Christopher Berry

Energy method for modelling delamination buckling in geometrically constrained systems

Abstract Delamination buckling analysis of laminates is of considerable interest to the mechanical and materials engineering sectors, as well as having wider applications in geology and civil engineering. With advances in computing power, the ability to model ever increasingly complex problems at more detailed levels becomes more of a reality. However, many of the common finite element packages, with the exception of all but the most specialized, do not perform particularly well where complex non-linear problems are dealt with. In many cases, these packages can fail to determine the full range of solutions or accurately predict the properties and geometry of the final state. This is particularly the case where large deformations and buckling of laminates are considered. Because of this, many researchers prefer to use what they perceive to be more reliable techniques, such as the symbolic computation of the underlying differential equations, rather than finite element approaches. The use of finite element packages is further frustrated by the steep learning curve and implicit restrictions imposed by using third-party software. In this paper, a finite element approach and an energy formulation method are considered and used to model the delamination buckling in a geometrically constrained system. These methods are compared with experimental results and their relative merits are discussed. In particular, the accuracy and the ability to represent the geometry of the buckled system are discussed. Both the finite element approach and the energy formulation are described in detail and the numerical results are compared.

An energy-based approach for modelling the behaviour of packaging material during processing

Abstract This paper deals with the investigation of improved methods for considering machine-material interaction during the design and production of packaging machinery. Minimum energy principles are used to create a theoretical model of the response of the packaging material during processing. The complex non-linear properties of the packaging material are encapsulated in parametric models generated through analysis of the physical measurement of the changing properties during processing. These two techniques are incorporated into a software model that represents the behaviour of a skillet during the erection process. This software model considers the material, the pack design and the machine system. The overall modelling approach is validated by comparison with a physical system, which shows a good correlation with the theoretical model.

Finite element simulation of folding carton erection failure

Abstract In response to recent European Union (EU) regulations on packaging waste, the packaging industry requires greater fundamental understanding of the machine-material interactions that take place during packaging operations. Such an understanding is necessary to handle thinner lighter-weight materials, specify the material properties required for successful processing and design right-first-time machinery. The folding carton industry, in particular, has been affected by the new legislation and needs to realize the potential of computational tools for simulating the behaviour of packaging materials and generating the necessary understanding. This paper describes the creation and validation of a detailed finite element model of a carton during a common packaging operation. The model is applied here to address the problem of carton buckling. The carton was modelled using a linear elastic material definition with non-linear crease behaviour. Air inrush suction, which is believed to cause buckling, was quantified experimentally and incorporated using contact damping interactions. The results of the simulation are validated against high-speed video of carton production. The model successfully predicts the pattern of deformation of the carton during buckling and its increasing magnitude with production rate. The model can be applied to study the effects of variation in material properties, pack properties and machine settings. Such studies will improve responsiveness to change and will ultimately allow end-users to use thinner, lighter-weight materials in accordance with the EU regulations.

Simulating the behaviour of folded cartons during complex packing operations

Abstract The folding carton is a widely used packaging solution. Recent European Union packaging legislation has forced carton manufacturers to use lighter-weight grades of carton board. This typically results in a reduction in board stiffness, which can lead to decreased process efficacy or even prevent successful processing. In order to overcome this, end-users lower production rates and fine-tune packaging machine settings for each pack and material. This trial-and-error approach is necessary because the rules relating machine set-up to pack design and material properties are not generally well known. The present study addresses this fundamental issue through the creation of a finite-element computer simulation of carton processing. Mechanical testing was performed to ascertain the key mechanical properties of the carton walls and creases. The carton model was validated against the experimental results and was then subjected to the machine-material interactions that take place during complex packaging operations. The overall approach was validated and the simulation showed good agreement with the physical system. The results of the simulation can be used to determine guidelines relating machine set-up criteria to carton properties. This will improve responsiveness to change and will ultimately allow end-users to process thinner lighter-weight materials more effectively.

The performance envelope of forming shoulders and implications for design and manufacture

Abstract The production of packaging machinery is a highly competitive global market driven by the ever-increasing demands of customers and legislation. The fundamental design principles of many packaging machines are the result of incremental improvements made over the last few decades. This paper looks at the underlying theory for forming shoulders and, starting with previously published results, determines the performance envelope relating to certain critical parameters. The findings are discussed in the light of their relevance for the creation of new designs.

Numerical optimization approach to modelling delamination and buckling of geometrically constrained structures

Understanding what happens in terms of delamination during buckling of laminate materials is of importance across a range of engineering sectors. Normally concern is that the strength of the material is not significantly impaired. Carton-board is a material with a laminate structure and, in the initial creation of carton nets, the board is creased in order to weaken the structure. This means that when the carton is eventually folded into its three-dimensional form, correct folding occurs along the weakened crease lines. Understanding what happens during creasing and folding is made difficult by the nonlinear nature of the material properties. This paper considers a simplified approach which extends the idea of minimizing internal energy so that the effects of delamination can be handled. This allows a simulation which reproduces the form of buckling–delamination observed in practice and the form of the torque–rotation relation.

Understanding Machine-Material Interaction for Improved Design Methods

Market price demands and legislation are forcing fast-moving consumer goods manufacturers to use thinner and lighter weight packaging materials to convey their products to the consumer. In general these thinner, lighter materials, and materials containing high levels of recycled substrate perform less well on the present designs of packaging machinery. This problem is further complicated by the fact that customers are demanding improved operating efficiencies and expect machines to be able to handle an increasing number of product types and pack sizes. The packaging machinery manufacturers are therefore looking to develop machinery that is more flexible and responsive to changes in material properties as well as better matching new materials to current processes and specific machine designs. In order to achieve this, a fundamental understanding of the interaction between machine systems and the packaging materials used on them is required. This paper presents a design methodology which supports the identification and consideration of the machine-material interactions, and the assessment of the impact of these interactions on the process performance and the machine capabilities. From this assessment, a set of design rules for the particular packaging operation and class of packaging material can be generated. These design rules can be used to support the design of responsive packaging machines, or to reverse engineer package design (shape and size) and material specification for improved processibility.