Use Of Strain Gauges Research Articles

Impact force measurement by in-plane piezoelectricity of polyvinylidene fluoride films

This manuscript provides a new idea to solve the problems related to measurement of impact force wave especially in the situation with a strong environment noise by utilizing the polyvinylidene fluoride (PVDF) film instead of strain gauge. According to our experimental results, an extremely high ratio between output signal and noise in environment (SN ratio) is realized even the infrequently employed in-plane piezoelectricity of film is utilized. Instead of piezoelectricity in thickness direction, attachment of film on Hopkinson pressure bar based on in-plane piezoelectricity could help us to avoid the influence from separation of Hopkinson pressure bar on measurement result. We could conclude that a more precise measurement could be realized by a short film rather than long one even though the short film shows a relative lower output signal. However, the output signal could be amplified by increasing its width. Besides, comparing with the use of strain gauge, broader bandwidth of film measurement is discovered. In the situation where the duration of impact force wave is extremely short, high accuracy measurement should be realized by PVDF film rather than strain gauge.

Modal, Structural, and Comfort Analyses for Improving Customized Bicycles for Recreational Ridings of People with Disabilities

Leisure activities are known to be especially important for the health of people with disabilities. In Belém, PA, an Amazonian city in Brazil, a nonprofitable organization has promoted leisure ridings in bicycles for those people in Utinga State Park, a large green area for physical and leisure activities. The handcrafted bikes have a sidecar attached for users with disabilities which are ridden by trained volunteers. Since such bikes have been empirically manufactured, they require some minor improvements in safety, comfort, and handling, and verification of structural strength. Therefore, ergonomic, modal, and forced vibration analyses assessed the user’s comfort and safety and a structural analysis with the use of strain gauges evaluated the bicycle’s structural strength. Initially, a numerical modal analysis was performed using the finite element method, and the modal model obtained was validated by an experimental modal analysis employing shaker excitation. ISO-2631-based evaluations of forced vibration and human body comfort were conducted regarding whole-body vibration in vehicles and mechanical equipment. Vibration measurements at the position of the rider and sidecar occupant were obtained during rides on the bicycle and, according to the results, in general, when subjected to loads, the bicycle showed low stress levels far from the yield stress of the material, promoting an excellent safety factor in relation to its structural integrity. The modal, comfort, and forced vibration analyses revealed a mode of vibration in the sidecar that caused discomfort to the back of the users. Ergonomics analysis pointed out changes in the handlebars, the bicycle seat, the coupling between the sidecar and the bike, and the dimensions of the sidecar will provide greater comfort and safety. This paper presents and discusses the proposed modifications to both bicycle and sidecar.

Telemetry System to Monitor Elastic Torque on Rolling Stand Spindles

This article outlines the relevance of building online telemetry systems for online monitoring of the technical conditions of rolling mill equipment. Electromechanical systems of the horizontal stand of the plate Mill 5000 are described, when operating in harsh conditions caused by the shock loading when workpieces enter the stand. It is noted that dynamic torque overloads, exceeding the rated motor torque by many-fold, cause the fatigue failure of spindle joints and breakage of rolls. In this regard, the development and implementation of systems for monitoring the elastic torque on spindles are extremely urgent. This issue has long been studied, but the references provide no information on the building principles and hardware composition of such systems. The use of strain gauges connected according to a balanced bridge circuit to measure the elastic torque is justified. This paper’s contribution is the proposed modular principle for building a telemetry monitoring system based on the analysis of known techniques for measuring and transmitting diagnostic data. The developed system structure is provided and the concept of data transfer and processing are explained. This article suggests the inductive power supply of a measuring unit mounted on a shaft without the use of batteries. A hardware structure was developed to be applied in a system for measuring, transmitting, and visualizing signals proportional to the elastic torque, manufactured on the basis of data measuring instruments by leading companies. The specifics of placement and connection of strain gauges are considered. The hardware providing a wireless power supply to the signal encoder and digital data transfer between the transmitter and receiver is described. The results of implementing the system on Mill 5000 are provided. The installation of a telemetry ring and a receiving head for the inductive power supply and data reception is shown. An experimental assessment of the elastic torques occurring when workpieces enter the cage was obtained by implementing a drive control algorithm which provided biting in the drive acceleration mode. The reliability of measuring the elastic torque with an error not exceeding ±5% and the reduction of dynamic loads on the spindle by 1.3–1.5 times due to the elimination of impacts from closing angular gaps in spindle joints was confirmed. This increases the service life of mechanical equipment and reduces the cost of eliminating the accident aftermath. The prospect of modifying the developed system into a cyber-physical system for monitoring the rolling mill’s mechatronic equipment conditions is shown.

A novel damage identification algorithm by combining the boundary element method and a series connection neural network

A novel damage identification approach based on a model-driven and a data-driven combined algorithm is developed. By using this approach with only boundary strains, the existence, location, classification as well as the extent of the damage in a plate can be predicted at once with high accuracy and efficiency. To accumulate the data, the boundary element method (BEM) is applied as a model-driven in modeling plates with one or multiple damages in the forms of circular or elliptical holes or cracks and for solving the boundary strains of the defective plates. The dimensionality reduction and semi-analytical characteristics of BEM not only can compress the feature data also can improve the accuracy of the database for the data-driven algorithm. The boundary strains are obtained directly from BEM models, which are also easily collected through the use of strain gauges mounted on the surfaces of structures being monitored in real applications. A series connection neural network algorithm is established to accomplish the novel damage identification assignments with deep learning. The number of the existing damages is firstly detected by a classification neural network model, then the extracted features are transmitted to the corresponding regression neural network model to prognosis the location, classification as well as the extent of each flaw. A high accuracy of about 99.86 % is achieved by the present combined neural network algorithm, which is promising in applications of actual structural health monitoring.

Experimental investigation of fixed-ended hot-rolled austenitic stainless-steel unequal-leg angles under compression

Structural stainless steel is gaining traction in the structural engineering field, however, there is currently limited published data on the performance of stainless steel unequal-leg single-angle compression members. This limitation of published data is reflected in the recently released AISC 370: Specification for Structural Stainless Steel Buildings which is limited in scope to equal-leg cross sections. Furthermore, the Specification requires the consideration of flexural–torsional buckling for single angles which is in contrast to the original design guidelines from AISC published in 2013, which mirrored the carbon steel specifications and did not required checking for flexural–torsional buckling for single angles. This paper reports a comprehensive experimental study on the behavior of hot-rolled austenitic stainless steel unequal-leg angle columns. A series of unequal-leg angles with cross-sectional dimensions of 76.2 × 50.8 × 6.35 mm (3″× 2″× 1/4″) and lengths ranging from 250 mm (10″) to 3760 mm (148″) were tested in compression. The ultimate loads were recorded in addition to displacements, twists, and failure modes through the use of strain gauges and an optical tracking system. The material properties were obtained through a series of tensile coupon tests, and the member geometric imperfections were measured through a non-contact 3D laser scanning technique. In addition, residual stress distributions were measured by the sectioning method. The results obtained from this experimental investigation indicated: (1) that torsional buckling is dominant in the shorter lengths and minor-axis flexural buckling in the longer lengths, with a transition occurring gradually in the middle lengths; (2) that the measured material properties are significantly higher than nominal values, and that this had a significant effect on the capacity predicted by the design provisions; (3) flexural buckling design provisions provide a better estimation than flexural–torsional buckling design provisions, although both are conservative.

Design and FEM Analysis of Plastic Parts of a Tie-Rod Composite Hydraulic Cylinder

Due to a number of advantages, such as a high ratio of power transmitted to the weight of the system, the possibility of easy control and the freedom to arrange system elements on the machine, hydrostatic drive is one of the most popular methods of machine drive. The executive elements in such a system are hydraulic cylinders that convert the energy of the pressure of the liquid into the mechanical energy of the reciprocating motion. One of the disadvantages of conventional actuators is their weight, so research is being done to make them as light as possible. The directions of this research include the use of modern engineering materials such as composites and plastics. The paper presents the process of designing, FEM analysis and experimental validation of the base and gland of a composite hydraulic cylinder. The considered elements are made of PET plastic. During the analysis, material non-linearity was taken into account, and the analysis itself was carried out in two steps. The first was the preloading of the tie-rods, and the second was the loading of the cylinder with internal pressure. The numerical calculations were experimentally validated by prototype tests with the use of strain gauges.

Model tests of a stiffness-similar jack-up, Part 2: In-place and hull-in-water conditions

This paper, Part 2 of a series, presents a comprehensive study involving ocean basin model tests of a novel stiffness-similar jack-up structure. The objective is to generate a high-quality dataset for the development of structural digital twins. The focus is on the model test design and selected results for in-place and hull-in-water conditions. The generic jack-up model was instrumented with strategically placed sensors on the hull, legs, leg-to-hull connections, and spudcan modules. The novel use of polycarbonate for the jack-up legs ensures stiffness similarity, enabling the use of strain gauges to derive axial member forces. Boundary forces were meaningfully measured, because of the representative modelling of the foundation and leg-to-hull connection fixity. The test cases encompassed long-crested waves, including conditions with and without current. In addition, oblique waves were modelled by rotating the entire jack-up model. Both extreme and operating scenarios were considered. In operating scenarios, the dynamic responses of the jack-up structure were found primarily governed by structural resonance, while wave frequency responses became comparable in extreme scenarios. For extreme scenarios, dynamic wind loads, consistently Froude-scaled to the model scale, were applied using a servomotor in the presence of random waves. Comparisons between results with and without the applied dynamic wind loads revealed noticeable differences in damping characteristics. The hull-in-water condition exhibited significantly larger motion and structural responses, emphasising its criticality in jack-up operations. The findings underscore the importance of considering the hull-in-water condition in the analysis and operation of jack-up structures.

Development, analysis, and verification of an intelligent auxiliary beekeeping device mounted on a crawler transporter

The transportation of beehives poses a significant challenge in the beekeeping industry. To address the manual handling practices prevalent in the beekeeping industry and enhance the automation level, this study attempts the design and development of a mobile auxiliary beekeeping device mounted on a caterpillar vehicle for beehive transportation. Specifically, the design of the auxiliary device was completed in SolidWorks with the notion of the cylindrical mechanical arm. Subsequently, a dynamic model of the simulated environment is constructed using RecurDyn, facilitating the determination of the torque requirements for each joint based on the dynamic model. Furthermore, the multi-flexible body dynamics analysis is utilized to conduct a flexible analysis of the auxiliary beekeeping device’s three principal components and the maximum beehive weight, which can be safely transported, is estimated through simulation analysis. Particularly, field experiments involve the use of strain gauges to measure the stress exerted on the components of the auxiliary beekeeping device during actual beehive transportation. Additionally, it incorporates the errors and precision associated with each joint, and the planar positioning accuracy result. Meanwhile, the maximum torque required for the joints, which is about 5 N·m was determined by simulation results, affirming that the selected drive motors can meet the operational requirements. Through simulation, it is determined that the auxiliary device can handle a maximum beehive weight of 126 kg, approximately three times the weight of the standard beehives (40 kg) utilized in beekeeping farms. This ensured that the auxiliary device poses no risk of overturning during the beehive transportation. In addition, the stress levels at crucial locations are ascertained through on-site strain experiments. Interestingly, the auxiliary support part (57.68 MPa) and the spindle connection (58.8 MPa) experienced the highest stress levels; and the stress levels in the telescopic rod and lower support part remained below 5 MPa. In particular, these stress levels fall within the permissible range of the materials employed (200 MPa), which ensures the auxiliary device’s safe utilization. An evaluation of each joint’s operational accuracy showed that the planar positioning accuracy result of joint 1 and joint 2 is 9.65 mm for 50% CEP and 23.55 mm for 95% CEP, respectively. Furthermore, the highest final error was exhibited by the vertical extension joint (11.48 mm), indicating that the auxiliary device can successfully accomplish the beehive transportation tasks within beekeeping farms. Overall, this research provides a solid foundation for the subsequent development of automated beehive handling devices.

Features of measuring deformations of load-bearing structures of buildings during their field and laboratory tests under the action of static and dynamic loads

The peculiarities of measuring the deformations of load-bearing structures of buildings during their field and laboratory tests using strain gauge-based sensors are considered. An overview of various problematic issues that arise in the process of conducting experimental tests and affect the measurement results is given. The most common, which affect the accuracy of measurements, are the effects of temperature, humidity, and vibration; the difficulty of calibrating and mounting strain gauges on different surfaces of elements; complexity of measurement data processing; combination of high-quality work of strain gauges, cable conductors, measuring equipment, data collection and processing system; the selection of the connection scheme of tensor resistors in the Wheatstone bridge. The peculiarities of the organization of the experiment for testing the load-bearing structures of the building, namely pile foundations, are considered, and the main problematic issues when using strain gauges as strain gauges of building elements are given. The use of strain gauges to measure deformations of load-bearing structures of buildings is one of the common methods, which has many advantages, which are discussed in detail in the work. Strain gauges can be used to measure deformations of elements that are mechanically connected to them. They have high measurement accuracy, sensitivity to element deformation, and a wide variable measurement range. The advantages of using the Wheatstone bridge to measure the change in electrical resistance are highlighted, as this method allows measuring very small values of the change in resistance. Methods of connecting tensor resistors according to the Wheatstone scheme are considered, the choice of which depends on the purpose of the study and the required accuracy. One of the easiest ways is to connect just one strain gauge to a current or voltage source and measure the change in resistance. But this method has low sensitivity and does not compensate for the effect of temperature. A more accurate way is to connect two or four tensor resistors in the Wheatstone bridge circuit, which allows you to measure the voltage change on the diagonal of the bridge. The bridge circuit has a high sensitivity and can compensate for the effect of temperature if the tensor resistors have the same coefficient of temperature dependence of the resistance. An algorithm for measuring the deformations of a metal pipe working under compression using strain gauges has been developed.

Material Characterization Based on a Comparative Analysis of Various Metals Elongations

Abstract: In this work, characterization procedures for examining materials and environmental factors are implemented utilizing strain gauges and DHT11 sensors. Stress-strain and fatigue analysis was made possible by the use of strain gauges to monitor the deformation and strain in various materials. By using the DHT11 sensors to detect temperature and humidity, environmental conditions might be analyzed. The sensor measurements were recorded and interpreted using data logging and visualization tools, and the noise and signal were improved using signal processing techniques. Correlation analysis was also performed to look into connections between the measured variables. The application showed the ability to learn important lessons about how things behave under pressure and in different environments.

Experimental evaluation of the size and distribution of lateral pressure on the walls of the excavation support

The paper presents the results of a research experiment that aimed at verifying the size and distribution of earth pressure acting on the excavation support with reference to commonly used theoretical solutions. The tests were carried out on the object in its full scale. For this purpose, a 6 m deep excavation was made in the testing ground. It was secured with a support system i.e., a point chamber consisting of corner columns and a system of three rows of fin plates. The tests relied on various measurement techniques. The earth pressure was measured with sensors specially designed and manufactured for this research experiment. Simultaneously with earth pressure measurements, there were measured stresses in the support plates with the use of strain gauges and deflections using laser scanning and a calibrated measurement patch. The tests were conducted for three months, with different backfill load. The measured values of earth pressure increased in a manner similar to the values of hydrostatic thrust, reaching max. 30 kPa before making the excavation and 25 kPa after making the excavation and assembling the support. The results were consistent with the values determined in line with commonly used theoretical solutions. The stresses caused a 15 mm deflection in the plates. Backfill load significantly affected the value of thrust down to a depth of approx. 4 m but did not cause a further increase in the deflection in the plates.

Use of sun gear orbits to obtain the load sharing in planetary transmissions and its impact in the tooth load

The present work assesses the possibility of using the orbits described by the sun gear in order to analyse the load sharing ratio in planetary gear transmissions. Furthermore, the current work is extended to observe the impact of the floatability and different tangential pinhole position errors in the load borne in a single contact between a pair of teeth in comparison to the load per planet. Therefore, it highlights the inaccuracy of the load sharing ratio (LSR) as an indicator of the overload in one tooth of the planet. Moreover, the use of the orbits represented with respect to a rotating reference provides helpful information to determine the overloads and underloads in the planets due to the existence of a tangential error in sequentially phased transmissions. Therefore, this proposal provides a simpler solution to the measurement of the LSR in planetary transmissions with different numbers of planets than the use of strain gauges.

Numerical evaluation of the accuracy in the load sharing calculation using strain gauges: Sun and ring gear tooth root

This work aims to extend the understanding in the use of strain gauges in the root of the teeth in order to calculate the load sharing in planetary transmissions. Continuing with the numerical analysis of the accuracy of the experimental measurements, this work studies the influence of the placing of strain gauges in the accuracy of the measurements. Thus, the strain gauges are placed in the ring and sun gears. Furthermore, new effects are added to the simulations in order to enhance its realism. Hence, the stiffness in the sun support is varied, as well as the number of planets is raised. Finally, the results show discrepancies between the real load sharing and the measured load sharing, more importantly, these differences prove that the measurements underestimate the load sharing in the transmission, which could be crucial in the durability and certification of such a transmission.

Дослідження умов раціонального комплектування орних машинно-тракторних агрегатів

Goal. To improve the operational and technological parameters of the plowing machine-tractor unit by determining the conditions of the rational combination of constructive parameters of the plow and the aggregating tractor. Methods. Theoretical research was carried out based on using the basics of theoretical mechanics and the theory of agricultural machinery. Experimental studies of plowing units to the determination of their traction and operational-technological indicators were performed with the use of strain gauges and other special mechatronic equipment. Results. The use of an arable machine-tractor unit as a part of the KhTZ-170 wheeled aggregate tractor and a 5-body plow attached to the rear, adjusted according to the developed methodology, allowed to increase its productivity by 13.4% while reducing specific fuel consumption by 15.2%. Conclusions. The research made it possible to propose a method of adjusting the plow machine-tractor unit, which involves a combination of design parameters of the plow and tractor to ensure the most rational placement of the «center of bearing part» and the point of attachment of the first relative to the longitudinal axis of symmetry of the second. According to the results of field experimental studies, it was found that the application of the developed method of aggregation of wheeled power tools with plow implements based on KhTZ-170 tractor with 16.9R38 tires and 5-body plow PLN-5-35 compared to similar machine tractor unit with standard 23.1R26 tires allowed to increase productivity by 4% with reducing the specific fuel consumption by 15.2%.

Data-driven farm-wide fatigue estimation on jacket-foundation OWTs for multiple SHM setups

Abstract. The sustained development over the past decades of the offshore wind industry has seen older wind farms beginning to reach their design lifetime. This has led to a greater interest in wind turbine fatigue, the remaining useful lifetime and lifetime extensions. In an attempt to quantify the progression of fatigue life for offshore wind turbines, also referred to as a fatigue assessment, structural health monitoring (SHM) appears as a valuable contribution. Accurate information from a SHM system can enable informed decisions regarding lifetime extensions. Unfortunately direct measurement of fatigue loads typically revolves around the use of strain gauges, and the installation of strain gauges on all turbines of a given farm is generally not considered economically feasible. However, when we consider that great numbers of data, such as supervisory control and data acquisition (SCADA) and accelerometer data (of cheaper installation than strain gauges), are already being captured, these data might be used to circumvent the lack of direct measurements. It is then highly relevant to know what is the minimal sensor instrumentation required for a proper fatigue assessment. In order to determine this minimal instrumentation, a data-driven methodology is developed for real-world jacket-foundation offshore wind turbines (OWTs). In the current study the availability of high-frequency SCADA (1 Hz) and acceleration data (>1 Hz) as well as regular 10 min SCADA is taken as the starting point. Along these measured values, the current work also investigates the inclusion of an estimate of the quasi-static thrust load using the 1 s SCADA using an artificial neural network (ANN). After data collection all data are transformed to features on a 10 min interval (feature generation). When considering all possible variations a total of 430 features was obtained. To reduce the dimensionality of the problem this work performs a comparative analysis of feature selection algorithms. The features selected by each method are compared and related to the sensors to decide on the most cost-effective instrumentation of the OWT. The variables chosen by the best-performing feature selection algorithm then serve as the input for a second ANN, which estimates the tower fore–aft (FA) bending moment damage equivalent loads (DELs), a valuable metric closely related to fatigue. This approach can then be understood as a two-tier model: the first tier concerns itself with engineering and processing 10 min features, which will serve as an input for the second tier that estimates the DELs. It is this two-tier methodology that is used to assess the performance of eight realistic instrumentation setups (ranging from 10 min SCADA to 1 s SCADA, thrust load and dedicated tower SHM accelerometers). Amongst other findings, it was seen that accelerations are essential for the model's generalization. The best-performing instrumentation setup is looked at in greater depth, with validation results of the tower FA DEL ANN model showing an accuracy of around 1 % (MAE) for the training turbine and below 3 % for other turbines, with a slight underprediction of fatigue rates. Finally, the ANN DEL estimation model – based on two intermediate instrumentation setups (combinations of 1 s SCADA, thrust load, low quality accelerations) – is employed in a farm-wide setting, and the probable causes for outlier behaviour are investigated.

Diagnosing Extrusion Process Based on Displacement Signal and Simple Decision Tree Classifier.

The article presents an extensive analysis of the literature related to the diagnosis of the extrusion process and proposes a new, unique method. This method is based on the observation of the punch displacement signal in relation to the die, and then approximation of this signal using a polynomial. It is difficult to find in the literature even an attempt to solve the problem of diagnosing the extrusion process by means of a simple distance measurement. The dominant feature is the use of strain gauges, force sensors or even accelerometers. However, the authors managed to use the displacement signal, and it was considered a key element of the method presented in the article. The aim of the authors was to propose an effective method, simple to implement and not requiring high computing power, with the possibility of acting and making decisions in real time. At the input of the classifier, authors provided the determined polynomial coefficients and the SSE (Sum of Squared Errors) value. Based on the SSE values only, the decision tree algorithm performed anomaly detection with an accuracy of 98.36%. With regard to the duration of the experiment (single extrusion process), the decision was made after 0.44 s, which is on average 26.7% of the extrusion experiment duration. The article describes in detail the method and the results achieved.

Optimisation of a mobile device frame structure – practical aspects

This paper presents a strength analysis of a steel container frame fastened to a Jelcz 8x8 chassis with four ISO 1161 corners. As part of the work, optimisation of the structure was performed using the numerical finite element method (FEM) and experimental tests with the use of strain gauges. The results of simulations and tests are summarised in appropriate tables and in the form of the distribution of stress contour lines using the Huber-Mises hypothesis.

PU tensile tests: conventional and digital image correlation analysis.

Polyurethane (PU) is a polymer, used as coating, paint, foam, adhesive, and even in biomedical devices. To furthermore expand its applications, it can be combined with additives such as Calcium Carbonate (CaCO3), an inexpensive material, widely available in nature, or with fibers, such as glass fibers explored in several sectors, likewise the aerospace and automobile industries. To determine the mechanical properties of these materials, the tensile test is the most used due to its great ease of application and flexibility. However, conventional processes, such as the use of strain gauges or crosshead displacement data, may not provide detailed information about the strain field, or cannot be able to evaluate the Poisson’s ratio and the true stresses for the entire stress-strain curve. Thus, digital image correlation (DIC) methods are a promising alternative, consisting of strain field measurement without contact with the surface of the structure. In this context, this study carried out the tensile characterization of two main polyurethane samples: one petrochemical, distributed by Sika®, reinforced with type E glass fiber: and the other, natural, manufactured by Kehl® from castor oils, and combined with CaCO3 particles. During the tests, DIC was applied to evaluate the Poisson’s ratio and, subsequently, Scanning Electron Microscopy (SEM) analyses were performed, revealing a higher number of bubbles on Sika’s polymer, which contributes to the reduction of the maximum supported stresses, since these pores, with dimensions of up to 25 µm, were regions where the cracks started and headed the breakage. Poisson’s ratios were all around 0.4 and the highest tensile strength values were obtained from E-glass reinforced samples (TS015), around 117.24 ± 13.20MPa. CaCO3 particles also acted as reinforced, increasing maximum stress reached from 20MPa to values between 29 and 37MPa.

A Design Concept and Kinematic Model for a Soft Aquatic Robot with Complex Bio-mimicking Motion

Fish mortality assessments for turbine passages are currently performed by live-animal testing with up to a hundred thousand fish per year in Germany. A propelled sensor device could act as a fish surrogate. In this context, the study presented here investigates the state of the art via a thorough literature review on propulsion systems for aquatic robots. An evaluation of propulsion performance, weight, size and complexity of the motion achievable allows for the selection of an optimal concept for such a fish mimicking device carrying the sensors. In the second step, the design of a bioinspired soft robotic fish driven by an unconventional drive system is described. It is based on piezoceramic actuators, which allow for motion with five degrees of freedom (DOF) and the creation of complex bio-mimicking body motions. A kinematic model for the motion’s characteristics is developed, to achieve accurate position feedback with the use of strain gauges. Optical measurements validate the complex deformation of the body and deliver the basis for the calibration of the kinematic model. Finally, it can be shown, that the calibrated model presented allows the tracking of the deformation of the entire body with an accuracy of 0.1 mm.

Ratcheting Examination of 1045 Notched Steel Plates under Low-High and High-Low Sequences

Abstract The present study examines the ratcheting response of 1045 notched steel plates undergoing uniaxial step-loading cycles. Loading steps were applied with different Low-High and High-Low sequences. Ratcheting tests were conducted on notched samples, and average local strains were measured with the use of strain gauges mounted in the vicinity of notch roots. Measured ratcheting strains near notch roots were found as high as 10 times those of tests conducted on unnotched samples. The magnitude of applied cyclic load as well as notch diameter influenced local ratcheting strain at the vicinity of the notch root. The lower nominal load level over the first step in the Low-High sequence substantially promoted ratcheting magnitude over subsequent loading steps with higher load magnitudes. In the High-Low loading sequence, the previous load step with higher magnitude retarded the local accumulated plastic strain of the subsequent step with a lower load level. The plastic zone at the notch root was affected over the loading steps. Microhardness tests were conducted at several positions within a small area of 1.5 by 4 mm near the notch root to map the plastic zone and its progress after each loading step. Microhardness data collected at the notch region verified an enlarged plastic zone over the Low-High loading sequence, while the plastic zone for the High-Low loading sequence was estimated about 50 % smaller in size. Cracking at the notch root and fracture surface taken within the plastic zone were examined through optical and scanning electron microscopies.