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In this work, the development of a hybrid lightweight automotive chassis control arm is demonstrated. It includes the development of a new simulation method for designing metal — LFT (long fiber-reinforced thermoplastics) rehybrid parts and the new hybrid forming method for its manufacture. Beginning with the original geometry of a series steel chassis control arm, the design was optimized for the hybrid forming process where a steel sheet part is reinforced by an LFT rib structure, and both parts are joined by an LFT layer. For this purpose, a new FE optimization process chain was established. The thickness of the sheet metal and LFT layers, the geometry and thickness of the ribs of the hybrid control arm could be determined to meet both mechanical and light weight requirements. Afterwards, a suitable tooling concept and process for the hybrid forming were developed and tested. The forming behavior of two different steel grades along with an LFT was demonstrated and analyzed with the help of 3D measurement techniques and relevant section cuts. Finally, a weight reduction of nearly 20 % compared to the original component was realized with the hybrid forming process.

Many forming failures such as tearing and wrinkling are encountered during sheet metal forming operations, and it is important for manufacturers to find a quick solution for these failures that hinder the production of a desired part. The theory of inventive problem-solving (TRIZ) is a problem-solving method that considers the patents issued in the past that have been useful in solving problems across a variety of industries. In this paper, TRIZ methodology was utilized to solve the tearing problem occurring during the forming of the lower control arm (automotive suspension part) without altering the desired shape and material of the part. For this purpose, a contradiction matrix was developed and the four different TRIZ principles of segmentation, taking out, the other way around, and parameter change were implemented in four different experiments. Of the conducted experiments, the experiment in which the TRIZ principles of segmentation, taking out, and parameter change were implemented together resolved the problem in a way that was acceptable and feasible for mass production of the lower control arm. WOS:000665698700001 2-s2.0-85116006399

The abnormal noises, such as clunking and popping, are usually generated when the car turns or drives over bumps. It could happen frequently when the free gap (clearance) values in the axial direction of the lower control arm ball joint are higher than normal values. The spherical surface of the ball stud is commonly assumed to have been corroded by foreign substances such as water, and the rough surface of the corroded ball stud accelerates the abrasion of the bearing contact portion to increase the free gap. Thus, the dust cap material and shape have been improved over time. However, there are still recurrences. The objective of this study was to evaluate two ball studs with different plating thicknesses and one uncoated sample from the reproducibility test simulating vehicle behavior conditions under environment test conditions. The findings of this study were as follows: First, the ball stud plating is advantageous in corrosion resistance, however, the thickness of the plating is uneven and the surface becomes rough with time, thereby accelerating the abrasion of the bearing contact portion. Second, as the surface of the ball stud wears, oscillating torque decreases and the axial free gap increases, which is more disadvantageous as the thickness of the ball stud sphere becomes thicker. Therefore, uncoated ball joint was defined as the best option.

This paper presents the structural vibration and acoustic radiation of a multibody vehicle system in interior and exterior under cleat impact excitations. The entire structure model, which consists of a hyper-elastic tire, a 17-inch lightweight wheel, a rotatable hub, a high-strength knuckle, a control arm and a spring-damper suspension, is a quarter vehicle to simulate transient response when passing through a cleat. The normal acceleration of a vibrating structure surface is applied as an acoustic noise source. A structural-acoustic coupling is employed to consider the interactive effects of the coupled system. The influence of the structure-borne noise can be confirmed by the frequency-correlation analysis between vibration acceleration and acoustic pressure. A sound pressure level (SPL) for near-field radiation is calculated by the finite element method (FEM). In addition, acoustic characteristics such as sound intensity in the passenger cabin are calculated through the boundary element method (BEM). The cleat impact experiment in a hemi-anechoic chamber is presented and validated in detail.

In this paper, the author has attempted to investigate the effects of different loading conditions including axial and multiaxial variable amplitude loading (VAL) on the fatigue life assessment of automotive components under various maneuvers. To this end, a case study was conducted on the cast iron steering knuckle of a passenger car. In fact, the various VAL histories are entered on the three joints of knuckle, namely steering linkage, lower control arm, and MacPherson strut. However, previous studies have shown that this high super-critical component fails through the steering linkage. Moreover, the rotation of the steering linkage is the most destructive load. Hence, in this research, different loading cases such as axial (destructive load as means 1 channel), multiaxial (only relates to loading on the joint of knuckle and steering linkage means 3 channels), and full multiaxial (including all loading time histories means 9 channels) were considered. Afterward, finite element analysis was performed for each case, and fatigue life of the component was predicted under different conditions. Next, fatigue life of the component was evaluated using the time histories of stress tensor in the root of steering linkage which is extracted by transient dynamic analysis and applying probabilistic approach based on the Liu–Zenner equivalent stress criterion. Eventually, the responses from both techniques were compared in different cases. The results reveal that life predicted using two methods are slightly different. But, the results of probabilistic approach are more accurate than the results of FEM in comparison with experimental data for the axial state. Also, one of the major achievements of this study is that for the components with complex geometry and under multi-input loading like the steering knuckle, it is essential to perform fatigue analysis by considering all real conditions and cannot be only focused to the destructive loading.

The semi-solid casting process has the advantage of providing reliable mechanical aluminum parts that work continuously in dynamic as control arm of the suspension system in automotive vehicles. The quality performance of dynamic control arm is related to casting mold and gating system designs that affect the fluidity of semi-solid metal during filling the mold. Therefore, this study focuses on improvement in mechanical performance, depending on material characterization, and casting design optimization, of suspension control arms made of A357 aluminum semi-solid alloys. Mechanical and design analyses, applied on the suspension arm, showed the occurrence of mechanical failures at unexpected weak points. Metallurgical analysis showed that the main reason lies in the difficult flow of semi-solid paste through the thin thicknesses of a complex geometry. A design modification procedure is applied to the geometry of the suspension arm to avoid this problem and to improve its quality performance. The design modification of parts was carried out by using SolidWorks design software, evaluation of constraints with ABAQUS, and simulation of flow with ProCast software. The proposed designs showed that the modified suspension arm, without ribs and with a central canvas designed as Z, is considered as a perfect casting design showing an increase in the structural strength of the component. In this case, maximum von Mises stress is 199 MPa that is below the yield strength of the material. The modified casting mold design shows a high uniformity and minim turbulence of molten metal flow during semi-solid casting process.

This study shows topology optimization of lower control arm (LCA), made of carbon fiber reinforced plastic (CFRP), that was originally composed of aluminum alloy. By mean-field homogenization (MFH) method, averaged mechanical properties of CFRP are applied to FEM analyses of 3D LCA model. The design target is to reduce the LCA weight while satisfying the multiple constraints including required stiffness and durability conditions at the same time. As a result, authors propose the new design of CFRP LCA with 30 % weight reduction compared to Al alloy LCA.

Funder: NIHR Cambridge Biomedical Research Centre, Funder: Engineering and Physical Sciences Research Council; doi: http://dx.doi.org/10.13039/501100000266, Background: For many disease areas, there are often treatments in different stages of the development process. We consider the design of a two-arm parallel group trial where it is planned to add a new experimental treatment arm during the trial. This could potentially save money, patients, time and resources; however, the addition of a treatment arm creates a multiple comparison problem. Current practice in trials when a new treatment arm has been added is to compare the new treatment only to controls randomised concurrently, and this is the setting we consider here. Furthermore, for standard multi-arm trials, optimal allocation randomises a larger number of patients to the control arm than to each experimental treatment arm. Methods: In this paper we propose an adaptive design, the aim of which is to adapt the sample size of the trial when the new treatment arm is added to control the family-wise error rate (FWER) in the strong sense, whilst maintaining the marginal power of each treatment-to-control comparison at the level of the original study. We explore optimal allocation for designs where a treatment arm is added with the aim of increasing the overall power of the study, where we define the overall power to be the probability of detecting all treatments that are better than the control. Results and conclusions: An increase in sample size is required to maintain the marginal power for each pairwise comparison when adding a treatment arm if control of the FWER is required at the level of the type I error in the original study. When control of the FWER is required in a single trial which adds an additional experimental treatment arm, but control of the FWER is not required in separate trials, depending on the design characteristics, it may be better to run a separate trial for each experimental treatment, in terms of the number of patients required. An increase in overall power can be achieved when optimal allocation is used once a treatment arm has been added to the trial, rather than continuing with equal allocation to all treatment arms.

Some vehicle components are developed by setting target weights to the gram level at their design stages to accomplish a lightweight design. Recently, there have been many studies that have focused on lightweight design through the use of ultra-high-strength steels. However, a lightweight design can face many challenges if the reliability of the analysis is not also secured at the design stage. Such challenges include difficulties in coupled analyses when the file formats are different among PAM-STAMP, ABAQUS, and NASTRAN. In this study, we developed a mapping interface that enables mapping between the file formats of various software programs. Buckling analysis was coupled to the forming analysis, in which pre-strain test data were applied in considering the material’s strain hardening, to evaluate the rigidity of the front lower control arm that controls the wheels and transfers loads. The influence of forming effects on endurance was evaluated, and residual stresses around the weld zone were calculated. A comparison of experimental and analytical results indicated that the proposed analysis was highly reliable.

Bending springback plays an important role in hydroforming of curved hollow components, and the effect will be more apparent with the increase of the strength of the material. In order to predict and eliminate the effect of springback on hydroforming process, springback of DP590 welded tube was investigated in computer numerical control (CNC) bending process using theoretical analysis, numerical simulation, and experimental methods. The effects of the bending angles, the diameter-thickness ratio d/t, and the relative bending radius R/d on springback are studied, and the influence factor of the weld position is considered. The theoretical and experimental results show that the springback of the DP590 welded tube with 65 mm in diameter and 2.6 mm in thickness varies within the range from 4.0 to 4.9 % and the amount of springback is influenced by the tube diameter and thickness. The springback reduces from 7.0 to 3.5 % when the diameter-thickness ratio is increasing from 10 to 40. On the contrary, the springback increases from 3.7 to 7.2 % when the relative bending radius is increasing from 1.2 to 4.0. The effect of weld position on springback is very little, but it has a negative effect on defects of hydroforming and wall thickness distribution. It is liable to crack when hydroforming if the weld locates on the outside or neutral layer of the bend. Finally, springback rules and weld effect are applied to form a control arm. A sound part had been successfully manufactured to avoid flash and crack defects considering the appropriate springback compensation and weld position.

Taking the automobile control arm as the research object, using MAGMASOFT, to simulate the squeeze casting process, the position of the shrinkage cavity and shrinkage defects in the casting process is accurately predicted. The results show that there exist shrinkage defects in the end and middle of the upper arm. The top of the upper arm is partially squeezed, and partial squeeze pressure is 130 MPa, the hotspot is eliminated. In the middle of the upper arm, the cooling line is added, so the control arm is whole to meet the order of solidification principle, and shrinkage defects are eliminated.

This paper presents shape optimization of lower control arm considering multi-disciplinary (stiffness, strength and durability) constraint conditions. As non-linearity of strength and durability is large out of the design constraint conditions and performance indexes are defined as min-max values, sensitivity is not reflected and instead, a sequential approximate optimization (SAO) method using a meta-model is suggested. In order to verify the efficiency of the suggested design method, shape optimization design of a 1 piece-typed lower control arm for compact cars is conducted. The design target aims to meet the multi-disciplinary (stiffness, strength and durability) design constraint conditions and at the same time, intends to minimize the weight. Design variables are 3 shape vectors and 1 thickness while design constraint conditions include 2 stiffness, 12 strength and 26 durability variables, featuring a big design problem. As a result, the design problem is solved in total 3 interation and the optimal model meets all of the design constraint conditions and reduces the weight by about 200 grams comparing with that of the initial model. Thus, the suggested design method is an appropriate method suitable for shape optimization design.

A Virtual Proving Ground (VPG) is a vehicle simulation environment used for evaluating durability of the suspension elements. Among the components that comprise the VPG system, the tire model with its complex nonlinear characteristics has most significant impact on the credibility of the estimated durability. This research proposes a method for generating an equivalent road profile as a way to compensate for the limits involved in modeling details of the tire characteristics. The method first identifies the frequency response function from the road heights to the spindle forces, which would contain rich information on the tire’s effect on the vehicle dynamics. Then it back-calculates a road profile using this model and the spindle force measurement. Finally the solution is updated iteratively until it yields the spindle forces close to their measured values. Using the proposed method, an equivalent road profile was successfully generated from a spindle force measurement collected from a physical durability test. In order to investigate validity of the proposed method, durability analysis was performed for a suspension component — a lower control arm. From the preliminary VPG simulation results, it was confirmed that the estimated fatigue life agreed well with the estimation based upon the force measurement.

Suppose that there are K experimental arms and a control arm in a study with survival as the primary endpoint. We consider a Dunnett-type testing procedure to discover the experimental arms that have longer survival distributions than the control arm using the log-rank statistic. In order to adjust for the multiplicity of the testing procedure, a Dunnett-type test controls the family-wise error rate (FWER). We derive the sample size required for a given parameter setting on the FWER level, power, survival distributions of the K + 1 arms, accrual period (or accrual rate), and additional follow-up period. Through simulations, derived sample sizes are shown to accurately maintain the power. The proposed method is applied to a real clinical trial.

CompARE is a pragmatic multicentre open-label phase III randomised controlled trial aiming to determine if intensification of treatment in intermediate and high risk oropharyngeal cancer (OPC) patients improves the definitive primary outcome measure of overall survival time. The trial evaluates three experimental arms separately against one control arm using a MAMS design, with three interim assessments of disease-free survival time. Experimental arms will be discontinued if they fail to meet the interim assessment criteria. The timing of these assessments is driven by the number of control events, with the study engineered so these occur approximately annually. The design characteristics will be presented. A potential additional experimental arm for treatment of OPC was proposed during CompARE initiation, and could be introduced into the trial after one year if approved. The straightforward implication is an increase in the number of patients required to recruit per year or an increase in trial duration. However in a complex MAMS design, a balance of multiple factors such as a feasible sample size, trial duration and appropriate number and timing of interim assessments with appropriate statistical error rates, have to be carefully considered. Using the nstage and artpep programs in Stata, a review of the operating characteristics of both the original design and expanded design with the new experimental arm was undertaken. The recruitment and statistical implications of the addition of the new experimental arm and an evaluation of the study duration to changes in recruitment predictions will be presented.

This paper presents a formulation for incorporating nonlinear viscoelastic bushing elements into multibody systems. The formulation is based on the assumption that the relaxation function can be expressed as a sum of functions which are nonlinear in deformation and exponentially decreasing in time. These forces can represent elastomeric mounts or bushings in automotive suspension systems. The numerical implementation of the nonlinear viscoelastic bushing model into a general purpose rigid multibody dynamics code is described, and an extension of the formulation is also presented wherein component flexibility is included. Model validation was performed by comparing experimental data to simulation results obtained using the nonlinear viscoelastic model and a nonlinear elastic model. The experimental data were obtained at the Center's facilities by testing an automotive lower control arm/bushing system, subjected to a simulated road load event. The comparison demonstrates the better load prediction capability of the viscoelastic bushing model compared to the conventional model.