A Physically Consistent Model for Forced Torsional Vibrations of Automotive Driveshafts

The aim of this research was to design a physically consistent model for the forced torsional vibrations of automotive driveshafts that considered aspects of the following phenomena: excitation due to the transmission of the combustion engine through the gearbox, excitation due to the road geometry, the quasi-isometry of the automotive driveshaft, the effect of nonuniformity of the inertial moment with respect to the longitudinal axis of the tulip–tripod joint and of the bowl–balls–inner race joint, the torsional rigidity, and the torsional damping of each joint. To resolve the equations of motion describing the forced torsional nonlinear parametric vibrations of automotive driveshafts, a variational approach that involves Hamilton’s principle was used, which considers the isometric nonuniformity, where it is known that the joints of automotive driveshafts are quasi-isometric in terms of the twist angle, even if, in general, they are considered CVJs (constant velocity joints). This effect realizes the link between the terms for the torsional vibrations between the elements of the driveshaft: tripode–tulip, midshaft, and bowl–balls–inner race joint elements. The induced torsional loads (as gearbox torsional moments that enter the driveshaft through the tulip axis) can be of harmonic type, while the reactive torsional loads (as reactive torsional moments that enter the driveshaft through the bowl axis) are impulsive. These effects induce the resulting nonlinear dynamic behavior. Also considered was the effect of nonuniformity on the axial moment of inertia of the tripod–tulip element as well as on the axial moment of inertia of the bowl–balls–inner race joint element, that vary with the twist angle of each element. This effect induces parametric dynamic behavior. Moreover, the torsional rigidity was taken into consideration, as was the torsional damping for each joint of the driveshaft: tripod–joint and bowl–balls–inner race joint. This approach was used to obtain a system of equations of nonlinear partial derivatives that describes the torsional vibrations of the driveshaft as nonlinear parametric dynamic behavior. This model was used to compute variation in the natural frequencies of torsion in the global tulip (a given imposed geometry) using the angle between the tulip–midshaft for an automotive driveshaft designed for heavy-duty SUVs as well as the characteristic amplitude frequency in the region of principal parametric resonance together the method of harmonic balance for the steady-state forced torsional nonlinear vibration of the driveshaft. This model of dynamic behavior for the driveshaft can be used during the early stages of design as well in predicting the durability of automotive driveshafts. In addition, it is important that this model be added in the design algorithm for predicting the comfort elements of the automotive environment to adequately account for this kind of dynamic behavior that induces excitations in the car structure.

An Update on Nickel-Titanium Rotary Instruments in Endodontics: Mechanical Characteristics, Testing and Future Perspective—An Overview

Since the introduction of Nickel-Titanium alloy as the material of choice for the manufacturing of endodontic rotary instruments, the success rate of the root canal therapies has been significantly increased. This success mainly arises from the properties of the Nickel-Titanium alloy: the biocompatibility, the superelasticity and the shape memory effect. Those characteristics have led to a reduction in time of endodontic treatments, a simplification of instrumentation procedures and an increase of predictability and effectiveness of endodontic treatments. Nevertheless, the intracanal separation of Nickel-Titanium rotary instruments is still a major concern of endodontists, with a consequent possible reduction in the outcome rate. As thoroughly demonstrated, the two main causes of intracanal separation of endodontic instruments are the cyclic fatigue and the torsional loads. As results, in order to reduce the percentage of intracanal separation research and manufacturers have been focused on the parameters that directly or indirectly influence mechanical properties of endodontic rotary instruments. This review describes the current state of the art regarding the Nickel-Titanium alloy in endodontics, the mechanical behavior of endodontic rotary instruments and the relative stresses acting on them during intracanal instrumentation, highlighting the limitation of the current literature.

Next Generation Torsional Vibration Isolation Tool Increases BHA Reliability Proven by Field Operations in North Sea

High Frequency Torsional Oscillations (HFTO) generate high torsional loads in the BHA causing cracks, damaged electronics or twist-offs. A new Torsional Vibration Isolator tool (TVI) protects the BHA by restricting vibrations to the tools between bit and TVI. Additional features have been added to the tool to automatically indicate torque overloading of the BHA and to increase torque resistance if required. This paper proves the functionality of the new features analytically, on a small-scale laboratory test and in multiple field deployments in the North Sea. New guidelines for field operations are provided. The new feature is a torsion limiter which automatically engages on reaching a critical torque threshold. The torque is then re-routed through more torque resistant BHA components. The engagement generates a characteristic signal indicating bit or BHA-overloading. The mechanical design of the new feature is presented. A criterion for engagement of the limiter and the signature indicating critical torque are analytically derived. They are experimentally validated on a scaled version of the TVI in a laboratory test. A prototype of the new tool is manufactured and deployed in multiple field operations in the North Sea previously heavily affected by HFTO. Two high-frequency measuring devices identify critical drilling situations on a scale of Milliseconds. A new guideline for utilization of this tool is developed including recommendations for BHA set-up and operational parameters. The TVI works as intended and protects the upper BHA from torsional loads generated by HFTO. The new feature engages at the predicted contact parameters. The signature indicating critical torque for the BHA was recorded and corresponds to the signature measured in the lab and predicted by the model. The TVI is best placed as close to the bit as possible, and a high-frequency measuring device in the BHA is recommended to record and transmit the contact indicators to surface. Based on field tests a parameter map for drilling torque and RPM is created that displays zones of safe operational parameters in a plain manner for field engineers. The map was validated in the field, and harmful drilling states were prevented by following the recommended drilling parameters. The next generation TVI protects BHAs from damage due to torsional vibrations. The new feature enables operations in stuck-pipe situations by increasing the torque when required. The overloading indicator prevents overstepping the torque limit of the bit and the BHA. The new parameter map and best-practice recommendations transport the learnings to the field in an easy-to-use manner.

Identification of wind turbine main-shaft torsional loads from high-frequency SCADA (supervisory control and data acquisition) measurements using an inverse-problem approach

To assess the structural health and remaining useful life of wind turbines within wind farms, the site-specific structural response and modal parameters of the primary structures are required. In this regard, a novel inverse-problem-based methodology is proposed here to identify the dynamic quantities of the drivetrain main shaft, i.e. torsional displacement and coupled stiffness. As a model-based approach, an inverse problem of a mathematical model concerning the coupled-shaft torsional dynamics with high-frequency SCADA (supervisory control and data acquisition) measurements as input is solved. It involves Tikhonov regularisation to minimise the measurement noise and irregularities on the shaft torsional displacement obtained from measured rotor and generator speed. Subsequently, the regularised torsional displacement along with necessary SCADA measurements is used as an input to the mathematical model, and a model-based system identification method called the collage method is employed to estimate the coupled torsional stiffness. It is also demonstrated that the estimated shaft torsional displacement and coupled stiffness can be used to identify the site-specific main-shaft torsional loads. It is shown that the torsional loads estimated by the proposed methodology is in good agreement with the aeroelastic simulations of the Vestas V52 wind turbine. Upon successful verification, the proposed methodology is applied to the V52 turbine to identify the site-specific main-shaft torsional loads and damage-equivalent load. Since the proposed methodology does not require a design basis or additional measurement sensors, it can be directly applied to wind turbines within a wind farm that possess high-frequency SCADA measurements.

Understanding the relationship between composition and rheology in alkali-activated binders

Based on the knowledge that exists today, it is generally accepted that there are basic parameters and characteristics to obtain effective mixtures for their use in 3D printing. Rheological behavior and setting time (initial and final) are those characteristics that determine workability, as well as the speed and nature of hardening of the molded pastes and, as a result, the final framework and the integrity of the resulted structure. Among the promising options for 3D printing, the literature often contains information on alkali-activated binders. In this work, an alkali-activated binding system based on electrometallurgical slag, as well as citrogypsum, a waste of the industrial production of citric acid, was studied. Some rheological characteristics of experimental binders were considered: the nature of the mixture flow under the action of torsional loads and their initial and final setting times. It was found that the joined use of both components in the experimental system “slag - water”: an alkaline activator and citrogypsum, promotes the transition of the character of the system from thixotropic to mixed: dilatant-thixotropic (for the Na2SiO3 activator) and dilatant (for the NaOH activator). It was found that the addition of alkaline activators and citrogypsum to the binding system separately in both cases helps to reduce the initial and final setting times from 18 and 22 hours to 1 hour and 1.5 hours. Also, experimental results have shown that the jointed action of both components: an alkaline activator and cytogypsum, has a synergistic effect on the setting time.

FRP pipeline performance in tensional and torsional S-lay installation loads

The loading conditions of a composite pipeline is the main factor for its dimensioning. During S-lay offshore installation of multilayered FRP pipelines, severe tensional and torsional loads take place in the above sea part of the pipeline. Since the wall pipe is multilayered and the material properties of the laminae and the laminate is anisotropic, the maximum stresses depend on the stacking sequence. In the present work, an analytical model is proposed for calculating the capacity of multilayered FRP pipelines to carry axial and torsional loads. Numerical results for typical multilayered filament wound E-Glass/Epoxy pipelines under axial tension and torsion are provided and discussed.

Three-dimensional numerical analysis of tubular adhesive joints under torsional loads

Bonding method using adhesives has gained a lot of presence in the design of mechanical structures in several industries, especially in the aeronautics and automobile industry. Bonded joints are widely used to join tubular components, in vehicle frames like aeroplanes and automobiles. For the design process of these joints, analytical or numerical predictive techniques can be used. This work performs a numerical study in order to evaluate the torsional performance of aluminium tubular adhesive joints (AW6082-T651), considering the variation of the main geometric parameters, such as overlap length (L O) and tubes’ thickness. In order to predict the strength, the Finite Element Method (FEM) was used with Cohesive Zone Models (CZM), whose analysis based itself on the internal stresses of the adhesive, namely the analysis of shear stress (τxy) and joint strength, measured by the maximum torsional moment (M m). Previously, validation with experimental data was carried out. The technique was positively validated, and a significant geometry on M m was found, except for L O.

Torsional Crack Localization in Palm Oil Clinker Concrete Using Acoustic Emission Method

Palm oil clinker (POC) aggregates is a viable alternative to the naturally occurring sand and gravel in the manufacturing of concrete. The usage of POC aggregates assists in the reduction of solid waste and preserves the consumption of natural resources. Although researchers investigated the mechanical response of POC-containing concrete, limited research is available for its torsional behavior. In general, the torsional strength depends on the tensile strength of concrete. This research investigates the compressive, tensile, and torsional response of concrete with various ratios of POC-aggregates. Five batches of concrete were casted with POC-aggregate replacing granite at ratios of 0, 20, 40, 60, and 100%. The selection for the mixture proportions for the various batches was based on the design of experiments (DOE) methodology. The hard density, compressive strength, splitting tensile strength, and flexural strength of concrete with a 100% replacement of granite with POC-aggregates reduced by 8.80, 37.25, 30.94, and 14.31%, respectively. Furthermore, a reduction in initial and ultimate torque was observed. While cracks increased with the increase in POC-aggregates. Finally, the cracking of concrete subjected to torsional loads was monitored and characterized by acoustic emissions (AE). The results illustrate a sudden rise in AE activities during the initiation of cracks and as the ultimate cracks were developed. This was accompanied by a sudden drop in the torque/twist curve.

Failure Analysis on the Fracture Shaft of a Centrifugal Pump Used for Diesel Engine Cooling System

Shaft failures often occur, even in the shafts of centrifugal pumps. This study aims to determine the cause of shaft fracture through experimental and numerical study. The fracture surface was observed using Scanning Electron Microscopy (SEM) to identify the initial crack. The chemical composition test results show that the material used was in accordance with the AISI 420 standard, which is necessary to make Finite Element Analysis (FEA) modelling. Shear stress, strain and stress intensity factors were analysed around the fillet using FEA. The results show that the value of maximum stress intensity factor, KI, occurs in the multilevel shaft fillets that experienced initial cracks due to torsional loads. The shear stress value, obtained from the FEA, was higher than the shear stress value of the material. The KI value, also derived from the FEA, was higher than the KICvalue of the material.