Ride improvement of vehicle suspensions with switchable inerter based on force cancellation strategy

Inerter is a recent advancement in vehicle suspension that have been shown to be capable of improving vehicle ride comfort, however its ride improvement is less encouraging in the parallel layout. This study investigated the possibility of further ride improvement brought by vehicle suspensions with a switchable parallel inerter instead. In this theoretical study, the inerter was assumed to be on-off switchable based on semi-active force cancellation strategy. A two-degree-of-freedom quarter vehicle model was used to evaluate several cases of suspension system, which included ordinary passive suspension as reference, a system with switchable inerter and a system with both switchable damper and inerter. The model was solved mathematically with random road profile and step profile as ground excitations. Results showed that the use of switchable inerter in parallel to spring and damper in the different test cases was capable of reducing vertical sprung mass acceleration by a healthy 12 %, which is far superior to a mere 2 % achieved by a passive parallel inerter, as well as comparable to that achieved by a switchable damper. When both sprung mass acceleration and dynamic tire load were considered, comparison made on the Pareto fronts indicated that the switchable capability of an inerter managed to further improve the Pareto optimal sets over those obtained for cases with passive inerter

Degree of Vehicle Overloading and its Implication on Road Safety in Developing Countries

The phenomenon of vehicle overloading is not new and has been discussed in relation to the adverse effects on road pavement damage, road safety and GHG emission. Although much has been said in the context of the more developed countries, there has not been much discussion on vehicle overloading in developing countries. In this study, the extent and degree of vehicle overloading in a developing country is established. Half of the 3-axle trucks were found to be overloaded and the degree of overloading is up to 101% of its legal weight limit! The effect of truck overloading on safety is discussed by establishing the relationship between truck stopping distance and gross vehicle weight for a certain travel speed. Comparison between actual overloading data for 2-axle, 3-axle and 4-axle trucks and the stopping distance illustrates the gravity of the situation which needs a comprehensive and effective strategy from the relevant agencies. Keywords: Road Safety, Vehicle Overloading, Traffic Accidents, Weigh-in-Motion, Stopping Distanc

Improving the Dynamic Characteristics of Body-in-White Structure Using Structural Optimization

The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process

A comparative analysis of experimental and numerical investigations of composite tubes under axial and lateral loading

Quasi-static tests are performed in order to determine the crash behavior of composite tubes. The specimens are made from woven fiber carbon/epoxy. The crash experiments show that the tubes crushed in a progressive manner from one end to the other of the tubes while delamination was - taking place between the layers. In the simulation works described in this paper the ANSYS explicit finite element code is used to investigate the compressive properties and crushing response of circular carbon tube subjected to static axial and lateral loading and the results are compared with the experimental work. To better understand the details of the crash process, thin multi layer shell elements are used to model the walls of the circular tube. Finally, the design optimization technique is implemented to find an optimum composite configuration that has the maximum failure load and absorbs the most energy. The crash performance of a carbon composite shell is compared with an optimum carbon tube from the experimental work. 2010, INSInet Publication.Scopu

Dynamic simulation of semi-active suspension systems for durability analysis

The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly for improvement in ride and handling, over the passive system. However, the durability of the suspension components resulting from this implementation received very little attention. Therefore, this research aims to examine the effect of employing a selection of semi-active control strategies on the components' durability. To achieve this early in the design cycle, accurate representations of the load histories must be generated as these histories are the prerequisite in predicting fatigue life. This requires an alternative modelling and simulation approach capable of combining the complexity of vehicle suspensions with semi-active controller models, and at the same time capable of maintaining accurate dynamic responses. In realizing this objective, a multi-body cosimulation approach has been proposed to predict these loads. Initially, efforts are centred on verifying the proposed method against conventional modelling and simulation techniques. This is followed by the evaluating the responses of vehicle suspension models of different complexities fitted with a selection of semi-active control strategies when subjected to transient and random road inputs. In an attempt to demonstrate the flexibility of MBS cosimulation, a magnetorheological damper model derived from experimental data is introduced,in which its dynamic characteristics and dynamic response are examined. It is concluded that the proposed method is capable of producing reasonably accurate load histories but at the expense of increasing solution time. Evaluation of the durability of a lower suspension arm of a multi-purpose passenger vehicle suggested that the two state semi-active strategies with skyhook damping control produced shorter fatigue life than from the conventional passives suspension systems

Multi-objective optimization of all-wheel drive electric formula vehicle for performance and energy efficiency using evolutionary algorithms

A new method based on constraint multi-objective optimization using evolutionary algorithms is proposed to optimize the powertrain design of a battery electric formula vehicle with an all-wheel independent motor drive. The electric formula vehicle has a maximum combined motor power of 80 kW, which is a constraint for delivering maximum vehicle performance with minimal energy consumption. The performance of the vehicle will be simulated and measured against different driving events, that is, acceleration event, autocross event, and endurance event. Each event demands a different aspect of performance to be delivered by the motor. The respective event lap time or energy rating will be measured for performance assessment. In this study, a non-dominated sorting genetic algorithm II and constrained multi-objective evolutionary algorithm based on decomposition by using differential evolution are employed to optimize the motor transmission ratio, motor torque scaling, and downforce scale of both front and rear wheels against the acceleration event to minimize energy consumption and event lap time while constraining the combined motor power of all wheels to not exceed 80 kW. The optimization will be performed through software-in-the-loop between MATLAB and VI-Grade, where the high-fidelity vehicle will be modeled in VI-Grade and optimization algorithms will be implemented on the host in MATLAB. Results show that the non-dominated sorting genetic algorithm II outperforms the constrained multi-objective evolutionary algorithm based on decomposition by using differential evolution in obtaining a wider distributed Pareto solution and converges at a relatively shorter time frame. The optimized results show a promising increase in the performance of the electric formula vehicle in completing those events with the highest combined performance scoring, that is, the lap time of acceleration events improves by 9.18%, that of autocross event improves by 6.1%, and that of endurance event improves by 4.97%, with minimum decrease in energy rating of 32.54%. © IMechE 2019

Reciprocating compressor valve damage estimation under varying speeds through the acoustic emission technique

Purpose: The purpose of this paper is to examine the effect of reciprocating compressor speeds and valve conditions on the roor-mean-square (RMS) value of burst acoustic emission (AE) signals associated with the physical motion of valves. The study attempts to explore the potential of AE signal in the estimation of valve damage under varying compressor speeds. Design/methodology/approach: This study involves the acquisition of AE signal, valve flow rate, pressure and temperature at the suction valve of an air compressor with speed varrying from 450 to 800 rpm. The AE signals correspond to one compressor cycle obtained from two simulated valve damage conditions, namely, the single leak and double leak conditions are compared to those of the normal valve plate. To examine the effects of valve conditions and speeds on AE RMS values, two-way analysis of variance (ANOVA) is conducted. Finally, regression analysis is performed to investigate the relationship of AE RMS with the speed and valve flow rate for different valve conditions. Findings: The results showed that AE RMS values computed from suction valve opening (SVO), suction valve closing (SVC) and discharge valve opening (DVO) events are significantly affected by both valve conditions and speeds. The AE RMS value computed from SVO event showed high linear correlation with speed compared to SVC and DVO events for all valve damage conditions. As this study is conducted at a compressor running at freeload, increasing speed of compressor also results in the increment of flow rate. Thus, the valve flow rate can also be empirically derived from the AE RMS value through the regression method, enabling a better estimation of valve damages. Research limitations/implications: The experimental test rig of this study is confined to a small pressure ratio range of 1.38–2.03 (free-loading condition). Besides, the air compressor is assumed to be operated at a constant speed. Originality/value: This study employed the statistical methods namely the ANOVA and regression analysis for valve damage estimation at varying compressor speeds. It can enable a plant personnel to make a better prediction on the loss of compressor efficiency and help them to justify the time for valve replacement in future. © 2019, Emerald Publishing Limited

Determination of Flow Patterns in Vertical Upward Two-Phase Flow Channel via Void Fraction Profile

Two-phase flow happens widely in the industrial plants and certain equipment. This paper attempts to study the characteristics of two-phase flow in a vertical piping system. This was achieved by comparing the void fraction, in the working fluid, by employing Constant Electric Current Method (CECM) with the actual observation using high-speed camera. The experiment requires a complete set of two-phase flow system information and was conducted based on various flow conditions. In order to carry out this experiment, the two-phase flow loop was constructed using a specific experimental apparatus and components. The flow channels were constructed using three pipes with three different inner diameters of 21.0 mm, 47.0 mm and 95.0 mm. The flow direction was vertical upward co-current flow with liquid superficial velocity range of 0.025 m/s to 3.0 m/s and gas superficial velocity range of 0.025 m/s to 3.0 m/s, depending on the size of the pipe. The flow pattern investigation focuses on experimental work, which was based on systematic observation and measurements using a high-speed camera and some measuring apparatus. The void fraction measurement using the CECM sensor was integrated into two-phase flow system with constant electric current running in the pipe and data acquisition system controlled virtually via LabVIEW software. Both result of the flow pattern and void fraction graph were then compared to determine the type of flow pattern from the void fraction graph. Information from the previous studies and experiments were collected and the assumption of any theoretical simplifications were used as a reference. According to the result, the flow pattern in pipe can be easily determined using CECM

Teething Troubles: Addressing the osteological paradox by comparing tooth crown size, enamel hypoplasia and age-at-death in the post-medieval population of Middenbeemster

There are two main issues that pose a problem with inferring health from the skeletons of past populations. Selective mortality refers to the fact that we can only research individuals who died and that they might not be representative of all individuals that existed at that age. Heterogeneity in frailty refers to the possibility that not all individuals are equal in terms of their risk of getting sick or dying and the factors that contribute to this difference might be hidden. This study addresses these two problems by looking at tooth crown sizes between individuals who died in childhood versus adulthood, as well as looking at the tooth crown sizes between teeth that show signs of physiological stress (enamel hypoplasia) and teeth that do not. Teeth might turn out smaller than their maximum genetic potential under developmental stress. It is researched if this same developmental stress caused individuals to be frailer than their peers, which might be reflected in reduced longevity and vulnerability to physiological stress episodes. The mesiodistal and buccolingual tooth crown sizes are measured for the entire dentition of 115 individuals between seven and 50+ years of age from the predominately 19th century Middenbeemster cemetery (the Netherlands). The results show that four buccolingual tooth crown dimensions (maxillary first molar, mandibular canine, first premolar and second molar) were significantly smaller for subadults than for adults, with all buccolingual dimensions having a tendency to be at least a bit smaller. For three of these dimensions, the significantly reduced tooth crown size is wholly attributed to the juveniles having smaller tooth crowns. Six dimensions of four teeth (maxillary second premolar and first molar, mandibular second premolar and first molar) were significantly smaller for teeth with and without enamel hypoplasia. These results indicate that increased frailty, which is reflected in a reduced tooth crown size, does affect mortality, more so for the juveniles than for adolescents. Besides a higher mortality risk, a higher risk of undergoing physiological stressors during early childhood, reflected in enamel hypoplasia presence, is also shown for individuals with reduced tooth crown sizes. Enamel hypoplasia lesions, thus, more likely reflect a weaker individual rather than a stronger individual. This study shows that selective mortality and hidden heterogeneity in frailty are issues that need to be considered in reconstructions of the health of past populations, however teeth are an excellent means to compare circumstances during the period of growth between survivors and non-survivors and to identify if these might account for the differences in longevity

Results from all test cases for rear quarter vehicle model.

<p>Results from all test cases for rear quarter vehicle model.</p