•A novel bistable mechanism utilizing torsion stiffness enhanced flexible beams to restrain the shuttle from out-of-plane rotation.•An analytical kinetostatic model is developed for the proposed ...bistable mechanism.•Five bistable examples are presented to demonstrate the effectiveness of the proposed bistable mechanism in suppressing unwanted motions, especially when the shuttle is displaced to a position around the second equilibrium stable position.
For compliant bistable mechanisms with planar configurations and exhibiting two in-plane stable states, their flexible beams are supposed to undergo in-plane bending deflections, but the out-of-plane deflections can significantly influence the kinetostatics of the mechanism, resulting in inconsistent bistable behaviors when off-axis or eccentric loads present. In this paper, we propose a novel bistable mechanism utilizing torsion-stiffness enhanced flexible beams to restrain the shuttle from out-of-plane rotation. An analytical kinetostatic model is developed for the proposed bistable mechanism. Five bistable examples are presented to demonstrate the effectiveness of the proposed bistable mechanism in suppressing unwanted motions and the correctness of the proposed kinetostatic model. The results show that the novel bistable designs are much stiffer along the out-of-plane rotation thus are more robust against off-axis or eccentric loading condition, especially when the shuttle is displaced to a position around the second equilibrium stable position (where the flexible beams are in the post-buckling states).
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•Proposed free-form optimization for designing bending and torsional stiffness of tubular structures with auxetic patterns.•Demonstrated the ability to adjust bending and torsional ...rigidities via multi-objective Bayesian optimization (MBO).•Maintained excellent predictive performance with only 300 data points and fewer iterations than big data-based ML approach.•Validated the bending and torsional stiffness of the optimal design by measuring the natural frequencies.
Medical concentric tubes have recently been designed using auxetic structures with negative Poisson's ratios to reduce undesirable snapping instability and improve mechanical performance. Despite the vast range of stiffness levels, prior auxetic designs were restricted to relatively simple geometries like square or triangular holes. Here, we present a novel free-form optimization for designing the bending and torsional stiffness of tubular structures using the multi-objective Bayesian optimization (MBO) method. The initial dataset of hole shapes is generated using a non-parametric Bézier curve, and the corresponding mechanical properties are estimated via numerical analysis. The acquisition function suggests a new hole shape with higher performance metrics based on the dataset, and updates to the regression model are made with new data points to improve prediction accuracy. Compared to a conventional tube with rectangular holes, the optimized design improves key factor, a ratio of bending stiffness to torsional rigidity, and torsional stiffness by 32% and 25%, respectively, by expanding the existing design space. The performance of the optimally designed tube was validated by resonant vibration tests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Initial torsion stiffness increases with increasing concrete strength and decreases with increasing shear-span ratio.•Ductility was reduced torsion-bending ratio increased and the energy dissipation ...capacity decreased.•Influence order of parameters on the ultimate torsion is: concrete strength, shear/span, steel ratio, torsion/bending, stirrup ratio, longitudinal reinforcement ratio and axial load ratio.•Influence order of parameters on the ductility coefficient is: steel ratio, shear/span, concrete strength, axial load ratio, stirrup ratio, torsion-bending ratio and longitudinal reinforcement ratio.
A computational model for studying the mechanical performance of steel-concrete columns under combined torsion is established via ABAQUS. The model is validated by experimental results. Through numerical simulations, the influence of the axial load ratio, torsion-bending ratio, concrete strength, steel ratio, longitudinal reinforcement ratio, stirrup ratio, and shear-span ratio on the torsional behaviour of steel-concrete columns is comprehensively investigated. The initial torsion stiffness and ultimate torsion strength of the column increase with increasing concrete strength and decreasing shear-span ratio. The parameters in descending order of influence on the ultimate torsion strength are steel ratio, torsion-bending ratio, stirrup ratio, longitudinal reinforcement ratio, and axial load ratio. Furthermore, the seven parameters in descending order of influence on the ductility coefficient are the steel ratio, shear-span ratio, concrete strength, axial load ratio, stirrup ratio, torsion-bending ratio and longitudinal reinforcement ratio.
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Torsion stiffness of elastic suspensions made of anisotropic single crystal silicon cannot be calculated by formulas derived for isotropic materials. We introduce a simple expression for an effective ...shear modulus, which depends on the aspect ratio (AR) of the torsional bar cross section. The approximation allows torsion stiffness evaluation of prismatic bars oriented in the most common 1 1 0 and 1 0 0 crystal directions, and can be directly used in an isotropic formula and is applicable within an entire range of the bar cross section AR. Our numerical and experimental results show that the approach can be conveniently used as a design tool for tilting micro devices.
The effects of structural parameters, material parameters and pre-compression of rubber on the static torsion stiffness of rubber spring were studied by means of experimental research and simulated ...analysis. Firstly, the Mooney-Rivlin model was used to fit the rubber constitutive parameters, and the finite element model of rubber spring was established. Then, the quasi-static torsion experiment of the rubber spring was carried out, which verified the accuracy of the finite element model. Finally, based on the established finite element model, the effects of rubber rod height, diameter, pre-compression and hardness on the static torsion stiffness of rubber spring were studied by orthogonal experimental method. The results show that the height, diameter, pre-compression and hardness of rubber rod are nonlinear with the static torsion stiffness of rubber spring, and the pre-compression of rubber rod has the most significant effect on the static torsion stiffness of rubber spring.
The overrunning clutch, or freewheel, is a kind of universal part with a one-way drive character, and is widely used in machinery. Typical roller overrunning clutches and sprag overrunning clutches ...have shortcomings such as low load bearing capacity, low torsional stiffness, and short life. For these reasons, studies on high-performance overrunning clutches have always been the focus of researchers. In this paper, a new type of double arc sprag overrunning clutch is proposed that overcomes the disadvantages of poor transmission capacity and low rigidity found in traditional overrunning clutches. The mechanical model of the double arc sprag overrunning clutch is established, the calculation formulas of the overrunning clutch engagement conditions and overrunning conditions are deduced, and the forces of the outer ring, roller, and inner star wheel of the overrunning clutch are also deduced. The contact stress and transmission torque of the overrunning clutch are compared with those of the roller overrunning clutch and the sprag overrunning clutch. The results show that the proposed overrunning clutch has the largest load capacity, which is 5.75 times that of the roller type overrunning clutch, and 2.1 times that of the sprag type overrunning clutch. The experiment shows that the proposed overrunning clutch has reliable bonding conditions in the oil-free and oil-immersed state, and the overrunning condition is sensitive, which indicates the effectiveness of the double arc sprag overrunning clutch. The roller overrunning clutch and double arc sprag overrunning clutch with the same geometric parameters are designed and manufactured, and the torsional stiffness test of the three types of overrunning clutches is carried out. The results show that the torsional stiffness of the double arc sprag overrunning clutch is the largest, which is 4.6 times of the roller overrunning clutch and 6.2 times of the sprag overrunning clutch.
Abstract
First create a simple beam model of finite element simulation analysis, find the principle and method of equivalent ACM solder joints, then the equivalent method of ACM welds a car white ...body finite element model is established, by using NASTRAN analysis modal, torsional rigidity and bending rigidity, and compared with the experiment on the mark, has the very good correlation. The results show that based on the 5mm×5mm mesh size, the equivalent ACM solder joint model is reasonable and reliable for the modal and static stiffness modeling analysis of BIW.
A non-classical mechanical analysis method was used to derive the equivalent torsional stiffness of thick-walled CFRP drive shaft. The equivalent shear modulus calculated by classical lamination ...theory, finite element analysis method and non-classical mechanical analysis method were compared. Experimental work was carried out on six composite tubes made of same dimensions but different lay-ups. All the results show that the layers with ±45° fiber orientation angle located on the outside of the wall thickness can increase the torsion stiffness of the composite tube. The non-classical mechanical analysis method predicts the torsion stiffness of thick-walled composite tube more precisely than the theory classical lamination, and agree well with experimental results. This method provides a convenient, accurate and fast method for the torsion stiffness.
Vehicle mass reduction is a major area of research in the automobile industry. Various techniques like reduced part break up, section reduction, material alternatives and load path design are widely ...being researched across the world. This paper presents a new technique of identifying materials for the components of minimal part break-up Body-In-White (BIW) in the conceptual phase using design of experiments and multi-objective optimization. Prime focus was on the methodology to effectively consider the materials for the parts without compromising the structural performance of the target components. BIW structural load cases like bending and torsion stiffness were considered to evaluate the structural performance. Material list is used as the design variable and then sampled using design of experiments to undertake multi-objective optimization. As a result, optimal material distribution and mass savings have been achieved for the BIW parts. The optimized design performance is closer to the baseline design. The proposed methodology may be widely adopted by engineers to optimally distribute the materials for the BIW components at various stages of the vehicle design.
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