Seat Strength Research Articles

Verification of Automotive Monopost Seat Strength through Dynamic and Quasi-Static Simulations

A monopost seat is a novel, lightweight seat developed to utilize most of the interior space of vehicles. The space under the seat can be utilized by inserting a monopost columnar structure between a monopost seat rail and the floorboard. This design increases the perceived spaciousness of the vehicle and imparts passengers with a higher degree of freedom, because the seats can be adjusted more easily than standard seats. Meeting these requirements will require the seats to be sufficiently strong and sturdy in order to maintain passenger safety. Compared to traditional seats, it is more likely that a monopost seat will shift under the mass of the passenger, and these seats are more vulnerable to external vehicle collisions. Passenger safety is further compromised if an operational function is added. Therefore, further research on monopost seats is required. This study performed quasi-static and dynamic simulations to determine if the attachment of monopost seats to a vehicle meets international safety requirements in collision events. With a focus on clarifying the dynamic simulation process, the outcomes of quasi-static simulations were compared with the results obtained from dynamic simulations.

Quasi-static methods to evaluate seat strength in rear impacts

Objective Various methods have been used in the past 50 years to apply Quasi-static load to a seat in the rear direction and measure seat performance in rear impacts. This study compared five of the most-common test procedures to evaluate seats. In addition, occupant mass and center of gravity are discussed as important characteristics of rear loading of seats. Method Data was collected and analyzed from five different seat pull tests, including FMVSS 207, modified FMVSS 207, QST, body block and FRED II. Test data included peak force, moment and angle at peak moment. Occupant loading height of was determined using body segment weights and position in the forward (x) and vertical (z) directions based on anthropometry data. Results Some of the inherent differences in the tests are shown by comparing data with the same seat structure. The QST and FRED II use a lower height of loading than FMVSS 207. The QST and FRED II peak moment and force did not coincide with the same seatback angle as in FMVSS 207 and body block testing. Center of gravity height varies depending on whether the whole body or only the upper torso is considered. For the 50th male, it is 171.5 mm (6.8”) with the whole body and 246.7 mm (9.7”) with the upper torso. Conclusion Results from different tests cannot be readily compared because of different loading conditions, including body shape and height of load about the H-point, which can cause the seat structure to respond differently.

An Assessment of the Kick Tolerance Calculation, Its Uncertainty, and Sensitivity

Summary Much of the contemporary literature on kick tolerance relates to the practical aspects of the calculation and the effects of the underlying assumptions and necessary simplifications. It tends to a formulaic approach involving unconstrained uncertainties about pore pressure, kick intensity, drilling fluid density safety factors which tend to overlook the inherent complexities of the subsurface environment, and the reality of model limitations. The literature on kick tolerance highlighting the strengths, weaknesses, and limitations of the classic calculation is reviewed before describing a first-principles approach to determining the consequences which casing seat strength limitations and strength variations in the overall openhole section impose on safe well designs as a result of uncertainties in the input variables and basic model assumptions. The classic kick tolerance calculation, together with its associated assumptions, yields only a single value for a given set of inputs. The uncertainties and sensitivities are those introduced by the variables and the choice of operational procedures. The Monte Carlo method is used to explore the effect of uncertainties in the input parameters and associated assumptions. The analysis is based on the driller’s method for kick circulation, with a single-bubble insoluble gas with optional allowances for gas gravity and thermal regimes. To examine the various factors influencing kick tolerance, the problem is framed graphically in terms of an allowable influx volume, the dependent variable, against bottomhole pressure (BHP), the independent variable, on which pore pressure, its uncertainty, possible variations in shoe strength, strength in the openhole section, drilling fluid density with associated equivalent circulating density (ECD) and swab effects can be examined. Application of the new approach demands significant prior work to determine the uncertainties inherent in the problem. Some of these uncertainties, such as drilling fluid density variations, swabbing, and ECD, must be evaluated by the engineer as part of the normal well design. Other factors, such as shoe strength, pore pressure variability, and formation depth error bars must be developed as part of a multidisciplinary effort within the planning team. Often ignored due to the spatial uncertainties, natural fractures intersecting the borehole could be inherently unstable and prone to hydraulic communication between borehole and formation. Synthesizing some of these considerations into a simple calculation framework allows the effect of these parameters either individually or collectively to be quantified and provides a view of the potential geological uncertainties inherent in a well design. The approach offers a starting point for thinking about the nature of geological uncertainties and carrying them into drilling programs.

A more reasonable model for submarines rescues seat strength analysis

The paper presents the rescue systems of submarines used worldwide. The idea of rescue seats was explained and described. The seat's load caused by the pressure of hydrostatic pressure, the thrust of the rescue vehicle, and the sea current was defined in accordance with the requirements of STANAG 1297. According to the standard, an analysis of the stress state of a Kobben-class submarine rescue seat loaded with the pressure of an emergency vehicle was carried out. The sea current and hydrostatic pressure at a depth of 700 m were taken into account. Non-linearities related to the description of the material and large deformations were used. Johnson-Cook characteristics for HY-80 steel are described. The stress state results in a Kobben-class submarine rescue seat obtained based on FEM simulations for a submersion depth of 700 m are presented. The results are shown in two variants. Variant I - following the standard, Variant II – author's proposal. Then differences were demonstrated, and additional recommendations were proposed.

Calculation of sealing joints with elastic edge in PTC MathCAD

The article touches upon the issues of the development of engineering methods of calculating a thin-walled shell-plate seat for valve and flange sealing joints, followed by the formulation of tasks using modern automated calculation software. To achieve the purpose, the authors used Parametric Technology Corporation MathCAD (PTC MathCAD) with subroutines for the search for extremum of functions and the computational block ‘Given - minimize’. The calculation is presented in the form of algorithms consisting of three logically interrelated parts: 1) stiffness calculation; 2) strength calculation; 3) the calculation of rational dimensions. The obtained results of the calculation of geometric dimensions are tested, which eliminates a probable error in the calculated block ‘Given’ of PTC MathCAD. Among the developed engineering methodologies, the article describes the following ones: a method for calculating the rational geometrical dimensions of a shell-plate valve seat, operating under shock loading at an uncertain maximum dynamic load. It ensures that the allowable stresses in a thin-walled shell-plate seat are not exceeded. Another is a method for testing the stress-strain state of a shell-plate valve seat under static loading with a force of sealing and pressure of the working medium. The last one is the method of calculating rational geometrical dimensions of the shell-plate seat of a flange connection, which minimizes the unit stiffness (minimizing sealing force), provided that the shell-plate seat strength is ensured.

Occupant responses in conventional and ABTS seats in high-speed rear sled tests

ABSTRACTObjective: This study compared biomechanical responses of a normally seated Hybrid III dummy on conventional and all belts to seat (ABTS) seats in 40.2 km/h (25 mph) rear sled tests. It determined the difference in performance with modern (≥2000 MY) seats compared to older (<2000 MY) seats and ABTS seats.Methods: The seats were fixed in a sled buck subjected to a 40.2 km/h (25 mph) rear sled test. The pulse was a 15 g double-peak acceleration with 150 ms duration. The 50th percentile Hybrid III was lap–shoulder belted in the FMVSS 208 design position. The testing included 11 <2000 MY, 8 ≥2000 MY, and 7 ABTS seats. The dummy was fully instrumented, including head accelerations, upper and lower neck 6-axis load cells, chest acceleration, thoracic and lumbar spine load cells, and pelvis accelerations. The peak responses were normalized by injury assessment reference values (IARVs) to assess injury risks. Statistical analysis was conducted using Student's t test. High-speed video documented occupant kinematics.Results: Biomechanical responses were lower with modern (≥2000 MY) seats than older (<2000 MY) designs. The lower neck extension moment was 32.5 ± 9.7% of IARV in modern seats compared to 62.8 ± 31.6% in older seats (P =.01). Overall, there was a 34% reduction in the comparable biomechanical responses with modern seats. Biomechanical responses were lower with modern seats than ABTS seats. The lower neck extension moment was 41.4 ± 7.8% with all MY ABTS seats compared to 32.5 ± 9.7% in modern seats (P =.07). Overall, the ABTS seats had 13% higher biomechanical responses than the modern seats.Conclusions: Modern (≥2000 MY) design seats have lower biomechanical responses in 40.2 km/h rear sled tests than older (<2000 MY) designs and ABTS designs. The improved performance is consistent with an increase in seat strength combined with improved occupant kinematics through pocketing of the occupant into the seatback, higher and more forward head restraint, and other design changes. The methods and data presented here provide a basis for standardized testing of seats. However, a complete understanding of seat safety requires consideration of out-of-position (OOP) occupants in high-speed impacts and consideration of the much more common, low-speed rear impacts.

Seat strength in rear body block tests

ABSTRACTPurpose: This study collected and analyzed available testing of motor vehicle seat strength in rearward loading by a body block simulating the torso of an occupant. The data were grouped by single recliner, dual recliner, and all belts to seat (ABTS) seats.Methods: The strength of seats to rearward loading has been evaluated with body block testing from 1964 to 2008. The database of available tests includes 217 single recliner, 65 dual recliner, and 18 ABTS seats. The trends in seat strength were determined by linear regression and differences between seat types were evaluated by Student's t-test. The average peak moment and force supported by the seat was determined by decade of vehicle model year (MY).Results: Single recliner seats were used in motor vehicles in the 1960s to 1970s. The average strength was 918 ± 224 Nm (n = 26) in the 1960s and 1,069 ± 293 Nm (n = 65) in the 1980s. There has been a gradual increase in strength over time. Dual recliner seats started to phase into vehicles in the late 1980s. By the 2000s, the average strength of single recliner seats increased to 1,501 ± 335 Nm (n = 14) and dual recliner seats to 2,302 ± 699 Nm (n = 26). Dual recliner seats are significantly stronger than single recliner seats for each decade of comparison (P < .001). The average strength of ABTS seats was 4,395 ± 1,185 in-lb for 1989–2004 MY seats (n = 18). ABTS seats are significantly stronger than single or dual recliner seats (P < .001). The trend in ABTS strength is decreasing with time and converging toward that of dual recliner seats.Conclusions: Body block testing is an quantitative means of evaluating the strength of seats for occupant loading in rear impacts. There has been an increase in conventional seat strength over the past 50 years. By the 2000s, most seats are 1,700–3,400 Nm moment strength. However, the safety of a seat is more complex than its strength and depends on many other factors.

A static test method to assess swivel seat strength in frontal impact

Mechanical swivel seat adaptations are a key aftermarket disability modification to any small- to medium-sized passenger vehicle. However, the crashworthiness of these devices is currently unregulated and the existing 20g dynamic sled testing approach is prohibitively expensive for prototype assessment purposes. In this paper, an alternative quasi-static test method for swivel seat assessment is presented, and two different approaches (free-body diagram and multibody modelling) validated through published experimental data are developed to determine the appropriate loading conditions to apply in the quasi-static testing.Results show the two theoretical approaches can give similar results for estimating the quasi-static loading conditions, and this depends on the seatbelt configuration. Application of the approach to quasi-static testing of both conventional seats and those with integrated seat belts showed the approach to be successful and easy to apply. It is proposed that this method be used by swivel seat designers to assess new prototypes prior to final validation via the traditional 20g sled test.

Strength Analysis of the Seat Structure for Large Passenger Vehicles by Using Finite Element Method

Presently, large passenger vehicles are known to have high risk of an injury due to accident and insufficient of safety regulation. The strength of seat is one of important issues that affect to injury level of passenger. Therefore, suitable structure strength and design of the seat are very important to prevent injuries and passenger life. This study was to evaluate strength of the seat structure for bus according to preliminary safety regulation of Department of Land Transport. Finite element analysis is employed by using a static load. The seat model was simplified and simulated. Stress and impact scenario between seat-back and back of manikin will be investigated. The strength and deflection of the seat will be evaluated. This study is expected to provide the seat model which will be safe and satisfied according to the regulation.

C’est en forgeant qu'on devient forgeron? Assessing legislative productivity in Fifth Republic France

This exploratory research note theorises about and tests the factors that have affected legislative productivity in France from 1960 to 2007. The empirical model accounts for intra-parliamentary dynamics such as the parties’ ideological placement on a left-right scale, the government's seat strength, coalition governments and intensity of opposition to the majority in the National Assembly. The model also considers features unique to the Fifth Republic, such as judicial review of bills by the Constitutional Council and presidents’ ‘sacking’ of prime ministers. External factors include strikes and social movements, as well as prime ministers’ and presidents’ job approval that are posited to impact lawmaking. The results of the analysis suggest how the model developed in this research may be extended to future analyses of parliamentary activity in the Fifth Republic.

Design of Strength of the Seats and Head Restraints Testing System

designed a equipment for testing the strength of seats and head restraints, the equipment can testing the seats and head restraints with the standard of GB 11550-1995 5.2. The equipment was composed of one upper cylinder elevating system, a beam elevating system, two load cylinders and a hydraulic station. In addition to designed the principle of the hydraulic system.

Evaluation of the effectiveness of a bus and coach seat during rear end impact by means of sled tests

Based on data from statistical accident analysis, buses and coaches are still one of the safest means of transportation. Nevertheless numerous occupants get injured or suffer fatal injuries due to accidents. Although a high proportion of seriously injured casualties happen in accidents where the bus overturns or leaves the road, a large number of injuries are caused due to a normal collision, like a head-on or rear end impact. ECE regulation 80, referring to the strength of seats and their anchorages, was the initial starting point for this investigation. This regulation is limited to seat testing for frontal collisions, while this study deals with the results of testing in the opposite direction. Numerous coaches, especially double decker coaches, also have rearward facing seats and have consequently a different kind of loading to the seat structure. Summarizing, the results of the sled tests show a potential for further improvements in the energy absorption and design of the coach seat structure, to minimise the injury risk in such an accident configuration.

Evaluation of the effectiveness of a bus and coach seat during rear end impact by means of sled tests

Abstract Based on data from statistical accident analysis, buses and coaches are still one of the safest means of transportation. Nevertheless numerous occupants get injured or suffer fatal injuries due to accidents. Although a high proportion of seriously injured casualties happen in accidents where the bus overturns or leaves the road, a large number of injuries are caused due to a normal collision, like a head-on or rear end impact. ECE regulation 80, referring to the strength of seats and their anchorages, was the initial starting point for this investigation. This regulation is limited to seat testing for frontal collisions, while this study deals with the results of testing in the opposite direction. Numerous coaches, especially double decker coaches, also have rearward facing seats and have consequently a different kind of loading to the seat structure. Summarizing, the results of the sled tests show a potential for further improvements in the energy absorption and design of the coach seat structure, to minimise the injury risk in such an accident configuration.

Report investigating the importance of head restraint positioning in reducing neck injury in rear impact

Neck injury resulting from rear impact (often known as whiplash) is a serious cause of road trauma. It is often underestimated or overlooked because such injuries are minor on traditional injury scales but can result in long term pain and disability. The paper begins with a brief review of research into head restraints and whiplash done so far. A review of international head restraint regulations revealed the absence of any horizontal offset requirements. A review of seat strength requirements and testing procedures showed that a regulation that required a collapsible seat would involve significant compliance testing. This paper concludes a preliminary project conducted by the Federal Office of Road Safety (FORS) where the head restraints for twenty Australian market vehicles were assessed using known performance criteria. A key finding of the report was that most of the vehicles allowed for vertical adjustment of the head restraint. Also important was that none of the vehicles measured allowed horizontal adjustment and on some of the head restraints the horizontal displacement increased as the vertical height increased. As the understanding of neck injury mechanisms in rear impact develops, there may be some scope for FORS to facilitate the improvement of these standards. Further research into neck injury mechanisms may reveal yielding seat backs or new ‘active’ head restraint technology as a more effective countermeasure. In the meantime, educating occupants to correctly adjust their head restraints seems to be an effective way to reduce injuries in existing vehicles.

Crashworthiness analysis of commuter aircraft seats and restraint systems

Abstract During the past five years, the U.S. Federal Aviation Regulations (FARs) have been significantly modified with respect to strength of seats and restraint systems, their attachments to the aircraft structure, and the means for their evaluation. Aircraft accident data, human tolerance levels, and aircraft structural characteristics have been considered in developing the new standards, which require dynamic testing of seats and restraint systems. FAR Part 23, which deals with small airplanes, was first amended to require dynamic testing of seats and restraint systems for normal and utility (general aviation) aircraft with capacity for fewer than 10 passengers. Performance criteria are similar to those specified by the U.S. Federal Motor Vehicle Safety Standards for automobiles, but also include a limit on pelvic force in order to prevent spinal injuries that may be caused by the vertical component of impact force. Similar regulatory actions, although requiring somewhat different dynamic test conditions, have also been implemented for transport aircraft, which are covered by FAR Part 25, and for helicopters, under FAR Parts 27 and 29. Commuter-type aircraft have not been affected by the FAR modifications. Commuter types seat 10 to 19 passengers, are closer in size to general aviation aircraft than to large transports, and are also covered by FAR Part 23. The Federal Aviation Administration (FAA) is currently involved in a research program that includes full-scale aircraft drop tests, sled tests of seats, and computer simulations that should lead to a proposal for amendment of the regulations for commuter-type aircraft. The objectives of this paper are to describe the research program and to document some conclusions that may be drawn from its results concerning seat and restraint system design, dynamic testing, and acceptance criteria.