Seat-interface pressures on various thicknesses of foam wheelchair cushions: A finite modeling approach

Ragan, Robert; Kernozek, Thomas W.; Bidar, Mani; Matheson, James W.

doi:10.1053/apmr.2002.32677

Cited by 66 publications

(38 citation statements)

References 7 publications

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“…This results in three distinctive elastic responses before, during, and after buckling occurs. This behavior was reported in Ragan et al [9] and Todd et al [10] for FRPU. The three phases are appropriately termed bending, buckling, and collapse, and they are identified on Figure 2.…”

Section: Non-linear Elasticity Measurementssupporting

confidence: 83%

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Mechanical-Thermal Simulation of Passenger-Loaded Vehicle Seat in Severe Winter Conditions

Chan¹,

Karimi²,

Rose³

et al. 2004

SAE Technical Paper Series

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This paper presents a comprehensive steady-state numerical study for an occupant-loaded vehicle seat with internal heating under severe winter conditions. A participant-based postural study showed that the nominal peak occupant seat pressure was 6kPa on the seat cushion, and 2.5kPa on the backrest. Uni-axial compression tests also indicated non-linear stress-strain behaviors in seating. Using an internally developed 3-D numerical model, it was found that the thermal resistance from contact and clothing was uniform (h c =144W ¡K 1 ¡m 2 ) throughout the occupied regions. Their contribution to the overall thermal resistance was relatively minor, however, compared to that of skin (h overall =27.2W¡K 1 ¡m 2 ).The thermal-mechanical simulations were conducted at heat input levels between 20W and 80W , using I-DEAS 10 and the TMG package as the simulation platform. Comparisons was also made between occupied seat with deflected and non-deflected mesh. The occupant deflection helped reduce the thermal resistance in the occupied region, which resulted in a slight decrease in heater temperature, accompanied by an increase in the average surface temperature, compared to corresponding undeformed results.

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Section: Non-linear Elasticity Measurementssupporting

confidence: 83%

“…The effective properties, 15 in total, were assigned to each contour level. Meanwhile, the Poisson's rations for all materials were assigned a value of 0.1 [9].…”

Section: Mechanical Simulationmentioning

confidence: 99%

Mechanical-Thermal Simulation of Passenger-Loaded Vehicle Seat in Severe Winter Conditions

Chan¹,

Karimi²,

Rose³

et al. 2004

SAE Technical Paper Series

View full text Add to dashboard Cite

show abstract

“…Some of the basic assumptions of the Hertz model, e.g., the elasticity of the two contacting bodies, the relatively small area of contact in comparison to the size of the bodies themselves, the elasticity of the deformations, and the absolute smoothness of the contacting surfaces, are, to put it mildly, inaccurate when describing the body [57]. It is therefore almost surprising that the overall results of the model are very plausible in comparison to other state-of-the-art investigations [37,39,54,[62][63][64]. The explanation may lie in the fundamental nature of the model and the ease with which it accepts corrections (Appendix).…”

Section: Discussionmentioning

confidence: 95%

Toward real-time detection of deep tissue injury risk in wheelchair users using Hertz contact theory

Agam

Gefen²

2008

JRRD

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Abstract-This study assessed the suitability of a new portable system that is based on Hertz's contact theory for evaluating internal gluteal muscle stresses under the ischial tuberosities of wheelchair users in real-time as a risk indicator for a deep tissue injury. Sitting in a wheelchair was monitored and processed with the portable system for six control subjects and five individuals with paraplegia. We compared the resultant internal peak and average muscle stresses and stress integrals over time (stress doses) of the control subjects with those of the subjects with paraplegia and validated the results against previously published subject-specific finite element (FE) stress data for the same subjects. Individuals with paraplegia were characterized by peak muscle compression stresses (mean +/-standard deviation = 109 +/-41 kPa) that were 2.4-fold higher than in control subjects (p < 0.03). A Bland-Altman comparison indicated that stresses recorded by the present system were in satisfactory agreement with previous subject-specific magnetic resonance imaging-FE analyses. We conclude that the present stress monitoring system has the potential to be a practical means for evaluating internal muscle stresses during everyday life of individuals with paraplegia.

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“…The elastic behaviour of the EVA mattress support is known to be highly nonlinear. However, over the range of stresses encountered in this study (3 kPa-30 kPa), the response was linear, and the Young modulus of the EVA foam was set at 30kPa, with a Poisson ratio of 0.1 based on previous findings [10]. The Shape A and Shape B models were meshed using SOLID185 elements as shown in Fig.…”

Section: Finite Element Analysismentioning

confidence: 99%

Finite Element Analysis and Empirical Analysis of a Cost-effective Pressure Ulcer-Preventing Mattress

Lai

Guo

2015

AUSMT

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Pressure relief mattresses are recommended to prevent pressure ulcers (PU). Passive mattresses offer a cost advantage over dynamic mattresses. This study evaluates a new passive PU-preventing mattress. Finite element analysis was used to determine the curved surface design of a mushroom-shaped support. A novel mattress evaluation platform was developed integrating a pressure mapping sensor, laser doppler flowmetry (LDF) and precise temperature sensors to validate the effectiveness of the new passive mattress. Compared with standard hospital mattresses, the new passive mattress was found to provide a more even body pressure distribution (relative disparity of -0.7%) and better assisted subcutaneous blood flow (relative disparity of 18.78%). Experimental results demonstrated that the new passive mattress can provide an effective and economical solution for preventing PU.

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Seat-interface pressures on various thicknesses of foam wheelchair cushions: A finite modeling approach

Cited by 66 publications

References 7 publications

Mechanical-Thermal Simulation of Passenger-Loaded Vehicle Seat in Severe Winter Conditions

Mechanical-Thermal Simulation of Passenger-Loaded Vehicle Seat in Severe Winter Conditions

Toward real-time detection of deep tissue injury risk in wheelchair users using Hertz contact theory

Finite Element Analysis and Empirical Analysis of a Cost-effective Pressure Ulcer-Preventing Mattress

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