Browse Topic: Body-on-frame
In most farm tractors through the middle of the 20th century, a pressed steel frame chassis is used as a supporting part of the tractor on which the engine, wheels, axle assemblies, transmission, steering mechanism, brakes, and suspension members were mounted together. Farm tractors generally used in the agricultural field experiences a variation in the load and vibrations, which leads to failure/fracture in the frame/chassis. In order to reduce the failure/fractures in the chassis/frame, high strength materials are used. Therefore, the main objective of the paper is to identify the best suitable high strength material and most suitable cross section for a mini tractor chassis, so as to make it very strong to bear the heavy loads and shocks received while working in the farms in static conditions. In the present work, ladder chassis is designed and analyzed with three different types of cross sections like C, I and Rectangular box type. Considering the maximum load condition, analysis is done to find the suitable material and cross section for the chassis. Mini tractor chassis designed for SAEISS (SAE India Southern Section) tractor design competition is taken for analysis with three different materials. Finite Element Analysis (FEA) is carried out for getting the chassis with high strength in order to minimize the failures, along with considering the factor of safety. So, a proper finite element model of the chassis is done using Solidworks software, and analysis is done using Ansys. Additionally, wave spring is introduced in between the seat and the tray system of the tractor in order to reduce the vibrations produced in it. From the results, it is observed that the rectangular box type cross-section with A356+B4C Composite is stronger than the other two types of cross-sections for the Ladder Chassis with a least deflection, Von Mises stress and Maximum Shear stress. Also, the wave spring is designed and analyzed with ASTM A401 material and it is found that the total deflection, Von Mises stress and Maximum Shear stress was minimum.
This paper investigates the application of torque weighting to vibration dose value. This is done as a means to enhance correlation of perceived drive comfort directly to driver pedal commands while rejecting uncorrelated inputs. Current industry standards for vehicle comfort are formulated and described by ISO2631, which is a culmination of research with single or multi-axis vibration of narrow or broadband excitation. The standard is capable of estimating passenger comfort to vibrations, however, it only accounts for reaction vibrations to controlled inputs and not perceived vibration request vs. response vibration. Metrics that account for torque inputs and the vibration response create actionable estimates of dosage due to driver torque requests without uncorrelated inputs. This reduces the need for additional accelerometers and special compensating algorithms when road or track testing. The use case for the proposed modified metric is during the powertrain calibration process. Specifically, it can be used to evaluate driver commanded torque transients that cause torque reversal(s) of the drivertrain, e.g., coast to drive or drive to coast, through pedal tip-in or tip-out, respectively. Two body on frame, solid rear axle, full-size trucks featuring a twin turbocharged gasoline direct injected engines each paired with a ten-speed automatic transmission and four-wheel drive selectable transfer case each were utilized in the investigation to collect test data. Road testing was performed on both vehicles instrumented with accelerometers, telemetry torque meters and CAN signal data. Vehicle NVH data in combination with standard and modified dose metrics acquired in various gear states, powertrain calibration configurations and vehicle loading states is presented. The utilization of transient event based torque weighting will be shown to improve correlation of subjective driver related NVH measurements to an objective quantity of dose value for the purposes of adjusting powertrain calibration.
Accurate prediction of in-vehicle powertrain bounce mode is necessary to ensure optimum responses are achieved at driver’s touch points during 4post shake or rough road shake events. But, during the early stages of vehicle development, building a detailed vehicle finite element (FE) model is not possible and often powertrain bounce modes are computed assuming the powertrain to be a stand-alone unit. Studies conducted on FE models of a large SUV with body on frame architecture showed that the stand-alone approach overestimates the powertrain bounce mode. Consequently, there is a need for a simplified version of vehicle model which can be built early on to compute powertrain modes. Previously, representing all the major components as rigid entities, simplified unibody vehicle models have been built to compute powertrain modes. But such an approach would be inaccurate here, for a vehicle with body on frame architecture due to the flexible nature of the frame (even at low frequencies). To address this issue, using theoretical beam formulations, a novel approach was proposed wherein the body on frame vehicle was represented as a two dimensional (2D) continuous beam attached to multiple spring mass systems. Using such a representation of body on frame vehicle to compute powertrain bounce mode was not only unique, but also led to more accurate results compared to the stand-alone unit and hence can be used for predicting powertrain bounce modes during the early stages of vehicle development.
During development of new vehicles, CAE driven optimizations are helpful in achieving the optimal designs. In the early phase of vehicle development there is an opportunity to explore shape changes, gage reduction or alternative materials as enablers to reduce weight. However, in later phases of vehicle development the window of opportunity closes on most of the enablers discussed above. The paper discusses a simplified methodology for reducing the weight in design cycle for truck frames using parametric Design of Experiments (DOE). In body-on-frame vehicles, reducing the weight of the frame in the design cycle without down gaging involves introducing lightening holes or cutouts while still maintaining the fatigue life. It is also known that the lightening holes might cause stress risers and be detrimental to the fatigue life of the component. Thus the ability to identify cutout locations while maintaining the durability performance becomes very critical. This paper describes a method of effectively locating these lightening holes on the truck frame, thereby reducing the weight of the vehicle while preserving the durability performance. The process to incorporate these lightening holes is a multi-step approach beginning with a stress envelope creation. The load paths for each component are identified based on the stress envelops generated in the fatigue code using a complete set of proving ground loading events. A subsequent step includes tuning those lightening holes to meet the durability, strength and stiffness requirements via the automated process of resizing the lightening holes to their optimal sizes. The final verification is carried out with the regular analysis procedure to verify the lightening holes effect on the durability performance of the structure.
Paper withdrawn by author.
Although its best-ever sales year was barely more than 50,000 units and many critics questioned the buying public's desire for a midsize pickup based on a unibody structure instead of the tried-and-true body-on-chassis layout, Honda remained faithful to the concept it introduced with the first-generation Ridgeline pickup, producing it for ten years from 2005-2014. Even through the recession and auto-industry downturn, Honda insisted it was keen to develop a second-generation Ridgeline, to continue to press the idea that if many in pickup-crazed America took an honest look at what they want from a pickup-and equally important, how they actually use a pickup-a unibody-based design would be the most satisfying choice.
Traditional accident reconstruction analysis methodologies include the study of the crush-energy relationship of vehicles. By analyzing the measured crush from a vehicle involved in a real world accident and comparing it to a test vehicle with a known energy, from a crash test, the real world vehicle's damage energy can be evaluated. In addition, the change-in-velocity (Delta-V) can be calculated. The largest source of publicly available crash tests is from the National Highway Traffic Safety Administration (NHTSA). NHTSA conducts numerous Federal Motor Vehicle Safety Standard (FMVSS) compliance and New Car Assessment Program (NCAP) testing for many passenger vehicles for sale in the United States. The NHTSA crash test data is available for analysis, but the data set is limited to production vehicles that are manufactured in significant quantities and it contains virtually no data relating to medium-to-heavy duty vehicles To date, there are no publically available controlled, full-scale, instrumented crash tests of any medium-duty, body-on-frame, delivery vans currently operating on North American roads. Accordingly, this series of full-scale crash tests of two medium-duty, body-on-frame, local vans will provide a basis for the analysis of the crush-energy relationship of these vehicles. This testing will also provide a basis for the study of the occupant kinematics experienced during these tests.
This paper investigates the crashworthiness of structural composite components in frontal and side crash tests. In addition, the safety benefits of composites applications in future lighter vehicles are studied. The methodology of the research includes two steps: (1) developing a light-weight vehicle based on a current finite element (FE) vehicle using advanced plastics and composites, and (2) evaluating the crashworthiness of the light-weighted vehicle by frontal and side New Car Assessment Program (NCAP) test simulations. An FE model of a 2007 Chevrolet Silverado, which is a body-on-frame pickup truck, was selected as the baseline vehicle for light-weighting. By light-weighting components in the Silverado, the vehicle weight was reduced 19%. As a result, the content of plastics and composite in the light-weighted vehicle was 23.6% of the total weight of the light-weight vehicle. Light-weighted composite structural components include bumpers, front-end module, fenders, pillar reinforcements, door beams, and ladder frame. Frontal and side NCAP test simulations of the light-weighted vehicle show that the light-weighted vehicles using advanced plastics and composites provide equivalent structural performance to the baseline vehicle in the full-scale impact condition. Also, this study demonstrates that using plastics and composites can reduce the vehicle weight efficiently.
Filled-rubber is widely used in automotive applications for noise and vibration isolation. The inherent material characteristics of filled-rubber make it suitable for these applications, but its complicated nonlinear behavior under both static and dynamic loading can make material modeling a challenge. This paper presents a two-element overlay technique to capture the nonlinear vibration amplitude dependency of a carbon-filled rubber material commonly referred to as the “Payne Effect.” This overlay technique is practically applied to predict the nonlinear dynamic stiffness and damping loss characteristics of a carbon-filled rubber body cab mount component from a body-on-frame vehicle calculated as a function of large static pre-strain, dynamic excitation frequency, and small dynamic strain amplitude in a single analysis. The first layer of elements is assigned a joint hyperelastic and linear viscoelastic material model that captures the pre-strain and frequency dependent behavior of the rubber material. While the second layer of elements, which is superimposed upon the first layer, is assigned a multi-linear kinematic hardening plasticity material model that captures the hysteresis and amplitude dependency of the material when subjected to dynamic loads. The two-element overlay technique is implemented using commercially available finite element software and is validated using physical test results. The technique accurately predicts the nonlinear dynamic stiffness of the filled-rubber component showing excellent correlation to physical test results while limiting model size and complexity as compared to other approaches.
Among the key parameters that decide the success of a vehicle in today's competitive market are quietness of passenger cabin (in respect of both airborne and structure-borne noise) and low levels of disturbing vibration felt by the occupants. To control these values in body-on-frame construction vehicles, it is necessary to identify major transfer paths and optimize the isolation characteristics of the elastomeric mounts placed at several locations between a frame and the enclosed passenger cabin of the vehicle. These body mounts play a dominant role in controlling the structure-borne noise and vibrations at floor and seat rails resulting from engine and driveline excitations, and they are also a vital element in the vehicle ride comfort tuning across a wide frequency range. In the work described in this paper, transfer path tracking was used to identify root cause for the higher noise and vibration levels of a diesel-powered sports utility vehicle. It was found that the one of the most important paths was the connection at the body mount locations. The mounts exhibited very high dynamic stiffness at frequencies above 50 Hz under installed conditions due to their geometric configuration, resulting in poor isolation of power train-induced vibrations between the frame and the body. New mounts of significantly different geometry were designed and evaluated at various stiffness values to optimize in-cab noise, structure vibration, and secondary ride quality. This resulted in noise-level reductions up to 4 dB(A) at passenger's ear levels through out the engine speed range together with floor vibration reduction in the range of 70 % without adversely affecting the ride qualities of the vehicle.
In this paper, a methodology is discussed to achieve cost-effective solutions for improving vehicle Noise, Vibration and Harshness (NVH) performance of a body-on-frame Multi-Utility Vehicle (MUV). The subject vehicle had objectionable levels of in-cab boom and gear rattle while accelerating in higher gears due to power-train and driveline excitations. Potential transfer paths which might be responsible for amplifying these phenomena were tracked using contemporary noise and vibration measurement techniques. Various modifications were evaluated to improve NVH performance under constraints of vehicle-packaging. An optimized combination of these modifications resulted in improvements in the NVH performance over a wide range of operating speeds with reductions of up to 10 dB achieved in firing frequency excitation, thus eliminating the objectionable boom and gear rattle from the vehicle.
The new 2005 Pathfinder is built on a more rugged body-on-frame platform and features a more powerful V6 and three-row seating. When it was first introduced in 1986, the Pathfinder was the lone SUV in Nissan showrooms in North America. Today the company has SUVs in many shapes and sizes including the full-size truck-based Armada and compact Xterra as well as the car-based Murano. This model variety has allowed the third-generation Pathfinder to return to its body-on-frame truck-based roots from the second-generation's unibody construction. The new model, which went on sale last month, will compete with the likes of middle SUV segment contenders such as the Toyota 4Runner, Ford Explorer, Chevrolet TrailBlazer and GMC Envoy, Dodge Durango, and Jeep Grand Cherokee. Four- and rear-wheel drive will be offered, with Nissan expecting that 70% of customers will opt for the former. The company also projects the take-rate on the four trim levels to be 15% XE (value), 30% SE (value/popularly equipped), 15% SE Off-Road (performance), and 40% LE (fully equipped). The new Pathfinder, along with the new Frontier pickup and smaller Xterra SUV, is the result of the largest investment in a new vehicle platform in the history of Nissan. All told, the program involved a $2.4 billion dollar investment and the participation of all three Nissan technical centers in Japan, the United States, and Europe. Variations on the program's products will be sold in 32 countries.
This paper reports a study of the impact dynamic characteristics of body mounts in a body-on-frame vehicle. Two methods of dynamic analyses are utilized. One method is direct impact; and the other excitation on the body mount. Using a series of component test data, the direct impact method yields the natural frequency, f, and damping factor, ζ, for a spring-mass-damper model of a body mount. The functional relationship between the g-force versus deflection curve and f, ζ, and v (impact speed) is examined. Given a frame impulse, the excitation method predicts the body response by the convolution integral. The transient transmissibility (TT), the ability of a body mount to transmit shock impulse from the frame to the body in the early part of crash duration, is investigated. The degree of front-loadedness on the body pulse is determined by TT and thus it affects the occupant/vehicle crash response.
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