Loading-unloading model of contact between elastic-plastic ellipsoid and rigid plane

Jian Chen,Wangyang Zhang,Di Liu,Chenglong Wang,Linbo Zhu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

The mechanical behaviour of the ellipsoidal asperity and rigid planes during loading and unloading are fundamental problems in contact mechanics. This study investigates the contact between elastic-perfectly plastic ellipsoidal asperity for different ellipticities and rigid planes under normal conditions during the loading and unloading process using the finite element method. The results show that the changing trend of the contact load, residual displacement, contact area, and plastic work with displacement under different ellipticities is similar, but the magnitude is different. The contact area during unloading is not always smaller than that during loading with the same displacement. Moreover, the initial unloading stage contact area is larger than that of the loading stage. Based on the numerical model calculation results, analytical dimensionless expressions are proposed for the residual displacement, plastic work, contact area, and contact load after fully unloading the ellipsoids with different ellipticities for a wide range of displacements. The prediction results from previous models are used to verify the effectiveness and correctness of the proposed equations. These empirical relations can be combined with statistical or fractal methods to study the contact behaviour of macroscopic rough surfaces.

원형 핀과 구멍의 접촉에서 헤르츠 응력장 가정을 위한 조건

김형규(Hyung-Kyu Kim) 한국트라이볼로지학회 2015 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.31 No.5

This paper focuses on the conformal contact problem. A typical example of conformal contact is the contact between a pin and hole. In particular, this paper focuses on the condition for assuming a contact stress field to be a Hertzian pressure profile by using well-known classical solutions associated with Hertzian contact. Persson first developed the conformal contact analysis method around half a century ago, but there have been no significant improvements since then. The present research also adopted this method, but developed new solutions from the viewpoint of application to structural design. The analysis began with a comparison between Persson° Øs conformal contact stress and the Hertzian stress fields. The next step was to check the differences in the normalized stress values of both. This study used the tolerance for the difference in the peak stresses of Persson° Øs solution and the Hertz solution to validate the Hertzian assumption. This gave the range for the difference in radii of the pin and hole when the contact force and mechanical properties of the material are specified. The results showed that, at a tolerance of 5%, the Hertzian assumption is valid if half of the contact angle is less than 35°ý. In addition, the Hertzian assumption holds even for a relatively long contact length, in contrast to the general incomplete contact problem. This paper discusses these results along with other aspects of the application to the design.

트라이볼로지 손상을 억제하기 위한 구조물 모서리부 설계 : 제1부 - 설계공식 개발

김형규(Hyung-Kyu Kim) 한국트라이볼로지학회 2015 한국윤활학회지(윤활학회지) Vol.31 No.4

This paper describes a design method for the corner radius of a contacting body using the theoretical approach of contact mechanics. A complete contact, as in the case of a sharp-cornered punch, produces singular contact traction: whereas, in an incomplete contact, the singular contact traction disappears because of the rounded corners, and the contact edges are within the rounded regions. The design method aims to determine the conditions of the contact force as well as the material properties in an incomplete contact. The incomplete contact changes into the complete contact again when the contact edges exceed the rounded regions owing to either an increased contact force or the compliance of the materials. The contact length of a rounded punch is used as a parameter to derive the required conditions. As a result, a design formula is obtained, which provides a minimum allowable radius when the materials, normal contact force, and the length of a flat region of the punch are predetermined. This work consists of two parts: Part I includes a theoretical background, design method, and formula, and Part II describes the actual process with the investigation of design parameters.

The contact problem of the functionally graded layer resting on rigid foundation pressed via rigid punch

Murat Yaylacı,Merve Abanoz,Ecren Uzun Yaylacı,Hasan Ölmez,Dursun Murat Sekban,Ahmet Birinci 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.5

The solution of contact problems is extremely important as we encounter many situations involving such problems in our daily lives. One of the most important parameters effective in solving contact problems is the materials of the parts in contact. While it is relatively easy to solve the contact mechanics of the systems created with traditional materials with a homogeneous microstructure and mechanical distribution, it may be more difficult to solve the contact problem of new generation materials that do not show a homogeneous distribution. As a result of this situation, it is seen that studies on contact problems of materials that do not exhibit such a homogeneous internal structure and mechanical properties are extremely limited in the literature. In this context, in this study, analytical and numerical analyzes of a contact problem created using functionally graded materials were carried out and the results were evaluated mutually. It has been decided that the contact areas and contact pressures acquired from numerical method are reasonably appropriate with the results obtained from the analytical method.

Carrier transport mechanism of Al contacts on n-type 4H-SiC

Kim, Seongjun,Kim, Hong-Ki,Jeong, Seonghoon,Kang, Min-Jae,Kang, Min-Sik,Lee, Nam-Suk,Cuong, Tran Viet,Koo, Sang-Mo,Kim, Hyunsoo,Shin, Hoon-Kyu Elsevier 2018 Materials letters Vol.228 No.-

<P><B>Abstract</B></P> <P>We investigated the carrier transport mechanism at Al/n-type 4H-SiC contacts. As-deposited Al exhibited the good ohmic behavior, while the thermal annealing leads the significant degradation of contact properties, i.e., the specific contact resistance was 3.97 × 10<SUP>−3</SUP>, 4.1 × 10<SUP>−2</SUP>, and 0.153 Ω cm<SUP>2</SUP> for the as-deposited, 200 and 400 °C-annealed condition, respectively. The ohmic mechanism of as-deposited contact could be explained by field emission model, yielding a tunneling parameter of 0.44 eV, i.e., the ohmic behavior is due to the tunneling through the thin barrier. The degradation of ohmic contact after thermal annealing caused by the formation of oxide layer between the Al and SiC.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We proposed an use of aluminum as a contact metal to form ohmic contact without thermal annealing process. </LI> <LI> The Al/n-type 4H-SiC contact showed an ohmic behavior without thermal annealing. </LI> <LI> The as-deposited contact could be explained by field emission model. </LI> <LI> The thermal annealing led to the degradation of ohmic behavior due to the generation of interfacial oxide. </LI> </UL> </P>

Double characteristic BNO-SPI-TENGs for robust contact electrification by vertical contact separation mode through ion and electron charge transfer

Cheedarala, Ravi Kumar,Duy, Le Chau,Ahn, Kyoung Kwan unknown 2018 Nano energy Vol.44 No.-

<P><B>Abstract</B></P> <P>• Contact-electrification is a conventional triboelectrification technique for generating current through charge transfer when two different polarized materials are brought into contact. For the first time, in-built alternate hydrophilic and hydrophobic nano channels were developed where both ionic and electronic charge transfer mechanisms were realized through contact separation mode between BNO-SPI films and PTFE. In this paper, we examined the dynamic interaction between these materials and observed adequate output performance. The novel BNO-SPI-TENGs (i.e. SO3H.BNO-SPI-TENG, SO3Li.BNO-SPI-TENG, and SO3H.TEA.BNO-SPI-TENG) produced 75V and 1µA, 43V and 0.6µA, and 9V and 0.13µA of open-circuit voltages (Voc) and short-circuit currents (Jsc) at 6Hz, respectively. Particularly, the SO3H-BNO-SPI was dramatically boosted up the performance of TENG, up to 733% of Voc and 669% of Jsc, with respect to the SO3H.TEA-BNO-SPI because the mobility of H+ ions is very high on the device surface compared to the other two Li+ and TEA bulky ions. The developed dual characteristic BNO-SPI-TENGs are very good candidates for fulfilling the need for alternate contact separation mode TENGs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel double characteristic hydrophilic and hydrophobic nano channel oriented BNO-SPI films were proposed. </LI> <LI> Contact electrification process was took place on the BNO-SPI films that followed ion and electron transfer mechanisms. </LI> <LI> An electron-donor-acceptor complex mechanism was proposed for the electron transfer mechanism. </LI> <LI> High triboelectric (V<SUB>oc</SUB>) and (J<SUB>sc</SUB>) were observed from BNO-SPI-TENGs, in particular, 75V and 1µA for SO<SUB>3</SUB>H.BNO-SPI-TENG at 6Hz. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

이중 스카치 요크 기구를 이용한 접점 개폐 메커니즘의 설계

양홍익(H. I. Yang),안길영(K. Y. Ahn),정광영(K. Y. Jeong) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

In this paper, a double scotch yoke mechanism for moving simultaneously the fixed contact and moving contact of a gas circuit breaker is proposed and designed to improve the breaking characteristics of the circuit breaker. Firstly, the design parameters of the scotch yoke are kinematically determined from the desired design condition of the circuit breaker. Next, the stroke curve of the moving contact is designed by considering the design parameter and the specified opening characteristics of electric contacts. Based on the scotch yoke and stroke curve, the dynamics of the electric contacts is analyzed using ADAMS model of switch mechanism.

접촉 조인트에서의 운동자유도

이장용(Jangyong Lee) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.4

The mobility (degree of freedom) of mechanisms can be regarded as independent coordinate to define its position. This concept is essential for kinematics, and for designing mechanisms in the practical point of view. Gruebler's equation has been applied to estimate the mobility using number of links and joints of a mechanism. In practical case, there are many types of mechanisms, which transfer motion by direct contact between two links. However, no exact kinematic definition has existed for the joint that the contact takes place in a mechanism. In this paper, a new concept of contact joint is defined and modified Gruebler's equation is suggested to calculate mobility of a mechanism with the joint. This concept would be useful in mechanism design because it will be possible to manage many contact mechanisms with kinematic exactness.

LCD 팬널의 접촉프린팅 공정에서의 접촉 평평도 연구

장시열(Siyoul Jang),임홍재(Hong Jae Yim),강윤석(Yun Seok Kang) 한국트라이볼로지학회 2006 한국트라이볼로지학회 학술대회 Vol.2006 No.6

Surface contacts between mold and target should be in parallel for the imprinting mechanism. However, the size of contacting area makes it difficult for both mating surfaces to be in all contact because of precision level of the imprinting machine and the waviness of mold and target. The gripping force for both mold and target with the vacuum chuck is also major effect to interrupt the full contact, which must be avoided in imprinting mechanism. In this study, the preliminary study for the causes of non-uniformity of contacting surfaces such as mold and target is performed with 470 × 370㎟ LCD panel size.

진공척 흡착패드 형태에 따른 대면적 임프린팅 균일 접촉 향상 연구

장시열(Siyoul Jang) 한국트라이볼로지학회 2008 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.24 No.6

The contact surfaces between mold and target should be in parallel for a proper imprinting process. However, large size of contacting area makes it difficult for both mating surfaces (mold and target planes) to be in all uniform contact with the expected precision level in terms of thickness and position. This is caused by the waviness of mold and target although it is very small relative to the area scale. The gripping force for both mold and target by the vacuum chuck is other major effect to interrupt the uniform contact, which must be avoided in imprinting mechanism. In this study, the cause of non-conformal contact mechanism between mold and target is investigated with the consideration of deformation due to the vacuum gripping for the size 470×370㎟ LCD panel.