Solid mechanics fracture tests

H. Riedel and J. R. Rice, Tensile Cracks in Creeping Solids, in Fracture Mechanics Twelfth Conference, ASTM Technical Publication 700, ed. P. C. Paris, American Society for Testing and Materials, Philadelphia, PA, 1980, pp. 112-130. 

Applications of linear elastic fracture mechanics (primarily) to the brittle fracture of solid polymers is discussed by Professor Williams. For those not versed in the theory of fracture mechanics, this paper should serve as an excellent introduction to the subject. The basic theory is developed and several variants are then introduced to deal with weak time dependence in solid polymers. Previously unpublished calculations on failure times and craze growth are presented. Within the framework of brittle fracture mechanics and testing this paper provides for a systematic approach to the faOure of engineering plastics. 

Shear cell testing of powders has its basis in the more comprehensive field of soil mechanics (Schofield and Wroth, Critical State Soil Mechanics, McGraw-Hill, 1968), which may be further considered a subset of solid mechanics (Nadia, Theory of Flow and Fracture of Solick, vols. 1 and 2, McGraw-Hill, 1950). The most comprehensive testing of the shear and flow properties of soils is accomplished in... 

There is clearly a need to investigate the mechanism of attrition to relate it to the fracture properties of the solids, and to develop a realistic attrition index , similar to that used for abrasion in cyclones. Such an index would indicate the relative importance of operating conditions and design variables such as inlet velocity, feed solids concentration or cyclone diameter. This could then be used in scale-up to predict (or minimize) the effect of the shape, the particle size distribution or the hardness and strength of the feed solids, if known, may allow such predictions without any experimental tests. Generally, better understanding of attrition and its relation to abrasion may lead to better equipment design and operation. 

The fracture-based approach derives from continuum fracture mechanics theory, which claims the strength of most real solids is governed by flaws within the material [2]. To help predict this type of behavior, many test methods have been developed to determine fracture properties of adhesives. These tests are used to characterize the mode I, II, and III fracture properties of many types of material systems. In this study, the focus will be on the mode I and II characteristics of bonded joints for automotive applications. 

A great deal can be learned about the mechanical properties of materials by stressing them until they fracture or break. The most common mechanical test involving metals or polymers is the tensile test, in which a sample of the solid is stretched. The test uses a standard test piece with a shape dependent on the material to be tested. Metals usually have a central cylindrical section, of known gauge length. 

In a contribution from B. F. Goodrich, Drake and Siebert extensively review the journal and patent literature since 1975 on reactive butadiene/acrylonitrile liquid and solid elastomers used in formulating epoxy structural adhesives. Areas reviewed include the preparation of elastomer-modified epoxy resins, the characterization of rubber-toughened epoxy resins, fracture mechanics and adhesive formulation and testing. 

Plastics—Determination of the Fluidity of Plastics Using Capillary and Slit Die Rheometers Plastics—Determination of Fracture Toughness (Gc and Kq). Part 1 Linear Elastic Fracture Mechanics (LEFM) Approach Methods of Test for Volume Resistivity and Surface Resistivity of Solids Electrical Insulating Materials... 

As discussed in Chapter 1, fracture mechanics relies on the assumption that the materials tested behave as linearly elastic solids. Structural adhesive bonds fail by crack initiation and propagation in the adhesive layer. Assuming that the structural adhesive is brittle, then it would seem appropriate... 

Testing of cured adhesives in the bulk state has become more widespread because of increasing use of adhesives in engineered structures. Concurrently, modelling of adhesive joints has become more commonplace, and for such work, measurement of the bulk mechanical and solid fracture properties in a variety of modes is essential. Developers of adhesives are also increasingly aware that testing of cured adhesives in the bulk state can provide information relevant to their performance in bonded joints. 

A large number of test results indicate that supported metal catalysts and metal-oxides have properties similar to that of brittle materials. That is to say, basically plastic deformation does not occm before the materials fracture under external stress, and the fracture is instantaneous without any obvious forewarning. Solid catalysts are highly porous with crystal boundaries and a lot of defects, such as dislocation or discontinuities arising from the presence of promoters. They are similar to cracks, as defined in fracture mechanics, where fracture stresses are focused, eventually leading to breakup of the catalyst particles. ... 

---