Static Strength Tests Research Articles

Dynamic strength of laser brazed joints

Laser brazing of zinc coated steel is a well-established joining technology in the automotive industry. So far, only a few studies examined the influence of the processing parameters on the strength of these joints. Thus, the influence of different laser power adjustments on the joints’ properties is investigated. The joints are examined by the visual surface inspection, the analysis of micro-sections, quasi static tensile strength tests and dynamic bending tests. Additionally, the influence of the type of zinc coating is investigated for electrogalvanized (EG) and zinc-aluminum-magnesium (ZM) coated steel. At comparatively high laser power adjustments joints manufactured with EG coatings excel the performance of those made with ZM as joints with EG endure up to 94 % more load cycles than joints with ZM during dynamic tests.

Stress Analysis and Strength Test of 2500 Fracturing Truck Frame

For the fracturing trucks, which is an important member of oil and gas fracturing, the stress and strength of fracturing truck’s frame have a very significant influence on the continuous fracturing operation. This paper takes the frame of 2500 fracturing truck as the research object, analyses its stress condition, and conducts the static strength test and dynamic strength test of the whole frame of fracturing truck, respectively tests the strain of 15 measuring points of the frame under the fully loaded static condition and the right front wheel lifting condition, and finds out the distribution rule of the stress and strain of the frame. The results show that the maximum stress position of the frame under migration condition is at the root of the rear support of the tank, the total stress is 146.76 MPa, the minimum safety factor reaches 2.35, and the strength of measuring point meets the requirements.

Effect of Shot Peening on the Mechanical Properties and Cytotoxicity Behaviour of Titanium Implants Produced by 3D Printing Technology.

Structural discontinuities characterize the implants produced directly from metal powders in 3D printing technology. Mainly, the surface defects should be subjected to procedures associated with surface layer modification (likewise shot peening) resulting in the increase of the implant service life maintaining optimal biocompatibility. Therefore, the purpose of the present study was to investigate the effect of type of shot used for the peening process on the Ti-6Al-4V implants functional properties as well as the biological properties. The components were produced by DMLS (direct metal laser sintering) additive technology. The surfaces of titanium specimens have been subjected to the shot peening process by means of three different shots, i.e., CrNi steel shot, crushed nut shells, and ceramic balls shot. Then, the specimens have been subjected to profilometric analysis, microhardness tests, and static strength testing as well as to the assessment of biocompatibility in respect of cytotoxicity using human BJ fibroblasts. The shot peening process causes the strengthening of surface layer and the increase of strength parameters. Furthermore, the test results indicate good biocompatibility of surfaces being tested, and the effect of shot peening process on the titanium alloy cytotoxicity is acceptable. At the same time, most favourable behaviour in respect of cytotoxicity has been found in the case of surfaces modified by means of ceramic balls > nut shells > CrNi steel shot correspondingly.

성층권 장기체공 무인기 주익 구조 해석 및 건전성 평가

Recently, development of long endurance electric powered airplane has been conducted worldwidely. Light structural weight of a main wing with sufficient structural integrity is essential for long endurance flight. Since a main wing with a slender spar can occur catastrophic fracture under the flight, it is important to establish a design and verification method for both the weight reduction and structural integrity. In this paper, structural design and analysis of the main wing of HALE UAV with tubular spar reinforced with a bulkhead were introduced. The static strength test of the main wing was performed to verify structural integrity under the static load. Then, the experimental result was compared with an analytical result from a finite element analysis. It was concluded that the developed light weight main wing would have sufficient structural integrity under the flight operation.

Post- Impact Fatigue Damage Analysis of Quasi Isotropic CFRP Laminates through Infrared Thermography

Carbon fiber reinforced plastic (CFRP) materials used for lightweight aircraft structures are susceptible to low velocity accidental impacts during manufacture and while in service. In this study the CFRP laminates subjected to low velocity impact conditions of three different energy levels were tested under various fatigue loading conditions till it reached the failure state. The infrared thermography NDT technique was used for the damage analysis of these post-impact fatigue loaded CFRP specimens to understand the damage distribution across the specimen. The cooling response curves obtained from the active thermography of the post impact fatigue specimens under four different combinations (transmission or reflection mode with impacted or un-impacted surface facing camera) for each of the specimens were analyzed. The rate of cooling in the temperature response curves is different for each specimens subjected with various post impact-fatigue loading conditions and it seems to be correlated with the extent of post-impact fatigue damage present in each specimen quantified through X-ray CT image processing. The temperature rise observed in the passive thermography at the fiber/ply breakage during static strength tests were proportional to corresponding load drops and the non-homogeneous spread of damage at the onset of tensile failure was seen from the thermographs.

Аналіз методів подовження терміну служби вантажних вагонів

In the article the authors consider the most common methods of extending the service life of wagons, namely: control tests and methods of non-destructive testing. The task of control tests is an experimental verification of the conformity of the parameters of the strength of the design of the wagon to the requirements of normative documents. The control tests include: static vertical strength tests, dropping from wedges, typical collision strength tests. Performing non-destructive testing of properties and indicators of the object of control should not lead to its destruction or violation of the suitability of the object for use and operation. Methods of non-destructive testing are classified according to the following features: the nature of the interaction of physical fields or substances with the controlled object, primary informative indicators, methods of obtaining primary information. In the study of the technical condition of knots and parts of wagons, only 4 methods of non-destructive control are most widely used: visual, capillary, magnіtopowder, ultrasonic (ultrasonic thickness gauging). According to the results of the analysis in the article, one can highlight the disadvantages and advantages of control tests. The main advantage should include the possibility of distributing the results to a batch of wagons of one model and the year of construction, the main drawback - it is quite lengthy to conduct control tests (1-2 months) and decryption of the results (2-3 months). Having analyzed the methods of non-destructive testing, it has been shown that they enable to instantly determine the technical condition of the wagon and extend the service life or eliminate it from operation. The most effective and unpretentious non-destructive control method is MT because it, unlike the PT method, detects sub surface defects (up to 2 mm from the surface) and does not have the requirements for the surface roughness of the object of control, which in turn does not require the operator Conduct control of the definition of false defects.

Moisture Damage of Warm Mix Asphalt Concrete

Implementation of Warm Mix Asphalt concrete (WMA) is getting global acceptance due to the restrictions for protecting the environment and the requirements to reduce fuel consumption. In this investigation, two WMA mixtures have been prepared in the laboratory using medium curing cutback (MC-30) and Cationic emulsion asphalt. Hot Mix Asphalt (HMA) was also prepared for comparison. The cylinder specimens (63.5mm) in height and (101.6mm) in diameter were constructed from the mixtures and subjected to indirect tensile strength test to determine the Tensile Strength Ratio (TSR). The cylinder specimens of (101.6mm) in height and (101.6mm) in diameter were also constructed from those mixtures and subjected to static compressive strength test to determine the Index of Retained Strength (IRS). It was concluded that the WMA are more prone to moisture damage than HMA, the TSR are (92 and 86) % for (emulsion and cutback) WMA respectively, both are lower than of HMA by (2.13 and 8.51) % respectively. As the asphalt content increases, the TSR also increases and reached to peak value of Optimum Asphalt Content (OAC) then decreases. The WMA has less IRS than HMA, the IRS are 70% and 78% for the WMA-emulsified asphalt and HMA respectively.

An Investigation of the Structural Strength of Transtibial Sockets Fabricated Using Conventional Methods and Rapid Prototyping Techniques.

Rapid Prototyping is becoming an accessible manufacturing method but before clinical adoption can occur, the safety of treatments needs to be established. Previous studies have evaluated the static strength of traditional sockets using ultimate strength testing protocols outlined by the International Organization for Standardization (ISO). To carry out a pilot test in which 3D printed sockets will be compared to traditionally fabricated sockets, by applying a static ultimate strength test. 36 sockets were made from a mold of a transtibial socket shape,18 for cushion liners with a distal socket attachment block and 18 for locking liners with a distal 4-hole pattern. Of the 18 sockets, 6 were thermoplastic, 6 laminated composites & 6 3D printed Polylactic Acid. Sockets were aligned in standard bench alignment and placed in a testing jig that applied forces simulating individuals of different weight putting force through the socket both early and late in the stance phase. Ultimate strength tests were conducted in these conditions. If a setup passed the ultimate strength test, load was applied until failure. All sockets made for cushion liners passed the strength tests, however failure levels and methods varied. For early stance, thermoplastic sockets yielded, laminated sockets cracked posteriorly, and 3D printed socket broke circumferentially. For late stance, 2/3 of the sockets failed at the pylon. Sockets made for locking liners passed the ultimate strength tests early in stance phase, however, none of the sockets passed for forces late in stance phase, all broke around the lock mechanism. Thermoplastic, laminated and 3D printed sockets made for cushion liners passed the ultimate strength test protocol outlined by the ISO for forces applied statically in gait. This provides initial evidence that 3D printed sockets are statically safe to use on patients and quantifies the static strength of laminated and thermoplastic sockets. However, all set-ups of sockets made for locking liners failed at terminal stance. While further work is needed, this suggests that the distal reinforcement for thermoplastic, laminated and 3D printed sockets with distal cylindrical locks may need to be reconsidered.

Optimization of Prosthetic Knee Joint Under Static and Cyclic Strength Tests

Knee joint consists of different components, i.e. femur, tibia, patella and menisci which make it a complex structure, undergoing different critical loads in human body performing motions and physical activities. The present study focuses on the analysis of stress magnitude on knee joint and knee implant when these are introduced with different loads acting upon it with varying angles of inclination. 3-D model of the knee joint and knee implant were designed using 3-D modeling software i.e. CAD. These models were imported to ANSYS to get the specific results of stress magnitude using finite element analysis. This study has revealed that with a load range of 540N to 790 N and change in angle from 10° to 90°, the knee implant could be able to sustain a load of 540-640 N at an angle of 10°-50° demonstrating a stable stress value of 1.27E+08 – 6.11E+08 Pa. At steady state of the knee i.e. when the knee is at 90° position, stress value reaches to 1.28E+08 Pa.

Verification of FEM modelling of composite materials based on the results of static strength test

The article presents the verification of FEM modelling of composite materials based on the results of static strength test. The aim of the work was to examine whether the applied modelling of composite materials is correct and verify it with finite element method (FEM). The composite structure of the PW-6U glider was used as a model. In the program the numerical model (geometry and finite element mesh) of the glider’s wing was created. The wing is made of glass fabrics and a spar with flanges with a glass roving. The composite structure of the wing, including composition, layout and thickness of laminate layers, fiber arrangement was exactly modelled in the program and then subjected to loads. Having the measurements from the static strength tests of the glider, the numerical results were compared with the experimental results. Thanks to the applied modelling, the obtained numerical results were satisfactory and very close to the experimental results from the structural static tests of the glider. Therefore, it can be concluded that the conducted verification of FEM modelling of composite materials is correct. Nowadays application of composite materials is increasingly expanding. Therefore, the modelling of composites becomes a significant issue. FEM modeling allows verification of the structure. At the stage of modelling modifications can be implemented and thus time and costs associated with subsequent changes in the production process may be saved. This is a very good solution which already at the design stage of the structure allows examination of its strength.

Fracture strength of teeth with access cavity preparation with operating microscope or on buccal surfaces

Objective: The present study assessed the fracture strength of teeth subjected to endodontic access cavity preparation on buccal surfaces, or with the aid of operating microscopy when compared to the conventional technique. Material and methods: Sixty mandibular incisors were split into four groups (n=15): conventional access cavity preparation (CCP); conservative (C); buccal surface (BS); and control. The canals were prepared and filled and the cavities were restored. A static compressive strength test was conducted until crown fracture. The force data were compiled and assessed statistically. Kolmogorov-Smirnov and Shapiro-Wilk tests were performed to assess normality, Levene’s test to assess variance homogeneity, the one-way ANOVA to compare fracture strength in the assessed groups. Tukey’s HSD test was used to determine whether the differences in the means were significant between the groups.Results: The experimental groups did not show any statistically significant differences in mean fracture strength (CCP = 585.65 N±107.64 N)(BS = 530.52 N±129.35 N) (C = 517.83 N±114.68 N). Conclusion: Therefore, the selection of surface or size of access cavity proposed did not influence the fracture strength of mandibular incisors when compared to conventional cavity preparation. KeywordsDental pulp cavity; Dental stress analysis; Root canal therapy.

МІЦНІСНІ ДОСЛІДЖЕННЯ ЕЛЕМЕНТІВ КОНСТРУКЦІЇ БУНКЕРНОГО ВАГОНА

The article deals with the theoretical and experimental study of the strength of the structural elements of the hopper car covered for grain and other food cargoes. The results of experimental and theoretical studies of the stress-strain state of the hopper car frame by the finite element method (fem) are analyzed. Analysis of the results showed that the convergence of the results of theoretical and experimental studies is 84% – 87%, which is a satisfactory result and confirms the adequacy of the design scheme and the reliability of the possible results of calculations for other elements of the design of the hopper car. Experimental studies were performed by the tensometric method. Special attention was paid to the measurement of deformations in the pivot assembly as the most loaded element. Data processing of static strength tests was performed using automated complexes of experimental data processing using statistical methods. Despite the modernization and strengthening sordevolo node for hopper model 19-4152, the maximum voltage at that node 98,5% of the permissible normative values. This indicates that the pivot point remains one of the most stressed elements of the car and requires detailed study when performing further studies. The analysis of published literature sources shows that the problems associated with the strength of the hopper cars are relevant not only in Ukraine but also in the cis countries.

Mechanical strength analysis of lift steel landing doors based on statistical methods

The landing doors are quite important to the safety of the passengers during waiting and using lifts. In order to know the safety situation of the lift landing doors after China’s new regulations issued, the type test results of 647 landing door samples are summarized and analysed, including thickness analysis, static strength test analysis and impact test analysis. The result shows that the maximum elastic deformation can be fitted to have proportional relationship with the applied force, and the protrusion clearance into well after impact test of 89% doors are below half of the given limit in regulations.

Influence of testing parameters on the load-bearing capacity of prosthetic materials used for fixed dental prosthesis: A systematic review and meta-analysis

The aim of this study was to systematically review the literature to assess static fracture strength tests applied for FDPs and analyze the impact of periodontal ligament (PDL) simulation on the fracture strength. Original scientific papers published in MEDLINE (PubMed) database between 01/01/1981 and 01/06/2010 were included in this systematic review. Data were analyzed considering the test method (static loading), material type (metal-ceramic-MC, oxide all-ceramic-AC, fiber reinforced composite resin-FRC, composite resin-C), PDL (without or with) and restoration type (single crowns, 3-unit, 4-unit, inlay-retained and cantilever FDPs). The selection process resulted in the 72 studies. In total, 377 subgroups revealed results from static load-bearing capacity of different materials. Fourteen metal-ceramic, 190 AC, 121 FRC, 45 C resin groups were identified as subgroups. Slightly decreased results were observed with the presence of PDL for single crowns (without PDL=1117±215 N; with PDL=876±69 N), 3-unit FDPs (without PDL=791±116 N; with PDL=675±91 N) made of AC, 3-unit FDP (without PDL=1244±270 N; with PDL=930±76 N) and inlay-retained FDP (without PDL=848±104 N; with PDL=820±91 N) made of FRC and 4-unit FDPs (without PDL=548±26 N; with PDL=393±67 N) made of C. Overall, for single crowns, fracture strength of FRC was higher than that of AC and MC; for 3-unit FDPs FRC=C>AC=MC; for 4-unit FDPs AC>FRC>C and for inlay-retained FDPs, FRC=AC. An inclination for decreased static fracture strength could be observed with the simulation of PDL but due to insufficient data this could not be generalized for all materials used for FDPs.

Field test on Ultimate bearing capacity of Composite Pile made up of Jet-mixing Cement and PHC Pile with Core Concrete

Composite pile made up of jet-mixing cement and PHC pile with core concrete (CPCP) is a new kind of pile. It is formed by inserting PHC core promptly into the cement soil mixing pile. According to the single pile static load test and PHC pile cement soil bond strength test, differences between CPCP and pipe pile in bearing capacity and coordination deformation mechanism are studied. The results show that presence of peripheral cement soil has greatly improved the bearing capacity of CPCP. Three different loading modes have no obvious effect on CPCP bearing capacity, but the more significant effects on settlement. When the cement soil and soil interface destroyed, pile and cement soil interface friction resistance is much smaller than the bond strength, indicating that the bond strength can ensure coordination between the pile and cement soil. On this basis, the design formula for calculating the bearing capacity of CPCP pile is proposed. Comparing calculated values with field measured values, it has been found that the results are less error and the formula has a certain reliability in the calculation of vertical ultimate bearing capacity of CPCP pile, providing a certain reference for the design and calculation of this type of piles.

Analysis of fatigue life of hybrid fibre reinforced self-compacting concrete

This paper presents the results of an investigation conducted to analyse the flexural fatigue life of self-compacting concrete with different proportions of steel fibre (SF) and polypropylene fibre (PPF) reinforcement. An experimental programme was planned to obtain the fatigue lives of approximately 250 beam specimens under four-point flexural loading. Approximately 90 static flexural strength tests were also conducted to facilitate fatigue testing. The proportions of SF and PPF varied in volume but the total volume was kept at 1%. The two-parameter Weibull distribution was used to describe the probability distributions of fatigue life data at different stress levels. The gradual replacement of SF with PPF in the mixes was found to reduce the variability in the distribution of fatigue life significantly. The maximum increase of 62% in the shape parameter for the fatigue life of a mix with 100% PPF as with a mix containing 100% SF was observed at a stress level of 0·85.

Relationships among static strength, dynamic strength, and psychophysically determined levels of acceptable force for a pushing task and foot pedal actuation task

Static strength or psychophysical tests are commonly used to define the capabilities of a working population, but these data are not easily translated to the peak forces that users apply to products or the operational forces associated with product ease of use. This study investigated the relationships among static strength, peak forces from rapid exertions, and psychophysically determined levels of acceptable forces for 39 subjects depressing a foot pedal and pushing against a vertical surface. Peak forces were greater than static strength and psychophysically determined acceptable forces were less than static strength. The ratio of peak to static strength was greater for the pushing task than for the foot pedal task, likely because of the types of motor units recruited and the inertial effects of each exertion. Relevance to industryEngineers should be mindful when using published strength values to generate requirements for product design. The ratios among static strength, peak force, and psychophysical limits appear to vary based on task and could affect product safety, effectiveness, and ease of use.

Development of the Main Wing Structure of a High Altitude Long Endurance UAV

To enhance the flight endurance of a HALE UAV, the main wing of the UAV should have a high aspect ratio and low structural weight. Since a main wing constructed with the thin walled and slender components needed for low structural weight can suffer catastrophic failure during flight, it is important to develop a light-weight airframe without sacrificing structural integrity. In this paper, the design of the main wing of the HALE UAV was conducted using spars which were composed of a carbon–epoxy cylindrical tube and bulkheads to achieve both the weight reduction and structural integrity. The spars were sized using numerical analysis considering non-linear deformation under bending moment. Static strength testing of the wing was conducted under the most critical load condition. Then, the experimental results obtained for the wing were compared to the analytical result from the non-linear finite-element analysis. It was found that the developed main wing reduced its structural weight without any failure under the ultimate load condition of the static strength testing.

고고도 장기체공 무인기 고세장비 초경량 주익 정적구조시험

고고도 장기체공 무인기의 세장비가 큰 초경량 주익은 작용하중이 작고 변형이 큰 특징이 있다. 때문에, 기존의 유압작동기를 이용한 구조시험 기법을 적용하기 어렵고 새로운 개념의 적용이 필요하다. 본 논문에서는 고고도 장기체공 무인기 고세장비 초경량 주익의 정적구조시험에 대해 간략히 기술한다. 작용하중이 작으므로 작동기를 사용하지 않고 추를 이용하여 하중을 부가한다. 시험체의 상면이 아래로 향하도록 크레인에 설치하고, 지상에서 각 단계별 시험하중에 해당하는 추를 시험체에 장착한 후 크레인을 이용해 시험체를 상승시켜 하중을 부가하는 방식을 채택하였다. 주익의 주요부위에 변형률 게이지를 장착하고 변위를 측정하기 위해 변위 게이지를 장착하였다. 설계제한하중 하에서 주 하중부재의 좌굴 및 파손이 발생하지 않았으며, 설계극한하중 하에서 주 하중부재의 파손이 발생하지 않았다.

Mass and heat-insulation properties of the bodies of passenger and insulated railway cars made of vacuum honeycomb panels

The goal of the study is to suggest an algorithm for optimizing honeycomb vacuum panels geometry to be used for the bodies of railroad passenger cars and insulated railroad cars, which would ensure the desired car strength, its minimum mass and improved heat-insulation properties. For the calculation of panel strength and heat transfer characteristics, the method of finite elements in the SolidWorks Simulation environment was used. An optimization criterion was suggested for the honeycomb structure of panels, which made it possible to select the panel geometry ensuring a minimal body mass for a passenger or refrigerated railroad car and the best thermal resistance for its enclosure. Static load strength tests of the models of passenger/insulated railroad car bodies made of solid plates identified the minimum permissible panel plate thickness for different parts of the car body. Comparative trials and examinations of solid plates and honeycomb panels revealed the optimum honeycomb panel structure variants for different parts of the car body based on the optimization criterion minimum. Having replaced solid plates in car body models with profile-optimized honeycomb panels, we defined the mass and thermal resistance of the cars. For a passenger car, the mass of the body amounted to 11.14 t, the average thermal resistance was 3.187 m2K/W; for an insulated car, the mass of the body was 20.42 t and the average thermal resistance 6.211 m2K/W.