Browsing by Author "Hu L."

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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.
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.
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 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.
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.
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.