Front Subframe Research Articles

Research on optimization of the vehicle handling stability considering flexibility of the front subframe

The elastic deformation of the front subframe during vehicle traveling affects the vehicle handling stability. The static equilibrium equations of the suspension and subframe system and the kinematics equations of the three-degree-of-freedom vehicle are established to illustrate the principle of the influence of the flexible front subframe on the handling stability. The front subframe is flexibly processed to establish a rigid-flexible coupled vehicle model. Simulations of the suspension kinematic and compliance alongside sine swept steering simulation of the vehicle are performed. The front subframe bushing stiffness, which has a greater impact on the handling stability, is selected as a design variable through parametric test design, and the NSGA-II algorithm is used for multi-objective optimization with the vehicle handling stability evaluation index as the optimization target. The simulation results show that the flexible front subframe will make the bushing force change to affect the suspension kinematic and compliance characteristics and then affect the vehicle handling stability, the gain of vehicle yaw rate and the delay time of lateral acceleration decrease, while the gain of roll angle increases. The optimization results show that the optimized vehicle exhibits improvements in the yaw rate gain, delay time of lateral acceleration, and roll angle gain.

Multi-Objective Lightweight Optimization Design of the Aluminium Alloy Front Subframe of a Vehicle

The aluminium alloy front subframe of an automobile was developed through multi-operating condition topology optimization and multi-objective optimization methods. By considering the influences of loads on the strength, static stiffness, and modal of the aluminium alloy front subframe under typical operating conditions, the performance parameters of the aluminium alloy front subframe after topology optimization were obtained. After topology optimization was performed, the parametric model of the aluminium alloy front subframe was established. Based on the Isight optimization platform, sample points were generated with the optimal Latin hypercube test method, and the response surface approximate model was constructed. The minimum mass and maximum first-order frequency were taken as the objectives, the stress under typical working conditions did not exceed the set target value, and the maximum displacement of the installation point was taken as the constraint condition. The multi-objective particle swarm optimization algorithm was used to optimize the aluminium alloy front subframe. The error of the free modal and finite element free modal analysis of the aluminium alloy front subframe samples was less than 15%. The optimized aluminium alloy front subframe was 2.4 kg lighter than the original subframe under the premise of satisfying various performance indices, and the lightweight rate was up to 12%.

Life cycle energy and greenhouse gas emissions implications of using carbon fiber reinforced polymers in automotive components: Front subframe case study

Vehicle lightweighting benefits consumers through fuel savings, manufacturers through a more fuel-efficient vehicle portfolio, and the environment through reduced fossil fuel use and lower emissions. Vehicle components can be lightweighted by replacing conventional materials with alternatives such as aluminum or composites. However, lightweight materials come with their own set of environmental and economic challenges. Often, manufacturing of lightweight materials requires more energy than for conventional materials such as steel. Understanding the net energy and environmental benefits of lightweighting requires life cycle assessment with a large enough system boundary to prevent shifting of impacts and to ensure a fair comparison between different material options. Life cycle assessments of carbon fiber composite parts are hampered by substantial uncertainties in the energy needed for their production and recycling and the vehicle fuel consumption benefits. The present study addresses these deficiencies using a detailed vehicle fuel consumption model and industrially relevant carbon fiber production data and component design. The front subframe case study considered illustrates the challenges associated with achieving life cycle energy and greenhouse gas savings using carbon fiber. The base case with no powertrain resizing, secondary weight savings, or recycled carbon fiber and with 160,000 miles vehicle lifetime has no energy or emission benefits. When powertrain resizing, secondary weight savings, carbon fiber recycling, and increased vehicle lifetime travel were considered, energy and greenhouse gas benefits were found.

Center Floor Undercover Air Guide Development to Improve Aerodynamic Drag for a Passenger Car

Cooling airflow is essential to the vehicle air conditioning system and engine cooling module. The cooling airflow in the engine room flows out through the front subframe, front wheelhouse, roll-rod, etc. and mixes with the upstream external flow in the underbody of the vehicle so that it affects the aerodynamic drag on the rear part of the vehicle. An air guide is developed to reduce the aerodynamic drag. It is attached on the center floor undercover and induces cooling airflow exited from the engine room to flow to the rear section of the underbody of a vehicle. It can reduce up to 2.3 % of the aerodynamic drag of baseline vehicle. Numerical flow simulations are performed at the velocity of 140 km/h vehicle driving condition.

Template Matching of Round Features of Aluminum Alloy Castings Based on Hu Constant Moment

Automobile structural parts, that is automobile frame, are used as load-bearing equipment with advanced mechanical properties so that it need to be strictly inspected. There are geometric characteristics, uneven distribution of positions, and large volume for automobile structural castings of aluminum alloy. Thus, it is necessary that the feature matching deals with the automobile structural casting by detection of visual image. However, the traditional visual image has exposed many essential problems, such as lower degree and lower field-of-view stitching accuracy. According to the above phenomenon, a template detection method is proposed based on Hu moment, combined with the target of round feature under the front sub-frame of a certain model of Zotye Automobile. The picture is converted into a binary image with the connected domain label. The feature values are obtained by the template image and the regional features is calculated. Secondly, the Euclidean distance is applied to judge the similarity before finishing the template matching. Finally, the matching accuracy can reach 100%, but also running time of the algorithm is less than 0.08s for the round holes of the front sub-frame under experimental data.

Identification of vehicle interior noise sources based on wavelet transform and partial coherence analysis

Abstract Vehicle interior noise has an important influence on the physical and psychological perceptions of passengers and their perception of vehicle quality. The identification of potential noise sources is necessary to effectively reduce vehicle interior noise and/or improve perceived vehicle quality. In this paper, a subjective evaluation of interior noise and vibration measurements was conducted. The contributions of different noise sources, such as the engine, transmission, and structure-borne noises that radiate from the vibrations of the car body panels, were investigated using continuous wavelet transform and partial coherence analysis methods to identify major sources of vehicle interior noise. The continuous wavelet transform results indicated that most interior noise was low and middle-frequency noise. The partial coherence analysis of the vibro-acoustical signals showed that the structural vibrations responsible for structure-borne noise contribute more to interior noise than airborne noise. This case study shows that one of the main sources of interior noise in the sample vehicle is the structure-borne noise that radiates from the car body panels connected to the front sub-frame. This structure-borne noise resulted from the low vibrational isolation ratio of the rear engine mount. In addition, to validate the effectiveness of the proposed method, another vehicle was tested to identify interior noise sources. For this vehicle, the structure-borne noise clearly radiated from the panel suspension. These findings can be further applied to facilitate the reduction of vehicle interior noise.

A study on localized expansion defects in tube hydroforming

This study investigated localized expansion in the tube hydroforming process, which may induce cracks in the tube material. First, a model of a trailing arm in the front subframe was built using the finite-element method; it was compared with the actual component to verify the accuracy of the model. Subsequently, a localized expansion model was constructed to analyze the effects of the tube geometry parameters and material-hardening parameters on localized expansion and the fracture location. The simulation results indicated that localized expansion can be ameliorated by changing the material distribution of the tube using a preform or an inner die; these methods substantially reduced the maximum material thinning. However, these methods can only be applied to the local bulging area that occurs when both sides of the tube are constrained. When both sides are not constrained, the material bulges back to the original state, and localized expansion occurs. In this study, both sides of the localized expansion area of the trailing arm in the front subframe were constrained, and the material distribution of the fracture zone could be changed by moving the mandrel to improve the localized expansion-induced fracture characteristics. Experimental results successfully validated the proposed method and analysis.

Reduction in strength requirements of material of the subframe of truck with independent suspension by topological optimization of the design and power scheme

The paper describes application of the method of topology optimization on the basis of finite element modeling when design highly loaded parts of the chassis of the vehicle. The brief theoretical information on method of optimization based on the application of the concept of body with variable density is given and two popular formulations of the problem were considered: with objective function in type of minimum strain energy of deformation and with objective function in type of minimum mass. In first case, constraints on objective function are set in the form of a maximum usage percentage of the original volume of space design, and in the second case, restrictions on objective function are set in form of maximum allowable displacements and stresses in the elements of space design. An example of the synthesis of the power scheme of the front sub-frame independent suspension of the truck with a description of the estimated model is given. For the solution of optimization problems were selected five the most heavy-load modes of the frame. The figure is shown of the available layout space design for subframe. The result of solving the problem of topological optimization is subject to a geometrical interpretation in the form of separate parts and combining them into assembly units. The result is the design of the subframe, close to the truss type (without the elements, working in bending and shear). For the design was carried out verifying calculation of strength at the same five load modes. The analysis results show the strength of low operating voltage in parts of the subframe, due to the lack of significant stress concentrators and compliance of space topology of the sub-frame structure to solution of the problem of topological optimization. Low operating voltage allows to use as construction material of sub-frame the cheap steel with low strength properties. Thus, the use of topology optimization to create an optimal constructive-power circuits of highly loaded structures allows to reduce the demands on the material properties while improving the performance characteristics of the products - durability, stiffness and reduced mass.

A hybrid method of modified NSGA-II and TOPSIS for lightweight design of parameterized passenger car sub-frame

This paper presents a hybrid method integrating modified NSGA-II and TOPSIS, used for lightweight design of the front sub-frame of a passenger car. Firstly, the FE model of the sub-frame is constructed and is validated by modal test. Then, the strength performance of the sub-frame is analyzed under four typical load conditions consisting of braking, acceleration, steady state cornering and vertical bump. After that, a parameterized model of the sub-frame, in which 12 geometric parameters are defined as design variables, is developed based on the mesh morphing technology. Subsequently, modified NSGA-II is employed for multi-objective optimization of the sub-frame considering weight, maximum von-Mises stress and first order natural frequency as three conflicting objective functions. Accordingly, a set of Pareto-optimal solutions are obtained from the optimization process. Finally, the entropy weight theory and TOPSIS method are adopted to rank all these solutions from the best to the worst for determining the best compromise solution. In addition, the effectiveness of the proposed hybrid lightweight design method is demonstrated by the comparisons among baseline design and optimum solutions.

Research on Accelerated Testing Method for the Service-simulation Fatigue Test of Automotive Front Sub-frame

Research on Accelerated Testing Method for the Service-simulation Fatigue Test of Automotive Front Sub-frame

Durability prediction for automobile aluminum front subframe using nonlinear models in virtual test simulations

This research work presents fatigue life evaluation techniques for an automotive vehicle aluminum front subframe using virtual test simulation technology with nonlinear suspension components model. The technology was used for improving the accuracy of the polynomial model used in conventional analysis. The proposed nonlinear suspension components models were developed using direct approach. The effects of the nonlinear elements on the prediction of the fatigue life were also analyzed. Actual aluminum front subframe was tested using half-car road test simulator to verify the accuracy of the models. It was found that the proposed nonlinear models yield more accurate results than conventional polynomial models. The proposed virtual test simulation technology with nonlinear suspension components model can be used to predict fatigue life for vehicle chassis structures more accurately.

Strength and Formability Designs of Tube-hydroformed Automotive front Sub-frame

To call for carbon cut, the automobile industry has been widely used tube-hydroforming technology instead of traditional stamping technology to achieve the reduction of structural weight, the enhancement of vehicle structural strength and low fuel consumption. This study targets on automobile front suspension system in modifying the front sub-frame design from stamping-welding parts to a one-piece tube-hydroformed part. First of all, this study refers to the result of cross-section analysis to put up with the modification directions to meet the part strength and manufacturability requirements. According to the modified finished surface, the part strength was evaluated by the comparing the stress and strain distributions of the tube-hydroformed part with those of stamping-welding parts. The impact properties of the tube-hydroformed part was also examined and the results indicated that the tube-hydroformed part exhibits a satisfactory impact mechanism and better capability in energy absorption compared to the stamping-welding parts. The die design for tube-hydroforming the front sub-frame was then investigated in the present study. Both the bending process and the perform design were optimized to avoid the presence of fracture. The proposed tube-hydroformed part design and the manufacturability of this part were validated by the production part. The consistency between the finite element simulation results and the production part in dimension accuracy confirms the effectiveness of the tube-hydroformed part design established in the present study.

Adaptive structure concept for reduced crash pulse severity in frontal collisions

From accident statistics in real-world frontal collisions, it has been shown that a considerable portion of injuries occur in situations without major passenger compartment intrusions and that these injuries can be attributed to the occupant interaction with the restraint systems. To address these types of injuries, a novel front structure concept is proposed. This structure includes a partly detachable front subframe that can actively be released from the passenger compartment and thereby reduce the crash forces and related decelerations. The aim of this study was to quantify the effect of an adaptive front structure on occupant loading in a modern passenger car in frontal crash situations. A simplified finite element model was derived from a full vehicle model in order to run a large simulation matrix spanning from full overlap to small overlap situations. Occupant loading was estimated by using two simplified occupant chest deceleration models, the Volvo Pulse Index and the Occupant Load Criterion. Results suggest that modifying the crash pulse shape can be equivalent to reducing the velocity change in a crash by up to 44%. In relation to scenarios without subframe release, this indicates a considerably lower force required to be applied to the occupant from the restraint system.

Two Welding Models Application on Fatigue Analysis for Front Sub-Frame

This article firstly established two finite element models of seam weld and spot-weld for the front sub-frame, then used the two models for seam weld and spot weld fatigue simulation analysis, next cooperated with bench test results for verification. After the above steps, we not only found the weak portion of the front sub-frame, but also provide reference for both optimum design and improving the bench test design.

Analysis of Life-Cycle Fatigue for a Car’s Front Sub-Frame

This paper based on the data of enterprise’s bench test, first set up the finite element analysis model for the front sub-frame by using the of professional finite element analysis software and fatigue life analysis software, then got the distribution information (such as the situation and the cycles) for the front sub-frame after analyzing, with these messages not only easily found out the danger area, but also provided reference for bench test improving, once more found a method that can forecast the life for mechanical products.

Development of automotive engine cradle by hydroforming process

The hydroforming technology may bring many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower springback, improved strength and durability and design flexibility. In this study, the whole process of front sub-frame parts development by tube hydroforming using steel material having tensile strength of 440 MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydroformability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape in automotive engine cradle by the hydroforming process were carefully investigated. Overall possibility of hydroformable engine cradle parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydroforming. At the die design stage, all the components of prototyping tool are designed and interference with the press is examined from the point of deformed geometry and local thinning.

차량용 서브프레임의 동특성 해석

The vibration of Powertrain are one of the import design characteristics of a vehicle. Powertrain is mostly mounted to the front subframe and powertrain mounting has an important role in determining the vehicle vibration characteristics. In this paper, the accuracy of the vibration analysis for the front subframe is discussed. The dynamic characteristic of subframe are measured from vehicle test and the finite element model updating are performed that natural frequency, mass and MAC of the experimental and theoretical modal analysis are compared. The subframe mounting stiffness are obtained the iteration method based on the vibration of subframe from vehicle test. Finally, the result of dynamic analysis which is operated dynamic load is compared with experimental one of vehicle test.

Analysis of crash response of aluminium foam-filled front side rail of a passenger car

The objective of this paper is to gain an understanding of the reinforcing effect by aluminium foam-filling for the front side rail and subframe structure of a passenger car. The reinforcing effect by aluminium foam-filling on two major collapsing modes, axial compression and bending, is studied. The front rail is divided into axial collapse and a bending collapse parts, and the crush response of each is investigated by varying wall thickness and the aluminium foam strength. The effect of the anisotropy of aluminium foam on the crush response of the front side rail structure is also studied by varying the orientation of aluminium foam. The sensitivity analysis of wall thickness and aluminium foam strength on the energy absorption and the specific energy absorption is made in axial compression and bending collapse. A summary of optimisation process of aluminium foam-filled front rail structure is given as a design example. The optimum design with regard to weight efficiency and crash energy absorption is determined using “Design of Experiment” and “Response Surface Method”.