Types of Strength

The stress systems in such tests are complex, and not easily related to fundamental properdes. But the results are relevant to the performance of materials in service, and for that reason, flexural tests are frequently used in engineering practice. 

Certain materials may be weak in shear, and for these it is appropriate to measure their strength by torsion tests. For such tests, the material is fabricated into a rod of circular cross-section, and twisted about its longitudinal axis. The angle of twist is proportional to the shearing strain, y, and the applied force or couple is proportional to the shearing stress, r, their ratio being defined as the shear stress, G, i.e. 

In addition to the strength tests already mentioned, there are 

There is no single answer to the question how strong is this material . The answer depends on which particular test of strength has been applied. For 

In addition to the strength tests already mentioned, there are other tests which can be applied and which at first sight give an indication of strength. These include hardness and fatigue tests. In reality all of these tests measure different physical attributes of the material and for a truly comprehensive picture of the behaviour of any material, results from all of these types of test should be known. 

---

This second group of tests is designed to measure the mechanical response of a substance to applied vibrational loads or strains. Both temperature and frequency can be varied, and thus contribute to the information that these tests can provide. There are a number of such tests, of which the major ones are probably the torsion pendulum and dynamic mechanical thermal analysis (DMTA). The underlying principles of these dynamic tests have been covered earlier. Such tests are used as relatively rapid methods of characterisation and evaluation of viscoelastic polymers, including the measurement of T, the study of the curing characteristics of thermosets, and the study of polymer blends and their compatibility. They can be used in essentially non-destructive modes and, unlike the majority of measurements made in non-dynamic tests, they yield data on continuous properties of polymeric materials, rather than discontinuous ones, as are any of the types of strength which are measured routinely. 

AB cements tend to be essentially brittle materials. This means that when subjected to mechanical loading, they tend to rupture suddenly with minimal deformation. There are a number of different types of strength which have been identified and have been determined for AB cements. These include compressive, tensile and flexural strengths. Which one is determined depends on the direction in which the fracturing force is applied. For full characterization, it is necessary to evaluate all of these parameters for a given material no one of them can be regarded as the sole criterion of strength. 

Figure 5.56 Design chart of modulus versus strength (see inset for type of strength determination). Reprinted, by permission, from M. F. Ashby, Materials Selection in Mechanical Design, 2nd ed., p. 42. Copyright 1999 by Michael F. Ashby.

Results of identical types of strength tests on an NC soil expressed as shear strength versus volumetric strain were fmmd to plot as a straight line parallel to the normal consolidation line. The raho of strength to consolidation pressure was constant for each particular t5qje of test, S /o = C2, where C2 is a constant dependent on the value of the OCR and the type of test. 

Figure 8.8 Brittle materials contain various types of strength-controlling flaws.

Two types of strength degradation are found during thermal shock. For materials in which crack propagation is unstable, there is a catastrophic decrease in strength at the critical temperature difference (Fig. 9.14). This effect becomes... 

Hypothesis B states that the same time-temperature superposition principle applies for all three types of strengths (CSR, creep, and fatigue). This means that the shift factors for all three types of strength can be assigned the same value. The first master curve of CSR strength can then be constructed from the test results for various constant strain rates and temperatures. 

Fig. 1.6 Types of strength testing compression, tensile, and three-point bending strength...

Minimum tensiley shear or peel strength at specified temperatures. For the most part, only one of these types of strength evaluation need be considered. There is no need for adhesives to develop strengths far in excess of the internal strength of the weaker of the materials being bonded. 

To predict the strength of adhesively bonded joints, strength criteria should be applied to the stress vales obtained by analyses. Several types of strength criteria applicable to dynamic problems are explained below. In addition, an example of an actual application is also shown in that section. 

---