Strain Gauge Method Research Articles

Influence of uphill quenching on residual stresses and properties of alloy D16

The paper presents the results of the heat treatment influence, including quenching in water, uphill quenching (cooling of the alloy in liquid nitrogen, holding in it and heating in hot mineral oil) and also natural or artificial aging on the properties of a deformable aluminum alloy D16 (2024). With the help of hole-drilling strain-gage method, the influence of heat treatment on residual stresses was determined. The recommendations concerning the usage of this heat treatment to reduce residual stresses and warpage are given. The influence of uphill quenching on mechanical and corrosion properties are determined.

Effect of aspect ratio and end plates on rotational oscillations of thick plates in air flow

The steady oscillations of elastically fixed thick plates in the air flow are considered. The oscillation amplitudes are measured using the strain gauge method. In experiments, the aspect ratio varies. Some of the experiments were performed with end plates. Steady-state oscillation amplitude increases with an increase in plate aspect ratio. In the presence of end plates, the oscillation amplitude linearly depends on the Strouhal number. Increasing the aspect ratio of the thick plate from 5 to 7 does not lead to a significant change in the amplitude of oscillations.

Effect of Heat Treatments on Residual Stress and Properties of AISI 316L Steel Processed by Directed Energy Deposition

AISI 316L stainless steel samples were produced by means of laser powder-directed energy deposition using optimized building conditions with two different deposition strategies. The samples, in the as-built state, were at first characterized in terms of microstructure, hardness and residual stresses by the incremental hole-drilling strain-gauge method. The results highlighted that the deposition strategy mainly affects the residual stress values, while the material hardness value is not strongly varied. The distribution of the residual stresses along the sample height was also evaluated by measuring the stress at different distances from the building platform. Furthermore, some samples underwent a homogenizing heat treatment for 2 h at 600 and 800 °C and were characterized and compared with the as-built ones. The results showed that the suggested heat treatments allow not only a reduction in residual stresses but also the homogenization of the microstructure confirmed by comparing the variations of the Vickers hardness values along the building direction. Tensile tests were also performed on the as-built and heat-treated samples in order to investigate the effect of the heat treatment on the tensile properties of the material.

The origin of large magnetostrictive properties of rare earth doped Fe-Ga as-cast alloys

Rare earth doping could greatly enhance the magnetostrictive properties of Fe-Ga as-cast alloys. But the origin of this large magnetostrictive property has always been controversial. Some researchers think that this large magnetostrictive property is induced by the distortion of A2 lattice. While others think this is sourced from the formation of (001) oriented textures. In order to solve this controversy, the microstructure and magnetic properties of La, Pr, Sm and Y doped Fe-Ga as-cast alloys were examined by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), electron backscattered diffraction (EBSD), vibrating sample magnetometer (VSM) and strain gauge method in this paper. And the results show that the reason for the increase of the magnetostrictive properties of Fe-Ga cast alloys caused by rare earth doping is closely related to whether the rare earth elements enter the A2 crystal lattice. When the rare earth elements cannot enter into the A2 lattice of the alloy sample, the cause of the large magnetostriction is mainly attributed to the (001)-oriented columnar crystals. However, when rare earth elements can enter into the A2 crystal lattice of the alloy sample, the cause of large magnetostriction is mainly due to residual stress, or distortion caused by rare earth elements entering into the A2 crystal lattice, and secondly by the (001)-oriented columnar crystals.

Magnetic and magnetoelastic properties of rare earth intermetallides based on TbFe2

The paper presents the results of the study of magnetic and magnetostrictive properties of rare-earth intermetallides based on TbFe2 compound: Tb1-xZrxFe2, Tb1–xSmxFe2 and (Tb1–xYx)0.8Sm0.2Fe2. These alloys have a cubic crystal structure of the Laves phase C15 throughout the substitution region. For the system of alloys Tb1–xZrxFe2 the single-phase area is limited to the replacement parameter 0 < x < 0.2 and 0.8 < x < 1.0. The compounds of the Tb1–xSmxFe2 system were studied via X-ray dilatometry. The magnetostriction of alloys within the Tb1–xZrxFe2 and (Tb1–xYx)0.8Sm0.2Fe2 systems was studied in the temperature range of 80-320 K in magnetic fields of up to 17 kOe via a strain-gauge method. It was found that each system has the phenomenon of sign inversion of magnetostriction constants: in the system Tb1–xZrxFe2 in the area of replacement parameter x = 0.8, in Tb1–xSmxFe2 - in the area x = 0.45, and in the system of alloys (Tb1–xYx)08Sm02Fe2 at x = 0.6. It was demonstrated that magnetic compensation and spin reorientation phenomena occur in these systems. The obtained results are discussed in the model of alloys with competing exchange interactions.

Flexible Pr‐Doped Fe–Ga Composite Materials: Preparation, Microstructure, and Magnetostrictive Properties

Herein, the manufacture process and the results of investigations into the microstructure and magnetic properties of flexible Fe83Ga17Prx (x = 0, 0.2, 1.0) composite materials are presented. The Fe83Ga17Prx (x = 0, 0.2, 1.0) alloy powders with particle size of 75 μm and epoxy binder are bonded at a weight ratio of 2:1, and then orient under a constant applied magnetic field of 10 kOe and airdry 12 h, finally processed into composite material. The microstructure and magnetic properties of as‐cast alloy, unoriented (UN), and oriented (OR) composite materials are examined by X‐ray diffractometer (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM/EDS), vibrating sample magnetometer (VSM), and strain gauge method. The results show that the Pr‐doped Fe–Ga as‐cast samples consist of A2 matrix phase and rare‐earth‐rich phase. As the Pr content increases, the grain sizes of A2 matrix phase decrease. The OR composite materials show significant magnetic anisotropy. Compared with as‐cast and UN composite materials, the magnetostriction of OR composite materials increase. The highest value of magnetostriction (310 ppm) is obtained in the flexible Fe83Ga17Pr1.0 composite material.

Residual Stress Analysis of a 2219 Aluminum Alloy Ring Using the Indentation Strain-Gauge Method

Aerospace thin-walled rings are vulnerable to machining distortion during the manufacturing process. Various research results show that the main factor causing machining deformation is initial residual stress inside the blank. In this study, the residual stress of a 2219 aluminum alloy ultra-large rolling ring was measured by using the indentation strain-gauge method. Results showed the maximum residual maximum principal stress was +265 MPa and stress distribution was uneven. To homogenize the initial residual stress of the ring, an expansion method is proposed based on the principle of pre-stretching plate, and the feasibility of the expansion method was analyzed by establishing a simplified theoretical model of ring. A FE (Finite Element) model was established to investigate residual-stress evolution during the rolling ring and the expanding ring process. The expansion simulation results show that the reduction rates of residual stress were greater than 40% and the maximum residual stress was only 65 MPa.

Studies of internal stress induced by solidification of menthol melt as temporary consolidant in archaeological excavations using resistance strain gauge method

Volatile organic solids, such as cyclododecane or menthol, have been employed as temporary reinforcement material during archaeological excavations. They are usually applied as melts and reinforcement is achieved once the melts solidify. Such solidification process can induce internal stress on the artifacts, which can be a big concern, especially to those very precious and fragile ones. However, information about such stress is still extremely limited at present. This paper proposes an experimental method based on resistance strain gauge technique to monitor the deformation induced by solidification of menthol melt. Bending tests are performed on very thin glass slides. The solidification process of menthol melt is well characterized by the development of mechanical strains. Then, menthol melts are applied to three kinds of simulated samples, i.e. glass, sandstone and rice paper, to investigate the mechanical response of preserved bodies upon solidification. It is found that menthol melt will generate certain amount expansion or contraction of the objects upon solidification. The stresses induced, evaluated according to obtained strains, are generally quite small, indicating that application of menthol as reinforcement material is safe in mechanics for cultural relics.

Investigation of the compressive behavior and failure modes of unconfined and FRP-confined concrete using digital image correlation

This paper presents a detailed study on the development of axial, lateral and Von Mises strains measured by contact and non-contact methods under axial compression fiber reinforced polymer (FRP) confined and unconfined concrete specimens. The focus of the study was on the correlation between macro responses and localized deformations and the effects of FRP confinement on the localization of deformations. A total of 10 specimens were experimentally tested with a range of instrumentation to measure different types of strain. Digital image correlation (DIC) was used to obtain full-field strain evolution during compressive loading of concrete specimens confined with various fiber reinforced polymers. The effect of confinement material on the compressive behavior and strain distribution of FRP-confined concrete was investigated. The evolution of axial, lateral and Von Mises strains were recorded and examined during axial loading, including post-peak strain softening behavior. Data recorded by the typical contact method of linear variable displacement transformers (LVDTs) and strain gauges were used to validate the non-contact DIC method. The results obtained from DIC data in this study showed that expansion of shear zone for unconfined concrete is more localized than FRP-confined specimens. The results also show that specimens confined with CFRP induced homogenous compressive behavior, whereas GFRP and BFRP specimens with lower lateral stiffness displayed local strain concentration and less homogenous response. It was also observed that DIC provides a more accurate estimation of the ultimate condition compared to the contact methods due to the ability of DIC to capture the evolution of full-field strains.

Influence of Impact Velocity on the Residual Stress, Tensile Strength, and Structural Properties of an Explosively Welded Composite Plate.

This study aimed to analyze the effect of the impact velocity of a Zr 700 flyer plate explosively welded to a Ti Gr. 1/P265GH bimetallic composite on the residual stress formation, structural properties, and tensile strength. The residual stresses were determined by the orbital hole-drilling strain-gauge method in a surface layer of Zr 700 in as-received and as-welded conditions. The analysis of the tensile test results based on a force parallel to interfaces was used to propose a model for predicting the yield force of composite plates. Compressive residual stresses found in the initial state of the Zr 700 plate were transformed to tensile stresses on the surface layer of the welded Zr 700 plate. A higher impact velocity resulted in higher tensile stresses in the Zr 700 surface layer. To increase the resistance of the composite plate to stress-based corrosion cracking, a lower value of impact velocity is recommended in the welding process.

Polymerization Stress and Gap Formation of Self-adhesive, Bulk-fill and Flowable Composite Resins.

Bulk-fill materials show a similar or better performance than control flowable materials regarding interfacial integrity. However, some self-adhesive composites need improvements to achieve competitive performance. Objective: This laboratory study compared the polymerization stress and gap formation of self-adhesive, bulk-fill and control flowable composites. The degree of conversion (DC) and post-gel shrinkage were also assessed.Methods: Two self-adhesive (Vertise Flow and Fusio Liquid Dentin), two bulk-fill (Tetric N-Flow Bulk-Fill and Filtek Bulk-Fill Flowable Restorative), and two control flowable (Z350 XT Flowable Restorative and Tetric N-Flow) composites were evaluated. Polymerization stress (PS) was determined in a universal testing machine (n=5). Gap formation was evaluated by scanning electron microscopy in class I restorations (n=6). DC was measured by Fourier transform infrared spectroscopy (n=3). Post-gel volumetric shrinkage (VS) was measured using the strain gauge method (n=5). Data were submitted to one-way analysis of variance or a Kruskal-Wallis test (α=0.05).Results: Vertise Flow and Fusio Liquid Dentin presented the highest interfacial gap (27%±5% and 21%±6%, respectively), which was associated with their highest PS (4.1±0.8 MPa and 3.5±0.6 MPa, respectively) and DC (63%±2% and 60%±2%, respectively) in spite of the lowest VS (1.0%±0.2% and 1.0%±0.3%, respectively). Tetric N-Flow Bulk-Fill and Filtek Bulk-Fill Flowable Restorative presented similar PS (2.9± 0.3 MPa and 2.4±0.2 MPa, respectively) to both control materials. However, the Tetric N-Flow Bulk-Fill showed the lowest gap (7%±2%) and the highest DC (64.3%±0.4%), and the Filtek Bulk-fill presented a marginal gap (17.8%±3.4%) and a DC (54.5%±2.7%) similar to the control materials. The VS values of both bulk-fill materials were similar to those of Tetric N-Flow and lower than that of Z350 XT Flowable Restorative.Conclusions: Bulk-fill composites showed either similar or significantly lower interfacial gaps and PS than the control flowable composites. The self-adhesive composites showed a significantly higher gap percentage and PS than the control and bulk-fill materials.

FAILURE MODE ANALYSIS FOR TENSILE S-GLASS FABRIC HEXPLY USING STRAIN GAUGE METHOD

This paper presents an experimental results of S-Glass fabric prepreg composite material to determine tensile strength of S-Glass fabric prepreg coupons along warp and weft direction at room temperature environment using strain gauge method. A coupon is a small sample of the material under test that has been prepared in such a way that the failure mechanism will be representative of the larger production.

Influence of Cryogenic Treatment and Thermal Shock on Quenching Stresses and Properties of Alloy D16

This paper presents the results of heat treatment influence, including quenching in water, cooling of the alloy in liquid nitrogen, holding in it and thermal shock (heating in hot mineral oil) and also natural or artificial aging on the properties of wrought aluminum alloy D16 (2024). With the help of the hole-drilling strain-gage method the influence of heat treatment on residual stresses was determined and using tensile and indentation tests – specific elongation, reduction of area, yield strength, tensile strength and cracking resistance of alloy D16 (2024) were determined. Corrosion properties were studied with potentiodynamic method in 3% aqueous NaCl solution

Experimental research on the dynamic propagation process of mode I cracks in the rock under directional fracture blasting using the strain gauge method

Based on the directional fracture blasting experiment of polymethyl methacrylate (PMMA) specimens and combined with an analysis of the strain field around the dynamic crack tip, a strain gauge method with a specific acute (obtuse) orientation is proposed to record the dynamic fracture process of mode I cracks. A time evolution of the strain of the whole test process is employed to establish a binomial expression to represent the crack tip position and surrounding strain field and calculate the crack propagation velocity (CPV) and dynamic stress intensity factor (DSIF). Compared with the dynamic caustics method, the feasibility of the strain gauge method is analyzed. The strain gauge method is employed to research the dynamic fracture process of mode I cracks in rock directional fracture blasting. The results show that when the normalized strain value is 0 in the acute orientation or the maximum in the obtuse orientation, the position of the propagating crack tip is directly below the strain gauge. The calculations of the CPV and DSIF are consistent with those of the dynamic caustics method, which verifies the feasibility of the strain gauge method. The acute orientation has a large error dispersion. Compared with the dynamic caustics method, the strain gauge method can approximately record the whole process of rock crack propagation, reveal the evolution law of the CPV and DSIF and provide an experimental basis for research on the directional fracture process of nontransparent materials. Compared with the PMMA specimens, the rock specimens have a larger oscillation of the CPV and a smaller oscillation of the DSIF.

Assessment of non-uniform residual stress field of the thermal sprayed stainless steel coatings on aluminium substrates by the integral hole drilling method

Thermal spray is one of the most used techniques to produce coatings on structural materials. Such coatings are used as protection against high temperatures, corrosion, erosion and wear. The combined action of high pressures, temperatures and spraying conditions give rise to non-uniform residual stresses. The latter plays an important role in coating design and process parameters optimization. The present work highlights the influence of coatings thickness on the evolution of residual stresses in layered materials. Therefore, thick stainless steel coatings (ASTM 301) of different thicknesses are manufactured by wire arc spraying on aluminium alloy substrates (ASTM 2017A). For a better bond strength, a Ni–Al bond coat is first deposited. Furthermore, a numerically supported hole drilling strain gage method for residual stress field evaluation is proposed. Required calibration coefficients, for the strain–stress transformation formalism based on the integral method, are computed through finite element calculations using Abaqus software. The results indicate that the maximum residual stresses, for all thicknesses, are tensile and range from 140 to 275 MPa. The bond coat does not seem to affect the stress field. Also, it was found that the mean equivalent Von-Mises stress decreases with increasing coating thickness; hence reducing the interfacial adhesion energy of the sprayed materials.

Experimental analysis of corrugated fibreboard cutting with movable cutting disc during large-sized package manufacture

ABSTRACT The paper reports experimental research of loads (torques) that arise during cutting of corrugated fibreboard specimens by a movable cutting disc and immovable counter blades. The paper shows a method of corrugated fibreboard cutting based on the use of immovable counter blades and the cutting disc with reciprocating motion driven by electric engine. There has been designed and created experimental test bench for the research of corrugated fibreboard specimen cutting. The authors have used the strain gauge method for torque research that made possible to get their trustworthy values. The paper shows experimental research results that define technological parameters of corrugated fibreboard cutting by movable cutting disc, which minimise loads on main shaft. Results of experimental research give opportunity to get trustworthy and systematised information about torque values depending on type and thickness of the corrugated fibreboard and the influence of flute direction, cutting disc movement velocity and overlap size of tool during corrugated fibreboard cutting. The use of movable cutting disc in technological equipment for corrugated fibreboard cutting creates preconditions for high-quality manufacturing of large-sized packages from corrugated fibreboard, decreases overall dimensions and simplifies equipment design, minimises power discharge and packages manufacturing time.

Global-local deformation measurement of stress concentration structures using a multi-digital image correlation system

The digital image correlation (DIC) technique is a method of measuring the displacement and strain of the entire area of a structure by comparing surface images taken by digital cameras before and after deformation of the structure. The DIC technique is currently being spotlighted because it can overcome the weakness of conventional contact measurement methods. So far a single DIC system with one camera or two cameras has been used for most applications. However, many structures need two or more DIC systems in order to measure their deformation efficiently and precisely. For example, the stress concentration problem and the cylindrical shell buckling problem are typical applications for a multi-DIC system. This study focuses on the stress concentration problem. The paper presents a globallocal deformation measurement method with a multi-DIC system. First, a tensile test of an aluminum beam was performed and compared with the strain gage method to validate the accuracy of DIC method. Then the tensile test specimens with a hole or a notch were prepared, and one DIC system measured the local deformation near a hole or a notch and the other DIC system measured the global deformation of the specimen. The results confirmed the proposed multi-DIC technique can be applied to the stress concentration problem.

Numerical Simulation and Measurement of Welding Residual Stresses in Orthotropic Steel Decks Stiffened with U-Shaped Ribs

This study aims to investigate the magnitude and distribution of welding residual stresses in orthotropic steel decks stiffened with U-shaped ribs. Numerical simulation of the welding residual stresses is performed using the thermal elastic–plastic finite element method. The residual stresses are subsequently measured using the hole-drilling strain-gage method. Based on the results of this study, it can be determined that: (1) The longitudinal welding residual stresses (σz) in the weld zones are tensile stresses, where the peak value exceeds the minimum yield strength (fyl); however, relatively low compressive stresses exist in the areas located far away from the welds; (2) The stress gradient in the weld zone is steep, and the widths of the areas experiencing tensile stress are narrow; (3) In the case of the upper surface of the deck, the weld that is first deposited has the highest peak stress, while similar stresses are determined for the remaining welds. In the case of the lower surface of the deck, the peak stress in the weld zones is greater than that on the upper surface; (4) In the case of the weld zone of the U-shaped ribs, the tensile stresses reach up to 1.15fyl; however, at locations a short distance away from the welds, the σz varies from tensile to compressive, and finally transforms into a small tensile stress at the base of the U-shaped ribs. In addition, the simulated and measured σz are compared, and the deviation between them is analyzed.

The impact of deformation in the zone of welded joints on the force action of the rolling stock on the track

The causes of deformation in the zone of welded joints are considered. Authors experimentally studied changes in hardness on the rolling surface of the rail in the longitudinal and transverse profiles within the thermally affected zone of the welded joint. It is established that the hardness of the rolling surface of the rail in the longitudinal direction in the thermally affected zone of the joint is uneven and is determined by the structures arising from the effects of the thermal cycles of welding and the quality of the local heat treatment. In this case, two "low spots" are clearly traced with a decrease in hardness to 290...300 HB and with a higher hardness up to 350 HB right in the welded joint. Experimentally investigated the change in the depth of the welded joint from the implemented tonnage. At the same time with strain gauge method, using the force method developed by N. N. Kudryavtsev, continuous changes in vertical forces when the wheels move along the welded joint zone were recorded. Average values of vertical forces from loaded cars were established. Experimental distributions of vertical forces were approximated by theoretical laws according to the Kolmogorov — Smirnov matching criterion. Recommendations are given on minimizing the harmful impact of rolling stock on the track in areas of lowering welded joints.The following conclusions were made.1. Geometry of the joint irregularity is in the form of a W-shaped deformation with an influx of metal on the receiving rail and lowering on the directing rail. The width of the upper part of the deformation varies between 160...200 mm along the axis of the rail.2. Deformation zone of the welded joint is a source of increased dynamic impact from the wheels of the rolling stock on the elements of the upper track structure. According to the results of experimental studies it was found that the greatest increase in dynamic effects was observed from locomotive wheels up to 45.. . 70 kN, maximum values reached 180...210 kN, from the wheels of loaded freight cars the values of vertical forces increased by 35.. .45 kN, maximum values reached 145...170 kN, from the wheels of empty cars increase dynamic impacts amounted to 14...16 kN, maximum values reached 32...36 kN.

Effects of Positions and Angulations of Titanium Dental Implants in Biomechanical Performances in the All-on-Four Treatment: 3D Numerical and Strain Gauge Methods

In finite element (FE) simulations, the peak bone stresses were higher when loading with a cantilever extension (CE) than when loading without a CE by 33–49% in the cortical bone. In the in vitro experiments, the highest values of principal strain were all within the range of the minimum principal strain, and those peak bone strains were 40–58% greater when loading with a CE than when loading without a CE (p &lt; 0.001). This study investigated how varying the implanted position and angulation of anterior implants in the All-on-Four treatment influenced the biomechanical environment in the alveolar bone around the dental implants. Ten numerical simulations of FE models and three in vitro samples of All-on-Four treatment of dental implants were created to investigate the effects of altering the implanted position and angulation type of anterior implants. A single load of 100 N was applied in the molar region in the presence or absence of a CE of the denture. The 3D FE simulations analyzed the von-Mises stresses in the surrounding cortical bone and trabecular bone. For the in vitro tests, the principal bone strains were recorded by rosette strain gauges and statistically evaluated using the Mann–Whitney U test and the Kruskal–Wallis test. Loading in the presence of a CE of the denture induced the highest bone stress and strain, which were 53–97% greater in the FE simulation and 68–140% in the in vitro experiments (p &lt; 0.008) than when loading without a CE. The bone stresses in the FE models of various implanted positions and angulation types of anterior implants were similar to those in the model of a typical All-on-Four treatment. In vitro tests revealed that the bone strains were significantly higher in the samples with various angulation types of anterior implants (p &lt; 0.008). In the All-on-Four treatment of dental implants, the bone stress and strain were higher when the load was applied to the CE of dentures. Altering the position or angulation of the anterior dental implant in the All-on-Four treatment has no benefit in relieving the stress and strain of the bone around the dental implant.