Conventional Cushion Research Articles

An Udwadia-Kalaba Equation based active seat suspension controller for mining dump trucks

Abstract: This work proposes the use of an active seat suspension system to reduce the negative effects of whole body vibrations experienced by mining dump truck drivers during loading of ore at high velocity by large shovels. The control system is developed using the Udwadia-Kalaba equation, a method from analytical dynamics, which does not require linearisation of the system dynamics. A multibody system model of the dump truck with an active seat suspension system and passive hydro-pneumatic suspension struts is developed using a pseudo-coordinate based approach. The control objective is first formulated as a mechanical constraint in order to apply this method. Simulation results are compared with particular focus on the acceleration developed at the mining dump truck’s seat, comparing a conventional cushion seat with the actively controlled seat suspension. Hence, validating the effectiveness of this approach.

Development of a method for manufacturing customized nasal mask cushion for CPAP therapy.

A continuous positive airway pressure (CPAP) device is considered one of the most effective treatments for obstructive sleep apnea (OSA). However, many patients receiving this treatment complain of mask discomfort and other issues. Therefore, this study aimed to develop a customized nasal mask cushion to reduce the discomfort associated with conventional masks. First, a 3D face scanner was used to obtain 3D facial data of participants. Second, a model of the face was created by reverse-engineering and then used for the computer-aided design (CAD) of the cushion. Finally, computer numerical control (CNC) was used to manufacture the mold, into which silicone was then injected slowly. A perceived comfort questionnaire was used to compare the customized and conventional cushions. 40 patients were randomly divided into two groups: 20 patients in the control group used a conventional cushion, and the remaining 20 patients used the customized cushion. The customized cushion was found to be superior to the conventional cushion. There are clear differences in the headgear force of the two cushion types (P = 0.001). The customized cushion applied less force to a patient’s face than a conventional cushion. Furthermore, there were obvious differences in the fit of the cushions (P = 0.001). Patients using the customized cushions experienced a better fit than those using the conventional cushions. This study has developed a new method for manufacturing customized cushions with better cushion fit through rapid tooling.

Clinical verification of patients with obstructive sleep apnea provided with a customized cushion for continuous positive airway pressure

Statement of problemPatients with obstructive sleep apnea may stop breathing momentarily during sleep because of a narrow upper respiratory tract. One of the main treatments for obstructive sleep apnea is continuous positive airway pressure. However, after long-term treatment, patients tend to complain about the leakage, inconvenience, and discomfort of the nasal mask. PurposeThe purpose of the study was to develop customized cushions and compare the clinical performance of the customized cushion with the conventional one. Material and methodsEach participant's face was replicated by using a 3-dimensional scanner and reverse-engineering technology, and computer numerical control techniques were used to design and manufacture customized cushions. Forty participants were randomly divided into 2 groups, a control group with conventional cushions and an experimental group with customized cushions. The saturation level of peripheral oxygen, apnea-hypopnea index, leakage data, and answers to a comfort questionnaire were examined. ResultsCustomized and conventional cushions were compared with independent sampling t tests and relational analyses. A significant difference was found in the apnea-hypopnea index (P=.001) of participants with the customized cushion and those with the conventional cushion. Participants with the conventional cushion had a lower apnea-hypopnea index. The customized cushion applied less headgear force and fit better than the conventional cushion. The leakage volume, saturation of peripheral oxygen (SpO2), treatment compliance, and degree of comfort were not significantly different between the groups. ConclusionsCustomized nasal mask cushions fit better and reduce the force applied by the headgear. Participants using a customized cushion showed an improved apnea-hypopnea index.

Corner Foam Versus Flat Foam: An Experimental Comparison on Cushion Performance

Most cushion structures used in the industry are end caps, edge or corner foam. The bearing area and thickness of the cushioning obtained from cushion curves apply, in principle only, to flat foam because the specimens used to develop the cushion curves are flat foam samples. This study is aimed at finding the difference between the two foams in stress–strain relationship and dynamic impact. A hysteresis cycle compression test, in conjunction with digital image correlation techniques, and a shock cushion test were performed to assess the static stress and strain, energy dissipated and maximum acceleration of flat and corner foams. The study found that the static stress of the corner foam that occurred during the compression testing is 23% higher in average than the flat foam, depending on the compression speed. The shock cushion curve of the corner foam showed a similar pattern as the flat cushion curve but was shifted horizontally to the right as a result of the increased static stress. This study recommends that the conventional cushion curve should be shifted to the right horizontally by about 23–35% in order for a packaging designer to apply it for corner foam. Copyright © 2014 John Wiley & Sons, Ltd.

Hierarchical Agglomerates of Carbon Nanotubes as High-Pressure Cushions

We report the cushioning behavior of highly agglomerated carbon nanotubes. The nanotube agglomerates can be repeatedly compacted to achieve large volume reduction (>50%) and expanded to nearly original volume without structural failure, like a robust porous cushion. At a higher pressure range (10-125 MPa), the energy absorbed per unit volume is 1 order of magnitude higher than conventional cushion materials such as foamy polystyrene. The structure of hierarchical agglomerates can be controlled for tailoring the cushioning properties and obtaining a lower cushioning coefficient (higher energy absorption) over a wide range of pressures (1-100 MPa). The mechanism was studied in terms of morphology evolution of the nanotube aggregates and pore size distribution during compression.

Development of Hybrid Energy-Absorbing Reusable Terminal for Roadside Safety Applications

The hybrid energy-absorbing reusable terminal (HEART) is a newly developed crash cushion or end terminal to be used in highway safety applications to mitigate injuries to occupants of errant vehicles. HEART is composed of corrugated plates of high-molecular weight, high-density polyethylene (HMW-HDPE) supported on steel diaphragms that slide on a fixed rail. Kinetic energy from errant vehicles is converted to other energy forms through folding and deformation of the HMW-HDPE material. Many previous designs utilized plastic or permanent deformation of plastics or steels to accomplish this goal. However, HEART is a combination of plastic and steel that forms a largely self-restoring and largely reusable crash cushion. Consequently, HEART has a major life-cycle cost advantage over conventional crash cushion designs. HEART was developed through extensive use of finite element analysis with LS-DYNA. The simulation approach adopted for the development of HEART, construction details, and a description and result...

Development of Hybrid Energy-Absorbing Reusable Terminal for Roadside Safety Applications

The hybrid energy-absorbing reusable terminal (HEART) is a newly developed crash cushion or end terminal to be used in highway safety applications to mitigate injuries to occupants of errant vehicles. HEART is composed of corrugated plates of high–molecular weight, high-density polyethylene (HMW-HDPE) supported on steel diaphragms that slide on a fixed rail. Kinetic energy from errant vehicles is converted to other energy forms through folding and deformation of the HMW-HDPE material. Many previous designs utilized plastic or permanent deformation of plastics or steels to accomplish this goal. However, HEART is a combination of plastic and steel that forms a largely self-restoring and largely reusable crash cushion. Consequently, HEART has a major life-cycle cost advantage over conventional crash cushion designs. HEART was developed through extensive use of finite element analysis with LS-DYNA. The simulation approach adopted for the development of HEART, construction details, and a description and results of crash tests performed so far to evaluate its performance are presented. Also discussed is some of the follow-up work currently under way for approval of HEART by FHWA as an acceptable crash cushion for use on the National Highway System.

Consolidation of cushion curves

AbstractA simple method for the consolidation of all of the conventional cushion curves for a particular material into a single relationship is discussed. The method requires only one of the usual cushion curves for an arbitrary drop height and cushion thickness to deduce the dynamic stress‐strain curve for the material. The results can then be used to generate all other cushion curves regardless of drop height, cushion thickness, or static loading. The procedure is applied to the published sets of cushion curves for Arcel® 512 and for expanded polystyrene, separately, and the predicted shock values for various drop conditions are then compared with the actual values from the cushion curves. The error incurred in using the consolidated data instead of the cushion curves is shown to fall within the limits of accuracy associated with the cushion curves themselves. The method offers many advantages, such as compactness of information, a continuous range of application, greater compatibility with computer aided cushion design, and a sizeable reduction in the number of drop tests required to generate new cushion performance data.

Protective helmet with voice communication system

An improved protective helmet of the type including a two-way voice controlled communication system having electronic transmitting and receiving circuitry. When incoming signals are received by the voice communication system, a transducer vibrates a rigid portion of the helmet, causing the helmet to act as a diaphragm to produce intelligible audible sounds. The electronic circuitry of the voice communication system is mounted in a resilient carrier for protection against damage from impact and shock to the helmet. Alternatively, the electronic circuitry may be supported on and protected by the conventional cushion lining of a protective helmet.