Load configuration

Fig. 2. Illustrations of forces to which adhesive bonds are subjected, (a) A standard lap shear specimen where the black area shows the adhesive. The adherends are usually 25 mm wide and the lap area is 312.5 mm. The arrows show the direction of the normal apphcation of load, (b) A peel test where the loading configuration, shown by the arrows, is for a 180° peel test, (c) A double cantilever beam test specimen used in the evaluation of the resistance to crack propagation of an adhesive. The normal application of load is shown by the arrows. This load is appHed by a tensile testing machine or other...

Plastic deformation is commonly measured by measuring the strain as a function of time at a constant load and temperature. The data is usually plotted as strain versus time. Deformation strain can be measured under many possible loading configurations. Because of problems associated with the preparation and gripping of tensile specimens, plastic deformation data are often collected using bend and compression tests. 

Similar desirability factors may be derived for other geometries such as struts, columns etc. This concept is taken further later where material costs are taken into account and Tables 1.11 and 1.12 give desirability factors for a range of loading configurations and materials. 

Desirability factors for some common loading configurations... 

For convenience so far we have referred generally to creep curves in the above examples. It has been assumed that one will be using the conect curves for the particular loading configuration. In practice, creep curves obtained under tensile and flexural loading conditions are quite widely available. Obviously it is important to use the creep curves which are appropriate to the particular loading situation. Occasionally it is possible to obtain creep curves for compressive or shear loading but these are less common. 

Stress and Strain 185. Elementary Loading Configurations 188. Prediction of Failure 194. 

In the loading configuration of Figure 2-29, the beam will bend in the concave upward direction, thus putting the lowermost fiber in tension and the uppermost fiber in compression. The magnitude of this axial stress is... 

Just as the armature coils of a three-phase generator may be connected in a A or Y configuration, the circuit loads may be connected in a A or Y configuration. The A-load configuration may be supplied from a source that is connected in either A or Y. The Y connection may include a neutral (fourth) wire, connected at the common connection of the circuit. 

The policy of Standard 4D, that the manufacturer specify the structure load capacity for various loading configurations, has been applied in detail in Standards 4E (superseded by Standard 4F) and 4F. Standard 4F calls for detailed capacity ratings that allow the user to look up the rating for a specific loading configuration. These required ratings are as follows. 

A typical ETO sterilization cycle is shown in Fig. 10. As discussed at the beginning of this section, it is important to determine and monitor the bioburden level of the product entering the sterilizer. Also, the load configuration in the sterilizer is important in achieving uniform and reliable sterilization. Unfortunately, commercially available biological indicators used in ETO sterilization are often unreliable. Hopefully, progress will be made in this field in the years ahead. 

The classic way that we perform force versus deformation measurements is to deform a sample at a constant rate, while we record the force induced within it. We normally carry out such tests in one of three configurations tensile, compressive, or flexural, which are illustrated in Fig. 8.1. We can also test samples in torsion or in a combination of two or more loading configurations. For the sake of simplicity, most tests are uni-axial in nature, but we can employ bi-axial or multi-axial modes when needed,... 

Apart from the short beam shear test, which measures the interlaminar shear properties, many different specimen geometry and loading configurations are available in the literature for the translaminar or in-plane strength measurements. These include the losipescu shear test, the 45°]5 tensile test, the [10°] off-axis tensile test, the rail-shear tests, the cross-beam sandwich test and the thin-walled tube torsion test. Since the state of shear stress in the test areas of the specimens is seldom pure or uniform in most of these techniques, the results obtained are likely to be inconsistent. In addition to the above shear tests, the transverse tension test is another simple popular method to assess the bond quality of bulk composites. Some of these methods are more widely used than others due to their simplicity in specimen preparation and data reduction methodology. 

Fig, 3.20. Schemalic drawings of loading configurations of (a) losipcscu shear test and (b) asymmetric tour-point bending (AFPB) test. After losipcscu (1967) and Slcpctz ct al. (1978). 

The intent of this study is to demonstrate the temperature uniformity and stability of the sterilizing medium throughout the sterilizer. Temperature distribution studies should be conducted on both empty and loaded chambers with maximum and minimum load configurations. Temperature uniformity may be influenced by the type, size, design, and installation of the sterilizer. The manufacturer of the vessel, based on the variables mentioned, should determine a satisfactory empty chamber temperature uniformity. 

Subsequent to the empty chamber studies, maximum load temperature distribution studies should be conducted to determine if the load configuration influences the temperature distribution profile obtained from the empty chamber studies. The thermocouples utilized in the heat distribution studies are distributed geometrically in representative horizontal and vertical planes throughout the sterilizer. The geometric center and corners of the sterilizer should also be represented. An additional thermocouple should be placed in the exhaust drain adjacent to the sensor that controls vessel temperature, if possible. 

Heat penetration studies are also employed to determine points within a load configuration that achieve higher temperatures and consequently greater Fq values. The temperature data obtained may be significant when heatable products are involved in the sterilization process and the potential for product degradation exists. The cool points established for a specified load and configuration will eventually be utilized to control the exposure time in subsequent routine production runs. The temperature sensors that control sterilization-cycle-exposure time at process temperature may be positioned within the load at the previously detected cool point. Consequently the entire load is exposed to sufficient heat lethality and achieves the desired Fq value. 

Load configuration. Vial filling machine parts ... 

Load configuration (define numbers) Tyvek bags, each containing (define numbers) stoppers... 

The following load configurations have been validated on the autoclave ... 

To determine coolest points for each load configuration/size... 

This is not applicable. Because the depyrogenation tunnel is a continuous line activity, minimum and maximum load cannot be defined. The validation study simulated all possible production scenarios and load configurations. Thermocouples were distributed at the beginning of production, middle of production, and end of production. 

Changes in sterilizer load configurations that are outside the range of previously validated loads. 

Heat distribution studies for each sterilizer, each loading configuration, every container size, using a minimum of 10 thermocouples. 

Again, the minimum and maximum loading configurations should be studied. Thermocouples will be placed both inside and outside the container at the cool spot location(s), in the steam exhaust line, and in constant-temperature baths outside the chamber. The F0 value will be calculated based on the temperature recorded by the thermocouple inside the container at the coolest area of the load. Upon completion of the cycle, the F0 value will indicate whether the cycle is adequate or if alterations must be made. Following the attainment of the desired time-temperature cycle, cycles are repeated until the user is satisfied with the repeatability aspects of the cycle validation process. Statistical analysis of the F0 values achieved at each repeated cycle may be conducted to verify the consistency of the process and the confidence limits for achieving the desired F0 value. 

Any changes in the load size, load configuration, or container characteristics (volume, geometry, etc.) must be accompanied by repeat validation studies to prove that the cool spot location has not changed or, if it has, that it receives the design F0 time exposure from the sterilization cycle used. 

Three to five replicate runs for each commodity size and every loading configuration should be done using 10 to 20 thermocouples distributed throughout the load. Careful analysis of the temperature data after each ran will be... 

Endotoxin destruction should be ascertained at the coolest location of the load. Load configurations should be identical to those used in the microbial validation studies. 

This is a very extensive topic involving many variables. It involves the evaluation of the inherent compatibility between a material and the environment under applied or residual stress. Factors such as material type, process history, product form, active cracking mechanisms, loading configuration and geometry and exposure environments can have an impact on the type of sample and test conditions for the evaluation of EAC. 

Figure 11 Common types of rectangular and circular specimen holders (a) zero background, (b) top-loaded, and (c) back-loaded configurations...

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