| A Study of Fatigue Crack Propagation in Powder Metallurgy Hot Isotatically Pressed Nickel-Base Alloy |
28 AUG 86 |
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| Authors:
Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA DEPT OF METALLURGY AND MATERIALS ENGINEERING
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 | L.C. Astroloy contains a complex distribution of rounded cuboidal gamma prime precipitates (0.1 micrometers edge dimension), cooling gamma prime(0.01 micrometers dia) and prior particle boundary particles of MC, ZrO2, alpha-Al2O3 and M3B2; the majority of MC carbides were not found in conjunction with ZrO2 particles as was previously assumed. Delta K sub th value were found to vary with specimen geometry with lower values being associated with more symmetrical specimen ... |
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| Fatigue and Fracture Mechanics of Structural Metals, Plastics, and Composites |
18 AUG 86 |
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| Authors:
Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA
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| AFOSR/DOD-URIP funds were used to purchase an Instron computer- controlled mechanical test system for the purpose of evaluating the fatigue and fracture response of metals, plastics, and composites. The FCP Run program provided with the test system has been modified to include differing testing options (constant K sub max and constant K sub mean decreasing K threhold procedure) and incorporate stress intensity factor and compliance calibrations for several additional specimen ... |
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| Crack Propagation in Powder Metallurgy Hot Isostatically Pressed Nickel- Based Alloy |
05 MAY 85 |
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| Authors:
Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA DEPT OF METALLURGY AND MATERIALS ENGINEERING
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| The room temperature threshold fatigue behavior of P/M HIP'd L.C. Astroloy has been examined. Material with grain sizes ranging from 5 micrometers to 50 micrometers has been tested to investigate the influence of grain size on the threshold response. In disc compact tension specimens grain size is observed to have little influence on the threshold values; in contrast tests conducted in four point bend specimens exhibit lower threshold values and ... |
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| Effects of Short Glass Fibers and Particulate Fillers on Fatigue Crack Propagation in Polyamides |
DEC 1982 |
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| Authors:
Reinhold W. Lang; John A. Manson; Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA COXE LAB
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| The fatigue crack propagation (FCP) behavior (at 10 Hz) of several commercial short-glass-fiber and mineral-reinforced nylon composites has been investigated. The FCP rates can be described in terms of the well known Paris relationship. Significant improvement in FCP performance was found for the glass-fiber-reinforced materials in comparison to that of the pure matrix materials (nylon 66 and nylon 612). Also, the FCP resistance was found to increase with increasing fiber ... |
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| The Application of Infrared Microscopy in the Study of Polymer Fatigue |
DEC 1982 |
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| Authors:
M. T. Hahn; Richard W. Hertzberg; R. W. Lang; John A. Manson; J. C. Michel; LEHIGH UNIV BETHLEHEM PA COXE LAB
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| A model describing the frequency sensitivity of fatigue crack propagation (FCP) of polymers in terms of localized versus generalized specimen heating is examined. The magnitude of heating at the crack tip and across the unbroken ligament of the specimen is measured with an infrared microscope. The results confirm the earlier hypothesis regarding the observed frequency dependence of FCP behavior. (Author) |
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| Fatigue Crack Propagation in Amorphous Poly(Ethylene Terephthalate) |
DEC 1982 |
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| Authors:
Alvaro Ramirez; John A. Manson; Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA COXE LAB
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| Earlier studies of fatigue crack propagation (FCP) in polymers have shown a general superiority of crystalline relative to amorphous polymers in terms of FCP resistance. In order to study in detail the effect of crystalline content and character on FCP rates, Poly(ethylene terephthalate) (PET) was selected as a convenient material in which a wide range of crystallinity can be obtained. In order to provide a base-line for comparison, FCP rates ... |
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| Effect of Test Frequency and Water Content on Localized Crack-Tip Heating in Nylon 66 |
DEC 1982 |
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| Authors:
M. T. Hahn; Richard W. Hertzberg; John A. Manson; Reinhold W. Lang; P. E. Bretz; LEHIGH UNIV BETHLEHEM PA COXE LAB
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| Fatigue crack propagation (FCP) tests were conducted on nylon 66 specimens equilibrated over a range of moisture levels and test frequencies to determine the crack growth rates and the crack-tip temperatures as a function of water content. Frequency-sensitivity was correlated with the amount of crack-tip heating taking place, with crack-tip temperature being found to depend strongly on the estimated loss compliance, D', of the material. The frequency-sensitivity of FCP in ... |
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| Effect of Frequency on Fatigue Crack Propagation in Short-Glass-Fiber- Reinforced Nylon 66 |
DEC 1982 |
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| Authors:
Reinhold W. Lang; John A. Manson; Richard W. Hertzberg; LEHIGH UNIV BETHLEHEM PA COXE LAB
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| The fatigue crack propagation (FCP) response of nylon 66 and composites containing 16 and 31 vol. % short glass fibers was determined at frequencies of 1, 10, 50, and 100 Hz. The sensitivity to frequency was found to depend on glass content and, in the case of the pure matrix, on the value of the stress intensity factor range, delta K. Whereas both glass-reinforced compositions were superior to the pure ... |
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| A Correlation between Crack Growth Rate and Fracture Mode Transitions in Low-Density Polyethylene. |
30 JAN 1981 |
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| Authors:
Philip E. Bretz; Richard W. Hertzberg; John A. Mason; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| Fatigue crack propagation rates in low-density polyethylene as a function of stress intensity factor were found to exhibit a discontinuity in the range Delta K = 0.4-0.6 MPa Zeta m. Within this range the FCP rate decreased with increasing Delta K. Fractographic examination revealed significant differences in the appearance of the fracture surfaces corresponding to values of Delta K below and above the transition range. While the reason for this ... |
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| Mechanisms of Fatigue Damage and Fracture in Semi-Crystalline Polymers. |
30 JAN 1981 |
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| Authors:
Philip E. Bretz; Richard W. Hertzberg; John A. Mason; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| Fatigue crack profiles and fracture surfaces of poly(vinylidene fluoride) (PVDF), nylon 66 (N66), and poly acetal (PA) were studied to ascertain the mechanisms of cyclic damage and fatigue crack propagation in semi-crystalline polymers. Crack tip damage is believed to begin as small trans-spherulitic and interspherulitic tensile crazes. However, compressive yielding within the reverse plastic zone at the crack tip crushes and elongates the spherulities in the direction of crack growth. ... |
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| The Influence of Absorbed Moisture on Fatigue Crack Propagation Behavior in Polyamides. Part A. Macroscopic Response. |
30 JAN 1981 |
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| Authors:
Philip E. Bretz; Richard W. Hertzberg; John A. Manson; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| The effect of plasticization on the fatigue crack propagation response in polyamides was examined by conducting fatigue tests on specimens of nylon 66 (N66), nylon 6 (N6), and nylon 612 (N612) which had been equilibrated at various levels of absorbed water. In N66 and N6, crack growth rates decreased as the water content was increased to about 2.5%; with increasing moisture content, FCP rates increased and at saturation (8.5% H2O) ... |
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| The Influence of Absorbed Moisture on Fatigue Crack Propagation Behavior in Polyamides. Part B. Fractography. |
30 JAN 1981 |
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| Authors:
Philip E. Bretz; Richard W. Hertzberg; John A. Manson; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| The fatigue fracture surface morphology of nylon 66, nylon 6 and nylon 612 was examined to ascertain mechanisms of fatigue crack propagation (FCP) in these polymers. Attention was also given to noting any correlation between fracture surface markings and macroscopic fatigue crack growth rate data. In general, observed changes in fracture surface appearance reflected an increasing level of plastic deformation with increasing water content, particularly in N66 and N6. Classical ... |
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| Discussion of 'A Model of Fatigue Crack Growth in Polymers'. |
28 DEC 1978 |
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| Authors:
Richard W. Hertzberg; Michael D. Skibo; John A. Manson; J. K. Donald; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| A model was previously proposed by Hertzberg, Skibo, and Manson to account for the sensitivity of fatigue crack growth rates to frequency. The model was based on the hypothesis that the mechanical Beta transition controls the fatigue deformation and on the use of time-temperature relationships to determine the match between the Beta transition frequency and temperature and the frequency and temperature of the test. An alternate model was recently proposed ... |
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| Fatigue Crack Propagation in Polymeric Materials. |
NOV 1978 |
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| Authors:
Richard W. Hertzberg; John A. Manson; LEHIGH UNIV BETHLEHEM PA MATERIALS RESEARCH CENTER
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| This report summarizes the results of a research program to bring polymer science and fracture mechanics technologies to bear on the subject of polymer fatigue. The first major thrust area concerned an analysis of fatigue fracture micromechanisms in amorphous engineering plastics. (Author) |
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| FATIGUE CRACK PROPAGATION IN RESIN-FIBER COMPOSITES. |
NOV 1969 |
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| Authors:
Richard W. Hertzberg; John A. Manson; Hans Nordberg; OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS
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| In order to gain a better understanding of fatigue failure processes in nonmetallic matrix composites, an exploratory study of fatigue crack propagation in both boron and glass fiber reinforced epoxy resins was begun. Under the test conditions employed the epoxy resin ERL 2256 was found to be extremely brittle and to possess limited capacity for stable crack extension. Due to the brittle behavior of the epoxy resin and the inability ... |
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Reports by Author
