Browsing by Author "Tor O."

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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.
Analysis of Sitting Pressure Distribution on Office Chair for Occupants with Different Body Mass Index
(2021-01-01) Li X.; Zhang T.; Shen L.; Tor O.; Zhu Y.; Zhang J.; Chilufya C.; Yan B.; Hu L.
The pressure distribution is one of popular objective measurements for sitting comfort, but a few studies were found for the pressure distribution between subjects with different body mass index and office chair. The effects of sitting posture, body mass index, gender, and the types of office chair (adjustable and non-adjustable) on sitting pressure distribution were investigated in this study. 18 subjects with different body mass indexes (overweight, normal weight and under weight) completed five different sitting postures in the order of forward-watching screen, forward-writing, backward-typing, backward-bow one’s head, and backward-cross legged. The outcome demonstrated that the seat adjustable or not, the type of sitting posture has significant influence on the average pressure, maximum pressure gradient and pressure distribution uniformity. Gender and body mass index have significant effects on the circular pressure gradient. Results of sitting pressure distribution obtained in this research, could strengthen the particularity of the body shape consideration in the design of office chairs.
Bending characteristics of laminated wood composites constructed with black pine wood and aramid fiber reinforced fabric
(2021-01-01) Karaman A.; Yildirim M.N.; Tor O.
The aim of this study was to determine the 4-point bending strength and modulus of elasticity in bending of Black pine wood laminated materials reinforced with aramid fiber was bonded using epoxy or polyurethane glues separately. The samples were prepared in accordance with the TS 5497 EN 408 (2006). The results of the study determined that the highest value for static bending strength was found in the laminated wood samples (83.94 N.mm-2) that were prepared using inter-layer aramid fiber reinforced polymer (AFRP) and epoxy glue. The highest value of modulus of elasticity in bending was found in the samples prepared with inter-layer epoxy and AFRP (10311.62 N.mm-2). It was observed that the samples parallel to the glue line of the laminated material showed higher performance compared to those perpendicular to the glue line. The data obtained as a result of this study demonstrated that aramid fiber reinforced Black pine wood laminated materials can be used in the building industry as building materials.
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.
Effects of factors on direct screw withdrawal resistance in medium density fiberboard and particleboard
(2020-01-01) Yorur H.; Birinci E.; Gunay M.N.; Tor O.
An increase in demand on solid wood that is insufficient supply to meet in the world necessarily directed to other engineering materials that could be an alternative to the solid wood. In this context, instead of using solid wood in furniture and construction industry, wood-based panels such as medium density fiberboard (MDF) and particleboard (PB) have become widely used as construction material. Limited research has been done in the field of fastener performance as mechanical properties with different parameters in the joints constructed with these panels. Therefore, in this study, the parameters of screw type, pilot hole, screw orientation, water treatment and adhesives were investigated in MDF and PB. The results indicated that the highest direct screw withdrawal (DSW) resistance was observed in the test blocks applied with PU and the lowest DSW resistance was in the test blocks without a pilot hole drilled in both materials. In addition, MDF in general had better DSW resistance than PB in almost all combinations of the parameters. The treatment of water into MDF and PB test blocks negatively affects the DSW resistance. The DSW resistance in the face orientation was found to be higher than the corresponding ones in the side orientation in both materials.
Effects of Pilot Hole Diameter and Depth on Screw Driving Torques in Plywood
(2020-01-01) Tor O.; Birinci E.; Hu L.; Chen C.
Factors affecting screw driving torques in plywood were investigated in this work. The factors were number of layers (7 and 9), pilot hole diameter (3.0 and 3.5 mm), pilot hole depth (60 and 80% of the thickness of specimen), and thickness of the metal plate (7.5 and 10 mm). Screw driving torques were studied in oriented strandboard, medium-density fiberboard, particleboard, and some wood-plastic composites. There is no such information about screw driving torques in plywood (PW). Therefore, this study focused on the plywood made of aspen (Populus tremula L.). The mean seating torque (SET) values ranged from 0.31 to 0.69 N∙m, whereas mean stripping torque (STT) values ranged from 0.50 to 4.7 N∙m. The ratios of STT/SET were between 2 and 5 in PW with seven layers, whereas the ratios were between 4 and 7 in PW with nine layers. The results indicated that the four main effects of SET and STT were statistically significant with p-values of ˂ 0.0001.
Effects of pilot hole diameter on screw-driving torques in medium density fiberboard
(2019-01-01) Tor O.; Tor, O
This study investigated the effects of pilot-hole diameter in medium density fiberboard (MDF) on the characterization of screw-driving torques. The factors investigated were the embedded screw orientation and pilot hole diameter. Based on the curves obtained from screw-driving process, the measurements of the seating torque (SET) and stripping torque (STT) were obtained. The results of statistical analysis indicated that the SET and STT values in MDF were significantly affected by the pilot hole diameter. In the case of driving screws into the side of MDF material, the mean SET ranged from 0.37 to 1.23 N·m and STT values ranged from 1.18 to 2.68 N·m whereas for the face specimens, the mean SET ranged from 0.57 to 1.56 N·m and STT values ranged from 2.89 to 5.41 N·m.
Effects of pilot hole diameter on screw-driving torques in medium density fiberboard
(2019-01-01) Tor O.
This study investigated the effects of pilot-hole diameter in medium density fiberboard (MDF) on the characterization of screw-driving torques. The factors investigated were the embedded screw orientation and pilot hole diameter. Based on the curves obtained from screw-driving process, the measurements of the seating torque (SET) and stripping torque (STT) were obtained. The results of statistical analysis indicated that the SET and STT values in MDF were significantly affected by the pilot hole diameter. In the case of driving screws into the side of MDF material, the mean SET ranged from 0.37 to 1.23 N·m and STT values ranged from 1.18 to 2.68 N·m whereas for the face specimens, the mean SET ranged from 0.57 to 1.56 N·m and STT values ranged from 2.89 to 5.41 N·m.
Ergonomics of a Chinese Folk Bamboo Lounge Chair
(2020-01-01) Cheng Y.; Tor O.; Hu L.; Zheng W.; Yu Y.
Bamboo is an environmentally friendly sustainable resource and is commonly used in furniture production in China. Limited research has been conducted in the field of ergonomics of bamboo furniture, which can greatly affect the seating experience. This study provides a qualitative and quantitative analysis of the main effects of seat surface curve, bending deflection of bamboo strips of seat, functions, and usability in a bamboo lounge chair provided in Zhejiang Province. The shape of the seat surface curve of the bamboo lounge chair included the seat-back angle of 134°, and the slope of the bamboo lounge chair seat was 16°. The deflection of bamboo strips of seat under vertical loading force of 336 N was 30.7 mm. In addition, the angles, deflection characteristic, and functions of the bamboo lounge chair were all human-centered design and suitable for human comfort, which can reduce maximum pressure and maintain normal lumbar spine curve in adult.
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.
Some Properties of White and Torrefied Pellets Obtained from Oil Palm Trunk as Raw Material
(2022-01-01) Chotikhun A.; Kittijaruwattana J.; Pianroj Y.; Tor O.; Birinci E.; Hengniran P.; Lee S.H.
Properties of unheated wood pellets were compared with those of torrefied wood pellets that had been heated to 270, 290, and 310 °C, with raw material taken from two different height levels of oil palm trunk (OPT). The gross calorific value, moisture content, ash content, volatile matter, fixed carbon, density, and weight loss were examined. Air drying or oven drying pretreatment was applied to the raw materials. The results showed that the heating values of samples increased when raw materials were torrefied, depending on the heat treatment temperature. The torrefied pellets were improved by as much as 66.4% in heating value compared with OPT pellet samples. The greatest improvement was found in torrefied pellet samples prepared at 310 °C, using air drying, and height levels of OPT between 0.3 to 1.5 m. The ash content of samples tended to increase when the torrefied temperature was increased, while the volatile matter value was reduced with high temperature. Based on the findings, OPT could be used as a raw material to produce value-added white and torrefied pellets as sustainable solid biofuel.
Static lateral load capacity of extruded wood-plastic composite-to-metal single-bolt connections, considering failure at the ends
(2019-01-01) Chen C.; Kuang F.; Tor O.; Quin F.; Xiong Z.; Zhang J.
The effect of the end distance was studied relative to the static ultimate lateral load capacity of a single-shear unconstrained wood-plastic-composite-to-metal single-bolt connection (SUWSC). Equations estimated the static ultimate lateral loads of the SUWSCs that failed during the end tear-out, splitting, and yield modes and were obtained using stress concentration factor regression- and mechanics-based approaches. The experimental results showed that the stress concentration factor was a linear function of the end-distance to bolt-diameter ratio for the SUWSCs that failed during end tear-out and splitting modes. The static ultimate lateral loads of the SUWSCs that failed during the yield modes were estimated using a mechanics-based equation. The minimum end distance for the SUWSCs that failed without end fracture (i.e., only with yield mode) was 25.4 mm, which was four times larger than the bolt diameter.
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.
Ultimate direct withdrawal loads of low shear strength wooden dowels in selected wood species for furniture applications
(2019-01-01) Chen C.; Xing Y.; Xu W.; Tor O.; Quin F.; Zhang J.
The wood dowel pin is one of the common fasteners for connecting structural members in wooden furniture frame construction, such as chairs. The effects of dowel penetration depth, shear strengths of connection member and dowel materials, dowel surface texture, and member grain orientation on ultimate direct withdrawal loads of single dowels withdrawn from wooden materials were investigated. The main findings were that the connections using dowels and main members with low shear strength properties achieved the same ultimate direct withdrawal loads with connections using the materials with higher shear strength properties for dowels and main members. Additionally, the existing empirical equations, including shear strength properties for both dowel and main member materials used to construct dowel connections, tended to remarkably underestimate the ultimate direct withdrawal loads of the evaluated dowel connections withdrawn from the end and side grains of the tested wood species. The connection main members in this study when these two shear strength values were added together was less than 25 MPa. Both estimation expressions were modified to consider the lower shear strength effort on ultimate direct withdrawal loads of dowels evaluated in this experiment.