Testing frequency

Fatigue tests were performed under load control mode on a Schenck horizontal fatigue testing machine with hydraulic grips and a maximum load capacity of 25 kN. Tension-tension constant amplitude fatigue tests were carried out at three stress levels 60% a , 70% Cu and 80% a at two different stress ratios R = 0.1 and R = 0.5. The test frequency was kept constant (f = 3 Hz) for all the tests. 

Three different specimens are considered here. Penetration depths range from 0.7 mm for aluminium to 0.15 mm for the steel block. For the experimental test frequencies used the electromagnetic skin depth is much smaller than the depth of the cracks for all the measurement considered. 

The sample frequency of the ADC (analogue to digital converter) should be 8 times higher than the test frequency (centre frequency of the spectrum). In dependence of the application, different ADC- boards are used. A standard board (20520) provides 8 bit resolution and up to 100 Msamples/s in single shot mode. For manual tests, up to 400 Msamples/s can be reached in the repetition mode. For scanning systems with high frequencies boards up to 400 Msamples/s (single shot) are available. 

The HILL-SCAN 304INF board is optimized for low test frequencies so that materials with high sound damping such as concrete can be sueeessfully inspeeted by the echo technique. 

The echo directivity was influenced by the test frequency, the angle of refraction (the velocity in the wedge and the incident angle), and the height of the transducer. 

When a test run is performed using the actual materials for the toll, it is a prime opportunity for the toller and the client to document the capability of the equipment, instrumentation, and process steps. During such a test, frequency of sampling may be increased, additional analyses performed and yield capabilities checked to find the optimum setpoints and timing for the toll process. Health, safety and environmental staff may choose to provide close coverage of the test run to evaluate areas for improvement during the actual startup and long term operation. 

The electrical properties will also depend on the above factors as well as on the test conditions, in particular temperature, test frequency and humidity. Table 26.12 quotes ranges for figures quoted in the literature for various electrical properties. 

This represents the locus of all the combinations of Ca and Om which cause fatigue failure in a particular number of cycles, N. For plastics the picture is slightly different from that observed in metals. Over the region WX the behaviour is similar in that as the mean stress increases, the stress amplitude must be decreased to cause failure in the same number of cycles. Over the region YZ, however, the mean stress is so large that creep rupture failures are dominant. Point Z may be obtained from creep rupture data at a time equal to that necessary to give (V cycles at the test frequency. It should be realised that, depending on the level of mean stress, different phenomena may be the cause of failure. 

The mean time to failure of various instrumentation and equipment parts would be known from the manufacturer s data or the employer s experience with the parts, which then influence inspection and testing frequency and associated procedures. Also, applicable codes and standards—such as the National Board Inspection Code, or those from the American Society for Testing and Materials, American Petroleum Institute, National Fire Protection Association, American National Standards Institute, American Society of Mechanical Engineers, and other groups—provide information to help establish an effective testing and inspection frequency, as well as appropriate methodologies. 

Inspections and tests are performed on the process equipment following recognized and accepted engineering practices. The inspection and test frequency is consistent with manufacturers recommendations, good engineering practices, and prior operating experience. 

Unavailability due to maintenance and testing Frequency and length of test and maintenance Maintenance report , control room Joe. l eriiHln test procedures... 

Hearing threshold level (HTL) The lowest level at which a person can detect a sound or tone. Test frequencies used to establish HTLs include 500, 1000, 2000, 3000, 4000, and 6000 Hz. 

Fig. 3.1. Young s moduli E of the polymers A, B, C, D in the rubbery state against absolute temperature T (test frequency 0.01 Hz). Entropic elasticity is indicated by the proportionality of E to T [11]...

Dynamic shear moduli are conveniently determined with automated equipment, for instance, with the torsion pendulum. However, moduli derived from dynamic tests are often higher than the results from static tests for lack of relaxation. Examples are shown in Table 3.3. Young s moduli of the polymers A, B, C, D, derived from tensile tests (frequency 0.01 Hz) are compared with shear moduli S determined with the torsion pendulum (frequency > 1 Hz). For rubberlike materials is 3S/E = 1, according to Eq. 

Dynamic mechanical measurements for elastomers that cover wide ranges of frequency and temperature are rather scarce. Payne and Scott [12] carried out extensive measurements of /a and /x" for unvulcanized natural mbber as a function of test frequency (Figure 1.8). He showed that the experimental relations at different temperatures could be superposed to yield master curves, as shown in Figure 1.9, using the WLF frequency-temperature equivalence, Equation 1.11. The same shift factors, log Ox. were used for both experimental quantities, /x and /x". Successful superposition in both cases confirms that the dependence of the viscoelastic properties of rubber on frequency and temperature arises from changes in the rate of Brownian motion of molecular segments with temperature. 

In agreement with observations previously made, recalculated data offer an overall picmre of processing effects along the mixing line. As can be seen, the expected effect of test frequency is observed, except on TR sample, but the most significant observations are made on run 2 data, which... 

Along the mixing line, significant changes occur on Q1/Q2. At dump, data are scattered and there is little, if any, effect of the test frequency. After curatives addition, the test frequency significantly affects the Q1/Q2 signature, as expected since quarter cycle integration provides all-inclusive parameters (i.e., main torque component and all harmonics). One notes also a net strain history effect, i.e., run 1 and mn 2 data do not superimpose. 

Table 11.1. Performance Attributes for HPLC Modules and Test Frequency...

PQ should be performed on a daily basis or whenever the instrument is used. The test frequency not only depends on the stability of the equipment but on everything in the system that may contribute to the results. For a liquid chromatograph, this may be the chromatographic column or a detector s lamp. The test criteria and frequency should be determined during the development and validation of the analytical method. 

Figure 5. Fatigue life as a function of sulfur content for a sand-asphalt-sulfur mix. Test temperature 50°F (10°C). Test frequency 60 Hz. Materials medium-coarse sandt and 150/180 pen. asphalt. Asphalt content 6% wt (15),...

Rigid fixtures which simulate the mounting of the fuze in service shall be used to mount the fuze to the vibration machine. The control accelerometer or accelerometers shall be mounted as close as possible to the fuze mounting point. The fixture shall be designed such that the trans-missibility at any point on the fixture shall be less than two (2). The transverse motion of the input monitoring points shall be less than 100 percent of the input motion. The transmissi-bility and transverse motion of the fixture, loaded with fuzes or dummy equivalents, shall be evaluated thru the ratnge of test frequencies... 

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