Virtual optimisation of car passenger seats: Simulation of static and dynamic effects on drivers’ seating comfort

The virtual investigation of static and dynamic effects on seating comfort requires the application of an adequate human model. An appropriate seat model considering static and dynamic properties of the structure, the foam and the trim is needed to perform an optimisation for a lower load level on the driver. The evaluation of the seating comfort must be divided into a static and a dynamic part. For the computation of the relevant physical quantities with the human model CASIMIR and a detailed seat model, the finite-element solver ABAQUS (ABAQUS Inc., http://www.abaqus.comwww.abaqus.com) is used.

To reflect a real driving situation, in the first step the human model is adapted to the right posture, which is given by the inclination of the cushion and the backrest. The seating process is then computed by the load due to gravity. The static comfort is mainly evaluated by the seat pressure distribution. Results such as the H-point and the meat-to-metal value can give additional important informations for the ergonomic and structural design of the seat. As the model reflects the nonlinear properties and the finite-element solver considers the effects out of finite displacements and contact, a good correlation with measurement is achieved.

The dynamic simulation is carried out by a unit excitation of the seat slides at the clamping points. To consider frequency-dependent properties of foam, structure and the human body, the computation uses an implicit solver. Therefore the model is linearised after the nonlinear static seating process.

Dynamic comfort is evaluated by the seat-transfer function. The presented numerical method leads to a good correlation with the measurements. Superposing the results with real excitation signals enables the estimation of the dynamic loads as muscle or intervertebral disc forces on the driver.

Altogether this method, in an early state of the development enables the user to optimise a car passenger seat structure due to the static and dynamic comforts. Considering boundary conditions as higher load amplitudes and accelerations, the advantages of virtual development can also be applied for construction vehicle seats.

Relevance to Industry

The present method allows the evaluation of static and dynamic comforts in a virtual phase of seat development. Besides the reduction of time and costs, the application of the simulation enables the testing of new materials and ways of construction with low investment.     

Metallschichten für langlebige Strukturen

For the steady growing of the miniaturisation in the interconnection technique new basic materials with improved quality must be available. The new generation for the flex materials affords high reliability for many applications that are characterized for example by high temperature, high humidity and aggressive chemicals surroundings.     

Properties of thin In2O3 and SnO2 films prepared by corona spray pyrolysis, and a discussion of the spray pyrolysis process

Thin films of doped In₂O₃ and SnO₂ were prepared by the “corona spray pyrolysis” technique with a deposition efficiency of 80%. The electrical and optical properties of the films were determined. A transmission of 88% in the visible region and an IR reflection of more than 90% were the maximum values obtainable for a doped In₂O₃ film.

A detailed discussion of the physical and chemical processes that occur during spray pyrolysis is presented to aid the understanding of this coating technique.

A minimum temperature of about 350°C for the formation of In₂O₃ was empirically confirmed.

Furthermore the powdery precipitate obtained during deposition of In₂O₃ was clearly identified as polycrystalline In₂O₃ formed by a homogeneous reaction.     

Standards-software reliability handbook: achieving reliablesoftware

The results to date of a three-year research effort on software reliability engineering sponsored by the American Institute of Astronautics and Aeronautics (AIAA) are discussed. After a standard for recommended practice for software reliability estimation was approved by the AIAA, a blue-ribbon panel of industry experts was convened to consider the future of reliable software and software technology in space systems. The panel's work towards a software reliability engineering database and research in software reliability tools and software reliability models are discussed. The software reliability recommended practice, its intended audience, and its users are reviewed     

Microstructural Evolution of Dissimilar Metal Welds Involving Grade 91

Metallurgical and Materials Transactions A - Dissimilar metal weld failures between low alloy Cr-Mo ferritic steels and austenitic stainless steels made with Ni-base filler metals are typically...     

Pharmacokinetics and metabolism of the new thromboxane A2 receptor antagonist ramatroban in animals. 1st communication: absorption, concentrations in plasma, metabolism, and excretion after single administration to rats and dogs

The absorption, concentrations in plasma, metabolism and excretion of ramatroban ((+)-(3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9- carbazolepropanoic acid, CAS 116649-85-5, BAY u 3405) have been studied following a single intravenous, oral, or intraduodenal administration of 14C-labeled or nonlabeled compound to rats and dogs (dose range: 1-10 mg.kg-1). After intraduodenal administration of [14C]ramatroban, enteral absorption of radioactivity was rapid and almost complete both in bile duct-cannulated male rats (83%) and female dogs (95%). The oral bioavailability of ramatroban was complete in the dog but amounted to about 50% in the rat due to presystemic elimination. A marked food effect on the rate but not on the extent of absorption was observed in rats. The elimination of the parent compound from plasma occurred rapidly with total clearance of 1.2 l.h-1.kg-1 in male rats and 0.7 l.h-1.kg-1 in dogs. After oral administration to male rats AUC increased dose-proportionally between 1 and 10 mg.kg-1, whereas in Cmax an over-proportional increase was observed. Excretion of total radioactivity was fast and occurred predominantly via the biliary/fecal route in both species. The residues were low, 144 h after dosing less than 0.2% of the radioactivity remained in the body of rats. A considerable sex difference was found in rats following oral administration of ramatroban. In females a 3-fold higher AUC and a 1.7-fold longer half-life of unchanged compound, as well as 3-fold higher renal excretion of total radioactivity was observed. A marked species difference exists in the metabolism of ramatroban. In dogs the drug was almost exclusively metabolized via conjugation with glucuronic acid, whereas in rats oxidative phase I metabolism and glucuronidation were equally important. As a consequence enterohepatic circulation was much more pronounced in dogs (77%) than in rats (17% of the initial dose).     

EFFECT OF EXCHANGEABLE CATIONS ON HYDROPHILIC NATURE OF KAOLIN AND BENTONITE*

The affinity for water of a kaolinite-type clay (kaolin) and a montmorillonite-type clay (bentonite), saturated with hydrogen, calcium, sodium, and potassium, was studied by three methods, namely, heat of wetting as determined by calorimetric measurements, sorption of water from the vapor phase by weighing, and desorption or removal of water by differential-thermal analysis. It was shown that hydrogen and calcium clays had a greater affinity for water than sodium and potassium clays. Although the bentonite evolved more heat and sorbed more water per gram of clay, it evolved less heat and sorbed less water per milliequivalent of exchangeable cation than did the kaolin; the differences in the effects of various cations were more pronounced in bentonite than in kaolin. The results may be explained as follows from considerations of the mineral structures: (1) A greater amount of water hydrates the surface of kaolinite in proportion to that hydrating the exchangeable cations than is the case in montmorillonite and (2) the exchangeable cations may be hydrated to a greater degree (i.e., less strongly held) on kaolinite than on montmorillonite.