Browse Topic: Underbodies
ABSTRACT Over the course of typical survivability analyses for underbody blast events, a multitude of individual cases are examined where charge size, charge location relative to the vehicle, and vehicle clearance from the ground are varied, so as to arrive at a comprehensive assessment. While multi-physics computational tools have reduced the expense and difficulty of testing each loading case experimentally, these tools still often require significant execution and wall-clock times to perform the simulations. In efforts to greatly reduce the time required to conduct a holistic survivability analysis, Fast Running Models (FRMs) have been implemented and validated to act as a surrogate for the computationally expensive finite element tools in use today. Built using a small set of simulations, FRMs generate loading data in a matter of seconds, representing a significant improvement in survivability analysis turnaround time
ABSTRACT This paper reviews the Army Generic Hull [1-5] as a vital developmental tool for underbody blast modeling and simulation applications. Since 2010, it has been used extensively to help calibrate and validate various numerical software codes and methodologies. These are being used extensively today in the development of underbody armor, as well as mine blast subsystems such as seats, to protect both military vehicles and their occupants. In the absence of easily shareable information in this domain due to data classification, this specially formulated product is a valuable part of any toolset for underbody blast development and product design. Citation: K. Kulkarni, S. Kankanalapalli, V. Babu, J. Ramalingam, R. Thyagarajan, “The Army Generic Hull As A Vital Developmental Tool For Underbody Blast Applications,” In Proceedings of the Ground Vehicle Systems Engineering and Technology Symposium (GVSETS), NDIA, Novi, MI, Aug. 16-18, 2022
ABSTRACT For this particular effort, TARDEC Center for Systems Integration (CSI) was tasked to lead an effort to develop an underbody kit that would serve multiple functions. The underbody kit would provide an additional 1,200 lbs of net buoyancy to enhance water mobility per the LAV. This program is in the development and testing phase with a prototype expected to be produced June of 2015. This program is one of multiple efforts to ensure the FOLAV meet all system requirements to keep the vehicle viable to 2035. In addition, the TARDEC concept/prototype must meet the same mine blast protection provided by the underbody D-Kit that was produced for the fleet of vehicles in 2010. This is a unique challenge as a combination of buoyancy, mine blast, and structural requirement on a ground military vehicle is novel idea. Vehicle weight and survivability requirements are difficult challenges on combat vehicles, to include the LAV, so the TARDEC solution would have to reduce the weight of the
ABSTRACT Presented are two designs for compact, low-profile UGVs with high cross-country mobility, intended for underbody operations with heavy manned vehicles. These UGVs are designed to remotely detect and assess combat damage incurred during combat operations, and analyze wear, leaks, and cracks, without the need for a human technician to be exposed to enemy fire, allowing crews to rapidly assess the conditions of their vehicles. Since robots required for underbody inspection would necessarily maintain a low, compact profile, they could also perform effective last-mile resupply in a contested environment, their small size allowing them to hide behind terrain and battlefield debris much more effectively than a heavy logistics robot. Naturally, a robotic vehicle that is capable of rapid underbody inspection of friendly vehicles or last-mile resupply could also be easily adapted as a combat platform to be used against enemy vehicles. Citation: A. Washington, et al., “Expendable Low
ABSTRACT In this paper a new bolt attachment method was explored, where the attaching bolts were divided into two sets. The first set of bolts was tightened and was used to connect the underbody plate to the hull under ordinary operations. The second set of bolts connecting the plate and the hull were not tightened and had some extra axial freedom. Under blast loading, the first set of bolts would break due to high tensile and shear loads, but the second set of bolts would survive due to extra axial freedom which allows the plate and the hull vibrate and separate from each other to a certain extent. A simulation model was developed to verify this concept. Three underbody plate-hull connection approaches were simulated and analyzed: 1) all tightened bolts, 2) some bolts not fully seated, 3) all bolts not fully seated. The simulation results show that with option 1), 100% of the bolts broke under the blast loading. With option 2) the not fully seated bolts survived and continued to
ABSTRACT In order to defeat under body blast events and improve crew survivability, a monocoque aluminum cab structure has been designed as a drop on solution based on the current M1151A1 (HMMWV) chassis. The structure is comprised of all 5083-H131 Aluminum alloy armor plates with various thicknesses. The structure design consists of the following new features: (1) Robust joining design utilizing interlocking ballistic joints and mechanical interlocking features, (2) unique B-pillar gusset design connects roof & floor with B-pillar & tunnel, and (3) “Double V” underbody shaping design. The TARDEC designed, integrated & built vehicle achieved no crew core body injuries for a vehicle of this weight class and demonstrated meeting the crew survivability objective when subjected to a 2X blast during the live fire underbody blast tests. These efforts help to not only baseline light tactical vehicle capabilities, but also validate the possibility of meeting aggressive blast objectives for
The automotive sector’s growing focus on sustainability has been spurred to investigate the creation of sustainable resources for different parts, emphasizing enhancing efficiency and minimizing environmental harm. For use in automobile flooring trays and underbody shields, this study examines the impact of injection molding on composite materials made of polyvinyl chloride (PVC) and Linum usitatissimum (flax) fibers. As processed organic fiber content was increased, the bending and tensile rigidity initially witnessed an upsurge, peaking at a specific fiber loading. At this optimal loading, the composite exhibited tensile strength, flexural strength, and elastic modulus values of 41.26 MPa, 52.32 MPa, and 2.65 GPa, respectively. Given their deformation resistance and impact absorption attributes, the mechanical properties recorded suggest that such composites can be efficiently utilized for automotive underbody shields and floor trays. The inherent structure of the flax fiber within
In electrified automobiles, wind noise significantly contributes to the overall noise inside the cabin. In particular, underbody airflow is a dominant noise source at low frequencies (less than 500 Hz). However, the wind noise transmission mechanism through a battery electric vehicle (BEV) underbody is complex because the BEV has a battery under the floor panel. Although various types of underbody structures exist for BEVs, in this study, the focus was on an underbody structure with two surfaces as inputs of wind noise sources: the outer surface exposed to the external underbody flow, such as undercover and suspension, and the floor panel, located above the undercover and battery. In this study, aero-vibro-acoustic simulations were performed to clarify the transmission mechanism of the BEV underbody wind noise. The external flow and acoustic fields were simulated using computational fluid dynamics. The vehicle structural vibration and sound fields of the interior and exterior cabin
This study numerically investigates the vortex flow that is generated within the underbody diffuser of a bluff body. Previous experimental studies have identified the existence of three main types of trailing vortex structures that correlate with the aerodynamic behavior of an underbody diffuser in ground-effect. The “force enhancement” behavior of the underbody diffuser results in a pair of longitudinal counter-rotating vortices that are generated off of the sidewalls within the upswept section of the underbody diffuser. By comparing the aerodynamic forces with the resulting flow field induced by the trailing vortex pair, this investigation aims to identify a relationship between the circulation of the vortices and the resulting downforce. It is hypothesized that the circulation generation of the vortex pair is directly linked to the generation of the downforce, just as with a wing. The bluff body features an elliptical nose, a straight midsection, and a thin-walled underbody diffuser
A multi-year, multi-vehicle study was conducted to quantify the aerodynamic drag changes associated with drag reduction technologies for light-duty vehicles. Various technologies were evaluated through full-scale testing in a large low-blockage closed-circuit wind tunnel equipped with a rolling road, wheel rollers, boundary-layer suction and a system to generate road-representative turbulent winds. The technologies investigated include active grille shutters, production and custom underbody treatments, air dams, wheel curtains, ride height control, side mirror removal and combinations of these. This paper focuses on mean surface-, wake-, and underbody-pressure measurements and their relation to aerodynamic drag. Surface pressures were measured at strategic locations on four sedans and two crossover SUVs. Wake total pressures were mapped using a rake of Pitot probes in two cross-flow planes at up to 0.4 vehicle lengths downstream of the same six vehicles in addition to a minivan and a
During Operation Iraqi Freedom and Operation Enduring Freedom, improvised explosive devices were used strategically and with increasing frequency. To effectively design countermeasures for this environment, the Department of Defense identified the need for an under-body blast-specific Warrior Injury Assessment Manikin (WIAMan). To help with this design, information on Warfighter injuries in mounted under-body blast attacks was obtained from the Joint Trauma Analysis and Prevention of Injury in Combat program through their Request for Information interface. The events selected were evaluated by Department of the Army personnel to confirm they were representative of the loading environment expected for the WIAMan. A military case review was conducted for all AIS 2+ fractures with supporting radiology. In Warfighters whose injuries were reviewed, 79% had a foot, ankle or leg AIS 2+ fracture. Distal tibia, distal fibula, and calcaneus fractures were the most prevalent. The most common
In the last decades it has been constantly debated about the behaviour of the human being towards a better usage of the natural resources through a restructuring of unsustainable processes. Considering the case for road vehicles, it was noticed a potential for improvement by assigning a more “harmonious” configuration to the underbody of the vehicles, in order to contribute to the reduction of aerodynamic drag. This region of the vehicles is often overlooked by the automakers because it is not easily accessible to the eyes of the consumer. The objective of this paper is, therefore, to improve the aerodynamic performance of the underbody region of a compact hatchback car available in the Brazilian market. This project proposes a new underbody configuration that promotes a more harmonious flow under the vehicle, reducing this way the drag coefficient (Cd) hence improving the fuel consumption. A comparative analysis, therefore, was performed between the standard condition of the underbody
A full-system, end-to-end blast modeling and simulation of vehicle underbody buried blast events typically includes detailed modeling of soil, high explosive (HE) charge and air. The complex computations involved in these simulations take days to just capture the initial 50-millisecond blast-off phase, and in some cases, even weeks. The single most intricate step in the buried blast event simulation is in the modeling of the explosive loading on the underbody structure from the blast products; it is also one of the most computationally expensive steps of the simulation. Therefore, there is significant interest in the modeling and simulation community to develop various methodologies for fast running tools to run full simulation events in quicker turnarounds of time. This paper discusses investigation of a fast running blast loading methodology wherein the effects of the soil can be adequately captured without having to employ a highly detailed and computationally intensive soil
It is well known that the underbody region of a tractor-trailer is responsible for up to 30% of the aerodynamic drag. This is the highest drag created by any region of a tractor-trailer. There are a number of underbody drag-reduction devices available on the market but they create a few operational issues, such as low ground clearance and ice collection, which inhibit their mass market appeal. In this paper, a novel concept of an underbody aerodynamic device is developed and investigated. The underbody device is a combination of a ramp and a side skirt; which are optimized simultaneously. In addition, the device is made collapsible to facilitate easy storage when not in use (i.e., city driving). NASA’s Generic Conventional Model (GCM); a 1/8th scale model of a generic class-8 tractor-trailer is used to evaluate and optimize the concept. The GCM allows the concept to be applicable to a wider range of tractor-trailers. The studies were conducted using the RANS based turbulence model, k-ω
Anthropomorphic test devices (ATDs) have been used in automotive safety research since the 1970s to predict injuries. ATDs must repeatedly perform under a dynamic range of loading rates and reliably distinguish between injuries ranging from minor to severe
The automotive underbody diffuser is an expansion device which works by speeding up the air flowing underneath a vehicle. This reduces the pressure below the vehicle thereby increasing downforce. When designed properly, it can lead to a massive gain in downforce and even a reduction in drag. However, a majority of the research and development is restricted to motorsport teams and supercar manufacturers and is highly secretive. Most of the publicly available research has been done for very simple shapes (bluff bodies) to study the effects of ground clearance and rake angle. Very little research has been done for complex geometries with vanes, flaps and vortex generators. This paper aims to investigate the effects of the addition of vanes/strakes and flaps, their location as well as angle, on diffuser performance. Computational Fluid Dynamics simulations have been carried out using three dimensional, steady state RANS equations with the k-ε turbulence model on STAR CCM+ V9.06. The
Three laboratory simulated sub-injurious under-body blast (UBB) test conditions were conducted with whole-body Post Mortem Human Surrogates (PMHS) and the Warrior Assessment Injury Manikin (WIAMan) Technology Demonstrator (TD) to establish and assess UBB biofidelity of the WIAMan TD. Test conditions included a rigid floor and rigid seat with independently varied pulses. On the floor, peak velocities of 4 m/s and 6 m/s were applied with a 5 ms time to peak (TTP). The seat peak velocity was 4 m/s with varied TTP of 5 and 10 ms. Tests were conducted with and without personal protective equipment (PPE). PMHS response data was compiled into preliminary biofidelity response corridors (BRCs), which served as evaluation metrics for the WIAMan TD. Each WIAMan TD response was evaluated against the PMHS preliminary BRC for the loading and unloading phase of the signal time history using Correlation Analysis (CORA) software to assign a numerical score between 0 and 1. A weighted average of all
The present work deals with a computational study of a ‘DrivAer’ car model, the rear-end shape of which corresponds to the Notchback configuration (Heft et al. [1] and Heft [2]). The study investigates the effects of the underbody geometry and wheel rotation on the aerodynamic performance. The configurations with detailed and smooth underbody as well as with stationary and rotating wheels are considered. The computational model applied relies on a VLES (Very Large Eddy Simulation) formulation, Chang et al. [3]. The residual turbulence related to the VLES framework is presently modelled by a RANS-based (Reynolds-Averaged Navier-Stokes), four-equation (D(k,ɛ,ζ, f)/Dt) near-wall eddy-viscosity model, Hanjalic et al. [4]. In addition to the equations governing the kinetic energy of turbulence (kus) and its dissipation rate (ɛus), it solves a transport equation for the quantity , representing a key parameter, as it models the velocity scale in the expression for the corresponding turbulence
This specification covers underbody corrosion preventive compounds for application to vehicle underbodies
Recently, modeling and simulation (M&S) engineers have made impressive strides in improving ground vehicle reliability and soldier safety. This work involved live-fire testing and evaluation (LFT&E) of the effects of underbody improvised explosive device (IED) blasts on moving ground vehicles. A multi-fidelity, multi-temporal M&S methodology was developed and successfully applied towards reconstruction of theater IED events
A blast buck (Accelerative Loading Fixture, or ALF) was developed for studying underbody blast events in a laboratory-like setting. It was designed to provide a high-magnitude, high-rate, vertical loading environment for cadaver and dummy testing. It consists of a platform with a reinforcing cage that supports adjustable-height rigid seats for two crew positions. The platform has a heavy frame with a deformable floor insert. Fourteen tests were conducted using fourteen PMHS (post mortem human surrogates) and the Hybrid III ATD (Anthropomorphic Test Device). Tests were conducted at two charge levels: enhanced and mild. The surrogates were tested with and without PPE (Personal Protective Equipment), and in two different postures: nominal (knee angle of 90°) and obtuse (knee angle of 120°). The ALF reproduces damage in the PMHS commensurate with injuries experienced in theater, with the most common damage being to the pelvis and ankle. Load is transmitted through the surrogates in a
Electric cars are the future of urban mobility which have very less carbon foot print. Unlike the conventional cars which uses BIW (Body in White), some of the electric cars are made with a space frame architecture, which is light weight and suitable for low volume production. In this architecture, underbody consists of frames, battery pack, electronics housing and electric motor. Underbody drag increases due to air entrapment around these components. Aerodynamic study for baseline model using CFD simulations showed that there was a considerable air resistance due to underbody components. To reduce the underbody drag, different add-ons are used and their effect on drag is studied. A front spoiler (air dam) is used to deflect the incoming air towards sides of the car. A under hood cover for front components, trailing arm cover for trailing arm and rear bumper cover for rear components were used to reduce underbody drag. Finally it is observed that aerodynamic behavior of the car
Vehicle water wading capability refers to vehicle functional part integrity (e.g. engine under-tray, bumper cover, plastic sill cover etc.) when travelling through water. Wade testing involves vehicles being driven through different depths of water at various speeds. The test is repeated and under-body functional parts are inspected afterwards for damage. Lack of CAE capability for wading equates to late detection of failure modes which inevitably leads to expensive design change, and potentially affects program timing. It is thus of paramount importance to have a CAE capability in this area to give design loads to start with. Computational fluid dynamics (CFD) software is used to model a vehicle travelling through water at various speeds. A non-classical CFD approach was deemed necessary to model this. To validate the method, experimental testing with a simplified block was done and then verified with CFD modeling. The simple rectangular block at two different speeds and three
The materials classified under this specification are: a Mastic vibration damping materials used to reduce the sound emanating from metal panels. b Mastic underbody coatings used to give protection and some vibration damping to motor vehicle underbodies, fenders, and other parts
This work is based on a current project funded by the United States Army Small Business Innovation Research (SBIR) Program and is being conducted with the Tank Automotive Research, Development and Engineering Center (TARDEC) Ground Systems Survivability (GSS) Team and Paradigm Research and Engineering. The focus of this project is to develop an advanced and novel sensing and activation strategy for Pyrotechnic Restraint Systems, Air Bags and other systems that may require activation. The overriding technical challenge is to activate these systems to effectively protect the Soldier during blast events in addition to Crash, Rollover and Other Injury Causing events. These activations of Pyrotechnic systems must occur in fractions of milliseconds as compared to typical automotive crashes. By investigating systems outside of typical accelerometer based applications and activations, the potential exists to exploit systems that require little power, are self-contained and provide the required
In today's vehicles underbody parts are absolutely necessary to reach a certain performance level regarding fuel saving, corrosion protection, driving performance and exterior as well as interior noise. With the constant demand for additional parts, which means additional weight on the car, lightweight materials have come more and more into the focus of development work. LWRT (low weight reinforced thermoplastic) is the acronym for this material group. The ongoing success of such materials in underbody applications that compared to compact materials such as GMT (glass mat reinforced thermoplastic) is the weight saving of up to 50 %, or in other words, with LWRT you can cover twice as much surface then with GMT. The production process is compression molding, but with low pressure because LWRT-material needs only partial compact areas, most regions of these parts can have a density even below 0.5 g/cm3. Another advantage coming with the process is the possibility to use multi-cavity
The Wuling Rongguang is a small van which uses a mid-engine layout where the engine is located underneath the floor panel in-between front and rear wheels. A particular challenge for this kind of layout is the protection of the engine against soiling. Typical protective measures consist of large mudguards in combination with an engine cover. While needed for soiling protection, these parts can have a strongly adverse effect on aerodynamic drag. This paper describes process and the results of the aerodynamic optimization of the underbody of the Wuling Rongguang. Because design changes had to be evaluated for aerodynamics performance as well as for their effect on the soiling, a digital approach was used which allowed to do the soiling analysis as a post processing to the flow simulation. As a first step, a baseline model was built and analyzed. This included the development of a soiling model taking into account wheel spray and splashing effects. The soiling model used available best
In this paper the effects of a rough underbody on the rear wake structure of a simplified squareback model (the Windsor model) is investigated using balance measurements, base pressure measurements and two and three component planar PIV. The work forms part of a larger study to develop understanding of the mechanisms that influence overall base pressure and hence the resulting aerodynamic drag. In the work reported in this paper the impact of a rough underbody on the base pressure and wake flow structures is quantified at three different ground clearances. The underbody roughness has been created through the addition of five roughness strips to the underbody of the model and the effects on the wake at ground clearances of 10.3%, 17.3% and 24.2% of the model height are assessed. All work has been carried out in the Loughborough University Large Wind Tunnel with a ¼ scale model giving a blockage ratio of 4.4% for a smooth under-body or 4.5% with the maximum thickness roughness strips
The Selective Catalytic Reduction (SCR) is the main after-treatment solution for high efficient diesel engines under development to cope with future lower fuel consumption and NOx emissions requirements (EU6+ legislation). Exhaust gas temperatures are decreasing too, leading to new after-treatment system developments in a close coupled position. Nevertheless before all vehicle architectures allow it, SCR systems are and will still be installed in underbody position. The current paper deals with an underbody metal SCR after-treatment systems, which is capable of active thermal management, and an ultra-compact SCR dosing system. These technologies are described and emission results obtained on several application examples (from passenger cars to light duty commercial vehicles) are presented and discussed in conjunction with an effective active thermal management of the SCR function. It is shown that the NO2/ NOx ratio as well as the temperature level at SCR system inlet, among all the
Wind noise has become an important indicator for passenger automobile quality. Several transmission paths can be related to different parts of the vehicle exterior. While the greenhouse (side glasses, windshield, seals & others) often dominates the interior noise level above 500 Hz, the contribution coming from the underbody area usually dominates the interior noise spectrum at lower frequencies. This paper describes a framework of numerical tools which is capable of determining realistic underbody turbulent and acoustic loads being generated for typical driving conditions, as well as performing the noise transmission through underbody panels and the propagation of sound to the drivers ear location. Different numerical tests are performed to demonstrate the ability of a Statistical Energy Analysis model updated with Finite Element Method properties to predict accurately the noise transmission through the underbody of simplified car vehicle in the mid frequency range under aero acoustic
In this paper, using the facilities offered by the ANSYS CFX, CFD code, the authors investigate numerically the flow around the Ahmed body for the rear slanted upper surface of 35°, fitted with a simple underbody diffuser, without endplates, in order to find the influence of the later one on the main aerodynamic characteristics, drag and lift. Relative motion between body and ground is simulated. The study is performed for different geometrical configurations, length and the angle of the diffuser being the parameters which are varied in ranges which are relevant for hatchback passenger cars. Later, based on a theoretical approach, a coefficient of the equivalent hydraulic resistance of the diffuser is computed, which helps to evaluate the drag due to underbody diffuser
During the life of a vehicle its tyres project a considerable amount of particles against the car underbody as well as to car body visible parts: the “stone chipping” effect is a significant source of corrosion of an automotive underbody along with undesired unaesthetic effects. Deposition of protective films counteracts the effects of the particles but protective coating extension and layout is somewhat driven by the experience. An actual simulation of the stone impact is then useful in order to design both coating thickness and layout. Nevertheless, even if the simulation of a single particle is, with reasonable simplifications, a quite straightforward task, the simulation of an actual impact of a real set of particles is almost impossible to attack due to the very large number of particles involved in the process and their mutual interactions. A more feasible approach relies on defining a “random particle” as a set of random variables with suitable distributions of mass, velocity
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