Bump Test Research Articles

범프 로드에서 대형트럭 프레임의 탄성효과를 고려한 컴퓨터 모델 개발

This paper develops a computer model for estimating the bump characterisitcs of a cat)over type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using MSC.ADAMS. A shock absorber, a rubber bush, and a leaf spring affect a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC.PATRAN. A mode analysis is performed with the frame model using MSC.NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double wheel bump test is performed with an actual vehicle. In the double wheel bump, vortical displacement, velocity, acceleration are measured. Those test results are compared with the simulation results.

An eddy-viscosity limited algebraic stress model for shock-boundary-layer interaction

AbstractThis paper presents a μt-limited explicit algebraic stress model for shock-wave-turbulent boundary-layer interactions based on an investigation of various two-equation turbulence models. The results of the κ-ω model, the shear stress transport (SST) model, and a quadratic explicit algebraic stress model are presented and analysed for the Delery channel bump, and the Bachalo and Johnson axisym-metric bump test cases. While the κ-ω model failed to give good predictions, the SST model proved reasonably successful in predicting strong interaction problems. The non-linear quadratic explicit algebraic stress model gave improved results (when compared with the original κ-ω model) for the channel bump test cases, but was not as good as the SST model. Inspired by this investigation, a model formulation is proposed in which Bradshaw's assumption for eddy-viscosity limiting (as used in the SST model) is applied to a quadratic explicit algebraic stress model. The QSST model further improves the SST model for strong shock-boundary-layer interactions.

Field test results of a semi-active ER suspension system associated with skyhook controller

Performance characteristics of a semi-active ER (electro-rheological) suspension system are evaluated through the field test of a passenger car. Four ER shock absorbers are designed and manufactured for both front and rear parts, and their field-dependent damping properties are investigated. Subsequently, four independent skyhook controllers associated with ER shock absorbers are formulated by considering the vertical motions of the body and wheel of the car to be tested. Both ride comfort and steering stability of the car are evaluated via the field test showing bump and squat test responses.

Study of Wet Friction Material Test Under Severe Thermal and Mechanical Loading (“Bump Test”)

One of the fatigue tests used for friction materials is the so called “bump test”. In this test, one of the reaction disks in a pack of disks has machined bumps across the contact surface. These bumps generate locally high contact pressure and temperature. In this way, severe contact conditions like that arising in service can be reproduced. The major difficulty in utilizing the “bump test” is estimation of the local pressure and temperature. In this paper, a model is developed and experimental verification of thermoelastic contact is presented. The model represents a multi-surface contact problem for a pack of disks. Due to the presence of bumps, contact surfaces are not conforming. To solve this strongly nonlinear contact problem, a robust finite element code is used. The model also includes thermal effects generated by frictional heating. The coupled elastic contact and thermal problems are solved sequentially. Contact pressure at interfaces is measured in static conditions (without sliding) using pressure sensitive film. Good agreement between the model and the measurement is observed in sense of contact length and magnitude of pressure. In order to verify the full thermoelastic model, the transient temperature inside one of the disks is measured by thermocouples. The results agree with model predictions. The study shows that the local contact pressure is an order of magnitude higher than nominal pressure. Also temperatures are much higher than that predicted for uniform contact conditions. The developed model helps to understand complex thermoelastic effects accompanying the test and to control the test parameters.

Input Design for Large-Scale Sheet and Film Processes

Manipulated variable moves are computed to maximize the information contained in experimental data collected from sheet and film processes. The experimental design procedure minimizes the confidence ellipsoid of the critical model parameters over the manipulated variables subject to their physical constraints. For a simulated blown film process, the model is 1 order of magnitude more accurate than that identified from the industrial standard bump test experiments. The improved accuracy results in a 37% reduction in closed-loop thickness variations. This indicates that substantial benefits can be achieved by incorporating the optimal experimental design algorithm into industrial sheet and film process control algorithms.

Cladding Deformation due to Gas Bubble Swelling of UO2Pellet in Bump Test

Fission gas release in the bump tests was correlated to the deformations of claddings via mathematical product of the number of gas atoms and their residing time on grain boundaries. A positive correlation of the deformations with the product indicated that gas bubble swelling of pellets contributed to the pellet-cladding mechanical interaction (PCMI). Residual gaps prior to the bump tests turned out to be filled in at the bump terminal level by differential thermal expansion of pellet and cladding. Visible macro cracks existing in the central part of the pellet virtually vanished during the tests due to bubble swelling of the pellet. Together with these observations, quantitative image analysis of pellet porosity showed that the aforementioned PCMI was brought about by combination of differential thermal expansion and bubble swelling. A model to unify gas release, bubble growth and PCMI simulated well the observed behaviors of fission gas release from bump-tested rods. It was deduced by the model that hi...

Cladding deformation due to gas bubble swelling of UO2 pellet in bump test.

Cladding deformation due to gas bubble swelling of UO2 pellet in bump test.

Multigrid acceleration of a flux-difference splitting method for steady Euler equations

A flux-difference splitting based on the polynomial character of the flux-vectors is introduced for steady Euler equations. This splitting is applied to finite volumes centered around the vertices of the computational grid. A discrete set of equations is obtained which is both conservative and positive. The flux-difference splitting is done in an algebraically exact way. As a consequence, shocks are represented as sharp discontinuities, without wiggles. Due to the positivity, the set of equations can be solved by collective relaxation methods. A full multigrid method based on symmetric successive relaxation, full weighting, bilinear interpolation and W-cycle is presented. Typical full multigrid efficiency is achieved for the GAMM transonic bump test case since after the starting cycle and one multigrid cycle, the solution cannot be distinguished anymore from the fully converged solution.

The reliability of integrated circuits protected with Ti-W/Au bumps

The role of Ti-W/Au bumping in reliability and hermeticity testing environments has been studied using both epoxy- and silicon-encapsulated tape automated bonding (TAB) chips, plastic chip carriers and bare TAB chips, with and without bump test openings. Aging was performed in 85°C and 85% relative humidity conditions and measurements were carried out with electrical testing equipment. Covering all the critical openings on the passivation with Ti-W/Au bumps was found to be a very effective way to improve the reliability especially in humid conditions, where the failure mechanism is often based on the joint surfaces at the opening area. Mechanical protection was found to be the only purpose for die-level encapsulation because high reliability was achieved by bumping all test patterns. Furthermore, a method for total chip passivation based on Ti-W/Au bumping was evaluated for the mass bonding processes.

Voltage limiters for DRAMs with substrate-plate-electrode memory cells

To prevent substrate-plate-electrode (SPE) cell weakness due to substrate-bias voltage bounce, voltage limiters were applied to both the substrate and the sense-circuit supply source. A supply voltage V/sub CC/ bump test was introduced to evaluate their effectiveness. The voltage limiters have been implemented on an experimental 4-Mb DRAM. It was found that a wider operational margin, as compared to conventional DRAMs (without voltage limiters) having SPE cells, was achievable through the use of voltage limiters. These voltage limiters may be considered suitable for wide operational margin DRAMs with SPE cells. The substrate-bias voltage limiter, in particular, is more effective than the sense-circuit supply voltage limiter and offers a means of improving the operational margin of V/sub CC/ bump. >