Due to uncertainties in the complex transport environment and conditions, such as the goods can not reach the destination on time or the transportation cost exceeds the expected goal, and the goods are damaged due to vibration impact, weather conditions and other transport environmental factors, resulting in losses, etc., it is directly Affects the reliability of the entire commodity transportation system. The study of the reliability of commodity transportation systems is to minimize the uncertainties in the entire transportation system, ensure the normal flow of goods, enhance flexibility and certainty, and increase the speed and quality of cargo delivery under the premise of optimal cost. Achieve real optimization of transportation management and improve the competitiveness of enterprises. According to relevant statistics, 70% of goods flow failures are due to improper packaging. Reasonable packaging is the main measure to overcome unreliable transportation. Reasonable packaging can save packaging costs, shorten transportation time, improve the efficiency of transportation management, and accelerate The role of cargo turnover, reducing the use of funds, but to design a reasonable transport packaging we must study the reliability of the transport packaging of goods.
1 Product Transportation Packaging Reliability Overview
The reliability of general products is divided into inherent reliability and use reliability. Inherent reliability refers to the reliability index that the product determines in the design stage, and is determined in the production stage, and is the attribute that the product itself has; the use of reliability refers to The actual reliability of the product during use. However, many cabinets have been damaged during transport, storage and transportation, so the product should also consider a packaging reliability. Packaging reliability refers to the ability of packaging to fulfill specified functions under specified conditions and within a specified period of time. Therefore, packaging reliability and general reliability have the same point, that is, they need to complete the prescribed functions. At the same time, packaging reliability is different from general reliability. The focus of general reliability is the product itself, and the focus of packaging reliability is not only the packaging itself, but more emphasis is placed on the safety and reliability of packaging products. Packaging reliability should involve the impact of all environmental factors such as impact, vibration, wind and sun exposure during the circulation process. However, the research on such reliability has become too complicated. However, due to impact and fatigue caused by product damage in the logistics process is the most direct and serious problem of product damage, so the main research is the dynamic reliability of product packaging.
2 Overview of Packaging Power Reliability Research
2.1 Product crispness
To quantitatively analyze the reliability of product packaging power, we must first determine the fragility or breakage boundary curve of the product, and the most straightforward way to obtain the product's fragility is to conduct the product's fragility test (using the product as the target, and determine its strength and resistance The ability to break through the experimental product to determine the product boundary damage curve, the product's fragile value), but for some large expensive or dangerous products, this destructive experiment is not suitable, so first consider how not to It is necessary to obtain the fragility of the product or destroy the boundary curve in the case of destructive experiments. At present, most of the energy analysis methods and energy methods try to open up a new way for the reliability analysis of the complex nonlinear buffer packaging system under the vibration. SARaper, RH Harkdd proposed a preliminary study of the application and packaging of statistical energy analysis.
Statistical energy analysis processes the modal parameters of complex structural dynamical systems into random variables, and predicts the response levels of various subsystems from the perspective of statistics. Now, through this analysis method, which subsystem in the product can be predicted It is the weakest link, and then evaluates its fragility.
2.2 Packaging Power Reliability in Different Failure Modes
Although there are many factors that affect the reliability of product packaging power, shock and vibration are two of the most important factors, so there are two kinds of product failure modes. A headed super-damaging mode can also be called peak failure mode. This failure mode is mainly caused when the maximum acceleration of the product during impact is greater than the fragility of the key components of the product, and at the same time, if the product structure system resonates during the vibration process, When the transmission rate reaches a maximum value, the failure mode is also generated when the acceleration transmitted to the key component exceeds the self-cracking value. The other is the fatigue failure mode, which is mainly due to the damage caused by random vibrations. Because the response takes longer than a certain amplitude, the accumulated effect exceeds the fatigue strength of a certain part of the product. For the calculation of the first super damage reliability, Song Baofeng proposed a new concept of “generalized impact load†and a definition of the reliability of industrial packaging power reliability. In 2000, Song Baofeng calculated the time history of response acceleration on a packaged product to meet the Gaussian process at any time, and based on the declaration formula of packaging reliability, the calculation formula of packaged power reliability was obtained. The calculation of the reliability of fatigue failure is not the same as the damage situation when the packaging system is subjected to random excitation and the damage situation when the packaging system is subjected to shock or harmonic excitation. Therefore, random vibration theory must be used for analysis and testing. In 1999, Jin Yuming proposed using the linear damage accumulation theory to calculate the random and random vibration fatigue of the two-degree-of-freedom packaging system according to the damage criteria, and estimated the fatigue life and remaining life of vulnerable parts. According to the calculation formula, there is a direct link between the reliability of the packaging power of the product and the transportation time, the crisp value of the product, and the transportation conditions. In 2001, Sun Yong et al. studied the problem of the failure of the buffer packaging system due to the cumulative effect of random alternating stress when the nonlinear buffered packaging system is subjected to random excitation.
2.3 Simulation of Package Power Reliability
In terms of simulation, in 2000, Huang Daomin, Yang Zhonglin and others established the dynamic model of the buffer packaging system, listed the system's differential agenda under vibration and drop, and used Matlab to perform differential transformation on the basis of Laplace transform. /Simulink dynamic simulation tool to simulate the dynamic characteristics of the package under various excitations and drop processes. In 2002, Liu Cheng et al. applied a finite element method to simulate the vibration characteristics of a computer host during transportation. And Jiang Hongkai and Tian Hongbo have made simulation calculations on the strength and reliability of missile tanks under random loads. Through establishing the cumulative damage model of missile tank strength, Miner's linear cumulative damage criterion and direct simulation method are used to simulate stress and missile tank initialization at random. Strength to gain the reliability of missile tanks.
3 Research directions and issues to consider
3.1 Model Research Needs Improvement
It can be seen from the above that the models currently studied are mostly single-degree-of-freedom or two-degree-of-freedom linear packaging models. In reality, product packaging systems are all multi-degree-of-freedom nonlinear systems, if forced to simplify single-degree-of-freedom systems or two degrees of freedom. The system may cause large errors, and most of the buffer packaging materials used at the same time are also non-linear, so the random vibration response and reliability of the multi-degree-of-freedom nonlinear product package model need further study, especially for many There are still many gaps in the theory of average energy method and its application in the degree of freedom of nonlinear systems.
3.2 Combining Analog Technology with Computer Analysis
Although the product crispness test is very important for the scientific design of product packaging, its destructiveness and cost make many product manufacturers daunting. In the current economic tide, there are more and more varieties of products on the market, and the speed of update is getting faster and faster. Product manufacturers are more willing to invest limited funds in the research of new products. Packaging is only an aid for them. The May Day. Therefore, product manufacturers generally do not attach much importance to packaging, preferring not to evaluate the fragility of their products, and adopting other unscientific methods such as analogy, empirical methods, and drop tests to design product packaging. Due to the unscientific nature of this packaging design, the product cannot be reasonably and effectively protected, and the economic loss it brings to China is as much as several billion yuan each year. Although simulation technology is not only a tool for predicting product fragility, but it also provides the development of a new buffer assessment technology, this method is still in a preliminary stage of research. How to make it more accurate and accurate Brittleness and buffer design also require more in-depth analysis.
At the same time, it can be predicted that the simulation simulation technology will bring new development to the buffer packaging test design, and the computer-aided analysis will be the future development direction of the buffer packaging test design. Simulation, also called simulation, is a model-based activity. It consists of: Establishing a simulation model - Experimenting with the model (behavior generation) - Analyze and process the model's behavior resulting from the experiment. The biggest advantages of simulation are economy and safety. The finite element method is a powerful tool for engineering numerical analysis, especially in the field of solid mechanics and structural analysis. Combining the characteristics of computer simulation technology and the finite element method, it is possible to analyze the acceleration response of any part of a product when it is subjected to arbitrary excitation.
4 Application of Package Power Reliability
The analysis of the dynamic reliability of complex goods transport packaging is to design a reasonable transport packaging. Because commodity packaging should adapt to the reproduction of social commodities and ensure the transfer of goods from production to consumption, it can be considered that rational commodity packaging can adapt to and overcome various obstacles in the circulation and sales process, and is the best package within the limit cost range. . The rationalization of commodity packaging is the ultimate goal of commodity packaging pursuit, and it is an effective means to reduce logistics costs and resolve logistics failures.
The reliability of packaging power is related to the fragility of products, the length of transportation time, and the conditions of transportation environment. Different packaging product reliability values ​​can be obtained through different product fragility values. The greater the fragility of the product, the greater the packaging reliability, but it may require more costs, so the higher the reliability, the better. Reasonable reliability, this value can reach the optimal cost of the product itself and transportation costs. In order to prevent the process of product modification and buffer packaging design from being repeated, it is necessary to specify the best reliability index at the product design stage, determine the fragility of the product based on the reliability index, and finally at the end of the product's fragility and the prescribed transport reliability. Based on the transportation environment and transportation time, the buffer packaging design is carried out to achieve optimal results. After introducing the concept of buffer packaging failure probability, reliability index, and state function, Wang Zhiwei proposed a buffer packaging probability design method based on probability theory, and put forward the concept of optimal buffer packaging to provide the most economical and appropriate buffer packaging method. It provides a theoretical basis for the most economical and optimum buffer packaging design.
Therefore, the reliability of packaging power is one of the methods for evaluating product reliability, and is one of the reference factors for product design. The most important thing is that it is the prerequisite for the optimal design of product buffer packaging.
5 Conclusion
As far as the world is concerned, the development trend of commodity transport packaging is: the general adoption of collective packaging, the standardization of transport packaging is highly valued, and the optimal design of rational packaging is carried out. The optimization design is inseparable from the analysis of the product packaging reliability. In fact, the packaging reliability is quite complicated. The power reliability of the single analysis packaging is not enough. If you want to consider various transportation environments, you can use the method of fuzzy mathematics. Analyze and evaluate the comprehensive reliability of product packaging. Based on this, we can design truly optimized product packaging. (Text / Zhang Hualiang Gu Zuli Jin Guobin)