Geometry optimization of double wishbone suspension system via genetic algorithm for handling improvement

Motion control, stability maintenance and ride comfort improvement are fundamental issues in design of suspension systems in off-road vehicles. In this paper, a double wishbone (DW) suspension system, mostly used in off-road vehicles, is modeled using ADAMS software. Geometric parameters of suspension system are optimized using genetic algorithm (GA) in a way that ride comfort, handling and stability of vehicle are improved. Simulation results of suspension system and variations of geometric parameters due to road roughness and different steering angles are presented in ADAMS and effects of optimization of suspension system during various driving maneuvers in both optimized and non-optimized conditions are compared. Simulation results indicate that the type of suspension system and geometric parameters have significant effect on vehicle performance

THE INFLUENCE OF GEOMETRIC PARAMETERS AND MECHANICAL PROPERTIES OF ADHESIVE ON STRESS ANALYSIS IN ADHESIVELY BONDED ALUMINUM SINGLE LAP JOINT

The aim of this study was to investigate adhesively bonded joints, and the influence of geometric parameters and mechanical properties of the adhesive in single lap aluminum structures under tensile load. A finite element model has been constructed in the ANSYS FE package and the effects of adhesive thickness, rigidity, strength and geometry have been studied in order to adjust peel stress. Various paths have been defined and obtained along the length of the adhesive and aluminum joint overlap. The results indicate that by increasing the adhesive thickness, the stress concentration decreases in the areas prone to yielding if a flexible adhesive is used instead of a rigid one, and effective stresses along the overlap length are also reduced. In addition, for a given tensile force, three different adhesive area geometries are defined. Considering the variation of peel and shear stress along the corners, the amount of adhesive used according to the introduced geometries is saved without sacrificing joint strength

Stress and dynamic analysis of optimized trailer chassis

Članak se bavi dinamičkom i analizom naprezanja lančane sheme šasije kamiona. Najprije se, kako bi se konstruirala šasija najmanje težine, odabiru vrsta materijala i profili poprečnog presjeka šasije u skladu s maksimalnim normalnim naprezanjem i teorijama maksimalne deformacije. Zatim je provedena analiza naprezanja šasije kamiona primjenom ABAQUS softvera u svrhu određivanja maksimalnog poprečnog progiba i raspodjele naprezanja. Rezultati pokazuju da su U-profili dovoljni za smanjenje težine koja može izdržati opterećenja. U sljedećem su koraku razmatrana vibracijska svojstva šasije, što je od velike važnosti za određivanje prirodnih frekvencija konstrukcije. U tu se svrhu provela modalna analiza metodom konačnih elemenata pomoću ANSYS softvera te su određene prirodne frekvencije i oblici vibriranja. U završnom se stupnju dinamički model vozila iskoristio za usporedbu dinamičkih parametara vozila i voznih karakteristika kod optimalizirane i neoptimalizirane šasije. Rezultati simulacije su pokazali da optimalizirana šasija povećava stabilnost kod ljuljanja i poboljšava uvjete u vožnji. Također, da bi se izbjeglo poklapanje frekvencije pobude (ekscitacije) s prirodnom frekvencijom šasije, prirodne frekvencije i oblici vibriranja analizirali su se uz promjene uvjeta opterećenja.This paper discusses the stress and dynamic analysis of truck ladder chassis. At the first stage, in order to design a chassis for self-weight reduction, material type and cross section profiles of chassis are selected according to a maximum normal stress and maximum strain theories. Then, the stress analysis of truck chassis has been carried out by ABAQUS software to determine maximum transverse deflection and stress distribution. Results show that open U-shaped profiles are sufficient for weight reduction which can endure loads. In the next stage, the prediction of the vibrational properties of the chassis which is of great significance in determining the natural frequencies of the structure, are considered. For this purpose, the modal analysis has been accomplished by the finite element packaged ANSYS software, and natural frequencies and mode shapes have been determined. In the final stage, vehicle dynamic model is used to compare vehicle dynamic parameters and ride response in optimized and not optimized chassis conditions. Simulation results clarified that the optimized chassis increases the roll stability and improves ride conditions. Also, in order to avoid matching the natural frequency of the chassis with the excitation frequency, natural frequencies and vibration modes have been analysed during the loading conditions

Analytical framework for analyzing brake squeal noise using assumed-modes approach

Sometimes a loud noise or high pitched squeal occurs when the brakes are applied. It is generated during the braking phase and is characterized by a harmonic spectrum. Brake squeal is induced by self-excited vibrations, consequences of local nonlinearities at the contact interface. Many researchers have examined the problem with experimental, analytical, and computational techniques, but there is still no method to fully annihilate brake squeal. This paper deals with presentation of a new model to analyze the brake squeal behavior. In this paper, a lumped-continuous vibration model is presented for the braking system and nonlinear equations are obtained using the Hamilton’s principle. Then, the linearization of nonlinear equations is done around the equilibrium point of system and linear stability analysis is discussed. Furthermore, the effects of different braking parameters such as friction coefficient, rotational speed, pad stiffness, calipers etc. on the brake squeal noise are investigated

Analytical framework for analyzing brake squeal noise using assumed-modes approach

Sometimes a loud noise or high pitched squeal occurs when the brakes are applied. It is generated during the braking phase and is characterized by a harmonic spectrum. Brake squeal is induced by self-excited vibrations, consequences of local nonlinearities at the contact interface. Many researchers have examined the problem with experimental, analytical, and computational techniques, but there is still no method to fully annihilate brake squeal. This paper deals with presentation of a new model to analyze the brake squeal behavior. In this paper, a lumped-continuous vibration model is presented for the braking system and nonlinear equations are obtained using the Hamilton’s principle. Then, the linearization of nonlinear equations is done around the equilibrium point of system and linear stability analysis is discussed. Furthermore, the effects of different braking parameters such as friction coefficient, rotational speed, pad stiffness, calipers etc. on the brake squeal noise are investigated

Reliability techniques to reduce the risk of failure in cng composite pressure vessel

This paper is devoted to present reliability techniques as a best failure mitigation tool for CNG composite pressure vessels. As far as composite materials are so sensitive to environmental working conditions, design methodology must be established based on reliability considerations. Because of over using of car fuel tanks, CNG should be properly substituted as an alternative fuel. Safety and cost are the most critical points in developing CNG-CPV to public usage. Meeting optimum point, design criteria must be followed by reliability criteria. In this paper, author tried to persuade CNG-CPV developer to take  care of mentioned risks. Reliability testing is introduced as a feasible and reliable solution in order to assure desired safety

A Comparison between cutting and folding modes of an extruded aluminum alloy tube during impact using ductile failure criterion

Thin-walled structures like crash boxes may be used as energy absorbers in the automotive chassis. There have been lots of investigations about the behavior of these parts during frontal crashes. Previous researches show that thin-walled circular tube has the highest energy absorption among different structures. In this study, cutting and folding modes of extruded aluminum tubes (EN-7018 T6) with 50 mm diameter, lengths of 300 and 400 mm and thicknesses of 2, 2.5 and 3 mm are compared when axial impacts with velocities of 6, 8 and 10 m.s-1 are applied to them. Cutting tools of 4 and 6 blades are used to provide the cutting mode. Effective parameters of energy absorbers including crush force efficiency, specific energy absorption and maximum axial load are modeled numerically with the help of Hooputra’s ductile damage criterion and are compared to each other for three cases of aluminum tube folding between two rigid plates and tube rupture by using 4 and 6 blades cutting tools. The analyses show that the tube rupture by the 6 blades cutting tool is better than the other two in the case of energy absorption. Furthermore, the results demonstrate that tube cutting with the help of multi-blades cutting tools is more stable, controllable and predictable than tube folding

Aberrant expression of miR-141 and nuclear receptor small heterodimer partner in clinical samples of prostate cancer.

BACKGROUND: Prostate cancer (PCa) is the second most common cancer in men worldwide. Currently, prostate-specific antigen (PSA) test and digital rectal exam are the main screening tests used for PCa diagnosis. However, due to the low specificity of these tests, new alternative biomarkers such as deregulated RNAs and microRNAs have been implemented. OBJECTIVES: Aberrant expression of small heterodimer partner gene (SHP, NR0B2) and mir-141 are reported in various cancers. The aim of this study was to investigate the SHP and miR-141 expression level in tissue samples of prostate cancer. METHODS: The expression level of SHP gene and miR-141 was assessed by real time PCR and their relative amounts were calculated by the Δ⁢ΔCT method. Also, IHC technique was used to determine the expression level of SHP protein. RESULTS: The miR-141 was significantly up-regulated in the samples of metastatic tumors compared to localized tumor samples (P< 0.001, 31.17-fold change). Tumor samples showed lower SHP mRNA expression level than BPH samples (p= 0.014, 4.7-fold change). The results of paired t-test analysis showed there was no significant difference between the SHP gene expression in PCa samples and their matched tumor-adjacent normal tissue (p= 0.5). CONCLUSIONS: The data obtained in our study confirm the involvement of miR-141 in PCa progression and metastasis. These effects could be mediated by AR via down-regulation of its co-repressor protein, i.e., SHP. KEYWORDS: Immunohistochemistry; Prostate cancer; SHP gene; biomarker; gene expression; miR-141; nuclear receptor

The Iranian blood pressure measurement campaign, 2019: study protocol and preliminary results

Purpose Hypertension is one of the most important risk factors for premature mortality and morbidity in Iran. The objective of the Iranian blood pressure (BP) measurement campaign was to identify individuals with raised blood pressure and providing appropriate care and increase the awareness among the public and policymakers of the importance of tackling hypertension. Methods The campaign was conducted in two phases. The first (communication) phase started on May 17th (International Hypertension Day). The second phase started on June 8th, 2019, and lasted up to July 7th during which, blood pressures were measured. The target population was Iranians aged >= 30 years. Participants voluntarily referred to health houses in rural and health posts and comprehensive health centers in urban areas in the setting of the Primary Health Care network. Additionally, over 13,700 temporary stations were set up in highly visited places in urban areas. Volunteer healthcare staff interviewed the participants, measured their BP, and provided them with lifestyle advice and knowledge of the risks and consequences of high blood pressure. They referred participants to physicians in case their BP was high. Participants immediately received a text message containing the relevant advice based on their measured BP and their past history. Results Blood pressure was measured for a total of 26,678,394 participants in the campaign. A total of 13,722,148 participants (51.4%) were female. The mean age was 46 +/- 14.1 years. Among total participants, 15,012,693 adults (56.3%) with no past history of hypertension had normal BP, 7,959,288 participants had BP in the prehypertension range (29.8%), and finally, 3,706,413 participants (13.9%) had either past medical history of hypertension, used medications, or had high BP measured in the campaign. Conclusion The campaign was feasible with the objective to increase the awareness among the public and policymakers of the importance of tackling hypertension in Iran