Edge Crush Test (ECT) Definition
An edge crush test (ECT) is a testing method used to measure the durability of a corrugated board. The edge crush test (ECT) gives valuable information regarding the strength of particular board to resist crushing. Corrugate box resistance strength is measured by the edge crush test and the ability of corrugated board to resist crush is specified in edge crush test (ECT).
A Little More on What is the Edge Crush Test
The resistance of edge crush, “R”, is measured and specified in kilonewtons per meter (KN/m) and it can be calculated as following;
R = 0.01 x F¯max, where F¯max shows the average value of maximum force and is calculated in newton.
There are many material testing methods used to measure the strength of corrugated boxes. Most techniques and procedures were used to evaluate the compression and resistance strength of a box (such as regular, single wall slotted containers, empty and top to bottom) based on several characteristics.
Simplified McKee formula:
McKee published one of the empirical methods in 1963. The method used MD, CD flexural, perimeter of box and depth of box, and board edge crush test (ECT). The formula was later on simplified and it included the board ECT, box perimeter and board thickness.
The formula of McKee to calculate the value of BCT is following;
BCT = 5.876 x ECT x square root of U x d
BCT Stands for Box Compression Test in pounds,
U denotes box outline in inch,
And d denotes thickness of corrugated board in inches.
The formula used by the McKee method to estimate the value of Box Compression Test (BCT) was the most simplified but it often gives an inaccurate estimate.
Benefits of Edge Crush Test
- Box Standards – If the producer wants to determine whether the manufactured box complies with industry rules and regulations, he would perform the edge crush test.
- Strength – The edge crush test allows manufacturers to check the strength of corrugated box.
- Material testing – The edge crush test allows the manufacture to test the quality of materials used in the production of corrugated boxes.
References for Edge Crush Test
Academic Research on Edge Crush Test (ECT)
Nonlinear finite element modeling of corrugated board, Gilchrist, A. C., Suhling, J. C., & Urbanik, T. J. (1999). AMD; Vol. 231. MD; Vol. 85.: p. 101-106: ill. This paper investigates the mechanical behavior of corrugated boards using finite element analysis. The analysis was performed using the commercial nonlinear finite element code ABAQUS and executed on Sun SPARCstations and the State of Alabama Cray C90 Supercomputer. Some of the models created considered the combined board structure in detail and some of the configurations analyzed includes the four-point bending geometry, Edge Crush Test (ECT) geometry, and anticlastic bending test geometry. Results from the analysis were compared with measurements from actual corrugated specimens for evaluation purposes.
Refined nonlinear finite element models for corrugated fiberboards, Haj-Ali, R., Choi, J., Wei, B. S., Popil, R., & Schaepe, M. (2009). Composite Structures, 87(4), 321-333. The authors presented a refined nonlinear finite element technique for analyzing corrugated fiberboard material and structural systems. The model is created using the orthotropic material model with Hill’s anisotropic plasticity. The combined material and structural modeling technique involve both material and geometric nonlinear effects. The edge crush test for geometry is then performed.
The influence of pin adhesion strength on edge crush and box compression strength, Schaepe, M. (2000). This paper researches historical information about the relationship between edge crush strength (ECT), box compression strength (BCT) and pin adhesion. Field data sometimes indicate an important relationship between ECT, BCT and pin adhesion strength. Those field data are obtained from tests performed on production boxes. This paper will also present data generated at the Institute of Paper Science and Technology and explore the special circumstances that affect the relationship.
Correcting for instrumentation with corrugated fiberboard edgewise crush test theory, Urbanik, T. J. (1990). Tappi J, 24(4), 263-268. This paper integrates a theory corrugated fiberboard short column failure by buckling into a semiempirical model that explains the factors responsible for post-buckling behavior. On application, a set of post-buckling constants are obtained which may be used to rectify instrumentation differences. The values of the constants differ depending on the user’s testing method. Results are in the form of equations which predict the elastic, inelastic, or combined failure modes which can then be used to confirm or reject the accuracy of the method of testing.
The structural design of corrugated boxes for horticultural produce: A review, Pathare, P. B., & Opara, U. L. (2014). Biosystems Engineering, 125, 128-140. Corrugated boxes are used widely in the horticulture industry for transporting and storing fresh produce because the boxes prevent mechanical damages due to drops, vibration, and compression. Different experimental and modeling tools are employed to study the design and mechanical performance of packaging boxes. Some of the experimental studies on the mechanical performance of packaging boxes include compression, impact and vibration analysis.
Flexural stiffness of selected corrugated structures, Lee, M. H., & Park, J. M. (2004). Packaging Technology and Science: An International Journal, 17(5), 275-286. This research was carried out to analyze the flexural stiffness of specific corrugated fiberboards. Flexural stiffness accurately predicts top-to-bottom compression strength of boxes by measuring the bending force and bending deflection using a four‐point bending test method. The article provides major constructional factors which can improve the compression strength of a corrugated box.
The relationship between the edgewise compression strength of the corrugated board and the compression strength of liner and fluting medium papers, Dimitrov, K., & Heydenrych, M. (2009). Southern Forests, 71(3), 227-233. The main objective of this study is to create and prove predictive mathematical correlations between corrugated board and paper compression properties after their exposure to specific climatic conditions. This allows packaging technologists to pick the right paper substrates, with adequate strength characteristics, to manufacture corrugated boards with the desired compression strength for specific climatic conditions.
The use of MD shear stiffness by the torsional stiffness technique to predict corrugated board properties and box performance, Chalmers, I. R. (2007). In 61st Appita Annual Conference and Exhibition, Gold Coast, Australia 6-9 May 2007: Proceedings (p. 145). Appita Inc. A new method of measuring the machine direction (MD) shear stiffness of corrugated boards was introduced at the 2006 Appita Conference. The method is called the machine direction torsional stiffness technique (torsional stiffness=shear stiffness). This article discusses the results obtained from using the method on corrugated boards, before and after manufacture and at different levels of crush damages. The results are compared other conventional testing methods such as flat crush (FCT), thickness, edge crush (ECT) or box crush (BCT), MD torsional stiffness.
Effect of corrugated flute shape on fiberboard edgewise crush strength and bending stiffness, Urbanik, T. J. (2001). Journal of Pulp and Paper Science, 27(10), 330-335. The author models the influence of corrugated fiberboard fluting geometry on strength and stiffness and presents a new technique to optimize flute profile. The height, length, pitch, radius arc and angle of wrap of the pitch are normalized to form a set of nondimensional parameters, two of which are independent. The strength and stiffness data from fiberboard are then modeled and used to predict the average stress-strain properties of the containerboard components. The models are then used to predict theoretically how mechanical properties and material savings change for other flutes.
Packaging performance, Hägglund, R., & Carlsson, L. (2012). Mechanics of paper products, 271. Paper materials have significant use in packaging. The main reason for packaging is to smoothen the transfer of goods from producer to consumer. This paper centers on the performance requirement that determine the strength of the package. An important example of such requirements is the stacking strength during high humidity exposure. This paper also discusses the packaging and performance of corrugated boards. This paper categorizes packaging into three categories namely primary packaging, secondary packaging, and tertiary packaging. The secondary packaging carries the major load during transportation and requires a lot of strength.