Rate of loading

Load bearing capabiUties are dependent upon the adherend, joint design, rate of loading, and temperature. Values given represent the type of adherends normally used at room temperature. Lap shear values approximate those obtainable from an overlap of 3.2 cm. ... 

Compression tests, in which agglomerates ate cmshed between parallel platens, ate probably most universal. To obtain reproducible and accurate results, the rate of loading and method of load appHcation must be strictly controUed. A variety of commercial testers ate available to allow this needed control over the compression process. Several means of distributing the load uniformly at the point of contact ate used, including covering the platen... 

Viscoelastic and rate theory To aid the designer the viscoelastic and rate theories can be used to predict long-term mechanical behavior from short-term creep and relaxation data. Plastic properties are generally affected by relatively small temperature changes or changes in the rate of loading application. 

It is also possible to mn tensile tests at a constant rate of loading. If the cross-sectional area is continuously monitored and fed back into a control loop, constant-stress-rate tests can be made. In this case the initial slope... 

During the transient load phase of an accidental explosion, when the shock duration is less than the time of maximum response of the structural elements, member end rotations are limited to one degree. Maximum inelastic deformation is limited to three times the member elastic limit deflection. Since this loading phase is suddenly applied, use of material dynamic increase factors based on strain rate of loading are also used. 

The actual impact (at fall hammer velocities of 1-5 m/sec) can be considered as a pseudostatic process, ie the rate of loading is much slower than the sound velocity in either the apparatus or the compacted explosive sample... 

It is customary when evaluating plasticizers in polyvinyl chloride to compare them at concentrations which produce a standard apparent modulus in tension, as measured at room temperature. Since the stress-strain relationship is generally nonlinear it is necessary to specify a given point on the stress-strain curve as well as the rate of loading or straining. The efficiency may be expressed as the concentration of a given plasticizer necessary to produce this standaid modulus. Other properties, e g., indentation hardness, may take the place of tensile modulus. 

Details of the experimental arrangements are presented in References 1-5 and 13. The majority of the experiments reported here were performed in vacuum at pressures ranging from 10 7 to 10"9 torr. For many studies, the samples are loaded into a carousel sample holder and sequentially rotated into position for testing. Typical sample dimensions are 2x6x12 mm3. The samples are usually loaded in three point bend. The load force is usually monitored to determine the rate of loading, the force at fracture, and the time of fracture. 

In applications where possible degrading elements exist, candidate adhesives must be tested under simulated service conditions. Standard lap shear tests, such as ASTM D1002, which use a single rate of loading and a standard laboratory environment, do not yield optimal information on the service life of the joint. Important information such as the maximum load that the adhesive joint will withstand for extended periods and the degrading effects of various chemical environments are addressed by several test methods. Table 15.2 lists common ASTM environmental tests that are often reported in the literature. 

J. Lankford, Strength of Monolithic and Fiber-Reinforced Glass Ceramics at High Rates of Loading and Elevated Temperatures, Cer. Eng. Sci. Proc., 9[7-8], 843-852 (1988). 

Load type and rate of loading, velocity/duration of test ... 

At quasi-static rates of loading the effect of the rubber particle is twofold. First, the stress concentrations near the rubber particles induce... 

At high rates of loading the britttle nature of the unmodified material is manifested by the occurrence of spallation (see Figure 3). Spallation... 

Thermal-Mechanical Criteria. The thermal and mechanical properties must not be degraded. The toughness properties (crack and impact resistance) must be improved, and the system should be rather insensitive to the rate of loading (or temperature) of a given test. 

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