Critical Plane Analysis of Rubber
Durability is an essential feature of most elastomer products, directly linked to safety and to perceptions of brand quality. Product designers must therefore consider the impact on product durability of typical and abusive end-user loading scenarios. Thi
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Critical Plane Analysis of Rubber W. V. Mars
Contents 1 Introduction 2 The Critical Plane Method 2.1 Critical Plane Selection 2.2 Multiaxial Criterion 2.3 Damage Evolution Law 2.4 Strain Crystallization Law 3 Incremental Procedure 4 Managing Lengthy Loading Signals 5 Some Applications 5.1 Critical Plane Analysis of Nonrelaxing Simple Tension 5.2 Incremental Analysis of Sequence Effects 5.3 Transmission Mount 5.4 Tire Durability Testing 6 Future Developments 7 Conclusion References
Abstract Durability is an essential feature of most elastomer products, directly linked to safety and to perceptions of brand quality. Product designers must therefore consider the impact on product durability of typical and abusive end-user loading scenarios. This can be accomplished using critical plane analysis (CPA). CPA starts by acknowledging that a small crack precursor might exist at any point in a part, and in any orientation, and that the potential development of all crack precursors must be evaluated. The analysis produces a full accounting of which location and orientation maximizes crack growth (or, equivalently, minimizes fatigue life) at each point, the energy release rate history experienced, and of course the worst-case fatigue life across all possible orientations. This review provides an account of the development
W. V. Mars (*) Endurica LLC, Findlay, OH, USA e-mail: [email protected]
W. V. Mars
of the method over the last two decades and the validation case that has accumulated. This review also suggests directions for further development of the method. Keyword Damage · Durability · Fatigue life · Multiaxial
1 Introduction The growth of cracks is often the chief limiter of a product’s useful life [1, 2]. Product designers must therefore make allowance via their selections of material, design, and loads for a sufficient margin between the demands of a given application and the capacity of the product to resist crack growth. Given that microscopic crack precursors exist [3–5] at nearly every point in a rubber part, and that they may have any orientation, a thorough analysis is required of a product’s use and abuse in order to ensure adequate durability. The growth of crack precursors is driven by the load inputs to a part. Load inputs may come from one direction or from several. They may be steady with a constant amplitude or random with variable amplitudes. The required analysis must account for how loading inputs to the part are experienced by each possible crack at each possible point of failure in a part, as well as the rate at which each possible crack grows. Implementing such an analysis for practical use requires the computational resources of a sufficient computer, as well as fatigue solver software that is properly formulated to embody the many details and physical effects that come into play. In this review, we shall take for granted that the computer is sufficiently powerful, and we shall focus on a specific calculation framework: critical plane analysis (CPA).
2 The Critical Plane Method Critical plane m
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