Cyclic Torsion Research Articles

Experimental study on the magnetic pulse welding process of large aluminum tubes on steel rods

Solid state welding technologies enable dissimilar metal welding without critical intermetallic phase formation. Magnetic Pulse Welding (MPW) is a promising joining method for hybrid sheet connections in car body production or for manufacturing of dissimilar tube connections. Given a suitable MPW process design, the shear testing of MPW joints usually leads to failure in the weaker base material. This finding emphasizes the high strength level of the joining zone itself. Consequently, the transmission of higher forces or torques, respectively, requires stronger materials or adapted geometries. In the present experimental study, the diameter of an exemplary driveshaft was doubled to 80 mm at constant tube wall thickness to increase the load bearing capability. The characteristic impact flash was recorded at different positions around the tube’s circumference and it was used to adjust the most relevant process parameters, i.e. working length and acceleration gap, at the lower process boundary. In metallographic analysis, the final shapes of both joining partners were compared with the original driveshaft dummies on macroscopic and microscopic scale. The typical wavy interface between aluminum and steel was analyzed in detail. Doubling the tube diameter lead to four times higher torque levels of failure during quasistatic and cyclic torsion tests.

Inclusion initiated fracture under cyclic torsion very high cycle fatigue at different load ratios

The influence of inclusions on cyclic torsion very high cycle fatigue (VHCF) is studied at different load ratios. Testing material is a high-strength spring steel, which was prepared based on the SWOSC–V composition with intentionally increased number and size of inclusions. Ultrasonic torsion fatigue tests were performed at load ratios R = –1, R = 0.1 and R = 0.35 with shot peened specimens. All specimens that were cycled at R = 0.1 or R = 0.35 and failed above 108 cycles showed crack initiation at internal aluminate or MnS inclusions. Interface failures between particles and metallic matrix generate cracks at aluminate inclusions, which predominantly grow in mode I. MnS inclusions have an elongated shape oriented in the specimens' length direction. Shearing of the MnS inclusions generates initial mode II/mode III cracks, which subsequently branch to mode I cracks. All specimens cycled at R = –1 showed surface crack initiation without inclusions, irrespective of lifetime. S–N curves are shifted towards lower shear stress amplitudes with increasing load ratio, indicating a pronounced mean stress influence on cyclic torsion strength.

Effect of strain reversal on the stress-induced martensitic transformation and tensile properties of a metastable β titanium alloy

In this study, the effect of strain reversal on the evolution of microstructure and mechanical properties was investigated. Metastable β titanium alloy samples with single β phase were twisted up to 360° with different strain paths: monotonic torsion (MT) and cyclic forward-reverse torsion (CFRT). The results revealed CFRT with strain reversal accumulated lower dislocation density and less martensitic transformation in comparison with MT under the same accumulative strain. The stress-induced martensitic transformation (SIMT) was retarded by strain reversal and this suppression of martensitic transformation is more pronounced with the decreasing amplitude of strain reversal. It was further observed that CFRT samples with a gradient α″ martensite have a higher mechanical property both in strength and ductility than MT samples, which are due to interactions between α″ martensite and dislocation slip, especially the kinks of α″ martensite.

On the cyclic torsion of elliptic curves over cubic number fields (II)

Merel’s result on the strong uniform boundedness conjecture made it meaningful to classify the torsion part of the Mordell–Weil groups of all elliptic curves defined over number fields of fixed degree d. In this paper, we discuss the cyclic torsion subgroup of elliptic curves over cubic number fields. For N=49,40,25 or 22, we show that ℤ/Nℤ is not a subgroup of E(K) tor for any elliptic curve E over a cubic number field K.

Characteristics of shear-mode fatigue crack growth behaviors in roll materials

The shear-mode fatigue crack behavior of work roll materials for hot strip mills was evaluated using cyclic torsion with superimposed static compression. Most of the deep cracks in rolls have grown under shear-mode during rolling, however there has been no practical methods to evaluate the fatigue behavior of roll materials in the presence of shear-mode crack, which has been a big obstacle for development of the work roll materials, especially the advanced materials like the high speed steel type roll materials. The present study shows that a high speed steel material has preferable torsional fatigue behavior than an enhanced ICDP (Indefinite Chill Double Poured cast iron). However, in actual rolling, the enhanced ICDPs generally show better crack resistance than high speed steel roll type materials. Accordingly, further research is necessary utilizing the testing method.

Assessment of the risk of fatigue damage in biaxial stress state

The paper contains the biaxial fatigue test results of specimens with round cross-section, made of 10HNAP steel. The tests under cyclic bending and torsion were carried out for the following ratios of normal to shear stresses amplitudes σa / τa = 0.5, 1, 2 and the loading frequency was 26.5 Hz. The tests were performed in the high cycle fatigue regime for the stress ratio R = - 1 and phase shift between bending and torsion equal to φ = 0 and 90°.

Crack growth and microstructural changes in AISI 52100: white etching cracks (WEC) and fine granular area (FGA)

The service life of rolling element bearings can usually be predicted with good accuracy. However, the damage phenomenon „white etching cracks” (WEC) can lead to premature and unforeseeable failures. The formation of zones with strongly decreased grain sizes at the crack faces is a characteristic of this type of failure. An earlier study showed that it is possible to reproduce this type of failure by multiaxial fatigue experiments with superposed cyclic compression and torsion. The present study shows the analysis of the stress state of those multiaxial fatigue tests with stress-based critical plane criteria. Using the critical plane results as a basis for a fracture mechanical analysis, a correlation is found between the crack length, the associated plastic zone size, and the extent of the transformed microstructure. This correlation is very similar to our results of the study of fine granular areas (FGA), a very high cycle fatigue phenomenon in bearing steels. It is argued that a plasticity-driven mechanism similar to the one proposed for FGA formation is responsible for WEC formation, too. Additional factors that are often cited as promoting WEC formation could explain the shift from very high cycle fatigue in the case of FGA to the early failures due to WEC.

Gradient hierarchical grain structures of Al0.1CoCrFeNi high-entropy alloys through dynamic torsion

Al0.1CoCrFeNi high-entropy alloys are firstly processed by cyclic dynamic torsion (DT) using Split-Hopkinson Torsional Bar. Gradient hierarchical microstructures produced by DT are investigated using electron backscattered diffraction, transmission electron microscopy, and nanoindentation tests. Based on the gradient torsional strain, significant grain refinement, remarkable work hardening, and hierarchical deformation substructures are introduced into the current DT-HEAs.

Improved Methods Aid Understanding and Mitigation of Stick/Slip Torsional Vibrations

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 189673, “Improved Methods To Understand and Mitigate Stick/Slip Torsional Vibrations,” by J.R. Bailey, SPE, G.S. Payette, SPE, and L. Wang, SPE, ExxonMobil, prepared for the 2018 IADC/SPE Drilling Technology Conference and Exhibition, Fort Worth, Texas, USA, 6–8 March. The paper has not been peer reviewed. Historically, prediction of stick/slip vibrations in advance of drilling has been fraught with challenges. Although the factors influencing stick/slip, and the directional changes required to mitigate it, are known, a need exists for a simple method to determine quantitatively the degree of dysfunction and the effects of redesign parameters. This paper will show how stick/slip vibration distributions can be used to guide drillstring and parameter redesign to mitigate stick/slip in the next well. Background Torsional vibrations, also known as stick/slip, occur as the rotational speed of the bit and drillstring vary because of stiffness, inertia, and torsional friction interactions. In some wells, these torsional/rotational fluctuations are not severe and may not reach full stick/slip, which occurs when the bit comes to a full stop in the torsional vibration cycle. The drilling data obtained in the drilling of a well are displayed typically as time or depth tracks, with different parameters shown on the same or adjacent tracks over the corresponding time or depth interval. Although of interest, this display of data is limited. It does not provide a direct indication of the amount of dysfunction present over the duration of the interval. A histogram is a particularly useful display of the distribution of data values. In the case of stick/slip vibrations, the torsional-severity estimate (TSE) is a measure of proximity to full stick/slip. A TSE value of 0.0 represents no torsional vibrations, where the entire drillstring is turning at a constant angular velocity. A TSE of 1.0 represents full stick/slip, in which the rotary speed at the surface is constant but the bit speed varies sinusoidally between zero and twice the surface rotary speed. Values of TSE greater than 1.0 indicate time intervals in which the bit comes to a complete stop and then accelerates to more than twice the surface rotational speed. The most severe cases may even involve negative rotation of the bit. Analytical tools that help assess the degree of torsional vibrations can be useful, especially in those instances where known remediation techniques are not available or may be costly. A variety of methods exists to address torsional vibration problems, and the most-cost-effective method may be the method of choice. The authors are not aware of simple analytical methods that can provide quantitative evaluation to address the following: How will the stick/slip problem change if the drillstring design is modified? How will stick/slip change if the operating parameters are modified? The bit-design parameters may be varied to increase or decrease bit torque. How will changes to the bit friction factor affect stick/slip vibrations in a certain application?

Strength changes of 40 Cr steel subjected to cyclic torsion below the fatigue limit

Abstract This paper investigates the fatigue and static strength variation of 40 Cr steel which has been subjected to cyclic torsion below the fatigue limit. The experimental results show that an improvement in fatigue strength can be exhibited if low-amplitude cyclic torsion and loading cycles are properly selected. The static strength can also be strengthened through the improvement of fatigue strength. It should be added that there is no significant static strength change in the first 50 % of the fatigue damaging process.

Cyclic Torsion Behavior of Prestressed Concrete Beams

The nonlinear finite element analysis has become an important tool, for the structural design and assessment of prestressed reinforced concrete members. However, design and assessment of torsion are still done with simplified analytical or empirical design methods. This paper pre-sents results from a numerical analysis using the ANSYS finite element program to simulate a prestressed concrete beams subjected to static and cyclic torque. The eight- node brick ele-ments SOLID65 are used for the idealization of concrete while the reinforcements are idealized by using 3D spar element LINK8. The steel plates are idealized by using three dimensional solid elements SOLID45. The results showed that the general behavior of the finite element models represented by torque- twist angle relationships show good agreement with the experimental results from the Abdullah's beams.

Size effect on cyclic torsion of micro-polycrystalline copper considering geometrically necessary dislocation and strain gradient

To predict the cyclic plasticity behavior of polycrystalline copper on the micro scale for fully reversed torsion, a model, which expresses back stress in an Armstrong-Frederick form, is developed. The model parameters are size dependent and correlate with the critical density of geometrically necessary dislocations (GNDs). For monotonic loading, the flow stress satisfies the parabolic Taylor relation, and a mathematical equation is derived that expresses the flow stress as the superposition of internal variables, such as back stress and yield stress. With this new expression of flow stress, the parameters for the saturated value of back stress are found to relate to GNDs. Although the flow stress is dominated by the dislocation pile-up under fully reversed torsion loading, the parameters do not change with the overall dislocation density but remain constant. It is assumed that the critical GND density is determined by the strain range, and related to level of dislocation pile-up. Moreover, our model is verified by simulation, and satisfactory results are obtained for facts such as strength increase, cyclic hardening, the Bauschinger effect, and plasticity recovery.

Effects of Level, Loading Rate, Injury and Repair on Biomechanical Response of Ovine Cervical Intervertebral Discs.

A need exists for pre-clinical large animal models of the spine to translate biomaterials capable of repairing intervertebral disc (IVD) defects. This study characterized the effects of cervical spinal level, loading rate, injury and repair with genipin-crosslinked fibrin (FibGen) on axial and torsional mechanics in an ovine cervical spine model. Cervical IVDs C2-C7 from nine animals were tested with cyclic tension-compression (-240 to 100N) and cyclic torsion (± 2° and ± 4°) tests at three rates (0.1, 1 and 2Hz) in intact, injured and repaired conditions. Intact IVDs from upper cervical levels (C2-C4) had significantly higher torque range and torsional stiffness and significantly lower axial range of motion (ROM) and tensile compliance than IVDs from lower cervical levels (C5-C7). A tenfold increase in loading rate significantly increased torque range and torsional stiffness 4-8% (depending on amplitude) (p < 0.001). When normalized to intact, FibGen significantly restored torque range (FibGen: 0.96 ± 0.14, Injury: 0.88 ± 0.14, p = 0.03) and axial ROM (FibGen: 1.00 ± 0.05, Injury: 1.04 ± 0.15, p = 0.02) compared to Injury, with a values of 1 indicating full repair. Cervical spinal level must be considered for controlling biomechanical evaluations, and FibGen restored some torsional and axial biomechanical properties to intact levels.

Evaluating fatigue resistance of toner-modified asphalt binders using the linear amplitude sweep test

This paper examines the effect of waste toner on fatigue resistance of asphalt binder. Fatigue resistance of toner-modified asphalt binders was studied implementing the linear amplitude sweep test, which has been approved by AASHTO as a provisional standard and is currently being considered as a specification test for evaluating fatigue resistance of original and modified asphalt binders. The linear amplitude sweep is a cyclic torsion test conducted with a dynamic shear rheometer (DSR) which uses increasing loading amplitudes to accelerate the damage process. In order to characterise a waste toner as an additive for modifying an original asphalt binder, the XRD test has been done. DSR test results were used to determine fatigue resistance parameters and dissipated energy ratio to investigate fatigue behaviour of toner-modified asphalt binders. This paper argues that the improved fatigue resistance properties of toner-modified asphalt binders are reflected in the enhancement of the number of loading cycles, shortening crack length and degrading dissipated energy which remains in the specimens.

Activation volume and energy of bulk metallic glasses determined by nanoindentation

Nanoindentation strain-rate jump testing was used to determine activation volumes and energies of various metallic glasses and composites. Three different single phase metallic glasses and three composites (two with amorphous/crystalline Cu and one with an amorphous/amorphous structure) were investigated. The state of the materials was additionally changed by varying the testing temperature between room temperature and 430°C, by performing high pressure torsion and by thermal cycling. The results show that testing temperature is the main parameter controlling activation volume and energy, whereas material modifications by high pressure torsion and thermal cycling do not significantly affect them.

Remarks on the $${\mathrm {CH}}_2$$ CH 2 of cubic hypersurfaces

This paper presents two approaches to reducing problems on 2-cycles on a smooth cubic hypersurface X over an algebraically closed field of characteristic \(\ne 2\), to problems on 1-cycles on its variety of lines F(X). The first one relies on osculating lines of X and Tsen-Lang theorem. It allows to prove that \({\mathrm {CH}}_2(X)\) is generated, via the action of the universal \({\mathbb {P}}^1\)-bundle over F(X), by \({\mathrm {CH}}_1(F(X))\). When the characteristic of the base field is 0, we use that result to prove that if \(dim(X)\ge 7\), then \({\mathrm {CH}}_2(X)\) is generated by classes of planes contained in X and if \(dim(X)\ge 9\), then \({\mathrm {CH}}_2(X)\simeq {\mathbb {Z}}\). Similar results, with slightly weaker bounds, had already been obtained by Pan (Math Ann 1–28, 2016). The second approach consists of an extension to subvarieties of X of higher dimension of an inversion formula developped by Shen (J Algebraic Geom 23:539–569, 2014, Rationality, universal generation and the integral Hodge conjecture, arXiv:1602.07331) in the case of 1-cycles of X. This inversion formula allows to lift torsion cycles in \({\mathrm {CH}}_2(X)\) to torsion cycles in \({\mathrm {CH}}_1(F(X))\). For complex cubic 5-folds, it allows to prove that the birational invariant provided by the group \({\mathrm {CH}}^3(X)_{tors,AJ}\) of homologically trivial, torsion codimension 3 cycles annihilated by the Abel–Jacobi morphism is controlled by the group \({\mathrm {CH}}_1(F(X))_{tors,AJ}\) which is a birational invariant of F(X), possibly always trivial for Fano varieties.

Torsional fatigue with axial constant stress of oligo‐crystalline 316L stainless steel thin wire

AbstractA series of symmetric torsional fatigue with axial constant stress tests, a kind of multiaxial fatigue test, was conducted on oligo‐crystalline 316L stainless steel thin wire, which was less than 3.5 grains across diameter of 200 μm. The material presents significant cyclic hardening under symmetric torsion cycling, and hardening is more obvious with the increasing shear strain amplitude. However, symmetric torsional cycle with constant axial stresses tests characterize rapid initial hardening and then gradually softening until fatigue failure. The axial stress has a great effect on torsional fatigue life. Fractography observation shows a mixed failure mode combined torsional fatigue with tensile strain because of axial tensile stress. A newly proposed model with axial stress damage parameter is used to predict the torsional fatigue life with constant axial stress of small scale thin wire.

Fatigue Property of High Strength Steel with Artificial Defects under Cyclic Torsion with a Shear Stress Ratio of 0.1

Fatigue Property of High Strength Steel with Artificial Defects under Cyclic Torsion with a Shear Stress Ratio of 0.1

Correlation of Uniaxial Cyclic Torsion and Tension-Compression for Low-Cycle Fatigue

We analyze the comparison of the fatigue characteristics and, in particular, the coefficients of tensioncompression and cyclic torsion based on the data of available tests performed under low-cycle fatigue in various materials. The correlation of torsion and tension-compression fatigue strength coefficients does not depend on the relative slope of the fatigue diagrams used to describe plastic strains. On the basis of the performed analyses, we conclude that the ratio of the fatigue strength coefficients in tensioncompression varies, in most materials, within the range from 0.5 to $$ \frac{1}{1+\nu } $$ . At the same time, the correlation of the strain-based fatigue coefficients in torsion and in tension-compression strongly depends on the relative slope of the plastic strain-based curves of fatigue life.

Effect of mean shear stress on the fatigue strength of notched components under multiaxial stress state

The effect of a static and intermittent shear stress on the HCF strength of two quenched and tempered steel grades used to produce shafts in crane industry was studied on notched specimens (Kt,bending=1.7 and 2.7) for being representative of critical areas. Three main loading configurations were considered: C1=rotative bending (RB), C2=RB and static torsion and C3=RB and mean torsion fluctuating in blocks to simulated start and stop cycles. In this last case the first investigated mean shear stress, τm, was equal to the material yield stress in pure shear, τy. Additional C3 variants were investigated too where τm was equal to 0.3τy and 0.7τy. It has been shown that τm has little effect on the rotating bending HCF strength at 3×106 cycles. For both steel grades and notch geometries studied, the results of the fatigue tests confirm that the influence of a static torsion on the rotating bending HCF strength is negligible even when the static torsion level is equivalent to the yield strength of the material in torsion. However, in intermittent service conditions (C3), it has been shown that torsion cycles can affect significantly the HCF strength in RB, depending on the notch acuity and torsion level. Elastic-plastic cyclic finite element analysis has been done for the two specimen geometries to assess the stabilized stress-strain state at the notch root and then compute the fatigue life by using the multiaxial HCF models proposed by: Fatemi-Socie, Smith-Watson-Topper, and Wang-Brown. The Palmgreen-Miner hypothesis was used to cumulate damage mainly because of its simplicity for design purposes. According to our simulations and with the chosen cumulative damage rule, none of the tested fatigue life calculation methods give good results for all the load cases. The efficiency of the tested methods is very dependent on both the material and the load cases. However, the Smith-Watson-Topper approach gives the best results whereas the Fatemi-Socie model leads to the more conservative ones except in one load configuration.