material in the elastic range. But when the stamping process and other production process should use the plastic deformation characteristics of the material. First, the mechanical properties of the material The mechanical properties of the container is not only related to the structure, but also with the mechanical properties of materials are closely different, it must study the mechanical properties of the material. Mechanical properties are measured by means of a test method, typically by tensile and compression tests. 2, the material of other mechanical properties of the creep properties of materials: a certain temperature and stress (below the yield point), the material slowly over time the phenomenon of plastic deformation. Metal materials in the high temperature creep phenomenon, and the polymer will occur at room temperature. Stress relaxation: Under the conditions of temperature and initial deformation, the stress of the material decreases with time and is called stress relaxation. The fatigue limit of the material under the action of alternating stress: During the transport process, the package will be damaged after a period of time under the repeated action of vibration and shock, when the stress is much lower than the yield limit. So in the structural design to take into account the fatigue limit, reduce stress concentration, improve product surface finish and so on. Material hardness: hardness There are a variety of measurement methods, the general use of indentation, which means that the material in a small volume range of resistance to plastic deformation capacity. Fracture toughness of the material: reflects the ability of the material to resist crack propagation, obtained by the test test. 3, material design indicators and application strength indicators: reflect the material resistance to plastic deformation of the ability indicators, such as yield limit, strength limit, fatigue limit, creep limit, etc., is the main basis for strength calculation. Stiffness indicators: indicators that reflect the ability of the material to resist elastic deformation, such as elastic modulus, shear modulus, etc., are used when calculating the elastic deformation of the component, such as stiffness, static and stability problems. Plasticity index: that the material can produce plastic deformation of the degree, such as cross-section shrinkage, which is the basis of material stamping design. Toughness index: reflects the material strength and plastic comprehensive performance, is the energy index. Reflecting the ability of the material to absorb energy during deformation or fracture. Is an important indicator of the choice of materials. Second, the strength of the material to calculate the material in the tension, torsion, bending and other basic deformation of the case, when the maximum stress exceeds the strength limit of the material may be destroyed, so the design to carry out the corresponding strength check: the commonly used strength theory There is: the maximum tensile stress theory: as long as the component to withstand the maximum tensile stress to reach the ultimate stress value of the material will cause material damage. Maximum elongation line strain theory: As long as the material maximum line strain reaches a certain limit strain value, it will cause the material brittle fracture. Maximum shear stress theory: As long as the maximum shear stress in the component reaches a certain limit shear stress value, it will cause the plastic yield of the material. Shape change the specific energy theory: as long as the shape of the component to change the ratio can reach a certain limit, it will occur plastic yield. Thin-wall pressure vessel strength calculation In the metal container structure design, when there is a large internal pressure (such as spray cans, etc.), must be calculated strength, so as to select the appropriate material and thickness parameters, calculated as follows: Stiffness problem In the packaging structure design to consider a very important issue is the structural stiffness of the problem, packaging containers such as cartons, paper, metal cans, plastic containers, etc. must have a certain degree of stiffness, that is, the ability of structural resistance to deformation, In order to better protect the product and packaging structure itself. Different structures have different stiffness calculation methods, in the design should be based on specific circumstances to be selected. In general, the method to improve the stiffness of the components are: select the elastic modulus of the larger materials. (Such as steel drums, cans, plastic containers, etc.) Fourth, the stability of the structure calculation When the elongated rod or thin-walled structure (such as the wooden box in the structure of the column), the thickness of the material, , Corrugated board, etc.) by the pressure, even if the stress is much lower than the strength of the material limit, but also due to loss of balance and suddenly rapid deformation, or even damage, this phenomenon is called instability. For the elongated rod, the critical pressure can be determined by the Euler formula: the middle and small flexible rod should use empirical formula, can refer to the general material mechanics teaching materials. The main measures to improve the stability of the structure are: to reduce the length of the bar. Select a reasonable cross-sectional shape, try to increase the size of the moment of inertia. Increase the rod or plate end constraint. Choose a material with a large modulus of elasticity