• Steel and Composite Structures
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• 제19권3호
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• pp.585-599
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• 2015

This paper presents the experimental work on fatigue life and specific fatigue strength of circular hollow sectioned steel tube and wood filled circular hollow section steel tube. Burning effect was observed in the case of circular hollow sectioned steel tube when it is subjected to Maximum bending moment of 19613.30 N-mm at 4200 rpm, but this did not happen in the case of wood filled hollow section. Statistical analysis was done based on the experimental data and relations have been built to predict the number of cycles for the applied stress or vice versa. The relations built in this paper can safely be applied for design of the fatigue life or fatigue strength of circular hollow sections and wood filled hollow sections. Results were validated by static specific bending strengths determined by ANSYS using a known applied load.

• Steel and Composite Structures
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• 제32권3호
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• pp.313-323
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• 2019

Ratcheting boundary is firstly determined by experiment, elastic-plastic finite element analysis combined with C-TDF and linear matching method, which is compared with ASME/KTA and RCC-MR. Moreover, based on elastic modulus adjustment procedure, a novel method is proposed to predict the ratcheting boundary for a pressurized pipe subjected to constant internal pressure and cyclic bending loading. Comparison of ratcheting boundary of elbow pipe determined by the proposed method, elastic-plastic finite element analysis combined with C-TDF and linear matching method, which indicates that the predicted results of the proposed method are in well agreement with those of linear matching method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1740-1743
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• 2007

In this study, two types of fatigue tests were conducted. First, cyclic bending tests were performed using the micro-bending tester. A four-point bending test method was adopted, because it induces uniform stress fields within a loading span. Second, thermal fatigue tests were conducted using a pseudo power cycling machine which was newly developed for a realistic testing condition. The pseudo-power cycling method makes up for the weak points in a power cycling and a chamber cycling method. Two compositions of solder are tested in all test condition, one is lead-free solder (95.5Sn4.0Ag0.5Cu) and the other is eutectic lead-contained solder (63Sn37Pb). In the cyclic bending test, the solder that exhibits a good reliability can be reversed depending on the load conditions. The lead-contained solders have a longer fatigue life in the region where the applied load is high. On the contrary, the lead-free solder sustained more cyclic loads in the small load region. A similar trend was detected at the thermal cycling test. A three-dimensional finite element analysis model was constructed. A finite element analysis using ABAQUS was performed to extract the applied stress and strain in the solder joints. A constitutive model which includes both creep and plasticity was employed. Thermal fatigue was occurred due to the creep. And plastic deformation is main damage for bending failure. From the inelastic energy dissipation per cycle versus fatigue life curve, it can be found that the bending fatigue life is longer than the thermal fatigue life.

• 대한기계학회논문집A
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• 제36권10호
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• pp.1227-1234
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• 2012

본 연구에서는 감육결함이 가공된 실배관 곡관 시편을 대상으로 10 MPa의 내압과 반복 굽힘하중 조건에서 피로 시험을 수행하였다. 시험에는 감육결함이 곡관의 외호부와 내호부에 존재하는 경우를 고려하였으며, 반복 하중으로는 완전 역방향의 변위제어 형태로 작용되는 In-plane 상의 굽힘하중이 고려되었다. 실험 결과, 감육결함이 곡관의 외호부에 존재하는 경우에는 결함부가 아닌 곡관의 측면에서 축방향 균열이 생성되었다. 또한, ASME Sec.III의 설계 피로곡선에서 예측된 건전 곡관의 피로수명보다 긴 피로수명을 보였으며, 피로수명이 결함 길이에 크게 영향을 받지 않았다. 반면, 결함이 내호부에 존재하는 곡관은 내호부에서 원주방향 균열이 발생하였으며, 피로수명은 ASME Sec.III의 설계 피로곡선에서 예측한 건전 곡관의 피로수명보다 짧은 값을 보였다. 또한, 내호부 감육 곡관의 피로수명은 결함 길이가 감소함에 따라 뚜렷이 감소하였다.

• Structural Engineering and Mechanics
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• 제75권5호
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• pp.529-540
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• 2020

The mechanical properties of timber construction have drawn more attention after the 2013 Lushan earthquake. A strong desire to preserve this ancient architectural styles has sprung up in recent years, especially for residential buildings of the mountainous areas. In the column-and-tie timber construction, continuous-tenon joints are the most common structural form to connect the chuanfang (similar to the beam in conventional structures) and the column. To study the cyclic performance of the continuous-tenon joints in column-and-tie timber construction, the reversed lateral cyclic loading tests were carried out on three 3/4 scale specimens with different section heights of the chuanfang. The mechanical behavior was assessed by studying the ultimate bending capacity, deformation ductility and energy dissipation capacity. Test results showed that the slippage of chuanfang occurred when the specimens entered the plastic stage, and the slippage degree increased with the increase of the section height of chuanfang. An obvious plastic deformation of the chuanfang occurred due to the mutual squeezing between the column and chuanfang. A significant pinching was observed on the bending moment-rotation curves, and it was more pronounced as the section height of chuanfang increased. The further numerical investigations showed that the flexural capacity and initial stiffness of the continuous-tenon joints increased with the increase of friction coefficient between the chuanfang and the column, and a more obvious increasing of bending moment occurred after the material yielding. The compressive strength perpendicular to grain of the material played a more significant role in the ultimate bending capacity of continuous-tenon joints than the compressive strength parallel to grain.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1584-1592
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• 2000

Reversed plane bending fatigue tests were conducted on SiC whisker reinforced aluminum composite which were consolidated by squeeze casting process. Initiation and growth of small surface fatigue c racks were investigated by means of a plastic replica technique. The fatigue crack initiated in the vicinity of SiC whisker/matrix interface. It was found that a fatigue crack deflected along SiC whisker and grew in a zig-zag manner microscopically, although the crack propagated along the direction normal to the loading axis macroscopically. The coalescence of micro-cracks was observed in the tests conducted at high stress levels, but were not evident in tests in which lower levels of stress were applied. Due to the coalescence, a higher crack growth rate of small cracks rather than those of long cracks was recognized in da/dn -ΔK realtionship.

• Steel and Composite Structures
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• 제21권4호
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• pp.703-753
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• 2016

The ratcheting behavior was studied experimentally for Z2CND18.12N elbow piping under cyclic bending and steady internal pressure. Dozens of cyclic plasticity models for structural ratcheting responses simulations were used in the paper. The four models, namely, Bilinear (BKH), Multilinear (MKIN/KINH), Chaboche (CH3), were already available in the ANSYS finite element package. Advanced cyclic plasticity models, such as, modified Chaboche (CH4), Ohno-Wang, modified Ohno-Wang, Abdel Karim-Ohno and modified Abdel Karim-Ohno, were implemented into ANSYS for simulating the experimental responses. Results from the experimental and simulation studies were presented in order to demonstrate the state of structural ratcheting response simulation by these models. None of the models evaluated perform satisfactorily in simulating circumferential strain ratcheting response. Further, improvement in cyclic plasticity modeling and incorporation of material and structural features, like time-dependent, temperature-dependent, non-proportional, dynamic strain aging, residual stresses and anisotropy of materials in the analysis would be essential for advancement of low-cycle fatigue simulations of structures.

• Composites Research
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• 제21권6호
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• pp.15-22
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• 2008

본 연구는 SiC입자를 20% 강화된 알루미늄기 복합재료를 이용해서 평면굽힘피로시험을 향했다. 표면미소피로균열의 발생 및 진전거동은 레프리카법으로 연속관찰을 했고 파괴원인과 파괴기구를 규명하기 위해서 주사전자현미경을 이용했다. da/dn-$K_{max}$ 관계에서 저응력 레벨에서는 여러 개의 균열이 진전하고, 합체 등이 일어나는 것으로부터 진전속도는 꽤 분산(흐트러짐)이 심하고, 고응력 레벨에서는 비교적 흐트러짐은 적게 나타나는 것을 알 수 있었다.

• Composites Research
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• 제22권3호
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• pp.74-81
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• 2009

본 연구는 SiC 입자 강화된 알루미늄기 복합재료와 SiC 휘스커 강화된 알루미늄기 복합재료를 이용해서 평면굽힘피로시험을 행했다. 표면미소피로균열의 발생 및 진전거동은 레프리카법으로 연속관찰을 했고 파괴원인과 파괴기구를 규명하기 위해서 주사전자현미경을 이용했다. 두 재료 모두 da/dn - $K_{max}$ 관계에서 고응력 레벨에서는 $K_{max}$의 증가에 따라 da/dn이 증가 했지만, 저응력 레벨에서는 da/dn이 감소하다가 증가하는 것을 알 수 있다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권9호
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• pp.427-433
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• 2001

A linear ultrasonic motor was designed by a combination of the first longitudinal and fourth bending mode, and the motor consisted of a straight aluminum alloys bar bonded with a piezoelectric ceramic element as a driving element. That is,$L_1-B_4$ linear ultrasonic motor can be constructed by a multi-mode vibrator of longitudinal and bending modes. Linear ultrasonic motors are based on an elliptical motion on the surface elastic body, such as bar or plates. In general, the natural resonance frequency of the stator is used as a driving frequency of the motor which provides a large elliptical motion. The corresponding eigenmode of one resonance frequency can be excited twice at the same time with a Phase shift of 90 degrees in space and time. And the rotation can be reversed by changing the phase between the two signals from sin$\omega$t to cos$\omega$t. Moreover, the tangential force pushes the slider(rotor) and, therefore, determines the thrust and speed of the motor. The experimental results of fabrication motors, bimorph-tyPe motor showed more excellent than unimorph-type. The maximum speed of TBL-200, TBL-300, TBL-400, TBL -220, TBL-310 and TBL-420 motors were 0.12, 0.37, 0.39, 0.14, 0.55 and $0.60ms6{-1}$, respectively. And the efficiency were reported 1.15, 7.9, 6.6, 2.36, 10.1 and 16.5%, respectively. That time, output thrust of the motor was a strong(1~2N) and the weight of stator was a lightness(5~7g).