Browsing by Author "Yu X."

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Analysis of back forces while sitting down, seated, and rising from a stationary chair in subjects weighing 136–186 kg
(2017-01-01) Hu L.; Tor O.; Zhang J.; Tackett B.; Yu X.
Limited research was found related to the study of back forces on chairs sat on by people who weighed over 136 kg. The Business Institutional Furniture Manufactures Association needs force data for development of performance test standards to test chairs for users who weigh up to 181 kg. 20 participants who weighed from 136 to 186 kg completed six tasks on an instrumented chair in the sequence of sitting down, remaining seated, and rising. Effects of sitting motion, armrest use, and seat cushion thickness on back forces and centre-of-force were investigated. Results indicated hard sitting down yielded the highest back force of 34.7 % in terms of participants’ body weights. Armrest use and cushion thickness affected back forces of normal sitting down, but not of rising, hard sitting down, and remaining seated.
Cushioning Capability Analysis of Seat Foundations Considering the Sitter’s Anthropometric Dimensions
(2020-01-01) Hu L.; Tor O.; Shen L.; Zhang J.; Quin F.; Yu X.
Sitting comfort is primarily determined by the cushioning capability of the seat foundation. Limited literature has been found related to the effects that different sized human buttocks had on the cushioning capability of the seat foundation. Moreover, there is no testing method specialized to measure the load-deformation behavior of foam cushions that imitates the sitting behavior between indenters with different sizes and seat support. This study investigated the effects of various indenter diameters (20 cm, 30 cm, 36 cm, 41 cm, 51 cm, and 58 cm), foam stiffness levels (high and low), and seat bases (spring versus solid flat panel) on the compressive load-deformation behavior of upholstered seat foundations. The load-deformation curves of all the tested foam-seat base combinations exhibited three typical regions, i.e., linear elasticity, plateau, and densification, when subjected to the loads applied through different indenter diameters. Statistical results indicated that the primary effects of the indenter diameter, foam stiffness level, and seat base had significant effects on the spring constants, which represented the slopes of lines in these three regions. In addition, a regression technique was proposed to derive power equations for the estimation of the spring constants of a seat foundation as a function of the indenter diameter, foam material stiffness, and seat base type.
Cyclic behavior of self-tapping screwed laminated Bamboo Lumber connections subjected to cycle loadings
(2019-01-01) Chen C.; Ye Z.; Yu X.; Tor O.; Zhang J.
Self-tapping screws are commonly used to connect critical structural components, such as legs to rails in chair construction, using laminated bamboo lumber (LBL) materials. The loosening of a connection is commonly seen in self-tapping screwed LBL connections before actual breakage of connections happens. The loosening of connections, especially those associated with chair legs, can significantly affect chair stability. Current furniture performance test standards have not address this issue, i.e., the minor loosening of a connection is not treated as a failure in the current standard because of the lack of better understanding the load-rotation-time behavior of various connections subjected to the cyclical loads. The effects of cyclic loading magnitude and orientation on the load-rotation-time behavior of L-shaped, end-to-side, single self-tapping screwed LBL connections were investigated. Results indicated that the Burger and Kelvin models could be used to describe the cyclic and recovery behavior of studied connections. Increasing the cyclic loading magnitude resulted in a decreasing trend for all viscoelastic constants. The most significant decrease in all viscoelastic constants occurred when the cyclic loading magnitude applied to connections increased from 50 to 60% of its corresponding ultimate static resistance loads.
Effect of body mass index on sitting pressure distribution on seat cushion
(2019-01-01) Hu L.; Tor O.; Duan P.; Zhang J.; Yu X.
The pressure distribution between a seat and people is a very important index in the assessment of sitting discomfort for seat cushion. However, limited research has been found for the relationship between pressure distribution and anthropometric dimensions, especially for Body Mass Index (BMI) of users with different sizes. Effects of BMI ranges (underweight, normal and obese) and cushion hardness (medium, firm, extra firm and wood board) were the factors investigated in this study. The results indicated that the normal participant had a higher comfort degree than the obese and underweight participants. The obese participant preferred the extra firm foam cushion compared to normal participants who preferred the medium foam cushion.
Factors affecting critical screw-driving torques in particleboard
(2019-08-01) Tor O.; Yu X.; Demirel S.; Hu L.; Zhang J.
Factors influencing the vertical driving force magnitude applied to screws during the process of driving the screws into faces of particleboard materials were investigated. In particular, the screw penetration depth and screwdriver air pressure were evaluated relative to critical torques, such as seating and stripping torques. Experimental results indicated that vertical driving forces significantly affected the magnitude of critical driving torques when no pilot hole was drilled, but this influence became non-significant when 3.2-mm diameter pilot holes were drilled. Screw-driving power had no significant effect on the magnitude of critical driving torques in particleboard materials if no pilot hole was drilled, but if pilot holes were drilled, increasing the screwdriver air pressure from 0.45 to 0.62 MPa led to increases in stripping torques. Increasing the screw penetration depth from 12.7 to 19.1 mm can significantly increase seating and stripping torques.
In-plane bending moment resistance of t-shaped one-sided two-gusset-plate furniture joints in oriented strandboard
(2016-07-01) Demirel S.; Yu X.; Tor O.; Zhang J.
This study investigated the in-plane bending moment resistance of a T-shaped joint connected with two gusset plates stapled on one side of joint members in three oriented strandboard (OSB) materials. Experimental results indicated that in-plane moment resistance loads of T-shaped, one-sided, two-gussetplate joints at ultimate point on average were about 1.9 times their corresponding moment loads at proportional limit. The proposed mechanical model was verified experimentally as a valid means for deriving estimation equations of in-plane bending moment resistance loads of T-shaped, one-sided, twogusset- plate joints in OSB materials used in this study. Experimental results and derived equations of in-plane bending moment resistance loads indicated that a T-shaped, one-sided, two-gusset-plate joint in OSB materials will always have a higher in-plane bending moment resistance load than an L-shaped one if the rail width in a L-shaped joint is the same as the stump width in a T-shaped joint. The difference in magnitude was affected by the critical joint member width and distance from the point on the stump at which the external in-plane moment load was applied to the rail top edge.
Lateral loads of stapled⇓glued surface-to-surface joints in oriented strandboard for furniture
(2018-01-01) Demirel S.; Tor O.; Yu X.; Zhang J.
The additive effects of the number of staples and gluing on ultimate lateral resistance loads of surface-to-surface, multistaple- and glue-connected joints in oriented strandboards (OSB) were investigated. Experimental results indicated that for a stapled–glued OSB joint with a given configuration of surface-to-surface bonding area of two joint members, its ultimate lateral resistance load and stiffness are governed by the number of staples used and gluing, respectively. Applying glue to multistaple-connected OSB joints can alter the effect of the number of staples used on their ultimate lateral resistance loads. Gluing increases joint lateral resistance loads, but this increase will not be significant when the number of staples used reaches a critical number. Applying glue to a stapled OSB joint improves its stiffness when compared with the stiffness of a stapled-only joint. The differences in ultimate lateral resistance loads of stapled–glued joints among three OSB materials evaluated in this study were not significant when the number of staples was six or less, and the differences became significant when the number of staples increased to eight.
Support factor of upholstered seat cushions
(2020-01-01) Zhu Y.; Shen L.; Tor O.; Zhang J.; Liu L.; Yu X.; Hu L.
Polyurethane foams are commonly used in the upholstered seat cushions, providing a sitter with a comfort sitting experience. According to the foam testing standard of American association for material testing, the compression testing for sofa cushions with two layers of foam were conducted to investigate the effects of the elastic modulus of upper and lower foams on the support factor of seat cushion. The results indicated that the interaction of elastic modulus of upper and lower foams has significant influence on support factor. The support factor is significant higher when the foam with elastic modulus of 0.19 MPa was used as the upper layer, which means those foam cushions had good support performance. In addition, a regression technique was proposed to drive power equation for the estimation of support factor as a function of elastic modulus of upper and lower foams for sofa seat cushion.