scholarly journals Method for determination of optimal geometrical parameters of a unit cell of X-shaped truss cores

2019 ◽  
Vol 18 (3) ◽  
pp. 99-108
Author(s):  
S. M. Mousavi Safavi
Keyword(s):  
Relative Density ◽  
Shear Stiffness ◽  
High Strength ◽  
Metal Plate ◽  
Unit Cell ◽  
Truss Structures ◽  
Core Material ◽  
Geometrical Parameters ◽  
Shear Stresses ◽  
Truss Core

Recently, in order to develop high-strength lightweight core materials of sandwich structures for multi-functional applications, a large number of truss structures have been created, including pyramidal and tetrahedral truss cores. In this paper, a new truss structure is developed to be used as core material in sandwich panels. The X-shaped truss core consists of discrete hourglass-shaped unit cells formed by the groove-to-groove connection of two flat X-shaped truss elements made by metal plate cutting. In order to determine optimal geometrical parameters of a unit cell of X-shaped truss core, in this work it is proposed to plot the diagrams of relative density versus the angle of the rods for the required values of equivalent critical compression and lateral shear stresses, and for the required values of equivalent compression and shear stiffness of the unit cell of X-shaped truss core. The results show that with the same mechanical characteristics, the relative density of the optimal X-shaped truss core is less than the relative density of optimal pyramidal and tetrahedral truss cores.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

Mechanical performance of honeycomb sandwich structures built by FDM printing technique

2021 ◽  
pp. 089270572199789
Author(s):  
S Gohar ◽  
G Hussain ◽  
A Ali ◽  
H Ahmad
Keyword(s):  
Fused Deposition Modeling ◽  
Mechanical Performance ◽  
Sandwich Structures ◽  
Weight Ratio ◽  
High Strength ◽  
Core Material ◽  
Interfacial Bond Strength ◽  
Fused Deposition ◽  
Competitive Prices ◽  
Composite Face

Honey Comb Sandwich Structures (HCSS) have numerous applications in aerospace, automobile, and satellite industry because of their properties like high strength to weight ratio, stiffness and impact strength. Fused Deposition Modeling (FDM) is a process which, through its flexibility, simple processing, short manufacturing time, competitive prices and freedom of design, has an ability to enhance the functionality of HCSS. This paper investigates the mechanical behavior (i.e. flexural, edgewise compression and Interfacial bond strength) of FDM-built HCSS. The influence of face/core material was examined by manufacturing four types of specimens namely ABS core with Composite (PLA + 15% carbon fibers) face sheets, ABS core with PLA face sheets, TPU core with composite face sheets and TPU core with PLA face sheets. To measure the effect of face sheets geometry, raster layup was varied at 0°/90° and 45°/−45°. The mechanical characterization revealed that an optimum combination of materials is ABS core with composite face sheets having raster layup of 0°/90°. This study indicates that HCSS with complex lamination schemes and adequate mechanical properties could be manufactured using FDM which may widen the applications of FDM on an industrial scale.

Stresses in Ultrasonically Assisted Turning

2006 ◽  
Vol 5-6 ◽  
pp. 351-358 ◽  
Author(s):  
N. Ahmed ◽  
A.V. Mitrofanov ◽  
Vladimir I. Babitsky ◽  
Vadim V. Silberschmidt
Keyword(s):  
Ultrasonic Vibration ◽  
Vibration Frequency ◽  
Cutting Forces ◽  
Plastic Material ◽  
Process Zone ◽  
Three Dimensional ◽  
Rate Sensitivity ◽  
High Strength ◽  
Material Model ◽  
Shear Stresses

Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.

scholarly journals Structural Transformations in Crystals Induced by Radiation and Pressure. Part 7. Molecular and Crystal Geometries as Factors Deciding about Photochemical Reactivity under Ambient and High Pressures

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 299 ◽  
Author(s):  
Krzysztof Konieczny ◽  
Arkadiusz Ciesielski ◽  
Julia Bąkowicz ◽  
Tomasz Galica ◽  
Ilona Turowska-Tyrk
Keyword(s):  
High Pressures ◽  
Unit Cell ◽  
Geometrical Parameters ◽  
Isopropyl Group ◽  
Unit Cell Parameters ◽  
Photochemical Reactivity ◽  
Space Group ◽  
Cell Parameters ◽  
Pressure Part ◽  
Asymmetric Unit Cell

We studied the photochemical reactivity of salts of 4-(2,4,6-triisopropylbenzoyl)benzoic acid with propane-1,2-diamine (1), methanamine (2), cyclohexanamine (3), and morpholine (4), for compounds (1), (3), and (4) at 0.1 MPa and for compounds (1) and (2) at 1.3 GPa and 1.0 GPa, respectively. The changes in the values of the unit cell parameters after UV irradiation and the values of the intramolecular geometrical parameters indicated the possibility of the occurrence of the Norrish–Yang reaction in the case of all the compounds. The analysis of the intramolecular geometry and free spaces revealed which o-isopropyl group takes part in the reaction. For (1), the same o-isopropyl group should be reactive at ambient and high pressures. In the case of (2), high pressure caused the phase transition from the space group I2/a with one molecule in the asymmetric unit cell to the space group P1¯ with two asymmetric molecules. The analysis of voids indicated that the Norrish–Yang reaction is less probable for one of the two molecules. For the other molecule, the intramolecular geometrical parameters showed that except for the Norrish–Yang reaction, the concurrent reaction leading to the formation of a five-membered ring can also proceed. In (3), both o-isopropyl groups are able to react; however, the bigger volume of a void near 2-isopropyl may be the factor determining the reactivity. For (4), only one o-isopropyl should be reactive.

scholarly journals Optimization of Geometrical Parameters of Hollow-core Slabs by Formwork-free Shaping for Construction in Seismic Areas

2020 ◽  
Vol 8 (6) ◽  
pp. 4973-4977
Keyword(s):  
Cross Section ◽  
High Strength ◽  
Geometrical Parameters ◽  
Hollow Core ◽  
Constructive Solution ◽  
Industrial Buildings ◽  
Operational Load ◽  
Wide Range ◽  
Hollow Core Slab ◽  
The Cross

The building norms and standards of Uzbekistan on the reinforced concrete structures do not regulate the design of hollow-core slabs of formwork-free shaping, reinforced with prestressed wire reinforcement. The manufacturing technology of such slabs allows creating a wide range of products that increase the possibility of their use in various structural systems in residential, civil and industrial buildings, but in non-seismic areas only. The aim of this work is to develop a constructive solution for the cross section of a prestressed hollow-core floor slab of bench formwork-free shaping, reinforced with high-strength wire reinforcement, in order to create a wide range of products intended for construction in seismic areas. To achieve the goal, the problem of determining the optimal combination of height and configuration parameters of the cross section of such a slab is solved, meeting the normalized operational requirements and limitations of earthquake-resistant building standards. The main variable parameters are the height and the void degree of the section, characterized by the size and shape of voids. In calculating the cross-section of a hollow-core slab when substantiating the theoretical basis for the calculation, the cross section is reduced to the equivalent I-section. As a result of research, a constructive solution was developed for the slab cross section of the maximum parameter values (the span, operational load) set by the customer. The parameters of the slab cross-section are: the height 190 mm, the hollowness 38%, the height of the upper thickened flange (compared with the height of the lower flange) of the given section is 0.27h, the height of the lower flange is 0.17h, the reduced (total) thickness of all ribs “b” is 0.32 of the width of the upper flange. The voids in the section along the height of the slab are arranged asymmetrically. A patent for a utility model has been received for the proposed constructive solution of the slab cross section.

Sound insulation performance of pyramidal truss core sandwich structure with frame

2021 ◽  
pp. 109963622110288
Author(s):  
Yu-Zhou Wang ◽  
Li Ma
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structure ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Insulation ◽  
Geometrical Parameters ◽  
Acoustic Performance ◽  
Truss Core ◽  
Pyramidal Truss ◽  
Wave Angle

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed.

scholarly journals High-Strength Behavior of the Al0.3CoCrFeNi High-Entropy Alloy Single Crystals

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1149
Author(s):  
Irina V. Kireeva ◽  
Yuriy I. Chumlyakov ◽  
Zinaida V. Pobedennaya ◽  
Anna V. Vyrodova ◽  
Anastasia A. Saraeva
Keyword(s):  
Single Crystals ◽  
Yield Point ◽  
Stress Level ◽  
High Stress ◽  
High Strength ◽  
Orientation Dependence ◽  
Temperature Deformation ◽  
High Entropy Alloy ◽  
Shear Stresses ◽  
High Entropy

The main disadvantage of fcc (face-centred cubic lattice) high-entropy alloys is the low stress level at the yield point (σ0.1) at a test temperature above room temperature. This restricts their practical application at high test temperatures from 773 K to 973 K. In this study, we found that a high stress level was reached at the yield point σ0.1 ≈ G/100–G/160 (G is the shear modulus) of the [001]- and [1¯44]-oriented crystals of the Co23.36Cr23.29Fe23.80Ni21.88Al7.67 (Al0.3CoCrFeNi) high-entropy alloy (HEA) within a wide temperature range of 77–973 K under tension, due to the occurrence, of nanotwins, multipoles, dislocations under plastic deformation at 77 K and the subsequent precipitation of ordered L12 and B2 particles. It was shown that grain boundaries are not formed and the samples remain in a single-crystal state after low-temperature deformation and subsequent ageing at 893 K for 50 h. Achieving a high-strength state in the Al0.3CoCrFeNi HEA single crystals induces the orientation dependence of the critical resolved shear stresses (τcr) at T ≥ 200 K (τcr[1¯44] > τcr[001]), which is absent in the initial single-phase crystals, weakens the temperature dependence of σ0.1 above 573 K, and reduces plasticity to 5–13% in the [1¯44] orientation and 15–20% in the [001] orientation.

Forming Potential of Steel/Polymer/Steel Sandwich Composites with Local Plate Inserts

2012 ◽  
Vol 706-709 ◽  
pp. 681-686 ◽  
Author(s):  
Heinz Palkowski ◽  
Olga Sokolova ◽  
Adele Carradò
Keyword(s):  
Deep Drawing ◽  
High Performance ◽  
High Strength ◽  
Metal Plate ◽  
Elastic Behaviour ◽  
Forming Limit ◽  
Sandwich Composites ◽  
Strength And Stiffness ◽  
Naval Engineering ◽  
Forming Behaviour

High-performance metal/polymer/metal hybrid sandwich composites are attractive materials for lightweight constructions in automotive, aerospace and naval engineering world-wide. Due to the excellent combination of mechanical, thermal and elastic properties and, as a result of high forming potential, they can be used in areas of high vibration, where high damping properties of the polymer are demanded and at the same time high strength and stiffness are given by the metal. Disadvantages can be given in case of mechanical or thermal joining of these polymer-based sandwiches because of the elastic behaviour as well as low melting temperature of the polymer. Local metal plate insertions in the soft core at the place of joining can be a solution for such kind of problems. But forming behaviour of sandwich materials with and without local inlays differs strongly. Sandwich composites of that type were produced by roll-bonding. Their quality and their position were controlled by Lockin thermography. The forming behaviour of sandwiches with different geometry, size, type and the position of the inlays was tested by deep drawing and bending and analysed with the help of digital photogrammetry and compared to experimentally obtained mechanical properties. As a result, the local inlays, as well as their geometry, size and type strongly influence the forming limit conditions. The differences in flow behaviour of non-reinforced and reinforced sandwich regions after deep drawing and bending will be presented, as well as the influence of the position of the inlays.

Multiscale Design and Multiobjective Optimization of Orthopaedic Cellular Hip Implants

2011 ◽  
Author(s):  
Sajad Arabnejad Khanoki ◽  
Damiano Pasini
Keyword(s):  
Finite Element ◽  
Bone Resorption ◽  
Multiobjective Optimization ◽  
Relative Density ◽  
Homogeneous Medium ◽  
Unit Cell ◽  
Interface Stress ◽  
Optimization Strategy ◽  
Interface Failure ◽  
Nsga Ii

A multiscale design and multiobjective optimization procedure is developed to design a new type of graded cellular hip implant. We assume that the prosthesis design domain is occupied by a unit cell representing the building block of the implant. An optimization strategy seeks the best geometric parameters of the unit cell to minimize bone resorption and interface failure, two conflicting objective functions. Using the asymptotic homogenization method, the microstructure of the implant is replaced by a homogeneous medium with an effective constitutive tensor. This tensor is used to construct the stiffness matrix for the finite element modeling (FEM) solver that calculates the value of each objective function at each iteration. As an example, a 2D finite element model of a left implanted femur is developed. The relative density of the lattice material is the variable of the multiobjective optimization, which is solved through the non-dominated sorting genetic algorithm II (NSGA-II). The set of optimum relative density distributions is determined to minimize concurrently interface stress distribution and bone loss mass. The results show that the amount of bone resorption and the maximum value of interface stress can be reduced by over 70% and 50%, respectively, when compared to current fully dense titanium stem.

scholarly journals The effect of mean axial and torsional stresses on the fatigue strength of 34CrNiMo6 high strength steel

2019 ◽  
Vol 300 ◽  
pp. 16004
Author(s):  
Luis Pallarés-Santasmartas ◽  
Joseba Albizuri ◽  
Nelson Leguinagoicoa ◽  
Nicolas Saintier ◽  
Jonathan Merzeau
Keyword(s):  
High Strength Steel ◽  
Fatigue Behavior ◽  
High Strength ◽  
Fatigue Loading ◽  
Experimental Results ◽  
Shear Stresses ◽  
Mean Stress ◽  
Theoretical Predictions ◽  
Loading Case ◽  
Fracture Appearance

The present study consists of a theoretical, experimental and fractographic investigation of the effect of superimposed static axial and shear stresses on the high cycle fatigue behavior of a 34CrNiMo6 high strength steel in quenched and tempered condition (UTS = 1210 MPa), commonly employed in highly stressed mechanical components. The Haigh diagrams for the axial and torsional cases under different values of mean stress were obtained. In both cases, experimental results showed that increasing the mean stress gradually reduces the stress amplitude that the material can withstand without failure. The results of the present tests are compared with the theoretical predictions from Findley, based on the maximum damage critical plane; and the methods of Marin and Froustey, which are energetic based criterions. Froustey’s method shows the best agreement with experimental results for torsional fatigue with mean shear stresses, showing a non-conservative behaviour for the axial fatigue loading case. Macro-analyses and micro-analyses of specimen fracture appearance were conducted in order to obtain the fracture characteristics for different mean shear stress values under torsion fatigue loading.

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