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Critical Concepts of Tolerance Stacks ASME Y14.5 1994, 2009, 2018 – Foundational Level

2022-04-04
Using tolerance stacks ensures that parts fit together properly, reducing scrap and rework, thereby increasing value. This 2-day foundational-level course explains how to use tolerance stacks to analyze product designs and how to use geometric tolerances in stacks. You’ll learn the essential methods used for creating 1D part and assembly tolerance stacks, including these six critical concepts: 1. The importance of stacks 2. The two-column stack method using the SAE stack spreadsheet 3. Determining a stack path 4. Creating 1D part and assembly stacks 5. Interpreting GD&T 6.
Technical Paper

Padded Self-Piercing Riveting (P-SPR) on magnesium high pressure die casting

2022-03-29
2022-01-0249
Padded self-piercing riveting (P-SPR) is a newly developed multi-material joining technology to enable less ductile materials to be joined by self-piercing riveting (SPR) without cracking. A deformable and disposable pad was employed to reduce the stress distribution on the bottom surface by supporting the whole bottom sheet continuously during rivet setting process. To verify the P-SPR process, 2.0mm thick 6061-T6 wrought aluminum was joined with 3.2mm thick coated AM60B magnesium high pressure die casting (HPDC) by using 1.0mm thick dual-phase 600 (DP600) steel as the pad. Regular SPR processes with 2 different die geometries were studied as a comparison. Compared to the regular SPR processes, P-SPR demonstrated advantages on coating protection, crack mitigation and joint strength.
Technical Paper

A study on editing method of road load spectrum of automobile rubber isolator using time-frequency domain methods

2022-03-29
2022-01-0272
In order to enhance the efficiency of durability testing of automobile parts, a time-frequency domain accelerated editing method of road load time series of rubber mount on powertrain was discussed. Based on Stockwell Transform method and Accumulative Power Spectral Density, a new time-frequency domain accelerated editing method (ST-APSD) was proposed. The accumulative power spectral density was obtained by ST of the load time series signal of automobile powertrain rubber mounting force which is acquired by the real vehicle in the test field. Based on the accumulative power spectral density, the threshold value was proposed to identify and delete the small damage load fragments, and then the acceleration spectrum was obtained.
Technical Paper

A fatigue life prediction method of rubber material for Automobile vibration isolator under road load spectrum

2022-03-29
2022-01-0253
Automobile rubber isolator was subjected to random load cycle for a long time in the service process, and its main rubber material for vibration isolation was prone to fatigue failure. Since the traditional Miner damage theory overlooked the load randomness, it had a prediction error problem. In order to improve the prediction accuracy of rubber fatigue life, the traditional Miner damage theory was modified by random uncertainty theory to predict the rubber fatigue life under random load. Firstly, the rubber dumbbell-shaped test column, which was vulcanized from rubber materials commonly used in vibration isolators, was taken as the research object. The uniaxial fatigue test of rubber under different strain amplitudes and strain mean values was carried out. Then the fatigue characteristic curve of rubber with equivalent strain amplitude as the damage parameter was established.
Technical Paper

Numerical Investigation on the Internal Flow Field of Electronic Expansion Valve as the Throttle Element

2022-03-29
2022-01-0318
As one of the key components of the heat pump system, the electronic expansion valve mainly plays the role of throttling and reducing pressure in the heat pump system. The refrigerant flowing through the orifice will produce complex phase change. It is of great significance to study the internal flow field by means of CFD calculations. Firstly, a three-dimensional fluid model is established and the mesh is divided. Secondly, the phase change model is selected, the material is defined and the boundary conditions are determined. According to the principle of the fluid passing through thin-walled small holes, the flow characteristics of electronic expansion valve are theoretically analyzed. Then the flow characteristics of expansion valve are numerically calculated, and a bench for testing mass flow rate of the expansion valve is built. Then the theoretical value, CFD value and experimental value are compared to verify the correctness of the established three-dimensional fluid model.
Technical Paper

Numerical Assessment of Tribological Performance of Different Llow Viscosity Engine Oils in a 4-Stroke CI Light-Duty ICE

2022-03-29
2022-01-0321
Decreasing fuel consumption in Internal Combustion Engines (ICE) is a key target for engine developers in order to achieve the CO2 emissions limits during a standard cycle. In this context, reduction of engine friction can help meet those targets. The use of Low Viscosity Engine Oils (LVEOs), which is currently one of the avenues to achieve such reductions, is studied in this manuscript through a validated numerical simulation model that predicts the friction of the engine’s piston-cylinder unit, journal bearings and camshaft. These frictional power losses are obtained for four different lubricant formulations which differ in their viscosity grades and design. Results show a maximum friction savings of up to 6% depending on the engine operating condition, where the major reductions come from hydrodynamic-dominated components such as journal bearings, despite an increase in friction in boundary-dominated components such as the piston-ring assembly.
Technical Paper

An experimental approach for exploring electrified sliding wear of EVs powertrain gears in a pin-on-disc tester

2022-03-29
2022-01-0320
In contrast to conventional powertrains from internal combustion engine vehicles (ICEV), the tribological performance of powertrains of electric vehicles (EVs) must be further evaluated by considering new critical operation conditions such as electric environments. The operation of any type of electric motor produces shaft voltages and currents generated during rotation. Furthermore, the common application of inverters to convert DC voltage of the battery into AC voltage in EVs, intensifies this problem. It has been widely reported that the induced shaft voltages and currents can cause premature failure problems in a series of powertrain components such as bearings, seals, pads, and gears due to accelerated wear and/or fatigue. It is ascribed to effects of electric discharge machining (EDM), also named, sparking wear caused by shaft currents and poor dielectric strength of lubricants.
Technical Paper

An Accurate Analysis Method to Calculate Planetary Gear Set Load Sharing under Non-Torque Load

2022-03-29
2022-01-0653
Given their high-power density, large range of speed change, and reputation of being quieter than counter-shaft gear sets, planetary gear sets (PGS) have advantages to be applied in electric vehicle (EV) applications. Typical rear wheel drive automatic transmissions have only PGS in gearbox, and power is transferred by torque. Most electric drive units (EDU) equipped PGS are like a simplified front wheel drive automatic transmission. PGS is coupled with counter-shaft gear sets normally at planet carrier which has two functions: original planet pinion carrying and additional transfer gear mounting. The latter brings in non-torque power in PGS through the carrier. This condition hasn’t obtained enough attention by automotive gear researchers regarding to PGS load sharing calculation. Excluding non-torque load here causes underestimating gear and bearing uneven loads in both magnitude and variation. In extreme conditions, undersized parts would miss demanding durability requirements.
Technical Paper

Managing Trust along the CAN Bus

2022-03-29
2022-01-0119
Multiple approaches have been created to enhance intra-vehicle communications security over the past three decades since the introduction of CAN. The twin pair differential-mode communications bus is tremendously robust in the face of interference, yet physical access to the bus offers a variety of potential attack vectors whereby false messages and/or denial of service are easy to achieve. This paper seeks to evaluate extensions of a common-mode watermark-based authentication technique recently developed to improve authentication on the CAN bus by considering the watermark as a side-channel communications means for high value information. We also describe a variety of higher layer algorithms, with benefits and pitfalls, for employing the watermark as a physical-layer firewall. All of these results are backed by a software-defined radio (SDR) based hardware testbed.
Technical Paper

A DFSS approach to optimize the Hood design parameters to improve durability performance

2022-03-29
2022-01-0771
In the Vehicle front closure development process, it is very important to meet the durability functional attributes such as Fit and finish, slam event and ease of closing effort. Conventionally softer seal & bump-stop stiffness properties are required for better flushness, but a stiffer seal & bump-stop will help to arrest the hood over travel during the slam event. It is always a challenging and iterative process to arrive at an optimum combination of these design parameters to meet both the flushness and slam targets. This paper highlights the six sigma approach to identify the effect of various control factors like Seal & Bump stop stiffness, latch position, bump-stop design clearance to meet the durability functional attributes. This approach suggests optimum design which is less sensitive to noise factors such as build tolerances on the latch position and the bump-stop design clearance.
Technical Paper

Design of Engine mount bracket for impact load requirement

2022-03-29
2022-01-0758
The primary function of a powertrain mounting bracket is to support the powertrain system in all road conditions. Since it is impossible to change the supporting locations and types of support at a later stage of the development after the powertrain is packaged, the mounting brackets must be verified for all kinds of requirements like NVH, crash, durability and impact strength at the early design stage. Generally, all car manufacturers ensure powertrain mount bracket design through CAE against road load data (RLD), corresponding damage for cumulative strain or stress against specified service life requirements. However, it is challenging to simulate the impact load through CAE, which requires highly complex input data. The energy absorption characteristics of the powertrain mounting bracket are mainly influenced by two variables, the material and the design. Though a bracket may be sound in design for durability, there is a chance of failure due to impact loading.
Technical Paper

Visualization of Frequency Response Using Nyquist Plots

2022-03-29
2022-01-0753
Nyquist plots are a classical means to visualize a complex vibration frequency response function. By graphing the real and imaginary parts of the response, the dynamic behavior in the vicinity of resonances is emphasized. This allows insight into how modes are coupling, and also provides a means to separate the modes. Mathematical models such as Nyquist analysis are often embedded in frequency analysis hardware. While this speeds data collection, it also removes this visually intuitive tool from the engineer’s consciousness. The purpose of this paper is to review the fundamentals of Nyquist plots and their application to structural vibration. The behavior of a single degree of freedom system will be shown to be well described by a circle on its Nyquist plot. This observation allows simple visual examination of the response of a continuous system, and the determination of quantities such as uncoupled natural frequencies, modal damping factors, and uncoupled modes shapes.
Technical Paper

Design Optimization of Centrifugal Pump Using CFD Simulations, Metamodeling and Bayesian Inference

2022-03-29
2022-01-0787
Computational expenses aside, simulating and optimizing pumps operating at pressures near the liquid’s saturation pressure needs complete modeling of cavitation physics. This becomes critical in high-temperature applications since the saturation pressure increases with temperature and the pumps become more prone to cavitation. In the present work, the performance of a centrifugal pump was improved by delaying the sudden onset of cavitation at higher flow rates through constrained optimization of impeller geometry. The optimized designs generated over 25% higher head at the operating point, and performed better than the baseline design across the range of operation. Constraints were dictated by geometric/ packaging limitations in order to ensure that the optimized impeller can be retrofitted into an existing fluid-power system. A Gaussian Process Regressor (GPR) based metamodel was constructed utilizing a database of designs generated through Latin Hypercube Sampling (LHS).
Technical Paper

Sensitivity of Operational Safety Assessment (OSA) Metrics for Automated Vehicles to Measurement and Parameter Uncertainty

2022-03-29
2022-01-0815
As the deployment of automated vehicles (AVs) on public roadways expands, there is growing interest in establishing metrics that can be used to evaluate vehicle operational safety. The set of Operational Safety Assessment (OSA) metrics, that include several safety envelope-type metrics, previously proposed by the Institute of Automated Mobility (IAM) are a step towards establishing metrics. The safety envelope OSA metrics can be computed using kinematics derived from video data captured by infrastructure-based cameras and thus do not require on-board sensor data or vehicle-to-infrastructure (V2I) connectivity, though either of the latter data sources could enhance kinematic data accuracy. However, the calculation of some metrics includes certain vehicle-specific parameters that must be assumed or estimated if they are not known a priori or communicated directly by the vehicle.
Technical Paper

Whirl Analysis of an Overhung Disk Shaft System Mounted on Non-rigid Bearings

2022-03-29
2022-01-0607
Eigenvalues of a simple rotating flexible disk-shaft system are obtained using different methods. The shaft is supported radially by non-rigid bearings, while the disk is situated at one end of the shaft. Eigenvalues from a finite element and a multi-body dynamic tool are compared against an established analytical formulation. The Campbell diagram based on natural frequencies obtained from the tools differ from the analytical values because of oversimplification in the analytical model. Later, detailed whirl analysis is performed using AVL Excite multi-body tool that includes understanding forward and reverse whirls in absolute and relative coordinate systems and their relationships. Responses to periodic force and base excitations at a constant rotational speed of the shaft are obtained and a modified Campbell diagram based on this is developed. Whirl of the center of the disk is plotted as an orbital or phase plot and its rotational direction noted.
Technical Paper

The mechanism of spur gear tooth profile deformation due to interference-fit assembly and the resultant effects on transmission error, bending stress, and tip diameter and its sensitivity to gear geometry.

2022-03-29
2022-01-0608
Gear profile deviation is the difference in gear tooth profile from the ideal involute geometry. There are many causes that result in the deviation. Deflection under load, manufacturing, and thermal effects are some of the well-known causes that have been reported to cause deviation of the gear tooth profile. The profile deviation caused by gear tooth profile deformation due to interference-fit assembly has not been discussed previously. Engine timing gear trains, transmission gearboxes, and wind turbine gearboxes are known to use interference-fit to attach the gear to the rotating shaft. This paper discusses the interference-fit joint design and the mechanism of tooth profile deformation due to the interference-fit assembly in gear trains. A new analytical method to calculate the profile slope deviation change due to interference-assembly of parallel axis spur gears is presented.
Technical Paper

Development of high damping powertrain mount using thixotropic fluid

2022-03-29
2022-01-0612
Vibration isolation performance and damping performance of powertrain mount are important for improving NV and ride comfort performances of the vehicle, respectively. In this research, based on the principle of liquid sealed mounts, we focused on the fact that the ideal fluid viscosity differs depending on the input frequency. By combining the liquid resonance phenomenon and thixotropic fluid, we developed a technology that balances a high level between low dynamic spring rate and high damping, which are trade-off items for liquid sealed mounts. The thixotropic fluid was blended with ethylene glycol aqueous solution as a base solution and smectite nano-cray as a thixotropic agent. From the view point of the viscosity corresponding to the shear rate and the viscosity at the high shear point, the optimum concentration of smectite was shown to be 1.5 wt%.
Technical Paper

Damage-Induced Dynamic Tooth Contact Forces in Spur Gears with Root Cracks

2022-03-29
2022-01-0642
A finite element/contact mechanics formulation is used to analyze the dynamic tooth forces that arise from damage-induced vibrations in spur gear pairs. Tooth root crack damage of varying sizes are analyzed for a wide range of speeds that include resonant gear speeds. Healthy gears without damage can have contact loss nonlinearity where pairs of teeth normally in contact lose contact due to large amplitude vibration. When spur gear teeth have tooth root crack damage, the added localized compliance from the damage leads to a re-distribution of the forces on the individual gear teeth. These loads cause additional transient dynamic response in the gear pair. For certain speeds and sufficiently large tooth root cracks, the damage-induced dynamic response causes large enough vibration that tooth contact loss nonlinearity occurs. For some speeds near resonance, the damage-induced vibrations cause teeth that normally lose contact to remain in contact due to vibration.
Technical Paper

Study on Flow Rate and Flow Field Characteristics of Gerotor Pump with Multi-arc Combined Profile

2022-03-29
2022-01-0632
The working principle and performance test method of the gerotor pump with multi-arc combined profile are introduced. According to the formation method of the rotor tooth profile, the calculation method of the inner rotor tooth profile is introduced, and the meshing characteristics of the inner and outer rotors are analyzed. On this basis, a calculation method for the displacement and instantaneous flow rate of the gerotor pump with multi-arc combined profile is proposed. In addition, a calculation model of the flow field characteristics of the gerotor pump with multi-arc combined profile is established, and the validity of the model is verified by experiments. Based on the model of traditional single-arc gerotor pump and the model of the gerotor pump with multi-arc combined profile, the flow rate, internal flow velocity, pressure distribution and gas volume fraction distribution under different working conditions are calculated respectively.
Technical Paper

Design of Cylinder Block for Horizontal K-type configuration

2022-03-29
2022-01-0631
Cylinder block is the bulkiest component in engine. It undergoes severe thermal and mechanical loads. Also, cylinder block is multifunctional. It includes positioning of coolant and lubrication circuit, location of coolant and oil pumps, locating cylinder head to form closed combustion chamber, locating mounting points of engine, mounting of alternator, starting motor, and AC compressors. Hence, the cylinder block design should be the strong and robust enough to handle the forces induced by combustion. Taking this requirement as the base, cylinder block is designed for Horizontal K type configuration. In this research, the mounting points of cylinder block are decided based on the unbalance forces for the configuration and from the gas pressure forces. Rigid body dynamics approach is used for locating the mounting points of engine. Topology optimization is carried out to know the location of coolant circuit.
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