Digital Micrometer Research Articles

Dynamic Screw Lead Accuracy Measurement: Research on the Compensation of the Workpiece Placed Away from the Ideal Position.

The screw, a critical element in a variety of transmission mechanisms, significantly influences the performance of the transmission process. Accurate measurement of screw lead is crucial for ensuring the quality of transmission equipment. However, the measurement process can be affected by the precision limits of the measuring instruments and the challenges of manual fine adjustments. This can lead to the screw being misplaced, introducing errors due to the off-center positioning of the workpiece. Such errors can hinder the achievement of high-precision measurements. This research aims to reduce the time needed to adjust for workpiece misalignment and to improve the accuracy of screw lead measurement through error compensation. This study starts by examining two specific scenarios that can cause workpiece misalignment in screw lead accuracy measurements: the tilting of the workpiece and the misalignment of the workpiece axis relative to the circular grating axis. Then, a mathematical model to quantify this misalignment and measure the associated parameters is developed. Based on the measured parameters, a computational model is established to compensate for the bias error under these conditions. This method allows for efficient and precise measurement of the screw lead even when the workpiece is not perfectly aligned. Calibrated screws and a digital micrometer are used to conduct experiments on workpiece misalignment. By comparing measurements with and without error compensation, the effectiveness of the compensation method in enhancing measurement accuracy is demonstrated.

Biomechanical and Physical Characteristics of Dental Dam Sheets Used for Absolute Isolation.

This study aimed to evaluate the mechanical and physical properties of dental dam sheets used for absolute isolation and to correlate the mechanical parameters with cost. Twenty-one dental dam sheets were tested: ALLPRIME; Madeitex; Sanctuary non-latex, Sanctuary latex black, green, and blue; Nic Tone blue and black; Mk Life; Elastidam; Bassi; Pribanic; Care; OK; MDCDental; Keystone; Dura Dam; Flexidam; Sanctuary blue; Nic Tone blue; Ehros; and USE. The thicknesses of the dental dam sheets were measured using a digital micrometer (Mitutoyo). The dental dam sheets (n=15) were prepared by cutting the samples with dimensions of 80 × 10 mm with a 1.7 mm hole made at the center of each specimen, following the ISO 9001 standard. The specimens were tested using a universal testing machine (Emic) at a speed of 500 mm/min until rupture to calculate rupture force (RF, N), elongation (%), and ultimate tensile strength (UTS, MPa), their thickness (mm) was measured using a digital micrometer, and scanning electron microscopy and X-ray energy dispersive spectroscopy were performed to analyze the structure and composition. The radiopacity was measured using digital radiography. Thickness, UTS, RF, and elongation data were analyzed by one-way ANOVA and Tukey's test (α=0.05). The Flexidam dental dam had the largest thickness (0.5 mm), while Nic Tone had a median thickness of 0.3 mm; the RF value (41.3 N) was higher for the thicker dental dams. The other dental dams had RF values ranging from 19 to 30 N. The highest elongation was obtained for the non-latex Sanctuary dental dam (600 mm). The Bassi dental dam had the highest UTS value (15 MPa), and medium and small particles were observed in most of the gums. A loss of continuity was detected in the structure of Sanctuary green and blue media. The predominant elements in the sheets were carbon, magnesium, sulfur, silicon, and calcium. The UTS, RF, and elongation varied substantially, indicating insufficient standardization of dental dam sheets. Nonetheless, most of the tested dental dams exhibited mechanical and physical properties suitable for clinical use. The correlation between the cost and mechanical properties of the dental dams was very low.

Influence of Coating Material Thickness on the Attraction Force of Dental Magnetic Attachment: An In Vitro Study.

This study aimed to determine the influence of coating material thickness on the attraction force of dental magnetic attachment (DMA). An in vitro experimental design was implemented using DMA as samples coated with different material types including polytetrafluoroethylene (PTFE) and glass ionomer varnish. DMA consists of keeper and assembly. The coating material was applied to DMA in two ways, on the assembly only and both the keeper and assembly. The thickness of each coated DMA was measured with a digital micrometer, and analysis was subsequently conducted with a universal testing machine to evaluate potential alterations in magnetic attraction force. Comparison was made between the attraction force of both the coated and uncoated DMA serving as a control specimen. The thickness of the coating material applied to both the keeper and assembly was 25 μm, while PTFE and varnish coating on the assembly alone was estimated as 12 and 10 μm, respectively. The magnetic attraction force of the uncoated DMA was 613.63 gf. Following coating, the magnetic attraction force decreased by 34.02-79.45 gf. The ANOVA test indicated that the decrease in magnetic attraction observed across both types of coating material and technique did not show significant differences. The thickness and type of coating material had no significant effect on magnetic attraction.

Evaluation of the in vitro performance of the double forwarder knot, compared to square and surgeon's knots using large gauge suture.

The aim of the study was to evaluate the strength and size of the double forwarder (DF) knot in 2 and 3 USP polyglactin 910 when used to form a ligature and to compare the knot holding capacity (KHC), size and weight of the DF knot to surgeon's (SU) and square (SQ) knots with varying numbers of throws. Laboratory study. Knotted suture. Knots were tied using 2 and 3 USP polyglactin 910 and tested on a universal testing machine under linear tension. Mode of failure and (KHC) were recorded. Knot volume and weight were determined by digital micrometer and balance. KHC, size, and weight between knot type, number of throws, and suture type and size were compared using ANOVA testing, with p < .05 as significant. In both suture types, DF knots had a higher KHC than SQ/SU knots (p < .004), with the exception of SU knots with 6-8 throws in 3 USP polyglactin 910 (p > .42). All DF knots failed by suture breakage at the knot, as did all SQ/SU knots with >6 throws. DF knots in 2 and 3 USP polyglactin 910 were larger and heavier than SQ and SU knots when the same number of throws was applied (p < .003). Self-locking DF knots provided increased strength compared to SU/SQ in large gauge suture but only when fewer than six throws are applied to SU/SQ knots. The new DF knot could be an alternative for a secure ligature.

Cuspal Deflection and Marginal Integrity of Class II Cavities Restored with Bulk-fill Resin Composites

Objective: This laboratory study aims to assess the cuspal deflection, adaptation, and marginal sealing of premolars restored with bulk-fill resin composites. Methods: Fourty-four premolars received class II preparations (distal and mesial boxes located 1 mm above and 1 mm below the cementoenamel junction, respectively). The teeth were distributed into four groups according to the resin composite used for restoration (n=11): G1 (control): Filtek Z250 XT; G2: Filtek Bulk-Fill; G3: Tetric N-Ceram Bulk-Fill; G4: Aura Bulk-Fill. A digital micrometer was used to measure the cuspal deflection before and after the restorative procedures. Replicas in epoxy resin of the restored teeth were achieved before and after thermal cycles. The cervical margins were observed by SEM at 200x magnification to obtain the percentage of continuous margins (%CM). After thermal cycles, the samples were immersed in a silver nitrate solution, and the microleakage was analyzed in the cervical margins. Results: ANOVA showed no significant differences in the cuspal deflection and %CM among the resin composites. Student’s t-test showed a significant decrease in the %CM after thermal cycles for all resin composites at the cervical margin in dentin. There was higher microleakage at the dentin margin for all the resin composites. Conclusion: Bulk-fill resin composites had comparable behavior to a conventional composite in regard to the cuspal deflection, adaptation, and marginal sealing parameters.

Cuspal Deflection and Marginal Integrity of Class II Cavities Restored with Bulk-fill Resin Composites

Objective: This laboratory study aims to assess the cuspal deflection, adaptation, and marginal sealing of premolars restored with bulk-fill resin composites. Methods: Fourty-four premolars received class II preparations (distal and mesial boxes located 1 mm above and 1 mm below the cementoenamel junction, respectively). The teeth were distributed into four groups according to the resin composite used for restoration (n=11): G1 (control): Filtek Z250 XT; G2: Filtek Bulk-Fill; G3: Tetric N-Ceram Bulk-Fill; G4: Aura Bulk-Fill. A digital micrometer was used to measure the cuspal deflection before and after the restorative procedures. Replicas in epoxy resin of the restored teeth were achieved before and after thermal cycles. The cervical margins were observed by SEM at 200x magnification to obtain the percentage of continuous margins (%CM). After thermal cycles, the samples were immersed in a silver nitrate solution, and the microleakage was analyzed in the cervical margins. Results: ANOVA showed no significant differences in the cuspal deflection and %CM among the resin composites. Student’s t-test showed a significant decrease in the %CM after thermal cycles for all resin composites at the cervical margin in dentin. There was higher microleakage at the dentin margin for all the resin composites. Conclusion: Bulk-fill resin composites had comparable behavior to conventional composites in regard to the cuspal deflection, adaptation, and marginal sealing parameters.

Precision Analysis of Chain Wheel Geometry Reconstruction Based on Contact and Optical Measurement Data

This study focuses on the detailed reconstruction of chain wheel geometry utilizing measurement data gathered from the MarSurfXC20 contact system and the iNEXIVE VMA 2520 optical system. Supplementary data were also gathered from a digital micrometer and a caliper to provide a comprehensive data set for the analyzed geometry. The geometric model of the chain wheel was then constructed using Siemens NX software. The reconstructed model was subsequently compared with the original design specifications to assess the fidelity of the reconstructed model. Results demonstrate a high degree of correlation between the model generated by reverse engineering and the original design model. Despite the satisfactory correlation, potential inaccuracies were identified, necessitating further research to mitigate these discrepancies and optimize the procedures for parameters beyond the established tolerance. The study affirms the feasibility of utilizing contact and optical measuring systems in the reverse engineering process of chain wheel geometry, although it underscores the need for additional refinement to improve the model's accuracy.

Comparative study on traditional and new etchants for radon monitoring using Poly(allyl diglycol carbonate) (PADC) and identification of (Na3H(CO3)2.2H2O) in etched products

A comparative study is conducted on Traditional Etchants (NaOH/H2O, KOH/H2O) and New Etchants viz. NaOH/Methanol, NaOH/Ethanol and NaOH/1-propanol for Poly(allyl diglycol carbonate) (PADC) used in Radon monitoring. Molar concentration of traditional etchants NaOH/H2O and KOH/H2O is varied from 1 M to 6 M and etching temperature is varied from 30 °C to 80 °C to verify optimal etching parameter. Etching is done for 8 to 9.5 h in the steps of 30 min. An average bulk etch rate (Vb) of 1.4μm/h and 1.7μm/h for NaOH/H2O and KOH/H2O is calculated respectively under optimal etching conditions. Optimal reported concentrations of 1.5 M, 1.5 M and 1 M respectively, are used to make standard NaOH/Methanol, NaOH/Ethanol and NaOH/1-propanol solutions. Track densities, track diameters, bulk etch rate (Vb), track etch rate (Vt), etching time, variation in mass and thickness for both traditional and new etchants are calculated and compared. Traditional etchants take much longer time (5 to 7 h) for etching with initial swelling due to absorption of etchant on the surface of detector due to broken molecular chains, causing increase in mass and thickness of detectors for initial 0.5 to 1 h of etching which are measured with digital balance (±0.0001 g) and digital micrometer (±0.001 mm) respectively. New etchants take short time for etching (30 min approx.). There is no initial increase in mass and thickness of detectors due to short etching time and high Vb of new etchant. Traditional etchants give high track densities with low Vb and Vt while new etchants gives low track density with high Vb and Vt. New tracks formation is rare in new etchants as compared to traditional etchants. An average radon concentration level of 21.8 kBqm−3 is calculated from detectors etched in traditional etchants while new etchants do not provide any useful information about radon track density to calculate radon concentration for the given samples. Trona i-e Na3H(CO3)2.2H2O is identified as a common product formed in the etched products of PADC etched in either of the etchants i.e. traditional etchants and new etchants, using X-ray powder diffraction (XRPD) analysis.

Automated Camera Lucida Method with Colored Images through Integration of Hardware and Software in Microscopic Zooming.

Automating the camera Lucida method which is a standard way for focusing microscopic images is a very challenging study for many scientists. Hence, actually combining hardware and software to automate microscopic imaging systems is one of the most important issues in the field of medicine as well. This idea reduces scanning time and increases the accuracy of user's results in this field. Closed-loop control system has been designed and implemented in the hardware part to move the stage in predefined limits of 15°. This system produces 50 consecutive images from parasites at the mentioned spatial distances in two directions of the z-axis. Then, by introducing our proposed relational software with combining images, a high-contrast image can be presented. This colored image is focused on many subparts of the sample even with different ruggedness. After implementing the closed-loop controller, stages movement was repeated eight times with an average step displacement of 20 μm which were measured in two directions of the z-axis by a digital micrometer. On average, the movement's error was 1 μm. In software, the edge intensity energy index has been calculated for image quality evaluation. The standard camera Lucida method has been simulated with acceptable results based on experts' opinions and also mean squared error parameters. Mechanical movement in stage has an accuracy of about 95% which will meet the expectations of laboratory user. Although output-focused colored images from our combining software can be replaced by the traditional fully accepted Camera Lucida method.

Changes in Hair Coat Length and Diameter in Blanketed and Non-Blanketed Adult Horses in the Winter.

Horses are often blanketed during cold weather for numerous reasons including assisting thermoregulation, cleanliness, and anecdotally to decrease hair coat length. However, the impact of blanketing on the hair coat has yet to be evaluated. The objective of this study was to evaluate changes in hair coat length and diameter over time in blanketed and non-blanketed horses during winter. In October 2019, 16 mature adult horses were blocked by breed and BCS and randomly assigned to a blanketed (n=8) or non-blanketed (n=8) treatment; blankets were placed. Data was collected between October 2019 and March 2020 in River Falls, WI. During this time BW, BCS, and hair coat samples were taken monthly. Twenty hair coat samples were taken from the non-mane side of the neck and the hindquarters using a tweezers and measured for the length and diameter using a digital micrometer and caliper, respectively. The average measurement was used to analyze the data. Horse neck and hindquarter hair were the longest and had the greatest diameter in January and February and they were the shortest with the smallest diameter in October and March regardless of treatment (P ≤ 0 .05). Blanketed horses had shorter neck hair length when compared to non-blanketed horses in January at 43 and 58 mm, respectively, and February at 35 and 47 mm, respectively (P ≤ 0 .05). These results suggest blanketing a horse can alter hair coat length, however, hair coat growth over time follows a similar pattern regardless of blanketing practices.

Justification of the use of wear-out digital micrometer in repair production

Issues related to the evaluation of the results of direct multiple measurements with a worn digital micrometer have considered. It had determined that the total error of the device used in operation exceeds the limit of permissible error indicated in the passport by 1.25 times and is equal to 5 μm. But in the field of control of parts in repair production, the passage of mandatory verification by measuring instruments is not required, and the calibration operation is advisory in nature. Based on the obtained value, we can conclude that the device can be used to measure the dimensions of parts with a tolerance of at least 15 µm.

Preparation, Characterization, and Application of Modified Starch/Chitosan/Sweet Orange Oil Microcapsules

Aquatic products have an important role in global agriculture, but the challenges associated with preservation have limited their marketability. Essential oil (EO), such as sweet orange oil (SOEO), has been widely used for preservation due to its excellent antibacterial ability. However, the volatilization of EO limits its application in food preservation. In this study, SOEO was extracted from sweet orange peel by steam distillation and then stored in microcapsules. The components of the microcapsules were as follows: the porous starch was chosen as an adsorbed substrate to store SOEO (PS/SOEO), and sodium alginate (SA) and chitosan (CMCS) were used as shell material to delay the volatilization of SOEO using the sharp pore coagulation method. Our results showed that the main antibacterial ingredients in SOEO were aldehydes (33.93%) and d-limonene (15.38%). The microcapsules were of an irregular shape (oval), and the size of the microcapsules was 1.2 0.1 cm as measured by a digital micrometer. Scanning electron microscopy (SEM) results showed that there were a lot of pores on the surface of the starch after modification, but sodium alginate and chitosan could well encapsulate these pores. The results of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis also showed that SOEO was successful encapsulated into the porous starch. The results of compression test and releasing kinetics studies suggested that CMCS and SA improved the mechanical and slow-releasing ability of SOEO microcapsules. The best antibacterial performance was obtained when 0.8 g of SOEO microcapsules was added. Finally, the shelf life of crawfish could be extended to 6 days by SOEO microcapsule (1/10 g, SOEO microcapsule/crawfish) under room temperature. These results provide a systematic understanding of the antibacterial capabilities of sweet orange essential oil microcapsules, which can contribute to the development of preservation methods for aquatic products.

Synthesis and Characterization of Biocomposite Films of Methylcellulose-Based with Nanocellulose

This study explores the development of nontoxic biocomposite films from methylcellulose (MC) and crystalline nanocellulose (CNC). First, a methylcellulose sample (Tylose MH 50) of concentration 1.5% (w/w) and crystalline nanocellulose type-1 samples of different concentrations were prepared to obtain these biocomposite films. Films were then produced by adjusting methylcellulose solution with nanocellulose solution following the casting-evaporation methodology. The molecular interactions of crystalline nanocellulose with methylcellulose were investigated using ATR Fourier Transform Infrared (FTIR) spectroscopy. FTIR analysis of films revealed a shift of absorption peak in the region of 3200-3600 cm-1 to a lower value and found an intense peak at 1031 cm-1 with the incorporation of CNC into Tylose MH 50 film. The thermal stability of these films was examined using thermogravimetric analysis (TGA), indicating the films' higher stability than MC. Mechanical properties were measured by controlled RH by dynamic mechanical analysis (DMA), showing changes in Young's modulus from the initial slope of stress-strain plots and storage modulus (E′) as the concentration of CNC increased in films. The data were obtained from bionanocomposite films, which were not even with variations in thickness as measured by a digital micrometer. The mechanical properties of bionanocomposite films showed variation due to the varying local orientation of CNCs in MC, as it contradicts work that was previously done in this area which suggests a uniform orientation of CNCs in MC biopolymer. Further research on these biocomposite films is expected to find more significant uses.

The Relationship between Process Capability and Quality of Measurement System

This article deals with the design of appropriate measures that had to be taken for the implemented measurement system. The measurement result was significantly negatively affected by several factors. Forty-five samples of shafts used in the production of surgical drills were measured. Measurements were performed by metrological appraisers with a calibrated digital micrometer. Measurement and subsequent data processing revealed low process capability (CP and PP indices). A large portion of the shafts had an observed size below the lower specific limit (LSL). Therefore, it was necessary to take corrective action. This paper focuses on the corrective measures implemented in the measurement system. The micrometer met the requirements of the standard and was metrologically capable. The shafts were measured by eight metrological appraisers, so attention was focused on the potential impact of the metrological appraiser. The measured data were evaluated by uncertainty analysis, paired t-tests, measurement systems analysis (MSA) and Cohen’s kappa. The number of non-compliant shafts was shown to increase with decreasing measurement capability. The measurement system was evaluated as conditionally capable, even incapable. One possibility was to identify the optimal pair of metrological appraisers. The pair of metrological appraisers E and F appeared to be the most suitable combination for most methods. Due to the relatively high %EV index, the second option was to improve the work with the measuring instrument, that is, improve the training and supervision of metrological appraisers in the measurement process. Repeated measurements by the pair with the highest capability (metrological appraisers E and F) resulted in an increase in the value of the capability indices and a decrease in the number of shafts out of tolerance for the same shafts. As the value of these indices was lower than 1.33 during repeated measurements, corrective measures had to be taken, not only in the measurement system, but also in the production system.

Anatomical variations of the liver and its suspensory system: a cadaver‐based study

Introduction &amp; ObjectiveNon‐traumatic musculoskeletal (MSK) pain has become a socio‐economic burden, being the leading cause of absenteeism and prolonged disability. Despite all medical advances, the origin of this pain is still unclear. Studies have reported theories on the role of fascia, nociceptive stimulation, and visceral (im)mobility, and provided evidence for the success of visceral manipulation therapy. The influence of viscera on the MSK system is neglected in scientific research, even though the human body functions best when its components, including the viscera, are free to move in full range. Thus, to understand the role of visceral mobility on the MSK system, this study aimed to investigate the anatomical variation of the liver’s suspensory system via physical measurements and 3D surface scanning. It is hypothesized that anatomical variations will exist.Materials &amp; MethodsWith IRB clearance, fourteen of twenty‐two formaldehyde‐fixed donors were selected for this study; the other eight donors excluded due to pathology affecting the region of interest. Using gross dissection, livers and diaphragms were isolated. Using a string and a digital micrometer, the length and thickness of the triangular ligaments, the falciform ligament, and the circumference of the bare area was measured for each selected donor. Each isolated liver was weighed. Using a structured light scanner, each liver and suspensory system (bare area and aforementioned ligaments) were digitalized for future analysis.ResultsThe mean lengths (mm) of the left triangular ligament edges were 55.70 ± 27.1, 88.38 ± 31.69, and 63.62 ± 28.76. The mean lengths (mm) of the right triangular ligament edges were 35.32 ± 21.15, 46.98 ± 51.83, and 33.28 ± 21.83. The mean lengths (mm) of the falciform edges were 102.75 ± 30.40, 172.32 ± 35.70, and 105.51 ± 49.25. The mean thicknesses (mm) of the left and right triangular ligaments, and the falciform, were 0.32 ± 0.16, 0.32 ± 0.20, and 0.34 ± 0.31, respectively. The bare area circumference was 443.12 ± 98.38mm, and the mean liver weight was 1439.09 ± 752.39g.ConclusionThis dissection‐based study provides evidence of a broad range of anatomical variations that exists between livers and suspensory system, emphasizing the uniqueness of the human body’s anatomy.Significance/ImplicationThis was the first study to examine the morphological variation of the liver’s ligaments and bare area via meticulous physical measurements. The results suggest that the liver’s suspensory system has carefully adapted to each body’s needs and demands. Understanding and visualizing this could help train clinicians who provide visceral manipulation therapy to the liver for MSK pain. A patient’s specific liver morphology may differ greatly from standard anatomy textbook descriptions, so recognizing the anatomical variation of the liver’s suspensory system and the potential impact it has on the MSK system could lead to alternative and improved treatments. Further research could include statistical modeling from the 3D digitalized models. To understand the actual role of the liver’s suspensory system in influencing the MSK system, the biomechanical and proprioceptive properties of the ligaments should be researched.

Impact of different light curing modes on the cuspal deflection of maxillary premolars restored with nanohybrid resin restoration

INTRODUCTION: The influence of various light-curing modes may lead to polymerization shrinkage resulting in contraction stresses in composite resin. These stresses leads to linear movement of the cusp tips of the tooth as a result of interactions between polymerization shrinkage stress of the composite and adherence of the cavity wall of the tooth. That may lead to restoration failure. AIM: Comparative evaluation of the effect of different light-curing modes on the cuspal deflection of class II Mesio-occlusal-distal cavity restored with Nano-hybrid composite resin restorative material. METHOD: Thirty-six standardized MOD preparations were prepared on maxillary first premolars. Three groups(n=12) were divided according to different light-curing modes of Blue phase LED curing light- Group 1: soft-start curing mode; Group 2: pulse curing mode; Group 3: continuous curing mode. 1mm diameter glass beads were fixed to each cusp tip as a reference point for intercuspal distance to measure initial cuspal deflection for each group. MOD Preparations were etched and bonded with adhesive resin to provide micromechanical attachment and restored with Nano-hybrid composite restoration using the incremental technique. The cuspal deflection was then measured with the Digital micrometer gauge and the mean difference was measured for each group.

Dimensional Accuracy of 3D - Printed Acrylonitrile Butadiene Styrene: Effect of Size, Layer Thickness, and Infill Density

The adoption of Additive Manufacturing (AM) is continuously growing due to its capability to produce complex shapes which leads to the dependence of manufacturers on AM to replace conventional manufacturing processes. One important focus of research now is on the accuracy of 3D printed products produced via the Fused Deposition Modeling (FDM). These products have great potential to be applied to tooling and other rapid prototyping applications. The aim of this study is to assess the accuracy of 3D printed Acrylonitrile Butadiene Styrene (ABS) through manual measurements of dimensions. Several sets of samples with cubic shapes were printed and measured using a digital micrometer to evaluate the dimensional accuracy of the 3d-printed parts. A 22 full factorial design was employed to investigate the effects of infill density and layer thickness on the dimensional accuracy of ABS parts.

Comparative evaluation of dimensional stability and flexural strength of different light cured tray materials with self-cured tray material: an in-vitro study

Objectives: To carry out a comparative evaluation of dimensional stability and flexural strength of different light cured tray materials with self-cured tray material as control.Materials and methods: The study was carried out in four groups based on the different available tray materials. Group A (n=30) – light cured resin (Individo Lux-VOCO™ GmbH Germany); Group B (n=30)- light cured resin (Profibase-VOCO™ GmbH Germany); Group C (n=30)- light cured resin (Plaque Photo-Willmann and Pein™ GmbH Germany); Group D (n=30)- control group-self cured resin (Asian special instant tray material Asian Acrylates™, Mumbai, India). A digital micro-meter was used to measure the length of each specimen first at 1 hour, 24 hour and 48 hour and three readings were taken up to 0.001 decimal. The values for flexural strength of each specimen were measured using the 3-point bending technique with the help of a universal testing machine. The mean values of dimensional stability and flexural strength were calculated by the one-way ANOVA and Tukey’s post-hoc test for multiple group`s comparison.Results The mean change in length (in mm) of light cured resins samples were significantly lower than self-cured resin samples at all three time intervals. The flexural strength values of light cured resin samples-Group A (84.46±13.32 N/mm2), B (83.43±14.52 N/mm2) and C (86.80±14.73 N/mm2) was significantly higher than the self-cured resin samples group D (41.29±7.93 N/mm2)Conclusions: Light cured tray materials are more dimensionally stable and have a higher flexural strength compared to self-cured tray materials.

Monitoring of crack opening displacement of steel structure by PPP-BOTDA-distributed fiber optical sensors: Theory and experiment

Crack opening displacement (COD) is an essential parameter in fracture analysis of steel structures, and a novel methodology was developed for measurement of COD using high-resolution distributed fiber optical sensors. Based on crack-induced strain transfer mechanism, a theoretical model was firstly proposed to explicitly determine COD of steel element by strain singularity considering both the elastic and elastoplastic behavior of the optical fiber coating. The presented theoretical COD equations consider the inclination angle between the sensor axis and crack length as well. An experimental program of a pre-cracked pure bending steel element was then conducted to confirm the feasibility of the proposed monitoring approach. The PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) with 1-cm-level spatial resolution was used in distributed measurement of strain and determination of COD. Estimated CODs were also compared to those measured using traditional electronic digital display micrometer. The results indicate that the inclination effect of the optical fiber is slight on the COD within the inclination angle range of 30°. This proposed approach demonstrates great promise for high accuracy and sensitivity of COD monitoring applications.

Crack detection and retardation of steel structure by smart CFRP embedding PPP-BOTDA fiber sensors

Crack detection and retardation are essential issues in the CFRP reinforcement of damaged steel structures. A smart CFRP was developed for monitoring and retarding of crack opening displacement (COD) by embedding distributed fiber optical sensors which measure the strain singularity of externally bonded CFRP in the cracking zone. Based on crack-induced strain transfer mechanism in CFRP strengthening system, a theoretical model was then proposed to obtain an explicit COD expression considering both the elastic and elasto-plastic behavior of the adhesive. An experimental program of a pre-cracked pure bending steel element was also conducted to verify the proposed COD model. The distributed measurement of strain was conducted on CFRP by the commercial PPP-BOTDA (Pre-Pump-Pulse Brillouin optical time domain analysis) sensor with high spatial resolution. The comparison of theoretical CODs and the measured ones using EDDM (electronic digital display micrometer) confirms the ability of presented model on COD estimate. The proposed method using smart CFRP embedded with distributed optical fibers demonstrates great promise for high accuracy and sensitivity of COD monitoring, and has the capability of crack retardation and detection for the strengthened structures.