Torsion Specimens Research Articles

Prediction of Damage Behavior of Casting Aluminum Components Considering Inhomogeneous Properties

The purpose of the work is to quantify and predict the influence of inhomogeneity of local properties on the overall behavior of the selected casting aluminum wheel and knuckle in different loading cases. Smooth and notched tensile specimens and torsion specimens are extracted from different positions in the wheel and knuckle and tested. The dependences of the flow stress, the fracture strain, and the S-N curve on position for specimen extraction are evaluated. Metallographic investigations are performed to reveal the relations between microstructure/microdefects and the mentioned properties. A damage model based on a triaxiality-dependent fracture strain is calibrated and used to simulate the specimens and component tests. The simulations of static wheel tests and knuckle fatigue tests are performed with position-dependent material parameters. The prediction of the component tests is compared with the experimental results.

Mechanical properties of concrete filled steel tube members constrained by carbon fiber reinforced materials under bidirectional coupled loading

Carbon fiber reinforced composite structures have been a research hotspot in recent years, with 9 specimens designed for static tests under bending and torsion loads of CFRP concrete filled steel tubes. The torque angle (T-θ) curve was studied from an experimental perspective. Subsequently, a reasonable finite element model was established using ABAQUS software. In addition, the effects of changes in parameters such as the number of steel concrete strength, bending ratio, and steel ratio on C–CF–CFRP-ST bending and torsion specimens were studied through numerical parameter research. Finally, equations of bearing capacity of CFRP-concrete filled steel tube under coupled bending and torsion are proposed.

A predictive mesoscale model for continuous dynamic recrystallization

Thermomechanical processing of titanium alloys often requires complex routes to achieve the desired final microstructure. Recent advances in modeling and simulation tools have facilitated the optimization of these processing routes. However, existing models often fail to accurately predict microstructural changes at large deformations. In this study, we refine the physical principles of an existing mean-field model and propose a calibration method that uses experimental results under isothermal conditions, accounting for the actual local deformation within the workpiece. This new approach improves the predictability of microstructural changes due to continuous dynamic recrystallization during torsion and compression experiments. Additionally, we integrate the model into the commercial FEM-based DEFORM™ 2D software to predict the local microstructure evolution within hot torsion specimens thermomechanically treated by resistive heating. Validation using non-isothermal deformation tests demonstrates that the model provides realistic simulations at high strain rates, where adiabatic heat modifies temperature, flow stress and microstructure. This study demonstrates the intrinsic correlation between microstructure, flow behavior, and workpiece geometry, considering the impact of deformation history in thermomechanical processes.

A new method for ultrasonic fatigue component frequency modulation: From ultrasonic horn to uniaxial and multiaxial specimens

Ultrasonic fatigue specimens require rigorous design. The entire machine and specimen setup must vibrate in resonance at high frequencies, with the desired mode shapes that produce the intended stresses. The connection between parts must be considered too as they should allow for the desired mode shape to vibrate in free-free conditions. Most published research uses an analytical method that works only for uniaxial tension–compression or pure torsion specimens. This limits the range of experiments. In this paper, a semi-analytical formulation that can model more complex ultrasonic specimen geometries for a variety of stress states is proposed, namely multiaxial tension–torsion. Comparing numerical simulations with the analytical method show a good correlation between results. This work can help other researchers to design and conduct more varied and efficient ultrasonic fatigue experiments.

Influence of Pre-Tension on Free-End Torsion Behavior and Mechanical Properties of an Extruded Magnesium Alloy.

In this study, the influence of pre-tension on free-end torsion behavior and compression mechanical properties and micro-hardness of an extruded AZ31 Mg alloy was investigated using electron backscatter diffraction (EBSD), compression testing and micro-hardness testing. The result indicates that pre-tension can cause significant dislocation strengthening, which can increase the torsion yield strength and make the shear stress-shear strain curve of the pre-tension sample almost parallel to that of the as-extruded sample during plastic deformation stage. Texture in edge position on the cross-section of both the pre-tension and as-extruded samples can be rotated towards the extrusion direction by about ~30° by free-end torsion. The Swift effect is mainly responsible for the occurrence of massive extension twins in the central region. In contrast, normal stress is the main cause of extension twins occurring in the edge region. However, the effect of extension twins on micro-hardness is less than that of dislocations. The micro-hardness of both free-end torsion specimens increases almost linearly with increasing distance from center to edge on the cross-section. Nevertheless, the increase in micro-hardness of the pre-tension and then torsion sample is inconspicuous because pre-tension leads to dislocation proliferation and dislocation accumulation saturation. The result also indicates that both pre-tension and free-end torsion can lead to dislocation strengthening, which can obviously increase the micro-hardness and compressive yield stress. The underlying mechanisms were explored and discussed in detail.

Static Behavior of Circular Section CFRP Concrete-Filled Steel Tubes Under Compressive–Torsional Load

In order to study the compressive torsional behavior of concrete-filled CFRP steel tubes (CF-CFRP-STs), the static test of eight circular section CF-CFRP-ST compression torsional specimens was carried out. The characteristics of the torque–angle (T–θ) curve and shear stress shear–strain (τ–γ) curve, failure mode, cooperative work between steel tubes and CFRP, and cross-section assumption were studied. The T–θ curve, τ–γ curve, and failure mode of the specimen are simulated by ABAQUS. Based on the above research, the stress distribution of each component material is analyzed. The effects of transverse CFRP layers, material strength, steel ratio, and axial compression ratio on the static performance of members are discussed. Based on the performance analysis, the bearing capacity equation of CF-CFRP-ST compression-torsional members is proposed.

High strain rate torsional response of maraging steel parts produced by laser powder bed fusion techniques: Deformation behavior and constitutive model

The deformation performance of maraging steel samples fabricated using the laser powder bed fusion technique was evaluated using the split Hopkinson torsion bar (SHTB) test. Thin-walled tubular maraging steel samples were deformed under dynamic torsional loading at strain rates of 260 s−1 to 720 s−1 using twist angles varying from 3 to 12°. Microstructural and textural investigations were carried out on deformed samples using the electron backscatter diffraction technique and scanning electron microscopy. Results showed that maraging steel samples fractured when deformed using an angle of twist of 12° and strain rate of 650 s−1. As a result of deformation localization at high strain rates, adiabatic shear bands are developed in some thin-walled tubular torsion specimens deformed using the 12-degree angle of twist, leading to fracture. Textural studies showed that texture weakening occurred with an increment in strain rate ascribable to grain fragmentation. In this study, two models (empirically and semi-empirically) were employed for describing maraging steel performance during high strain-rate torsional loading. Simulation results based on Kobayashi-Odd and Nemat-Nasser models agreed well with the experimental data.

On the torsional and coupled torsion-tension/compression behavior of magnesium alloy solid rod: A crystal plasticity evaluation

Extensive attention has been paid to magnesium (Mg) alloys considering their potential as lightweight structural materials. However, it is still challenging to process and manufacture Mg materials that carry high strength and good ductility. This issue mainly arises from a lack of understanding toward the anisotropic mechanical behavior of Mg alloys in response to large deformation in a multiaxial stress state, which is unavoidably in existence under various material processing routes. In this regard, we seek to understand the torsional and coupled torsion-tension/compression behaviors of a magnesium alloy subject to large-strain deformation. The elastic viscoplastic self-consistent (EVPSC) model, which incorporates the twinning-detwinning (TDT) scheme and takes a torsion-specific finite element (TFE) approach, was employed to illuminate the inhomogeneous and multiaxial features of the torsional deformation in the AZ31 Mg alloy subjected to free/fixed-end torsion and coupled torsion-tension/compression. Experimental validation was conducted by characterizing the mechanical responses of the torsional specimens under the loading paths of free-end torsion and coupled torsion-tension. Our model successfully captures the Swift effect along with the shear texture, which is hardly predicted by conventional constitutive models. In addition, our model reveals that twinning is nearly equally active under free-/fixed-end torsion, while twinning under coupled torsion-tension and torsion-compression is promoted and suppressed, respectively. The comparison between the simple shear and pure torsion by simulation demonstrates that the significant bulk stress existing within the torsional rod is ascribed to the strong interaction between the cylindrical elements in the EVPSC model. As a final thought, we believe that the TFE-EVPSC-TDT model not only highlights the inhomogeneous and multiaxial features underlying the torsional and coupled torsion-tension/compression behaviors of the Mg alloy solid rod, but more significantly, can be used as a numerical tool for designing/tuning gradient twinning structures that may lead to optimized properties of Mg alloys.

Determination of Single Parameter for Serviceability Requirements of Fibre Reinforced Concrete: Study of Fracture Characteristics

Abstract: This The influence of fibre reinforcement on crack propagation in concrete was studied . Thirty-five double torsion specimens, made with three types of fibres (fibre glass , straight steel fibres and deformed steel fibres ) were tested . The variables were the fibre volume and size of the fibres. The test results indicated that the resistance to rapid crack growth increased somewhat with increasing fibre content up to about 1.25% - 1.5% by volume. The degree of compaction had an enormous effect on the fracture properties .The fracture toughness increased with fibre content up to about 1.25% by volume, and then decreased , due to incomplete compaction. It was found that in this test geometry, fibres did not significantly restrain crack growth. It was also observed that once the crack had propagated down the full length of the specimen, the system changed from a continuous system to a discontinuous system, consisting of two separate plates held together by the fibre reinforcement. Different types of fibres did not significantly affect the fracture toughness. Keywords: Fibre glass, straight steel fibers, deformed steel fibers, fracture toughness.

Photogrammetric evaluation of shear modulus of glulam timber using torsion test method and dual stereo vision system

The shear modulus of timber and timber-based composite materials is a fundamental mechanical property, which is used in the design of timber and engineered wood products. The problem of experimentally determining appropriate values of shear modulus for timber-based composite is not as simple and straightforward as in isotropic materials. Although the torsion test is a recommended standard approach to determine the shear modulus of structural-size timber and glulam beams, it is difficult to measure the rotational deformations of the timber beams. Therefore, in this paper, a stereo camera system combined with a photogrammetric approach is proposed to evaluate the values and variations of the shear modulus of glulam beams under the torsion test. The photogrammetric approach is a non-contact method, which provides an efficient and alternative approach for measuring the deformations of the torsion specimens in three dimensions. A series of experiments was conducted on glulam timber beams under the torsion test to investigate the applicability of the optical approach to evaluate the values and variations of shear modulus as well as to investigate the effect of applying torques in a clockwise or anticlockwise direction on the shear modulus of the beams. This optical system not only allows the performance and reliability of the traditional sensors to be assessed, but also allows the rotational deformation of the torsion samples to be monitored at various locations. This enables the values of shear modulus at different cross-sections of the torsion specimens to be evaluated without the need to use more devices. The test results showed that applying torques to the glulam timber specimens during loading and unloading in either a clockwise or anticlockwise direction does not influence or cause a significant change in the shear modulus of the beams. By comparing shear modulus values of glulam beams measured based on different shear spans, it was found that the larger the shear span the smaller the shear modulus value. This might indicate that the variations of shear modulus values at these different gauge lengths need to be considered.

Modeling of the torsion test of a cylindrical specimen with the help of the inverse method

This article discusses the torsion problem of a continuous cylindrical specimen used to construct a hardening curve. A brief review of the methods for processing the results of the method of torsion of a cylindrical specimen is given. The possibility of using the inverse method to determine the material model in the case of the torsion of the continuous cylindrical specimen made of steel 20H is shown. By means of QFORM 9.0 software package virtual experiment connected with torsion of a cylindrical specimen is carried out. As a result of this research, the rheological model of steel 20His determined with a high degree of accuracy. The stress-strain state of the material was analyzed during the torsion of the specimen by means of the QFORM. The results of the virtual experiment are compared with the full-scale test.Anexceptionally good match of the results was obtained. The inverse method showed its efficiency and made it possibleto determine a rheological model of the material. The model accurately describes the experimental data. The resulting material model (for steel 20H) is valid in the following range of parameters: deformation temperature of 20°C, deformation rate of 0.5 s−1, the strain range of 0 to 2.5.

Extending the annular in-plane torsional shear test specimen to applications at high strain rates

In-plane torsional shear testing is a well-established material testing technique in the metal forming community. The corresponding specimen is designed to be machined from sheet metal with a continuous annular shear zone intended to deform in simple shear. Consequently, there are no geometric discontinuities or “edge-effects” to induce volumetric changes or instabilities with the result that large true plastic strains up to 1.0 can be achieved. This paper presents an extension of the in-plane torsional shear test to the dynamic regime. Dynamic experiments were performed using a torsional split Hopkinson bar (TSHB) on specimens manufactured from Al 1050 H14. The experimental results show that the adopted technique can be used to determine the material behavior accurately and reliably in the dynamic regime.

Periodic formations of deformation twins and dislocation arrays via grain boundary sliding at serrated grain boundary in cold-shear-strained AZ31 alloy

It is well known that grain boundary sliding (GBS) provides stress concentration and initiates grain boundary fracture at the serrated grain boundary or grain triple junction during high-temperature creep. Recent reports on GBS occurring during deformation at room temperature suggest that stress concentration may occur due to GBS, which has a stress component parallel to the grain boundary plane, even in cold working. To identify if GBS can generate stress concentration and related defects at the grain boundary at room temperature, we experimentally investigated periodic defect formation along the serrated grain boundary during cold shear deformation. To obtain defect-free serrated grain boundary structure, optimal conditions of hot-torsion and annealing were determined. Cylindrical torsion specimens were then machined into notched tensile specimens, which provide the advantage of directly observing the GBS and lattice curvature. Extensive observations and orientation analysis on periodic defect formation along the serrated grain boundary suggest that GBS at room temperature can periodically nucleate twinning as well as dislocation arrays. Crystal plasticity simulation proved that serrated GB generates non-rotating region and split stress distribution with intensified value. Two stress concentration mechanisms during the accommodation of GBS at the serrated grain boundary were proposed: direct transfer from rotational stress and indirectly formed tensile component, namely “cleavage stress.” While direct energy transfer was likely to follow the local Schmid's law for direction of the grain rotation, cleavage accommodation represented geometrically necessary characteristics.

Cyclic shear response of additively manufactured Inconel 718

PurposeAdditive manufacturing (AM) studies on Inconel 718 (IN718) have focused on exploring its tensile and fatigue response. As IN718 is used in the propulsion and energy sector, the impact of shearing is also critical to ensuring the durability of these components. As such, this study aims to explore the relation between build orientation on the shear cyclic response of direct metal laser sintered (DMLS) IN718.Design/methodology/approachIN718 torsion specimens were manufactured along six build orientations: (100)-X, (010)-Y, (001)-Z, (110)-XY45, (101)-XZ45 and (011)-YZ45, using the DMLS process. Torsional fatigue testing was performed on as-built specimens, from which fracture behavior, surface roughness, softening/hardening response and monotonic/cyclic shear torsional properties were assessed.FindingsDMLS IN718 was found to exhibit transversely isotropic behavior. In terms of shear stress range and shear modulus, Z > (X, XY45, Y) > (XZ45, YZ45). Specimens cyclically hardened to stabilization and softened to fracture. In terms of torsional fatigue fracture response, the Z, XZ45 and YZ45 specimens exhibited crack initiation and propagation from internal defects, whereas cracks were found to initiate at the surface and propagate between and through build layers for the X, Y and XY45 specimens.Originality/valueThis study reports the torsional cyclic response and shear moduli exhibited by as-built DMLS IN718 manufactured along varying build orientations. The findings are applicable for researchers because of the wide use of IN718 in the gas turbine industry, and the current trend to replace conventional manufacturing with AM.

Strain Distributions of Plane-Strained and Simple-Sheared Al–Mg Alloy

Strain distribution in plane-strained (rolling) and simple-sheared (torsion) Al–Mg alloy has been estimated using both X-ray line profile analysis and electron backscatter technique. The strain analyses under unified texture distribution by orientation rotation showed that torsion has relatively homogeneous strain distribution regardless of texture component in contrast to inhomogeneous strain in rolling. In addition, annealing texture of torsion has more random texture than inhomogeneous rolling texture. Lower texture difference index in annealed torsion specimens suggest homogeneous strain distribution in simple shear has a higher resistance to strain-induced boundary migration, which has been known to be main reason for strong development of ND||〈100〉 component during annealing of rolled Al sheet.

WITHDRAWN: A new approach of material nonlinear finite element analysis

Abstract In this article, a novel approach is proposed for solving material nonlinear analysis problems in which a torsion problem is solved. A torsion specimen was tested in the lab and with the experimental data, shear stress and shear strain are first defined. It is to be noticed that in the basic analysis procedure, linearity assumptions are nowhere used. For example, use of shear modulus is eliminated in the basic formulation. Instead, shear stress function and shear strain functions are used as the material input. These shear stress and shear strain functions are derived from the experimental torsion-rotation data. The methodology gives ideal result, either it is linear or nonlinear range of the loading condition, with much more accuracy than the conventional linear analysis approaches. It could be realized that the methodology could be regarded as stress-based structural analysis procedure.

Surface cracks growth in aluminum alloy AW-2017A-T4 under combined loadings

The work deals with the tests results of the growth of fatigue cracks subjected to torsion and bending with torsion specimens at the constant amplitude loading and with zero or non-zero mean load. In the fatigue tests, specimens made of AW-2017A-T4 alloy with rectangular cross-section weakened by external notches were used. The results of experimental and numerical calculations were presented. During experimental investigations, heterogeneous growth of fatigue cracks at the front and rear of the specimen was noticed. Thereby, both the crack growth rate and the cracking process itself are affected. Two types of fatigue cracking were also observed: surface and passing through specimen. Crack paths were measured on the surface of the specimens using a microscope. Different lifetimes were observed for the specimens subjected only to cyclic torsion compared to those subjected to bending with torsion in the first and second periods of cracking. At the final stage of cracking, both in bending with torsion and in torsion, the difference in crack lengths for ratio a/c and a/a* is greater for R = −1 than for R = 0.

Estimation of Mode-III Interlaminar Fracture Toughness in GFRP Laminates

The composite material is heterogenous in nature has several applications ranging from sports to defence industries replacing the conventional materials. Assessing the strength composite material for out of plane delamination characterization is a challenging task. One of the test specimens which can simulate the out of the plane loading is the Edge crack torsion (ECT) specimen, to study thedelamination growth in composite laminates in a controlled environment. For the present work a fixture was developed to simulate out of plane loading and hence to estimate mode-III fracture toughness. The testcoupons werecast using from bi-directional satin glass fibre woven mat, subsequently a starter crack was introduced in the mid plane. A 100 KNInstron Universal test loadingframe was used in static condition. It was observed that the crack growth did initiate from specimen centre.The fracture parameter experimentally measured was found to bedependent on the crack growth.

Seismic performance of predamaged RC columns strengthened with HPFL and BSP under combined loadings

This paper presents an experimental investigation of the seismic behavior of coupling predamaged reinforced concrete (RC) columns strengthened with high-performance ferrocement laminate (HPFL) and bond steel plate (BSP) that are subjected to combined loadings. A total of four specimens were fabricated. After they were predamaged with corrosion and an earthquake environment, they were strengthened with HPFL and BSP, and then tested under four different combined loadings, separately, which are unidirectional compression, bending, and shear (CBS); bidirectional CBS; unidirectional compression, bending, shear, and torsion (CBST); and bidirectional CBST. Their seismic behavior, including failure mode, bearing capacity, ductility, energy dissipation, stiffness degradation, damage index and residual displacement, was analyzed. The results revealed that the coupling predamaged RC columns still had retrofit value and that the retrofitting method utilized in this paper was effective. After repairing with HPFL and BSP, the bearing capacity can be significantly improved especially for torsional specimens, which increased by more than 100%. Other seismic behavior like ductility coefficient, stiffness, and single cyclic energy dissipation can be recovered well. In addition, the horizontal eccentricity had a negative effect on the seismic behavior of specimens, while the negative effect was reduced after strengthening.

Forming properties of additively manufactured monolithic Hastelloy X sheets

Additive manufacturing (AM) of semi-finished sheets for a subsequent forming operation has not been investigated yet. The potentials in resource efficiency and effective use of build-chamber-volumes, by combining laser powder bed fusion of metals and forming technology are demonstrated. The overarching aim of this process chain are time savings of up to 50% and the benefit of material strengthening by work hardening. The scope of this paper is the understanding and characterization of the flow behavior of additively manufactured semi-finished parts for the use in a subsequent forming application of the nickel-based superalloy, Hastelloy X. Characterization methods used in sheet metal forming are applied to monolithic additively manufactured tensile, compression and in-plane torsion specimens. The resulting characterization and yield criteria can be used to predict the forming behavior of additively manufactured semi finished parts with integrated functions like cooling channels that are formed in its final geometry. A correction function is introduced to consider the surface roughness in the stress-strain diagrams. The material shows a high anisotropic yield stress with a nearly isotropic hardening behavior in the as-build condition. The heat treatment reveals a homogenization of the material accompanied with an isotropic initial yield stress but anisotropic yield behavior. To numerically model those effects, different yield surfaces based on the preceding material characterization are discussed. It turns out, that the additively manufactured Hastelloy X shows high potential in terms of formability combined with high tensile strengths.