• 대한기계학회논문집
• /
• 제12권4호
• /
• pp.755-759
• /
• 1988

Laminated Composites, SS41-Cu-SS41 plates are made by brazing bonding and hot bonding process. Fatigue repeated plane bending tests are carried out and the fracture behavior of Laminated composites, SS41-Cu-SS41 plates are compared with that of homogeneous steel, SS41plates. The following results are obtained; (1) The fatigue life of the brazing bonding plates is higher than those of SS41 plates and hot bonding plates under high stress. (2) The relations between the fatigue crack growth rate, da/dN and stress intensity factor are, da/dN=4.7*10$^{-10}$ $K^{3.20}$, for SS41 da/dN=7.8*10$^{-9}$ $K^{2.43}$, for CAH da/dN=3.6*10$^{-9}$ $K^{2.54}$, for CAB da/dN=1.58*10$^{-9}$ $K^{2.94}$ , for PAH da/dN=1.23*10$^{-9}$ $K^{2.69}$, for PAB

• Steel and Composite Structures
• /
• 제17권2호
• /
• pp.145-157
• /
• 2014

This study aimed to investigate the fatigue crack growth behavior of a kind of fiber metal laminates (FML) under four different stress levels. The FML specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimens. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that: (1) a-N and da/dN-a curves of FML specimens can be divided into transient crack growth segment, steady state crack growth segment and accelerated crack growth segment; (2) compared to 2024-T3 aluminum alloy, the fatigue properties of FML are much better; (3) da/dN-${\Delta}K$ curves of FML specimens can be divided into fatigue crack growth rate decrease segment and fatigue crack growth rate increase segment; (3) the maximum stress level has a large influence on a-N, da/dN-a and da/dN-${\Delta}K$ curves of FML specimens; (4) the fatigue crack growth rate da/dN presents a nonlinear accelerated increasing trend to the maximum stress level; (5) the maximum stress level has an almost linear relationship with the stress intensity factor ${\Delta}K$.

• 한국해양공학회지
• /
• 제7권2호
• /
• pp.131-140
• /
• 1993

To study the corrosion fatigue begavior of T.M.C.P. steel, the rotary bending fatigue test with the change of concentration of NaCl solution was carried out. Fatigue life in the corrosion environment is decreased markedly in comparision with that in the air. Fatigue limit in the air was about 225 MPa. In case of 3.5% NaCl solution fatigue life could be expressed as .sigma./sub f/=10,392 * (N/sub f/)/sup -o.2923 . According to the paris's rule, crack growth rates could be expressed as da/dN=2.62.*10/sup -7/ .DELTA. K/sup 1.09/(3.5% NaCl solution), da/dN=1.95 *10/sup -7 .DELTA. K/sup 1.05/(1% NaCl solution), da/dN=2.62 * 10/sup -7/.DELTA./sup 0.72/(0.01% NaCl solution) with da/dN expressed in mm/cycle and .DELTA.K in MPa.GAMMA.m. The crack growth rate in the corrosion environment was highest under 3.5% NaCl solution.

• 대한토목학회논문집
• /
• 제4권2호
• /
• pp.133-142
• /
• 1984

횡방향(橫方向)과 종방향(縱方向), 대입열용접(大入熱鎔接)과 소입열용접(小入熱鎔接), 모재(母材)와 같은 강도(强度)의 용접재료(鎔接材料) 사용(使用)과 모재(母材)보다 낮은 강도(强度)의 용접재료(鎔接材料) 사용(使用) 등으로 서로 비교되는 용접(鎔接)이음의 소인장시험편(小引張試驗片)을 만들어서 피로시험(疲勞試驗)을 행하여 피로구열(疲勞龜裂) 진전속도(進展速度) ${\frac{da}{dN}}$와 구열선단(龜裂先端) 부근의 응력확대계수(應力擴大係數)의 변동범위(變動範圍) ${\Delta}K$와의 관계곡선(關係曲線)을 그려서 비교시험간(比較試驗間)의 모재(母材), 열영향부(熱影響部) 및 용착금속부(鎔着金屬部)로 구분, 혹은 지금까지의 연구자료(硏究資料) 등과 비교검토하였다. 이 결과, 다음과 같은 현상들을 알 수 있었다. 기본적(基本的)으로, 용접방향(鎔接方向), 용접입열량(鎔接入熱量), 용접재료(鎔接材料)의 강도(强度), 혹은 모재(母材), 열영향부(熱影響部) 및 용착금속부(鎔着金屬部)의 구분 등에 따라 ${\frac{da}{dN}}-{\Delta}K$관계에 큰 차이가 없었다. 다만, 첫째, 소재(素材)에 대한 경우에 비해 대개 처음은 같은 ${\Delta}K$에서 ${\frac{da}{dN}}$가 상당히 늦다가 점차 증가하여 중간쯤에서 같아진 후 끝 부분에서 같은 ${\Delta}K$에서${\frac{da}{dN}}$가 다소 빨라짐을 알 수 있었다. 둘째, 열영향부(熱影響部)에서 용접금속부(鎔接金屬部)로 진전(進展)하면서 ${\frac{da}{dN}}$가 다소 늦어지는 것을 알 수 있었다. 셋째, 용접방향(鎔接方向)과 구열방향(龜裂方向)이 평행인 경우가 직각인 경우에 비해, 모재(母材)와 같은 용접재료(鎔接材料)를 쓴 경우 소입열용접(小入熱鎔接)인 경우가 대입열용접(大入熱鎔接)인 경우에 비해, 모재(母材)보다 낮은 용접재료(鎔接材料)를 쓴 경우 대입열용접(大入熱鎔接)인 경우가 소입열용접(小入熱鎔接)인 경우에 비해, 대입열(大入熱)의 평행용접(鎔接)의 경우를 제외한 모든 용접(鎔接)에서 모재(母材)와 같은 강도(强度)의 용접재료(鎔接材料)를 쓴 경우가 모재(母材)보다 낮은 강도(强度)의 용접재료(鎔接材料)를 쓴 경우에 비해 ${\Delta}K$가 낮은 시기(時期)에 일찍 저속(低速)으로 구열(龜裂)이 시작되어 ${\Delta}K$의 큰 증가없이 ${\frac{da}{dN}}$가 빠르게 증가한 다음 다른 경우와 같은 성상(性狀)으로 진전됨을 알 수 있었다. 넷째, 소입열용접(小入熱鎔接)의 경우 평행용접(鎔接)이 직각용접(鎔接)에 비해, 소입열용접(小入熱鎔接)이 대입열용접(大入熱鎔接)에 비해 같은 ${\Delta}K$에서 ${\frac{da}{dN}}$가 다소 늦은 것을 알 수 있었다.

• Archives of Pharmacal Research
• /
• 제23권4호
• /
• pp.360-366
• /
• 2000

The in vivo binding of dopamine (DA) radioligands to $D_2$receptors can be affected by competition with endogenous dopamine. In the present study, we used a brain slice preparation that provides more controlled conditions than in vivo preparations in order to examine the relationship between synaptic DA and the binding of [$^3H$] raclopride to $D_2$receptors. We also estimated the synaptic DA concentration in rat striatal slices by determining the changes in [$^3H$] raclopride binding. To correlate the changes in [$^3$H]raclopride binding with the concentration of synaptic DA, the kinetic parameters were determined. [$^3H$] Raclopride reached equilibrium binding conditions within two hours. The K value for DA in inhibiting [$^3$H]raclopride binding was about 2.2 nM. The increase in synaptic DA evoked by electrical stimulation decreased the striatal binding of [$^3H$] raclopride in a frequency-dependent manner. Increases in the DA concentration evoked by amphetamine (AMPH) or cocaine decreased [$^3H$] raclopride binding by 74% or 20%, respectively, corresponding to increases in the synaptic DA concentrations of 1.6 nM or 0.6 nM, respectively. Pargyline also decreased [$^3H$] raclopride binding by 36%corresponding at a concentration of 1.2 nM. In contrast, the depletion of synaptic DA by $\alpha$-methyl-p-tyrosine ($\alpha$-MpT) increased the specific binding of [$^3H$] raclopride by 43%when the DA concentration was decreased to 0.7 nM. The changes in the DA concentration at the synapse were responsible for the changes in the striatal binding of [$^3H$] raclopride. The values calculated in this study may therefore approximate the changes in the synaptic DA concentration in rat striatal slices following manipulation.

• 한국해양공학회지
• /
• 제9권1호
• /
• pp.92-100
• /
• 1995

The effect of different anisotropy and stress ratio on fatigue crack propagation behavior was investigated under various stress ratio(R=-0.4, -0.2, 0.2, 0.2, 0.4) using pure titanium sheet used in aerospace, chemical and food industry. The rack closure behavior under constant load amplitude fatigue crack propagation test was examined. Fatigue crack propagation rate da/dN was estimated in terms of effective stress intensity factor range, $\Delta$K$_{eff}$, regardless of various stress ratio but was influenced by anisotropy. Also, it was found that the effect of anisotropy was considerably decreased but still not negligible when he da/dN was evaluated by a conventional parameter, $\Delta$$K_{eff}$/E and when the modified da/dN.$\sqrt{\varepsilon}_f$ was evaluated by $\Delta$$K_{eff}$/E. On the other hand, da/dN could be evaluated uniquely by effective new parameter, $\Delta$K$_{eff}$/$sigma_{ys}$, regardless of anisotropy, as int he following equation da/dN=C''[\frac{{\Delta}K_{eff}}{{\sigma}_{ys}}]^{n''}. And effective stress intensity factor range ratio, U was estimated by the following equation with respect to the ratio of reversed plastic zone size, $\Delta r_{p}$ to monotonic plastic zone size, $r_p$ regardless of stress ratio and anisotropy. U=-4.45$(\Delta r_{p}/r_{p})^{2}$+4.1$(\Delta r_{p}/r_{p})$+0.245_{p})$+0.245

• 대한기계학회논문집A
• /
• 제31권3호
• /
• pp.344-354
• /
• 2007

The objective of this study is to investigate the effect of arbitrarily located defect around the circular hole in the aircraft structural material such as Al/GFRP laminates and monolithic Al alloy sheet under cyclic bending moment. The fatigue behavior of these materials may be different due to the defect location. Material flaws in the from of pre-existing defects can severely affect the fatigue crack initiation and propagation behavior. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic Al alloy and Al/GFRP laminates under cyclic bending moment. The fatigue behavior i.e., the stress concentration factor($K_t$), the crack initiation life($N_i$), the relationship between crack length(a) and cycles(N), the relationship between crack growth rate(da/dN) and stress intensity factor range(${\Dalta}K$) near a circular hole are considered. Especially, the defects location at ${\theta}_1=0^{\circ}\;and\;{\theta}_2=30^{\circ}$ was strongly effective in stress concentration factor($K_t$) and crack initiation life($N_i$). The test results indicated the features of different fatigue crack propagation behavior and the different growing delamination shape according to each location of defect around the circular hole in Al/GFRP laminates.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 추계학술대회 논문집
• /
• pp.263-268
• /
• 2001

The constant .DELTA. K fatigue tests are performed in SS41 and its weldment. The LASER ISDG method is used in determination of crack opening ratio. This method is more precise than indirect measurement method, faster and easier than other direct measurement method. And obtained results are followed 1) Crack opening ratio U is proportional to fatigue crack growth rate da/dN at constant .DELTA. K 2) Fatigue crack growth rate da/dN in weldment increases in weld metal and heat affected zone, decreases in base metal as crack grows.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제8권2호
• /
• pp.189-194
• /
• 2004

Amylase isozyme based three multivoltine viz., N+p, Np, N+ $p^{cho}$ and two bivoltine-D6+p, D6p syngenic lines (Syn. L) were developed from germplasm (GP) stocks Nistari (N) and D6 respectively. haemolymph isozyme pattern at pH 7.0 and 8.5 depicted a total 11 number (Am $y_{1 to 6}$ at pH 7.0 and Am $y^{l to 5}$ at pH 8.5) of native proteins (NP) of various sizes are amylase isozyme expressers. Among eleven NPs, two NPs of 770 kDa (Am $y^{6}$ at pH 7.0) and 376 kDa (Am $y^3$ at pH 8.5) are $\alpha$-amylase expressers and remaining NPs of 370, 364, 350, 329 and 274 kDa at pH 7.0 and 206, 292, 416, 725 kDa at pH 8.5 are $\beta$-amylase expressers. Accordingly, digestive juice amylase isozyme pattern at aforesaid pH also depicted a total number of 10 NPs (Am $y^{1 to 5}$) at each pH 7.0 and 8.5 are amylase expressers of which NP of 387 kDa (Am $y^4$ at pH 7.0) and 780 kDa (Am $y^{5}$ at pH 8.5) are a-amylase expresser. Remaining NPs of 338,297 ＆ 216 kDa at pH 7.0 and 370, 341, 329 ＆302 kDa at pH 8.5 are $\beta$-amylase expresser. Recurrent backcross lines (RBL) viz., N+pRBL and NpRBL were developed through introgression of high shell weight character (a multigenic trait) to be used further for congenic line (Con. L) development and to understand any association with introgressed character. Isozyme pattern in haemolymph of RBLs depicted only one $\alpha$-amylase of 770 kDa at pH 7.0 and 376 kDa at pH 8.0 with three and four respective $\beta$-amylase bands but in bivoltine lines numbers of $\beta$-amylase bands vary between 1 to 2 at aforesaid pH. Variability was also observed in digestive juice of multivolitine and its RBLs but bivoltine lines express null activity at both pH except appearance of one very week $\alpha$-amylase band D6+p at pH 8.5. Overall study suggests that not a single NP at both pH is common for expression of any band of amylase isozyme i.e., a totally different set of proteins are the amylase isozyme expresser at specific pH and no molecular factor of amylase is associated in developed RBLs which showed improvement on survival, single cocoon shell weight (SCSW) and single filament length over receptor parents.s.s.s.

• 대한핵의학회지
• /
• 제31권4호
• /
• pp.421-426
• /
• 1997

[$^{18}F$]FMBS는 도파민 $D_2$ 수용체 방사성추적자로서 유망한 성질을 지니고 있다. [$^{18}F$]FMBS는 비교적 높은 특이결합/비특이결합 비를 제공하며, 그 체내결합은 도파민 $D_2$ 수용체에 대하여 높은 특이성과 선택성을 보인다. 도파빈 $D_2$ 수용체 측정을 위한 보다 적합한 PET 방사성추적자를 얻기 위해서는 [$^{18}F$]FMBS의 낮은 뇌섭취와 느린 역학을 개선할 수 있는 화학적 구조의 변형이 시도되어야 하며, [$^{18}F$]FMBS는 이러한 시도의 골격이 될 수 있을 것으로 믿는다.