Seat Structure Research Articles

Advanced seating comfort: suppression of vibration using multi-mode piezoelectric shunt damping

The transmission of seat structural vibration to the human body contributes to vibration discomfort particularly near the resonant frequencies (> 10 Hz). The conventional methods of controlling vehicle seat vibration may no longer be used on lightweight seat structures efficiently. Here, a new control method derived from multi-mode shunt damping using piezoelectric patches is proposed and is implemented on a vehicle seat to suppress the transmission of seat vibration to the occupant's body by controlling the seat foam vibration. The results indicate that the proposed method is effective for controlling seat vibration at the resonant frequencies of the seat. The application of the piezoelectric shunt damping system holds some promise for the future development of lightweight vehicle seats with enhanced ride comfort.

Numerical investigation into the cavitating jet inside water poppet valves with varied valve seat structures

Owing to the strong three-dimensionality and transient evolution, the flow dynamics of a cavitating jet inside a water poppet valve is poorly understood, leading to insufficient basis for exploring the governing mechanism of cavitation effects. In this paper, a three-dimensional simulation considering the compressibility of each constituent phase is performed, to clarify the governing mechanisms under the cavitating flow inside two water poppet valves. The cavitation structures inside the poppet valves are primarily located at three regions and triggered by different mechanisms. The vortex cavitation, mainly confined within the free shearing layer, is due to vortex dynamics, while the attached cavitation at the poppet trailing edge and within the chamfered groove arises from flow separation. The fast laminar–turbulent transition process contributes to the three-dimensionality within the free shearing layer and the rear part of the chamfered groove. The flow separation due to the chamfered groove leads to increased velocity of the central potential core, contributing to a different flow discharge performance from that of the poppet valves with a sharp seat. In addition, the periodic variation in cavitation reveals the significant interaction between the shed cavitating vortex and attached cavitation at the poppet trailing edge. In conclusion, the change in velocity distribution due to different poppet valve seat structures leads to variation in flow discharge performance, and the vortex dynamics makes sense for all three kinds of cavitation occurring inside poppet valves.

Modeling and analysis of car seat rubber bush using CATIA for reducing vibration in passenger engine vehicles

The fatigueness due to the long driving by the driver in the passenger vehicle like car is experienced due to the low frequency vibration occurring in the IC engines. It is been mainly occurring in the driver seat and hence to reduce the vibration transferred to the driver through the seat. The car seat has been measured with the amount of vibration magnitude and the analysis of seat structure using the CATIA. The modeling of the seat bush is done by using the 3D printer three different type of car seat bushes is made with the nylon, ABS and polyurethane the material properties like the tensile and hardness are tested and in addition to it the dynamic characteristics of the stiffness and damping properties are studied using the CATIA and the properties are compared.

Combined with finite element analysis of car seat safety performance improvement

Neck injuries caused by low-speed rear-end collisions are a worldwide problem. The reasonable design of car seat can effectively prevent or reduce the passenger neck injuries. In this paper, the finite element analysis (FEA) and whiplash test are combined to optimize the seat structure parameters to enhance the safety. The whiplash test results of the existing car seats according to C-NCAP (2015) were matched with FEA, and the optimization scheme was developed by computer simulation. For the improvement of seat safety, the optimizations are applied to determine backrest stiffness, backrest rotational stiffness, headrest rotational stiffness and headrest stiffness. The retest results of optimized seat show that its safety performance is greatly improved. Furthermore, it shows that the combination of finite element analysis and whiplash test can optimize seat structure to improve safety performance.

Design and analysis of engine mount for biodegradable and non-biodegradable damping materials

In the present automotive world high importance is given to the comfort and safety of the passenger. The comfort to the passenger signifies many terms such as the seating structure, leg space, air conditioning etc. The most important thing is that all the vehicles are subjected to vibrations such as from the engine or from external factors. The vibrations produced from the engine are transferred to the entire vehicle structure and this is reduced by placing engine mounts between the engine and the chassis. Designing the proper type of mount holds the key for effective reduction of vibrations. In this article a new design of the engine mount is proposed and taken into finite element analysis. Also, material for the mounts are considered to play a vital role. In this along with two regular materials, a biodegradable material is also used for the dampers. More importance is given to the frequency response of the mount for different materials and the finite element analysis is performed for a four-cylinder inline engine with two mounts on either side.

Modelling and Validation of the Composite Shell of a Train Seat

The subject of the modelling work and the conducted experiments is the composite shell of a train seat. The activities carried out involved designing the geometry, planning the material structure, and selecting the materials to be used. The shell was built using polymer matrix fibrous composites (i.e. FRP – Fibre Reinforced Polymer – composites), which are lighter than steel and comply with the relevant standards for strength and safety at the same time. This was followed by creating a computational model for the shell and conducting a strength analysis in accordance with the guidelines of the relevant industry standard and strength hypotheses adopted for FRP composites. The calculations were conducted using ANSYS Composite PrepPost software based on the finite element method. The article offers a strength analysis of an optimised composite shell of a train seat. Based on the guidelines obtained as a result of the conducted modelling work, a physical prototype (validation model) of the seat was created. Hot vacuum lamination technology was applied in the production process. The experimental validation of the model, producing a positive result, was conducted using a test stand owned by S.Z.T.K. TAPS – Maciej Kowalski. Keywords: train seat structure, FRP composite, FEM modelling, experimental validation

A three-phase QFD-based framework for identifying key passenger needs to improve satisfaction with the seat of high-speed rail in China

This study aims to suggest a three-phased methodological framework based on the operational approach of quality function deployment (QFD) to improve the service quality and passenger satisfaction with China’s high-speed rail (HSR) by identifying the key passenger needs with regard the HSR seats. For the first phase, the collection of the voice of the customers/passengers (VOC), the processing of the collected VOC into need items and further into passenger needs of QFD would be explained in terms of knowledge management. For the second phase, a reference comparison-based fuzzy best–worst method is developed for determining the relative importance of passenger needs, with a particular purpose of coping with the uncertainty and ambiguity associated with qualitative assessment of respondents. For the third phase, the importance-performance analysis is performed to determine the improvement priorities for meeting passenger needs. Findings showed that Body-friendly seat structure and Reasonable layout of the seat are the two most important needs demanded by the passengers of second-class cabins, with the former being the top priority. The current study provides useful references for service operators of HSR to formulate development strategies for improving the seat comfortability, which subsequently contributes to improving HSR’s service quality and passenger satisfaction. Moreover, the proposed methodological framework for identifying the important passenger needs can be appropriately adjusted and expanded to similar transportation infrastructures and facilities.

Analysis and Optimization of automotive seat structure based on finite element method

According to the rigid design standard of automotive seat frame structure, the strength and stiffness of a vehicle seat is analyzed and optimized in this paper. The finite element analysis results show that the initial design of the seat can basically meet the stiffness requirements under most standard test conditions. However, in the front crash test condition, there is a risk of strength failure in the seat rail. Therefore, it is necessary to optimize the structure. Based on the engineering experience, local characteristics of the seat rail is modified. After conducting simulation of the improved seat structure, it is demonstrated that the seat meets all the design requirements of stiffness and strength.

Design optimization of a business aircraft seat considering static and dynamic certification loading and manufacturability

A conceptual design for a lightweight business aircraft seat was developed using topology optimization in a 2-stage approach to consider both the static and dynamic certification test requirements of the Canadian Aviation Regulations (CARs) Section 525.561 and 525.562, respectively. Preliminary optimization was performed using static load requirements, and the interpretation of the optimization results was done considering key manufacturability metrics to reduce the cost of manufacturing components when using traditional subtractive manufacturing methods. A series of explicit dynamic models was run to predict the behavior of the seat during 14g and 16g certification tests and to estimate the maximum loads which the anthropomorphic test device (ATD) applies to the seat structure. Peak seatbelt loads were estimated at 9060 N and 8955 N for the left and right sides, respectively, and the asymmetry of the loads can be attributed to the 10° yaw of the aircraft required by the 16g certification test. Topology optimization was used to refine the design at the component level and further reduce weight using the loads determined in the dynamic modeling. The final conceptual design was 32% lighter when compared with the baseline structural components, and key manufacturability cost metrics were reduced by 24%.

Structure design of LFT passenger car seat structure based on topology optimisation

The newly revised GB 13057-2014 ‘The strength of the seats and their anchorages of passenger vehicles’ replaces the static test with a dynamic test, which puts forward higher requirements on seat safety. Considering safety and lightweight design, the LFT (Long glass Fiber reinforced Thermoplastic) is used to replace the original steel seat back frame. Combined with energy absorption model and topology optimisation, the force transmission path and detail structure design under both the forward loading and rearward loading conditions are carried out. In order to analyse the occupant protection performance, numerical models of composite seat and HybridIII dummy are established, and the safety and lightweight effect of LFT seat back frame are optimised and verified.

Countermeasures design and analysis for occupant survivability of an armored vehicle subjected to blast load

The demand for blastworthy structures increases due to a large number of casualties in the armored vehicle undergoing improvised explosive device (IED) and landmine attacks. In this research, the numerical studies on the countermeasure analysis to reduce injury biomechanics risk were conducted. The available experiment data of occupant survivability test on a medium size tank was used to validate the numerical model. The subsystem evaluation in this study included the finite element modeling of military personnel, seat system, surrounding interior system, seatbelt, and restraint system with four running conditions. The military personnel inside the armored vehicle was modeled by using Hybrid III 50th percentile anthropomorphic test device (ATD) and its biomechanical response was monitored on the head, neck, thorax, spine, femur, and tibia. The load case for this study referred to NATO STANAG 4569 level 3b with 8 kg TNT explosive load underbelly. The injury assessment reference values (IARV) for the regulation used in this study were based on AEP-55 volume 2. Based on this study, the critical injuries identified on the head injury, neck compression, and tibia axial load. The solid frame as part of seat structure appeared to contribute to an excessive kinematic on the lower extremities. The vehicle acceleration resulted from the load blast was directly transmitted to the lower extremities, resulting in unintended kinematic and interaction on the passenger body. The proposed solutions were to introduce a flexible mounting for the seat system and as well increasing the height of the footrest to avoid direct transmission of vehicle acceleration. The modified countermeasure design reduced significantly head, neck, and tibia injury criteria more than 90 % from the baseline design (existing design). The new anti-mine seat design successfully passed all the standard regulation thresholds of injury criteria.

Geological and Geoelectrical Investigation of a Proposed Dam Site Using Vertical Electrical Sounding at Osuworowo Stream, Utughughu Arochukwu, South Eastern Nigeria

Geophysical studies was carried out at a proposed dam site across Osuworowo stream in Arochukwu, south eastern Nigeria to investigate the depth to bedrock, possible geologic structures and foundation conditions of the dam axis. The study area is located between latitudes 5°23.58”N and 5°23.707”N and longitude 7°53.93”E and 7°53.97”E. Its elevation ranges from 90 ft to 149 ft. Six Vertical Electrical Soundings (VES) were carried out along the stream course using ABEM SAS 1000 TERRAMETER and this was done using Schlumberger configuration with maximum half current electrode separation of 55m able to reveal deep seated structures. The ip2win software was used to model the VES data to give resistivities which vary between 258 Ωm and 39000 Ωm with three and four geoelectric layer combinations of sand, sandstone, sandyshale, shalysand and ale units. The high resistivities of the geoelectric layers sand thickness and dip showing high gradient in elevation differences are indications that the site is suitable for the dam construction. The geological result shows the presence of faults this is confirmed by change in strike and dip.

Passive Safety System for Side Impact in Cars

The ultimate aim of this work is to provide the safest ride for the peoples. The following contribution is to protect the precious life of the driver and the co-passengers during the accidents by increasing the distance between the impact zone and the passengers, peculiarly during the crash on the sides. This can be achieved by incorporating a pneumatic cylinder under the seats, which is then actuated by the solenoid valve triggered by the deformation caused by the crashing vehicle. This makes the seats tilted at the time of the accident away from the near side of the door, which saves the life. The high-pressure energy in the container gives ultimate kinetic energy using high velocity gives a sudden actuation of seats in a fraction of seconds clearly say 0.3 seconds. We have re-designed the structure and mechanism of car seats to make it possible to save precious lives. Our design idea does not stop with single possible way of saving the life, it extends to lot of customization and adaptability based on the car structure and available space specific to various brands and models.

Optimisation design of CFRP passenger car seat backplane based on impact characteristics

The newly revised GB 13057-2014 put forward high requirements for the dynamic occupant protection of passenger car seats. Due to the high density of steel, there is currently not much space for lightweight through structure improvement. In this paper, the quasi-static and dynamic mechanical properties of CFRP and corresponding simulations are used to study the mechanical behaviour of CFRP and verify the accuracy of simulation. It is now applied to the composite seat backplane structure design, and combined with the CFRP moulding process and the energy absorption characteristics of the car seat backplane to initially design the CFRP seat backplane material and structure. At the same time, considering the designability of the material itself, the ply optimisation technology under multi-condition is used to design the material and structure of the CFRP passenger car seat backplane. The new CFRP passenger car seat achieves significant weight reduction while meeting regulatory requirements.

A seated human model for predicting the coupled human-seat transmissibility exposed to fore-aft whole-body vibration

Occupant discomfort, induced by vibration transmitted through a vehicle seat, can be evaluated by measuring vibration on the contact interface between the occupant and seat. In the previous study (Ittianuwat et al., 2016), measuring five contact points of the back-backrest, including centre point (ISO 2631-1), was considered as an important factor for assessing occupant comfort in frequencies where seat structure resonances occur. To enhance occupant vibration comfort in the early seat design stage, predicting the dynamic response of the coupled human-seat system on various contact locations is necessary. In this study, a low order seated human body Finite Element (FE) model was developed for predicting vibration transmissibility of the human-seat system in frequencies up to 30 Hz. Throughout the optimization process, the parameters of the model were obtained by comparing measured transmissibilities of the occupied vehicle seat system. The human-seat system vibration modes were also compared and verified with measured data by calculating MAC (Modal Assurance Criterion). The results showed that two human body vibration modes coupled with foam were observed below 10 Hz, and two coupled human and seat structure fore-aft modes were observed at around 20.1 Hz and 21.9 Hz. Fore-aft transmissibility of the model at various locations of contact provided reasonable correlation with the measured data. The developed low order human model enables the prediction of the fore-aft transmissibility on various back-backrest contact locations up to 30 Hz. This showed the capability of improving occupant's vibration comfort by predicting transmissibilities of the human-seat system in the early stage of developing a new vehicle seat.

A numerical investigation of factors affecting lumbar spine injuries in frontal crashes

Recent field data analyses have shown that lumbar spine fractures occurred more frequently in late model vehicles than the early ones in frontal crashes. Therefore, the objective of this study was to investigate risk factors associated with lumbar spine fractures in frontal crashes.Parametric simulations were conducted using a set of validated vehicle driver compartment model, restraint system model, and a HIII mid-size male crash test dummy model. Risk factors considered in the study included occupant seating posture, crash pulse, vehicle pitch angle, seat design, anchor pre-tensioner, dynamic locking tongue, and shoulder belt load limiter. ANOVA and ANCOVA were used to test the statistical significance (p < 0.05).Simulation results showed that all the factors that reduced the risk of submarining increased the lumbar spine forces, indicating a direct conflict between submarining and lumbar spine fractures. Among all the factors selected, seat structure is the most significant factor in determining the lumbar spine force (p < 0.001). Crash pulse severity, time at which the peak crash deceleration reached, and pitch angle are also crucial for lumbar spine force. Specifically, increase in vehicle pitch angle increased lumbar spine force, but reduced injury measures to other body regions; while a crash pulse with early peak produced greater lumbar spine force than that with a late peak. On average, more reclined posture increased the lumbar spine force compared to upright posture, and decreases in the coefficient of friction between the pelvis and the seat cushion reduced the lumbar spine force. However, they are not statistically significant.This study provided better understanding of effects from design countermeasures to reduce occupant lumbar spine injuries in new generation of vehicle models.

Loading of the Musculoskeletal System of a Person While Driving in a Passenger Car

The damping of these dynamic effects is solved by the vehicle suspension system. All this is then reflected in the safety of driving, the driving characteristics of the vehicle, but also in the response to the locomotive apparatus of the vehicle crew. Cervical injuries are usually caused by the inertia of the head. Although the product of speed and weight (kinetic energy) are proportional to the values that increase the likelihood of neck or head injury. It is surprising that significantly more injuries occur at slow speeds. The force effects transmitted to the cockpit always affect the body of the person controlling the vehicle. In the long term, one-sided loading of the organism negative impact on human health, in rare cases can lead to death. The main aim of the article was to measure the dynamic effects that are transmitted to the driver (co-driver) when driving in a passenger car over obstacles. The measurement was carried out experimentally in a real environment on a designated road at different driving speeds and different distribution of obstacles on the road. Acceleration sizes generated on the driver/co-driver seat structure, under the buttocks, head and cervical vertebrae C7 were sensed by acceleration sensors. The result of the work was to find out how much dynamic effects are transmitted from the vehicle structure to the driver/co-driver body, respectively. the head and vertebra of the cervical spine C7 (vertebrae cervicales) as the vehicle crosses obstacles.

Impact of upholstered furniture seat structures on the long-term use comfort

Impact of upholstered furniture structures on the comfort of long-term use. The main objective of the study was to analyze the impact of changes to the structures of upholstered seating furniture to measure the comfort of new furniture and after long use. Tests were conducted with the use of a Force Sensitive Applications sensing mat to record contact pressure, and a profiled cavity pressed into the seat with a force of 760 N. The period of 5 years of long-term use was simulated by the cyclic load of 1000 N x 25,000 repetitions. Based on the analysis of the test results obtained, a decrease in the discomfort factor D by 12.7% for seat I and 11.5% for seat II was observed. This means an increase in the feeling of comfort in using these seats during the period of use. This is associated with a decrease in seat stiffness. Seats with less rigidity ("softer") cause less pressure on the human body due to the larger usable area.

Effect of the Q10 dummy upgrade kit in UN Regulation No. 129 front and side impact tests

Objective: The objective of this study was to compare the kinematics and dummy loadings between the original Q10 and the Cellbond Q10 upgrade kit and determine the effect of the kit on the type approval of booster systems in United Nations (UN) Regulation No. 129.Methods: Front and side impact pilot experiments were carried out according to dynamic test procedures in UN Regulation No. 129. In each case, the original Q10 and Q10 upgrade kit were compared in a booster seat.Results: In front impact, the Q10 and Q10 upgrade kit displayed very similar kinematics and seat belt interaction. The peak dummy loads were also very similar. In side impact, the Q10 and Q10 upgrade kit displayed similar kinematics and interaction with the side structure of the booster seat. Once again, the peak dummy loads were also very similar.Conclusions: The original Q10 and the Q10 upgrade kit generated very similar kinematics and loadings in both front and side impact. Adoption of the kit for UN Regulation No. 129 would be unlikely to have significant effects on the type approval of booster seats. However, it would also appear not to offer any specific benefits. This will be verified in a larger program of experiments with a broader range of booster systems.

Structure Optimization of Infrared Guidance Testing Device Based on Orthogonal Test

As an important weapon, missiles cannot be ignored in its fighting capacity. Therefore, the performance testing of the missile is particularly important. The hardware in the loop simulation test using missile test equipment on the ground can reduce the cost and improve the utilization rate; it is of great significance for the development of national defence construction. In the process of missile testing, the parts under the force of deformation will reduce the accuracy of the device, therefore the light pipe support needs sufficient strength and stiffness. In this paper, the finite element method was used to analyse the structure of the optical tube support seat, and the orthogonal test was used to optimize it. The test results were analysed by the range and variance to find out the optimal level combination and the significant influence of each factor in the result. At end, the appropriate structure of the program was determined. Comparing with the original structure, the strength and rigidity of the optical tube support seat have been greatly improved. Device accuracy has also been improved.