• Transactions of Materials Processing
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• v.28 no.6
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• pp.368-374
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• 2019

The past recent years have seen an increasing use of high-strength steel sheets in the automotive industry. However, the formability and damage prediction of these materials requires accurate acquisition of necking and fracture strains. Digital image correlation (DIC) is used to accurately capture the necking and fracture strains during testing. The fact that single time points of capturing vary with frame rate makes the need for an investigation necessary. For the high-strength steel DP980, the frame-rate dependences of the final necking and fracture strains values are analyzed here. To eliminate the influence of gauge length, the strains were measured locally by DIC. Results for three specimen shapes obtained with frame rates of 1 and 900 fps (frames per second) were considered and based on them, triaxiality failure diagrams (TFD) are established. It was observed that after diffuse necking, the deformation path departed from the initially linear one, and the stress triaxiality grew with ongoing deformation. It was further revealed that the frame rate-dependence of the necking strain was rather low (< 2%), whereas the fracture strain could be underestimated by up to 8% when the lower frame rate of 1 fps was used (compared with 900 fps). In this study, this issue is investigated while taking into consideration the three different triaxialities. These results demonstrate the importance of choosing an appropriate frame rate for the determination of necking and fracture strains in particular.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.470-474
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• 2008

The rate-dependent constitutive model and the rate-independent model were analyzed for comparing with the piezocone penetration test and dissipation test. The mathematical expressions of the rate-dependent constitutive model were introduced, and the predictions using the both models were compared with the experimental results of in-situ field test. The rate-dependent model analysis gave better results than the rate-independent model analysis, that is appreciated since the process of the piezocone penetration and dissipation depends on the strain rate. Therefore, it is recommended the concept of the rate-dependent model for the prediction of soil behaviors using the field penetration test.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.312-317
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• 2013

The armyworm, Pseudaletia separata was occurred suddenly in a golf club in Namhae, Gyeongnam province in 2013. Thus, pathogenicity of seven species of entomopathogenic nematodes (Steinernema carpocapsae GSN1 strain, S. glaseri Dongrae strain, S. longicaudum Nonsan strain, S. monticolum Jiri strain and S. siamkayai, Heterorhabditis sp. Gyeongsan strain, and H. bacteriophora Hamyang strain) was evaluated against armyworm on tall fescue in pot and golf course to control this pest environmentally friendly. The pathogenicity against P. separata larvae was significantly different depending on nematode species. The corrected mortality of fifth instar of P. separata was 100% in the treatment with S. carpocapsae GSN1 in 7 days in tall fescue pot. However, there was not different in the mortality of fifth instar of P. separata (80 to 100%) at the rate of 385 to 6,160 infective juveniles (Ijs) ($=2.5{\times}10^2$ to $4{\times}10^5Ijs/m^2$) of S. carpocapsae GSN1 strain in each pot. Corrected mortality of P. separata was 65 and 60% at the rate of $10^5Ijs/m^2$ of S. carpocapsae GSN1 and S. longicaudum Nonsan strain, respectively in the tall fescue of golf course.

• Journal of Plant Biology
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• v.1 no.1
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• pp.1-6
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• 1958

1. Study was made to investigate effects of desoxyribonucleates on copper-resistance in yeast. 2. It is found that the resistant strain there exists the phenomic lag. 3. In the occurrence of the resistant strain there exists the phenomic lag. 4. Desoxyribonucleate isolated from copper resistant culture is capable of inducing the resistant strain, which is the same type as donor of the resistant type. It accelerated the rate of variation to the resistant, but it is of no effect on the resistant strain. 5. Desoxyribonucleate derived from non-resistant type inhibits growth of the resistant strain and delays the initial phase of growth. However, it is of no effect on the sensitive strain. It is concluded that desoxyribonucleate derived from resistant culture is capable of inducing the resistance, however, nonresistant type desoxyribonucleate is of no effect on inducing the resistance.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.53-60
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• 1997

The strain localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region along with softening behavior. The objective of this paper is to develope a consistent algorithm for the finite element modeling of localized zone in the analysis of the strain-localization in concrete. For modeling of the localized zone in concrete under strain localization, a general Drucker-Prager failure criterion which can consider nonlinear strain softening behavior of concrete after peak-stress is introduce. The return-mapping algorithm is used for the integration of the elasto-plastic rate equation and the consistent tangent modulus is derived. Using finite element program implemented with the developed algorithms, strain localization behaviors for the different sizes of concrete specimen under compression are simulated.

• Parasites, Hosts and Diseases
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• v.22 no.2
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• pp.153-160
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• 1984

An experimental study was undertaken to observe the difference in susceptibility of mouse strains to Metagonimus yokogawai infection by estimating it from worm recovery rate and dimension of worms. It was also studied the effects of prednisolone injection on the chronological pattern of worm recovery in ICR mice. The metacercariae were obtained from sweetfish and 300 in each number were given to 5 strains (CBH, A, DBA, $C^{57}BL$ and KK) of mice, and after 7 days period, the worms were collected from their intestine. Prednisolone at the dose of 10 mg/kg was injected to ICR mice every other day from 7 days prior to infection until sacrificed at 6 hours to 35th post-infection day. ICR mice infected with M. yokogawai but untreated were used for controls. The success rate in infection of mice ranged 25.0-83. 3% by strains, the worm recovery rate 1. 2-18. 9%, and the average size of worms O. 554-0. 683 mm long and 0.214-0.244 mm wide. The higher rates and larger size of worms were observed in KK and $C^{57}BL$ strains than others and the difference was statistically significant. In ICR mice for control, the worm recovery rate until 1 day after infection was relatively high (38-66%) but it became much lower (less than 0.7%) during 1-35 days. However, prednisolone injection brought about persistently high recovery rates (16-80%) until 21 days. It was concluded that the susceptibility to M. yokogawai infection is different by strains of mice but it can be elevated by prednisolone injection probably due to suppression of Immune respon3e3 in ICR mice.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1193-1199
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• 1990

Effects of strain hardening exponents on the behavior of fatigue crack propagation are experimentally investigated. The retardation effect of fatigue crack propagation after single overloading is investigated in relation to strain hardening exponent and crack closure. A relationship between crack opening ratio and strain hardening exponents is inspected through an examination of the crack closure behavior. An empirical equation relating retardation effect of fatigue crack propagation after single overloading, percent peak load and strain hardening exponent of materials is proposed.

• Geomechanics and Engineering
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• v.29 no.2
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• pp.99-111
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• 2022

Instability of bolted rock mass has been a major hazard in the underground coal mining industry for decades. Developing effective support guidelines requires understanding of complex bolted rock mass failure mechanisms. In this study, the dynamic failure behavior, mechanical behavior, and energy evolution of a laboratory-scale bolted specimens is studied by conducting laboratory static-dynamic coupled loading tests. The results showed that: (1) Under static-dynamic coupled loading, the stress-strain curve of the bolted rock mass has a significant impact velocity (strain rate) correlation, and the stress-strain curve shows rebound characteristics after the peak; (2) There is a critical strain rate in a rock mass under static-dynamic coupled loading, and it decreases exponentially with increasing pre-static load level. Bolting can significantly improve the critical strain rate of a rock mass; (3) Compared with a no-bolt rock mass, the dissipation energy ratio of the bolted rock mass decreases exponentially with increasing pre-static load level, the ultimate dynamic impact energy and dissipation energy of the bolted rock mass increase significantly, and the increasing index of the ratio of dissipation energy increases linearly with the pre-static load; (4) Based on laboratory testing and on-site microseismic and stress monitoring, a design method is proposed for a roadway bolt support against dynamic load disturbance, which provides guidance for the design of deep underground roadway anchorage supports. The research results provide new ideas for explaining the failure behavior of anchorage supports and adopting reasonable design and construction practices.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1863-1870
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• 2000

When an impact stress is applied on the external boundary of double cantilever beam of orthotropic material which crack length is greater than specimen hight and anistropic ratio is very high, dyna mic energy release rate is derived, and the relationship between dynamic energy release rate and crack propagating velocity is studied. Dynamic energy release rate to static energy release rate is decreased with increasment of crack propagating velocity. The relationships between dynamic energy release rate and vertical strain have a similar pattern with those between static energy release rate and vertical strain. When normalized time(Cstla) is greater than or equal to 2, dynamic energy release rate approaches to a constant value.

• Nuclear Engineering and Technology
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• v.5 no.1
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• pp.55-64
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• 1973

The effect of compression in the strain ageing of Ferrovac E iron has been examined with compressive testing following the prestrain in compression. Both prestraining and testing were preformed at room temperature with the strain rate of 1.9$\times$10$^{-4}$ se $c^{-1}$ and that of 0.95$\times$10$^{-4}$ se $c^{-1}$ , respectively. Ageing was carried out at several temperatures below 8$0^{\circ}C$ using thermostatically controlled oil baths with a temperature control within$\pm$1$^{\circ}C$. It was found that the rate of strain ageing obeyed the $t^{2}$3/ law up to about five hours ageing at 6$0^{\circ}C$. The rate was slower than theses reported in case of the tensile prestrained iron. Activation energy for strain ageing has been estimated as 21.5 Kcal/mole at tile first stage of the aging process. At the second stage of ageing where the $t^{2}$3/ law is still valid, however, the activation energy was somewhat decreased. The activation energy at the first stage of ageing was about 10% larger than published results on the tensile-prestraining. This difference between the activation energies is explained in terms of the residual stress field in lattice.