Side Members Research Articles

FE Modeling for Bolted Wood Connection Using a Porous Constitutive Model

According to the facts of localized crushing failure of bolt groove in wood connection with enough end distance and the three‐phase composites of wood with solid (wood substance), water, and gas, a confined compression test for the wood cylinder was conducted for achieving constitutive relation under the complex stress state in wood groove. A porous constitutive model was developed according to the confined compression experiments. Then, the constitutive model was implemented in a finite element modeling of mental dowel‐type fasters in wood‐to‐wood connections to analyse the load‐carrying capacity parallel to the grain. Through changing the thicknesses of centre members and side members of wood connections made of a similar wood species, Pinus Sylvestris var. Mongolica, the effects of thickness combinations of centre members and side members on the failure modes and load‐carrying capacity of bolted wood connection including numerical simulations and experiments were compared. The failure modes, including the yielding of centre member, the yielding of side member, and the yielding of the bolt, as well as the rigid rotation of the bolt, all reappeared by the finite element modeling with the porous constitutive model. The predicted deformation shapes and load‐displacement relations of bolted wood connections were compared with experimental ones, and good correlations were observed. This paper presents a new approach to simulate the local embedment crushing of bolt groove in wood connections.

A gradient boosting approach with diversity promoting measures for the ensemble of surrogates in engineering

Ensemble of surrogates has shown to be effective in the modeling of a variety of engineering problems, from aerospace to automotive and oil and gas industries, among many others. The ensemble performance though can be negatively affected by the lack of diversity (correlated errors) among the members of the ensemble, i.e., similar errors throughout the input space. During the last decade, ensemble research efforts in engineering have mostly focused on the so-called ensemble integration (combining prediction) phase with, for example, linear weighted averages of surrogate predictions based on performance (error) measures of both local and global natures. On the ensemble generation side (members of the ensemble), the emphasis has been on promoting diversity through the so-called heterogeneous ensembles, that is the use of different learners (surrogates), such as, linear regression, radial basis functions, kriging, support vector regression, and neural networks. Because of the lack of control on diversity in heterogeneous ensembles, potentially correlated error among the learners remains a critical issue. This paper presents an alternative approach based on homogeneous ensembles (single learning algorithm) that promotes diversity both implicitly and explicitly, by randomly sampling the training data and deterministically changing the data supplied to each surrogate model in the ensemble generation process. Specifically, it includes decision trees as learners, subsampling of the training set, and training on random selections of the input features, i.e., random subspace. The ensemble is sequentially constructed as an additive model where at each stage a simple surrogate is fit to the negative gradient of the loss function at the training data of the latest ensemble (gradient boosting). In addition, as a by-product of the modeling process, the proposed approach provides importance measures to preliminary rank input features. Statistically significant prediction improvements over heterogeneous ensembles were observed in a variety of well-known analytical test functions and industrial case studies in the areas of petroleum engineering-net present value of oil production in a mature reservoir and structural analysis-FSAE brake pedal von Mises stress and buckling load factor.

Contribution of Face and Core Layers to Lateral Load Resistance of Single-Shear Metal-to-Particleboard Single-Screw Connections

The lateral load-slip behavior of a single-shear metal-to-particleboard single-screw connection (SMPSC) was investigated. The connection consisted of a layered particleboard main member fastened to a metal plate as a side member using a 4.8-mm diameter sheet metal screw. A mechanics-based approach was used to evaluate critical factors on the lateral load resistance performance of SMPSCs. Experimental results indicated that ultimate screw-bearing strengths in face and core layers of evaluated particleboard materials were 100.0 and 29.9 MPa, respectively. This significant difference of screw-bearing strength in material layers significantly affected the lateral resistance load capacity of SMPSCs. The proposed mechanical models considering material layer effects on screw-bearing strengths were verified experimentally as a valid means for deriving estimation equations of lateral resistance loads of SMPSCs evaluated in this study.

Hydro-Forming Process Design of Automotive Sub-Frame Side Members for Securing Stiffness by Application of Cross-Sectional Groove

Hydro-Forming Process Design of Automotive Sub-Frame Side Members for Securing Stiffness by Application of Cross-Sectional Groove

Lateral strength of nailed timber connections with decay

Loading tests were conducted on nailed connections with decay due to a brown rot fungus. The effect of the decay on the lateral strength of nailed connections was investigated. After loading tests, the sound and decayed regions of a nailed connection were observed in the cross section, which was cut parallel to the grain through the nailed point. The nailed connections with decay showed a low load during initial deformation when the main and side members had a decayed region in the boundary between them. The nailed connections showed low load after yielding when the sound region in the main member decreased. The yield load of nailed connections with decay was calculated based on the yield theory. The model of calculations had sound and decay regions within a member. The yield load of nailed connections obtained by the calculation based on the yield theory agreed with the results obtained by experiments when significant decay in a direction parallel to the grain was observed in the main and side members. This result indicates that the yield theory can estimate the yield load of nailed connections not only with a sound member, but also a member that is partly or wholly decayed.

Hydro-Forming Simulation of Automotive Sub-Frame Side Members

Hydro-Forming Simulation of Automotive Sub-Frame Side Members

Design of a half cut side member structure for optimal car crash energy absorption characteristics

The front side members of a car play a vital role in energy absorption for improved occupant safety during a crash. The response of side members with a half cut structure was examined with a parameter study. The structural design variables were the number of edges of the polygonal cross section, the spot welding spacing, and the thickness of the thin-walled side member structure. An optimal design method for the half cut side member was developed to maximise the absorbed energy by applying a response surface optimisation method. An objective function was used to maximise the energy absorbed by the side member structure. The mass of the optimal side member was constrained to be less than an allowed value.

Design of a half cut side member structure for optimal car crash energy absorption characteristics

Design of a half cut side member structure for optimal car crash energy absorption characteristics

Energy Absorption Due to Oblique Impact Crushing of Thin-Walled Tubes

From the viewpoint of improving both the crash safety and the fuel efficiency, various shaped thin-walled tubes have been utilized as energy absorbers of automobiles such as front side members, crash boxes and so forth. In the axial crushing test of the regular polygonal tube, if the number of angles was small enough, it showed a certain inherent wrinkle mode, and the mean buckling load increased with that number, while it showed the mode of cylindrical tube if that number became larger. In the oblique crushing test, the same tendency was also shown within the range that the transition from axial collapse to bending collapse did not occur. This transition considerably decreases the mean buckling load so that it is important to know the threshold crush angle for the transition. Then, the crushing behavior of regular 4-12 angled tubes were investigated with changing the crush angle mainly by the experiment. The threshold angle is sensitively influenced by the initial imperfection and the boundary condition so that both the threshold angles obtained by the experiment and by the calculation for the square tube are 8-13° smaller than that predicted by the equation proposed by Han and Park. For the carbon steel S25C, the increase of the strain rate in the axial collapse mode raises the mean buckling load, while it shows little strain rate dependence once the transition occurs.

Modelling the fire resistance of steel-to-timber dowelled connections loaded perpendicularly to the grain

A framework to model timber connections at normal temperature and in fire, based on combined finite-element (FE) heat-transfer analyses and temperature-dependent Johansen-type load-carrying models, was developed and applied in a parametric study of previously tested beam-to-column steel-to-timber dowelled connections. Comparison with experimental results shows that the FE heat transfer models provide good estimates of measured temperatures and the load-carrying model gives good approximations of the load-carrying capacity at normal temperature (for dowel and embedment failures) and under standard fire exposure. For the degrees of utilisation expected in fire Efi/R20≈0.3, the developed models are able to predict the failure mode of each dowel and the expected load-carrying capacity. Simulation results showed a clear influence of the thickness of the side members on the fire resistance of the analysed connections. The influence of dowel spacing is not so clear, as it also depends on the dowel diameter. A smaller dowel diameter seems to slightly improve the fire resistance, namely for smaller degrees of utilisation or thinner side members, but compromises the load carrying capacity at normal temperature.

Hardness Prediction of Tailor Rolled Blank in Hot Press Forming Using Quench Factor Analysis

This paper aims to predict the hardness of hot formed part for tailor rolled blank (TRB) by the FE-simulation coupled with quenching factor analysis (QFA). Dilatometry test of boron steel is performed at various range of cooling rates from 0.2 to 100°C/s using the dilatometer with forced air cooling system. The dilatometry test provides a hardness data according to cooling curves which are used to determine the material constants (K1~K5) of QFA and the time‒temperature‒property (TTP) diagram of boron steel. Then, FE‒simulation of hot press forming is conducted to predict the cooling curves of hot formed TRB part with a thickness combination of thicker 1.6mm and thinner 1.2mm which is called as rear side member of automotive component. The cooling curves of FE-simulation are applied to predict the hardness of hot formed rear side member using the QFA. Also, experiment of hot press forming is performed to verify the predicted results and to examine the effect of cooling curves on the hardness.

Vehicle energy absorbers consisting of foldable cylinders using response surface methodology

In vehicle head-on collision, the side member cannot be collapsed more than 70% of its length because of its bulk. Moreover, its initial peak load is sometimes too high. So the authors have investigated the foldable origami cylinder structure - reversed spiral cylindrical (RSC) for the existing side member. RSC has solved these two problems mentioned above. In this paper, we treat so called crash box which is shorter than the side member. In the shorter length case, it makes much more difficult to solve the two problems mentioned above simultaneously. With using RSC for the crash box, it is requested to achieve that initial peak load is lower; meanwhile the amount of crash energy absorption is equal or higher than the existing energy absorber. In order to response to the difficulties, the authors try to seek an ideal design specification consisted by RSC and a straight cylinder.

熱可塑性CFRP異形断面ビームのプレス成形と強度評価

As a demonstration of the production process of thermoplastic carbon fiber reinforced plastic (CFRTP) parts by press forming, a varying-cross-section beam has been press formed using thermoplastic carbon fiber composite sheets. The shape of a front side member in an automobile has been applied as the formed shape 800mm long, 170mm wide in front, 270mm wide in the rear and 50mm high. Deformation of the fiber during the press forming has been investigated. Inserting sheets with fiber orientations corresponding to the corner line in the varying width part had an effect on the uniformity of the mechanical strength in the formed beam. Two beams are joined to a closed beam and a drop impact test has been carried out. The results showed that the beam has the favorable characteristic that a constant destruction load is maintained from the front to the distance in which the impact energy is absorbed. The constant destruction load depended on the combined strength of the sheets in the press-forming process.

Simultaneous optimization of blank shape and variable blank holder force of front side member manufacturing by deep drawing

This paper presents a method to determine an optimal blank shape minimizing earing for a front side member. In addition, variable blank holder force, meaning that the blank holder force (BHF) varies through punch stroke, is adopted. Blank shape directly affects the material cost, and it is important to determine an optimal blank shape minimizing earing that is trimmed out. BHF also have an influence on the product quality. Large BHF leads to tearing, whereas small BHF results in wrinkling. Variable BHF (VBHF) approach is recognized as one of the advanced manufacturing technologies, but it is difficult to determine the optimal VBHF for successful sheet metal forming. To determine the optimal blank shape and VBHF simultaneously, design optimization is performed. Numerical simulation in sheet metal forming is so intensive that a response surface approach is valid. In particular, a sequential approximate optimization that the response surface is repeatedly constructed and optimized is used to determine the optimal blank shape and VBHF. Front side member provided from NUMISHEET 2011 (BM3) is used for the numerical simulation. It is found from the numerical result that the proposed approach can drastically reduce the earing. In addition, the maximum thinning is much improved, compared with other results reported in NUMISHEET 2011.

Development of FEA-ANN hybrid model for Equivalent Stress prediction of automobile structural member

Chassis serves as a backbone by supporting the body and diverse parts of the automobile. It ought to be sufficiently rigid to endure the shock, twist, vibration and extra stresses. Then, a vital consideration in chassis design is the strength (Equivalent Stress) for sufficient bending stiffness (Deflection). The primary goal of the research is to build up an Artificial Neural Network (ANN) model for identical stress prediction. Two side members joined to a series of cross members to make the chassis frame. The number of cross members and their locations, cross-section and the sizes of the side and the cross members turn into the design variables. The chassis frame model is created in Creo 3.0 and dissected using Ansys. Since, the number of parameters and levels are more, so the probable models are too much. By changing the Parameters, using the orthogonal array the weight of the sidebar is decreased. Then, FEA is performed on those models. ANN model is prepared by using the results of FEA. For training the ANN model, the standard back-propagation algorithm is observed to be the best. A multi-layer perception network is used for non-linear mapping between the input and the output parameters. FEA-ANN hybrid model can save material used, production cost and time.

Effect of Automotive Side Member Materials on the Head Injury Criteria (HIC) and Chest Severity Index (CSI) of Adult Passenger

This paper presents the results for Head Injury Criteria (HIC) and Chest Severity Index (CSI) of an adult occupant in frontal impact. The component being studied is side member as impact energy absorber. Steel side member is used as the benchmark material, whereas aluminum alloy is used as lightweight material. Crash analyses are conducted using nonlinear finite element analysis software Ls-dyna. The effect of different types of aluminum alloy and component thickness on the HIC, CSI, weight and energy absorbed is assessed and discussed. A cost function is then formulated with the geometrical average method to solve the multi-objective problem. The HIC36 and CSI are set as minimum requirements in the optimization. The materials used was Aluminium alloy of AA 5182 AA5751. It was found that AA5751 with inner and outer thickness of 2.8 mm and 4.9 mm respectively, provides a reduction in mass of 1.03 kg compared with steel and has energy absorbed of 11.9 kJ. The lowest values of HIC36 and CSI obtained are 1146 and 665.4 respectively.

DOUBLE SHEAR TEST BEHAVIOUR OF BALAU SPECIES FOR DIFFERENT END DISTANCE

Timber connection is the most important part in timber structural building. In design, it depends on parameter criteria such as bolt diameter, bolt spacing, edge and end distance. End distance is one of design criteria that will influence mechanical timber joint such in single and double shear. This study focuses for a single fastener joint loaded in double shear with 12mm and 16mm bolt diameters having 30mm and 40mm end distance respectively. Double shear test was conducted on Balau timber species and the finding also focuses on the pattern failure modes with reference to European Yield Model (EYM) theory according to National Design Specification (NDS) 2005. It shows that the joint ability to withstand load decreased when the bolt diameter and end distance smaller and conversely with larger bolt diameter. The failure behavior for 12mm diameter tends to fail into category IIIs which described two plastic hinges formed with crushing of wood fibres in the side members. While, 16mm diameter bolt tends to fail under categories of mode Is which dowel bearing failure or crushing of the side members. Eventually, 12mm bolt diameter produces lower shear strength compared to 16mm bolt diameter.

Effect of Automotive Side Member Materials on the Head Injury Criteria (HIC) and Chest Severity Index (CSI) of Adult Passenger

This paper presents the results for Head Injury Criteria (HIC) and Chest Severity Index (CSI) of an adult occupant in frontal impact. The component being studied is side member as impact energy absorber. Steel side member is used as the benchmark material, whereas aluminum alloy is used as lightweight material. Crash analyses are conducted using nonlinear finite element analysis software Ls-dyna. The effect of different types of aluminum alloy and component thickness on the HIC, CSI, weight and energy absorbed is assessed and discussed. A cost function is then formulated with the geometrical average method to solve the multi-objective problem. The HIC36 and CSI are set as minimum requirements in the optimization. The materials used was Aluminium alloy of AA 5182 AA5751. It was found that AA5751 with inner and outer thickness of 2.8 mm and 4.9 mm respectively, provides a reduction in mass of 1.03 kg compared with steel and has energy absorbed of 11.9 kJ. The lowest values of HIC36 and CSI obtained are 1146 and 665.4 respectively.

Material and shape crash-box influence on the evaluation of the impact energy absorption capacity during a vehicle collision

During a light collision between two vehicles or a vehicle and an obstacle, the internal structure of the car is irrecoverably damaged. In order to limit as much as possible the body in white defacement the new vehicles are equipped with so called crash boxes situated in front and rear of the car. The purpose of our study is to analyze the influence of the crash box material in order to reduce the side member permanent deformations, since once damaged, this component, even repaired, will never assure a good safety in case of major collision. Although the speed necessary for of a car homologation is 16km/h, a second purpose of this paper is to identify the influence of the velocity upon the crash box behaviour. Consequently, a numerical study has been undertaken to investigate axial crushing responses, energy absorption performance of empty & foam filled steel and aluminium concentric tubes with different density of foam.

Experimental and Numerical Analyses of the Lightweight Potential for Hybrid Thin-Walled Members

Within this study, the lightweight potential of thin-walled closed hat members, partially supported by hollow cores, consisting of glass foam granulate and a two component epoxy resin, is investigated. Nonlinear finite element analyses are applied to simulate the behavior under quasi-static three-point bending and to find out the lightweight potential. The simulations are validated by experiments on thin-walled side members of the chassis of a recreational vehicle with and without supporting cores. The results show a significant potential for weight reduction by using supporting cores. Related to the weight (Fmax/Fg), experiments have shown that the collapse load is 38 % larger in comparison to thin-walled members without supporting cores.