Maximum Load Values Research Articles

Development of new ηpl, β and limit load equations to evaluate fracture parameters of pre-cracked small punch test specimens

The small punch test (SPT) is an alternative method for determination of the mechanical properties when enough material is not available for conventional testing. Recently SPT specimen configuration is changed to have a crack (known as pre-cracked SPT) for more accurate determination of material fracture properties. Use of p-SPT specimens needs limit and maximum load values and geometric parameters, β and ηpl for evaluation of Stress Intensity Factor (SIF) and plastic J-integral respectively. However, general equations for these parameters are not available in the open literature. The present paper is an attempt to address this aspect of p-SPT specimens. Finite element analysis has been employed to evaluate the above parameters. Square pre-cracked specimens with crack parallel and perpendicular to the thickness direction are considered in this paper. The range of crack size a/W = 0.40–0.60 is considered for the present analysis. The load–displacement curves are extracted for both specimens using 3-D elastic–plastic FE analysis assuming elastic perfectly plastic material behaviour. Maximum load is directly obtained from the FEA load–deflection curves. The maximum load helps to assess the machine capacity to perform the SPT. Using the elastic–plastic J-integral and load–displacement data from FEA, ηpl values are calculated. Limit analysis using Plastic Work Curvature (PWC) criterion is carried out to obtain the limit loads. The geometric factor (β) is found out using elastic FE analysis for SIF calculation. Based on these FEA results, new equations have been proposed for limit load, maximum load, geometry factor (β) and ηpl for both types of p-SPT specimen configurations.

Synthesis and Tribological Performance of Different Particle-Sized Nickel-Ion-Exchanged α-Zirconium Phosphates

Nickel-ion-exchanged α-zirconium phosphate (Ni-α-ZrP) was synthesized by a mild hydrothermal synthesis method. Different raw material ratios (NaF/H3PO4/Ni(CH3COO)2·4H2O) influence the particle size of the Ni-α-ZrP samples. The grain size could be controlled and distributed from 20 to 600 nm. Ni-α-ZrP was evaluated as an additive in lithium grease in a four-ball test. A 3.0 wt.% addition of Ni-α-ZrP to lithium grease yielded maximum non-seizure load values of 1235 N, and the wear scar diameter on the lower balls is 0.42 mm at 294 N. Compared with smaller particles, the addition of Ni-α-ZrP with a larger particle size to grease yields a better load-carrying capacity.

Influence of Heat Treatments on the Fracture Toughness of 2017A Aluminium Alloy

The present study was carried out on 2017A aluminium alloy, in order to determine the influence of heat treatments on the fracture toughness determined by three point bending tests and empirical formula correlations used Charpy impact energy. The three point bending test has shown that the minimum values of fracture toughness and maximum load were found in the annealed state. Moreover, the hardening heat treatment increases them considerably, especially in the artificially aged condition of the alloy where it provided the maximum values. Schindler’s empirical formula gave the best estimation of fracture toughness in all metallurgical states of 2017A aluminium alloy.

Evaluation of Fracture Toughness of Red Mud Reinforced Aluminium Matrix Composite

Metal matrix composites are formed by combination of two or more materials (at least one of the materials is metal) having dissimilar characteristics. In the present investigation Red Mud Particle of average 90μm size was used as reinforcement and aluminum 8011 alloy was used as matrix material. Conventional stir casting method was employed to reinforce with the matrix. Metallographic studies carried out using optical microscope, reveal fair distribution of reinforcement in the matrix material. Prepared composite are then machined as per the ASTM standers to test Compact Tension (CT) and Single Edge Notched Bend specimen(SENB) . Fracture toughness values are the compared against the pure matrix aluminum and reinforcement weight percentage. For Compact tension specimen, the value of Maximum load (Pmax) increases by 35% at 12wt% red mud composite and gradually decreases at 16wt% compared to the base alloy, whereas the stress intensity factor K1c increases by 6% at 12wt% and decreases 16wt% of reinforcement. For Single Edge Notch Bend specimen, the value of Maximum load(Pmax) increases and stress intensity factor K1c increases with the weight percent of composite, the Maximum load id increased by 45% and stress intensity factor is increased by 11 % at 16wt% of reinforcement .

Impact Tensile Properties of Notched Titanium Alloy Bolt for Fairing Separation of Launch Vehicle

The payload fairing in Japan is fixed by a lot of notched bolts. These notched bolts were fractured by axial impact tensile using the explosive devices to separate the fairing. In this case, the stress waves and the oscillations propagate, which may seriously damage the satellites. In this study, the impact deformation and the fracture behavior of notched titanium alloy bolt was investigated using a split Hopkinson pressure bar method. The notched bolt specimen was made of commercial Ti-6Al-4V alloy. The maximum load value was increased with increasing the displacement rate. It can be said that the strain rate dependence of strength for Ti-6Al-4V alloy appeared. From the observation of fracture surface using a scanning electron microscope, compared with the quasi-static test, it was clear that the irregularities of the fractured surface at the impact tensile test became rough. Therefore, it was found that the brittle fracture was mainly observed due to the increase in displacement rate, which may mean that the mode of fracture changes from the transgranular to the intergranular. It was surmised that this change of fracture mode was caused by the high strain rate due to stress concentration of the notched part.

Analysis of Global Sensitivity of Landing Variables on Landing Loads and Extreme Values of the Loads in Carrier-Based Aircrafts

When a carrier-based aircraft is in arrested landing on deck, the impact loads on landing gears and airframe are closely related to landing states. The distribution and extreme values of the landing loads obtained during life-cycle analysis provide an important basis for buffering parameter design and fatigue design. In this paper, the effect of the multivariate distribution was studied based on military standards and guides. By establishment of a virtual prototype, the extended Fourier amplitude sensitivity test (EFAST) method is applied on sensitivity analysis of landing variables. The results show that sinking speed and rolling angle are the main influencing factors on the landing gear’s course load and vertical load; sinking speed, rolling angle, and yawing angle are the main influencing factors on the landing gear’s lateral load; and sinking speed is the main influencing factor on the barycenter overload. The extreme values of loads show that the typical condition design in the structural strength analysis is safe. The maximum difference value of the vertical load of the main landing gear is 12.0%. This research may provide some reference for structure design of landing gears and compilation of load spectrum for carrier-based aircrafts.

Studi Numerik Pengaruh Ukuran Penampang, Rasio Tulangan Lentur dan Jarak Tulangan Geser Terhadap Kekakuan Balok Beton Bertulang Menggunakan Program Respone 2000

One of the reinforced concrete beam behavior can be seen from the value of deflection, maximum load, and the relationship between moment with curvature and stiffness of the beam. Respone 2000 program is an approach program with numerical method that can be used to analyze the reinforced concrete beam. The results of this program include the value of deflection, maximum load, moment and curvature. This study aims to obtain numerical results in the form of stiffness of the beam, deflection value, maximum load, moment and curvature until the crack pattern occurs. This research was done by making 32 sample beam with variation of cross section of beam, flexural reinforcement ratio and shear reinforcement distance. The result of the analysis shows that the length of the span has a big effect on the deflection value, the maximum load and the stiffness but not the nominal moment. The results of the reinforcement ratio in this study greatly affect the deflection value, the masimum load, the nominal moment and the stiffness of the beam, while the shear reinforcement distance affects the beam behavior but only on some specimens.

Biomechanical Responses of Neonatal Brachial Plexus to Mechanical Stretch.

This study investigated the biomechanical responses of neonatal piglet brachial plexus (BP) segments—root/trunk, chord, and nerve at two different rates, 0.01 mm/second (quasistatic) and 10 mm/second (dynamic)—and compared their response to another peripheral nerve (tibial). Comparisons of mechanical responses at two different rates reported a significantly higher maximum load, maximum stress, and Young's modulus (E) values when subjected to dynamic rate. Among various BP segments, maximum stress was significantly higher in the nerve segments, followed by chord and then the root/trunk segments except no differences between chord and root/trunk segments at quasistatic rate. E values exhibited similar behavior except no differences between the chord and root/trunk segments at both rates and no differences between chord and nerve segments at quasistatic rate. No differences were observed in the strain values. When compared with the tibial nerve, only mechanical properties of BP nerves were similar to the tibial nerve. Mechanical stresses and E values reported in BP root/trunk and chord segments were significantly lower than tibial nerve at both rates. When comparing the failure pattern, at quasistatic rate, necking was observed at maximum load, before a complete rupture occurred. At dynamic rate, partial rupture at maximum load, followed by a full rupture, was observed. Occurrence of the rate-dependent failure phenomenon was highest in the root/trunk segments followed by chord and nerve segments. Differences in the maximum stress, E values, and failure pattern of BP segments confirm variability in their anatomical structure and warrant future histological studies to better understand their stretch responses.

Designing a epileptics patients services management model for Iranian health system

Aim: Epilepsy is increasingly developed worldwide, considered as one of the most important healthcare problems in the second half of 12th century. Methodology: This study is a quantitative-qualitative/cross sectional-practical method research. The conceptual model was derived from comparative studies of the United States, Australia, United Kingdom, Canada and the relevant experts' perspectives. The study population consisted of all professionals related to the healthcare management of epilepsy in all geographical regions of Iran. The obtained data were analyzed using software SPSS 16 and AMOS. Exploratory and confirmatory factor analysis were also performed, and the final model was obtained and its fitness was confirmed. Results: Nine factors were entirely identified for the final model of healthcare management of epileptic patients: Organizational structure of the leading policy, makers, methods of governmental interventions in financing resources, types of services necessary to provide patients, instances of epilepsy, monitoring, and controlling epilepsy healthcare services among which methods of governmental interventions in financing resources and monitoring and controlling epilepsy healthcare services had the minimum and maximum factor load value, respectively. Conclusion: As it can be observed from the study data, training and raising the public awareness toward epilepsy in the country is an essential tool to prevent these types of diseases, as identifying the initial main risks aiming at prohibition of epidemic diseases and also proper healthcare services in case of development are the most important initiations to be taken.

Determination the maximum load capacity of the welded structure of the transport carriage in operation

The article presents a calculation procedure for determining the maximum permissible load on the welded structure of the transport carriage. During the transport carriages operation inside the production hall there was no breakage of the welding joints. The use of carriages outside the hall and with an uneven surface began to create cracks and fractures in the weld joints. The values of vertical accelerations that were generated by running on uneven surfaces were determined by experimental measurement. To avoid cracks in welded joints, the maximum permissible load value of the transport carriage was subsequently determined by calculation using FEM.

Particular aspects of calculating affecting factors of fireballs emerging from aircraft crash

The article reveals an algorithm of calculating the heat loads which emerge during fireball-involving accidents. By way of illustration it considers a situation when a heavy aircraft crashes in the vicinity of a typical reactor building of a nuclear power plant. The given algorithm provides a quite detailed and accurate calculation of maximum heat load values that accompany the accident.

Fatigue behaviour of fibre-reinforced composite T-joints

In this paper a study was carried out on the fatigue life of fibre-reinforced composite T-joints subjected to a tensile pull-out loading. The composite T-joints have been made of glass fabric infused with epoxy resin using a vacuum assisted resin transfer moulding technique. Methods such as the use of veil layers, tufting techniques and 3D weave have been employed to improve the interlaminar fracture toughness of the composite T-joints. All the tests were conducted in an Instron testing machine using a specially designed test fixture. Fatigue tests were performed in a load control mode with a stress ratio of R = σmin/σmax = 0.1. The cyclic loading pattern was a sinusoidal wave with a frequency of 6 Hz. The specimens were cycled at a series of constant maximum load values up to failure. Fatigue loads versus life data for each T-joint type were produced at various maximum applied loads. The 3D weave T-joints were found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue life performance; the increasing rate in fatigue life is changed with the number of stress cycles. The location for the through-thickness reinforcement plays an important role in improving fatigue life of the Tjoints. Fatigue life is significantly improved if the web is reinforced in through-thickness direction. A finite element (FE) failure model was also created using ABAQUS to determine the location where delamination is initiated and its subsequent propagation.

Biomechanic and histologic analysis of fibroblastic effects of tendon-to-bone healing by transforming growth factor β1 (TGF-β1) in rotator cuff tears.

To evaluate the effect of transforming growth factor β1 (TGF-β1) on tendon-to-bone reconstruction of rotator cuff tears. Seventy-two rat supraspinatus tendons were transected and reconstructed in situ. At 8 and 16 weeks, specimens of three groups; that is control, L-dose (low dose), and H-dose (high dose) were harvested and underwent a biomechanical test to evaluate the maximum load and stiffness values. Histology sections of the tendon-to-bone interface were identified by hematoxylin-eosin or Masson trichrome stain. Collagen type III was observed by picric acid sirius red staining under polarized light. The level of insulin-like growth factor 1 (IGF-1) and vascular endothelial growth factor (VEGF) was measured by the enzyme-linked immunosorbent assay (ELISA) method. Collagen type III of the H-dose group had a significant difference in histology structure compared with the L-dose group (P<0.05). The maximum load and stiffness decreased significantly in the control group compared with the values of the L-dose and H-dose groups. The stiffness among the three groups differed significantly at the same postoperative time (P<0.05). Interestingly, progressive reestablishment of collagen type III affected tendon-to-bone healing significantly in the later stages. The H-dose was associated with an increased collagen type III morphology stimulated by TGF-β1.

Dynamic Simulation Research on Chain Drive Mechanism of Corn Seeder Based on ADAMS

In order to reduce the damage to the chain and improve the seeding quality of the seeding machine, the corn seeder has the characteristics of the seeding quality and some technical indexes in the work of the corn seeding machine. The dynamic analysis of the chain drive mechanism is carried out by using the dynamic virtual prototype. In this paper, the speed of the corn planter is 5km/h, and the speed of the simulated knuckle is 0.1~0.9s. The velocity is 0.12m/s, which is equal to the chain speed when the seeder is running normally. Of the dynamic simulation of the movement and the actual situation is basically consistent with the apparent speed of the drive wheel has changed the acceleration and additional dynamic load, the chain drive has a very serious damage, and the maximum load value of 47.28N, in order to reduce the damage to the chain, As far as possible so that the sowing machine in the work to maintain a reasonable uniform speed, to avoid a greater acceleration, the corn sowing machine drive the design of a certain reference.

Comparison of the effect of saturated and superheated steam on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes on cantaloupe and watermelon surfaces

The purpose of this study was evaluation of the effectiveness of superheated steam (SHS) on inactivation of foodborne pathogens on cantaloupes and watermelons. Saturated steam (SS) treatment was performed at 100 °C and that of SHS at 150 and 200 °C. Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes-inoculated cantaloupes and watermelons were exposed for a maximum of 30 s and 10 s, respectively. Populations of the three pathogens on cantaloupes and watermelons were reduced by more than 5 log after 200 °C steam treatment for 30 s and 10 s, respectively. After SHS treatment of cantaloupes and watermelons for each maximum treatment time, color and maximum load values were not significantly different from those of untreated controls. By using a noncontact 3D surface profiler, we found that surface characteristics, especially surface roughness, is the main reason for differences in microbial inactivation between cantaloupes and watermelons. The results of this study suggest that SHS treatment can be used as an antimicrobial intervention for cantaloupes and watermelons without inducing quality deterioration.

Biomechanical comparison of xenogeneic bone material treated with different methods.

Bone xenografting is considered one of the most effective ways to address the shortage of bone autografts and allografts. Various methods have been employed to minimize the immune rejection issues associated with bone xenografts. However, the side effects of such methods on bone biomechanical properties remain unclear. As such, the objective of this study was to compare the influence of different treatments on the biomechanical properties of porcine bones. Fresh pig ribs were cut into 1.5×0.5×0.4cm specimens, which were randomly divided into four groups and subjected to different modification regimes: group A by degreasing and partial deproteinization, group B by cryopreservation, group C by cryopreservation and enzyme digestion, and group D was a control group using fresh bone. Biomechanical tests and α-Gal antigen detection were performed for all groups. In the axial compression test, the values for maximum load were as follows: group D>group C>group B>group A. The maximum load in group A was significantly less than in the other groups (P<.05). There were no differences between groups D, C, and B in terms of the maximum stress and elastic modulus (P>.05). The maximum stress and elastic modulus values recorded for group A were significantly less than for the other groups (P<.05). There were no significant differences in the maximum load or elastic modulus among groups B, C, and D, in the three-point bending test (P>.05). However, the maximum load and elastic modulus values recorded for group A were significantly lower than the other groups (P<.05). In groups A and C, no α-Gal antigen-positive expression was detected. In group B, there was low level α-Gal antigen-positive expression, while a high level of α-Gal antigen-positive expression was observed in fresh bone samples. The results indicated that xenogeneic bone subjected to degreasing and partial deproteinization had the worst biomechanical properties. Cryopreservation and cryopreservation with enzyme digestion had little effect on the bone biomechanical properties, although enzyme digestion resulted in the complete elimination of the α-Gal antigen. Cryopreservation with enzyme digestion treatment presented the best results in terms of removing the immune-response triggering α-Gal antigen, while preserving the good biomechanical properties of bone xenografts.

Force Interaction of Technological Tool and Elastic-Plastic Link at Large Diameter Tubes Preliminary Forming

The sustainability of the manufacturing process and quality improvement of the longitudinal electric-welded large diameter tubes, produced from the U-shaped workpiece, is determined based on a science-based approach to the parameters selection and the preliminary press forming technological tool settings. For this purpose we developed a software system that allows interactively performing multiple calculations of the kinematics and press equipment energy-power characteristics in the interaction of mutually movable links of the supporting rocker mechanism with a punch through the forming workpiece, presented in the form of elastic-plastic link. As a result of the study of forming workpiece stress-strain state and the mechanism force analysis, dependence of the equipment maximum loads in function of the geometry, size and setting instrument parameters, the forming tube size and material is determined. Physical modelling of the press forming process was performed to analyze the influence of these factors on the maximum load value. The forces perceived oscillating rocker stand and videogram of the process were recorded during physical modelling. Experimental data matches with the results of the developed software calculation with a precision of 12%. An original modular tool with variable geometry is proposed. It is shown that the use of the two-radius punch construction allows to reduce the maximum loads magnitude during preliminary forming by 30% and, therefore, to reduce the load of the whole technological tool. In addition, the possibilities to receive U-shaped products with high precision and predetermined shape parameters are expanded.

Fracture load of complete-arch implant-supported prostheses reinforced with nylon-silica mesh: An in vitro study

Statement of problemComplete-arch implant-supported prostheses without a framework have a high risk of failure: a straightforward and inexpensive reinforcement material, such as nylon mesh, could improve their longevity. PurposeThe purpose of this in vitro study was to evaluate a nylon-silica mesh compound on the fracture strength of acrylic resin and the fracture load of complete-arch implant-supported prostheses. Material and methodsTwenty-four complete mandibular arch implant-supported prostheses were divided into 2 groups according to cantilever length (molar and premolar) and subdivided into another 2 subgroups according to the presence or absence of reinforcing mesh. The specimens were submitted to a maximum load-to-fracture test in a universal testing machine, with a 100-N load cell, a 2 mm/min crosshead speed, and a spherical metal tip diameter of 4 mm at different points (molar and premolar). These were submitted to 1-way analysis of variance for repeated measurement and the post hoc Tukey multiple comparison test (α=.05). ResultsThe mean maximum load ±standard deviation for the molar group was 393.4 ±95.0 N with reinforcement and 305.4 ±76.3 N without reinforcement (P=.02); and for the premolar group was 1083.3 ±283.7 N with reinforcement and 605.3 ±90.5 N without reinforcement (P=.001). ConclusionsReinforcement with nylon mesh increased the mean maximum load of implant-supported complete-arch prostheses at both cantilever lengths. The cantilever to the premolar (5 mm) presented the highest maximum load values to fracture.

FRACTURE RESISTANCE AND FAILURE MODE OF TWO RESTORATION DESIGNS MADE OF MONOLITHIC HYBRID AND GLASS MACHINABLE CERAMICS ; IN VITRO STUDY

Statement of the problem: Monolithic hybrid and glass ceramics are indicated for intracoronal and extracoronal ceramic restorations. Available data regarding selection of the appropriate ceramic type for each preparation design and its influence on fracture resistance of tooth restoration complex is still scarce.Purpose: The purpose of this study was to evaluate in vitro the fracture resistance and investigate failure mode of two restoration designs (crowns and inlays) made from lithium disilicate glass ceramic and hybrid ceramic constructed by the CAD /CAM technique.Materials and Methods: A total of twenty ceramic restorations restoring lower molars were designed and fabricated in this study. The restorations were divided into two groups; Group 1: Ten full coverage crowns and Group 2: Ten inlays. Each of the previous groups was further subdivided into two equal subgroups; Subgroup 1: Five restorations constructed from lithium disilicate glass ceramics (e.max CAD) and Subgroup 2: Five restorations constructed from hybrid ceramic (VITA ENAMIC) by the CAD/CAM technology. Two ivorine teeth were prepared following the guidelines for full coverage and inlay ceramic restorations, they were duplicated into stone dies followed by scanning, designing and milling of restorations. The stone dies were duplicated into epoxy dies where the restorations were adhesively cemented on them. All cemented samples were exposed to 2000 thermal cycles (5°C and 55°C in water) with a dwell time of 25 seconds in a computer controlled thermocycler. All specimens were loaded in a universal testing machine where fracture test was done by compressive mode of load applied occlusally using a metallic rod with round tip at cross-head speed of 1mm/min until fracture occurred. Fracture resistance values were recorded in Newtons then they were statistically evaluated and failure modes were analyzed. Results: For group 1 representing crown restorations, a statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.05) where the highest mean value of maximum load was found in (VITA ENAMIC) (951.77 N ± 81.05) and the lowest mean value of maximum load was found in (e.max CAD) (709.35 N± 49.51). While for the second group representing inlay restorations, no statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.307) where the highest mean value of maximum load was found in (e.max CAD) (627.71 N ± 80.01) and the lowest mean value of maximum load was found in (VITA ENAMIC) (581.26 N± 51.74). For the e.max CAD subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p=0.005) where the highest mean value of maximum load was found in the crown group (790.35 N± 49.51) and the lowest mean value of maximum load was found in the inlay group (627.71N ± 80.01).Regarding the VITA ENAMIC subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p<0.001) where the highest mean value of maximum load was found in the crown group (951.77 N ± 81.05) and the lowest mean value of maximum load was found in the inlay group (581.26N±51.74).Conclusions: 1. All inlays and crowns constructed from hybrid and glass ceramics in this study revealed fracture load values falling in the range of physiologic masticatory forces 2. When considering restoration of molars with full coverage crowns, VITA ENAMIC is more preferred than e.max CAD ceramic in terms of fracture resistance as it showed a higher statistical significant mean values.3. When planning to restore molars with minimally invasive intracoronal restorations, both ceramics can be used as there was insignificant statistical difference between them , however e.max CAD can be recommended due to its more favorable mode of fracture compared to VITA ENAMIC.4. Irrespective of preparation designs, both ceramics showed insignificant difference regarding fracture resistance mean values.

A Fatigue Fracture Study on TDCB Aluminum Foam Specimen of Type Mode III Bonded with Adhesive

AbstractThis paper studies the characteristics of junction structure of closed-cell type aluminum foam, which is generally used as a shock absorber. TDCB specimens were designed for mode III type with thickness as a variable and performed a fatigue experiment on them by thickness. As the result, the load value of all specimens peaks under 0 to 25 cycles and decreases as the cycles increase. As the specimen thickens by 10 mm, the maximum load value is 1.2 times. When the thickness increases by 20 mm, the maximum value increases by 1.5 times. This study result can be utilized by investigating the mechanical characteristics of TDCB specimens for mode III type under fatigue loading conditions systematically and efficiently.