Testing ASTM impact test specimen

ASTM standard specimens and procedures were used for flexure (D-690), compression (D 695), Izod impact and torsional pendulum analysis (TPA). For tension, D1822 tensile impact specimens were substituted for D638 specimens to conserve material. Test specimens were machined from the plates and cylinders using a water cooled dlamond wheel. All the specimens were dried in vacuo at 100°C for three weeks before testing or subsequent postcure treatment. Half the specimens were post-cured for 2 hours at 225°C in vacuo before testing. Selected specimens were Immersed in distilled water at 80°C for 6 weeks for moisture uptake determinations. 

This test method was proposed by Senbetta16. Its original purpose was to evaluate the impact resistance of floor materials in terms of the capacity to resist surface disintegration due to repetitive low level impact. Instead of floor materials, this test was employed to measure the influence of plastic fillers on the concrete resistance to repetitive low impact. The specimens which were used in the test were nine 2-in. (50-mm) concrete cubes made with mix No. 2. The test uses the Los Angeles (LA) abrasion machine, which is traditionally utihzed to test aggregates according to ASTM C 131 and C 535 specifications. 

Mechanical tests were carried out in a laboratory where the temperature was maintained at 25°C using a Universal Testing Machine, LR-50 K (LLOYD Instrument, England) at a crosshead speed of 50 mm/min and 98 mm as gauge length. Stress at break, strain at break, work of rupture, and initial modulus were determined as per ASTM standards. Izod notched impact test specimens were... 

The ASTM test follows the same principles but differs in certain details. The standard test specimen is based on imperial units, so that the preferred test piece is 127 mm long by 12.7 mm wide by a thickness of 12.7. 6.4, or 3.2 mm. The details of the apparatus used are the same as for the Izod test, which is covered in the nc.xi section but the form of expressing the result is different, being based on the energy normalized with respect to the length of the notch only, and not on the area behind the notch. This only serves to add to the difficulty in making comparisons between data obtained by the ASTM standard, with its dilTcrcnt test piece sizes and impact conditions, to that of the ISO standard. 

There are various methods for performing this test. In the ASTM standard, a specimen comprised of a loop of film is subjected to a hammer impact load. The test is repeated over a series of temperatures and the impacted specimens are examined visually to determine the temperature below which failure occurs in a brittle mode. Another type of test, which evaluates brittleness temperature in a similar manner, utilizes a specimen of film that is clamped onto a table over an oval opening and inflated with air until failure. Because of the shape of the opening, this is known as a racetrack test. 

Reconstitution techniques to machine specimens from pre-tested broken specimens make it possible to generate new surveillance test data. Charpy impact specimens and fracture toughness test specimens can be reconstituted by methods such as the ASTM E1753, Standard Guide for Reconstitution of Irradiated Charpy-sized Specimens, and JEAC 4201, Method of Surveillance Tests for Structural Materials of Nuclear Reactors. 

Charpy impact test n. A destructive test (ASTM D 256B) of impact resistance using a centrally notched test specimen 126 mm long and typically 12.7 mm... 

Driers drop-weight test (falling-weight test) n. Any test of impact resistance in which known weights are dropped once or repeatedly on the test specimen. Examples are ASTM D 4272 (plastic films), D 3029, D 4226, and D 4495 (rigid PVC sheet and parts), and F 736, Section 15 (polycarbonate sheet). 

Impact resistance n. ( ) Ability of a coating to resist a sudden blow. Ability to resist deformation from impact. (2) The relative durability of plastics article to fracture under stresses apphed at high speeds. A widely used ASTM impact test, www.astm.org, employs the Izod pendulum striker swung from a fixed height to strike a specimen in the form of a notched bar mounted vertically as a cantilever beam. The Charpy tester, an alternative in D 256, uses a specimen in the form of a horizontal beam supported at both ends. ASTM lists some several different impact tests for plastics and plastics products. 

Tensile-impact test n. An impact test that uses a pendulum striker to break a dog-bone-shaped test specimen, described in ASTM D 1822 and 1822M. It differs from the Izod impact test in two important aspects (1) the specimen is not notched and (2) it is broken in simple tension rather than bending. For these reasons, its interpretation is more straightforward. 

Figure 11.8 Dimensions of Charpy impact test specimen (ASTM D 256-97).

It is worth noting that ISO/IEC and ASTM test methods for many properties, in principle, are similar and the differences between the specific test methods are rather minimal. Even so, differences in measured data between the two methods, depending on the type of material, are expected, particularly with thickness-dependent properties such as impact strength, DTUL, and flexural properties stemming from the variance in test specimen dimensions and its preparation. Thus, any correlation between two sets of data is dependent on the material type, implying that one should not assume that the property values generated by the ISO test methods would always be equivalent to the values obtained by using the ASTM method with simple conversion to appropriate units. 

The chip impact test is carried out in a similar way to the Izod test but without a notch. The test specimen is usually 25.4 mm long, 12.7 mm wide, and 1.65 mm thick. The tests are carried out using ASTM D4508 [79]. Because the test involves an un-notched sample, it reflects material toughness rather than the notch sensitivity measured for the Izod and Charpy tests. 

Drop weight, standard and precracked Charpy impact, tensile test, and compact tension fracture toughness specimens are provided for unirradiated tests. Drop weight tests will be conducted in accordance with ASTM E-208. Charpy impact tests will be conducted in accordance with AGTM E-23. Tensile tests are conducted in accordance with ASTM E-8 and E-21. Correlation of drop weight and Charpy impact tests to establish will be made in accordance with NB2300 of the ASME Code, Section III. Charpy impact and tensile test specimens are provided for post-irradiation tests. 

Tensile test, standard and precracked Charpy impact and l/2t compact tension test specimens are used for determining changes in the strength and static and dynamic toughness properties of the materials due to neutron irradiation. A total of 333 standard Charpy impact, 81 precracked Charpy impact, 60 l/2t compact tension and 36 tensile test specimens are provided. The type and quantity of tests specimens provided for establishing the properties of irradiated materials over the lifetime of the vessel are presented in Table 5.3-3. Compact tension specimens provided for capsule irradiation are precracked prior to insertion to reduce the time required for post irradiation testing. The types and quantity of specimens provided exceed the minimum requirements of ASTM E-185-82. 

ASTM G 73, Practice for Liquid Impingement Erosion Testing—The behavior of solid specimens that are exposed to discrete impacts of liquid may be evaluated by conducting studies according to this standard. Specimens are subjected to hquid sprays or jets and the weight loss (or other metal loss data) is recorded with exposure time. This method presents test apparatus, test specimens, test procedures, and calculations and analysis of erosion resistance. 

Each of the fillers in both surface modified and as received condition was mixed with polypropylene and then dried at 110 C for 30 minutes just prior to molding. Tensile, flexure, and impact samples were molded using an injection molder. Test specimens were conditioned for a minimum of 72 hours at 23°C and 50% RH prior to testing. All physical property evaluations were conducted in accordance with appropriate ASTM testing procedures. 

Charpy Impact Test n A destructive test (ASTM D 256B) of impact resistance using a centrally notched test specimen 126 mm long and typically 12.7 mm. The specimen is supported horizontally near its ends and struck on the side opposite the notch by a pendulum, having sufficient kinetic energy to break the specimen with one blow. The result is expressed as the quotient of the energy absorbed from the pendulum divided by the specimen width (J/cm or ft-lb/in). 

The fractional return, to an impacting hody, of the energy with which it strikes a resilient test specimen. ASTM D 1054 details a pendulum-rehound test, while D 2632 and D 3574 describe drop-weight-rebound tests, all employing this principle and all in section 09.01. 

The fracture toughness of the laminate material can be measured by a number of methods, some of which are shown in Fig. 4.32. The results will vary with different layup orientations. Other methods may be similar to the test specimens shown in ASTM-E-399 and may involve impact. Presently, the most widely accepted technique for evaluating the fracture toughness of a laminate or structure is a compression test after impact. Compression is a valid indicator without matrix support, the fibers will buckle, while the fibers do not need as much matrix support for tensile loading. 

Figure 7.25 Impact test specimen and holding fixture. (From ASTM D 950)...

The DWT procedure is given in ASTM E-208 and consists of welding a brittle bead on a test specimen. The bead is then notched and the specimen impact tested at various temperatures. The NDT temperature is obtained when the specimen does not break upon impact. 

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