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Correct shifting schedule of vehicle coasting mode play a vital role in improving vehicle comfort and economy. At present, the calibration of the transmission shifting schedule ignores the impact of vehicle’s dynamic mass. This paper proposes a method for optimizing the shifting schedule of the coasting modes with gear based on the dynamic mass identification of the vehicle. This method identifies the dynamic mass of the vehicle during driving and substitute them into the process of solving the shifting schedule parameters. Then we get the optimal shifting schedule. At first, establish the Extended Kalman Filter to Pre-process the experimental data, reducing errors caused by excessive data fluctuations. Then, establishing a weighted squares estimation model based on particle swarm optimization to identify the dynamic mass of the vehicle.

The lightweighting potential brought by advanced high strength steels (AHSS) was studied on automotive exterior panels. The dent resistance was selected as a measure to quantify the lightweighting since it is the most crucial for exterior panels. NEXMET® 440EX and 490EX, which possess both the surface quality and high strength, are evaluated and compared with BH210 and BH240. The denting analysis was conducted first on representative plates with different curvatures to simulate the dented areas on door outer, roof and hood panels. In addition, both 1% and 2% pre-strain and baking scenarios are considered for this plate, which represent the most common situations for exterior panels. The maximal dent load that the plates can sustain was calculated and compared for all those steel grades. Then the dent resistance analysis was conducted on a selected door outer panel. The minimum gauge required to meet the dent resistance performance was obtained.

As vacuum suction cups are widely used in stamping plants, it becomes urgent and important to understand their performance and failure mode. Vacuum suction cups are employed to lift, move, and place sheet metal instead of human hands. Occasionally the vacuum cups would fail and drop parts, even it would cause expensive delays in the production line. In this research, several types of vacuum cups have been studies and compared experimentally. A new tensile device and test method was developed to measure the pulling force and deformation of vacuum cups. The digital image correlation technique has been adopted to capture and analyze the contour, deformation and strain of the cups under different working conditions. The experimental results revealed that the relevant influential parameters include cup type, pulling force angles, vacuum levels, sheet metal curvatures, etc.

Fatigue testing is a specialized form of mechanical testing that is performed by applying cyclic loading to a coupon or structure. Two common forms of fatigue testing are load controlled high cycle and strain controlled low cycle fatigue. Some strain measurement device, such as extensometers, strain gage, that are often used as a feedback sensor on strain controlled fatigue test. However, in applications where strain controlled fatigue testing could face some extreme conditions as well as high temperature and unusual sizing which requires the strain measurement to be nondestructive and full field. While digital image correlation (DIC), an advanced optical measurement technique, has a decent solution on challenges of fatigue testing measurement. The problem is how to turn DIC from a measurement system to a feedback controller unit. Due to the developments in camera and computation techniques, the sequential process can now be performed as a parallel process.

Springback is a major concern in stamping of advanced high strength steels (AHSS). The existing computer simulation technology has difficulty predicting this phenomenon accurately even though it is well developed for formability simulations. Great efforts made in recent years to improve springback predictions have achieved noticeable progress in the computational capability and accuracy. In this work, springback simulation studies are conducted using FEA software LS-DYNA®. Various parametric sensitivity studies are carried out and key variables affecting the springback prediction accuracy are identified. Recently developed simulation technologies in LS-DYNA® are implemented including dynamic effect minimization, smooth tool contact and newly developed nonlinear isotropic/kinematic hardening material models. Case studies on lab-scale and full-scale industrial parts are provided and the predicted springback results are compared to the experimental data.

Edge cracking is one of the major formability concerns in advanced high strength steel (AHSS) stamping. Although finite element analysis (FEA) together with the Forming Limit Diagram has been widely used, it has not effectively predicted edge cracking. Primary problems in developing a methodology to insure that parts are safe from edge cracking are the lack of an effective failure criterion and a simple and accurate measurement method that is not only usable in both die tryout and production but also can be verified by finite element analysis. The intent of this study is to develop a methodology to ensure that parts with internal cutouts, such as a body side panel can be produced without edge cracking. During tryout and production, edge cracking has traditionally been detected by visual examination, but this approach is not adequate for ensuring freedom from edge cracking.

An experimental study of springback was conducted for a hat channel section with varying cross sections and controlled gap between punch and die. The channel section was formed in a single step forming process with upper pressure pad. DP590 steel was compared to a group of high strength steels (HSS), e.g. HSLA270, 340 and 420. In addition, sidewall curl phenomenon was studied utilizing bending under tension test. This paper describes methodology of experiment and discusses springback related results. It also offers recommendations that can be applied to die-punch gap control or material substitution situations. The results of this investigation can be used to verify accuracy of springback predictions in finite element analysis (FEA).

Advanced high-strength steel (AHSS) is gaining popularity in the automotive industry due to its higher final part strength with the better formability compares to the conventional steel. However, the edge fracture occurs during the forming procedure for the pre-strained part. To avoid the edge fracture that happens during the manufacturing, the effect of pre-strain on edge cracking limit needs to be studied. In this paper, digital image correlation (DIC), as an accurate optical method, is adopted for the strain measurement to determining the edge cracking limit. Sets of the wide coupons are pre-strained to obtain the samples at different pre-strain level. The pre-strain of each sample is precisely measured during this procedure using DIC. After pre-straining, the half dog bone samples are cut from these wide coupons. The edge of the notch in the half dog bone samples is created by the punch with 10% clearance for the distinct edge condition.

Vehicle weight reduction is a significant challenge for the modern automotive industry. In recent years, the amount of vehicular components constructed from aluminum alloy has increased due to its light weighting capabilities. Automotive manufacturing processes, predominantly those utilizing various stamping applications, require a thorough understanding of aluminum fracture predictions methods, in order to accurately simulate the process using Finite Element Method (FEM) software or use it in automotive engineering manufacture. This paper presents the strain distribution of A5182 aluminum samples after punch impact under various conditions by Digital Image Correlation (DIC) system, its software also measured the complete strain history, in addition to sample curvature after it was impacted; therefore obtaining the data required to determine the amount of side-wall-curl (Aluminum sheet springback) present after formation.

Vehicle front panel is an interior part which has a major impact on the consumers’ experience of the vehicles. To keep a good appearance during long time aging period, most of the front panel is designed as a rough surface. Some types of surface defects on the rough surface can only be observed under the exposure of certain angled sun light. This brings great difficulties in finding surface defects on the production line. This paper introduces a novel polarized laser light based surface quality inspection method for the rough surfaces on the vehicle front panel. By using the novel surface quality inspection system, the surface defects can be detected real-timely even without the exposure under certain angled sun light. The optical fundamentals, theory derivation, experiment setup and testing result are shown in detail in this paper.

This paper represents the development of a new design methodology based on data mining theory for decision making in vehicle crashworthy components (or parts) development. The new methodology allows exploring the big crash simulation dataset to discover the underlying complicated relationships between vehicle crash responses and design variables at multi-levels, and deriving design rules based on the whole vehicle safety requirements to make decisions towards the component and sub-component level design. The method to be developed will resolve the issue of existing design approaches for vehicle crashworthiness, i.e. limited information exploring capability from big datasets, which may hamper the decision making and lead to a nonoptimal design. A preliminary design case study is presented to demonstrate the performance of the new method. This method will have direct impacts on improving vehicle safety design and can readily be applied to other complex systems.

Spring-back phenomena are critical in stamping procedures for advanced high strength steel. An analytical model is developed to predict the spring-back effect for a U-channel part with post-stretching process. The stress distribution is obtained by direct application of material constitutive relationship. The subjected loading conditions are sequentially bending, (un-bending), and uniform stretching, based on different zones in the part. Both the loading history and the friction effects are considered in the model. The bending moments are obtained to generate a theoretical spring-back shape. Great performance in spring-back control is achieved by applying certain high level of external forces. FE simulation is conducted for the identical stamping process with post-stretching. Good correlation is observed between the analytical and numerical solutions/experimental results under various scenarios.

Dimensional accuracy of punched hole is an essential consideration for high-quality sheet metal forming. An out-of-shape hole can give rise to manufacturing issues in the subsequent production processes thus inducing quality defects on a vehicle body. To understand the effects of punch shapes and cutting configurations on punched hole diameter deviations, a systematical experimental study was conducted for multiple types of AHSS (DP1180, DP980, DP590) and one mild steel. Flat, conical and rooftop punches were tested respectively with three cutting clearances on each material. The measurement results indicated different diameter enlargement modes based on the punch profiles, and dimensional discrepancies were found to be more significant with the stronger materials and higher cutting clearance. To uncover the mechanism of punched hole enlargement, a series of finite element simulations were established for numerical investigation.

The elevated strength of advanced high strength steels (AHSS) leads to enormous challenges for the sheet metal processing, one of which is hole punching operation. The total tonnage must be estimated at each trimming stage to ensure successful cutting and protect the press machine. This paper presents the effects of hole punch configurations on the punching force with the consideration of punch shape, cutting clearance and material grade. The hole punching experiments were performed with DP590, DP980, DP1180 and one mild steel as a reference. The punching force coefficient is defined and presents a negative correlation with the material strength based on the experimental data. Surface quality was examined to analyze the damage accumulation during the punching process. The cutting mechanisms with various punch shapes were revealed through an extensive finite element simulation study.

Twist spring-back would interfere with stamping or assembling procedures for advanced high strength steel. A “homeopathic” resolution for controlling the twist spring-back is proposed using unbalanced post-stretching configuration. Finite element forming simulation is applied to evaluate and compare the performance for each set of unbalanced post-stretching setup. The post-stretching is effectuated by stake bead application. The beads are separated into multiple independent segments, the height and radii of which can be adjusted individually and asymmetrically. Simulation results indicate that the twist spring-back can be effectively controlled by reducing the post-stretching proximate to the asymmetric part area. Its mechanism is qualitatively revealed by stress analyses, that an additional but acceptable cross-sectional spring-back re-balances the sprung asymmetrical geometry to counter the twist effect.

Light-weighting vehicles cause an increase in Aluminum Alloy stamping processes in the Automotive Industry. Surface finish and lubricants of aluminum alloy (AA) sheet play an important role in the deep drawing processes as they can affect the friction condition between the die and the sheet. This paper aims to develop a reliable and practical laboratory test method to experimentally investigate the influence of surface finish, lubricant conditions, draw-bead clearances and pulling speed on the frictional sliding behavior of AA 6XXX sheet metal. A new double-beads draw-bead-simulator (DBS) system was used to conduct the simulated test to determine the frictional behavior of an aluminium alloy with three surface lubricant conditions: mill finish (MF) with oil lube, electric discharge texture (EDT) finish with oil lube and mill finish (MF) with dry lube (DL).

Although numerical simulation techniques for sheet metal forming become increasingly maturing in recent years, prediction of springback remains a topic of current investigation. The main point of this paper is to illustrate the effectiveness of a modelling approach where static implicit schemes are used for the prediction of springback regardless whether a static implicit or dynamic explicit scheme is used in the forming simulation. The approach is demonstrated by revisiting the 2-D draw bending of NUMISHEET'93 and numerical results on two real world stampings.

The use of cyclic corrosion tests which consist of salt spraying, humidifying, and drying phases is desirable in the evaluation of the corrosion performance of automotive body panels. In this work, coupons of zinc-coated steel and of cold rolled steel were exposed to a defined cyclic corrosion test (CCT) which has shown to be suitable for simulating diverse outdoor conditions for evaluating the cosmetic corrosion of precoated steel. Micro-environment data in the gap of lapped panel specimens, such as wetness, corrosion rate of test materials, pH value, chloride content, have been obtained during the CCT test. The galvanic current flowing between a gold electrode and the test materials was measured to monitor the degree of wetness inside the crevice. The results show that the surface of the test materials never became really dry even during the dry period of the CCT cycle. Furthermore, the wetness during wet and dry periods in the crevice increased with increasing number of CCT cycle.

A V-engine high pressure fuel pipe have experienced several failures during dyno engine validations at brazed joints due to combination of static and dynamic engine loads. The braze fillet experience high local stress concentration with large gradients and it was critical to capture strain contour at this spot to properly understand the failure. Strain gauges was used to measure strain but was incapable of capturing the braze fillet due to the small fillet radius and lack of real estate to install the gauge (braze fillet radius ~ 0.10 mm). A whole field optical experiment method Digital Image Correlation was utilized to successfully captured strain contour at area of interest and results fed back to computational model.

Unexpected severe failures occur during the warm forming procedure of carbon fiber material due to the existence of extremely large deformation/strain. To evaluate this failure, a good understanding the accurate material property under certain loading is important to evaluate the forming feasibility of carbon fiber material. Also, a clear connection between the fiber orientation and the material property helps to increase the accuracy of the forming prediction. Therefore, an experimental test is needed to evaluate the material property as well as the fiber orientation. In this paper, a uniaxial tension test for the prepreg carbon fiber under the warm forming condition is performed. A halogen lamp is used to heat the specimen to reach the warm forming condition. A 3D Digital Image Correlation (3D-DIC) is utilized to measure the material property and the fiber orientation in this test, along with a DIP system.